Carnot batteries for integrated heat and power management in residential applications: A techno-economic analysis

The growing use of photovoltaic (PV) energy in residential systems presents challenges, notably managing daily and seasonal intermittency. To limit curtailment and maximise self-consumption, decentralised flexibility options are crucial. In this context, Carnot batteries, which combine a heat pump, thermal energy storage, and a heat engine, show promise for integrated heat and power management alongside PV production. However, the economic model (investment costs, electricity pricing system) and control strategy (heat/electricity discharge, seasonal impacts) needed to achieve maximum cost-effectiveness have not yet been identified. This study therefore explores the integration of a Carnot battery in a housing development of 20 dwellings equipped with PV systems. Using a quadratically constrained linear programming model, the designs and operations that minimise the annualised energy cost are identified across different ranges of investment costs. The impact of climatic conditions is assessed by comparing results from Pisa and Brussels. Our findings indicate that, except in scenarios with prohibitively high costs, incorporating a heat engine alongside a heat pump and thermal energy storage is the most cost-effective solution. Parametric analyses reveal that zero feed-in tariffs promote Carnot battery deployment, while non-zero tariffs significantly reduce the installed capacity. Additionally, dynamic (or variable) tariffs generally do not reduce energy costs but do increase the Carnot battery capacity, in order to take advantage of the energy arbitrage mechanism. In conclusion, when heat pumps and thermal storage are necessary to meet heating demand, adding a heat engine to address electricity needs is financially effective. This paves the way for further advancements in residential energy management using Carnot batteries. Future work should confirm and refine these results with more precise models, incorporating non-linearities such as start-up and part-load operations.