Potential evaluation of Carnot battery integrating waste heat recovery in industry

One of the keys to the current energy and ecological transition is the development of electrical energy storage. This demand has motivated the development of alternative technologies that overcome some of the shortcomings of the storage systems used until now. Among these, Carnot battery has experienced a rapid development in the last decade. Its principle is to store electrical energy in the form of heat and restore it with a heat engine. This technology has several advantages: a long life span, the possibility to increase easily its storage capacity, and the use of small environmental footprint materials. Current research tends to show the lack of competitiveness of classical Carnot batteries architectures compared to other technologies due to their relatively low roundtrip electric efficiency. It is therefore necessary to investigate the integration of heat streams in order to increase their attractiveness. A large part of the industrial energy consumption is used for thermal purpose. It is estimated that a large part of this energy is then lost as waste heat. The aim of this paper is to provide economic key performance indicators concerning the potential of a Carnot battery integrating waste heat recovery in a given industry. The key performance indicators provided are based on the temperature level of the waste heat, the energy rates consumed and dissipated by the industry, the type of primary energy used and the electricity pricing. This paper shows that electricity pricing is the key to this technology development. High price variability and negative purchase prices are factors leading to a potentially interesting profitability of this system. The primary energy ratio is the second most important parameter influencing the results. As an illustrative example: an industry with a recoverable waste heat at 100°C, a gas consumption three times higher than the electricity consumption, and a ratio of the minimum (positive) purchase price of electricity to the maximum sale price equal to 50% can expect a maximum reduction in its electricity bill of 25%. This maximum reduction rises to 50% if the the gas consumption is seven times higher than electricity consumption or if the electricity price ratio is 27%.