Energy - Research in Jülich (2/2010) by Forschungszentrum Jülich

The Magazine from Forschungszentrum J端lich

RESEARCH in J端lich

ENERGY :: SUPERMATERIAL FOR SOLAR CELLS :: MEMBRANES AGAINST GLOBAL WARMING :: SAVING ENERGY IN GREENHOUSES

02|2010

RESEARCH in Jülich The Magazine from Forschungszentrum Jülich

A sample of glass sealant for high-temperature fuel cells is melted with an invisible laser beam. Cover illustration: Solidified droplets of glass used to produce a sealant for solid oxide fuel cells (SOFCs).

Research in Jülich 2 | 2010

Towards a Sustainable Energy Supply

n order to achieve the goal of a sustainable energy supply, we must rethink our current attitude and reach out across borders. Even though the Inter national Energy Agency (IEA) does confirm that there has been some initial positive development with respect to energy generation, it also says that global energy consumption and carbon dioxide (CO2) emis sions continue to be on the rise. Innovative research is the basis for sustainable change in the generation and utilization of energy. Forschungszentrum Jülich occupies a key position in this process and has made energy research one of the three priority areas in its portfolio. Attention is focused on finding concrete applications for an en ergy supply that is not only environmentally friendly, but also reliable and affordable. At the same time, we are analysing the mechanisms and mainsprings of global warming and are developing energy- efficient large-scale equipment, such as the leading European supercomputer QPACE. An interdisciplinary dialogue on the key issues of energy supply is needed in order to develop new solutions and approaches beyond existing structures. In the future, our activities in this field will therefore be integrated under one roof: the Institute of Energy and Climate Research (IEK). At this new institute, researchers of the former Institute of Energy Research (IEF) and those involved in atmosphere research at the former Institute of Chemistry and Dynamics of the Geosphere (ICG-1 and ICG-2) – a total of 600 employees – work together with the joint goal of arriving at the optimum solution for the future. However, no institution will be able to solve the energy problem on its own. It is therefore necessary

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to establish cross-border cooperations and tread a common path in energy research. We have been maintaining a well-established research partnership with Oak Ridge National Laboratory, the leading research centre in the USA, for decades. A unique cooperation model we launched in 2007 is the Jülich Aachen Research Alliance (JARA) with RWTH Aachen University located in our close vicinity. In the JARAENERGY section, we jointly conduct research into topics such as decentralized energy supply and storage, power plant technologies and issues of nuclear waste management. In doing so, we do not limit ourselves to one tech nology. Our researchers are working on various solu tions for addressing the energy problem. In this maga zine, we would like to show how innovative materials can make conventional power plant technologies more environmentally friendly and renewable ener gies more economically efficient, and how these ma terials may become the linchpin in the implementa tion of future technologies such as nuclear fusion. We will also show how novel ideas help save energy in greenhouses, how fuel cells can be used in trucks and how researchers develop concepts for storing waste from nuclear facilities. We hope that it makes for interesting reading!

Prof. Dr. Achim Bachem Chairman of the Board of Directors

Prof. Dr. Harald Bolt Member of the Board of Directors

10 10 :: SUPERMATERIAL FOR SOLAR CELLS Jülich solar cells with a new, highly transparent window layer demonstrate in special tests that they make very effective use of the entire spectrum of the sun’s natural radiation.

MembraneS AGAINST global wArmIng Jülich scientists are developing membranes that separate the greenhouse gas carbon dioxide from the flue gases of coal power plants and thus help protect the climate.

SAVING ENERGY IN GREENHOUSES Tomatoes, peppers and other plants grow better if greenhouses are covered with a new glass–foil combination which allows a particularly large amount of natural light to pass through. It also saves a lot of energy in plant cultivation.

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IN This ISsue

3 Editorial

:: SnapSHOTS from Jülich 6 Research at a Glance A kaleidoscope of pictures shows highlights of Jülich research – from the dawn of a new era in computing and the development of a detector for hazardous liquids to a new method for treating tinnitus.

:: focus 9 Focus on Materials 10 Supermaterial for Solar Cells New materials make photovoltaics – a technology that is both climate-friendly and environmentally compatible – more efficient and less costly. 13 On the Way Towards an International Fusion Reactor All around the world, Jülich researchers are called upon as experts when it comes to the material and design of the inner walls of fusion devices. 16 Membranes Against Global Warming Coal power plants are to become more climate-friendly in the future with the help of membranes for the separation of gases. 18 Heat Protection for Turbines New ceramic thermal barrier coatings for turbines improve the efficiency of power plants.

:: Highlights 22 The Energy Mix of the Future Interview with Dr. Thom Mason, Director of Oak Ridge National Laboratory, USA 24 Using Diesel More Efficiently Fuel cell systems may soon generate the electricity required for heating and air conditioning in trucks in an environmentally friendly way. 27 Simulation for Fusion A supercomputer located at Jülich will transfer the knowl edge acquired in existing fusion experiments to future larger facilities. 28 Driving Without Gasoline Know-how from fuel cell research helps develop highperformance batteries for electric cars. 30 Research for One-Million-Year Safety Jülich scientists are looking into possible consequences of spent fuel elements coming into contact with water. 32 Saving Energy in Greenhouses Glass–foil combination instead of single-pane glass helps horticulturists reduce energy consumption in greenhouses. 34 News from Energy and Environmental Research Information on the “Energy Technologies 2050” study, the most energy-efficient supercomputer in the world and high-altitude flights for the climate.

20 Beautiful and Mysterious Pictures from Jülich research

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DAWN OF A NEW AREA IN COMPUTING In the next ten years the computing power of supercomputers is to increase by a factor of 1,000 to one exaflop/s, that is to say one quintillion arithmetic operations per second. In this context, Forschungszentrum Jülich and IBM have launched an “Exascale Innovation Center”. Intel and ParTec have also signed an agree ment with Forschungszentrum Jülich for a joint “ExaCluster Lab oratory”. Kirk Skaugen, Vice-President of the Inter Data Center Group said, “Jülich plays a leading role in pursuing research in the area of supercomputing in Europe.”

ENERGY-EFFICIENT COMPUTER CHIPS Scientists of the Jülich Aachen Research Alliance (JARA) have realized a new switching concept for a special chip. This concept paves the way for the generation after next of high-performance computers with low energy requirements. In the memristor chips used, the resistance can be programmed and subsequent ly remains stored. With their new switching concept, the re searchers have solved a fundamental problem of these compo nents: their storage space was extremely limited so far because a superimposition of information between adjacent units during operation, referred to as crosstalk, could not be avoided.

Research at a Glance This magazine focuses on energy and environmental research at Jülich. However, this is not the only area in which Jülich scientists have scored great successes.

LINK TIP www.fz-juelich.de/portal/kurznachrichten

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SNAPshots FROM JÜLICH

HELP WITH TINNITUS The T30CR neurostimulator has been approved by the EU for the treatment of chronic tinnitus. The small device developed by Adaptive Neuromodulation GmbH (ANM) is based on the results of research conducted at Forschungszentrum Jülich. The neuro stimulator combats the disturbing ringing noises in the ear – a condition estimated to affect about three million Germans – using controlled acoustic stimuli. These stimuli disrupt the undesirable synchronization of neural networks in the brain, which is responsible for the non-stop ringing in the ear.

SHAMPOOS AND SHEARING FORCES Everyday products like shampoos and plastics are a mixture of complex ingredients such as polymers and other long-chain molecules. If the pressure is too high or if the mixture is stirred too violently during production then the liquids frequently separate out again. The shearing forces at the container walls are of great significance here. Scientists from Jülich and Lyon have now been able to demonstrate experimentally for the first time how an invisible slip process leads to liquids that are more stable. Their findings can help to more accurately predict the flow behaviour of complex liquids in the future.

DETECTORS FOR HAZARDOUS LIQUIDS Jülich physicists have presented the prototype of a new detector that reliably and rapidly distinguishes for example between liq uid explosives and harmless substances. In the future, it could be used as a monitoring device at airports, and thus render the widespread ban on liquids and gels in hand luggage – including soft drinks, numerous cosmetics and medications – unneces sary. The researchers are in contact with industrial companies, whose job it will be to develop the prototype into a marketable product.

EXCELLENT YOUNG SCIENTISTS The research of Dr. Sebastian Feste and Dr. Dörte Gocke could hardly be more different: he is concerned with the fabrication and analysis of silicon components for nanoelectronics, while she conducts research into enzymes used for example for the production of starting materials for pharmaceuticals. However, the two young scientists at Jülich do have one thing in common: their ideas have provided decisive stimuli for their respective areas of research. For this achievement, they were awarded the 2010 Excellence Prize of Forschungszentrum Jülich endowed with € 5,000 each.

SIMULATED ELEMENTARY MAGNETS Magnetic atoms behave just like tiny compass needles, apart from the fact that their magnetization can only point in two directions, either to the top or to the bottom. With the help of the supercomputer JUGENE, Jülich scientists have now simulated the behaviour of indi vidual cobalt atoms on a platinum surface and have determined how elementary bar magnets influence each other’s orientation. Detailed knowledge of this magnetic coupling can help develop atomic data stor age technology. The result of the simulation was confirmed in experimental measurements carried out by researchers at the University of Hamburg.

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Schwerpunkt

:: FOCUS ON MATERIALS Robust new materials are the foundation of all progress in energy technologies. Research at Jülich provides some concrete examples of this: photovoltaic modules with microcrystalline silicon carbide as a window layer are particularly efficient when it comes to converting sunlight into electric current; hope is pinned on tungsten for the continuous operation of fusion reactors in the future; ceramics help conventional gas- and coal-fired power plants release less climatedamaging carbon dioxide. The search for a solution to mankind’s energy problem has a number of exciting aspects.

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Supermaterial for Solar Cells Jülich researchers are developing new materials for solar cells which are expected to make this climate-friendly and environmentally compatible energy technology less costly and more efficient.

LEDs in different colours cast light on the black surface of a solar cell. This set-up is designed to help find out which parts of the spectrum of sunlight are utilized particularly well by solar cells.

he increasing number of shiny black roofs all over the country shows that photovoltaics are a growth market. The conversion of sunlight into electric current is an inexhaustible source of clean energy as well as an industry that creates jobs. In Germany alone around 57,000 people worked in the pho tovoltaics industry in 2008. However, production costs for solar cells are still relatively high. These shiny power gener ators would become more cost-efficient if they could be successfully constructed from the thinnest possible layers. This saves costly material and reduces the amount of energy required for production.

Thin-film solar cells based on a silicon material in which the atomic components are not arranged in crystal lattices are already being produced. Using cells with a semiconductor material that is more structured could result in higher efficien cies. Crystalline material is better suited for the sun-facing window side of the so lar cell in particular. A team of scientists headed by Dr. Friedhelm Finger is devel oping a material that is particularly prom ising for this purpose. At the Jülich Insti tute of Energy and Climate Research (IEK), solar energy researchers are pro ducing microcrystalline silicon carbide, a material made up of many tiny crystals

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FOCUS

Solar Cells – a Multi-Layered Construction If an electrical conductor is connected to the contacts of a solar cell, electrons flow from the negative pole to the posi tive pole: an electric current is produced, just like in a battery. In order to make this possible, electrons and mobile positive charge carriers – atoms that have emit ted an electron – must initially be pro duced in the solar cell and then separat ed from each other in such a way that they accumulate at the contacts. The en ergy required for these processes comes from the particles of light captured by the solar cell. Solar cells are based on certain mate rials referred to as semiconductors. Semi conductors such as silicon become elec trically conductive when supplied with heat or light. By deliberately introducing impurities – scientists call this process “doping” – the number of mobile charge carriers in the solar cell and therefore the cell’s current yield can be improved. The schematic of a solar cell as cur rently studied at Jülich is shown here: two electrodes or contacts envelop a package made up of three different semi conductor layers. The upper electrode is transparent so that particles of light can penetrate into the semiconductor layers.

that each consist of 50 % silicon atoms and 50 % carbon atoms. TRANSPARENT AND STABLE “It really is a supermaterial,” says Finger. Microcrystalline silicon carbide has many of the advantages that materials scientists involved in solar technology dream of: charge carriers are very mobile in the material, it is extremely stable and moreover, it is transparent. “Crystalline silicon carbide can therefore be used as an ideal window layer for thin-film solar cells,” says Finger. The window layer is the side from which the sunlight hits a solar cell. At the same time, silicon car

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light

glass transparent electrode n-doped microcrystalline silicon carbide i-layer p-doped microcrystalline silicon

reflecting back contact

The lower electrode can reflect particles of light that have overshot the target back into the semiconductor layers (re flecting back contact). All the incident sunlight is therefore utilized in an optimal way. The solar cell is protected by a layer of glass. The semiconductor sandwich in side the solar cell consists of an undoped i-layer in the centre that connects two differently doped layers with each other – the n-doped and p-doped layers. The

researchers introduce impurity atoms that have more electrons than the pure material into the n-doped layer (n for negative) and impurity atoms with fewer electrons than their neighbours into the p-doped layer (p for positive). This layer conducts positive charges. The combina tion of the three semiconductor layers means that electrons and positive charge carriers are systematically separated from each other.

bide also reduces light reflection. The re sult of this “antireflection effect” and the high transparency is that light is utilized particularly well. However, it is not easy to produce the “supermaterial” in the desired quality. Describing the background, Finger says that initial attempts were made as early as the 1980s. However, early experi ments with silane and methane as source materials were unsuccessful because the researchers were unable to find the cor rect ratio of silicon and carbon. Only if the two elements combine with each oth er in a 1:1 ratio will transparent crystals with a high conductivity form. Tempera

tures significantly above 1,000 °C are also required for production. Conventional substrate materials such as glass plates cannot withstand such conditions. In ad dition, high-temperature techniques con sume a lot of energy as well as money and are therefore not suited for the lowcost mass production of solar cells. In the meantime, however, a new method referred to as hot-wire deposi tion has been introduced at Jülich. The source material used for the technique is monomethyl silane, a gaseous compound consisting of one carbon and one silicon atom with three hydrogen atoms bound to each of them. Carbon and silicon are

One of the facilities used by Jülich researchers to produce the thin films for a solar cell.

therefore present in the desired ratio of 1:1 from the very beginning. If this gas is introduced into a chamber with a hot wire made of tungsten or tantalum, hydrogen is split off and the resulting silicon carbide is deposited on a substrate area at 300 °C. In this way, high-quality mi crocrystalline films can be produced that are between 10 and 60 nanometres (millionths of a millimetre) thick. Solar cells with this type of window layer already have an efficiency of 9.6 %. “That is a fantastic value!” says Finger. However, the researchers want to achieve even more. “The films we pro duce with this method do have a high conductivity. However, for reasons we do not quite understand yet, the material primarily conducts free electrons, which means it is an n-type layer,” says Finger. It is possible to produce solar cells from this material – but the light will have to come from the side of the n-type layer. However, for the particularly effective tandem solar cells, like those developed in Jülich, p-type silicon carbide is re quired. The Jülich researchers can manu facture this by incorporating aluminium atoms into the material. This “doping” produces positive charges in the silicon carbide (see box “Solar Cells – a MultiLayered Construction” on p. 11). “For this process, we use trimethylaluminium, which is also used in the production of LEDs, for example,” says Finger. How

ever, “contamination” with aluminium at oms disrupts the crystallization process, the result being a less transparent mate rial. Here, too, Jülich researchers have found a solution: if the pressure in the re action chamber is increased, very trans parent crystalline films will form once again. Finger says, “The technique works in principle, but there are a couple of things that must be optimized before it is ready for practical application.” For ex ample, source gases that are not used up must be prevented from condensing dur ing the manufacturing process. In further developing the production processes, IEK is cooperating with the

Fraunhofer Institute for Surface Engi neering and Thin Films in Braunschweig, Germany, which has broad experience in hot wire deposition. Using numerous methods available at Jülich, from electron microscopy to infrared and Raman spec troscopy, the researchers analyse time and again how silicon carbide changes as a consequence of different interventions. The aim of these studies is to make the supermaterial ready for application soon, so that the market for environmentally friendly solar energy can continue to grow in the future. Wiebke Rögener

Inside this chamber, a hot wire glows while gaseous monomethylsilane is decomposing. This produces films of silicon carbide that are particularly advantageous for solar cells.

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Focus

On the Way Towards an International Fusion Reactor Construction work is in progress in the south of France for the ITER international fusion reactor, which is planned to go into operation in 2019. Whether the project will be a success and thus fuel hopes of having a nearly inexhaustible and clean source of energy largely depends on the material used for its inner wall (“first wall”) and the way it is designed. In this field of research, Jülich scientists have special expertise which they contribute to nuclear fusion experiments all over the world and, in doing so, they extend this know-how.

M This is what the international fusion device ITER in Cadarache in the south of France will look like one day (above). Top: Another virtual glimpse, this time into the vacuum vessel of the Joint European Torus (JET) in Culham, UK.

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odern science banks on interna tional exchange. However, there are only a few disciplines in which global cooperation is as strong as in fusion research. The scientific commu nity, which is scattered all over the globe, has the ambitious joint goal of generating power according to the prin ciple of the sun’s fire (see “Sun’s Fire on Earth”, p. 15) on a commercial scale from around 2050. If they succeed, the raw materials used as fuels would suffice to supply mankind with energy for a period of at least tens of thousands of years.

The Jülich plasma physicists at the In stitute of Energy and Climate Research are among those driven by this vision. One of them is Dr. Sebastijan Brezinsek. He is an expert in what is called plasma– wall interaction, i.e. the ways in which the fusion plasma, which has a tempera ture of more than 100 million °C, and the first wall of a fusion reactor influence each other. However, he is only present at the Jülich fusion experiment TEXTOR, which is jointly operated with partners from Belgium and the Netherlands, for a few months each year. More often than not, he can be found in Culham. This UK

From 2011, the divertor area of the JET fusion device at the lower end of the photomontage will consist entirely of tungsten elements developed at Jülich.

village, some 100 kilometres west of Lon don, is the location of the Joint European Torus, or JET for short – the largest fusion device in the world and so far the most successful. Here, Brezinsek from Jülich is a “deputy task force leader”. He was ap pointed by the EFDA (European Fusion Development Agreement), the organiza tion which operates JET according to an agreement between the European Union and the European fusion research facili ties. While the plasma in the Jülich TEXTOR machine has a volume of seven cubic me tres, JET contains a plasma of 100 cubic metres. “The amount of energy that can be obtained in a fusion device increases with the plasma volume,” says Sebastijan Brezinsek. In order for the device to gen erate more energy than is required to produce the plasma, a minimum size is required, which even JET does not quite have. “However, JET allows us to test the overall concept envisaged for ITER and to develop it further,” says Brezinsek. ITER – which means “the way” in Latin –

is a joint facility of Europe, the USA, Russia, China, India, Japan and South Korea. This “biggest scientific under taking since the international space station”, as the former French President Jacques Chirac called it, is designed to deliver ten times the power it consumes for producing and stabilizing the plasma with a volume of 830 cubic metres, that is, a total output of 500 million watts, for more than eight minutes. CONTROLLED PLASMA Even though the hot plasma is con tained by magnetic fields and thermally insulated, it is actually intended to touch the wall of the vacuum vessel in some places so that helium nuclei can be re moved from the plasma. Similar to a large amount of ash in a fireplace, which will smother a fire, a by-product referred to as “helium ash” can extinguish the plasma. Those parts of the wall that will be in contact with the plasma and must therefore be particularly resistant to heat are called the divertor.

According to its role as the direct predecessor of ITER, JET is currently be ing retrofitted with a wall that, in terms of the materials and properties, corre sponds to the one planned to be used in the decisive operational phase of ITER. “While JET is being retrofitted, we will plan the experiments that will be carried out in the completely upgraded facility with its ITER-like wall from mid-2011 in detail,” says Brezinsek. Ultimately, these experiments aim to clarify whether ITER can one day be operated in such a way that a wall made of the metals tungsten and beryllium can withstand the extremely high stresses over the course of many years. This is because in ITER’s divertor in particular, heat fluxes are to be expect ed that are ten times greater than those present in an aircraft turbine or the fuel rods of a nuclear power plant. “If at all, such heat fluxes can only be found in the boosters of Ariane launch vehicles, but they only need to do their job for a maxi mum of ten minutes until they are sepa rated from the rocket,” says Dr. Jochen Linke, a Jülich specialist in fusion materi als. As a consequence of instabilities in the plasma, heat pulses may even occur in ITER for fractions of a second that have substantially higher power densi ties. In addition, the materials must also be resistant to the neutron radiation that occurs during the fusion process.

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focus

Sun’s Fire on Earth Nuclear fusion is expected to generate the same amount of energy from two litres of water and 250 grams of rock as can be extracted from 1,000 litres of oil. The water contains deuterium, also called “heavy hydrogen”, and lithium rock, from which tritium is produced in the fusion reactor. Tritium is sometimes referred to as “superheavy hydrogen”. Nuclear fusion quite literally fuses the deuterium and tritium nuclei, thus imitat ing a process that also occurs in the sun. However, not only does the centre of the sun have a temperature of around 15 mil lion °C, it also has a pressure that is at least two billion times higher than that of the earth’s atmosphere. Since neither the pressure nor the huge volume of the sun can be imitated in a lab, a tempera

ture of 100 million °C is required in nu clear fusion reactors to compensate for the difference. The fact that materials can withstand the hot fusion plasma at all is due to its extremely low density: the material is affected by the high energy of the impacting plasma particles but is only hit by relatively few of them.

A future fusion reactor will convert en ergy released in the form of heat into electric current by means of turbines and generators, just as in power plants fired by coal, gas or nuclear fuel. In contrast to nuclear fission power, fusion does not produce any high-level active waste that would have to be stored in a controver sial final repository. Radioactive tritium is consumed in the reactor and helium, the final product of nuclear fusion, is not radioactive. In addition, no nuclear chain reaction can occur during nuclear fusion. In the worst case, an accident in the reactor would simply cause the fusion reaction to stop.

MAKING WAY FOR TUNGSTEN For a long time, fusion researchers throughout the world favoured graphite as a material for divertors, because it does not melt even at high temperatures, and because the carbon it is made of causes relatively little damage to the fu sion fire if it finds its way into the plasma as an impurity. However, graphite is less suited for a fusion reactor in continuous operation because it would become en riched with radioactive tritium, which constitutes an inacceptable safety prob lem. Tungsten, in contrast, which is the element with the highest melting point (3,415 °C), has been discussed by fusion researchers for a long time, but was al ways considered to be a poison for the plasma. The reason is that even in the hot plasma, some electrons will remain bound to the tungsten nucleus and cool the plasma by continuously absorbing en

ergy and emitting it in the form of light. “However, in the meantime, we and other scientists have found out in many experi ments how the plasma must be handled, how impurities can be removed and how the thermal load can be distributed more effectively, which is why tungsten has be come the focus of research interest,” says Brezinsek. For example, the team headed by Jochen Linke has examined the structure of tungsten produced in various way under the microscope and carried out numerous load tests, for ex ample using specialized test devices in so-called “hot cells”. In these cells, mate rials that are radioactive after having been bombarded with neutrons can be examined by remote handling. Jülich know-how has in particular contributed to the divertor that will be used in the completely upgraded JET. “That part of

the divertor which must withstand the highest heat fluxes consists of solid tung sten and was co-developed and tested at Forschungszentrum Jülich,” says Brezin sek. He is one of the lucky few who can experience for themselves on site in Culham how this piece of Jülich proves itself in the sun’s fire.

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Frank Frick

The beauty of tungsten: scanning electron micrographs show the metal after it has been exposed to various loads (left). Below: Tungsten lamella for the JET divertor.

Membranes Against Global Warming Coal-fired power plants and climate protection seem to be irreconcilable opposites. Jülich scientists, however, are developing membranes designed to separate the greenhouse gas carbon dioxide from the flue gases of coal power plants. These membranes are intended to make the use of fossil fuels more climate-friendly in the future.

he earth’s atmosphere is heating up to a dangerous degree. The princi pal reason is greenhouse gases re leased by man, in particular carbon diox ide or CO2 for short, which forms during the combustion of coal, oil and natural gas. The International Energy Agency pre dicts that the share of these fossil energy carriers in global energy consumption is even set to increase. The solution seems simple enough: if CO2 was separated from the flue gases of power plants and then permanently stored underground, for example in ex hausted oil fields, coal and natural gas could be used without putting a strain on the climate. There are in fact already coal-fired power plants in which CO2 is scrubbed from the flue gas by means of alkaline solutions. However, the technol ogy is very complex, requires space the size of a football pitch and reduces the efficiency of the power plant by more than ten percentage points.

THE THREE POWER PLANT CONCEPTS Scientists expect lower energy losses if the gas mixtures are separated using membranes. “In principle, there are three options,” says Dr. Wilhelm Meulenberg of the Jülich Institute of Energy and Climate Research (IEK). After combustion, it is possible, for example, to pass the flue gases through a membrane permeable for CO2 which, as it were, sifts out the greenhouse gas. It therefore performs the same job as the alkaline solution does today. Since the CO2 is only re moved after combustion, this method is referred to as post-combustion capture. Pre-combustion capture starts earlier on in the process. Coal is converted with pure oxygen, producing a gas rich in hy drogen and carbon monoxide. The latter reacts with steam to produce carbon diox ide, forming even more hydrogen. Mem branes separate the CO2 from the hydro gen so that, finally, the gas turbine can be supplied with almost pure hydrogen.

The third alternative is the oxy-fuel technology. This involves a membrane that separates oxygen out of the air. It is then “diluted” with CO2 to avoid combus tion temperatures rising too much. The coal is burnt with this gas mixture, the end product being highly concentrated carbon dioxide.

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focus

A scientist at Forschungszentrum Jülich measures how permeable a ceramic membrane is to oxygen (left). Far left: The apparatus she uses in close-up.

“Only the post-combustion method is already widely used today,” says Meulen berg. This method of CO2 capture pro vides the opportunity of retrofitting exist ing power plants. Meulenberg says, “The other two methods offer greater CO2 savings potentials and efficiency losses can be kept at a lower level. However, these methods raise even more issues.” The Helmholtz Alliance MEM-BRAIN, coordinated by Prof. Detlev Stöver of For schungszentrum Jülich, aims at address ing these issues as quickly as possible. MEM-BRAIN also includes other research institutions, universities in Germany and abroad as well as industrial companies. The development of climate-friendly coal power plants also plays an important role within the Jülich Aachen Research Alliance JARA. In addition to the technical properties of the membranes, their entire life cycle must be analysed. This involves ques tions concerning the disposal of compo nents and the costs incurred including the transport and storage of carbon diox ide. Systems Analysis and Technology Evaluation (STE) at Jülich also explores possible reactions of the public to these power plants with incorporated mem branes. The first step is, however, the produc tion of suitable materials. Polymers – highly specialized plastics, so to speak – can be used for CO2 separation at temperatures of up to 200 °C. The sepa ration of hydrogen or oxygen, however,

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requires temperatures of 400 to 900 °C. Ceramic membranes such as those pri marily developed at the Jülich Institute of Energy and Climate Research can be used for these purposes. HIGH-PERFORMANCE CERAMICS An interesting membrane material the Jülich researchers are working on is called BSCF. It belongs to a group of minerals named perovskites after the Russian mineralogist Lev Alekseevich Perovski (1792–1856). BSCF is particu larly suited for the separation of oxygen from air. The MEM-BRAIN Alliance, for ex ample, showcased a demonstrator with a BSCF membrane area of 0.2 m² at the Hanover Trade Fair. It has so far been able to produce around 300 kilograms of pure oxygen in 1 600 operating hours at a temperature of 800 to 850 °C and an oxygen flow of 2.5 litres per minute. The equipment for testing such new materials is not available off the shelf. “We build test stands in which the mem

branes can be fixed and then be tested under controlled conditions,” says engi neer Dr. Michael Butzek of the Jülich Cen tral Technology Division (ZAT). How does a membrane behave at several hundred degrees Celsius? How does the gas flow change at different pressures? How quickly does the material age? “We must continuously adapt the apparatus to the changing tasks,” says Butzek. Material development, practical appli cability, constraints with respect to gov ernment policy and the energy economy – there are numerous factors that have an impact on whether techniques for car bon dioxide separation succeed or fail. “Nobody can say today which route will eventually be taken,” says Meulenberg. “We are working on finding the best pos sible basis for taking a decision.” Wiebke Rögener

This type of membrane separates oxygen out of the air at several hundred degrees Celsius. The specimen on the right is still unfinished. The porous substrates gives the membrane mechanical stability.

Heat Protection for Turbines Ceramics are used wherever it gets really hot inside a power plant turbine. Still, even the best of these materials cannot withstand temperatures above 1,200 °C for a very long time. Jülich researchers intend to change this in order to help turbines in power plants release less greenhouse gas and utilize the fuel more efficiently.

he higher the temperature at which a power plant turbine is operated, the more electricity it generates from each cubic metre of natural gas. Thin thermal barrier coatings made of ceramics protect the metal turbine blades from the damaging effects of the hot fuel gas. “Partially yttria-stabilized zirconia, or simply YSZ, as we call it, is currently the material of choice for this kind of applica tion. This ceramics is very tough and withstands stresses exceptionally well,” says Prof. Robert Vaßen of the Jülich In stitute of Energy and Climate Research. For him, there is currently no material in sight which could completely replace

YSZ, even though this material has its disadvantages, too. For example, the porous interior structure of the ceramics undergoes a phase transition at tempera tures above 1,200 °C which reduces their porosity – experts call this process “sintering”. As a consequence, the mate rial loses its elasticity and starts to chip off. The team headed by Vaßen is working on improving the successful YSZ thermal barrier coatings even further and on making them more resistant to heat. The researchers’ strategy is to increase the share of fine pores in the layer, because air pores reflect heat radiation and increase insulation. The more pores, the better the thermal barrier. Porosity can be increased during the manufactur ing process, in which ceramic powder is injected into the 3,000 °C flame of a plasma burner, where it is melted and accelerated. A computer-controlled robot arm moves the plasma burner along the surface of the blade and thus applies the ceramic thermal barrier coating.

Prof. Robert Vaßen (bottom) with the powders he and his team use to produce thermal barrier coatings for turbines. Next page left: A mixture of ceramic powder and water or ethanol is injected into the torch of the plasma burner and accelerated. The result (centre) is a thin protective ceramic layer on the workpiece. Right: The heat resistance of new ceramics is tested on a test stand.

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The scientists are experimenting with the powder’s particle size in order to pro duce a more porous ceramic material. The finer the powder, the finer the pores – that is the theory. In practice, however, the powder must not be too finely ground. Otherwise, it may cake and will not flow evenly into the plasma flame. Vaßen and his colleagues have found a way out of the dilemma: they mix very finely ground ceramic powder, which is not free-flowing on its own, with water or ethanol. This suspension is fed to a plas ma burner through a newly developed at omizing valve. This results in many tiny pores in a very stable ceramic layer. “The thermal barrier coatings fabricated in this manner have an excellent dispersive ca pacity. Up to 95 % of the thermal radia tion is reflected back,” says Vaßen. In order to make YSZ ceramics even more resistant to mechanical loads, the scientists have transferred the produc tion process into a vacuum. Under such conditions, there is no counterpressure for the hot gases of the plasma burner, which causes them to expand to an ex treme extent. “If the particles are intro duced into the expanded plasma, they do not only melt, they vaporize. In this way, we obtain a rod-like structure that con forms to extreme mechanical require ments,” says Vaßen. MAKE OR BREAK However, this is not enough for the re searchers. Their goal is to achieve oper

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ating temperatures for the gas turbines of 1,450 °C. The development of com pletely new thermal barrier coatings from entirely novel ceramics is therefore one of the key research areas at the Institute of Energy and Climate Research. Once these ceramics have been produced, they will be applied to the YSZ like pro tective armour. Prof. Tilman Beck tests whether the double layers developed by Vaßen and his colleagues deliver what they promise. At the Microstructure and Properties of Materials laboratories, which are also part of the Institute of En ergy and Climate Research, he has two test stands at his disposal that are unique in the world. “What makes these furnaces so special is that we can simu late rapid and extreme temperature fluc tuations, which are also relevant in prac tical applications, by activating each of the heat-producing halogen lamps indi vidually,” says Beck about the advantages of the system. A hydraulic system grips the samples from the top and the bottom and exposes them to cyclic compressive and tensile loads. Ceramics in power plant turbines are exposed to centrifugal loads that correspond to several thou sands of kilograms per square centi metre. After all, the blades of a power plant turbine rotate at 3,000 revolutions per minute. The researchers work like detectives in order to exactly understand how cracks and ruptures form. Using acoustic emission analysis, they can already hear

during the experiment whether a crack is propagating. An infrared camera is used afterwards. Following a flashlight im pulse, it is used to observe how heat transmission subsides in the samples. Parts of layers that have separated from their metal base material can be detect ed with this method even if the diameter is no more than half a millimetre. “We can therefore exactly locate the position of the defect,” says Beck. This is exactly where he and his colleagues will then try and find the physical and chemical causes of the defect with an electron mi croscope. One the one hand, this precise fault analysis initially benefits the team head ed by Vaßen in further improving the pro duction processes for the ceramics. On the other hand, the results are also ap plied in model calculations that can be used to obtain robust estimates on the stability of new coating systems relatively quickly. Such estimates are also of inter est for industry. New thermal barrier systems that pass all the tests ultimately benefit energy companies and their customers as well as the climate. If a 240 MW gas turbine power plant can generate 2 % more electricity from the same amount of natural gas, it will produce this electricity more cheaply and release 24,000 less tonnes of carbon dioxide each year. Brigitte Stahl-Busse

Beautiful and Mysterious If you hear the word “energy technology”, you will probably think of wind turbines, high-voltage pylons and power plant chimneys. These pictures from Jülich energy re search show that technology also has other facets - aesthetic and mysterious ones.

1 Solidified droplets of glass used to produce a sealant for solid oxide fuel cells (SOFCs).

2 A look through a solar cell to the end of an optical wave guide. It is part of a new measuring system for determining how sensi tive a solar cell is to the various spectral regions of sunlight.

3 A drop of glass taken out of the induction furnace at Jülich’s Central Technology Division, which has a temperature of 1,500 °C.

4 Samples of materials for solid oxide fuel cells joined by means of a laser beam. They are tested for characteristics such as tight ness and strength.

5 The wall of an electron beam welding chamber at the Jülich Central Technology Division. When in operation, it is used to permanently join extremely heat-resistant materials for energy technology.

6 A sample is melted with an invisible electron beam. Research in Jülich 2 | 2010

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7 Part of an experimental set-up for determining the uniformity of light of a solar simulator. It produces light with a spectrum that is as close as possible to that of natural sunlight, which is im portant for testing solar cells.

8 A glimpse through a sight glass into a device for manufacturing solar cell layers. Inside, gaseous molecules are broken up with

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the help of a plasma (purple). The resulting substances precipitate on a substrate.

9 This scanning electron micrograph shows the pool of molten highgrade steel that forms if the material is heated to its melting point within milliseconds. This would happen if the steel came into contact with the plasma in a fusion device.

Interview with Thom Mason

The Energy Mix of the Future Energy is the basis for the high standard of living in the industrialized countries. Dwindling fossil resources, global warming and environmental disasters such as the oil spill in the Gulf of Mexico show that we cannot continue as before. Dr. Thom Mason, the Director of Oak Ridge National Laboratory in the USA, comments on the short-term and long-term options for quenching the world’s thirst for energy.

Dr. Thom Mason

Question: What is work in the area of energy research focused on at Oak Ridge? Mason: One focus of our work is on sci ence and technology that make a clean energy future possible. We cover funda mental research on the one hand as well as application-oriented topics such as re newables, grid and power plant technolo gies and end use of energy on the other hand. The key to making substantial progress, however, is connecting basic science and applications, because even if we could accelerate the implementation of novel energy technologies, this would not suffice to reach the targets in terms of carbon dioxide emissions and energy

security in the near future. What is re quired are some very fundamental break throughs – and that is why we need the scientific community to engage. Question: What are the effects in this respect of a cooperation between two institutions such as Oak Ridge National Laboratory and Forschungszentrum Jülich? Mason: The problems are very very diffi cult and no one is going to solve them by themselves. It ultimately comes down to the scientists exchanging information, finding common interests and turning them into breakthroughs – for example, cost-effective carbon dioxide separation

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HIGHLIGHTS Protons from a high-energy accelerator hit a heavy-metal target in the SNS neutron source – an important research facility within the Oak Ridge National Laboratory.

or that, together, we can bring solar en ergy to a point where it is very easy to integrate it in every single building. Question: You just alluded to an important joint project: ceramic filters that will make zero-carbon conventional gas or coal power plants possible. Does that not leave us with the problem of where and how to store carbon dioxide? Mason: Yes. Even if we figure out a costeffective way of separating carbon diox ide, for example using membranes, we must still find an answer to the question of suitable reservoirs. We really have to gain a better understanding of the bio geochemistry. There is no point in storing the CO2 underground if it escapes after ten or twenty years. Considerable work remains to be done to find the right geological formation. We need to solve this question in parallel with the task of CO2 separation. Question: What do you think of calls for investing all funding in renewable energy sources only? Mason: I don’t think much of them – only an energy mix will take us a step forward. Take the example of Denmark, which already generates 20 % of its electrical power from wind energy. However, if the wind force decreases by just a metre per second, the loss of energy is equivalent to the capacity of an entire coal-fired power plant. Now that may be manage able if it is just 20 %, but the whole thing becomes very challenging beyond that level. I believe that smart grids will mean improvements, but that does not change the fact that we need to ensure base load capacity. In my opinion, we have two op tions for this – at least until fusion power is available: conventional coal power plants and nuclear power. The oil spill in the Gulf of Mexico has reminded people that obviously all energy sources have risks. Whether you dam a river, drill for oil

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Oak Ridge National Laboratory (ORNL) Oak Ridge National Laboratory (ORNL) with its more than 4,600 employees and Forschungszentrum Jülich have been cooperating for many years. The partners agreed upon an exchange of scientists as early as 1969. Close ties have existed between the two institutions ever since, for example in energy and materials research. These ties, which have grown in the course of decades, were cemented with binding contracts in 2008 and 2010.

offshore or cover large areas of land with wind turbines – every kind of energy sup ply has an impact on the environment. You always have to trade off these conse quences against the benefits, which in clude the contribution to our industrial competitiveness or to preserving our standard of living. Question: In addition to solar and wind energy, many people also pin their hopes on the use of fuel cells. Do you share these hopes? Mason: Cars will almost certainly be electrified in future. It is not yet clear though, in my opinion, whether those cars will be driven by batteries or fuel cells. Both technologies still have to over come some hurdles – particularly in terms of costs and energy efficiency. Since the question of which technology will win the race is still entirely open, you have to explore both of them equally.

Question: Fusion research is a prime example of large-scale international cooperation. Nevertheless, the general public is under the impression that progress is slow. Do we need fusion at all? Mason: Fusion is the only potential ener gy form that will not pose problems in terms of fuel supply – it is something we need to work on as an option for future generations. One way or the other, we are going to exhaust carbon resources. Even with fission, we are dependent on the uranium resources available, even if the fissile material is recycled. Fusion will not solve our current problems, but we need it if we want our planet to remain inhabitable even for 10 billion people. I believe the investments will eventually pay off. Brigitte Stahl-Busse

Using Diesel more Efficiently Jülich researchers have improved diesel-powered fuel cell systems to such an extent that their application in trucks is now within reach. Auxiliary power units in trucks could produce the power required by heating and air conditioning systems in a more efficient and environmentally friendly manner than combustion engines.

mong US truck drivers, it quite common to leave the engine run ning during a break, above all to ensure that the heating or air condition ing system is supplied with power. How ever, when a vehicle is idled, the engine generates little usable energy per litre of diesel and produces a lot of fumes that harm the climate. “The market is hungry for a diesel-powered auxiliary power unit for trucks that has an energy yield of more than just five or ten per cent,” says

Jülich scientist Dr. Robert SteinbergerWilckens. Solid oxide fuel cells (SOFCs) are just one of several types of fuel cells studied at the Jülich Institute of Energy and Climate Research, and are particu larly suited as auxiliary power units. Compared to most low-temperature fuel cells, which run exclusively on pure hydrogen, SOFCs have the advantage that they can also use methane and carbon monoxide as a fuel or else as a “fuel gas”. An upstream reformer unit can convert the diesel fuel that drives the truck into these three fuel gases. SOON READY FOR THE MARKET Steinberger-Wilckens, who coordi nates Jülich’s activities with respect to SOFCs, estimates that this type of fuel cell will be ready for the market within less than four years. “By then, we must be able to make sure that the cells sur

vive the numerous switching processes between the on and the off state during their lifetime without any damage.” The high operating temperature of more than 700 °C is difficult to handle. It is neces sary to make the ceramic material of the electrolyte permeable to oxygen ions (see figure on p. 25). The high tempera ture itself is not the actual problem – SOFCs are already very reliable in con tinuous operation – but the change in temperature when the cell is switched on or off. Changes in temperature cause the metal and the ceramic materials in the cell to contract or expand to a different extent. The sealing material, which ensures that air and fuel gases do not mix, is under particular stress. “The problem would be solved quickly if we could use a metal gasket,” says Mihaly Pap, an engineer at the Jülich Central Technology Division.

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HIGHLIGHTS

Efficient Converters of Chemical Energy

electric consumer

fuel

air

H2 O2-

H2O unused air components

water unused fuel anode

“However, our sealing material must fulfil requirements that metal cannot – for ex ample, it must be electrically insulating.” In many years of work, Pap’s working group has succeeded in developing glass seals that can at least withstand the cooldown of SOFCs to a stand-by tem

electrolyte

cathode

perature of approximately 350 °C. This would be quite acceptable for a truck that is driven every day. If the SOFCs are switched off in the evening, the tempera ture could be maintained at this level until the next morning. “Scientists all over the world are still having a tough time finding the ideal gasket that is not damaged by repeated complete cooldown,” says Pap. This problem makes being able to repair a defective seal all the more important. So far, an expensive stack of several fuel cells connected in series has had to be discarded even if the gasket was only untight in one single place. How to reach untight places inside the stack without breaking the stack apart? The solution: “Similar to doctors, who focus radiation on a tumour in radiotherapy, without damaging the irradiated healthy tissue, we focus a laser beam on the defective spot,” says Pap.

Production of the thin electrolyte layer of a fuel cell by means of dip coating. A substrate is first immersed in a liquid, called the “sol”, and then removed at a constant rate.

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This is how a fuel cell works, in this case the SOFC version powered by hydrogen or hydrocarbons: air is introduced at the positive pole, the cathode. The oxygen molecules (O2) in the air take up elec trons from the cathode material. They move through the electrolyte as negative ly charged ions to the anode, i.e. the negative pole, where they react with the hydrogen (H2) to form water (H2O). The surplus electrons are released in this process and utilized as electric current.

This melts the broken glass sealant material. When the material cools down and solidifies, the defective spot is com pletely sealed again. The amazing thing is that the method is successful even though the laser has to permeate the metal material of the SOFC. Pap’s depart ment has recently filed a patent for this technique, which PhD students helped to develop. ENORMOUS PROGRESS The “survival” of the sealing material would be easier if the operating tempera ture of SOFCs was not quite as high. Dr. Frank Tietz and his colleagues are there fore working on improving the permeabil ity of the electrolyte layer to oxygen ions at lower temperatures. “We have recently found out how to build cells that have about the same performance at 550 °C as cells 15 years ago at 950 °C,” says Tietz. The researchers achieved this enormous progress by reducing the elec trolyte layer’s thickness to one to two thousandths of a millimetre. “We are the only ones in the world who can produce layers this thin for electrolytes with a size of ten by ten square centimetres,” says Tietz. The scientists scored a success by

This fuel cell stack (left) with dimensions of 25 x 35 x 50 cm consists of three modules with ten individual HT-PEFC fuel cells each (bottom, in the foreground).

optimizing the so-called sol-gel technique for their purposes, which is also used, for example, for the antireflection coating of ophtalmic lenses. However, if SOFCs are intended to be operated at 650 °C in the future, the thin electrolyte layer would double the performance of the SOFCs at this temperature. The advantage of such a high operating temperature is that the cells can use methane without the up stream reformer. In order to achieve further improve ments, the researchers are studying how the materials are affected during the operation of the fuel cells on the micro scopic level. For this purpose, they are using the numerous tools for analysis available in their state-of-the-art lab put into operation in November 2008. This does not only facilitate the progress of SOFCs. The researchers are also working on an alternative, the high-temperature polymer electrolyte fuel cell or HT-PEFC for short. “The decisive advantage is that HT-PEFCs only need to heat up for three minutes. In contrast, it takes SOFCs 20 to 30 minutes before they are ready to operate,” says Dr. Bernd Emonts, who coordinates research activities in the field of low-temperature fuel cells at IEK. The “HT” in the name of the HT-PEFC can be attributed to the fact that it is a “hotter” version of the older PEFC that operates at 90 °C. The operating tem perature of HT-PEFCs, in contrast, is about 160 to 180 °C. “Their advantage is

that the hydrogen they consume does not need to be highly purified, which takes us back to diesel or jet fuel,” says Emonts. The more modest requirements with respect to purity enables the hydro gen to be produced from diesel in an upstream reformer. REFORMER IMPROVED WITH HELP OF JUGENE The key factor for the efficiency of such a reformer is that the diesel is mixed well with air and water. To this end, a group of researchers headed by Prof. Ralf Peters has calculated the flows of gases and liquids injected in the mixing chamber of a reformer for a 5 kW HT-PEFC with the Jülich supercomputer JUGENE. In addition, they simulated the

flows with coloured liquids in a glass model of the reformer. In this way, they were able to optimize the shape of the mixing chamber so that initially, 99.9999 % of the diesel could be utilized – and even after 1,000 operating hours, it is still as much as 99.7 %. Due to this success, Peters’ team had so much confidence in the supercomputer’s calculations that they had it design the mixing chamber of a larger reformer for a 50 kW fuel cell on its own, without comparison with real reformer models. Although the large reformer has not yet undergone initial tests, the researchers have no doubt that their “colleague”, the supercomputer, has once again done a first-class job. Axel Tillemans

Computer simulation of the flow velocities in the reformer that produces the hydrogen required by the HT-PEFC fuel cell from diesel. The velocity decreases from red (100 metres per second) to yellow and green and finally blue.

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HIGHLIGHTS

Simulation for Fusion The Jülich Supercomputing Centre operates the first supercomputer exclusively for European fusion research known as HPC-FF. Its computing power of about 100 teraflop/s – 100 trillion arithmetic opera tions per second – is required to transfer the knowl edge gained in today’s fusion experiments to future larger facilities.

hoever designs a fusion device (see “Sun’s Fire on Earth” on p. 15) must address a special problem. A look at the construction of new sports equipment, aircraft or bridges shows that these objects of very differ ent sizes are all tested in wind tunnels, for example for air drag or stability. These wind tunnels therefore have very differ ent sizes as well, although inside them, the wind often flows around models that have been built true to scale instead of real test objects. The engineers can then scale up the test results. “Unlike wind tunnel experiments, this is not possible for the important interface between the plasma and the first wall of a fusion device,” says Prof. Detlev Reiter of the Jülich Institute of Energy and Climate Research. He continues, “What we know about the physical processes at the edge of the plasma today can only be extra polated to future larger fusion devices or even a fusion power plant with the aid of computer simulations.” In fact, there are very many and very different physical processes close to the first wall of a fusion device that play a role and interact in extremely complicat ed relationships. The calculations there

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2D simulation (left) and 3D simulation (above) of the plasma temperatures close to the first wall of a fusion device (top). Temperatures decrease from red to green to light blue. fore require a great deal of time and ef fort. “Only with the current generation of supercomputers and in particular with the HPC-FF is it possible to include all three dimensions of a fusion device in the simulation,” says Reiter, who heads the Computer Simulation for Fusion team at Jülich. Before this only the cross sec tion of the device was used for the simu lation, assuming that it was representa tive of the entire reactor – which can be compared to the assumption that a slice of bologna sausage will always look the same irrespective of where you cut it. However, the simulations on the HPC-FF

including the third dimension have re vealed that in areas for which experimen tal data is difficult to obtain, the behav iour of the plasma edge is not as symmetrical as previously expected. Since this may also have conse quences for the contact between plasma and wall in the international experimental reactor ITER, which will be put into opera tion in 2019, the Jülich team was put in charge of the relevant calculations – thus beating the field in an international com petition. Frank Frick

Driving Without Gasoline The chemical and technological know-how Jülich scientists have acquired in fuel cell research helps them develop powerful batteries for electric cars. The researchers are also studying whether these vehicles could be used as a temporary storage for surplus electricity in the grid. Furthermore, they are already considering possible consequences of new drive concepts for the atmosphere.

e ffectively remove many substances from the air enveloping the earth, includ ing methane, the climate-forcing effect of which is twenty times as strong as that of carbon dioxide.

Electric cars are easy on the environment if they use electricity generated from renewable sources. They may also serve as a temporary storage for surplus electricity.

n order to reduce our dependence on oil and curb carbon dioxide emissions, which are harmful to the climate, the German Federal Government is funding the development of alternative fuel und drive concepts for vehicles. It would, however, be fatal to fight fire with fire by releasing other substances that provide additional fuel for the greenhouse effect into the atmosphere instead of CO2. Dr. Cornelia Richter of the Jülich Institute of Energy and Climate Research (IEK) is

therefore studying the effects of hydro gen as a fuel for vehicles in fuel cells. A small share of the hydrogen will inevita bly be lost and find its way into the atmosphere without being utilized, for example during the storage process. Hydrogen does not play an active part in the earth’s radiation budget. “However, it competes with methane for hydroxyl radicals,” says Richter. These substances are also referred to as the “detergent of the atmosphere” because they very

ALL-CLEAR FOR HYDROGEN “A hydroxyl radical which has already reacted with water is no longer available for a reaction with methane,” says Rich ter. More hydrogen therefore means that less methane is removed from the atmo sphere. The physicist and meteorologist has now calculated what would be the consequences if the EU switched over to a hydrogen economy. For the first time, she also took into consideration the changes in concentrations of other air borne pollutants, some of which cause an increase in hydroxyl radicals. The re sults showed that on the global scale, the concentration of the atmospheric deter gent would fall by about one per cent. On the other hand, the use of hydrogen as an energy carrier would also mean that carbon dioxide would be saved if the hydrogen was generated by means of

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HIGHLIGHTS

In order to stop global warming, the share of carbon dioxide and methane in the atmosphere needs to be kept as low as possible.

r enewable energies, for example. “On the whole, the positive impact on the climate outweighs the negative effects,” says Richter. NEXT-GENERATION BATTERIES However, hydrogen is not the only form in which renewable energy can be stored for driving cars – electrical energy in batteries is another option. Forschungs zentrum Jülich has therefore established the Kompetenzverbund Nord (Excellence Alliance Nord – KVN) together with four universities and a Max Planck institute. The KVN is planning to support the Na tional Electromobility Development Plan that was recently decided by the German Federal Government. The scientists in the collaboration are looking far ahead and have their sights set on the batteries of the next generation, and the genera tion after next. “For state-of-the-art lithi um ion batteries to power a vehicle for 1,000 kilometres, a battery weighing 1 tonne would be required – there is sub stantial room for improvement,” says Dr. Hans Peter Buchkremer of Forschungs

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zentrum Jülich, the coordinator of the alliance. The scientists at IEK will, above all, contribute the experience they have gathered during the development of fuel cells – after all, fuel cells and batteries are based on similar electrochemical prin ciples and are technologically related. A key role will be played by new materials, which are expected to make batteries more powerful, lighter and cheaper. There is also another important de mand on the batteries. “They should be able to tolerate irregular loading and un loading cycles,” says the Jülich scientist Jochen Linßen, who coordinates the project NET-ELAN at IEK funded by the Federal Ministry of Economics and Tech nology (BMWi). It is all about the promis ing idea of integrating electric cars into the grid in such a way that their batteries can be used as a temporary storage for surplus electricity. In concrete terms, the concept could look like this: the owners of electromobiles sign a contract with their electricity supplier. Whenever they are not using the car, they plug it into an electric socket. The electricity supplier

continually decides whether he takes electricity out of the car battery or recharges it, depending on supply and demand. The task of NET-ELAN is to identify potential problems associated with an appropriate integration of electric vehi cles into the grid and to show how these issues can be resolved. For example, car owners, electricity providers, vehicle manufacturers and the State represent different interests with respect to electro mobility. “These interests must be co ordinated in order to encourage the development of electromobility,” says Linßen. “In addition, we need intelligent grids to make such a concept a reality, grids that facilitate automated control of the charging and discharging processes.” The additional electricity requirement of one million electric cars will not be a problem for German power suppliers – it would be less than one per cent of the present electricity production in the country. Axel Tillemans

Research for One-Million-Year Safety Final repositories for high-level active waste are a matter of much controversy. Many people are worried that an ingress of water may cause dangerous reactions and that, as a consequence, radioactive material could contaminate the environment. Jülich scientists are looking into the possible consequences of spent fuel elements coming into contact with water and are also developing ceramic materials suitable for the long-term storage of radioactive elements.

With the aid of scanning electron microscopy and numerous other methods, Jülich scientists are analysing the corrosion products that arise when spent nuclear fuel comes into contact with water.

here are currently 17 nuclear power plants in Germany that generate electric power. Every year they pro duce a total of 370 tonnes of spent fuel. The Federal Office for Radiation Protec tion (BfS) estimates that even when nu clear energy is phased out in Germany, there will still be 10,000 tonnes of highlevel active waste that will have to be stored permanently one day. Approxi mately 95 % of a spent fuel element con sists of uranium dioxide. The remainder is made up of fission products and ele ments whose atomic nuclei have been produced by the capture of neutrons. It will take a million years for the radiation of these elements referred to as acti nides to have more or less completely decayed. This is therefore the time hori

zon during which a final repository should isolate the radioactive waste from the en vironment. “It is a very demanding task to make a reliable forecast on safety issues regard ing such a long period of time,” says Prof. Dirk Bosbach. However, the head of Ra dioactive Waste Disposal at the Jülich In stitute of Energy and Climate Research (IEK) is convinced that, in principle, such a task can be accomplished. “As soon as we have understood the behaviour of ra dioactive waste under the conditions in a final repository down to the level of the molecules, we can base our safety analy sis on physical and chemical laws that will apply as much in hundreds of thou sands of years as they do today.” CONTACT WITH WATER All current concepts envisage storing radioactive waste several hundreds of metres deep in rock formations that are as impermeable to water as possible. Bosbach and his team investigate how spent nuclear fuel behaves if it comes into contact with water despite precau tionary measures taken to prevent this from happening. The researchers build on a special strategy for their analysis: initially, they try to determine which solids form as a consequence of contact with water and what states they occur in – experts refer to these states of matter as phases. At the same time, the scien tists analyse which substances dissolve

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HIGHLIGHTS

“Hot cells” at Forschungszentrum Jülich: in these facilities, experiments with highlevel active waste can be carried out without putting the scientists’ health at risk.

and can be detected in the water. Due to the high radioactivity, these corrosion ex periments including the required analy ses and measurements must be carried out in so-called “hot cells”, shielded ex perimental facilities in which highly ac tive substances are handled by remote operation. However, a large number of experi ments that are necessary cannot be per formed under these conditions. This is why in the next step, the researchers go to a lab, where they produce the identi fied phases or corrosion products indi vidually in minute quantities, so that they are only slightly radioactive, if at all. They then determine data based on the natural laws of thermodynamics that provide reli able information on the stability of sub stances. In a third step, they investigate how actinides dissolved in water are taken up by the corrosion products – this process is referred to as sorption – in various German and European measuring facilities. Here, too, the samples are only slightly radioactive because the research ers work with extremely diluted solu tions. In addition to many detailed findings, their research has already led to an in sight that Dirk Bosbach considers essen tial when it comes to the assessment of the long-term safety of final repositories. “The corrosion products that form if spent fuel elements come into contact with water would initially bind almost all

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the radioactive atomic nuclei released, so that they cannot spread any further,” says the Jülich mineralogist. ALTERNATIVE CONCEPTS Bosbach is a member of JARA, the Jülich Aachen Research Alliance, and has co-developed the master’s degree pro gramme “Nuclear Safety Engineering”, which will be offered by RWTH Aachen University from the end of 2010. How ever, his working group is not only involved in conducting research on the direct final disposal of high-level radio active waste, but also on alternative methods of disposal. It would be conceiv able, for example, that the fuel rods could be reprocessed and that those actinides that are particularly dangerous could be separated. Plutonium, americium, curium and neptunium could then be encased in ceramic materials and stored in this form in a final repository. The advantage, he says, is that “such ceramics are much more stable chemically than spent fuel elements or a glass product: in water that has been in contact with them for many years at moderate temperatures, absolutely no dissolved substances can be found even with the most sensitive detection methods.” However, most ceramics also have a disadvantage: under the influence of par ticles that are released when the acti nides decay, some ceramic materials lose their well-ordered structure; they be

come glass-like and therefore more sus ceptible to outside influences. The Jülich scientists have now produced new zirco nium oxide ceramics. “There is evidence that ceramics with the structure we have produced are particularly tolerant of ra diation damage,” says Bosbach. Only fur ther extensive experiments will show whether the researchers’ hopes are justi fied. If they are, says Bosbach, “the range of options for waste management would be extended considerably”. Frank Frick

A member of staff prepares samples of lowlevel active material in a box with transparent walls, the so-called “glove box”. He can only reach the samples using the gloves.

Saving Energy in Greenhouses Many greenhouses are still covered with off-the-shelf single-pane glass. The glass– foil combinations developed at Jülich would offer several advantages: they allow a particularly great amount of light to pass through and thus promote the growth and quality of tomatoes, peppers and other plants. Above all, however, they help save up to 50 % energy when growing plants.

obert Stefan grows seedlings, in particular, lettuce, cabbage and herbs. “If I do this under normal window glass or under a polyethylene film and then plant the seedlings out doors, they will initially go limp,” he says. “The reason is that they are not used to the natural spectrum of light.” If Robert Stefan grows the plants under self-clean ing foil highly transparent in the entire spectrum of light instead, the plants sur vive the shock of being transplanted out doors without suffering any damage. The plants are toughened up for the outdoors inside the greenhouse, so to speak. The red tinge of lollo rosso lettuce even be comes more intense under this special foil, because in contrast to conventional glass, it is also permeable to around 80 % of the sun’s UVB radiation. As a conse

quence the content of healthy plant pigments called anthocyanins, and also vitamins, flavours and essential oils considerably increases in some plants. Gardening is not a hobby for Robert Stefan. He manages a horticultural enter prise that produces approximately 35 million young plants per year and is re quired to be cost-efficient. “What counts for horticulturists are additional benefits in terms of production – a new glazing material will only have a chance on the market if it provides the plants with more light and if the investment pays back within a period of five years,” says Dr. Silke Hemming, leader of the Greenhouse Technology team at the Dutch research institution Wageningen University and Research Centre. Four years ago she vis ited what is today the Jülich Institute of

Prof. Ulrich Schurr with the special foil that improves plant growth.

Research in Jülich 2 | 2010

HIGHLIGHTS

The slight bulge shows which of the roofs and window areas are covered with foil. The air trapped inside is the decisive factor for the excellent thermal insulation of the greenhouse.

Bio- and Geosciences together with the owner of one of the Netherlands’ largest tomato-growing companies. She was par ticularly interested in the greenhouses that were being developed at the insti tute. They use a novel glass with an antireflection coating that is permeable to UVB radiation on both sides. These panes of glass increase transparency to a maxi mum of 97 % for the region of light the plants need for photosynthesis. The effect is that the plants grow stronger, are more resistant and more productive. In the Netherlands, more than 250,000 square metres of greenhouse area have already been fitted with anti-reflection glass. The Jülich team headed by plant physi ologist Prof. Ulrich Schurr, engineer Ger hard Reisinger and horticultural expert Prof. Andreas Ulbrich tried to figure out how to save additional energy. Even though the new glass does let more light into the greenhouse, the insulation is just as poor as with the single-pane glazing used as a standard in horticulture. For ex ample, a greenhouse in which heat-loving poinsettias are grown consumes up to 80 litres of oil per square metre every year. Glass also has the additional disadvan tage that it gets dirty easily and must be

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cleaned regularly in order to ensure that plants always receive sufficient light. TRANSPARENT AND THERMALLY INSU LATING AT THE SAME TIME This was how the idea for a glass– foil combination was born. The Jülich researchers developed a completely new design. A highly transparent, stable and self-cleaning foil is stretched across the antireflection glass and fixed at the edges with a special window profile. “We deliberately chose so-called ETFE foil that has a lifetime of more than 20 years even under unfavourable climatic conditions,” says Gerhard Reisinger, the head engineer in the project. The space between the glass and the foil is inflated with air. The results showed that “with respect to the wave lengths that are important for the plants, the new glass–foil combination lets as much light through as previous green house covering materials with normal, uncoated glass. The permeability for heat, in contrast, is 40 to 50 % below that of conventional single-pane glazing systems,” says Schurr. Even snow will no longer be a problem for horticultural enterprises in the future. The air cushion

can be deflated temporarily to decrease thermal insulation. The snow melts and natural daylight can get through to the plants in the greenhouse again. However, this is not yet the final product. For their most recent project, the researchers are using FEP films from the aviation industry. This type of foil has even better transparency values while being as durable and self-cleaning as the ETFE variety. A greenhouse 56 m long and 26 m wide operated by the Jülich scientists in cooperation with research ers at Bonn was recently constructed at the Horticultural Centre of Excellence (KoGa). There, the next generation of glass–foil combinations will be used: along the entire length of the green house, an FEP film that is two metres wide will be spread continuously instead of providing each individual pane of glass with a film. This is intended to further increase transparency and thermal insu lation. Above all, however, the scientists expect that the production and material costs will be halved in comparison to the first generation of glass–foil combina tions. Brigitte Stahl-Busse

News

all about energy and environmental research

Thrifty Supercomputer

Energy Technologies 2050

In the Green500 list of the world’s most energy-efficient super computers published in July 2010, the German QPACE super computer defended the top position. It was developed as part of a cooperation with the University of Regensburg, Forschungs zentrum Jülich and IBM Research & Development in Böblingen as the main partners. The Green500 list has established itself alongside the Top500 list of the fastest supercomputers as a way of evaluating and rating the performance of computers. The discussion on dwindling raw materials and the scarcity of energy has penetrated the world of supercomputers and is challenging the long-established mantra that “only the speed counts”.

This is the title of a study published by scientists and initiated by the Federal Ministry of Economics in which Jülich energy experts from Systems Analysis and Technology Evaluation played a major role. The paper will contribute to the preparation of the 6th Energy Research Programme. It evaluates numerous energy technologies and analyses the research and develop ment work required for each of them. The Jülich scientists were concerned with the technology fields of fossil-based power generation, carbon capture and storage, fuel cells as well as the transport of district heat.

Jülich Elements for “Wendelstein 7-X” There are in principle two concepts for future fusion power plants: tokamaks, such as the Jülich TEXTOR machine, the JET joint European project or the planned ITER device, and stellarators. The “Wendelstein 7-X” stellarator, to be put into operation in Greifswald in 2014, will help clarify which of

these concepts is more promising. An unusual system of a total of 140 superconducting electrical connectors devel oped, built and tested in Jülich with a budget of € 30 million has already been completed. The final elements were offi cially handed over in Jülich on 30 June 2010.

Research in Jülich 2 | 2010

HIGHLIGHTS

International Exchange of Knowledge

Flying High for the Climate

More than 200 scientists accepted the invitation of the Jülich Aachen Research Alliance (JARA) to join the 1st International JARA-ENERGY Conference, which took place in March 2010. Topics up for discussion were, for example, clean electricity, e-mobility and energy-efficient production. In his opening speech, Dr. Michael Stückradt, then state secretary in the Ministry of Innovation of North Rhine-Westphalia, paid tribute to JARA as “one of the most important innovations in the science land scape” and to the JARA-ENERGY section as “the largest research collaboration in the field of energy in Germany”.

In early 2010, an international team of 50 scientists collected a wealth of new data with the research aircraft Geophysica for predicting the future development of the ozone layer and its in fluence on climate even more precisely than today. The aircraft took off from the northern Swedish city of Kiruna into the strato sphere, up to an altitude of 20 km. The six-week measuring campaign, which was part of the EU project RECONCILE, was coordinated by the Jülich atmospheric researcher Marc von Hobe. His campaign diary can be found on the Internet at http:// www.fz-juelich.de/icg/icg-1/data/reconcile/news.php.

Research Partnership with China Forschungszentrum Jülich has further consolidated its tradition ally good relationships with Chinese scientists and institutions. For example, an agreement was concluded in late 2009 with the solar module manufacturer Baoding TianWei Solarfilms on study ing the long-term stability of thin-film solar cells. Representa tives of Forschungszentrum Jülich and Peking University also signed a memorandum of understanding on intensifying collabo ration in the field of atmospheric research.

PUBLICATION DETAILS Research in Jülich Magazine of Forschungszentrum Jülich, ISSN 1433-7371 Published by: Forschungszentrum Jülich GmbH | 52425 Jülich | Germany Conception and editorial work: Dr. Frank Frick, Dr. Anne Rother (responsible according to German press law), Dr. Barbara Schunk, Erhard Zeiss Authors: Dr. Wiebke Rögener, Dr. Frank Frick, Dr. Axel Tillemans, Brigitte Stahl-Busse Design and Layout: Graphical Media, Forschungszentrum Jülich Translation: Language Services, Forschungszentrum Jülich Photos: Forschungs zentrum Jülich (cover illustration, pp. 2–4, p. 6, p. 7 top left, p. 7 top right, p. 8/9, p. 10 bottom, p. 12, p. 15 bottom, p. 16 top, p. 17, p. 18 bottom, p. 19, p. 20/21, p. 22 bottom, p. 25, p. 26, p. 27 centre, pp. 30–33, p. 34 top left, p. 34 bottom), Fotolia (p. 7 top left, p. 10 top, p. 15 top, p. 18 top, p. 28/29, p. 34 top right), Digital Stock (p. 35 top left), Arndt Lorenz (p. 35 top right), EFDAJet (p. 13, p. 14), ORNL (p. 22 top, p. 23), RWE (p. 16 bottom), SPM Group, University of Hamburg (p. 7 bottom), Mauritius (p. 24), Baoding Tianwei Solarfilms Co., Ltd. (p. 35 bottom), © Copyright 2006 General Atomics. Reprinted with permission. Further duplication without permission is prohibited. All rights reserved. (p. 27 top) Contact: Corporate Communications | Telephone: +49 2461 61-4661 | Fax: +49 2461 61-4666 | Email: info@fz-juelich.de Printed by: Rhein-Ruhr-Druck GmbH & Co. KG Print run: 2,500

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