Adsorption Cooling with Biochar Thermochemical Storage: Integration Strategy for District Heating
The integration of thermochemical storage with adsorption chillers offers a promising solution to decouple heat generation from cooling demand, enhancing the flexibility and efficiency of thermal energy systems. The solution developed within the European CharCool project is based on high-density, rechargeable thermopiles made of biochar plates, an agricultural by-product, impregnated with widely available and environmentally friendly inorganic salts. These thermopiles function both as adsorbent beds and mid-term thermal energy storage media. The thermopile is coupled with a compact, low-cost adsorption chiller using pure water as refrigerant, offering reduced system volume and environmental footprint. These systems can potentially be integrated into district heating networks to provide on-demand cooling services. This study investigates the integration of this system with district heating to supply the cooling demand of multi-apartment residential building. A model was developed to evaluate the system performance in terms of operating cost, CO2 emissions, and Levelized Cost of Cooling (LCOC). The analysis considers the influence of both economic and technical parameters, including heat cost, transport distance, thermopile volume, and district heating emission factor. A sensitivity analysis was carried out using Partial Rank Correlation Coefficient, Standardized Rank Regression Coefficient, and Sobol indices to identify the parameters with the greatest impact on system performance, followed by a comparative assessment against a vapor compression chiller. The results show that the CharCool system can achieve competitive operating costs and emissions in configurations combining large thermopile volumes with low-cost, low-emission district heating sources, supporting its potential as a flexible and sustainable alternative for future district energy applications.