Limited fossil energy resources and the greenhouse gas effect on the environment is creating increasing pressure over the world to look for alternative energy resources that are sustainable and ecofriendly . Solar energy is currently among the popular renewable energy resources due to its recent advancements in technology and economics. However, reliability of energy supply is considered among the major drawbacks for stand-alone solar systems, as solar energy is not available during nighttime and intermittent on cloudy days. Hybridizing solar systems with fossil fuel can resolve the issue of reliability and also reduce the infrastructure cost compared to a pure solar plant . Concentrated solar power (CSP) system are viable for large scale power production . Parabolic trough are widely used CSP technologies as they are easy to finance and their maturity level in the market . Hybridizing solar power plant with natural gas requires minimal capital cost for infrastructure . In this study, we have designed and modeled a hybrid solar and natural gas plant in comparison to a stand-alone solar plant with thermal energy storage. The novel features of the hybrid design include supplemental fuel firing to ensure that high superheat temperatures are always reached in order to ensure a high cycle efficiency and the ability to operate the plant flexibly between solar and fuel modes. Another novel contribution of this work is that the design is complete with a fully dynamic model to capture the effects of rapidly changing solar conditions and an active control system to ensure that plant automation can handle these fluctuations. The hybrid system demonstrates an increase in solar-to-electric efficiency of 15 to 26% when compared to the stand-alone system. The overall efficiency also increases from 15 to 34 % in the same comparison. The hybrid system also demonstrates better environmental performance than a stand-alone system that would otherwise rely on fossil fuel backup generators at grid scale.
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