Hybrid Heat Networks

Pete Mills, Commercial Technical Operations Manager at Bosch Commercial & Industrial looks at how hybrid heating systems will future proof district heating schemes.

Local authorities, housing associations and developers alike are turning to district heating – or heat networks – for various larger scale developments. Heat networks provide heating and hot water in a high-efficiency, low emissions way and as a result will become more prominent across the country as we continue towards a net zero future.

However, with 2050 still several decades off, different technologies powering the networks should be considered, as much can change in the coming years as innovation dictates. For example, many observers see heat pumps as the primary option for heat network projects, as they are powered by electricity, an energy source that has reduced carbon emissions. However, this could in fact be a limiting factor for heat network’s future flexibility.

Heat pump technology, whilst very good, comes at a cost that adds considerably to the initial capital investment. Air source heat pumps, which are less capital cost, also suffer from reduced efficiency during times when the air temperature is cold. Instead, a more agnostic view should be considered which looks to incorporate heat pumps while leaving the door open for new technologies.

One of the best solutions for this would be a hybrid approach. Take, for example, a plant room where a heat pump takes the lead supported by peak-load boilers. This offers a practical option to keeping capital costs under control while still delivering significant carbon savings.

Heat networks typically operate below 25% of their peak demand for over half of the year, which is why heat pumps are well-suited to large schemes. However, by having peak-load boilers on standby, when the outside temperature drops to its coldest during the winter months the heat network will provide end users with instant peak time hot water and heating.

Ground source heat pumps are a better option in terms of more consistent efficiency across the year. Yes, it means more complexity for the installation stage and will often need expert involvement, particularly where bore holes are used. However, it still makes sense to optimise their coverage of the maximum demand, as this occurs rarely. No point either trying to build in redundancy by additional heat pumps. Much better to meet this need through lower cost, efficient boilers to reduce capital costs.

However, the main benefit of including a hybrid system instead of a sole heat pump is that it can support future carbon emission reductions. For example, it is looking increasingly likely that current boilers will be replaced by hydrogen-ready appliances. So much so that it could become a mandatory requirement when replacing older boilers in the future.

This offers the ability for a simple conversion to hydrogen once a particular area has moved to the new gas. Coupling that with a heat network’s unique ability to adapt to multiple forms of heat that become available, will result in considerable flexibility and load shifting options, and future proofing any district heating scheme.

By carefully considering the design of heat network plant rooms now and the types of heating technology that are installed, will ensure that heat networks continue to achieve their full potential as we continue moving towards a net zero future. Hybrid systems do just that.