Professor George Stavrakakis (www.elci.tuc.gr)Dr Apostolos Apostolou(www.unitech-hellas.gr)

CONCENTRATED SOLAR THERMAL POWER PLANTS (CSPPS)

CSPPs utilize solar thermal power to produce electricityThe power plant cycles applied for CSPPs are mainly based on conventional power plant componentscommercially available today on the 5-200MWe scaleCSPPs use either Parabolic Trough or Solar Tower collection possiblilities

PARABOLIC TROUGH CSPPS

Parabolic mirrors concentrate the sunlight on a line of focus. The solar field is composed of many parallel rows of “trough” collectorsThe rows are positioned in a North-South axis and use single-axis tracking, sufficient for optimal performanceConcentrated solar energy is received on a special oil (Heat Transfer Fluid) running through the absorber tube

Thermal storage solutions can be applied, which can aid the plant (in conjunction with fossil fuel) to operate continuously during intermittent sunshine and some hours after dawn

PARABOLIC TROUGH CSPPS -OPERATION PRINCIPLE

SOLAR TOWER CSPPS

Solar tower fields are composed of several hundred individual, large dual-axis sun tracking flat plane mirrors called heliostats. These heliostats focus the rays on to the solar receiver. The solar receiver is located on the tower at a height of up to 100 m

A HTF, usually molten salt is pumped through the receiver where it is heated to 550°C. The heated fluid can then be used to generate steam to produce electricity.

SOLAR TOWER CSPPS –OPERATION PRINCIPLE

PARABOLIC TROUGH TECHNOLOGICAL EVALUATION

Parabolic trough advantages:Lower environmental and aesthetic impact due to compact designLower space requirements (fixed spacing)Synthetic oil (HTF) preservation heating not required –the plant can operate solar-onlySingle Axis tracking ensures lower installment costs and higher reliabilityMore than 1GWe of existing commercial applications ensure proven viability and expertise

Parabolic trough disadvantages:Lower Solar to Electric efficiencies require more optical elements, increasing project costs

SOLAR TOWER TECHNOLOGICAL EVALUATION

Solar tower advantages:Higher efficiencies (solar to electric energy conversion) due to reduced pumping and higher medium heat capacity (600+ ºC steam generation)Smaller volumes of HTF required, non-linearly related to the size of the plant, resulting in reduced costsTower based heat absorption ensures easy and affordable transitions to future technologies

Solar tower disadvantages:Supportive fossil heating for molten salt is obligatory, increasing O&M costsVery few commercial applications, higher solar field reflections, space requirements

PARABOLIC TROUGH VS SOLAR TOWER COMPARISON FOR A 50MW PLANT

50MW Scale CSPP Parabolic Trough Solar Tower

Estimated plant cost(specific cost)

250 million €(5.000 €/Kwe)

150 million €(3.000 €/Kwe)

Mirror Surface required 510.000 m2 291.000 m2

Solar-only Possible Impossible

Storage Capacity 7 h 0,5 h

Required land area ~ 1.020.000 ~ 1.750.000

Maximum Capacity Factor(at 2.700 kWh/m2) 42% 26%

Future upgradability Low High, up to 1000ºC through changes in receiver and HTF in near future

Reflections and environmental burden None High

GREEK LEGISLATIVE FRAMEWORK

Recent Greek law 3468/2006 for Electrical energy production from Renewable Energy Sources (RES) and Combined Cycle Power Production (CCPP) provides high initiatives for investment in solar thermal power production

Power Plants are defined as Hybrid when more than one source of energy is being utilized. Therefore CSPPs supported by any kind of fossil fuel are considered hybridCSPPs can use fossil derived energy (i.e. LNG) for support of production. The fuel’s total energy content must never succeed the 10% of the totally utilized energy in annual basisSelling price for energy produced by CSPP is set for 2008 at 0.233€/kWh for large scale installments (>5MWe). Even higher prices are given for remote islands

PRELIMINARY FEASIBILITY ANALYSIS ON APOSSIBLE GREEK PROJECT

50MW Scale CSPP Parabolic Trough Solar Tower

Estimated plant cost(specific cost)

250 million €(5.000 €/kWe)

150 million €(3.000 €/kWe)

Estimated Capacity Factor(at 2.332 kWh/m2) 34 – 38 % 19 - 21%

Estimated O&M costs 5 Million € per year 2,2 Million € per year

Net electricity selling price 0.233 €/kWh 0.233 €/kWh

Project Location: Megara, AttikiAnnual levels of direct (2-axis tracking) solar irradiation 2.230 kWh/m2 (ref: PVGIS)Development Law 3299/04 subsidies 30%

PRELIMINARY FEASIBILITY ANALYSIS ON APOSSIBLE GREEK PROJECT

50MW Scale CSPP Parabolic Trough Solar Tower

After tax IRR (20yrs) 16,9 % 17,1%

Year-to-Positive 6,2 yrs 5,9 yrs

Net Present Value (20yrs) 515 Million € 313 Million €

Minimum capacity factors were assumedTax rates of 25% were considered with a 5% annual depreciation factorEnvironmental impacts and land requirements of Solar Tower CSPPs must not be disregardedParabolic trough is the currently considered as the most realistic and financially viable application

PRELIMINARY FEASIBILITY ANALYSIS ON APOSSIBLE GREEK PROJECT

50MW Scale CSPP Parabolic Trough Solar Tower

After tax IRR (20yrs) 16,9 % 17,1%

Total investment for 50MWe 250 million € 150 million €

Land required ~ 1.020.000 ~ 1.750.000

Parabolic trough is more profitable as it offers:Higher capital investment possibility for the same IRR outputHigher capital investment possibility for the same nominal capacity authorization (50MWe)Easier environmental authorization and land acquisition due to smaller area requirements

OTHER INVESTMENT POSSIBILITIES

Up to 200MWe of Hybrid Solar To enhance availability, efficiency and controllability, the solar field may be incorporated into a conventional combined cycle power plant. A hybrid 200MWe Integrated Solar Combined Cycle Plant (ICCPP) produces 25% of its total capacity from solar utilization during peak sunshineUp to 10% of the annually produced electrical energy is sun derived.Law 3468 accepts applications for hybrid plantsSolar-derived electricity is priced separately (0.233 €/kWh) from fossil fuel-derived electricity 0.0758 €/kWh)

POSSIBLE LOCATIONS WITH AVAILABLE AREASAND SUFFICIENT SUNSHINE