Techno-economic evaluation of different hybridization schemes for a solar thermal/gas power plant

Abstract

Stabilizing the effects of greenhouse gases emissions on the atmosphere is a key step towards solving the global climate change problem. The power industry is one of the major sectors for greenhouse gas emissions. One solution to help reduce emissions from the existing power plants is to hybridize them with renewable energy sources. Solar energy is a leading source among alternative energy sources due to its technological advancement and declining cost in recent years. Concentrated solar power is a mature solar technology that can play a major role in large-scale power production. Hybridizing concentrated solar power plants with natural gas plants can ensure a continuous and reliable power supply in meeting electricity demand. This study investigates the environmental impact and techno-economics of a hybrid natural gas/solar plant with a power production capacity of 140 MW. The system uses a tightly integrated design and a robust control scheme to exploit the synergies between natural gas and solar thermal power. A techno-economic comparison is made between the hybrid plant and two separate plants (solar thermal and natural gas) that are only connected at the grid-level as well as to a stand-alone natural gas plant. Simulation results demonstrate that the solar-to-electric efficiency and solar fraction in a plant-level hybrid unit increase by 77.7 and 69.6%, respectively, when compared to a grid-level hybrid unit. A sensitivity analysis on the plant economics reveals that a value of $146.2/tonne for the carbon tax and a renewable energy credit of 56.94% are required for the plant-level hybrid unit to break-even with the levelized cost of electricity production from the stand-alone natural gas plant. In contrast, the grid-level hybrid unit does not break-even with the levelized cost of electricity production from the natural gas plant within a reasonable range of carbon tax and renewable energy credit. The sensitivity analysis also demonstrates that a carbon tax will be a better leveraging tool to encourage greenhouse gas emissions reductions than the renewable energy credit. A life cycle assessment is also performed for the three systems considered in this work, while using their dynamic models and the relevant control schemes. This study shows that the greenhouse gas emissions in the grid-level hybrid unit and natural gas plant are 9.28% and 23.78%, respectively, higher than the plant-level hybrid unit. Hence, the plant-level hybrid unit emits the least amount of greenhouse gases while demonstrating the maximum synergistic benefits from hybridization.