Heat networks: a fast-advancing low-carbon technology

Heat networks hit the headlines late last year when news broke of plans to create a system in Westminster to heat 1,000 buildings in Central London, including the National Gallery and Houses of Parliament. The proposed heat network would be the UK’s largest and could be powered by recovered waste heat from a local sewer system, the River Thames and the London Underground.

Such networks are common in continental Europe but largescale networks in the UK are usually limited to estate use on hospitals, educational campuses, cultural collections and horticulture. According to the Department for Energy Security and Net Zero, just 3% of the UK heat needs are currently met by heat networks, but projects like the Westminster scheme could see that grow to 20% by 2050.

While the energy efficiency and low-carbon nature of heat networks are partly the reason to expect growth, changes in technology are also making them more attractive in the UK.

Conventional heat networks rely on steam or high-temperature hot water to meet the needs of multiple buildings. However, heating in the UK has often been an isolated affair with each building containing its own plant and equipment solely to meet the needs of its occupants and processes. While heat might be circulated around the building itself, it is not expected that this heat will be distributed much further afield. Under this approach, each building must find a way of meeting its individual net-zero carbon needs based on the constraints and opportunities available.

By overcoming this cultural norm of considering buildings in silo, multiple building owners could use heat networks to make schemes more viable and gain greater carbon savings as a collective. When this is combined with recent innovations that mean lower temperature solutions, such as heat pumps, can offer the same benefits as conventional heat networks, a wider range of applications is now possible. Additionally, the building sector’s improved analytical skills and understanding of energy conservation contribute further to this expanded potential.

The advance in technology means that several heat sources can be used in combination with other heat sources, offering viability thanks to the new generation systems running at lower operating temperatures. Other enhancements come from better heat retention and control and plant efficiency improvements which considerably reduce the costs associated with operation.

Advances in building management systems mean that split plant rooms can be used to take advantage of the opportunities that different areas of a heat network can provide. For example, air-source heat pumps on a roof of one building can be supported using a water-source heat pump system housed in another nearby building and both can benefit from their operation.

The government is keen to see greater uptake of heat networks in the UK and is currently trying to learn lessons from, and deliver improvements to, existing systems through its £77m Heat Network Efficiency Scheme. The scheme is a key part of the government’s Heat Network Transformation Programme, which is also supporting industry and local authorities to develop new heat networks.

As part of this drive, Mott MacDonald has supported the Scottish government in a technical adviser role to develop a largescale ambient loop heat network for the Advanced Manufacturing Innovation District Scotland (AMIDS).

The 52 ha manufacturing and life sciences campus presented a great opportunity as a demonstrator project due to its range of building typologies, including industrial spaces. The ambient loop system, which operates at a significantly lower temperature than traditional communal systems, successfully demonstrated the potential to apply the technology to other similar developments.

The system provides a future-proofed energy strategy for AMIDS that makes use of waste heat from a nearby wastewater treatment, providing a low-carbon solution for heating and cooling of the buildings at the site. The system aims to deliver carbon emissions reductions of around 57% compared with the previous systems, equating to year-one CO2 savings of 600 tonnes.

While the government recognises heat networks as the lowest-cost and lowest-carbon heating option in densely populated areas when it comes to operation, investment in the underlying infrastructure to unlock this benefit can be high. Several models could be used to spread the cost of investment across multiple partners, such as an energy services company or a multi-organisation special purpose vehicle.

Historically, the initial investment payback and inability for properties within the network to change suppliers as they could with conventional gas or electricity supply has led to concerns about overcharging. However, later this year energy regulator Ofgem will start to oversee the heat network market, creating greater confidence and security for those supplied by such systems.

With all the agreements in place, there is still the challenge of installing the distribution infrastructure. Returning to the Westminster example, the possible disruption its development may bring to central London demonstrates the obstacles such projects will face. However, with a renewed focus on leveraging all available zero-carbon energy sources and meeting the UK’s targets, there is significant pressure on all parties to find solutions to these issues and maximise the potential of such schemes.

Jonathon Monkcom is divisional net-zero carbon lead at Mott MacDonald.