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Potentials of Solar Thermal Potentials of Solar Thermal for Electricity use in Pakistanfor Electricity use in Pakistan

Prof. Dr. Azzam ul AsarEngr. Rehan AhmadEnr. Farah Mahmood

NWFP University of Engineering & TechnologyPeshawar, Pakistan.

Overview Overview ?Solar Technologies?Solar Thermal for Electricity ?Photovoltaic versus Solar Thermal ?Solar Thermal Prospects?Prospects of Solar Thermal for

Electricity Use in Pakistan?Improvements and Future Projections ?Conclusion

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Solar Technologies?All solar technologies make use of sunlight?They differ in the ways they capture and

use solar energy to produce heat or electricity. ?Variations of the annual solar irradiation

depends on ? the site ? annual efficiency, ? specific output and ? electricity generation cost.

?Converts sunlight into two major technologies? Concentrating solar thermal power and ? photovoltaic

operational areas for solar thermal and photovoltaic systems operational areas for solar thermal and photovoltaic systems depending on the installed capacity and the annual global solar depending on the installed capacity and the annual global solar irradiationirradiation

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Solar Thermal?Solar thermal power is one of the most promising

ways to provide renewable energy that can compete with conventional power plants.

?There are three main CSP systems: ?Parabolic trough, Solar tower and the Solar dish

Solar Thermal

?Trough technology:? the most advanced one ? low technical and financial risk? received great attention over the years.?simplest of the previous technologies? lowest efficiency ? favourable economic factors

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Solar Thermal

?Tower technology ? successfully demonstrated with a conceptual and

a pilot plant.? needs to proceed from demonstration to

commercial development. ? economic performance lies between dishes and

troughs? carries the best prospects for future economic

success?Dish technology

? best prospects for off-grid operation, ? Provides highest temperatures ? highest efficiency.

Solar Thermal?Concentration Solar Power (CSP)

? Reflective Devices -----> concentrated sun’s energy ------> Heat transfer medium ------> conventional turbine + generator to produce electricity

? Low environmental degradation? Produces both heat and electricity? can be useful in some industrial applications.? closely resembles the current power plants ? most of the equipment employed in conventional

power plants can also be used for CSP plants.? can easily be integrated into the already existing

electrical utility grid. ? requires short time required for the plant

construction.

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Stirling Engine

?The Stirling Engine has been in existence for many years, spread over two centuries. ?The Stirling engine converts heat to

mechanical power that is, by compressing a working fluid when it is cold, heating the compressed working fluid, and then expanding it with a power piston to produce work. ?The Stirling engine works on a closed cycle

with a gaseous working fluid

COUNTRY CAPACITY MW (2010) ? Algeria 130 ? Australia 100 ? Brazil 100

? Egypt 130 ? Greece 50

? India 130 ? Iran 130 ? Israel 200

? Italy 100 ? Jordan 130

? Mexico 300 ? Morocco 150 ? Namibia 100

? South Africa 100 ? Spain 200

? United States 200 ? Total 2.250

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Photovoltaic versus Solar Thermal

?Research into photovoltaics has been focused on improving efficiency because there has been no significant decrease in the inherent cost of silicon wafer area. ?PV systems may require additional cooling

for protection in hot regions.?In contrast, solar thermal collectors are

primarily comprised of metal formed into simple shapes and coated with appropriate films to reduce optical and thermal losses.

Solar Thermal Prospects?We can work for a promising case for the use of

distributed solar-thermal-electric generation, based on Stirling engine technology in conjunction with an improved low cost design of thermal collectors.

?Solar electric technologies should be judged by output power per dollar rather than by efficiency or other technical merits.

?The proposed strategy deals with solar-thermal-electric system to be designed for fabrication out of low cost materials.

?Estimated cost per KW can be made attractive with predicted modest efficiencies as compared to conventional PV technology

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Why Solar Thermal?Why Solar Thermal?

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Solar Thermal Vs PhotovoltaicSolar Thermal Vs Photovoltaic(contd..)(contd..)

For areas lying near the equator, solar thermal power plant are economically more suitable than PV system up to 45 degrees latitude. Beyond this, PV system are economical.

Prospects of Solar Thermal for Electricity Generation in Pakistan?Solar electric energy systems have yet to

be exploited in Pakistan on a widespread basis.?This technology can be made affordable

that would lead to widespread deployment at residential and commercial sites. ?This presentation highlights the potentials

of low-cost solar thermal electricity generation technology, suitable for distributed deployment.

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Prospects of Solar Thermal for Electricity Generation in Pakistan?No shortage of incident solar energy in Pakistan, ? capital cost of the solar-electric system is most

precious. ?A strategy can be devised for Pakistan to exploit

solar resources in a cost constrained manner. ?Together with promoting local R&D work and using

our indigenous resources in terms of HR resource and low cost material, we can make this technology work for Pakistan.

?There are vast untapped sitting opportunities exist in our Country that can certainly focus this target.

?Only low-cost materials and manufacturing methods are required to realize a solar Thermal Electric System.

Prospects of Solar Energy in Prospects of Solar Energy in PakistanPakistan?Excellent potential for Pakistan

?High levels of solar radiations throughout the year

?Receives on average 19 megajoules of solar energy per square meter

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Prospects of Solar Energy in Prospects of Solar Energy in PakistanPakistan

?Average daily insolation rate –5.3 kWh/m²

?Sun shines for 3000 hrs per annum in south-western province of Balochistan

?Jacobabad receives 2,142 kWh of solar irradiation/m²/year

Prospects of Solar Energy in Prospects of Solar Energy in PakistanPakistan

(contd..)(contd..)

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Prospects of Solar Thermal for Electricity Generation in Pakistan?Use of 1% surface area of Sahara for

solar power plants would be sufficient to meet the entire global electricity demand

?Solar thermal power plants apart from photovoltaic, offer the opportunity to produce solar electricity in the tropics at low cost

Improvements and Future Improvements and Future ProjectionsProjections?Use of high transmission covers and

selective absorber materials to reduce optical and thermal losses. ?Use of non-imaging CPC (compound

parabolic concentrator) reflectors to improve collector performance:? It absorbs wide angles of irradiation ? needs no diurnal tracking system and seasonal

adjustments ? results cost reduction and more reliability. ? limited overall system efficiency compensated by

lower cost of materials and maintenance.

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Improvements and Future Improvements and Future ProjectionsProjections

?Materials like fiberglass, aluminum sheets and iron glazing can reduce the cost of the collector ?Large scale manufacturing of

collectors and stirling engine machines can significantly reduce the cost of the system.

Dish DesignsDish Designs?Southern California

Edison – 500MW announced?San Diego Gas &

Electric – 300 and 900 MW planned?

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Improvements and Future Improvements and Future Projections Projections ?Non-imaging solar concentrators in

conjunction with a free piston Stirling engine is a cost-effective solution for distributed solar power generation.?A lower cost of system (cost/watt)

makes it a better choice with even lower efficiencies by working at lower temperatures (125 to 150° C).

Improvements and Future Improvements and Future Projections Projections ?Losses in Stirling engine due to heat

exchangers, fluid flow, mechanical friction etc. can be eliminated by replacing moving pistons by diaphragms?Same diameter heat exchangers can

reduce losses due to sudden expansion and contraction.?Helium as a working fluid can increase the

output power of stirling engine.?increasing the working fluid pressure can

further increase the output power.

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Conclusion Conclusion ?Pakistan lies in an area of one of the highest solar

incidence in the world. ? Its geographical location presents excellent

conditions for deployment of small and large scale solar thermal power plants

?R&D work and Use of Indigenous Resources can make the difference

?Cheap labor and location near the equator are the main factors, which changes the scenario from the western world

?This vast potential can be exploited to produce electricity by solar thermal technology, which could be provided to off-grid communities.