Cities rely on multiple infrastructures for their daily operation—sewer networks, groundwater drainage systems, metro pumping facilities or, in some cases, secondary water networks. These systems continuously transport or manage water and therefore represent an often-overlooked source of thermal energy.
Aiguaterm explores how existing urban infrastructure can be transformed into a renewable heat source and sink for heat pumps, adding an energy function without compromising its original purpose.
The concept has been demonstrated in València, where the city operates a low-pressure non-potable water network for irrigation, street cleaning and other municipal uses. A full-scale pilot at the Universitat Politècnica de València integrates a reversible 5–22 kW water-to-water heat pump, a plate heat exchanger and two 3,000-litre buffer tanks through a hydraulic bypass.
The system provides heating and cooling to a real university classroom, achieving COP values between 4 and 6, with negligible hydraulic impact (~0.01 bar pressure loss) and no detected deterioration in water quality.
Beyond the pilot, EPANET and GIS analyses assessed 154 km of network, identifying 315 public buildings with potential for connection and demonstrating the urban scalability of the concept.
