The City of Madrid

Madrid is the capital of the Community of Madrid and Spain. It is the largest city in the country with 3.2 million inhabitants, although if we include the population of the Madrid metropolitan area, it reaches 6.3 million. Madrid is the 5th most important leading centre of commerce in Europe.



The Madrid demonstrator is a hospital building. It was chosen because it is a very common urban tertiary building with local district heating and cooling infrastructure and has great replication potential. Southern European hospitals have high cooling needs during the whole year and, in addition, these kinds of buildings have in general a high thermal energy demand. During winter periods, cooling is needed e.g. for surgery rooms and other areas with special air conditions, while during summer, most of the hospital areas need to be cooled. Furthermore, heating demands are high, not only for space heating in winter periods, but also for domestic hot water production as well as for process heat (e.g. sterilization and cleaning) during the whole year.

The hospital that was chosen to demonstrate ReUseHeat’s innovative solutions is the Hospital Universitario Severo Ochoa, in Madrid. It is situated in the municipality of Leganés and it is a public university hospital that offers a variety of medical services to Madrid citizens. The Hospital is connected to a local heating network, supplying all the buildings with heating and cooling.

Severo Ochoa Hospital Facility building

The Hospital currently has a local network to supply all the buildings with heating and cooling. The central heating and cooling production system is formed by:

  • Heating plant: 3 natural gas boilers, 3*1.85 MW that started to work in April 2019, substituting 3 diesel boilers
  • Cooling plant: 4 water-water electric chillers, 4*1.14 MW capacity
  • Cooling towers: 3 x 2 MW capacity.

The distribution system is formed by the primary and secondary pipelines, that distribute hot and cold water through the building complex.



The objective is to demonstrate an advanced solution based on heat recovery from a cooling production process. As explained above, cooling is vital for hospitals, e.g. in surgery rooms, so it is necessary during the whole year. Hence, electric chillers are used for cooling purposes that dissipate the excess heat either to an air, ground or water source. Usually, this heat is “wasted” and released to the environment; or if recovered, it normally only meets temperature demands for hot water. However, with a booster heat pump, this heat can be recovered and upgraded to a suitable temperature level that can be used for heating in a building or a district heating network, ensuring significant primary energy savings and CO2 emissions reductions.

The demonstrator will recover low temperature heat from the cooling circuit of the water-water electric chillers. Currently, this heat is dissipated through the cooling towers. The booster heat pump will capture the heat from the outlet water of the chiller cooling circuit and upgrade it in order to supply it to the district heating system. By using the booster heat pump, the water from the chillers’ cooling circuit is cooled, minimising the usage of the cooling towers.

A new advanced control system will be installed to improve the operation of the heating production system. In order to optimise efficiency and energy savings, parameters such as temperatures in the chillers’ cooling circuit and district heating network, boiler efficiencies and energy prices will be taken into account. The advanced control system will be especially important during the summer period because the cooling demand is high and the heating demand is low. In this period, most of the savings will be obtained. In addition, in autumn, spring and winter it will be possible to increase efficiencies by operating the booster heat pump with a consumption control, lowering the pressure on natural gas boilers.


The figure below shows a comparison between the ReUseHeat solution and the current situation:

Booster heat pump for waste heat recovery from hospital, concept (Madrid).


More information on heat recovery from tertiary buildings