Thermodynamic analysis of heat driven Combined Cooling Heating and Power system (CCHP) with energy storage for long distance transmission

The instability and intermittency feature of low grade heat sources and renewable energy brought about utilization problems, and in most cases, energy source site locates far away from energy demand site, how to implement long distance transmission of energy has been a challenge. To solve above problems, a novel combined power, cooling with solution energy storage and long distance heating/cooling system without heat preservation is proposed. The system integrates Kalina cycle with solution energy storage cycle, which is based on concentration difference of ammonia-strong, ammonia-weak solutions and liquid ammonia, and capable of changing operation modes flexibly according to heat sources and client needs. An analytical model is established and exergy destruction analysis is conducted to indicate exergy losses distribution of components. After optimization of proposed system, exergy efficiency is 0.57, and maximum solution energy storage density reaches 523 MJ/m3. Furthermore, thermal energy is storaged in the form of latent heat, and the working fluids are transported under ambient temperature, therefore, thermal insulation are unnecessary, the maximum heat supply distance is 143 km, 15.7 times that of typical hot water transmission system, and pipe diameter is reduced to 3/20, pump work consumption and construction costs can be reduced dramatically as a consequence.