8/10/2019 (free energy) concentrating solar power_ energy from mirrors.pdf

1/3

parabol\ic troughs, dish/engine systems, )Tj0 -1.2 TD(and central-receiver systems. These technologies can be used to generate\electricity for a variety of )TjT*(applications, ranging from remote power systems as small as a few kilowa\tts \(kW\) up to grid-connected )TjT*(applications of 200-350 megawatts \(MW\) or more. A concentrating solar \power system that produces 350 )TjT*(MW of electricity displaces the energy equivalent of 2.3 million barrels\of oil. )Tj/T1_1 1 Tf0 -2.55714 TD(Trough Systems )Tj/T1_0 1 Tf0 -1.2 TD(These solar collectors use mirrored parabolic troughs to focus the sun's\energy to a fluid-carrying receiver )TjT*(tube located at the focal point of a parabolically curved trough reflect\or. The energy from the sun sent to the )TjT*(tube heats oil flowing through the tube, and the heat energy is then use\d to generate electricity in a )TjT*(conventional steam generator. )Tj0 -2.55714 TD(Many troughs placed in parallel rows are called a "collector field." The\troughs in the field are all aligned )Tj0 -1.2 TD

(along a north-south axis so they can track the sun from east to west dur\ing the day, ensuring that the sun is )Tj0 -1.2 TD(continuously focused on the receiver pipes. Individual trough systems cu\rrently can generate about 80 MW )TjT*(of electricity. Trough designs can incorporate thermal storage\227settin\g aside the heat transfer fluid in its hot )TjT*(phase\227allowing for electricity generation several hours into the even\ing. )Tj0 -2.55714 TD(Currently, all parabolic trough plants are "hybrids," meaning they use f\ossil fuels to supplement the solar )Tj0 -1.2 TD(output during periods of low solar radiation. Typically, a natural gas-f\ired heat or a gas steam boiler/)TjT*(reheater is used. Troughs also can be integrated with existing coal-fire\d plants. )Tj

/T1_1 1 Tf0 -2.55714 TD(Dish Systems )Tj/T1_0 1 Tf0 -1.2 TD(Dish systems use dish-shaped parabolic mirrors as reflectors to concentr\ate and focus the sun's rays onto a )TjT*(receiver, which is mounted above the dish at the dish center. A dish/eng\ine system is a stand-alone unit )TjT*(composed primarily of a collector, a receiver, and an engine. It works b\y collecting and concentrating the )TjT*(sun's energy with a dish-shaped surface onto a receiver that absorbs the\energy and transfers it to the )TjT*

(engine. The engine then converts that energy to heat. The heat is then c\onverted to mechanical power, in a )TjT*(manner similar to conventional engines, by compressing the working fluid\when it is cold, heating the )TjT*(compressed working fluid, and then expanding it through a turbine or wit\h a piston to produce mechanical )TjT*(power. An electric generator or alternator converts the mechanical power\into electrical power. )Tj0 -2.55714 TD(Dish/engine systems use dual-axis collectors to track the sun. The ideal\concentrator shape is parabolic, )Tj0 -1.2 TD

8/10/2019 (free energy) concentrating solar power_ energy from mirrors.pdf

2/3

(created either by a single reflective surface or multiple reflectors, or\facets. Many options exist for receiver )TjT*(and engine type, including Stirling cycle, microturbine, and concentrati\ng photovoltaic modules. Each dish )TjT*(produces 5 to 50 kW of electricity and can be used independently or link\ed together to increase generating )TjT*(capacity. A 250-kW plant composed of ten 25-kW dish/engine systems requi\res less than an acre of land. )Tj0 -2.55714 TD(Dish/engine systems are not commercially available yet, although ongoing\demonstrations indicate good )Tj0 -1.2 TD(potential. Individual dish/engine systems currently can generate about 2\5 kW of electricity. More capacity )TjT*(is possible by connecting dishes together. These systems can be combined\with natural gas, and the )TjETEMC/Artifact BDCQBT/T1_0 1 Tf8.66719 0 0 8.66719 18 7.42256 Tm(http://www.eere.energy.gov/erec/factsheets/csp.html \(2 of 6\)6/5/2004 6\:10:04 AM)TjETEMC

endstreamendobj81 0 obj 4601endobj82 0 objstream/Artifact BDC0 0 0 rg0 iBT/T1_0 1 Tf0 Tc 0 Tw 0 Ts 100 Tz 0 Tr 8.66719 0 0 8.66719 18 780.42256 Tm(Concentrating Solar Power: Energy from Mirrors)TjETEMC/Article BDC

q0 18 612 756 reW* nBT/T1_0 1 Tf13.4823 0 0 13.4823 12.51927 754.71603 Tm(resulting hybrid provides continuous power generation. )Tj/T1_1 1 Tf0 -2.55714 TD(Central Receiver Systems )Tj/T1_0 1 Tf0 -1.2 TD(Central receivers \(or power towers\) use thousands of individual sun-tr\acking mirrors called "heliostats" to )Tj

T*(reflect solar energy onto a receiver located on top of a tall tower. The\receiver collects the sun's heat in a )TjT*(heat-transfer fluid \(molten salt\) that flows through the receiver. The\salt's heat energy is then used to make )TjT*(steam to generate electricity in a conventional steam generator, located\at the foot of the tower. The molten )TjT*(salt storage system retains heat efficiently, so it can be stored for ho\urs or even days before being used to )TjT*(generate electricity. Therefore, a central receiver system is composed o\f five main components: heliostats, )Tj

8/10/2019 (free energy) concentrating solar power_ energy from mirrors.pdf

3/3

T*(receiver, heat transport and exchange, thermal storage, and controls. )Tj0 -2.55714 TD(By using thermal storage, power tower plants can potentially operate for\65 percent of the year without the )Tj0 -1.2 TD(need for a back-up fuel source. Without energy storage, solar technologi\es like this are limited to annual )TjT*(capacity factors near 25 percent. The power tower's ability to operate f\or extended periods of time on stored )TjT*(solar energy separates it from other renewable energy technologies. )Tj/T1_1 1 Tf0 -2.55714 TD(Solar One, Two, "Tres" )Tj/T1_0 1 Tf0 -1.2 TD(The U.S. Department of Energy \(DOE\), and a consortium of U.S. utilitie\s and industry, built this country's )TjT*(first two large-scale, demonstration solar power towers in the desert ne\ar Barstow, California. Solar One )TjT*(operated successfully from 1982 to 1988, proving that power towers work \efficiently to produce utility-)TjT*(scale power from sunlight. The Solar One plant used water/steam as the h\eat-transfer fluid in the receiver; )TjT*(this presented several problems in terms of storage and continuous turbi\ne operation. To address these )Tj

T*(problems, an upgrade of Solar One was planned \227Solar Two. Solar Two o\perated from 1996 to 1999. Both )TjT*(systems had the capacity to produce 10 MW of power. )Tj0 -2.55714 TD(Solar Two demonstrated how nitrate salt \(molten salt\) could be used as\the heat-transfer fluid in the )Tj0 -1.2 TD(receiver and as the heat storage media as well. At Solar Two, the molten\nitrate salt reached approximately )TjT*(1,050\260F \(565\260C\) in the receiver and then traveled to a storage t\ank, which had a capacity of 3 hours of )TjT*(storage. Solar Two demonstrated how solar energy can be stored efficient\ly and economically as heat in )TjT*

(tanks of molten salt so that power can be produced even when the sun isn\'t shining. It also fostered )TjT*(commercial interest in power towers. Two of the project's key industry p\artners have been pursuing )Tj0 -1.2 TD(commercial solar power tower plant opportunities in Spain. )Tj0 -2.55714 TD(Solar energy premiums and other incentives under review in Spain create \an attractive market opportunity, )Tj0 -1.2 TD(providing the economic incentives needed to reduce the initial high cost\and risk of commercializing a new )TjT*(technology. The Spanish project, called "Solar Tres" or Solar Three, wil\l use all the proven molten-salt )TjT*(technology of Solar Two, scaled up by a factor of three. Although Solar \Two was a demonstration project, )Tj

T*(Solar Tres will be operated by industry as a long-term power production \project. This utility-scale solar )TjT*(power could be a major source of clean energy worldwide, offsetting as m\uch as 4 million metric tons of )TjT*(carbon equivalent through 2010. )T