At the current status of the development of solar-hybrid gas turbine systems with pressurized volumetric receivers the main issues for further R&D are the verification of O&M assumptions for the receiver and the power conversion subsystem, further increase of the solar share and further cost reduction of the solar components.

Continuation of the 240 kWe solar-hybrid test operation at the PSA is foreseen until summer 2004 with a receiver for air outlet temperatures up to 1100°C. Another future option is the inclusion of high temperature heat storage systems, also leading to an increased solar share.

Although the cost predictions indicate potential competitive applications in the green power market, the introduction of this new technology is hampered by several factors:

Power production cost are still higher than with conventional fossil fuel options.

Up to now, only few possibilities exist for the funding of hybrid systems with fossil contributions above 30% (solar shares <70%).

Exploiting the full potential of high efficiencies of combined cycle plants (>50%) requires power levels above 50 MWe; this means very high investment cost which is not realistic for the introduction of a new technology. Therefore it is clear that market introduction is mainly possible at lower power levels, with the option for future scale-up. At power levels below 10 MWe, gas turbine systems are mainly used for decentralized power generation with cogeneration of heat or cooling power. First cost assessments for such cogeneration units indicated a potential for solar-hybrid gas turbine units [4]. Therefore the first step towards market introduction will be the design and installation of a prototype plant based on a small gas turbine or microturbine in cogeneration mode. Later upscaling will be done to power plants with combined cycle for high efficiency.

Conclusions

The cost-optimized design and performance prediction of solar-hybrid gas turbine plants in the power levels 1.4 MWe, 4.2 MWe and 16.1 MWe for two different locations were shown. An annual mean solar to net electric efficiency of up to 19% was calculated, belonging to the highest conversion efficiencies of solar electric technologies. The cost analysis showed total plant investment costs down to below 1500 €/kW for 2nd generation plants. Solar LEC of 12.8 €cent/kWh at a solar share of 53% are calculated for the largest system in daytime operation (capacity factor 54%). Going to higher power levels will further decrease the specific investment and O&M costs and increase the thermal efficiency. This will lead to a further reduction of solar LEC down to values predicted for other technologies.

The path to enter the market of high power level combined cycles was described. It is foreseen to start after successful long term testing with small scale applications in distributed markets using cogeneration units.

References

[1] Price H., Lupfert E., Kearney D., Zarza E., Cohen G., Gee R. and Mahoney R. (2002): Advances in Parabolic Trough Solar Power Technology. Journal of Solar Energy Engineering, Vol. 124, pp. 109-125.

[2] Buck R., Lupfert E. and Tellez F. (2000): Receiver for Solar-Hybrid Gas Turbine and CC Systems (Refos). IEA Solar Thermal 2000 Conference. March 8-10, 2000, Sydney, Australia.

[3] Heller P., Pfander M., Denk T., Tellez F. and Ring A. (2004): Test and Evaluation of a Solarized Gas Turbine System. Proc. 12th SolarPACES International Symposium, Mexico 2004 (to be published)

[4] Sugarmen C., Ring A., Buck R., Heller P., Schwarzbozl P., Tellez F., Marcos M. J. and Enrile J. (2003): Solar-Hybrid Gas Turbine Power Plants — Test Results and Market Perspektives. Proc. ISES Solar World Congress 2003, June 14-19, 2003, Goteborg, Sweden.

[5] Buck R., Brauning T., Denk T., Pfander M., Schwarzbozl P., Tellez F., Solar-Hybrid Gas Turbine-Based Power Tower Systems (REFOS). J. Solar Energy Engineering, 124, 2-9 2002

[6] Schwarzbozl P., Schmitz M., Pitz-Paal R. and Buck R. (2002): Analysis of Solar Gas Turbine Systems with Pressurized Air Receviers (Refos). Proc. 1lth SolarPACES International Symposium on Concentrated Solar Power and Chemical Energy Technologies, September 4-6, 2002, Zurich, Switzerland

[7] Pitz-Paal R., Jones S. (1998): A TRNSYS Model Library for Solar Thermal Electric Components (STEC). SolarPACES Technical Report No. 111 -4/98. Koln, Germany, 1998

[8] TRNSYS STEC web page: http://sel. me. wisc. edu/trnsys/trnlib/stec/stec. htm

[9] Schwarzbozl P., Buck R., Sugarmen C., Ring A., Marcos M. J., Altwegg P., Enrile J. (2004): Solar Gas Turbine Systems: Design, Cost and Perspectives. Proc. 12th SolarPACES International Symposium Mexico 2004 (to be published)