(554b) Optimal Design and Planning of Renewable Combined Cooling Heating and Power Systems

Nowadays, urban cities are facing enormous challenges in meeting their energy demands due to the increasing anthropogenic activities¹. Globally, urban cities consume more than 70% of fossil energy in the form of cooling, heating, and power and contribute to over 60% of CO₂ emissions². CO₂ emissions have been considered as the main cause of global warming. To keep the global average temperature rise to well below 2 ºC above pre-industrial levels, it is of necessity to improve energy utilization efficiency and deploy renewable energy resources for urban cities³. Combined cooling, heating, and power (CCHP) systems represent a promising paradigm, since they can increase energy efficiency by cascade energy utilization and reduce carbon emissions via substituting fossil fuels with renewables. However, designing renewable CCHP systems and managing their long-term planning are challenging, since there exists complex interactions among system design, operation, and user demands.

This work first develops a new mixed-integer linear programming (MILP) model for simultaneous design and operation optimization of a renewable CCHP system, considering equipment nonlinear operating characteristics and performance degradation with time. The linearized formulations are derived by linearizing the nonlinear terms comprising equipment operating characteristics and load variation and thus can accurately capture equipment performance and significantly reduce computational burden. A multi-objective optimization is performed to achieve a trade-off between two economic and environmental objectives. The impacts of equipment performance degradation and capital price are also analyzed. The MILP model is then extended to study the economic planning of a renewable CCHP system considering energy storage and demand response. The planning horizon is divided into several planning windows, in each of which investment decisions can be made for better matching the increasing user demands. Four scenarios are considered to quantify the impacts of energy storage and demand response on CCHP long-term planning.

The results show that the optimal renewable CCHP system has a total annual cost of 1.98 million USD/y and carbon emissions of 942.4 ton/y, respectively. In comparison with conventional cost minimization, the renewable CCHP system features a tardy increase of 12.8% in total annual cost and a sharp reduction of 75.5% in carbon emissions. Moreover, ignoring performance degradation leads to an over-estimation of 2.3-13.7% in system economic performance, and photovoltaic and battery are found to be the most impactful technologies on CCHP economic performance. Finally, it is found that considering energy storage and demand response significantly improve CCHP economic performance. Integrating energy storage systems and implementing demand response program reduce CCHP total cost by 4.54 and 8.38 million USD, respectively, in a planning horizon of 15 years, and combining them further augments economic benefit, as total cost reduction reaches 10.48 million USD.

References

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2. Comodi, G., Bartolini, A., Carducci, F., Nagaranjan, B., Romagnoli, A. Achieving low carbon local energy communities in hot climates by exploiting networks synergies in multi energy systems. Applied Energy 256, 113901 (2019).
3. The Paris Agreement | UNFCCC. https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-ag....