A multi-energy thermochemical hybrid heat and power (CHP) system with two-stage storage is presented and analyzed in this study. The proposed system includes parabolic trough solar collectors, a thermochemical reactor, an internal combustion engine (ICE) and a two-stage storage of thermal energy and chemical energy, which uses solar energy and methanol as input and outputs power and thermal energy. With the two-stage storage, solar energy and exhaust heat are stored as thermal energy in the first stage and further converted into chemical energy in the second stage, which is stored in the syngas tank. Due to the two-stage energy storage, the heat-to-power ratio (HPR) of the proposed system can be adjusted and controlled between 0.67 and 2.02 under rated working conditions. The load match between energy supplier and receiver is improved, reducing additional energy input and energy waste. Compared to the reference CHP system, the fuel saving ratio (FSR) of the proposed system is further improved from 34% to 52% under the design conditions. The methanol decomposition driven by the combination of solar energy and exhaust heat increases the power generation efficiency for methanol fuel. The fuel source conversion reduces the irreversible loss of fuel combustion. Solar thermal energy is upgraded into syngas chemical energy. A high net solar-to-electric efficiency (22.85%) is achieved at a low heat-collecting temperature (538.15 K). This study provides a promising approach for the active regulation of solar-fuel hybrid distributed systems.
Keywords Combined heat and power, solar energy, energy storage, thermochemistry, heat-to-power ratio