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    Potentials of Solar ThermalPotentials of Solar Thermalfor Electricity use in Pakistanfor Electricity use in Pakistan

    Prof. Dr. Azzam ul Asar

    Engr. Rehan AhmadEnr. Farah Mahmood

    NWFP University of Engineering & TechnologyPeshawar, Pakistan.

    OverviewOverview?Solar Technologies

    ?Solar Thermal for Electricity

    ?Photovoltaic versus Solar Thermal

    ?Solar Thermal Prospects

    ?Prospects of Solar Thermal forElectricity 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 orelectricity.

    ?Variations of the annual solar irradiationdepends on? the site

    ? annual efficiency,? specific output and? electricity generation cost.

    ?Converts sunlight into two majortechnologies? Concentrating solar thermal power and? photovoltaic

    operational areas for solar thermal and photovoltaic systemsoperational areas for solar thermal and photovoltaic systems

    depending on the installed capacity and the annual global solardepending on the installed capacity and the annual global solar

    irradiationirradiation

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    Solar Thermal

    ?Solar thermal power is one of the most promisingways to provide renewable energy that cancompete 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 economicsuccess

    ?Dish technology

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

    Solar Thermal?Concentration Solar Power (CSP)? Reflective Devices -----> concentrated suns

    energy ------> Heat transfer medium ------>conventional turbine + generator to produceelectricity

    ? 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 existencefor many years, spread over two centuries.

    ?The Stirling engine converts heat tomechanical power that is, by compressing aworking fluid when it is cold, heating thecompressed working fluid, and thenexpanding it with a power piston to producework.

    ?The Stirling engine works on a closed cyclewith 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 SolarThermal

    ?Research into photovoltaics has beenfocused on improving efficiency becausethere has been no significant decrease inthe inherent cost of silicon wafer area.

    ?PV systems may require additional coolingfor protection in hot regions.

    ?In contrast, solar thermal collectors areprimarily comprised of metal formed into

    simple shapes and coated with appropriatefilms to reduce optical and thermal losses.

    Solar Thermal Prospects

    ?We can work for a promising case for the use ofdistributed solar-thermal-electric generation, basedon Stirling engine technology in conjunction with animproved low cost design of thermal collectors.

    ?Solar electric technologies should be judged byoutput power per dollar rather than by efficiency orother technical merits.

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

    ?Estimated cost per KW can be made attractive with

    predicted modest efficiencies as compared toconventional PV technology

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    Why Solar Thermal?Why Solar Thermal?

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    o ar erma s o ovo a co ar erma s o ovo a c(contd..)(contd..)

    For areas lying near the equator, solar thermal power plant areeconomically 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 widespreadbasis.

    ?This technology can be made affordablethat would lead to widespread deploymentat residential and commercial sites.

    ?This presentation highlights the potentials

    of low-cost solar thermal electricitygeneration technology, suitable fordistributed 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 mostprecious.

    ?A strategy can be devised for Pakistan to exploitsolar resources in a cost constrained manner.

    ?Together with promoting local R&D work and usingour indigenous resources in terms of HR resourceand low cost material, we can make this technologywork for Pakistan.

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

    ?Only low-cost materials and manufacturingmethods are required to realize a solar ThermalElectric System.

    Prospects of Solar Energy inProspects 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 inProspects of Solar Energy in

    PakistanPakistan?Average daily insolation rate

    5.3 kWh/m

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

    ?Jacobabad receives 2,142 kWh of

    solar irradiation/m/year

    Prospects of Solar Energy inProspects 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 fromphotovoltaic, offer the opportunity to

    produce solar electricity in the tropicsat low cost

    Improvements and FutureImprovements and Future

    ProjectionsProjections?Use of high transmission covers and

    selective absorber materials to reduceoptical and thermal losses.

    ?Use of non-imaging CPC (compoundparabolic concentrator) reflectors toimprove collector performance:? It absorbs wide angles of irradiation

    ? needs no diurnal tracking system and seasonaladjustments

    ? results cost reduction and more reliability.

    ? limited overall system efficiency compensated bylower cost of materials and maintenance.

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    Improvements and FutureImprovements and Future

    ProjectionsProjections?Materials like fiberglass, aluminum

    sheets and iron glazing can reduce

    the cost of the collector

    ?Large scale manufacturing ofcollectors and stirling engine

    machines can significantly reduce thecost 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 FutureImprovements and Future

    ProjectionsProjections?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 evenlower efficiencies by working at lower

    temperatures (125 to 150C).

    Improvements and FutureImprovements and Future

    ProjectionsProjections?Losses in Stirling engine due to heatexchangers, fluid flow, mechanical frictionetc. can be eliminated by replacing movingpistons by diaphragms

    ?Same diameter heat exchangers canreduce losses due to sudden expansionand 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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    ConclusionConclusion?Pakistan lies in an area of one of the highest solar

    incidence in the world.

    ? Its geographical location presents excellentconditions for deployment of small and large scalesolar thermal power plants

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

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

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