District heating and cooling systems for enhanced decarbonisation

The municipality of El Prat de Llobregat maintains a firm commitment to climate action and to advancing the energy transition. This process represents one of the most significant contemporary challenges for any society, as it requires a profound transformation of current energy models, together with a strong and active commitment from both public authorities and citizens.

Under this framework, Aiguasol has developed an alternatives study for the energy system of the Prat Nord / PAU Estació–SEDA–Urgoiti–Paperera district, commissioned by the City Council of El Prat de Llobregat. The objective of the study was to determine the most appropriate climate control solution for this new urban development area, in alignment with the Amendment to the Metropolitan General Urban Plan (MGPM) approved in December 2023.

Our mandate was to assess and compare different renewable-based solutions from a technical, economic, and environmental perspective, and to determine the optimal level of system centralisation — dwelling, building, or district — in order to ensure maximum energy efficiency and long-term sustainability.

A rigorous and sustainability-oriented methodology

The study was structured into four main phases:

• Data collection and calculation of thermal energy demands (heating, cooling, and domestic hot water), based on the building typologies and uses defined in the MGPM, as well as projected climate trends.
• Assessment of available local energy resources and definition of renewable technological alternatives.
• Technical, economic, and environmental evaluation of each scenario.
• Formulation of recommendations and identification of next steps to facilitate implementation. 

The analysis was conducted across different functional scales — building, block, and district — to ensure consistency with the projected urban scale of the development.

Three scenarios, one common objective: maximum efficiency through renewable energy

All solutions were required to be renewable-based and compliant with the Energy Efficiency Directive (SPF ≥ 2.5). Within this framework, three scenarios were defined and characterised:

Scenario 1: Reference solution (Business as Usual)

Individual systems for residential dwellings (direct expansion split units) and centralised aerothermal systems for tertiary buildings. This reflects the current prevailing market approach.

Scenario 2: Building-level centralisation

Centralised air-source heat pumps at building level (residential and tertiary), including internal distribution systems and heat recovery for domestic hot water production.

Scenario 3: District-level centralisation

A four-pipe district heating and cooling network supplied by a central plant equipped with high-efficiency water-to-water heat pumps, located in the vicinity of the Llobregat River.

In this third scenario, a distinctive territorial opportunity was identified: the availability of water resources (groundwater, river water, and reclaimed water). For prudential and regulatory feasibility reasons, calculations were based on the use of groundwater — currently the most administratively viable option — although the proximity of the reclaimed water backbone network opens the door to even more favourable configurations.

Key results

The results are conclusive. While centralised solutions (both building- and district-level) entail a higher initial investment (~€40 million) compared to the reference scenario (~€30 million), this differential is largely offset by:

• Lower operational costs, due to improved system performance.
• Reduced replacement costs, associated with longer system lifespans.
• Significant emissions reductions. 

Specifically, the district-level centralisation scenario achieves:

• A seasonal performance factor (SPF) of 3.86, compared to 3.0 for building-level centralisation and 2.75 for the individual solution.
• Operational costs 60% lower than the reference scenario.
• A 28% reduction in greenhouse gas emissions.
• An aggregate investment saving of approximately €6 million for developers, driven by economies of scale and system optimisation. 

Furthermore, by incorporating projected rooftop photovoltaic generation, the study assesses the energy and environmental balance in coherence with the planned urban development.

Beyond a technical study: a city-level strategy

This study demonstrates that integrating energy planning into the urban planning process is essential for achieving low-carbon, energy-efficient, and economically viable neighbourhoods.

District-level centralisation not only optimises costs and emissions, but also:

• Strengthens energy governance.
• Facilitates renewable energy integration.
• Reduces local environmental impacts.
• Delivers a resilient and scalable infrastructure.

At Aiguasol, we continue to advance the energy transition through real, implementable projects grounded in technical rigour and systemic vision. Prat Nord clearly illustrates that when energy and urban planning are addressed in an integrated manner, the outcomes are significantly enhanced for the territory, developers, and the environment alike.