Performance of the solar hybrid STIG cycle with latent heat storage

The solar hybrid Steam Injection Gas turbine (STIG) cycle uses both recuperated heat and solar heat in order to generate steam at a low temperature and pressure, and inject it into the cycle in order to augment the power output. This work addresses the addition of thermal energy storage to allow operation from solar energy beyond the daylight hours. An annual performance analysis of the Solar STIG cycle with latent heat phase change material (PCM) storage is presented for the climatic conditions of Sede Boqer, Israel. We show that the heat transfer limitation present in a real PCM storage leads to a slight performance penalty only compared to an ideal storage. We also analyze the impact of shifting electricity generation from daytime to evening, which can lead to a surprisingly high contribution of the thermal storage. Results show annual solar fraction of up to 35.2%. The annual solar to electricity efficiency was 20.1% when using the recuperated Brayton cycle as reference, and 13.9% for an optimal conventional STIG cycle as reference. These values are similar to or higher than the annual efficiency of current solar thermal power technologies, even though the hybrid STIG cycle uses low-grade solar heat at 200-280. °C.