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About APEC Efficiency With Usability
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Smart Grid
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Harvest Time
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Photovoltaic
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Wind Energy
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A Seismic switch
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Wave Energy
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Contents Page
Vision Leading the Electrical and Mechanical field by graduating Engineers capable of satisfying all market needs.
About Us APEC (Associative Power Engineering Community) is a non-profitable organization established in 2007 in the Faculty of Engineering in Ain-Shams University to help and support all electrical and mechanical Students and prepare them to penetrate life after college confidently. Our target is to satisfy the needs of engineering students disciples through providing them with superior quality services linking the chain between academic science and applied technical knowledge.
Transfer Engineering Students to innovative Engineers able to run the world. Through APEC remarkable and leading contributions in connecting the two Engineering wings: applied technical knowledge and academic study.
Mission
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Efficiency with usability ABB’s all new string inverter for photovoltaic systems
JukkA NuRMI – The worries of global warming and soaring oil and gas prices mean
the utilization of renewable energy sources looks set to increase to meet growing global energy demands. The planet has always received generous amounts of one source of renewable energy, sun rays. The simplest method of harnessing solar energy is through the use of photovoltaic cells. These cells produce direct current (DC) which needs to be converted into alternating current (AC). This conversion is carried out using an inverter, and ABB string inverters are designed for photovoltaic systems installed primarily on residential and small- to medium-sized commercial buildings. The new inverter series now includes built-in protection functions, which reduce the need for costly and space-consuming external protection devices and larger enclosures.
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1 ABB’s PVS300 string inverter
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echnological developments are continuously improving the efficiency and cost effectiveness of photovoltaic systems. For its part, ABB has long been a leader in inverter and power converter technology and it has been using this knowledge and experience to provide leadingedge and high-quality solutions for photovoltaic power systems. Its portfolio of solar inverters ranges from small single-phase string inverters right up to central inverters with power ranges of hundreds of kilowatts. The latest addition to this portfolio, the PVS300 ➔ 1, has a power range from 3.3 to 8 kW, making it suitable for residential buildings as well as small and medium-sized commercial and industrial buildings. Its all-inone design makes it reliable, safe and extremely cost effective, especially in installations using multiple inverters. The heart of the PVS300 string inverter is the intuitive control unit equipped with a user-friendly graphical display that provides three main views: sun meter; solar energy production information; and help/ settings menus. The sun-meter symbol indicates the amount of sun shining (10 rays mean full sunshine, one ray means rain) ➔ 2, and at night the inverter goes into sleep mode, consuming less than 1W. The solar energy production information
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display is designed to provide the necessary data for those interested or involved in the feed-in tariffs 1 provided by many countries for environmentally friendly production such as solar power ➔ 3. The built-in data logger displays and stores the exact daily, weekly, monthly and yearly production for up to 24 years. In addition, the inverter calculates CO2-emission savings. Detailed technical data are available for those who want more than a general overview of their solar energy production. A dedicated “help” key and built-in user’s manual are provided to explain the different views and setting possibilities. The display platform supports up to 24 languages. Start-up, guaranteed in just four straightforward steps, is guided by a start-up assistant that is initiated when the inverter is first powered up. Settings can be easily changed thanks to a menu structure with a look and feel similar to that found in everyday devices, such as mobile phones. The display can be detached from the inverter ➔ 4 and 5 and mounted separately on a wall to monitor inverter performance from outside the installation room. It can also be wirelessly connected to the in-
ABB’s portfolio of solar inverters ranges from small single-phase string inverters right up to central inverters with power ranges of hundreds of kilowatts.
Title Picture ABB’s new string inverter, designed for photovoltaic systems installed on residential and small-to-medium-sized commercial buildings now includes built-in protection functions.
Footnote 1 A feed-in tariff (FiT) is a policy mechanism designed to encourage the adoption of renewable energy sources and to help accelerate the move toward grid parity. Under a feed-in tariff, eligible renewable electricity generators (which can include those in homes and businesses) are paid a premium price for any renewable electricity they produce.
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2 Displays even a child can understand
3 Detailed technical information is available for those who want a bigger picture of their solar energy production
3a Solar-energy- production- information
3b A "help” key explains the different views
verter; the wireless transmitter and receiver are already paired in the factory so that the user does not have to play with the complex settings so often needed in wireless connections. The technology and frequency range is similar to that used in wireless weather sensors but it covers longer distances than Bluetooth and consumes significantly less power than Wi-Fi.
Also solar arrays are subject to atmospheric activity and may be damaged by the overvoltage generated by lightning. To minimize these risks, surge protective devices (SPD) need to be installed on each polarity. The impedance of these devices varies depending on the voltage applied; for example, in normal operation the impedance is extremely high and is only reduced – in the case of over voltage – by discharging the associated current towards ground. Unfortunately,
Built-in protection The attention given to the aesthetics, and the internal design and layout of ABB’s string inverter were important to fully support system integrators and those installing photovoltaic systems. In particular, the addition of comprehensive built-in protection eliminates the need for the external components used in most traditional photovoltaic systems. To begin with, fault currents, created in an ungrounded system when two ground faults or a line-to-line fault exist, may damage modules or cause excessive heating in some part of the system. The systems need to be protected against this admittedly rare occurrence by placing string fuses in both the negative and positive legs of the string cabling.
The PVS300 has a power range from 3.3 to 8 kW, and its all-in-one design makes it reliable and safe especially in installations using multiple inverters.
The addition of comprehensive built-in protection eliminates the need for the external components used in most traditional photovoltaic systems. standard SPDs do not work properly in photovoltaic systems. Instead specially designed ones are needed for PV systems having high nominal DC voltage
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The neutral point clamped (NPC) topology combined with ABB’s patentpending modulation scheme provides an efficient inverter with minimal leakage current and the maximum allowed DC voltage.
4 The PVS300 string inverter is suitable for residential and commercial use
5 PVS300 display can be detached for remote monitoring
6 Integrated DC switch, string fuses and surge protection devices under the main cover
and low short-circuit current capability. Typically, these protection devices are placed in a separate junction box between the solar modules and the inverter.
ternal design of the inverter significantly reduces troubleshooting and repair time when a problem occurs. For example, an in-built microprocessor monitors internal protection devices (eg, fuses and surge protective devices) and immediately transmits error messages or information to the inverter display and optionally over the Internet as an e-mail in the event of a problem; and components such as pluggable surge-arrester cartridges can be easily and safely replaced. Finally, the reduction in material usage is a major contributor to minimizing CO2 emissions over the product lifecycle.
The built-in protection designed into ABB’s PVS300 string inverter avoids the time and cost required to select, design and install external protection devices and enclosures ➔ 6. For system integrators and during installation, a compact integrated solution means space is used much more efficiently, something that is valued especially in installations that use multiple inverters. For end users, the in-
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7 PVS300 string inverter full bridge neutral point clamped (NPC) topology
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LCL Filter
8 Photovoltaic system with stray capacitance Grid PWM control unit
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L1 PV C PVg
Pure performance at the core The core of ABB’s string inverter design is described as a full bridge, neutral point clamped (NPC) topology ➔ 7, which is combined with ABB’s patent-pending modulation scheme to provide an inverter that is extremely efficient with minimal leakage current and high maximum allowed DC voltage. High efficiency comes from simplicity, which is illustrated when certain aspects of a traditional solar inverter design are compared to the PVS300 design. For example, the traditional design uses an additional boost converter in the input or a step-up transformer in the output whereas the ABB string inverter only uses one DC to AC power conversion stage. The elimination of additional power conversion stages not only improves the efficiency but also the reliability of the system. Additional efficiency gains are achieved using intelligent sleep logic and advanced materials, such as amorphous alloy cores in the output LCL filter. A typical ungrounded photovoltaic system is shown in ➔ 8. Solar modules are always connected to ground through a parasitic capacitance (CPVg). Any AC component present in the voltage UN will generate a current through this capacitance to ground. If the voltage across the capacitor contains excessively high-frequency components, it can produce equally excessive high-frequency ground currents that can either create electromagnetic compatibility issues, or degrade or damage the solar modules over time. ABB’s patent-pending high-fre-
quency elimination modulation scheme eliminates the high-frequency components from U N that some inverters in the market actually introduce. The solar-system DC voltage varies depending on the system configuration, temperature and solar irradiation. Due to its wide DC-input range, the ABB string inverter easily accommodates a broad selection of series and parallel configurations and different solar module types. Its high maximum DC voltage allows more modules to be connected in series and this in turn reduces the cost and losses in the DC cabling.
+ U DC + UN -
Inverter
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U AB -
L2
+ EMI filter
Ug
∼
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The maximum DC voltage allows more modules to be connected in series. This not only reduces the losses in the DC cabling but the cost as well.
The PVS300 string inverter was introduced to the market for the first time at the 2010 Intersolar fair in Munich, the world’s largest exhibition for the solar industry. It follows the successful launch of ABB’s central inverter product family for photovoltaic power plants a year earlier.
Jukka Nurmi ABB Solar Inverters Helsinki, Finland jukka.nurmi@fi.abb.com
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smart grid is a digitally enabled electrical grid that gathers, distributes, and acts on information about the behavior of all participants (suppliers and consumers) in order to improve the efficiency, importance, reliability, economics, and sustainability of electricity services.
A brief The term smart grid has been in use since at least 2005, when the article (Toward a Smart Grid) , authored by S. Massoud Amin and Bruce F. Wollenberg appeared in the September/October issue of IEEE P&E Magazine (Vol. 3, No.5, pgs. 34–41). The term had been used previously and may date as far back as 1998. There are a great many smart grid definitions, some functional, some technological, and some benefits-oriented. A common element to most definitions is the application of digital processing and communications to the power grid, making data flow and information management central to the smart grid. Various capabilities result from the deeply integrated use of digital technology with power grids, and integration of the new grid information flows into utility processes and systems is one of the key issues in the design of smart grids. Electric utilities now find themselves making three classes of transformations :
Improvement of infrastructure, called the strong grid in China, addition of the digital layer, which is the essence of the smart grid; and business process transformation, necessary to capitalize on the investments in smart technology. Much of the modernization work that has been going on in electric grid modernization, especially substation and distribution automation, is now included in the general concept of the smart grid, but additional capabilities are evolving as well.
Smart
Grid
Goals of the smart grid : Smart energy demand describes the energy user component of the smart grid. It goes beyond and means much more than even energy efficiency and demand response combined. Smart energy demand is what delivers the majority of smart meter and smart grid benefits. Smart energy demand is a broad concept. It includes any energy-user actions to : enhancement of reliability. reduce peak demand. - shift usage to off-peak hours. - lower total energy consumption. - actively manage electric vehicle charging. - actively manage other usage to respond to solar, wind, and other renewable resources. - buy more efficient appliances and equipment over time based on a better understanding of how energy is used by each appliance or item of equipment. All of these actions minimize adverse impacts on electricity grids and maximize utility and, as a result, consumer savings.
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Smart Energy Demand Mechanisms And Tactics Include : smart meters. dynamic pricing. smart thermostats and smart appliances. automated control of equipment. real-time and next day energy information feedback to electricity users. usage by appliance data. scheduling and control of loads such as electric vehicle chargers, home area networks (HANs), and others.
First city with Smart
Grids:
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he earliest, and still largest, example of a smart grid is the Italian system installed by Enel S.p.A. of Italy. Completed in 2005, the Telegestore project was highly unusual in the utility world because the company designed and manufactured their own meters, acted as their own system integrator, and developed their own system software. The Telegestore project is widely regarded as the first commercial scale use of smart grid technology to the home, and delivers annual savings of 500 million euro at a project cost of 2.1 billion euro.
Demand Response and the Smart Grid:
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emand response programs provide a simple way for facility managers to get paid for reducing consumption and relieving load on the power grid when it is stressed. In effect they are returning capacity to the grid and being paid for that asset.
The modern demand response market began with a pilot program at ISO (Independent System Operator) New England in 2000. ISO New England is responsible for managing the power grid for 7 Northeastern US states. In other countries, these entities are often referred to as TSOs, Transmission System Operators. Since that pilot program in 2000, robust markets have developed at several ISOs and pilot projects are underway at other ISOs and utilities. Demandresponse is an electricity market mechanism by which consumers reduces consumption in response to energy price fluctuations, demand charges, or a
direct request to reduce demand when the power grid reaches critical levels. With demand response, facility managers have the ability to manage their electricity consumption as an asset instead of an expense that must be paid every month. Currently, there is a challenge to electric commodity suppliers in being able to supply the required amount of electricity at any given time. For example, in the summertime, there are many places that get extremely hot, prompting consumers to increase their electricity use for cooling devices. This increase creates a spike in the need for electricity. The electricity company has to be able to provide enough electricity for these spikes and must build the necessary infrastructure to do so. Essentially this means that even though the electric commodity supplier will only need to supply this increased amount of electricity for a relatively short period of time, the equipment needed to do it is present year round. The suppliers, therefore, incur the expense of owning and maintaining this equipment. The cost of this is passed onto consumers and increases their monthly charges. SmartGrids
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Demand response programs provide an alternative. When a spike period is detected, participants in the program receive a curtailment request which generally comes from the Independent System Operator (also known as Transmission System Operator). The request will be based on a previously agreed contract and will specify how much load has to be reduced and for how long. The format of the curtailment request varies : it may be an email, a phone call a pager message or an automatic signal direct to the building management system. The participants evaluate the request and decide whether to accept it. Some programs include only voluntary requests, where the participant has the option to accept or refuse any curtailment. Other programs include mandatory requests, where the participant is obliged by contract to comply.
be built for less than $400/kW. This translates into lower charges for customers. In addition, given that the demand response solution is, at its core, power reduction instead of power generation; it is a zero emission generator, the cleanest power possible. As we have seen, the idea behind demand response is for customers to get paid to manage their energy. By reducing consumption and relieving load on the power grid when it is stressed, participants return capacity to the grid. In effect each curtailment is an asset that has a financial value. Program participants can expect to earn back 5-25% of their annual energy costs. The earnings vary based on speed, location, and willingness to participate.
Why the smart grid is beneficial
The participants turn off nonessential loads, and bring down the height of the spike to a level that the electricity company can provide. Finally the participants communicate back to the ISO to confirm a successful curtailment. In this way the electricity company avoids the investment required for peaking power plant. The most common type of equipment used for peak power is a natural gas combustion turbine. These are powerful generators that can start up on a moment’s notice. However, they tend to cost about $800/kW to build, whereas a similarly robust demand response solution can
In order to understand why the smart grid is beneficial, we need to understand how it works. The energy market or local electric utility closely follows the market conditions and then based on that information; they will dispatch a virtual green generator. The virtual green generator is triggered to start when a signal is sent to the control boxes inside buildings participating in the smart grid program. The Building Automation System and Electrical Distribution systems in the participating buildings have pre-designed routines they will follow in the event that they receive one of these signals. Following these routines will work to reduce electrical demands.
SmartGrids
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Demand Response is the primary driver for the Smart Grid. The Smart Grid has been set up to self-optimize as well as restore itself automatically. The grid could be utilized in a number of ways including for Demand Side Management/Real Time Pricing (RTP). Another benefit of the Smart Grid is that it has the ability to provide some information to the utility companies including real time data.
The Smart Grid is all about presenting the information to the right people at the right time. In terms of demand response, this means letting consumers know the price for power relative to their consumption in real time. This gives the information that has previously been kept private and that most have not seen before. This information allows them to decide if they should continue to consume or not. In general, most automatic metering business cases will say that simply providing this information will make about 60% of their case. The other 40% of their value proposition comes from transmission and distribution management Finally, some of the impacts that can be seen from Smart Grid implementation are potentially reduced overall costs, more energy efficiency and better alignment with green initiatives, higher reliability, and the opportunity to have more information regarding your electrical service.
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MicroGrids Micro grids are envisioned as local power networks that use distributed energy resources and manage local energy supply and demand. Although they would typically operate connected with a national bulk power transmission and distribution system, they would have the ability to pull themselves off the grid and function in island mode when necessary to increase reliability for the local load.
Dis
Advantages:
Advantages: Area served : from one house up to 10 square kilometers AC or DC, Low voltage or high voltage architectures may be used. Lower cost than the existing service. Full time Micro grid - always operates independently of the bulk supply.
Integrated communications : Some communications are up to date, but are not uniform because they have been developed in an incremental fashion and not fully integrated. In most cases, data is being collected via modem rather than direct network connection. Areas for improvement include substation automation, demand response, distribution automation, supervisory control and data acquisition
It has to supply all of the demand without the benefits of a diverse load profile.
Technology : The bulk of smart grid technologies are already used in other applications such as manufacturing and telecommunications and are being adapted for use in grid operations. In general, smart grid technology can be grouped into five key areas : (SCADA), energy management systems, wireless mesh networks and other technologies, powerline carrier communications, and fiber-optics. Integrated communications will allow for real-time control, information and data exchange to optimize system reliability, asset utilization, and security.
Sensing and measurement :
meter reading equipment, widearea monitoring systems, dynamic line rating (typically based on online readings by Distributed temperature sensing combined with Real time thermal rating (RTTR) systems), electromagnetic signature measurement/analysis, time-of-use and real-time pricing tools, advanced switches and cables, backscatter radio technology, and Digital protective relays.
Core duties are evaluating congestion and grid stability, monitoring equipment health, energy theft prevention, and control strategies support. Technologies include: advanced microprocessor meters (smart meter) and SmartGrids
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Harvest time Harvesting energy to create truly autonomous devices for industrial processes PHILIPP NENNINGER, MARCO ULRICH – In an effort to further
reduce downtime and maximize reliability, operators need to know more about the health of a plant’s assets. This information is mostly supplied by sensors. Additional sensors mean extra wiring to power them and hence increased installation costs. Eliminating these wires would not only reduce costs but also the complexity of the entire process. Because the power consumption of many industrial sensors is quite modest, the use of batteries would
seem like a suitable solution. However, exchanging batteries at regular intervals may very well offset the savings of having wireless sensors in the first place. Another solution is known as energy harvesting. Energy harvesting is the process by which energy (ambient, motion, wind, light), derived from external sources, is captured and stored to supply power for low-energy electronics. Ambient energy is available in abundance in the process industry and it is here that energy harvesting is beginning to make its mark.
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1 Battery life over measurement interval of an idealized temperature transmitter
Battery life (a)
Battery shelf life
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10 0
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Measurement interval (s)
installation can amount to almost 90 percent of the total cost of the device, it makes financial and technological sense to explore the possibility of using wireless devices.
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ireless technology has had a significant impact on society over the past 15 years or so, and technological developments in the meantime mean it is gradually being accepted in the process industry, especially for asset monitoring. Process automation plants usually have an operating lifetime of about 20 years, and to maximize return on investment during this time, plant utilization should be as high as possible. Since a plant can only be operational if all the necessary assets are functioning correctly, high component reliability is a must. This can be achieved through asset monitoring, an option to detect possible defects in equipment before they occur and to allow the root cause to be eliminated in a scheduled manner. In order to do this, additional sensor information is required. This information can come either from sensors already installed and capable of providing the required measurements, such as ABB’s differential pressure transmitters used for plugged impulse line (PIL) detection or from additional sensors positioned in other locations of the process. If additional sensors are required, installation costs should be kept as low as possible in order to maximize the benefit of having them. But since wiring and
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Wireless technology Wireless solutions are by no means a new concept in the process industry; In fact they first came to prominence in the 1960s. However, these solutions have been applied mainly in specialized products for certain markets such as ABB’s AquaMaster, an electronic commercial water-flow meter, and flow totalizers in the oil and gas industry. ABB’s Totalflow, a remote measurement and automation system, is one such example. As is the case with fieldbus technology, any wireless protocol that aims at achieving critical mass requires a global standard, which is supported by all device manufacturers. One such standard does exist and is called WirelessHART. WirelessHART is the first international wireless standard which was developed specifically for the requirements of process field device networks.
dundant channels between two nodes in the network by relaying messages over different routes. This in turn increases the fault tolerance of the communication and allows a well-designed network to become tolerant of both communication link and routing device failures. In addition, the spatial redundancy of mesh networking ensures reliable communication, even in industrial, scientific and medical (ISM) bands. Of course the relaying of messages (as a consequence of mesh networking) together with the requirement of constant security impacts the power budget, which has to be offset by achieving low-power optimization. Low-power optimization There are some major differences between wired and wireless devices when it comes to low-power optimization, and ABB’s “wired” industrial temperature transmitter, the TTH300, will be used to illustrate this point. The TTH300 device is powered by the 4–20 mA current
Because wiring and installation can amount to almost 90 percent of the total cost of a device, it makes sense to explore the possibility of using wireless devices.
Network reliability is one of the main focus points in process automation An aspect of wireless networks that has influenced reliability is the area of meshed networking. Mesh networks provide spatially re-
loop and measures, for example, the resistance of a 4-wire Pt100 (and thus the temperature at the sensor tip) at very short time intervals, which, depend-
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2 Energy harvesting allows the conversion of energy created by industrial processes into electrical energy
3 A fully autonomous temperature transmitter
Solar radiation
Vibration
Flow Heat
ing on the sensor type and configuration, could be every 100 ms. Because the 4–20 mA loop continuously provides up to 40 mW of power, the device is limited by the power it can draw, while the energy consumed by the device is irrelevant. A wireless sensor on the other hand does not have to measure temperature several times per second because most industrial wireless networks for the process industry do not usefully support such short update intervals. Between measurements the transmitter only has to fulfill its network duty of relaying messages for other nodes. The rest of the time the electronics can be in a so-called low-power mode during which no computations or measurements take place and only a fraction of the power is consumed. In low-power mode, the power consumption of the device can be approximated by considering the power consumed in active and low-power mode and the duty cycle of the device. For the wireless device described above the duty cycle roughly correlates to the time needed for the sensor to update. If the self discharge of the battery is not considered, a rough estimate for the battery life of a battery-powered transmitter can be given. This estimate for an ideal device is shown in ➔ 1. Energy harvesting Exchanging batteries on a regular basis is not always an option since this could – depending on the plant setup – offset the savings of using wireless devices. Instead, energy harvesting (EH) is seen
as a possible solution that overcomes this issue to create truly autonomous devices. EH converts the energy available in the process ➔ 2 into usable electrical energy, which in turn is used to power wireless devices. Typical energy sources include hot and cold processes, solar radiation, and vibration and kinetic energy from flowing media or moving parts. The most prominent mechanisms are solar radiation, thermoelectric and kinetic converters. Solar radiation
Although photovoltaics is nowadays a robust and established technology, its application indoors is rather limited. While the outdoor intensity can reach approximately 1,000 W/m 2, typical indoor values lie in the region of 1 W/m 2 [1]. In other words, the amount of energy that can be harvested is restricted.
Energy harvesting converts the energy available in an industrial process into usable electrical energy.
Thermoelectric
Thermoelectric generators (TEG) harvest electrical energy from thermal energy (ie, the temperature gradients between hot or cold processes and the ambient) using the Seebeck effect 1 [2]. While the efficiency of TEGs is rather low – typically below 1 percent – the technology is quite robust and stable. Often large temperature reservoirs are present especially in the process industry. Hence a lot of heat is available and the power that can be delivered by commercially available TEGs is sufficient to maintain a variety of wireless sensor nodes in different scenarios.
Footnote 1 Discovered by Thomas Johann Seebeck in 1821, the Seebeck effect is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two substances.
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4 With a footprint of only 8 mm2 the micro-TEG allows for high output voltages.
5 Numerical thermal simulations
Source: Micropelt GmbH
Process temperature distribution of 80°C (red) An ambient temperature of 25°C (blue)
Kinetic converters
The direct conversion of mechanical movement, such as vibrations, into electrical energy can be achieved with different transducer mechanisms: − Electromagnetic mechanisms use a flexible mounted coil, which moves inside the static magnetic field of a small permanent magnet. This induces a voltage as described by Faraday’s law. − Piezoelectric transducers are based on piezoelectric materials. By means of a proof mass supported by a suspension, kinetic movement results in a displacement of this mass, which induces a mechanical stress on the piezoelectric material. − Electrostatic transducers are based on a charged variable capacitor. When mechanical forces are applied, work is done against the attraction of the oppositely charged capacitor plates. As a result, a change in capacity induces a current flow in a closed circuit. In short, all kinetic converter principles are based on a mechanical resonator, and the systems can only deliver a reasonable power output if the resonance frequency of the harvesting device matches the external excitation frequency. The use of variable-frequency drives in the process actually limits the application of vibration harvesting systems. System components and architecture
Energy harvesting can be a discontinuous process: For example, in the case of outdoor photovoltaic applications, daynight cycles will lead to unstable power
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sources; plant downtimes can lead to different process temperatures, which may influence the energy delivered by TEGs; and variable-frequency drives can lead to varying power yields of vibration harvesters. In contrast there may be times when the energy harvesting system supplies more energy than is actually needed. The power consumption profile of typical wireless sensor nodes is also discontinuous: Depending on the duty cycle and update rate of the sensor, peak loads may occur which have to be buffered be-
ABB has developed a complete autonomous temperature transmitter using a fully integrated EH system. cause EH systems are not able to support these high short-term currents. Essentially every EH system needs a buffer to overcome times when the harvesting device is unable to supply enough energy for the sensor node. Typical buffers include: – Special super or hybrid-layer capacitors. These capacitors tolerate high peak currents. – Rechargeable secondary cells. – Conventional primary cells. These cannot store an excessive amount of energy coming from the EH system
but they can be used to provide power at times when the system cannot. – Typical industrial primary cells. These cells have a very long shelf life with low self-discharge rates and are a very reliable buffer alternative. Conventional lithium-ion based secondary cells suffer from a limited amount of discharge/charge cycles. Harvesting devices and buffers need an appropriate power management (PM) system for a truly autonomous power supply. The PM has two major functions: – To adjust the characteristics of the output voltage and current of the EH system to the input requirements of the electrical consumer. – To switch smoothly between energy buffers and the different EH sources. ABB’s autonomous temperature transmitter Research in ABB has developed a complete autonomous temperature transmitter ➔ 3 using a fully integrated EH system. Thermoelectric generators have been integrated into the device in a way that the handling, stability and form factor of the transmitter stays the same while its lifetime and functionality are considerably enhanced. The device also includes a smart energy buffer solution for occasions when the process temperature is insufficient to generate enough energy. The overall size of the selected temperature transmitter prevented the integration of conventional TEGs, which normally have macroscopic dimensions around
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Fully autonomous devices will help engineers to better control industrial processes
10 to 20 cm 2. Instead novel micro-thermoelectric generators (micro-TEGs), produced with a wafer-based manufacturing process [4], were used ➔ 4. The major challenge of integrating these two devices was ensuring that the stability and robustness of the transmitter was maintained.
used to allow for faster update rates, for example. Future outlook The EH-powered temperature transmitter solves a central issue of wireless sensor nodes: The regular exchange of primary cells is no longer necessary, and this in turn can help reduce the total cost of ownership. While EH is not possible for all sensors in every circumstance, it is a viable energy supply for a wide range of devices. Fully autonomous devices can help to better understand and control industrial processes and therefore make them more profitable.
Fully autonomous devices can help to better understand and control industrial processes and therefore make them more profitable. In most cases the process is warmer than the ambient air temperature and so the hot side of the TEGs needs to be coupled to the process with the most optimal thermal conductivity. Extensive numerical simulations were carried out to maximize the heat flow through the TEGs ➔ 5. The other (or cold) side must be cooled and is therefore coupled to the ambient air with a heat sink. The heat sink needs to be positioned at a sufficient distance to allow for applications where the process pipe is covered with a thick insulation layer. With a minimum difference of about 30 K between the process and ambient temperatures, the system is able to generate sufficient energy to supply both the measurement and wireless communication electronics. At temperature gradients greater than 30 K, more energy is generated than is needed, which could be
Philipp Nenninger Marco Ulrich ABB Corporate Research Ladenburg, Germany philipp.nenninger@de.abb.com marco.ulrich@de.abb.com
References [1] Müller, M., Wienold, J., Reindl, L. M. (2009). Characterization of indoor photovoltaic devices and light. Conference Record of the IEEE Photovoltaic Specialists Conference: 000738-000743. [2] Vining, C. B. (2001). Semiconductors are cool. Nature, 413 (6856), 577–578. [3] Nenninger, P., Ulrich, M., Kaul, H. (2010). On the energy problem of wireless applications in industrial automation. In proceedings of the IFAC Symposium on Telematics Applications (218–224). [4] Nurnus, J. (2009). Thermoelectric thin-film power generators self-sustaining power supply for smart systems. In proceedings of smart sensors, actuators and MEMS IV: Vol. 7362-05. Dresden.
Title picture Just as grains are harvested to produce food, energy can be harvested to produce power.
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hotovoltaics offer consumers the ability to generate electricity in a clean, quiet and reliable way. It’s the direct conversion of light into electricity at the atomic level. Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electric current results that can be used as electricity. The photoelectric effect was first noted by a french physicist, Alexander Edmond Becquerel, in 1839, who found that certain materials would produce small amounts of electric current when exposed to light. In 1905, Albert Einstein described the nature of light and the photoelectric effect on which PV technology is based, for which he later won a nobel Prize in physics. The first PV module was built by Bell Laboratories in 1954. It was billed as a solar battery and was mostly just a curiosity as it was too expensive to gain widespread use. In the 1960s, the space industry began to make the first serious use of the technology to provide power aboard spacecraft. Through the space programs, the technology advanced, its reliability was established, and the cost began to decline. During the energy crisis in the 1970s, PV technology gained recognition as a source of power for non-space applications.
Photovoltaic
T
his diagram illustrates the operation of a basic PV cell, also called a solar cell. Solar cells are made of the same kinds of semiconductor materials, such as silicon, used in the microelectronics industry. For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current and thus electricity.
A number of solar cells electrically connected to each other and mounted in a support structure or frame is called a PV module. Modules are designed to supply electricity at a certain voltage, such as a common 12 volts system. The current produced is directly dependent on how much light strikes the module.
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PV are best known as a method for generating electric power by using solar cells to convert energy from the sun into a flow of electrons. The photovoltaic effect refers to photons of light exciting electrons into a higher state of energy, allowing them to act as charge carriers for an electric current. The term photovoltaic denotes the unbiased operating mode of a photodiode in which current through the device is entirely due to the transduced light energy. Virtually all photovoltaic devices are some type of photodiode. Solar cells produce direct current electricity from sun light, which can be used to power equipment or to recharge a battery.
PV Moudle
The first practical application of PV was to power orbiting satellites and other spacecraft, but today the majority of photovoltaic modules are used for grid connected power generation. In this case an inverter is required to convert the DC to AC. There is a smaller market for off-grid power for remote dwellings, boats, recreational vehicles, electric cars, roadside emergency telephones, remote sensing, and cathodic protection of pipelines.
P Average solar irradiance, watts per square metre. Note that this is for a horizontal surface, whereas solar panels are normally mounted at an angle and recevie more energy per unit area. the small black dots show the area of solar panels needed to generate all of the worlds energy using 8% efficient photovoltics. Photovoltaic power capacity is measured as maximum power output under standardized test conditions (STC). The actual power output at a particular point in time may be less than or greater than this standardized value, depending on geographical location, time of day, weather conditions, and other factors.
hotovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material. Materials presently used for PV include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium gallium selenide/sulfide. Due to the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years. Cells require protection from the environment and are usually packaged tightly behind a glass sheet . When more power is required than a single cell can deliver, cells are electrically connected together to form photovoltaic modules, or solar panels. A single module is enough to power an emergency telephone, but for a house or a power plant the modules must be arranged in multiples as arrays. A significant market has emerged in off-grid locations for solar power charged storage battery based solutions. These often provide the only electricity available. The first commercial installation of this kind was in 1966 on Ogami Island in Japan to transition Ogami Lighthouse from gas torch to fully selfsufficient electrical power. World solar PV capacity (grid-connected) was 7.6 GW in 2007, 16 GW in 2008, 23 GW in 2009, and 40 GW in 2010.
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Photovoltaic Applications Power
Buildings
stations Many plants are integrated with agriculture and some use innovative tracking systems that follow the suns daily path across the sky to generate more electricity than conventional fixed-mounted systems. There are no fuel costs or emissions during operation of the power stations.
Arrays are most often retrofitted into existing buildings, usually mounted on top of the existing roof structure or on the existing walls. Alternatively, an array can be located separately from the building but connected by cable to supply power for the building. The output of photovoltaic systems for installation in buildings is usually in KW.
Transport PV has traditionally been used for electric power in space. PV is rarely used to provide motive power in transport applications, but is being used increasingly to provide auxiliary power in boats and cars. A selfcontained solar vehicle would have limited power and low utility, but a solar-charged vehicle would allow use of solar power for transportation.
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Solar Power
Advantages :
satellite
D
esign studies of large solar power collection satellites have been conducted for decades. The idea was first proposed by Peter Glaser, then of Arthur D . Little Inc NASA conducted a long series of engineering and economic feasibility studies in the 1970s, and interest has revived in first years of the 21st century. A key issue for such satellites appears to be the launch cost, which so far makes spacebased solar power at least 100 times more expensive than terrestrial solar power .
Hybrid systems
Rural Electrification Where no mains electricity is available, the system is connected to a battery via a charge controller. An inverter can be used to provide AC power, enabling the use of normal electrical appliances.
A solar system can be combined with another source of power a biomass generator a wind turbine or diesel generator - to ensure a consistent supply of electricity. A hybrid system can be grid-connected, stand-alone or grid-support.
It’s fuel free and produces no noise, harmful emissions or polluting gases . PV systems are very safe and highly reliable and can be recycled. It can be aesthetically integrated in buildings (BI PV). It creates thousands of jobs.
Dis Advantages : Some toxic chemicals, like cadmium and arsenic, are used in the PV production process. These environmental impacts are minor and can be easily controlled through recycling and proper disposal. Solar energy is somewhat more expensive to produce than conventional sources of energy due in part to the cost of manufacturing PV devices and in part to the conversion efficiencies of the equipment. As the conversion efficiencies continue to increase and the manufacturing costs continue to come down, PV will become increasingly cost competitive with conventional fuels. Solar power is a variable energy source, with energy production dependent on the sun. Solar facilities may produce no power at all some of the time, which could lead to an energy shortage if too much of a region’s power come from solar power.
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Wind
Energy Wind is a form of solar energy , Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earths surface, and rotation of the earth. Wind flow patterns are modified by the earth’s terrain, bodies of water, and vegetative cover. This wind flow, or motion energy, when harvested by modern wind turbines, can be used to generate electricity. The total amount of economically extractable power available from the wind is considerably more than present human power use from all sources. At the end of 2010, worldwide nameplate capacity of windpowered generators was 197 giga watts (GW).Wind power now has the capacity to generate 430 TWh annually, which is about 2.5% of worldwide electricity usage. Over the past five years the average annual growth in new installations has been 27.6 percent. Wind power market penetration is expected to reach 3.35 percent by 2013 and 8 percent by 2018. Wind power, as an alternative to fossil fuels, is plentiful, renewable, widely distributed, clean, produces no greenhouse gas emissions during operation, and uses little land. In operation, the overall cost per unit of energy produced is similar to the cost for new coal and natural gas installations. The construction of wind farms is not universally welcomed, but any effects on the environment from wind power are generally much less problematic than those of any other power source.
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Wind Turbine A wind turbine is a device that converts kinetic energy from the wind into mechanical energy. If the mechanical energy is used to produce electricity, the device may be called a wind generator or wind charger. If the mechanical energy is used to drive machinery, such as for grinding grain or pumping water, the device is called a windmill or wind pump. Developed for over a millennium, today›s wind turbines are manufactured in a range of vertical and horizontal axis types. The smallest turbines are used for applications such as battery charging or auxiliary power on sailing boats; while large grid-connected arrays of turbines are becoming an increasingly large source of commercial electric power.
Types
Horizontal Axis : Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator.
Modern wind turbines
: Turbines used in wind farms for commercial production of electric power are usually three-bladed and pointed into the wind by computer-controlled motors. These have high tip speeds of over 320 km/h (200 mph), high eff iciency, and low torque ripple, which contribute to good reliability. The blades are usually colored light gray to blend in with the clouds and range in length from 20 to 40 meters (66 to 130 ft) or more. The tubular steel towers range from 60 to 90 meters (200 to 300 ft) tall. The blades rotate at 10 to 22 revolutions per minute. At 22 rotations per minute the tip speed exceeds 90 meters per second (300 ft/s). A gear box is commonly used for stepping up the speed of the generator, although designs may also use direct drive of an annular generator. Some models operate at constant speed, but more energy can be collected by variable-speed turbines which use a solid-state power converter to interface to the transmission system. All turbines are equipped with protec-
tive features to avoid damage at high wind speeds, by feathering the blades into the wind which ceases their rotation, supplemented by brakes.
Vertical Axis design : Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. Key advantages of this arrangement are that the turbine does not need to be pointed into the wind to be effective. This is an advantage on sites where the wind direction is highly variable, for example when integrated into buildings. The key disadvantages include the low rotational speed with the consequential higher torque and hence higher cost of the drive train, the inherently lower power coefficient, the 360 degree rotation of the aerofoil within the wind flow during each cycle and hence the highly dynamic loading on the blade, the pulsating torque generated by
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some rotor designs on the drive train, and the difficulty of modeling the wind flow accurately and hence the challenges of analyzing and designing the rotor prior to fabricating a prototype. With a vertical axis, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, hence improving accessibility for maintenance.
Research :
R
ecent researches into technologies to improve power output from wind turbines include those such as the wind lens or leading edge tubercles on the blade.
A Wind lens is a modification made to a wind turbine to more efficiently capture wind energy. The modification is a ring structure called a shroud or wind lens which surrounds the blades, diverting air away from the exhaust outflow behind the blades. The effect created as a result of the new configuration creates a low pressure zone behind the turbine, causing greater wind to pass through the turbine, and this, in turn, increases blade rotation and energy output. Wind lenses are being researched in Japan where it is claimed that a wind lens may increase wind power output between 2-4 times depending on the turbine scale and shroud de-
sign. Additionally, the shroud acts to dampen noise created at the blade tips. The blade itself can be designed to locally utilize the same concept in fluid dynamics as the wind lens. Blade designs modeled from the humpback whale flippers to include leading edge tubercles have been shown to yield an additional 20% power output.
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A seismic switch Certified switchgear for nuclear power plants is providing a critical link in the chain 24
ABB review 1|11
RENATO PICCARDO, ANNUNzIO REGANTINI, DAVIDE CATTANEO, LUCIANO DI MAIO – A nuclear power plant must be able to manage an enormous
amount of energy in extremely safe conditions. All system functions must be controlled with absolute reliability and guaranteed operation. The equipment used must be able to withstand degradation over time caused by exposure to environmental extremes of temperature, pressure, humidity, radiation and vibration, including earthquakes. ABB has developed the UniGear zS1 medium-voltage certified switchgear with the aim of satisfying all critical requirements.
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1 Example of required response spectrum (RRS)
Acceleration (g)
3
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0 10
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Frequency (Hz)
operating basic earthquake (OBE) or, in case of a very strong earthquake, it must be able to shut down the reactor, known as a safe shutdown earthquake (SSE). An additional requirement is verifying the functionality of each component under very intense environmental conditions in terms of temperature/humidity and after a thermal/radiation aging process.
P
eople working on nuclear projects know that attention to detail and only using equipment that has been certified is crucial: It is never acceptable to turn the key of a nuclear plant until it is certain that every component playing a safety function has been fully tested and certified. Detailed parameters for certification are specified in American IEEE 1 and European IEC 2 standards.
The critical scenario is the possibility of a seismic event: The system must be able to continue functioning during a so-called
According to both IEEE and IEC standards the following methods can be used to qualify system components (alone or in combination): – Type testing: A type test subjects a representative sample of equipment, including interfaces, to a series of tests, simulating the effects of significant aging mechanisms during normal operation. – Operating experience: Performance data from the equipment in question or from equipment of similar design that has successfully operated under known service conditions may be used in qualifying other equipment under equal or less severe conditions. – Analysis: Qualification by analysis requires a logical assessment or a valid mathematical model of the equipment.
Footnotes 1 Institute of Electrical and Electronics Engineers 2 International Electrotechnical Commission
Degradation over time, along with exposure to environmental extremes of temperature, pressure, humidity, radiation
The qualification process Every supplier of products for the safety chain of a nuclear power plant (NPP) must go through a specific qualification process, the purpose of which is to verify and certify complete reliability of system components. Some of the equipment in a NPP may also be required to operate under very intense conditions. This is why the main purpose of a qualification process is to verify the ability to operate during various and well-defined environmental settings.
and vibration, can hasten commoncause failures of qualified equipment. For this reason it is necessary to establish a “qualified life” for equipment with significant aging mechanisms. Qualified life is the period of time before the start of a design basis event for which equipment has demonstrated that it meets the design requirements for the specified service conditions [1]. Climatic qualification (cyclic damp heat)
The purpose of climatic qualification is to prove that the switchgear will continue to perform its safety function before, during and after variation of the humidity and temperature levels in the environment where the equipment will be installed. The test determines the suitability of equipment under conditions of high humidity combined with cyclic temperature changes and production of condensation on the
The system must be able to continue functioning during a so-called operating basic earthquake (OBE) or, in case of a very strong earthquake, it must be able to shut down the reactor surface of the equipment being tested. In medium-voltage (MV) switchgear, condensation produced during humidity-temperature cycles can cause a reduction in the isolating properties.
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A seismic switch
maintain it in a safe shutdown condition, are designed to remain functional.
2 The climatic testing cycle of the Doel NPP qualification cycle 6 100
EMC qualification
Ur% max
95 90 85
The equipment must also be qualified to ensure full availability of the safety function in case of high electromagnetic stress, which may occur during accident conditions. Two types of testing, which reproduce the actual configuration of the instrumentation and control (I&C) devices installed in the primary equipment, including wiring, are performed on all of the equipment.
Ur%
Ur% min
80
Ur% max
75
Ur% min
Ta°C/Ur%
70 65 Ta
60 55 50
Ta
45 40
Ta max
35
Ta min
30 Ta
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The ABB Competence Center located in Dalmine, Italy, has several recent references for medium voltage switchgear for nuclear plants in Europe: Tihange and Doel in Belgium, Cernavoda in Romania, Oskarsham in Sweden and Leibstadt in Switzerland.
Seismic and airplane impact test qualification
IEC 60980 [2] and IEEE 344 [3] standards represent the two main reference standards for the seismic qualification of safety electrical equipment for nuclear power stations. The response spectra are not defined in either standard, since they can vary depending on the geographic area and building structure. They are therefore normally defined in technical project specifications. A time-history seismic test usually consists of a tri-axial independent multifrequency test performed on the basis of time histories (plots of the acceleration as a function of time) artificially synthesized from a given required response spectrum (RRS). The RRS takes into account the characteristics of the geographic location and of the supporting structure or building ➔ 1. The time-history method is considered the best way to simulate seismic loads during the qualification of equipment. During the seismic test the following
Immunity testing: Electromagnetic compatibility (EMC) qualification tests are performed in order to verify the level of immunity of the equipment from electromagnetic disturbance in a broad frequency range. Emission testing: Electromagnetic emissions radiated and conducted on the wires by each piece of electrical equipment are measured over a broad spectrum. Detailed functional tests are performed on all of the I&C functions, such as protection or control functions integrated into a single piece of equipment. The software qualification process follows IEC standards specifically developed for NPPs; these are described in IEC 60780 [4]. The ABB answer ABB has the products, the expertise and the technical means to ensure that all NPP requirements are met. The ABB Competence Center located in Dalmine, Italy, has several recent references for MV NPP switchgear in Europe: Tihange and Doel in Belgium, Cernavoda in Romania, Oskarsham in Sweden and Leibstadt in Switzerland. For each of these projects, ABB’s products underwent a rigorous qualification procedure. This process verified equipment functionality in the case of seismic events and severe environmental conditions.
earthquakes are simulated:
OBE/S1: an earthquake that produces accelerations where features for continued operation without risks to public safety are designed to remain functional. SSE/S2: an earthquake that produces accelerations for which certain structures, systems and components necessary to ensure the integrity of the reactor coolant pressure boundary as well as the capability to shut down the reactor and
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In addition to ABB’s own products, laboratories and know-how, the company also can rely on a dedicated partnership with state-of-the-art laboratories located nearby containing, for example, a triaxial shake table; in addition, ABB can call on a team of experts on structures for seismic events. Software simulations of seismic events can provide many advantages for nuclear projects since no prototype is
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3 Seismic test arrangement on UniGear zS1 during Doel NPP qualification
4 Example of numerical evaluation of the structure used for analytical seismic qualification
5 Example of amplified deformation on UniGear zS1 structure
needed, therefore achieving shorter scheduling times and a reduction in costs.
ment is used for distribution of energy supplied by diesel emergency generators.
In 2009, Areva NP, an engineering, procurement and construction (EPC) leader in NPPs, certified that the ABB Competence Center satisfies the conditions for “planning and production of medium voltage switchgear for nuclear power plants.”
The equipment supplied was qualified according to IEEE 323 and 344 standards and customer specifications, which included a request for climatic and seismic tests ➔ 2. A specimen switchgear was identified so that all of the characteristics that were part of the supply were included. A qualification program was implemented on these prototypes ➔ 3, achieving a successful outcome.
piece of equipment that has voltage transformers fitted onto removable trucks. As required in the contract, the replacement of all circuit breakers and VT trucks took place within 2010; the site activity was performed along two years, during the annual routine maintenance shut-downs.
MV Switchgear – UniGear zS1 Medium-voltage switchgear is one of the most important links in the power distribution chain. ABB has developed the UniGear ZS1 switchgear with the aim of satisfying all users’ requirements. UniGear ZS1 is a combination of consolidated solutions and innovative components from ABB. The MV switchgear is suitable for indoor installations. Metal partitions segregate the compartments from each other and the live parts are air-insulated. The range of apparatus for UniGear ZS1 switchgear is the most complete available on the market, and includes vacuum and gas circuit breakers and vacuum contactors with fuses. Industry applications Doel is one of two large-scale NPPs in Belgium. The Belgian energy corporation Electrabel, part of the GDF SUEZ group, is its largest stakeholder. In 2009 ABB supplied MV switchgear comprising 18 UniGear ZS1 panels with 12 kV / 1,600 A / 50 kA ratings and equipped with ABB HD4 SF6 insulated circuit breakers. ABB equip-
The qualification process was conceived in two different steps. Industrial and nuclear qualifications were based on IEC
Medium-voltage switchgear is one of the most important links in the power distribution chain. ABB’s UniGear ZS1 switchgear is a combination of consolidated solutions and innovative components from ABB.
The Tihange Nuclear Plant is the other large-scale NPP in Belgium. The primary stakeholder in the plant is again the Belgian energy company Electrabel. The plant has three pressurized water reactors (PWRs), has a total capacity of 2,985 MWe and makes up 52 percent of the total Belgian nuclear generating capacity.
ABB has retrofitted 344 breakers made by CEM Gardy, with HD4 SF6 breakers. On site there are 354 circuit breakers (including 35 spares) and 34 VT trucks (including seven spares). A VT truck is a
and IEEE standards for MV apparatus and switchgear, as well as on the customer’s technical specifications. Seismic tests were performed according to IEEE standards at CESI-ISMES laboratories. The Oskarshamn nuclear power station is one of ten active nuclear power stations in Sweden. With three reactors, the 27 Page 27 1
A seismic switch
Because circuit breakers operate opening and closing currents, as opposed to other switchgear components that are static, in most cases breakers are the equipment most prone to aging. Therefore breakers are the components that are generally in the worst condition and replacing them with new ones is the best solution.
zS1 switchgear
ABB has already performed retrofits on its own as well as competitors’ breakers. The most extensive job was performed at the Tihange NPP where ABB retrofitted 344 CEM Gardy breakers with HD4 SF6 breakers.
In addition to ABB’s own products, laboratories and know-how, the company also can rely on a dedicated partnership with state-of-theart laboratories.
plant produces about 10 percent of the electricity needs of Sweden and its reactors use boiling water reactor (BWR) technology. In 2009 ABB supplied four MV switchgear installations, each of them comprising seven UniGear ZS1 panels with a 12 kV / 1,600 A / 50 kA rating and equipped with ABB HD4 SF 6 breakers. As at Doel, ABB equipment is used for power distribution supplied by diesel generators for emergencies and the equipment supplied was qualified according to IEEE 323 and IEEE 344 standards, as well as the customer’s specifications, which required seismic qualification. Seismic qualification of the MV switchgear was performed by both analytical and testing methods. Both of these were carried out in collaboration with the CESI-ISMES laboratories located a few kilometers from the ABB MV switchgear factory ➔ 4, ➔ 5. Modernization of existing NPPs Retrofitting is the implementation of modern components (primary switching devices and digital protection/control technology) in existing MV installations. The aim of this modernization is to replace only those components that are planned for replacement according to their expected life cycle.
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Renato Piccardo Annunzio Regantini Davide Cattaneo Luciano Di Maio ABB Power Products, Medium Voltage Products Dalmine, Italy renato.piccardo@it.abb.com annunzio.regantini@it.abb.com davide.cattaneo@it.abb.com luciano.di_maio@it.abb.com
References [1] IEEE 323 IEEE standard for qualifying class 1E equipment for nuclear power generating stations. [2] IEEE 344 Recommended practices for seismic qualification of class 1E equipment for nuclear power generating stations. [3] IEC 60780 Nuclear power plants – Electrical equipment of the safety system – Qualification. [4] IEC 60980 Recommended practices for seismic qualification of electrical equipment of the safety system for nuclear generating stations.
Further Reading EN 61000-4 Series Electromagnetic compatibility – Testing and measurement techniques.
Title picture Seismographs are used to record both real earthquakes and to monitor shake-table testing.
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Wave Energy
Waves are a result of the effects of wind on the oceans and seas. This wind originates from the major influx of energy to this planet: solar energy from the sun. The energy contained within waves is around the world is huge; in some places values of 70MW/km of wave front are experienced. In theory it could then be said that huge generating stations could be built which would capture all this energy and supply all or most of our needs. But there are many factors affecting this kind of deployment becoming a reality. Waves are not as consistent as the tide and therefore there is a definite problem with matching supply and demand. This is one of the main reasons that Wave power has so far been restricted to small scale schemes, no large scale commercial plant is in action. Ocean energy comes in a variety of forms such as marine currents, tidal currents, geothermal vents, and waves. All are concentrated forms of solar or gravitational energy to some extent. Moreover, wave energy provides “15-20 times more available energy per square metre than either wind or solar�. The most commercially viable resources studied so far are ocean currents and waves.
The ocean holds a tremendous amount of untapped energy. Although the oil crisis of the 1970s, Increased interest in ocean energy, relatively few people have heard of it as a viable energy alternative. In fact, hydroelectric dams are the only well known mass producing water-based energy, but the ocean is also a highly exploitable water-based energy source. This report provides an overview of the energy found in ocean waves, the current state-of-the art in methods used to extract this energy, commercial prospects, and environmental concerns associated with ocean wave energy extraction.
Some research has been conducted on constructing a heat cycle based on geothermal vents, but this work has led to the conclusion that geothermal vents are not commercially viable [11]. On the other hand, ocean current and wave energy has already undergone limited commercial development and is therefore of more interest. Worldwide demand for electricity is expected to double within the next 20 years. This demand, combined with commitments to signiďŹ cantly reduce CO2 emissions within the same time frame, are facilitating the push for clean, socially acceptable methods of generating power. The ocean is a large, relatively untapped renewable energy resource. The British Department of Trade and Industry has claimed that there are at least 90 million giga watts of energy
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in wind driven waves alone worldwide. This may be compared to the 15 thousands giga watts of energy consumed worldwide. Besides surface wave energy, there are numerous other ways of extracting energy from the ocean. Tidal power includes using the potential energy created by lunar tides at shorelines and rivers. Marine currents such as the Gulf Stream could be used much like windmills to gather wind energy. Other resources like temperature and salinity gradients are also considered of high potential.
A
ccording to London-based Carbon Trust, wave energy can realistically provide over 2,000 terawatts (TWh) of electricity per year (approximately 10% of global energy needs) and eventually generate revenues from wholesale power sales in excess of $50 billion per year. However, according to the Electric Power Research Institute (EPRI) of Palo Alto, CA, a realistic estimate of ocean wave energy potential in the United States indicates approximately 6% of total energy needs with a wholesale market value eventually reaching $16 billion per year.
O
cean wave energy has significant advantages over other renewable energy resources like wind and solar for the following reasons: - Ocean wave energy is a very predictable and consistent (less intermittent) energy resource which means:
Developing ocean energy resources will reduce dependence on fossil fuels (oil, coal, and natural gas), which have limited resources. Also, since ocean energy is not subject to fuel cost increases, this effectively positions ocean energy as a potential hedge against price volatility. Finally, ocean energy technologies produce no emissions of harmful pollutants or greenhouse gases.
Fossil fuels such as coal and oil are not renewable over the span of human generations, and their use may be increasingly limited by environmental concerns over global warming and acid rain. To meet the energy needs of a growing world population, engineers in coming decades will be challenged to generate power economically from renewable energy sources. Despite the fact that nearly 75% of the Earth’s surface is covered with water, waves are a largely unexplored source of energy in comparison to the progress that has been made in harnessing the sun and the wind.
Wave energy systems are built to harness energy from waves and transform it into electrical power. By absorbing the incoming energy, power modules create an area of calm water behind them, contributing to coastal defense and producing a valuable area for other commercial and recreational marine activities. This protected area can be used to create self-financing harbors and breakwaters. Their installation can bring positive environmental and economic spin-offs, such as protection of threatened areas of coastline or provision of an environment suitable for aquaculture development. Artificial reefs substantially improve the local marine bio-density, attracting shoals of fish and providing habitats for the colonization of commercially valuable species. Wave energy systems can act as these artificial reefs while also providing the potential to improve the local inshore marine harvest. Benefits will be greater in areas currently sparsely populated with marine life and devoid of suitable substrate for settlement.
Converting the mechanical energy of waves into other forms of us1- Fewer technical problems related to grid interconnection. able energy (for example electrical energy or compressed air) has inspired new technologies and efforts. According to peswiki.com there 2- Potential for higher $/kWh are about 60 companies with a stake in the wave energy industry. sale price.
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There are three major classes of wave energy conversion devices based on how they interact with the ocean :
Oscillating Water Columns (OWC) 1- Oscillating Water Columns (OWC) are devices that involve creating a structure on the shoreline such that waves enter and leave a static chamber. The motion of the water pushes air up when it enters and pulls air back as it leaves. This oscillation of air pressure turns a turbine to generate electricity.
Overtopping Devices 2- Overtopping Devices consist of a structure that collects incoming waves by creating a reservoir into which only tall waves may crash. Therefore waves must overtop a barrier to be collected. Then the reservoir is emptied out below through a turbine collecting the potential energy of the reservoir. 3- Surface Devices include devices that directly use the motion of the ocean surface. They generally include a floating surface that moves up and down due to the buoyancy force of waves. Tested prototypes include Plamis of Ocean Power Delivery, Power Buoy of Ocean Power Technologies, and Aqua buoy of Finavera. Despite the extreme effort placed on extracting ocean wave energy and the fierce competition that is heating up fast, there are serious challenges associated with a commercially viable ocean wave energy power plant. While there remain difficult open questions on the theoretical side of energy extraction from ocean waves, engineering challenges include, but are certainly not limited to, survivability in the ocean’s harsh environment, and the development of extraction and conversion mechanisms suitably adopted for slow reciprocatory motion of the ocean’s surface. On the deployment and test side, wave energy companies, particularly United States based ones, are involved with serious regulatory issues as well. Although still in the early stages of development, wave energy can and will provide enough power to supply a substantial part of the world energy demand. The wave energy industry is sometimes compared with the wind energy industry some 25 years ago when there was neither a unique design, nor a universal agreement on its future path. Wind industry has converted to a unique design over the past quarter of a century and now is a major player in the energy industry. Having learned from the evolution of wind power, wave energy is expected to come into play in a much shorter time period.
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