Thermoeconomic assessment of a heat pump-enhanced steam and power cogeneration system under design and off-design conditions based on energy level-based exergy cost allocation method

Thermoeconomic analysis is considered a strong tool for cogeneration systems to optimize operation and set prices. In this paper, an absorption-compression heat pump enhanced steam and power cogeneration system is proposed, in which a heat pump is used to upgrade low-temperature waste heat and generate steam. The thermoeconomic performance of the proposed system is investigated under design and off-design conditions using a new thermoeconomic analysis approach with energy level-based cost allocation. As a result, the unit exergy costs of electricity and steam under the design conditions are 2.249 kW/kW and 1.714 kW/kW, respectively. The cost of electricity is higher than that of steam, and this result is opposite to that obtained by a conventional thermoeconomic method (2.063 kW/kW and 2.339 kW/kW, respectively). The costs of electricity and steam increase along with the decreasing engine load under off-design conditions, and the cost of electricity is always higher than that of steam. Finally, the thermoeconomic analysis method with energy level-based cost allocation can obtain more reasonable results and is more suitable for cogeneration systems.