Reiner Buck, Peter Heller, Peter Schwarzbozl, Deutsches Zentrum fur Luft — und Raumfahrt (DLR), Institute of Technical Thermodynamics, Pfaffenwaldring 38-40, D-70569 Stuttgart, Germany

Chemi Sugarmen, Arik Ring, Research & Development Department, ORMAT Industries Ltd., Industrial Area, POB 68 Yavne 81100, Israel

Felix Tellez, Renewable Energy Department, CIEMAT, Avda. Complutense 22, E-28040 Madrid, Spain

Juan Enrile, SOLUCAR, Avda. de la Buhaira, 2, E-41018 Sevilla, Spain

The integration of solar energy into gas turbine power systems can lead to lower cost for solar power production. The paper describes the status and perspective of solar-hybrid gas turbine systems. A solar-hybrid test system was set-up consisting of a pressurized solar receiver cluster and a modified helicopter gas turbine with a generator. The test system was operated up to receiver temperatures of 960°C, delivering up to 230 kWe to the grid. Controlability of the hybrid system was very good.

Design and performance assessment of prototype plant configurations in the power levels from 4 MWe to 16 MWe are presented. Expected cost figures for the solarized gas turbine, the solar tower plant and further equipment as well as for operation and maintenance are discussed. Levelized electricity costs of about 13 €cent/kWh with an annual solar share of 53% are calculated for a 16 MWe combined cycle. The perspective for market introduction is outlined.

Introduction

The reduction of fossil-fuel based power production by using solar power technology is one important step in the international commitment of CO2 reduction. The direct way of producing electric power from solar energy, the photovoltaic technology (PV), is gradually extending its focus from purely decentralized small scale systems towards large-area bulk power production. Generating costs of solar electricity below 10 €cent/kWh are predicted for 2010. In contrast, solar thermal power plants produce high temperature heat that is converted to electricity by conventional power cycles. The nine commercial parabolic trough plants in the Californian dessert (SEGS) produce electricity from solar energy with an overall efficiency of 10-14% and at levelized electricity costs of 16-19 €cent/kWh.

Future large systems of 200 MW with 12h storage are forecasted with system costs of 2500 €/kW and generating costs below 5 €cent/kWh [1]. Similar projections are made for other solar-only technologies. In any case, the key to cost reduction lies in mass production after successful market penetration.

One major option for an accelerated market introduction of solar thermal power technology are solar-fossil hybrid power plants. Their advantage compared to solar-only systems lies in low investments due to an adaptable solar share, reduced technical and economical risks due to a fully dispatchable power, and a higher system efficiency because of reduced part load operation and less start-up and shut-down losses. Another important aspect is that for renewable power generation technologies like wind turbines and PV a conventional power capacity has to be kept in stand-by to compensate the fluctuating power supply of renewable energies. This is a kind of renewable-conventional hybrid power system but with completely separated system technologies. Real hybrid plants share great parts of their system, hence leading to economical advantages.

Using the high conversion efficiencies of Combined Cycle systems (now above 50%) or recuperated gas turbines leads to a decrease in the required heliostat area. As the heliostat field is the major cost contribution in solar tower plants, this results in a cost reduction.

In this paper the current status of the technology for solar-hybrid gas turbine systems is discussed, including their market perspective.