Synergistic Solar Hybrids

Thoughtful, integrated plant designs can combine the benefits of each energy source. Rather than combining renewable and conventional energy at the grid level, combining them at the plant level allows the two energy sources to share equipment, which can reduce overall capital costs. Hybridization with a combustible fuel allows solar thermal power to achieve higher temperatures and more efficient power cycles, while mitigating heat losses in the solar field. A dispatchable energy source also creates operational flexibility, which can be leveraged with online optimization techniques to enhance the plant’s operation. Finally, low-cost thermal energy storage allows the plant to be optimized over a time horizon, rather than at a single point in time.

In this work, these principles are demonstrated in two different solar and natural gas hybrid plants: one that uses parabolic trough technology combined with a conventional Rankine cycle power plant and one that uses central tower solar receiver combined with a conventional Brayton cycle. In each case, the plant design utilizes natural gas to enhance the plant’s reliability through use of a dispatchable fuel and to increase its efficiency through elevated heat delivery temperatures. Each of these designs achieves a higher solar-to-electric efficiency than a stand-alone solar plant, indicating that there are synergies to be gained by hybridization.