Salt, waste heat, and a sports centre in Toulouse, that is the combination that enabled Water Horizon and its Move Heat To Cold (MH2C) technology to win the second SET Alliance Efficiency-as-a-Service Innovation Showcase Awards.
Somewhere between an incinerator and an ice rink, separated by 15 kilometres and the width of the Garonne River, quietly lies one of the most remarkable energy solutions operating in Europe today.
Every year, industrial processes and energy generation across France produce an estimated 118 TWh of waste heat – the equivalent of a quarter of the country’s total electricity consumption – most of which simply dissipates into the atmosphere. While this wasted energy has been identified for a long time, and occasionally used to supply neighbouring buildings and infrastructures through district heating, the challenge has been to develop a solution for more distant premises, for buildings with no physical connection to where the thermal energy is produced.
This is what Water Horizon, a French cleantech company based in Toulouse, created, with the additional possibility of converting it to cooling: using the thermochemical properties of salt as the basis for a mobile battery system, the company captures waste heat at its source, stores it, and transports it to customer sites where it can be converted into heating or cooling on demand. The solution does not require any pipes running across the city, nor any upfront infrastructure investment for the end customer. The energy is delivered as a service, charged per unit of use.
In Toulouse, that means a sports and leisure centre hosting both a swimming pool and an ice rink can now meet its year-round heating and cooling needs via an as-a-service contract, using heat that would otherwise have been lost from a nearby incinerator. Water Horizon retains ownership of its battery infrastructure and charges customers a fixed rate per MWh, making the solution financially accessible to facilities that could not otherwise justify the capital outlay.
The results, in terms of both energy performance and emissions avoided, are significant.
The project was selected as the winner of the SET Alliance’s 2025 Efficiency-as-a-Service Innovation Showcase Award, recognising its contribution to advancing service-based models for sustainable energy in Europe by applying the Cooling-as-a-Service model to a unique, innovative technology.
