Assessing the influence of compressor inertia on the dynamic performance of large-scale vapor compression heat pumps for Carnot batteries
(2024) Journal of Energy Storage — Vol. 101 (2024)
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- Abstract
- Carnot batteries, a combination of a power-to-heat, a thermal storage and a heat-to-power system, are an emerging storage technology that could provide a solution to the imbalance of intermittent renewable energy injection into the grid. However, which grid services this technology could deliver remains unclear due to a lack of detailed research on the system dynamics, which makes it difficult to predict, control and optimize its performance in actual operating conditions. As such, also the financial appraisal of the technology remains unclear. This work explores the potential of delivering grid balancing services during the charging phase of a Rankine-based Carnot battery. In this context, the electrical response of the vapor compression heat pump is of interest rather than the thermal response, as it is crucial for integration of the storage system in the electrical grid. Therefore, the dynamic behavior of a 1.5 MWe vapor compression heat pump is addressed. A control strategy driven by the requirements of the electrical grid was implemented and the effect of compressor rotational inertia was taken up into the modelling approach. The prequalification tests for grid balancing services in the central European grid were simulated using models neglecting and considering rotational inertia. While the rotational inertia can be considered negligible for thermodynamic performance predictions, which remain dominated by the thermal capacitances and refrigerant reservoirs in the closed loop, this work shows it is relevant to variable-speed heat pump applications for correct simulation of the electrical response. The heat pump can deliver a capacity of 750 kW for secondary and tertiary reserve in the upward and downward direction, both neglecting and considering rotational inertia. However, its potential to deliver a symmetric primary reserve capacity of 375 kW is identified only when the rotational inertia is included in the modelling. Grid balancing services during the charging phase can thus be additional revenue streams to increase the financial feasibility of Carnot batteries and it is therefore worthwhile to investigate their potential financial benefits. © 2024 Elsevier Ltd
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Citations
Tassenoy, R., Laterre, A., Lemort, V., Contino, F., De Paepe, M., & Lecompte, S. (2024). Assessing the influence of compressor inertia on the dynamic performance of large-scale vapor compression heat pumps for Carnot batteries. Journal of Energy Storage, 101. https://doi.org/10.1016/j.est.2024.113948 (Original work published 2024)