Department of Mechanical Engineering A.D.Patel Institute ... · one pilot demonstration unit (10 MWe SOLAR TWO) with two years of operating experience and by one pilot experimental

By:Dr. B. M RamaniAssociate ProfessorDepartment of Mechanical EngineeringA.D.Patel Institute of Technology (CVM institute)New V V Nagar

Introduction

Present Energy scenario

Need of Renewable sources

Solar Energy

Solar Energy Technology

Barrier

Latest developments

Conclusion

28-Apr-11 2Dr. B.M.Ramani, ADIT

28-Apr-11Dr. B.M.Ramani, ADIT 3

ENERGY IS A BASIC INGREDIENT OF LIFE

Energy

Non Renewable Sources

Coal

Oil

Gas etc.

Renewable sources

Solar

Wind

Wave

Geothermal etc.



Global worming

Depletion of fossil fuels

Environmental hazards

Health hazards

Life Cycle costs versus running costs

The pinnacle of fossil fuel usage is passed. Its usage will now

decay exponential and in the next 100 years will gradually die.


SOLAR ENERGY

Key features:

It is the most promising renewable source of energy.

It is an essentially inexhaustible source of energy.

It has potential to meet a significant portion of the nation’s

future energy need because of its quantitative abundances.

It is clean and environment friendly source of energy.

Limitations

It is diluted source of energy.

Its availability varies widely with time.

It needs storage system.



SOLAR ENERGY TECHNOLOGY

Technology

Direct Conversion

Solar cell Photovoltaic

Indirect Conversion

(Solar Thermal)

1. Low Temperature

2. Medium Temperature

3. High Temperature


1. Photovoltaic or Solar electric system

Solar

Radiation

Load

Contact grid


2. Solar collector or Solar Thermal System

Solar

Radiation

Load

Thermal

Storage

Auxiliary

Air blower

Solar

Collector


Solar

Thermal

Low Temperature

-Air and Water heating

Medium Temperature

-Process heating

-Small capacity power

generation

High Temperature

-Medium to high capacity

power generation


A 100 liters capacity SWH can replace an

electric geyser for residential use and

saves 1500 units of electricity annually.

A SWH of 100 liters capacity can prevent

emission of 1.5 tones of carbon dioxide

per year.

Savings/ Sustainable


MIED

IIT ROORKEE

Low-Medium Temperature applications

To make solar high flux, with high energetic valueoriginating from processes occurring at the sun'ssurface at black-body-equivalent temperatures ofapproximately 5800 K usable for technical processesand commercial applications, different concentratingtechnologies have been developed or are currentlyunder development for various commercialapplications.

Such solar thermal concentrating systems willundoubtedly provide within the next decade asignificant contribution to efficient and economical,renewable and clean energy supply.


Concentrating solar collectors

1. Parabolic trough system: at thereceiver can reach 400° C andproduce steam for generatingelectricity.


Parabolic trough system

Trough systems use linear concentrators ofparabolic shape with highly reflective surfaces,which can be turned in angular movements towardsthe sun position and concentrate the radiation ontoa long-line receiving absorber tubeThe absorbed solar energy is transferred by aworking fluid, which is then piped to a conventionalpower conversion system.The used power conversion systems are based onthe conventional Rankine-cycle/steam turbinegenerator or on the combined cycle (gas turbinewith bottoming steam turbine).





Trough power plants are highly modular and arealready applied up to 80 MW unit capacity using athermal oil heat transfer system.


For hundreds of years, people have wanted to harness the sun’s

power for weapons, heating, and many other uses to make their

lives more comfortable.


The upper process temperature iscurrently limited by the heat transferthermal oil to 400°C.The heat transfer thermal oil adds extracosts of investment and of operating andmaintenance.Depending on national regulations,environmental constraints from groundpollution by spillage of thermal oil couldoccur.

Technology Challenges


Some absorber tubes are still object ofearly degradation; reasons are the risk ofbreakage of absorber envelope glass tubeswith loss of vacuum insulation anddegradation of the absorber tube selectivecoating.High winds may break mirror reflectors atfield corners.Low-cost and efficient energy storagesystems have not been demonstrated up tonow.The direct steam generation troughtechnology is still in a developmental stage.


Morocco: 30 to 50 Mwe capacity; promoted byindustrial groups; with allocated 40 to 50 millionUSDollar GEF grantIndia: 140 MWe naphta-fired ISCCS plant inMathania/Rajasthan; 35 MWe equivalent solar capacity;promoted by industrial groups; with allocated 49 millionUSDollar GEF grant and 100 million US-Dollar loan of theGerman KfW-bankIran: Feasibility study for the implementation of a 100MW natural gas fired combined cycle plant with a 200000 – 400 000m² parabolic trough field in the desert ofYazd contracted with its own national funds.Mexico: 310 MWe natural-gas-fired ISCCS plant in theNorthern Mexican desert; 40 MWe equivalent solarcapacity; promoted by industrial groups; with allocated40 to 50 million US-Dollar GEF grant.

Installed/Ongoing Projects



2. Central tower system: The reflected raysof the sun are always aimed at thereceiver, where temperatures wellabove 1000° C can be reached.

Central receiver systems use heliostats totrack the sun by two axes mechanisms followingthe azimuth and elevation angles with thepurpose to reflect the sunlight from manyheliostats oriented around a tower andconcentrate it towards a central receiversituated atop the tower.This technology has the advantage oftransferring solar energy very efficiently byoptical means and of delivering highlyconcentrated sunlight to one central receiverunit, serving as energy input to the powerconversion system.

Central Receiver Systems (Central Tower)





In this plant, the solar energy is collected bythousands of sun-tracking mirrors, calledheliostats, that reflect the sun’s energy to a singlereceiver atop a centrally located tower.The enormous amount of energy focused on thereceiver is used to generate high temperature tomelt a salt.The hot molten salt is stored in a storage tank,and is used, when needed, to generate steam anddrive the turbine generator.


After generating the steam, the used molten saltat low temperature is returned to the cold saltstorage tank.From here it is pumped to the receiver tower toget heated again for the next thermal cycle.The usable energy extracted during such athermal cycle depends on the workingtemperatures.




In spite of the elegant design concept

and in spite of the future prospects of

high concentration and high efficiencies,

the central receiver technology needs still

more research and development efforts

and demonstration of up-scaled plant

operation to come up to commercial use.



No successful scaled-up central receiver plantsare available for commercial demonstration up tonow, although more than six experimental andpilot demonstration central receiver plants weresuccessfully operated world-wide since 1981.Currently promising technologies (the moltensalt-in-tube receiver technology in USA and thevolumetric air receiver technology in Europe, bothwith energy storage system) are proven only byone pilot demonstration unit (10 MWe SOLARTWO) with two years of operating experience andby one pilot experimental unit (2.5 MWthPHOEBUS-TSA) with some years of operatingexperience.



Not yet verified is the good potentialprojected for the improvement of solarsystem performance and for cost reductions.Not yet verified are projections of theinstalled plant capital costs, operation andmaintenance costs, electricity costs, solarsubsystem performance, operationalcharacteristics and of the annual plantavailability.The industrial demonstration of volumeproduction of heliostat components is stillmissing.


Spain: Two EU funded central receiver projects SOLGAS andColón Solar for European demonstration of hybrid solar towerpower plants (ISCCS) for integration of 20 MW of solarsaturated steam into a conventional combined-cycle powerplant; terminated due to budgetary reasons after the detailedengineering phase in 1998Spain: 10 MWe solar-only power plant project Planta Solar(PS10) at Sanlúcar near Sevilla promoted by Spanish andGerman companies; application of GermanPHOEBUSvolumetric air receiver/energy storage technology; use ofSpanish 90m2 glass-metal heliostats (Figure 6)Spain: 10 MWe solar-only power plant project at Córdobapromoted by Spanish and U.S. companies; application of U. S.molten-salt technologies for receiver and energy storage; useof new Spanish low-cost heliostats with reduced dimensions.




3. Parabolic dish systems: Parabolic dishsystems can reach 1000° C at thereceiver, and achieve the highestefficiencies for converting solar energyto electricity.

Dish systems use parabolic reflectors in the shapeof a dish to focus the sun’s rays onto a dish-mountedreceiver at its focal point. In the receiver a heat-transfer medium takes overthe solar energy and transfers it to the powerconversion system, which may be mounted in oneunit together with the receiver or at the ground.Due to its ideal optical parabolic configuration andits two axes control for tracking the sun, dishcollectors achieve the highest solar fluxconcentration, and therefore the highest performanceof all concentrator types in terms of peak solarconcentration and of system efficiency.

Parabolic Dish Systems



The Vanguard concentrator is approximately 11 meters in diameter and made of 366 mirror facets. The engine used is a United Stirling AB (USAB) Model 4-95 Mark II driving a commercial 480 volt/ac 60-Hz alternator.


California Edison 25 kW dish/Stirling system. The 944 square foot concentrator consists of 82 spherically curved glass mirrors each 3 foot by 4 foot. This engine delivered 25kW output at 1000W/m2 insolation.


The electricity output of singledish/Stirling unit is limited to small ratingsof e. g. 25 kWe due to geometric and physicreasons (exception: Australian big dishdesigned for use of a 50 kWe steam engineor turbine generator).Large-scale deployment has not yetoccurred.No commercial demonstration has beenperformed up to date.



The predicted potential for improvementsof solar system performance and of costreductions is still to be verified.Hybrid systems have inherent low-efficientcombustion and have to be proven.No adequate energy storage system isapplicable or available.The establishment of industrial largevolume production of dish components andStirling engines is needed for entry intoappropriate market segments.


Europe: First ongoing industrial dish/Stirlingdemonstration programme under successfuloperation for proof of continuous operationof six German dish/Stirling pre-commercialunits with 9 to 10 kWe ratings.Spain: Feasibility study and a smalldemonstration project promoted by aSpanish group in collaboration with StirlingEnergy Systems (SES) consortium using a 25kWe Dish/Stirling unit of McDonnell Douglas(MDAC) for erection in the South-east ofSpain.



USA: First industrial series of five 25 kWeU.S. dish/Stirling 2nd generation prototypesystems for extended testing in the South-west USA.

Australia: First 400 m2 pilot experimental“big dish” project with capacity of up to 150kWth under scientific testing at theAustralian National University (ANU).



Comparison of all three Technologies

It has a tall chimney at the center of thefield, which is covered with glass.The solar heat generates hot air in the gapbetween the ground and the gall cover whichis then passed through the central tower to itsupper end due to density difference betweenrelatively cooler air outside the upper end ofthe tower and hotter air inside tower.While traveling up this air drives windturbines located inside the tower.

Solar Chimney Technology



These systems need relatively lesscomponents and were supposed to becheaper.However, low operating efficiency, and needfor a tall tower of height of the order of1000m made this technology a challengingone. A pilot solar chimney project was installedinSpain to test the concept. This 50kW capacityplant was successfully operated between1982 to 1989.



Rural electrification using solar dishcollector technologyTypically these dishes care of 10 to 25 kWcapacity each and use striling engine forpower generation. These can be developed for village leveldistributed generation by hybridizing themwith biomass gasifier for hot air generation.Integration of solar thermal power plantswith existing industries such as paper, dairyor sugar industry, which has cogenerationunits.

Opportunities for solar thermal power generation in India


Integration of solar thermal power

generation unit with existing coal thermal

power plants. The study shows that

savings of upto 24% is possible during

periods of high insolation for feed water

heating to 241 0C


Solar thermal power plants need detailedfeasibility study and technology identificationalong with proper solar radiation resourceassessment.The current status of internationaltechnology and its availability and financialand commercial feasibility in the context ofIndia is not clear.The delays in finalizing technology forMathania plant have created a negativeimpression about the technology.

Barriers


Solar thermal power generation

technology is coming back as commercially

viable technology in many parts of the

world. India needs to take fresh initiative to

assess the latest technology and its

feasibility in the Indian context.

Way ahead


28-Apr-11 57Dr. Bharat M Ramani, ADIT

Documents

Department of Mechanical Engineering A.D.Patel Institute ... · one pilot demonstration unit (10 MWe SOLAR TWO) with two years of operating experience and by one pilot experimental