The project team visited the Odense Heat Network to see a heat network using waste heat from a data centre. From left: Liam Caulfield, senior project manager, and Davena Wilson, director of projects, at OPDC; Asad Kwaja, associate director, and Anthony Riddle, technical director, at Aecom
Two major shifts are under way in the energy sector: the electrification of heat and the rapid growth of artificial intelligence (AI) and cloud computing. The transition to electric heating plays a key role in reducing reliance on fossil fuels, while advances in AI and cloud technology are reshaping how we work, learn and connect.
The vast amount of computer power required by AI has led to rapid growth in the data-centre sector in the UK, while electrification is driving a resurgence in heat networks, which the government recognises as a scalable and efficient solution for decarbonising heat.
The government’s upcoming heat network zoning policy aims to support growth by identifying areas where networks are likely to be the lowest-cost solution to decarbonising heat.
The opportunity
The synergies between data centres and heat networks present a significant opportunity. Every electron of electricity consumed by servers within data centres ultimately converts to heat, most of which is currently wasted and released into the atmosphere.
When you consider that components within a data centre can get up to 85°C, these facilities can be thought of as giant electric boilers. Capturing this wasted heat and integrating it into a heat network can transform this by-product into a valuable resource.
With recovery temperatures ranging from 20°C (air-cooled) to as high as 60°C (liquid-cooled), data centre-connected heat networks can have significantly higher efficiencies than typical low carbon heat solutions, such as air source heat pumps.
Consistent access to low-grade heat is an essential requirement for low carbon networks, which use heat pumps and the refrigeration cycle to ‘move’ heat into more usable forms efficiently.
Data centres are increasingly being recognised as a key contributor to heat network development, with growing momentum in policy and industry. The UK government has recently taken steps to support this opportunity and is funding a heat network in West London that will use a significant amount of waste heat from nearby data centres.
The money from the Green Heat Network Fund (GHNF) is for the Old Oak and Park Royal Development Corporation (OPDC) to develop the Old Oak Park Royal Energy Network (Open)1. Aecom has led the development of Open from its conception through to the appointment of a delivery and funding partner, which are soon to be on board to conclude the commercialisation and construction of the network.
OPDC was established by the Mayor of London to secure the regeneration of the Old Oak Opportunity Area, which spans land in three London boroughs: Ealing, Brent, and Hammersmith & Fulham. The regeneration has been catalysed by the new rail interchange at Old Oak, which will link HS2, Crossrail and the London Underground. Over the next 20 years, 25,500 homes will be built in the area, which also has numerous existing businesses and warehouses, and one of the highest densities of new construction in Europe.
Given its strong transport connectivity, proximity to the City of London and high-fibre connectivity, the area has become a hot spot for data centres, with more in the pipeline. In 2022, West London was subject to significant press coverage because power constraints – brought on partly by the high number of data centres – were said to be blocking new housing development.
The proximity of planned housing to new and existing data centres has created the conditions for the development of Open, which is expected to deliver up to 95GWh of heat per year over five phases between 2028 and 2040. It is the first new-build heat network in the UK to take waste heat from data centres on a large scale, and will recover 17MW of waste heat from two new sites, with the potential to expand and connect several more.
Project development
Aecom started work on Open in 2022 with initial heat mapping masterplanning, which led to the award of GHNF funding in 2023. The consulting firm has since been supporting procurement of the development.
Open is one of the first major pieces of infrastructure being brought forward through OPDC. This has its own challenges in terms of advanced planning and anticipating the needs of a growing urban development.
Future requirements influenced the ‘architecture’ for the network. Two options were assessed in terms of configurations: a 4th-generation and 5th-generation heat network (Figure 1).
The advantages of 5th-generation heat networks include energy sharing, distributing plant, and providing both heating and cooling more locally – whereas 4th-generation networks centralise plant and distribute via a low-temperature network.
A key factor influencing the configuration was the limited space available because of the land’s high development value. Spreading plant across multiple energy centres – distributed energy centres (DECs) – in a 5th-generation heat network would also have added to the risk profile, and put additional requirements on new and existing developers to accommodate heat pumps and their associated power requirements.
When a site local to the new data centres came up for sale, it was decided that this would be the perfect location for a centralised energy centre (EC), and we decided to pursue a 4th-generation heat network to connect buildings in Open. The EC concept design houses centralised 23MW water-to-water heat pumps, peaking plant, and up to 350m3 of thermal storage (to improve resilience and enable partial load shifting).
An ambient loop connects the data centres and the EC. Because of the narrow delta-T between flow and return temperatures of the ambient loop, large-diameter pipes are required to move the 17MW of waste heat. The ground conditions are challenging in this area; with a high density of underground utilities, space is expected to be limited. At these ambient temperatures, heat loss to the surrounding ground is low, so conventional uninsulated plastic pipes can be used, which reduces capital expenditure and embodied carbon. The 4th-generation low temperature hot water (LTHW) network will use pre-insulated pipes, with a circulating flow of 65°C.
Open will potentially supply a major hospital, which requires 80°C during peak demands. A localised water source heat pump has been designed at the hospital energy centre, which will use the 65°C LTHW as the source temperature and increase it to 85°C. This will save the hospital the disruption and cost of extensive building-level upgrades that would be necessary to operate using a 65°C LTHW.
Prior to construction, OPDC is using the existing EC site as a circular economy hub for the community, where local organisations will repurpose local waste materials into new products, such as furniture, tableware and panelling, to be sold back to the community.
In its first phase, Open is planned to recover up to 17MW from two new-build data centres, with the heat captured at around 24°C. The heat-recovery circuit is connected in series on the return of the chilled water loop, acting as a pre-cooler to the data centres’ own plant. The relatively low proportion of heat being supplied compared with the facilities’ total cooling demand means that a near-constant supply of heat can be provided year round.
Technically, the equipment required to facilitate the offtake is not complex – a pair of plate heat exchangers, valves and pumps – and working with a new facility means the requirements can be built in from the outset.
However, a major area of work has been developing the commercial understanding around which party will own, operate and maintain what. Data centres have inherent security and uptime requirements, so making operators comfortable with the expectations of the heat network, in terms of maintenance access and control signals, was a key part of developing the project.
Development of the heat offtake solution has been a collaborative effort between Aecom’s sustainability and data centre teams.
The project has led to several more conversations with data centre developers to ascertain opportunities for heat reuse and share best practice. This has included a team visit to Denmark and the Odense Heat Network, which is served in part by 45MW of heat from a Meta Data Centre.
The growth of data centres is a consequence of increasing global demand for digital services, cloud computing and AI. As these facilities expand, so too does the opportunity to harness their waste heat for a more sustainable built environment.
Integration of waste heat recovery must become a standard consideration.
With supportive policies, investment and collaboration, such projects can play a pivotal role in achieving the UK’s net zero ambitions.
How the Open network could be expanded in the future
The Open network has the opportunity to connect to several existing data centres as it expands and further heat is required for new and existing buildings. However, retrofitting heat offtake can come with challenges.
These modifications are typically bespoke designs, and can be complex and costly to design and develop. Additionally, older facilities may have a number of different cooling systems across the site that have been installed over time and work at different temperatures; this would make the waste-heat offtake solution more complex.
Detailed planning, phased installations and downtime management are necessary, which, again, can add to the cost and complexity.
Specific feasibility assessments will be required – but the opportunity is significant.
- Open is the subject of a presentation by Aecom principal consultant Sam Pepper at the CIBSE IBPSA-England Technical Symposium, UCL London, on 24-25 April: cibse.org/symposium
References:
- ‘Thousands of homes to be kept warm by waste heat from computer data centres in UK first’, Department for Energy Security and Net Zero, bit.ly/CJWH23
