Sahara Solar project to move forward at Munich meet

By Erik Kirschbaum

BERLIN (Reuters) - A group of companies from Europe and northern Africa will meet in Munich on Monday to map out concrete steps for a series of large-scale renewable energy projects worth 400 billion euros ($560 billion) over 40 years.

They will launch a venture to explore the feasibility of harvesting solar thermal energy from the deserts of northern Africa and the Middle East to be used within the next decade or so in those regions and Europe.

Invited by German reinsurer Munich Re, executives from blue chip companies such as Siemens, E.ON, RWE and Switzerland's ABB along with firms from southern Europe and northern Africa will be at the inaugural meeting.

About 10 companies are expected to sign a memorandum of understanding setting up the Desertec Industrial Initiative.

Despite uncertainties associated with such vast multinational projects and concerns about political stability in the Mediterranean region, host Munich Re said the companies were eager to move forward with the next concrete steps.

"We believe the time is ripe for projects like this," said Alexander Mohanty, a Munich Re spokesman. "It's a great vision for the future. But we're not dreamers. This is the start of an industry initiative and we're looking for results.

"We're not just setting up a 'working group' to meet from time to time. The focus is on concrete results. The initiative will be doing lobby work, getting a dialogue going. The issue of the power price is important to be able to raise capital."

The European Union and German government are also firmly behind the projects. EU Commission President Jose Manuel Barroso and Chancellor Angela Merkel both expressly praised the idea behind Desertec at a recent Berlin meeting of energy executives.

Growing global efforts to slow climate change by reducing greenhouse gas emissions along with a projected increase in energy demand in the Middle East and northern Africa make the projects all the more attractive, its proponents say.

Analysts are eagerly waiting for details.

"I think it's a serious project, but it will take a very long time until there will be concrete news," said Commerzbank analyst Robert Schramm.

"The time schedule seems a bit overambitious. The technology is certainly there and it makes sense but there are political factors that need to be taken into consideration regarding the Sahara region."

HARNESSING SUN'S POWER

The Desertec Foundation has noted in six hours the world's deserts receive more energy than mankind consumes in a year.

The projects would use concentrated solar power (CSP) -- a technology that uses mirrors to harness the sun's rays to produce steam and drive turbines to produce electricity -- from the Sahara and deliver to markets locally and in Europe.

Using high-voltage direct current transmission lines there is only a minimal power loss of 3 percent per 1,000 kilometers.

Solar thermal is a well-tested technology from operation since the 1980s of an installation in the U.S. Mojave Desert as well as in Spain, but it is a more expensive source of electricity than fossil fuels.

Desertec officials hope the Sahara could be supplying 20 gigawatts of power -- the equivalent of 20 large conventional power plants -- by 2020 and one day deliver 15 percent of Europe's electricity, helping the EU meet CO2 reduction targets.

"After the founding we're planning to invite more companies to join in," said Michael Straub, head of marketing at the Desertec Foundation in Hamburg.

"At first we'll be studying which countries and which areas could be used for the first plants, and we'll also be studying the costs, the financing and other fundamental questions."

Straub said one project is already moving ahead; it would link power produced in Tunisia with users in southern Italy. He said it was possible it could be on line within five years.

Germany's Solar Millennium, which helped develop Spain's Andasol 1 solar thermal project, will also be at the Desertec meeting as is German solar technology company Schott Solar.

(Additional reporting by Christoph Steitz in Frankfurt; editing by Philippa Fletcher)

-- For Reuters latest environment blogs click on: blogs.reuters.com/environment/

($1=.7184 Euro)

Arizona Solar Power Plant Will Deliver Power Day and Night!

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Written by Jack Moins

Monday, 08 June 2009

In 2013 the world will see the real future of solar technology.  That's when the world's largest dispatchable power plant, the 290 MW Starwood 1 will start producing power day and night, on cloudy or sunny days. Starwood 1 will showcase two critical future technologies. The first is power storage. Without storage, you will only have power when the sun is shining. And while that can work to a point, it will never power the whole world. We'll still need something to take care of the base-load, and that something, as of right now, is coal. Different ideas have been cooked up for storing the power created by solar power plants – batteries, ultracapacitors, hydrogen generation, flywheels – but all of these are far from being affordable enough for large scale power needs. The alternative is to store power as heat before it's converted to thermal energy. Fortunately, there is a fairly good and relatively inexpensive solution to thermal storage, one which Starwood 1 implements. Starwood 1's concentrating troughs feed heated liquid in large insulated molten salt tanks at 734 degrees Fahrenheit. When needed, these tanks will release steam, driving turbines at night or during cloudy weather. The second big technology featured in Starwood 1 is concentrated solar power (CSP). CSP has seen commercial deployments since the 1980s, but has failed to dominate the industry. However, expect that to change as the maximum theoretical efficiencies of concentrated power designs are much higher than those of standard photovoltaics. CSP can be used to enhance thermal (as is done here) or to enhance photovoltaic technologies. When completed Starwood 1 will cover 1900 acres of desert land. Unlike wind turbines there's a low risk of bird strikes, and the construction team is working to minimize the impact on ground-based local wildlife. Flash from the plant (burst of bright light when viewed from certain angles) is a concern, but given the remote location, this shouldn't prove a problem. Locate approximately 75 miles west of Phoenix, the plant will produce enough power for 73,000 customers. The construction will also create 7700 jobs. The construction won't be cheap – the plant will cost $2.7B USD, but it should pay for itself and then some. If it can live up to its promise, which seems likely, expect more CSP plants and thermal storage installations to pop up across sunny remote areas of the U.S. southwest in the near future. Via Green-Energy-News

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