An efficient and low-cost solar-aided lignite drying power generation system based on cascade utilisation of concentrating and non-concentrating solar energy

Abstract

A new solar-aided power generation system is proposed. It is based on the unique characteristics of non-concentrating and concentrating solar energy applied to lignite drying. In the new system, solar energy cascade utilisation is achieved by the two-stage solar drying of lignite. Solar irradiance, especially diffused irradiance, can be efficiently used in the new system at a relatively low cost using a non-concentrating solar collecting device. High solar energy conversion efficiency is achieved through solar-integrated lignite drying. For a 600-MW base unit, the solar energy in the new system increases electric power by 26.8 MWe; the solar-to-electricity conversion efficiency is 35.83 %. The low-cost non-concentrating solar collecting device has outstanding thermal performance. The net annual revenue of the new system is 63.45 million CNY with a solar-generated electricity cost of 0.346 CNY/kWh. The problem of solar fluctuation is resolved by dried coal storage. The new system achieves significantly better performance than the conventional system by efficiently utilising diffused solar irradiance during cloudy days.