Efficient distributed concentrating solar power system with ammonia-based chemical heat pump

Abstract

Recently, distributed renewable energy system has become a flexible, reliable and environmentally friendly alternative to the conventional large-scale centralized power plant. This paper proposed a distributed concentrating solar power system coupled with an ammonia-based chemical heat pump. The proposed system is able to upgrade the solar thermal energy absorbed from 450 °C to 650 °C. To design a concentrated solar module, consisting of a Linear Fresnel Reflector field and a Compound Parabolic Collector, for the proposed system, a three-dimensional optical model is developed with SolTrace software. Moreover, the optical model has been validated by comparing the model predicted results with the data from the reference. As for the ammonia decomposition membrane reactor in the system, a three-dimensional reactor model is developed with COMSOL software, which is capable of simulating both ammonia decomposition and hydrogen permeation processes under solar irradiation. With an experimental prototype of the membrane reactor, experiments have been conducted to validate the reactor model. With the validated model, the effects of the reactor length, reactor inlet temperature and ammonia flow rate on the thermochemical conversion efficiency of the reactor have been investigated parametrically. The results show that the reaction conversion increases with the reactor length increasing, while thermochemical conversion efficiency decreases. The thermochemical conversion efficiency increases with reactor inlet temperature and/or ammonia flow rate increasing, which reaches the maximum of 34.9 % in our study. By integrating an ultra-supercritical double reheat power cycle, the system with a low concentration ratio of ∼ 24 can achieve a high solar to power efficiency of ∼ 18.3 %, which surpasses the peak efficiency of a typical concentrating solar power plant with a concentration ratio of ∼ 30.