No electric grid, no batteries: OGZEB house to run on hydrogen, solar power

Publication Date:04-March-2007  09:00 AM US Eastern Timezone   Source:Diane Hirth-Tallahassee Democrat.
What's a rectangle of dirt today may turn into an entirely energy self-sustainable house of the future by December. The Off-Grid Zero Emission Building or OGZEB is being built at Florida State University under the watchful eye of mechanical engineering professor Anjaneyulu Krothapalli, with the help of several other faculty and graduate students. "We are building a house that's not connected to the grid, completely run by solar during the day, and the house during the night will be running on hydrogen," he said. "That is unique. All the materials in the house are recyclable and green materials." "In about five years," was Krothapalli's estimation of how soon a house like this could be affordable and produced commercially. On Tuesday, there was a groundbreaking for OGZEB, which will be built just south of Tennessee Street near the north entrance to FSU's campus. The house will incorporate a way to make hydrogen using solar energy and an innovative fuel cell that both currently have patent applications pending. Hydrogen will be used for the big energy consumption in the house, such as heating, cooling and generating hot water. OGZEB's interior design is FSU-generated too, incorporating sustainable materials like bamboo floors. FSU scraped together $200,000 for the project, which is receiving support from private partners like Mad Dog Design and Construction. The FSU Sustainable Energy Science and Engineering Center is seeking more financial support for OGZEB. "We are building the building at cost," said Kristin Dozier of Mad Dog. "We really want the knowledge base to present to our clients."

SunRun PPA

 

 

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SunRun PPA

via Cool Tools on 5/25/09

The cool tool here is creative solar financing. Solar-electric panels are pretty much a commodity, but still high priced. What's new is an innovative way for a homeowner to afford an expensive solar set up. Nine months ago I covered my studio roof with 5 kilowatts of solar panels financed by a solar company. We are generating about 85% of the electricity we use now. Here's how it works.

You sign up with a company that installs high-quality panels on your property for no money down. Zero dollars! On sunny days the panels make electrons which run your meter backwards. The quantity of panels are sized to cover about 80-90% of your current electric bill, so that you should be expected to pay the utility only 10-20% of what you pay now. In addition to the much smaller payment to your electric grid company you will also now pay the solar company a fee based on the number of watts you send into the grid. This is how they make money to cover the costs of installing the panels and their profit. The rates they will charge you per kilowatt will be less than the utility rates, so your total bill for electricity will be less each month. (Not zero, not half, but less.) Because the solar company makes money by how much electricity your panels produce they have a clear incentive to maintain the panels' performance and keep them clean and the inverters going. After 15-18 years, you own the panels and set up free and clear.

You could think of this as a lease-to-own option for solar panels, where the solar company's rents for electricity are cheaper than the utility grid's. Those cheaper rents are made possible in part by government solar subsidizes, which the solar company will claim on your behalf. But this is a business. While you may be generating 90% of your usage, because you are leasing the panels, your total combined bill will not be 90% less. It may only be 10% less per month. But since it costs you nothing or little up front, over 18 years that 10% adds up. In California, one company providing this zero down financing is SolarCity.

While I got a bid from SolarCity, we went with a slightly different deal from SunRun. Rather than zero down, we paid for half of the installation. That investment bought us a better rate for the electricity that we generate. In fact for the next 18 years we pay a fixed rate for electricity. The average California rate is expected to at least double, and we are projected to save $80,000 over 18 years. We could have gone all the way and bought the panels outright and then paid no lease. But we went with SunRun because this path requires either half, or no, down payment, and because SunRun specs out, installs, insures, owns and maintains the solar panels on our roofs. Also, they guarantee a certain level of output performance.

The actual rates that SunRun or SolarCity charge you depends on the particulars of your place -- the solar climate in your town, the pitch and orientation of your roof, potential shade, and local electric rates. Solar engineers use a really cool computerized tool (above) which takes a annualized panoramic to determine your solar potential. From this they can accurately predict your site's solar potential and lay out a design to maximize it by the hour. The image below was taken on the roof of my studio where our panels now lay.

Solar panels these days are low profile (you can't see ours from the street), modular, and require a minimum penetration into the roof. (The picture at the beginning of this review shows the panels being installed on our roof.) Our 28 panels made it through the rainy season with no problems. If there is a problem, the owner -- SunRun -- takes care of it. (There are escrow mechanisms should SunRun go out of business.)

The technical term for this kind of financing is a "solar power purchasing agreement" or a Solar PPA. Solar PPAs were first used for commercial properties -- huge flat roofs converted for collecting electricity. SunRun, SolarCity and a few others have adapted solar PPAs for home residential use. Right now SunRun operates in California, Massachusetts, and Arizona. SolarCity, California and Arizona. SunPower seems to have dealers in many states, though I have not used them. Coverage is being expanded rapidly so it's worth rechecking. Here is a PDF document answering the FAQ on "whether a solar PPA is right for you."

Like a lot of folks, we've wanted solar electricity for a long while but the significant up-front costs of installing it didn't seem to make sense. Zero dollars down makes sense. Half down and a fixed 18-year rate makes sense.

And watching my daily stats on the SunRun website, seeing the meter run backwards, really makes sense.

SunRun

SolarCity

Solar Power Partners
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World's Largest Solar Farm Project For Australia

by Energy Matters  

Perhaps still stinging from criticism on coal receiving the lion's share of clean energy funding in the budget last week, the Australian Government has highlighted a lofty goal - to build four solar farms that generate three times as much power as the world's current largest project based in California. The Rudd Government says it remains committed to ensuring 20 per cent of Australia's electricity comes from renewable sources by 2020.
 
Under the Government's $1.365 billion Solar Flagships plan, such a project would see the farms generating a combined 1 gigawatt of renewable energy generated electricity; the equivalent of an average sized coal fired power station.
 
The new solar farms will be built via a tender to be called later this year. The farms may consist of both solar thermal and solar panel (solar photovoltaic) technologies. 
 
The successful companies and technologies chosen will be based on a competitive assessment, with an important criteria of industry development, including capacity to boost domestic manufacturing and future export potential.
 
In related news, the Government has also announced Australia will become a member of the International Renewable Energy Agency (IRENA). 
 
Launched in January this year; Bonn, Germany based IRENA works on behalf of the renewables sector to promote the acceleration of renewable energy uptake worldwide. The organisation provides advice and support for countries, assists in the development of regulatory frameworks and the building of capacity. IRENA currently has 80 members.
 
The Rudd Government sees the membership of IRENA as a strengthening of Australia's role as a global leader in tackling climate change and the knowledge gained from operating the Solar Flagships program will contribute to the worldwide fight against carbon pollution.

Cooling with Solar Heat: Growing Interest in Solar Air Conditioning

Sunny summer days are beautiful, yet in the office a hot day can be altogether stressful. Because productivity can suffer under such conditions, more and more buildings are being fitted with air-conditioning systems. This is where solar air conditioning comes in: The summer sun, which heats up offices, also delivers the energy to cool them. The thermal use of solar energy offers itself: Days that have the greatest need for cooling are also the very same days that offer the maximum possible solar energy gain. The demand for air conditioning in offices, hotels, laboratories or public buildings such as museums is considerable. This is true not only in southern Europe, but also in Germany and middle Europe. Under adequate conditions, solar and solar-assisted air conditioning systems can be reasonable alternatives to conventional air conditioning systems. Such systems have advantages over those that use problematic coolants (CFCs), not to mention the incidental CO2 emissions that are taking on increasingly critical values.

	Sorption-assisted air conditioning: collector system on the rooftop of Chamber of Commerce and Industry in Freiburg, Germany. Photo: Fraunhofer ISE.

The trend towards solar-assisted air conditioning is met by the organizers of the forum "Solar assisted Air-Conditioning of Buildings" at the convention Intersolar 2002: The German Association for Solar Energy (Die Deutsche Gesellschaft für Sonnenenergie (DGS)), the Fraunhofer Institute for Solar Energy Systems (Fraunhofer Institut für Solare Energiesysteme ISE), the Institute for Maintenance and Modernization of Buildings at the Technical University of Berlin (Institut für Erhaltung und Modernisierung von Bauwerken e.V. an der TU Berlin), and the Pforzheimer Solar Promotion Corporation (Pforzheimer Solarpromotion GmbH) are all offering a two-day international forum on the state of technology, the energy and economic aspects of solar cooling as well as the possible fields of application. Next to German companies, organizations from the entire world have registered including firms from Israel, Ghana, Spain, India, the Netherlands, Belgium, and Austria. This Solar-Report will briefly inform you over the possibilities and technology of solar air conditioning and will also cover economic aspects.

Basic structure of a solar air conditioning system

What is Solar Air Conditioning? Should buildings be cooled with the help of solar energy, then water-assisted air conditioning systems or ventilation systems can be powered with heat that is made available by solar collectors. No long-term intermediate storage is necessary in months of high solar energy gain or in southern lands. The sun can, at least seasonally at our latitudes, provide a substantial part of the energy needed for air conditioning. Combination water-assisted systems and ventilation systems are also possibilities. How does Solar Air conditioning Work? The basic principle behind (solar-) thermal driven cooling is the thermo-chemical process of sorption: a liquid or gaseous substance is either attached to a solid, porous material (adsorption) or is taken in by a liquid or solid material (absorption). The sorbent (i.e. silica gel, a substance with a large inner surface area) is provided with heat (i.e. from a solar heater) and is dehumidified. After this "drying", or desorption, the process can be repeated in the opposite direction. When providing water vapor or steam, it is stored in the porous storage medium (adsorption) and simultaneously heat is released. Processes are differentiated between closed refrigerant circulation systems (for producing cold water) and open systems according to the way in which the process is carried out: that is, whether or not the refrigerant comes into contact with the atmosphere. The latter is used for dehumidification and evaporative cooling. Both processes can further be classified according to either liquid or solid sorbents. In addition to the available refrigerating capacity, the relationship between drive heat and realized cold energy (coefficient of performance; COP) is also an essential performance figure of such systems (see Table 1 at end of article).

Absorption Refrigeration Machines In Germany, closed absorption refrigeration machines with liquid sorbent (water-lithium bromide) are most often operated in combination with heat and power generation (cogeneration) (i.e. with block unit heating power plants, district heating), but can also be assisted by vacuum tube solar collectors (operating temperature above 80 °C). With a single-step process the COP is 0.6-0.75, or up to 1.2 for a two-step process. A market overview is available from the Consortium for Economical and Environmentally Friendly Energy Use (Arbeitsgemeinschaft für sparsamen und umweltfreundlichen Energieverbrauch (ASUE)). Adsorption Refrigeration Machines Closed processes with solid sorbents work with so-called adsorption refrigeration machines (operating temperatures 60° - 95°; COP = 0.3 - 0.7). Solar energy can easily be used in the form of vacuum tube or flat plate collectors. A pilot system used for a laboratory's climate control at the University Clinic of Freiburg is fitted with tube collectors; the Fraunhofer ISE also took part in its scientific conception. The refrigerating machine is composed of two adsorbers, one an evaporator and the other a condenser. An adsorber chamber takes up the water vapor, which is transformed into the gas phase under low pressure and low temperatures (about 9°C) within the evaporator. Granulated silicate gel, well known as an environmentally friendly drying agent, then accumulates it (adsorbs the water vapor). In the other sorption chamber the water vapor is set free again (the chamber is regenerated or "charged") by the hot water from the solar collector (about 85°C). The pressure increases and at the temperature of the surroundings (30°C) the water vapor can be transformed once again into a fluid within a cooling tower (condensed). Through a butterfly valve the water is led back into the evaporator and the cycle begins from the beginning. Both the condensed water (low temperature) and the sorption heat (high temperature) are discharged.

Main components of the system at the University Clinic of Freiburg: Adsorption refrigeration machine (left) and solar thermal system (right).

The thermal operating power for this adsorption refrigeration machine is produced by vacuum tube collectors with a surface area of 170 m². Additionally, heat storage tanks improve the use of the solar heat. A cold storage tank functions as a buffer during short-term demand fluctuations. During colder times of the year, the solar energy heats the air inflow thereby reducing heating costs. Sorption-Assisted Air Conditioning Although the process of sorption-assisted air conditioning has been known for a long time, it has only been used in Europe for about 15 years. In principle, under middle European climate conditions, sorption-assisted air conditioning systems can be operated everywhere an air conditioner is wanted, for example in ventilation control centers. Their economical operation is then possible if cost-effective heat energy is available, i.e. from cogeneration plants, rather than from over loaded district heating systems. New heat sources, offering much promise, are solar thermal systems. Open sorption-assisted air conditioning systems are fresh air systems, that is they dry the outside air through sorption, pre-cool it with a heat reclamation rotor and finally cool it to room temperature through evaporation-humidification. The main principle of sorption-assisted air conditioning is shown in the graphic. The solar energy is used to dehumidify the sorbent.

Basic structure of the process of sorption-assisted air conditioning.

The most important steps of the process are: 1-2 Sorptive dehumidification of outside air with simultaneous rise in temperature through the freed adsorption heat 2-3 Cooling of the air in the heat reclamation rotor in the countercurrent to the exhaust air 3-4 further cooling of air through evaporation-humidification; the air inflow to the building has a lower temperature and less water vapor than the outside air 4-5 Heating of the air and if necessary addition of water vapor 5-6 Lowering of building's exhaust air temperature through evaporative cooling in the humidifier 6-7 Heating of exhaust air in the countercurrent to the air inflow in the heat reclamation rotor 7-8 Further heating of the exhaust air through external heat sources (i.e. solar thermal system) 8-9 Regeneration of the sorption rotor through the desorption of the bound water

At present, systems with rotating sorption wheels (sorption rotors) are mostly in use. The sorption wheel has small air channels that create a very large surface contact area, which has been treated with a material that easily takes up moisture, such as silica gel. The inflow air is dehumidified in one of the two sectors of the rotor and heated through the adsorption process (the exhaust air serves to dry the rotor). Finally, the inflowing air is cooled down in a heat reclamation rotor. The heat transfer here is made possible through the contact between the air and the rotor material. The last step in cooling the inflowing air is with conventional evaporation humidification. How well do Solar-Assisted Air Conditioning Systems Operate? Scientists of the Freiburg Fraunhofer Institute for Solar Energy Systems ISE (Freiburger Fraunhofer Instituts für Solare Energiesysteme ISE) tested solar assisted air conditioning systems for a study of the International Energy Agency (IEA) in the context of the TASK 25 "Solar-Assisted Air Conditioning of Buildings". Detailed descriptions and results of the compared systems can be gathered from the study's conclusion [1]. Year simulations of five variants of a solar-assisted system for air conditioning were conducted and compared to a conventional system for different climates (Trapani/Sicily; Freiburg and Coenhagen). Energy Balance Without the use of solar energy, thermally powered climate control raised the primary energy use (thermal and electrical) for all of the tested locations. The reason for this is the lower operating numbers of this process in comparison to electrically powered compression refrigeration machines. Whether absorption or adsorption refrigerating machines are used, a solar-covered share for cooling of 30 % (Freiburg) and almost 50 % (Trapani) is required to affect a primary energy savings. The solar-covered share for cooling is the portion used for cooling during the summer that comes from heat made available by the solar thermal system. With coverage shares of up to 85 %, the primary energy use can be decreased by over 50 % compared to the conventional reference system. The results were ascertained from an example reference office building and can therefore not simply be applied to other cases or buildings. In Trapani the sorption assisted air conditioning, in combination with a compression refrigeration machine, led to a small primary energy savings with a solar coverage share of 30 %. If the sun delivers 85 % of the heat for the air conditioning, then just about 50 % of the primary energy can be saved. In this case there are two apparent positive aspects: the sorption-assisted air conditioning can effectively be used for air dehumidification and additionally it can achieve relatively good overall efficiency.

	Photo: Sorption-assisted air conditioning system in Portugal.

Cost Effectiveness Although over 20 systems that use thermal solar energy to air condition buildings and that can be technically and economically assessed have been installed in Germany, there are still a number of obstacles to be overcome when it comes to the implementation of solar-assisted air conditioning. In the twelve countries taking part in the TASK 25 of the Solar and Heating Program of the IEA, experience with about 30 systems has been gained and currently 10 systems are being tested as a part of a demonstration program. Such pilot and demonstration programs are still necessary so that cost reductions become possible and so that relevant energy savings can be assured. Standardized programs, matured concepts and the development of components are starting points that can contribute to improved cost effectiveness and wide applicability of solar-assisted air conditioning. Because solar cooling is based on thermally driven processes instead of the normal electrical cold production, the costs for the used heat plays a central role: a fundamental problem arises from the inherently higher costs of solar heat compared to heat energy produced by fossil fuel systems or waste heat. Experts at the Fraunhofer ISE expect no economical advantages of the solar air conditioning in this respect. Their use becomes interesting if favorable requirements for a high output of solar heat are present and if the system also delivers energy for heating. The cost of electricity could also pose an argument for solar cooling: The thermally powered cooling process requires only a fourth (absorption/adsorption) or half (sorption-assisted air conditioning) of the electrical power required by the conventional reference system. The ISEs comparative testing showed that during the process the sorption-assisted air conditioning connected to a conventional machine (compression refrigeration machine) represents the most promising system combination, at least for a Mediterranean climate. The sorption-assisted air conditioning produced the lowest costs at all locations, while the adsorption machines were the most expensive solution. The scientists at the Fraunhofer ISE see a chance for sorption-assisted air conditioning in the cooperation between German facilities and companies that have gained experience with the operation of sorption processes for climate control and large solar thermal systems. Using this know-how, especially in Mediterranean regions, a gap could be found in the market.

Process	closed		open
Coolant circulation	closed refrigerant circulation systems		open refrigerant circulation systems (in contact with the atmosphere)
Process baic principle	cold water production		air dehumidification and evaporative cooling
Sorbent type	solid	liquid	solid	liquid
Typical material systems (refrigerant/sorbent)	water- silica gel ammonia- salt*	water-water-lithium bromide, ammonia- water	water-silica gel water- lithium chloride- cellulose	water- calcium chloride, waterlithium chloride
Marketable technoloy	adsorption refrigeration machine	absorption refrigeration machine	sorption assisted air conditioning	-
Marketable output [kW cooling]	adsorpzion refrigeration machine [50 - 430 kW]	absorption refrigeration machine: 35 kW - 5 MW	20 kW - 350 kW (per module)	-
Coefficient of Performance (COP)	0.3 - 0.7	0.6 - 0.75 (one step) <1.2 (two step)	0.5 - >1	>1
Typical operating temp.	60 - 95°C	80 - 110°C (one step) 130 - 160°C (two step)	45 - 95°C	45 - 95°C
Solar technology	vacuum tube collector, flat plate collector	vaccum tube collector	flat plate collector, solar air collector	flat plate collector, solar air collector

*still in development

Table 1: Overview of processes for thermally powered cooling and air conditioning

Material and Pictures: Fraunhofer ISE: Solarserver Editor: Rolf Hug. We thank Dr. Hans-Martin Henning and Diplom Engineer Carsten Hindenburg for their friendly support.

EFFECT OF PARABOLIC TROUGH SOLAR COLLECTOR ORIENTATION ON ITS COLLECTION EFFICIENCY

Authors: A. S. Hegazy ^a;  M. M. El-Kassaby ^b; M. A. Hassab ^b

Affiliations:	a Mechanical Power Engineering Department, Monoufia University, Egypt
	b Mechanical Power Engineering Department, Alexandria University, Egypt

DOI: 10.1080/01425919508914275

Publication Frequency: 4 issues per year

Published in: International Journal of Sustainable Energy, Volume 16, Issue 3 January 1995 , pages 173 - 183

Subjects: Alternative & Renewable Energy Industries; Alternative Fuels; Energy Conservation; Green Buildings; Power & Energy; Power Electronics; Renewable & Sustainable Energy; Solar Energy; Sustainable Engineering;

Formats available: PDF (English)

Previously published as: International Journal of Solar Energy (0142-5919) until 2003

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Abstract Parabolic trough solar collector PTC is often oriented with its axis horizontally in the North-South or East-West direction. However, it may be set in a position where its axis makes an angle Ψ with the south direction. The main objective of the present work is to study the effect of this angle on the collection efficiency. An algorithm for calculating the collection efficiency for any time period has been developed. The results obtained by using this algorithm by using this algorithm show that the maximum daily collection efficiencies ηc,d all over the year are obtained for the N-S orientation at sites having latitude angles Φ ≤ 15°. For latitude angles Φ > 15°, ηc,d are much higher in summer days than in winter ones for N-S orientation. In the case of orienting die collector with an angle 70° lt; Ψ ≤ 90°, ηc,d are higher in winter days than in summer ones This orientation is preferable to obtain almost constant output of PTC through the whole year. The results show also that a trough oriented with an angle of 70° from N-S direction has almost a constant daily collection efficiency all over the year in order of 82% when considering the reflectivity of the collector surface equal to unity. Also, the effect of orientation on yearly collection efficiency ηc,y are minor at latitude angle Φ between 30° and 40° while the effect of orientation becomes important outside this range.

Keywords: Parabolic trough collector; Collector orientation; Collection efficiency; Latitude angle; Incident angle

Making the desert bloom with solar flower power

By Rachel Neiman   May 13, 2009 Rising up, like a mirage in the middle of the desert outside Eilat, is a giant yellow tulip in whose heart lies a massive crystal. Surrounding it: a field of mirrors that slowly move back and forth, following the sun.  Hallucinatory though it may sound, this is no mirage. The tulip is actually a solar tower with an aperture that directs sunlight into a solar receiver that drives a high-powered turbine, and the 30 tracking mirrors below are called heliostats.  It's an ambitious project initiated by Israeli company AORA to construct the world's first solar-thermal powered gas turbine station. The plant, with its distinctive 30-meter high tulip-shaped tower, is now nearing completion at Kibbutz Samar in Israel's southern Arava region.  AORA, of Israeli EDIG group, is a developer of applied ultra-high temperature concentrating solar power (CSP) technology. The breakthrough of CSP is that it can power a 100kW gas micro-turbine; other solar technologies currently available can only power much larger steam turbines. AORA says it is the worlds' first company to commercialize the use of a solarized gas turbine engine.  The government recently showed support when Minister of National Infrastructures, Binyamin Ben Eliezer signed AORA's license provide solar electricity to the national grid -- the first such license to be granted by Israel to solar-thermal technology.  Being able to run the equivalent of a jet engine on solar power, means the system is efficient at far smaller power blocks, Yuval Susskind, COO of AORA, explains to ISRAEL21c. This enables smaller scale projects that require less land and shorter towers (30m vs. 70-120m and more), and which are easier to build, finance and operate.  "Israel has all the climate conditions, but we don't have huge available tracts of land. AORA is the first to bring the size of a solar field down to something like a soccer pitch or a baseball diamond," says Susskind.  Business looks bright - abroad  The installation at Samar will be the model for many more to come, says Haim Fried, CEO of AORA, and will include the framework for selling power to the national grid over a long-term period.  The company expects to begin power generation any day. Once it begins generating power, Fried says, the Samar unit will provide 100kW electric power to the grid, as well as 170kW thermal power - enough to supply 50 households at an average of 2kW per household. "That's the average use in Israel. The US is a bit more," he explains.  Fried notes that selling power to the local grid close to the customer base is more efficient because there is no need to step up and down voltage, as is done when transmitting power from a central power station. By generating locally, the power is fed in low voltages, via the local distribution grid, for standard domestic use in the home. It also relieves the load on the high voltage distribution grid.  Location is key, he adds because AORA's installations require direct radiation. "The set up cost is the same in the Arava or Tel Aviv but for the same investment I get more direct sunshine at Samar, so I'll get more power out of it."  The company's business plan has two profit centers: in Israel it will sell power to the national grid through partnerships. Outside Israel, the company will set up joint ventures with local partners to build solar power stations and sell clean energy to the grid.  Costs haven't been finalized yet, but Fried says installations will be competitively priced and estimates that AORA will become profitable after selling 20 units.  "We're also probably going to do a joint venture in Spain," he adds. "We want to do more in Israel but there's a problem with the feed-in tariffs, which are too low. In Spain, they pay 29.9 eurocents, which is much more favorable. If Israel doesn't change the rates then we'll have to do more business outside."  Sunny technology  The AORA system is hybrid, meaning it can run on solar, as well as almost any alternative fuel, including biogas, biodiesel and natural gas. Being located in an agricultural community such as Samar, Susskind points out, means ready access to unlimited amounts of biogas, courtesy of the kibbutz cowshed. "So it can run on sunshine during the day, biogas at night and be operational 24 hours a day," he says.  The system is also modular and scalable; more base units - each comprising a tulip tower and 30 heliostats on a half-acre of property - can be added as demand grows.  Modularity enables each unit to be located independently with no need for one large, flat, contiguous expanse of land. Strung together, the units can form a utility-scale power plant. Being modular also means greater reliability, the company states, as servicing a single base unit does not require a complete shutdown.  The key components of AORA's Power Conversion Unit (PCU) are the micro-turbine and the solar receiver, whose technology resulted from collaboration with the Weizmann Institute and Rotem Industries.  The patented receiver uses the sun's energy to heat air to a temperature of 1,000 degrees Celsius and direct this energy into the turbine. The turbine then converts this tremendous thermal energy into electric power.  The solar receiver and some other key components are proprietary technologies and will always be manufactured in Israel, says Fried. However, other components, such as the tower and heliostats, are made of simple materials and can be manufactured wherever a base unit is to be set up according to AORA's specifications.  The company unveiled the Samar project in February, at the annual Eilat-Eilot Renewable Energy Conference. "The response was very positive - which is a great compliment because of the high professional level there," says Fried.  "Greentech has to look good"  AORA's tulip is painted bright sunny yellow. Susskind says this was because the dusty red of the Arava hills overpowered the gold color. "One reason for selecting Samar was its proximity to the highway. I want every kid to see this tower when they're heading for a family vacation in Eilat," he says.  The company hired architect Haim Dotan to design the tower. "We didn't think we could afford it but we met with him, and told him about our vision: that there would be many towers like this all over the world. He was so excited about the project that he said he would do it in any case. He said it would make the desert bloom - that's why it's in the shape of a flower. He loves the desert and wants it to be beautiful."  AORA also has a vision of setting up a roadside attraction for tourists: an alternative energy education center that will showcase not just the company's own technology, but other cleantech being developed and tested in the region as well. The company has already been in talks with the regional council, which is interested in the project.  After the Samar facility is completed, AORA plans to expand into larger scale power generating plants of 5MW and more. "By late 2009, we plan on setting up our first international installations in strategic markets," says Fried. These include the Mediterranean, southern Europe, Australia, California, Arizona and the US Sun Belt states. At a later stage, the company aims to enter the African market. "We view China - where we already successfully constructed and operated a pilot unit - Africa and other remote regions as the true market for the AORA system," says Fried.
	© 2001-2008 ISRAEL21c.org. All rights reserved.

Concentrating Solar Energy Technologies Explained

May 12, 2009

by Mike Taylor, Director of Research and Education, Solar Electric

Q: What are the different types of concentrating solar energy technologies? Why are they limited to the southwestern United States? -- Bertha Z., Berea, KY

A:

There are two main types of concentrating solar energy technologies: concentrating photovoltaics (CPV) and concentrating solar thermal (CST). Together they are commonly referred to as concentrating solar power (CSP), although sometimes CSP is used interchangeably with CST.

1. Concentrating photovoltaics (CPV) uses lenses or mirrors to focus or increase the sun's light on a photovoltaic solar cell or panel.  This technology includes both a low-concentration approach, which increases the sun's magnification by less than 5 "suns," and high concentration approach, which can increase the magnification by hundreds of suns.  High-concentration CPV uses focusing lenses to concentrate the sun's rays on a single, high efficiency solar cell that is very small, on the order of 1-centimeter square.

When you hear about a new world record for PV efficiency that exceeds 40%, it is generally this type of technology they are utilizing.  CPV's "better mousetrap" uses less photovoltaic material (tiny, high efficiency cells), concentrates the sun and increases performance, hopefully enough to offset any additional costs.

2. Concentrating solar thermal (CST) technology uses mirrors to focus the sun's light on a heat capturing point, the heat from which can then be either used directly or converted to electricity.  The three basic designs of CST are troughs, towers and dish-engine systems.

Troughs are set-up in large horizontal fields that contain long loops of piping (many kilometers for large installations).  The pipes collect the 600+ degree (F) heat from light reflected off mirrors that concentrate the sunlight in a line on the pipes. Troughs have the longest proven operating history and the least number of unknowns for CSP technology project development.

Towers use a mirror field that is set-up around the tower. The mirrors focus sunlight on a heat receiver at the top that collects the heat and transfers it to piping inside the tower where is it circulated and used to make electricity.  The design minimizes the field of piping to the vertical tower height to a few hundred meters and can reach temperatures in excess of 1000 degrees (F).  While currently there are very few commercially operating tower installations, based on announcements, this technology may grow rapidly. 

Dish-engine systems look like satellite dishes and focus light on a Sterling engine mounted on an arm in front of the mirrors.  Each dish-engine is an autonomous generator—unlike the other CSP technologies that use a central power plant design—and utilizes a temperature and pressure difference to produce kinetic movement inside the engine, which is then converted to electricity.

An interesting development for troughs (and possibly towers in the future) is the interest on the part of utilities in "hybrid-solar power plants," which include the pairing or retrofitting of natural gas or coal power plants with the thermal input or boost from CSP.

The one thing that is common among the different kinds of concentrating solar power technologies is that unlike traditional photovoltaic panels, they need "direct normal" solar radiation, i.e. sunlight that can cast a shadow.  A certain percentage of solar radiation is made up of diffuse or scattered light, caused by clouds, humidity or particulates.  Solar resource measurements are reported as either "direct" normal radiation (no diffuse light) or total radiation (diffuse + direct). 

The southwest has the highest percentage of "direct normal" radiation of nearly anywhere in the world, making this one of the best regions for development of CSP.   However, there is one CSP trough project in Florida—a hybrid CSP plant that will augment a natural gas plant—and a number of trough and tower projects in Spain.  CSP will work in both areas, but performance will be commensurately reduced based on the direct normal radiation profiles.

The CSP industry is growing fast in Spain and the United States, and SEPA is tracking over 5,000 MW of new project announcements that are slated for development over the next five years.  Not all of them will be built—permitting, financing, technology and other factors need to fall into place first—but the industry is poised for rapid growth regardless of any individual project's outcome.

http://www.renewableenergyworld.com/rea/news/article/2009/05/concentrating-solar-energy-technologies-explained

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