Hybrid heating systems: bridging the gap in the public sector
Chris Caton, Product Director – Commercial at Ideal Heating, explains the key features and benefits of a hybrid heating system, and how they can help to reduce emissions in public sector buildings.
The Public Sector Decarbonisation Scheme (PSDS) supports the aim of reducing emissions from public sector buildings in England, as well as those with reserved functions operating in the devolved administrations across the UK, by 75% by 2037, compared to a 2017 baseline. Phase 4 of the scheme has a £1.17 billion budget to run from 2025-2028. Similar schemes operate in Wales and Scotland.
The PSDS is a much needed fund for decarbonising the public sector, which includes transitioning to decarbonised heating systems, primarily by replacing natural gas boilers with heat pumps which are up to a third more efficient than gas boilers, so require less energy to run.
Even with the large sums available, many PSDS applicants will fail in their bid to get funding meaning they are unlikely to be able to afford a truly decarbonised heating solution based on renewables and heat pumps. Why? Because the capital cost of heat pumps is more than comparable to gas boilers and, despite their efficiency, running costs are not low due to the price of electricity compared to gas in this country. On the plus side, heat pumps have a long lifespan and have minimal moving parts that need to be replaced or maintained. However, these costs remain a real stumbling block for many.
In such a scenario, a compromise can be achieved that makes considerable steps towards decarbonised heating, but with a more affordable price tag: the hybrid heating system.
Hybrid heating systems explained
A hybrid system essentially has heat pumps as the primary heating system, with gas boilers as the ‘top up’ at times when there is high demand or external temperatures are particularly low.
Cascading wall-hung commercial condensing boilers, such as our Evomax 2 or the floor standing Imax Xtra 2, are ideal for a hybrid system as a higher modulation ratio is achieved, so gas usage is far more efficient. With a large single boiler, it would cycle on and off, using considerably more fuel than strictly necessary. This hybrid approach is receiving a lot of interest from customers and is one of the reasons we designed our ECOMOD heat pumps with the capability to be installed alongside other Ideal Heating solutions.
When it comes to system design and installation, the same principles are followed as with a standard commercial heating system and the boilers and heat pumps have all the connectivity required to interface with the building management system on-site that will need to be programmed to allow for the switch between the systems. That switch from one system to the other could even be based upon energy pricing, so when electricity is too expensive the system switches over to the gas boilers.
Hybrid heating systems: the benefits Hybrid heating systems help bridge the gap between reliance on fossil fuel burning boilers and low carbon heat pumps. It enables public sector bodies who have not been successful with their PSDS funding bid to move towards decarbonisation without the high capital cost. Of course, this also makes hybrid systems suitable for privately owned buildings where cost is a big factor too.
On top of this, meeting the heat load of an older, poorly insulated property can be expensive from a heat pump alone, typically due to the size and fabric of the building. Even in these properties where retrofitting insulation and improving the airtightness of a building is possible, the cost of doing so may be prohibitive. A hybrid heating system provides more affordable running costs and ensures the properties are heated adequately, where a heat pump, with its lower operating temperatures, may struggle.
Hybrid heating in action
As part of its sustainability strategy that embraces responsible energy management, Tinsley Meadows Primary School in Sheffield has taken this hybrid approach. The school has installed two Ideal Heating Commercial ECOMOD 14kW air source heat pumps running in a hydraulic cascade. These have been installed alongside two wall hung Evomax 2 40kW commercial condensing boilers, for a low carbon hybrid heating system, offering lower running costs and comfort all year round.
Chris Snowden, Technical Operations Manager at Service 2, which installed the system, explains the hybrid approach taken at Tinsley Meadows: “The ECOMOD heat pumps have been designed to be the main heating source, backed up by the new gas boilers at times of heavy demand. It means the school always has sufficient heating without relying solely on gas.”
Conclusion
The PSDS is an excellent scheme but, as with seemingly everything in the public sector, there’s simply not enough money to go around and many organisations will be left disappointed when the results of Phase 4 are announced. But decarbonisation aspirations don’t have to end there. By adopting a hybrid heating system approach, public sector bodies can bridge the gap between fossil fuel and decarbonised heating systems without the hefty price tag of the latter.
