Gas Turbine/Solar Parabolic Trough Hybrid Designs

Abstract

A strength of parabolic trough concentrating solar power (CSP) plants is the ability to provide reliable power by incorporating either thermal energy storage or backup heat from fossil fuels. Yet these benefits have not been fully realized because thermal energy storage remains expensive at trough operating temperatures and gas usage in CSP plants is less efficient than in dedicated combined cycle plants. For example, while a modern combined cycle plant can achieve an overall efficiency in excess of 55%; auxiliary heaters in a parabolic trough plant convert gas to electricity at below 40%. Thus, one can argue the more effective use of natural gas is in a combined cycle plant, not as backup to a CSP plant. Integrated solar combined cycle (ISCC) systems avoid this pitfall by injecting solar steam into the fossil power cycle; however, these designs are limited to about 10% total solar enhancement. Without reliable, cost-effective energy storage or backup power, renewable sources will struggle to achieve a high penetration in the electric grid. This paper describes a novel gas turbine / parabolic trough hybrid design that combines solar contribution of 57% and higher with gas heat rates that rival that for combined cycle natural gas plants. The design integrates proven solar and fossil technologies, thereby offering high reliability and low financial risk while promoting deployment of solar thermal power.

Technical and Environmental Analysis of Parabolic Trough Concentrating Solar Power (CSP) Technologies

“…The AGT stops when the TES system nears full capacity to maximize the efficiency of the process. This configuration may facilitate the use of molten salts as HTF because the exhaust heat from the gas turbine provides sufficient energy to maintain the salt at a temperature above its freezing point during the night [18]. The auxiliary fuel may be of a fossil (natural gas) or renewable nature (biogas, biomethane, or syngas produced from the thermochemical gasification of solid biomass).…”

“…The flexibility of the AGT allows for multiple hybrid configurations with parabolic trough CSP, some of which have been analyzed by Turchi and Ma [18,19]. AGT have a low mass compared to standard gas turbines, which allows them to heat up to nominal values of operation in a very short time (less than 10 min from cold to full load and less than 4 min from stand by to full load).…”

Thermodynamic evaluation of solar integration into a natural gas combined cycle power plant

“…When an NGCC plant is integrated with solar through an HRSG, a certain amount of feed water or steam will be extracted from the HRSG, heated by the solar energy from the solar field and routed back to the HRSG. When solar collectors can directly accept water/steam, the feed water or steam from the NGCC can be heated directly in the solar field; when a heat transfer fluid (HTF) different from water/steam is running in the solar collectors, a heat exchanger will be added between the hot HTF from the solar field and the feed water/steam from the NGCC plant [16].…”

Energy, Transportation and Global Warming

“…In terms of the combined usage of natural gas and concentrated solar thermal energy in one power plant the most common solution is the ISCC (Integrated Solar Combined Cycle). Due to technical reasons the amount of integrable solar energy is strongly limited, for instance the annual solar share is relatively low at 2-8 % (Turchi et al 2011). An alternative approach is to integrate smaller gas turbines, like industrial or aeroderivative gas turbines, into a CSP plant.…”

“…A fairer performance ratio and a comparatively lower natural gas usage are achievable, for what reason this idea is increasingly studied in the last years (e.g. Turchi et al 2011;Vogel et al 2013;Servert et al 2014). …”