The Torrelago district in Laguna de Duero, Valladolid, Spain, has seen a complete retrofitting including renovation of the buildings’ façade and an upgrade to a district heating system which now integrates renewable energy and smart control solutions. This integrated demand and supply approach leads to 50% energy savings in the district.

Torrelago’s district heating is integrated in the CITyFiED project, a smart city demonstration project supported by the European Commission. A new underground biomass boiler room was built, substations were renovated, variable flow pumps were installed and all the devices were connected to an energy management system.

In a truly cooperative approach, CITyFiED representatives carried out workshops with the residents on visualising the district’s renovation. In this way, the project took account of user perspectives and placed residents at the heart of the decision-making process, key for long-term success in green energy projects. Such an approach raises awareness of energy challenges and increases the prospect of replication through citizen engagement.

The project recently won a special award at the 2017 Global District Energy Climate Awards.

The project details

Torrelago is a residential district located in Laguna de Duero, near Valladolid, formed by 31 buildings that respond to three different typologies, containing a total 1,488 dwellings where more than 4,000 residents live. Every building has ground plus twelve floor levels, occupied by an entrance hall and a total of 48 dwellings each with a surface of about 80 m² or 95 m² , which means more than 140,000m² in total.

Before the retrofitting, the district had two different district heating systems, composed by two independent gas-fired boiler rooms. The system was controlled by an analogical system that managed the flow temperature from the boiler and the temperature of storage domestic hot water tank. The heating temperature set point was configured by maintenance personnel according to their experience, the weather conditions and the requirements of the neighbours. Heat flow temperature was usually between 70°C and 80°C.

During the project feasibility stage, it was recommended to transform the previous district heating systems in a more efficient, sustainable and smart one. The main aims were set in reducing energy costs, introducing renewable energy sources and allowing a better control capacity with smart metering.

Introducing biomass

Both district heating systems were joined into one in order to reduce peak periods, make the curve of consumption more homogeneous, and biomass boilers were installed. For those purposes, it was necessary to define the characteristics of the new centralised biomass plant, the distribution network, pumping systems and control equipment, in order to cover heating and domestic hot water needs.

A new building was built to place the biomass boiler room and biomass silo. The underground area occupied by the biomass silo is 72.4 m² and height 5.9 m, with a useful volume of approximately 400 m³. Thermal energy generation is implemented by three renewable energy biomass boilers, two of them of 1,250 kW and one of 950 kW. The boilers have a triple heat exchanger, to achieve maximum heat transfer and efficiency.

Using a digital control system and modulating regulation, boilers reach a performance of 90%.

Key achievements

  • Thanks to the refurbishment in the district heating system, the share of energy savings is increased from 40% to 50%.
  • The system saves 3,392 tCO2/year compared to the initial gas-fired system producing 3,583 tCO2/year (94% CO2 avoided).

Learn more with the following video:  https://youtu.be/BLeTJdeaGdA