There is a huge untapped potential of waste heat across the world, reflected in very low utilisation levels. According to the International Energy Agency (2012), only 5.0 PJ, from a total primary energy supply of 10.0 EJ, was recovered as usable heat during the year 2010.

The main sources of waste heat in Europe based on their total potential have been assessed by the Stratego project (2014) in a background report. This report covered large scale (> 50 MW) thermal power generation fuel combustion plants, fuel supply and refineries, waste to energy, and industrial facilities within six significant energy-intensive industrial sectors (chemical and petrochemical, iron and steel, non-ferrous metals, non-metallic minerals, paper, pulp and printing, and the food and beverage sector). The research resulted in a detailed map of EU28 waste heat facilities by main activity sectors and by annual waste heat volumes.

Waste heat from thermal power generation is, at current, by far the richest source that can be exploited – approximately 70% of all available waste heat originates in main activity and auto-producer power plants. The shares for waste to energy and industrial waste heat out of total volumes are 4% and 26% respectively.

Among industrial main activity sectors, fuel supply and refineries represent the highest annual waste heat availabilities (9% of the total waste heat volume and 36% of total industrial sectors volumes), while non-metallic minerals facilities account for 5% of the total waste heat volume and 20% of total industrial sectors volumes.

Although more difficult to quantify and not yet covered by existing research, a large amount of waste heat is also available at urban level from different sources. Such heat sources are low enthalpy sources (around 20-40°C) and available in all cities. Due to their proximity to end-users, they could be effectively exploited to provide heating and cooling both through individual systems as well as district heating and cooling networks.

The ReUseHeat project chose to focus on four key urban facilities sources: data centres, waste water management, underground stations and tertiary buildings (such as hospitals).