EMBRACING THE SOLAR CENTURY Š 2011 CARL ANDREWS WHITE PAPER Making a feasible and affordable solution to the climate change dilemma.
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
A Solar Century
Background!
2
Technical and engineering issues form a platform for collaboration!
3
Common Standards & Smart Grids!
3
Standards for Energy Supply from Solar Buildings and Solar Farms!
3
UNFCC as a starting point!
4
Consequences of not having standards!
4
Systems Theory as a basis!
5
Summary of changes proposed, in order!
5
1. Solar Collector Manufacturing: cogenerating collectors!
6
Figure 1 details:!
7
Output ratios for matching loads.!
8
Grid-tie systems: Best range of output ratios for cogenerating collectors!
8
2. Solar collector optics must provide a more consistent energy supply!
9
3. Minimize the materials cost of producing solar electricity, while maintaining high capture capacity.! 10 4. Reduce the materials cost of producing solar thermal end-uses.!
10
5. Make collectors upgradable, and set compatibility standards.!
11
6. Installation methods and costs, manpower, exportability.!
12
7. Balance-of-system development standards!
12
8. Efficient supply chain facilitation!
15
CONCLUSIONS!
15
Appendix A!
19
Appendix B!
20
P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
1
A Solar Century
Background The 21st century is upon us. Too many people are agonizing over the boons of the 20th century that are now swiftly falling away: cheap oil, expansionist economics, and the free reign for corporations to traverse the world and pick the low-lying fruit for profit without responsibility. These are past, and yet there remains great promise for the 21st century, because our science has advanced to a stage where we can feed our economies directly from the sun. In order to accelerate our collective progress toward sustainability in societies of the Americas, the use of sustainable technologies and the knowledge base for installing, maintaining, and upgrading equipment for renewable energy production must grow rapidly. However, in today’s solar industry there are many companies competing for market share, a plethora of different systems, little sharing of technical knowledge, minimal inter-brand compatibility, dangerous materials and methods being used, and other alarming trends. Thus we need intergovernmental and international industry associations to guide the growth of solar. One recent positive development is IRENA: International Renewable Energy Association. This organization has (so far) focused on government policy knowledge transfer. IRENA hopes to set a general framework for feed-in tariffs, renewable portfolio standards, carbon taxes, cap and trade schemes, etc. However, IRENA is not addressing one issue that ought to concern every person who has children: This issue can be encapsulated in this question: Are current products meeting our long term goal to avoid climate disaster? A tremendous amount of resources goes into the built environment, and our residential and commercial buildings are some of the most long-lived things that we have. If we spend our precious money now on technologies that won’t do the job long-term, we will fail because of these “sunken assets”. In other words, if we allow companies to use government incentives to build solar rooftops while offering only a very small percentage of actual acceptance and pass-through of the available sunlight, then this precludes doing the job better, either now or in the foreseeable future, because too much money will be “sunken” into roofs already. In this case, if we fail to get maximum usage of the solar energy for buildings, climate change disaster will be the consequence, not merely the failure of one or two corporations. That is why this issue is the business of everyone, and must include participation by government. Informed and forwardlooking government, that acts together with industry to the degree it can gain cooperation. On his recent trip to Brazil, President Obama offered to set up a collaboration between the two countries to develop clean technology and renewable energy products. Yet there is no shared set of standards on which to base such a collaboration. Let me get more specific, and then show an example of what is possible, and how much that varies from what is currently a popular approach by companies. This paper will help to inform both government and industry. History has shown that it is possible for industry players to come together and determine a set of standards for themselves that increases their overall efficiency and progress. For example, the MIDI convention set by the music industry made it possible for many manufacturers to make various music equipment and accessories and for most of these items to talk to each other enough that an array of equipment could be set up without hiring a team of programmers and engineers. Since music equipment was commonly shipped around the world when marketed, it was a global issue. Industry players were able to forge a standard that moved the whole industry forward. This also needs to happen with solar. While individual governments may be best suited to choose particular incentives and methods of enforcement that will be most beneficial for their region, a solar throughput standard for roofs as a general framework for these incentives should be formed internationally rather than each country acting unilaterally. This paper proposes a set of standards that is appropriate to addressing climate change.
P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
2
A Solar Century
Technical and engineering issues form a platform for collaboration Here are the technical and engineering issues of an international nature that could form a common platform for such collaboration:
Creating common standards to ensure the effectiveness of solar and wind technologies; Educating a new generation of engineers, installers, commissioners, and repairers. Speeding up implementation of technology transfer between countries and corpora-
tions by making it easy for various systems to be made compatible with each other an to increase the introduction of more effective technologies;
Encouraging innovation. These issues can be generally summarized as technology development. While scientific discovery is equally important and benefits from collaboration, it is left out of this white paper and instead is covered by a different organization: the Pan-American Advanced Studies Institute. Industrial implementation between members of the Americas could mean achieving a process that will enable a robust growth of imports and exports in member countries. Also, with a collaborative process, it is possible for the Americas to compete with Europe and China for achieving the state-of-the-art in solar technology. This collaboration would mean that solutions to problems that crop up (from implementing new technology) could be developed anywhere among the Americas and rapidly implemented to all the Americas. Thus it is to our mutual benefit to achieve cooperation in setting up engineering metrics, throughput standards, political support structures, import and export regimes, and standardized solar building schemes, as these would enable such adaptations as smart grids, distributed solar energy farms, integration with wind farms, integrated building energy systems, and international agreements. Let us address these issues methodically.
Common Standards & Smart Grids As we attempt to move toward more sustainable energy and water management and generation, a great deal of international cooperation will be required. Current renewable sources of electricity using up-to-date technologies (solar and wind) are often of an intermittent nature. To get the most out of these energy sources we require smart grids that allow for the transfer of power from where it is currently being generated to where it is currently required. The greater geographic area these grids cover, the more useful these grids become. This suggests that smart grid technologies and standards be developed and implemented across the Americas, and that transnational grids be built to these standards.
Standards for Energy Supply from Solar Buildings and Solar Farms Presently, the supply of energy to the grid from solar energy is less than 2%. The schedule of this supply does not have much impact on utility companies yet. But as this supply grows, it’s schedule will become greatly important. The peak supply level determines the balance-of-system costs. The lower the peak is and the longer the supply curve holds a moderate quantity of electricity, the cheaper solar electricity will be. Utilities in many states are required to purchase solar-generated electricity from both solar farms and individual P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
3
A Solar Century
buildings who generate excess electricity. Scientists have know that storage of energy for non-supply times is a critical cost factor to the solar energy. Therefore, we should do what we can to make the solar supply schedule as even as possible throughout the solar day. For example, in North and South America, networking of electricity grids between countries from East to West will help regulate the supply schedule. For all the Americas, an approach to solar collectors that minimizes the peak and maximizes the constancy of solar energy supply will help. Standards to maximize the throughput of solar energy to local end-uses will also decrease the amount that is sold back to utilities, easing the requirements for grid balancing and energy storage by the utility companies. This will also put less strain on grids in general, and make the adaptation less expensive and more feasible. This paper will specify how that can be achieved.
UNFCC as a starting point In the paper titled: “United Nations Framework on Climate Change latest recommendations to governments�, it is recommended that industrialized countries achieve an 80% emissions reduction in buildings by the year 2050. (This reduction target is set for industrialized countries in order to achieve a worldwide reduction of emissions of 60%, since developing countries do not have enough capacity for emissions reductions of even 60%.) Without a standard set for how much throughput a solar system on a roof achieves, incentives by government will be used by corporations to deploy inefficient solar systems, the adoption of which will financially preclude the emergence of the proper technology which does meet this target.
Consequences of not having standards This strategy of setting a throughput standard is critical because the current trends in the solar industry are moving us further away from this target, not closer. Failure to set clear standards for how to reach this target has already resulted in corporations profiting from receiving taxpayer money without really helping to solve the problem of climate change. We have seen that demonstrated in the opportunism displayed by foreign corporations in Spain (including an American corporation) during 2007-2008, resulting in damaging the Spanish economy and driving up the price of solar equipment, while not fully harvesting the renewable energy potential at each installation in Spain. 1 We can learn from this debacle and set proper standards which will guide development efforts and corporations towards the achievement of much better results elsewhere in the world. To achieve this 80% emissions reduction goal, it is essential to adapt the distributed renewable energy technologies currently being installed in new buildings and retrofit to existing buildings. This distributed energy system is necessary, along with striving for the 25% renewable portfolio standard for our electricity grid, as suggested recently by President Obama. Only the two developments working together, simultaneously, can succeed in addressing climate change issues. The remainder of this paper will address proposed standards for the distributed energy system installed on buildings, keeping in mind it’s interaction with utility grids.
1
Global Green report card on Spain, 2009 P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
4
A Solar Century
Systems Theory as a basis The “systems theory� approach was used to determine the prioritization of changes to current solar designs that would maximize effects throughout the system. These recommendations would radically reshape the solar industry into a collaborative, consortium type of industry, and would remove the opportunities for companies who would damage our ability to reach our goals as a society of stabilizing climate for our children. Yet careful consideration was given to keeping open pathways for innovation from individual companies and allowing for upgrades and enhancements to be incorporated. These recommendations do not involve sacrificing freedom of architectural design, nor do they involve instituting communism or socialism, copying the Europeans, bankrupting government, or any unpalatable alteration of our society. They would however, be a game changer for the established solar industry, and create a revolution in renewable energy production potential that we so urgently need. Once systems theory has been applied, it becomes clear how the guidance of government and cooperative efforts of industry leaders needs to encourage or enforce various changes to the entire system by which we research, manufacture, distribute, install, control, finance, and operate energy systems in buildings. To spread scientific and engineering knowledge and to help train the next generation of scientist and engineers, a new approach to solar energy must also be set up within universities and research institutions, to engage academia and attract qualified students from other countries in the Americas, within programs specifically designed to encourage the advancement of sustainable energy and technology transfer.
Summary of changes proposed, in order We will first examine how co-generation in distributed energy systems, can achieve the 80% target. We will examine how solar collector optics can provide a maximally consistent energy supply. We will consider how to minimize the materials cost of producing solar electricity. We will consider how to reduce the materials cost maximize efficiency of thermal absorbers. We will consider how to engender innovation while maintaining compatibility of sub-systems. We will examine issues of upgradability and repurposing solar collectors on buildings. We will consider the relevance of installation methods to costs, manpower, and exporting. We will discuss the balance-of-system development equipment requirements We will specify an example that meets the above ideals, illustrating new standard guidelines.
P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
5
A Solar Century
1. Solar Collector Manufacturing: cogenerating collectors Presently, we have two separate manufacturing industries: “Solar PV” and “Solar Thermal” collectors. This is by definition a wasteful duplication of effort. More dangerously, it results in installation of systems that do not and cannot ever reduce carbon emissions in most buildings by 80%. Residential and commercial building practices both show a trend towards higher density, resulting is less roof area per total floor area. Solar systems must therefore also attain more energy density. They must accept more of the available energy ( ‘capture capacity”) and process the maximum solar energy per area of roof (or wall) space available. Simple analysis shows that the systems capable of doing this are co-generating solar collectors that deliver both thermal and electrical outputs. Mathematical analysis (see appendix) shows that these outputs need to be within a certain range of ratios to maximize output. Figure 1 below demonstrates this reality in chart form. The typical electrical load of a building is one-third: 33%. The typical thermal load is two-thirds: 66%.2, 3 Obviously, 80% reduction of these loads on conventional fossil fuel energy supplies must include replacement of fossil fuels for at least part of both the thermal load and the electrical load, as neither load can achieve the 80% threshold by itself, even if it were 100% upgraded to renewable energy supply. Both thermal and electric conversion is required, yet the problem remains that roof space is limited, and the use of it by dedicated solar electric panels to supply electrical load diminishes the availability of roof space to supply thermal loads, and vice versa. This is a lose/ lose scenario, as has already been demonstrated in Germany, where two industries are competing for available roof space. The result is that achieving 80% renewable energy, even with the assumption that a 25% RPS on the grid is achieved, is beyond the roof area capacity in Germany and many other places. Is this proof that we can’t do it? Not at all. The solution is to manufacture and install co-generating solar collectors for roof installation that convert light at least to both electricity and hot water, and perhaps with more output options. This enables a much more efficient use of the roof to capture available sunlight. Such collectors are called PV/T or cogenerating collectors. Although photovoltaic panels are approaching 15% annualized capture capacity, and thermal collectors, used for domestic hot water, approach 20% annualized capture capacity, cogenerating collectors have already approached 80% annualized capture capacity. In addition, cogenerating collectors can address looming materials shortages with a design that is more materially efficient. The IEA has already identified this technological change as a priority for a healthy solar industry. However, the IEA has no authority to regulate or incentivize industry. Neither have they specified what ratios are needed, as this proposal does. Therefore, the next steps in the systems approach are also necessary.
2
including air conditioning loads, which can most efficiently be supplied with solar thermal output.
3
Although the electric car trend could theoretically increase residential electrical loads, it wonʼt make electrical loads more than 80% of total loads. P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
6
A Solar Century
Figure 1: Meeting 80% of loads in a residential building with 36 kWh / day average total load.
While the scenario in Figure 1 was calculated using a residential building load profile, if we recognize that cooling loads are essentially thermal loads and can be supplied from solar thermal energy, then we can apply a similar profile to commercial buildings.
Figure 1 details: Problem represented: What is the feasible range of ratios of solar electric to solar thermal conversion that meets 80% of total building load (3y) using renewable energy ? green box = 100% electric load & 70% thermal load supplied –> 80% of total load red box = a more economic ratio: 60% electric load & 85% thermal load –> 80% of load The mathematics in Appendix A show that the grid can supply 40% of electricity load, while we achieve 80% emissions reductions, but only if we use cogenerating collectors. These cogenerating collectors can be no lower than 30% efficient in producing electricity output. To achieve this, we need to employ infrared light capture, using non-silicon cells which are based on Gallium. Gallium is spread widely throughout the earth’s crust, and therefore available on all continents. It is possible to design cogenerating collectors with an IR array @ 30% efficiency. Photovoltaic cells can be added, to get up to 48% efficiency. We have the technology now to do this. It remains simply a set of standard engineering tasks to combine multiple cell arrays into a single solar collector, by splitting the light beam into visible and infrared components. P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
7
A Solar Century
Output ratios for matching loads. Combinations of renewable thermal and renewable electrical energy supply that achieve approximately the 80% emissions reduction target, (assuming 25% renewable grid supply), are shown below. The chart shows that a cogenerating collector system that gets a ratio between 1.4:1 and 10:1 would be capable of achieving 80% emissions reduction. However, at 10:1 ratio, it would be require very large thermal storage and some kind of overheat protection, in climates with cold winters. To reduce storage costs and overheat problems, it is best to design a system wherein 80% of thermal load is met by the collectors, and 73% of electric load is met in the same collectors, using both visible & infrared cell arrays, assuming a renewable portfolio standard of 25% RE on the grid. Then the 80% RE standard could be met, and the solar beam could be removed from the thermal generators for 35-50% of the summer insolation hours – protecting them from overheating in the summer. Moreover, the 2.23:1 ratio would be ideal for any buildings that need to be off-grid, such as isolated buildings and those in remote areas. This ratio requires almost the minimum of roof area, because the total kW capacity is reduced. thermal/ electric ratio
thermal supply
kWh/ day therm
electric supply
kWh/ day elect
total kWh supplied therm + elect.
kWh capacity, collectors
1.4 : 1
70%
16.8
100%
12
28.8
40 1
2.23 :1
80%
19.2
73%
8.6
27.8
28.6 1
2.83 : 1
85%
20.4
60%
7.2
27.6
27.6
3.83 :1
90%
21.6
47%
5.64
27
30 2
10 : 1
100%
24
20%
2.4
24.4
36 2
1 - Collector capacity is determined here by the % conversion to electricity possible. Assumed: 30% 2 - Collector capacity is determined here by the thermal load in winter rather than the average thermal load.
Grid-tie systems: Best range of output ratios for cogenerating collectors The vast majority of systems eventually installed in America will be of this type: grid-tied. With grid-tied systems, the ratio of electrical to thermal supply from solar should be determined to minimize the roof area and number of collectors needed. This ratio can be skewed more towards the thermal end, achieving better economics, and using less roof area. This is because solid state conversion is more expensive than thermal conversion, and grid electricity is available and hopefully partly renewable itself. Many roofs don’t have sufficient solar exposure area to deliver the higher capture capacity (40 kWh/day in this scenario) required for 100% electricity load anyway, and a lesser portion of roofs cannot even deliver 100% of thermal load (36 kWh/day). So a ratio between 2.23 : 1 and 3.83 : 1 of thermal to electrical (see chart above) is more universally optimal. P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
8
A Solar Century
Therefore all cogenerating solar collectors for grid-tie or otherwise energy–assisted systems should be designed to achieve some ratio within this range, in order to achieve the 80% emissions reduction target. This will also have a beneficial effect on utilities, who would be shouldered with fewer and smaller supply transients via their “net metering” buy-back storage systems.
2. Solar collector optics must provide a more consistent energy supply The current paradigm of solar collection on rooftops is predicated upon placing flat collectors on roofs facing South. This results in a bell-shaped curve of acceptance on sunny days, which begins well after the solar day begins and ends well before the solar day ends. On cloudy days, the curve is more flat, but the amplitude is very low. Heat losses increase with colder weather, adding to this problem. For larger buildings, the flux range, and the reliability of solar energy supplied is extremely important. Equipment must be sized for the maximum energy throughput, so a supply with a sharp peak increases the cost of equipment while hardly increasing the sum energy supply. As with Utility companies, who diligently search for methods of “peak load shaving”, large building systems benefit greatly from solar collectors that do not produce a sharply peaked output in midday, and offer more consistent energy supply across changes in weather. Since building trends show more large buildings and fewer small ones, this factor should be a priority for development. The achievement of “low– peak, high–constancy” solar supply To maximize yield requires designing collectors that maximize the capture of diffuse light from the whole sky, and morning and evening light. Then cloudy days would present less consequences to the collector. With the optics configuration shown in figure __ we achieve this. We place the absorbing surfaces vertical instead of horizontal, to give us east and west facing facets that accept sunshine well from the very beginning and until the end of the solar day. On sunny days and cloudy days alike, the collection curve is now a fairly steady plateau, except for a dip in the midday region on a sunny day. This dip can be compensated for with auxiliary reflectors, that reflect the midday sunshine onto both sides of bifacial absorbers. Government subsidy policy-makers and research grantees need to be made aware of these factors, and encouraged to set incentive requirements that encourage or require the above goals to be met by incentive recipients.
P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
9
A Solar Century
3. Minimize the materials cost of producing solar electricity, while maintaining high capture capacity. The main cost of a solar collector making electricity is the photovoltaic cells. Attempts to reduce the cost of these cells have delivered only low-power density cells, which compromise the targets of the UNFCC for combatting climate change. SO, we must refocus on high power density cells: single crystalline silicon or gallium based cells are the most dense in power delivery efficiency. About half of the cost of these cells comes from the polysilicon processing before crystals are grown. The use of bifacial photovoltaic cells– accepting light on both faces– greatly increases the amount of electricity per unit of polysilicon used. Bifacial technology was relegated to special applications until just recently. We now have a proven technology that is 18% efficient on BOTH sides. Using the vertical placement in a parabolic capture devise, it can be illuminated both sides with full strength sunlight. Early bifacial technology was far less efficient on the second side. This means that with half of the materials cost, one can produce solar electricity at 18% efficiency, which is one of the highest conversion rates among all solar photovoltaic cells.
4. Reduce the materials cost of producing solar thermal end-uses. This requirement for success is very important because of the majority role that thermal end-uses play in the building loads. Solar cooling can be counted as a thermal load for reasons that are explained in our white paper on solar cooling. Reducing costs on the thermal side is a bit more complex of an issue. There is the efficiency factor, the manufacturing process factor, the economy of scale in manufacture, and the concentration of the solar energy to allow smaller absorber surfaces. The latter faces safety challenges. Evacuated tubes, when properly sealed, are virtually immune to heat losses during cold weather, and thus are the best solar technology we have for space heating with hot water or steam in colder climates. This being a large portion of residential thermal energy loads, it is recommended to use evacuated tubes except in tropical climates. They have another advantage: when mixing thermal and photovoltaic technologies in one collector, the evacuated tubes can prevent heat buildup on the photovoltaic cells– which compromises performance and longevity– by keeping the heat inside the tubes while the PV cells are outside the tubes. The larger diameter tubes can use less materials per absorber surface and offer some economy of scale in manufacture. ( see our separate white paper on evacuated tube absorber strategies). However, the larger size tubes are potentially more vulnerable to breakage, unless they are covered by another layer of glass.
P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
10
A Solar Century
Concentration of sunlight is a rather complex issue, as on the one hand it requires less absorber materials, and on the other hand it can require very high-tech and expensive absorbing and transporting equipment, and cause fire hazards. So it is easy to go overboard with concentration. Two wise targets to aim for: 1) to heat water to the same temperature that an oil-fired boiler would when used in hydronic heating; 2) to heat water sufficiently to make steam capable of driving a steam catalysis treatment or Stirling Engine. Ideally this temperature would be reachable on a cloudy day. This requires only about 3 suns’ concentration factor.
5. Make collectors upgradable, and set compatibility standards. In Baseball, one must catch the ball before one can throw it. Likewise in solar systems, the amount of solar energy caught by the collector optics, and the concentration factor at which light is captured, determines the baseline for potential throughout the rest of the system. For this reason, optics are too critical to leave to the whims of market forces and a plethora of companies, as is done today. By separating the optics at least partially from the conversion process, we can still save the latter from stiff regulations that would stifle creativity and innovation. Any solar collector that is mass manufactured will have an impact on global warming–whether positive or negative. If governments stipulate that such collectors must have highly efficient optics, and detachable absorbers with means to easily plug-in new absorbers, then we can regulate collectors for maximum throughput while leaving room for upgrades, and even repurposing the collectors for different applications, as building change tenants or use patterns. So, just as vehicles have CAFE standards about how far they must travel on a gallon or liter of petroleum distillate, solar collectors could have standards about how much of the solar day’s energy supply should be captured and sent to end-use conversion units. Certainly at least any government solar tax breaks or feed-in tariffs should be predicated on meeting this standard. Yet the conversion units, remaining separate components, could be freed for continuing R & D work, as they are bound to improve with time. In practice it is quite difficult to separate the energy beam from all conversion means and switch it to a new set of conversions, in the middle of operation, without losing a great deal of potential energy. However, a compromise can be worked out where a third or more of the collected light can be slightly concentrated and channeled to an interface for plug-in units. This approach solves several other problems in the system, as we will see momentarily. Another great benefit of this plug-in configuration is that the beam of light from the collector optic could potentially be switched between TWO conversion units, one on either side of the collector. This switching capacity means that the same collector optic could be used both for space heating in summer and for cooling or making hydrogen or electricity during hot summer months. Energy density related to roof area available is then optimized.
P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
11
A Solar Century
6. Installation methods and costs, manpower, exportability. By manufacturing co-generating solar collectors, the installation process is automatically streamlined. One type of collector and mounting system can be installed continuously upon or within the sun-facing roof plane, and produce both hot water and electricity. The current system requiring two separate installations for that achievement can be reduced to one installation. Yet further refinement and cost savings are possible. Here’s how to accomplish that: • For new construction, collectors should be roof-integrated. This means that the collectors are installed in such a manner that they penetrate the roof, and only the solar absorbing portion of the collector is above the roof plane, while the delivery of energy is beneath the roof plane. Therefore NEMA 3 standard connectors and weatherproof roof penetration systems for pipes and wires are no longer required. Further, the roof profile is smoother and more durable, due to the real-world dynamics of smooth versus broken or sharp surfaces. This penetrating type of installation reduces both the labor and the materials costs of installation, while enabling installations that last much longer before maintenance is needed. The roofing materials are reduced because the collector acts as part of the roof covering envelope. Piping and electrical connections are shorter and rated for interior use rather than exterior use. • Yet this design has another advantage that is even more important: Roofers without special training can do the first phase of an installation by merely bolting the collectors into place to the roof structure ( which would use a specially designed truss system for solar collector support), as part of installing the regular roofing materials. They only need carry one extra tool, a wrench. The remaining system integration work, done inside the attic space, is therefore not subject to the roofing schedule, and can be accomplished in combination with the plumber’s and electrician’s normal schedule of tasks to be accomplished within the attic space. This convenience will greatly reduce the installation labor cost. • For retrofit installation, weatherproof cabinets encasing back-end parts of the collectors into an array can provide some of the same benefits listed above.
7. Balance-of-system development standards Once a particular Solar collector becomes certified to meet the new standards proposed above, it should be produced on a massive scale and sold throughout the Americas. This won’t be hard, since it will outperform all of it’s current rivals, will be applicable, with various plug-ins, to a very wide range of applications and weather conditions, and will not be significantly more expensive than the rivals. Specifications for attaching plug-in units will be made public. Then developers worldwide will seek opportunity to provide plug-in units for the many potential conversions to end-uses that these new solar collectors are capable of supplying with energy. In review, the supply would be far more regular, longer lasting, and slightly concentrated ( 2-3 suns). Since this slight concentration is ample to produce steam, or to match standard boiler temperatures, many conversion configurations are possible. Here are some examples of useful plug-ins:
Stirling heat engines for off-grid systems [Off-grid = cases where 100% of electrical and thermal loads are supplied locally.] P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
12
A Solar Century
There are two methods of generating electricity to compare: an all-solid state solution (longest life cycle), or using a mechanical conversion process, such as a heat engine, microwind or micro-hydro turbine/generator to supply at least part of the electric load. (highest conversion percentage)
For fully solid state conversion, full use of the solar energy is not feasible because a ratio of 1.4 thermal to 1 electrical conversion would require 71% efficiency of electricity conversion from a roof space capable of supplying the thermal loads. No known system can achieve this level of efficiency. So, if 12 kWh represents the electrical load, at 30% of the solar capacity, ( the maximum that can be converted with solid state devises) the full capacity of a solid state based collector array must be 40 kWh. This requires 37% more solar collector area, (likely more than the available roof space) and creates a new problem: a 46% thermal surplus over the thermal load. Even with cogenerating collectors, assuming enough roof space, meeting a 100% electricity generation target would in this case require a robust method for preventing summertime overheat, involving substantial expense in rejecting the 46% excess heat produced. For a mechanical approach, a heat engine may be used with the collectors, and the waste heat recovered to make hot water or steam. Stirling heat engines have proven reliable and flexible, and can be adapted to work with some cogenerating solar collectors. A welldesigned Stirling engine generation system can approach the 71% efficiency (sunlight to electricity) needed, and recover heat in approximately the same quantity as the thermal load. Excess heat rejection can be minimized, meaning the number of collectors required stays reasonable. Therefore heat engines are often better solutions than solid state conversion for off-grid solar applications. Therefore ideally, cogenerating collectors should be designed so that they can be interfaced with Stirling heat engines, when used in off-grid applications.4 The engineering of a cogenerating collector system with the flexibility to be interfaced with either solid state voltaic technology or a Stirling engine, is an especially attractive solution, and is being approached by Energy Pioneers International (see EnPiCo.com)
Thermal energy storage: radiant heating and cooling solves the riddle Energy storage has been identified by some scholarly analysts as perhaps the largest barrier to distributed renewable energy adoption. Since the 80% solution must be thermal as well as electrical, thermal energy storage is a necessity. In addition, relying on electrical storage assumes a system that generates a substantial surplus of electricity at some times, which is usually an uneconomical ratio of electric to thermal production, as was illustrated above. For these reasons, and others, we must vigorously promote the transition to radiant heating and cooling of buildings. The connection is that radiant floor slabs are at present the cheapest way to store thermal energy, chiefly because they serve dual purposes, as floors and heat stores. Also, radiant ceiling panels can achieve both heating and cooling by way of solar or wind energy, and they also make heat storage cheaper and more efficient– the interrelationship of ceilings and floors in radiant heating and cooling means ceiling panels can cause floor slabs to store heating and cooling potential as well. Radiant systems also extend the useful capacity of solar energy due to their low–temperature operation. They are also more efficient: radiant heating typically uses - Note however, that in warmer climates with low heating loads, micro-wind or micro-hydro, if available, are often better supplements to solar. 4
P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
13
A Solar Century
22% less energy than other types of heating to attain equivalent comfort levels. Although this is too large a subject to fully explain in this white paper, the literature claims these energy saving factors. In brief, the reasons common to almost all radiant heating systems are: i) occupant thermal comfort at lower ambient air temperatures, ii) reduced infiltration, and iii) lower system-induced heat loss.5 For cooling, Europeans have achieved as much as 60% reductions in cooling energy loads with radiant cooling.6 If we want to make renewable energy economical, we must adopt radiant heating and cooling as the natural brother and sister of solar energy.
Electrical energy storage Electrical grid systems have increasingly become forced to provide electrical storage to their customers who generate electricity onsite, by governments passing “Net Metering” laws. Thus in increasing numbers of places the grid can be used as an economical means of energy storage by buildings or community energy systems. However, this places a burden upon utility companies without any regulation of the scheduling of this forced “buy” of excess energy generated in many small local PV systems. The proposed regulations above would make “Net Metering” a more fair proposition for utilities. “Net Metering” laws could then be extended to federal laws in all countries of the Americas. For local electricity storage, especially for off-grid applications, battery technology has been revolutionized with nano–materials, and now batteries can last as long and be as efficient as the rest of the renewable energy system. Electrical energy storage no longer needs to be an impediment to meeting the 80% target! They need no more help-Intel, a large corporation, is now planning to begin manufacturing nanotechnology batteries, so we will soon have ample supply at low prices.
Variable ratio cogenerating collectors The other main way to reduce the need for energy storage is with variable ratio cogenerating collectors. It is possible to design a solar system that a) makes both hot water and electricity from the same collectors, and b) can vary the ratio of these two outputs in real time. The result: as a building’s needs change, the control system can cause the solar collectors to adapt their outputs to match load demands. The closer the match, the less energy is wasted and the less energy needs to be stored for later use. This approach together with radiant heating/cooling reduces the energy storage demands and storage costs to a level where the system will become economically competitive with traditional HVAC systems for many buildings, on a life-cycle basis, particularly for multi-residential buildings and light commercial buildings like shopping centers. The addition of this variable ratio output system with a core–and–plug-in design enables a solar system that can be fully integrated with both the building’s roof and the building’s HVAC system, achieving the 80% target elegantly and economically. What was once an add-on system with little possibility of functional control now becomes a highly flexible back–end energy system interfaced directly with all the building’s internal energy-using systems. Equipment
5 6
R.D.Watson & K.S. Chapman; “Radiant Heating & Cooling”; Pub. McGraw-Hill 2002 Greg Cunniff, PE; “High-Efficiency Radiant Cooling”; Pub. Taco Inc. 2008 P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
14
A Solar Century
duplication is thereby eliminated, and solar becomes just part of HVAC, capturing and using as much energy as is possible on the roof area ( and perhaps wall area) available. This kind of R & D should be strongly supported by government research funds.
8. Efficient supply chain facilitation What do I mean by an efficient supply chain? Presently we have warehouses full of solar collectors with warehouse managers sitting at desks being unproductive much of the time. They only receive and deliver merchandise. In large population centers, this can be fairly efficient. However, in more rural areas it is quite wasteful of money, space and labor. The inventory of different types of solar collectors for different applications is quite large, and then these warehouses are duplicated, one for solar electric panels, and another for solar thermal systems. This must be changed. First by cogenerating collectors, using one warehouse instead of two. Next, the efficient use of distribution centers (and of the installers) requires a new approach to how solar systems are designed and assembled. There should be a core unit of a size that fits with construction standards (4 feet by 8 feet), a size almost universal in it’s applicability. This core should be able to produce hot water, steam, or electricity or all three, depending on how it is postassembled at the distribution warehouse site. Thus it can be modularly expanded to any size and type of system. Then various plug-ins are manufactured by various manufacturers to adapt this core unit to various types of buildings and climates. Then inventory is reduced: only one core unit is needed in quantity. The plug-in units are much smaller, and their stock requirements are fewer, so they fit in much less space. Further, the people operating the warehouse also would have the job of post-assembly: pulling and packaging core units with various plug-ins and accessories to create kits for each specific application, with some assembly work involved. This gives outlying distribution center workers closer to full-time work, and makes the distribution process more efficient and economical. Shipping and handling is streamlined as well for the core units, with less common plug-in units being handled on a special order basis, making for efficient ‘justin-time’ stocking & deliveries by van, truck, or train car. The block diagram in Appendix B shows a plausible design for such a core and plug-in system. The site EnPiCo.com gives more details.
CONCLUSIONS Economy of Mass Production
The rationale for government incentives to the solar industry has been that this grows the industry, and as the scale of production increases, the cost decreases, and the efficiency of systems increases. Well, after 30 years of incentives, we have not seen a solar revolution that in any way resembles the scale or dynamic of the personal computer revolution. Efficiency has increased only marginally, and the cost of solar has remained high. It’s recent moderate lowering in cost is more due to world economic recession that due to government incentive programs. Recent history has shown that governments have needed to ween the solar industry off of government subsidy long before the goal of cost reduction was reached. In Spain costs were actually increasing with government subsidy. This is because the market for solar products is quite fragmented into several niche markets with a few products designed specifically for those niche markets. The proposed standards listed below will solve the problem of a fractured market with many niche products that do not lend themselves to mass production. When mass production DOES occur, these standards will ensure it will be because of a truly superior solar collector development, NOT because P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
15
A Solar Century
a giant corporation decided to take a position and make whatever they thought their profit margins and capabilities suggested.
Solar Incentives should be reserved for building solar systems that demonstrate annualized capture capacity of 70%+. Because annualized capture capacity increases the amount of energy fed to the entire rest of the system, capture capacity must be the most weighted factor in standards requirements. The system must pay for itself with energy savings. The more energy captured in a given year, the more money is saved, and the faster the payback. Cogenerating collectors have higher capture capacity than any other type, and some cogenerating collectors have already exceeded this standard. This standard will also pressure companies to make collectors with convex surfaces that capture early day and late day sun as well. This will benefit utility companies, by lowering the peak supply and raising the consistency of power sold back to utilities by building and community energy systems. Preferential incentives for polysilicon minimization, and thermovoltaic R & D The next most weighted factor is the amount of costly photovoltaic or thermovoltaic material required to output a given amount of electricity. This factor can be optimized by using bifacial PV cells, and by concentrating the sunlight before it illuminates the costly material. However, low and medium levels of concentration are preferable, as high levels require all the other materials in the solar collector to be of very expensive composition, and presents fire hazards as well. Our research funding mechanisms need to be oriented around low level concentration and use of bifacial PV and eventually Thermovoltaic arrays.
Solar Products distribution must change through demands by consumers and states Ultimately, the market for solar technology is controlled by consumer demand. The only sustainable way to tie this demand to the right solutions is to educate consumers and organize consumers so that they demand the technology that is a true solution to climate change. While Federal government organizations can set standards for industry, this needs to be in concourse with public education campaigns by State governments defining why these standards represent whole solutions, and someone must restrict government incentives to the type of solar systems that provide whole solutions. This will require deep changes in an industry that is already invested in a status quo of separate solar electric and thermal technologies. Yet team formations can bridge the gaps so that existing companies can merge into future companies that meet the criteria we must demand. Specific Recommendations To achieve the adaptations of our solar industry as outlined above, I submit the following recommendations: * A new incentives program that require cogenerating collectors; replacing the existing programs by 2012. Since cogenerating solar systems can be modular, varied approaches will be used, and they may be installed in phases, there can be two alternative requirements, either one of which procures an incentive: P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
16
A Solar Century
* a) collectors that deliver >70% of the available sunshine to end-uses through a system that generates both heat and power. * b) the whole system achieves 80% of total building energy loads. * A substantial research fund within NREL earmarked for the development of cogenerating solar collectors which can be building integrated, and accessory systems for cogenerating collectors. * Special emphasis should be given to developing collimating optics so that cogenerating collectors can concentrate diffuses light and track the sun passively without moving. As an example, examine the progress made already using holographic optics. * A substantial demonstration project fund (perhaps managed by the Green Building Council) for engineering/architecture companies who will combine cogenerating solar systems in various ways with HVAC systems, particularly with radiant heating and cooling. * A research fund for solar-powered radiant heating and cooling, managed by ASHRAE * Publication of this paper and forwarding it to current solar manufacturers. * Funding enhancement for the National Cooperative Bank on condition that they finance ECLAD’s startup costs. * A research fund for the industrial design of thermovoltaic cell manufacturing in the USA or Canada. Close cooperation with the Canadians who have been researching thermovoltaic crystal growth techniques, (Univ. Victoria) and who have an emerging cogenerating solar collector company (Menova). Support for further development of ENTECH (USA)’s product line, which currently includes one form of cogenerating collector, although it is not roof-mountable. * Close government oversight of our Gallium reserves and controls of the mining and use of gallium, antimony, and cerium, the main ingredients in thermovoltaic semiconductors and hydrogen catalysis. * A fund managed by the EPA for removing Antimony contamination from mine tailing sites and refining it to be used to make Thermovoltaic cells. * A research & development fund for solar steam driven air conditioning with only water as a refrigerant, so that extreme weather incidents will not spread harmful refrigerants into the atmosphere. * A streamlined incentive processing program for solar cogeneration from 2009 to 2012. Currently, installers must apply for two separate incentives as if they were two separate collectors. There should be a special process for cogenerating collectors that combines thermal and electric incentives into one application and makes it quick and clear how to apply. * A fund for roof truss manufacturers to retool to make special roof trusses that: * a) provide the correct inclination for solar collector optimization in their area
P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
17
A Solar Century
* b) are strong enough and spaced properly to accommodate penetrating solar collectors ( a standard width should be set for penetrating solar collectors) * c) do not require cross bracing to the extent that the attic space is occluded from use for installing solar collectors and ancillary equipment such as inverters, heat storage tanks, solar air conditioners, etc. * d) include a training video for roof installers to learn how to install these trusses. * e) provide enough space for R-36 insulation of the ceiling right up to the exterior wall. * Safety standards and demonstration projects for hydrogen storage tanks in residential and commercial building attic spaces. * Safety standards and demonstration projects for using hydrogen as a replacement fuel in gas stoves and heaters. * A public education program about cogenerating solar collectors and why they provide so much more energy output when the full solar exposed roof area is used.
Postlude All the benefits and increases in efficiency described herein depend on or are optimized by using cogenerating solar collectors. Government standards and incentives should therefore be designed to aid cogenerating solar systems over separated systems, since they have more benefits, and are more able to achieve the 80% GG reduction target. When it is fall, and harvest time approaches, is it wise to harvest only the low-lying fruit and leave the stuff that is difficult to reach for later, when it is colder and you are hungrier? Or is it wise to get the whole job done in one go? That is what systems theory is about: getting the whole job done in one go. Without it, we will flounder hopelessly in the opportunism behavior of companies who take whatever subsidy or profit is available without doing the job right. We can plainly see that winter (climate change) is looming. But there is always enough time to do the job right the first time, while we still have the roof space to do it. The rapid development of highly efficient cogenerating collectors only needs the help of government to train the public eye on the developments, fund the development and demonstration projects, and set standards that will pave the way for acceptance by the construction industry. Also, government research should aim at increasing supply chain efficiency as discussed above. We also need a cooperative to provide international distribution of solar equipment at nonprofit costs. A cooperative to distribute international solar technology on a nonprofit basis, Wherein initial funding comes from consumer memberships and perhaps grants or guaranteed loans, even government subsidies. This cooperative will also apply pressure on the manufacturing industry to supply cogenerating solar collectors as the natural and sustainable answer to our climate change problem.
P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
18
A Solar Century
In that light, such an organization, called “Energy Consumers League for Alternative Development� is being spawned. It currently includes a FaceBook group, but could soon expand into a consumer cooperative. Nonprofit distribution, together with the cost savings of an efficient supply chain, which the core-and-plug-ins strategy creates, and combined installation rather than piecemeal installation, can in itself bring down the cost of solar installations in buildings by more than half in many cases. This cooperative distribution approach has the capability to maintain a focus on achieving 80% emissions reductions, making renewable energy affordable, and hastening it towards becoming market competitive without incentives, for most new buildings under four stories tall. A corporation cannot achieve these goals. A cooperative will also cut the cost of retrofitting existing buildings down significantly, by enlisting home-owners as helpers. See http://www.facebook.com/group.php?gid=7060941285#/group.php?gid=18834931875 These proposed changes could streamline the solar industry, cutting out much unnecessary duplication of effort, particularly in the installation, marketing, and integration process.
Electrical energy conversion beyond 18% efficiency requires thermovoltaic cells This is needed to meet the ratios of thermal to electric conversion listed above. Thermovoltaic or thermionic cells convert infrared light, which is missed by photovoltaic cells. Standard photovoltaic cells do not convert infrared light energy, which is about 45% of the flux content of sunlight. So infrared conversion is a crucial element for an efficient cogenerating collector. Use of either thermovoltaic cells or thermionic devises will address this requirement. Cogenerating collectors should convert infrared as well as visible light, but first we must develop the industry to manufacture infrared conversion cells on a mass scale. The technology for production exists. The raw materials and substrate materials can be supplied.7 This will produce collectors that can convert up to 48% of solar to electricity. Current technology converts 18%. Government funded development projects for thermovoltaics could change all that. There is at least one corporation that could easily build a large mass-production plant for these cells, once given government support to developing the market for them. Also, gallium resources should be controlled and developed in a way to guarantee an ongoing supply as the market expands and Gallium use increases. Gallium resources exists in many countries, and Gallium recycling is viable as well.
Appendix A 1) Find the proportions of renewable electrical (z) supply, as the f(z) of y, given 'y' electrical load, matching various proportions of renewable thermal supply (2y), to get 80% of total load. Assumption: 25% of electricity supplied by the grid will be renewable (eventually). Assumption: Thermal load = 2x electrical load (typical integral for residential buildings) 7
WaferTech, a division of IQE Corp., is capable of supplying the wafers used as the substrate material. They will increase their capacity as they see manufacturing tool-up to create a demand for the substrates. P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
19
A Solar Century
Limit: last 10–15% of thermal load (midwinter excess) is very expensive to supply with solar. ( So we want x to be < 0.9, and probably ≤ 0.85) Lets start with the value of x = 85% of 2y = 0.425y (target) 0.80 3y = zy + x2y 2.4y = [z +2x] y 2.4 = z + 2x 2.4 – 2x = z 2 (1.2–x) = z 2 (1.2-0.85) = 0.7 Therefore, if thermal supply is 85% of load, RE electricity supply should be 70% of load. The 30% non-renewable grid supply can be increased by 1/3 to get 4 parts of grid power of which 1 part is renewable ( @ RPS of 25% ). Then z = 0.60y = 60% of electrical load produced by local renewable energy, = 7.2 kWh / 7.2 + 20.4 = 26% of total load. The other 10% RE comes from the grid.
Appendix B Core & Plug-in system schematic
P a A m S o l a r. o r g
1 8 9 8 0 Ly n b r o o k C o u r t , S a r a t o g a C A 9 5 0 7 0 - 3 4 2 7
20