Exergy and Economic Evaluation of a Hybrid Power Plant Coupling Coal with Solar Energy

Abstract

Hybrid power plants that couple conventional with renewable energy are promising alternatives to electricity generation with low greenhouse gas emissions. Such plants aim to improve the operational stability of renewable power plants, while at the same time reducing the fuel consumption of conventional fossil fuel power plants. Here, we propose and evaluate the thermodynamic and economic viability of a hybrid plant under different operating conditions, applying exergy and economic analyses. The hybrid plant combines a coal plant with a solar-tower field. The plant is also compared with a conventional coal-fired plant of similar capacity. The results show that the proposed hybrid plant can emit 4.6% less pollutants due to the addition of solar energy. Fuel consumption can also be decreased by the same amount. The exergy efficiency of the hybrid power plant is found to be 35.8%, 1.6 percentage points higher than the efficiency of the conventional coal plant, and the total capital investment needed to build and operate a plant is 8050.32 $/kW. This cost is higher than the necessary capital investment of 5979.69 $/kW to build and operate a coal-fired power plant, and it is mainly due to the higher purchased equipment cost. Finally, the levelized cost of electricity of the hybrid plant is found to be 0.19 $/kWh (using both solar and coal resources) and 0.12 $/kWh when the plant is fueled only with coal.