Why hybrid heating systems are better than heat pumps for district heating schemes

Pete Mills, Commercial Technical Operations Manager at Bosch Commercial & Industrial, outlines why a hybrid heating system is a better option than a full heat pump for district heating schemes

District heating, otherwise known as heat networks, are fast-becoming the ‘go to’ option for many local authorities, housing associations and developers thanks to their strong credentials of providing heat and hot water in a high-efficiency, low carbon way.

As the UK moves towards a Net Zero future, the role of district heating will no doubt become more prominent. Many believe that heat pumps could and should be the sole heat source for heat network projects, particularly as we see the decline of CHP use. However, this may actually limit a heat network’s potential.

Not just because heat pumps are not at their most efficient during the colder months, but also as it restricts the possibility of future, net low carbon fuels. There are alternatives which ensure district heating schemes have the best of both worlds.

An integrated approach

In our view, a future-proof solution is a hybrid between heat pumps and peak-load boilers. These could deliver savings on both carbon emissions and capital costs.

Hybrid solutions between heat pumps and peak load boilers offer a practical option to keeping capital costs under control, while still delivering significant carbon savings.

Experience has shown that with around 40% to 60% of peak demand covered by heat pumps, over 80% of the kW’s can typically be provided through heat pumps. Heat networks typically operate below 25% of their peak demand for over half of the year, which is well suited to a heat pump. On the small number of days each year when temperatures are coldest, demand can be taken up by the peak-load boilers.

This makes even more sense where air source heat pumps are used since it is on these days with low external temperatures that their operating efficiency will be at its lowest. Heat generating plant redundancy is also not optimised by having expensive heat pumps sat waiting to kick in on the rare occasion that another heat pump goes down. Far better to meet this need through lower-cost boilers and further reduce capital costs.

Another benefit of including a hybrid system instead of solely heat pump is that it can support further carbon emission reductions in future. One key energy transformation that is looking more likely is the decarbonisation of the gas grid to hydrogen blends and ultimately 100% hydrogen. Coupling that with a heat network’s unique ability to adapt to multiple forms of heat that become available, will result in considerable reduction in carbon emission.

It is no surprise that many cities have already implemented district heating schemes in their regions, which will most likely increase the introduction of them across the country. However, we need to ensure the right technology mix is placed into the plant room to see the full potential on the long road to net-zero 2050.