A COST-EFFECTIVE ROUTE TO COMPLIANCE

Rinnai Director Chris Goggin explores the financial and ecological benefits of hybrid technology in heating and hot water delivery.

Hybrid systems offer an innovative approach to decarbonisation and can provide a practical first step for projects that are not yet able to adopt technologies such as heat pumps as a standalone solution.

UK energy policy is focused on reducing and eventually eliminating the use of fossil fuels. During the transition away from coal, oil, petrol and high-carbon gases towards renewable and alternative energy sources, retrofit projects must find ways to comply with future policy while still maintaining a reliable supply of hot water.

One possible solution is a hybrid system, which combines two forms of fuel or power to deliver cost-effective and consistent heating and hot water performance.

Hybrid technology can combine a traditional fuel source, such as natural gas or LPG, with renewable technology such as solar thermal panels or a heat pump. The system is designed to optimise performance according to factors including outside temperature, current energy prices, space-heating demand and domestic hot water requirements.

Rather than relying on a single fuel source or technology, hybrid systems use two forms of power or heat generation to meet the daily demands of commercial applications.

For domestic hot water systems using continuous-flow water heaters alongside heat pumps, the renewable heat generator provides the base load, while the water heaters top up the temperature when required. This approach is built into the system and helps ensure reliable and efficient performance.

Using two separate energy sources offers several benefits for UK retrofit projects. From a financial perspective, electricity costs can be higher than natural gas, so combining renewable electricity with a traditional fuel source can make running costs more manageable than those associated with a fully electric system.

The initial capital cost of a hybrid system can also be lower than that of a fully electric alternative, helping to reduce whole-life expenditure.

In terms of operational performance, a hybrid heating and hot water system combines two technologies to improve energy efficiency while maintaining consistency. The system can make use of heat pump or solar thermal technology during favourable weather conditions, while an auxiliary appliance provides additional support during colder periods or when demand increases.

This allows each technology to operate where it is most effective. Combustion-based water heating can boost the renewable base load when necessary, helping to maintain reliable domestic hot water performance.

Another benefit is the potential to extend the service life of each technology. As neither heat source has to satisfy the full demand independently, the workload placed on individual components is reduced, which can help improve system longevity.

Hybrid systems provide a practical route towards achieving environmental objectives. Not every customer is able to make the financial commitment required for full decarbonisation, so technologies that combine renewable and traditional energy sources can help bridge the gap.

This approach introduces customers to cleaner and alternative energy sources while allowing them to maintain greater control over energy costs through the continued use of conventional and often more cost-effective fuels.

Hybrid systems can also be particularly useful in buildings that do not have the space, infrastructure or plant room capacity required for full electrification or increased stored hot water volumes.

The principal components of a hybrid heating and hot water system can include:

Heat pump: The renewable backbone of the system. Most hybrid systems use air source heat pumps, although ground source heat pumps can also be suitable for certain applications, particularly in commercial buildings.

Condensing gas boiler or water heater: A high-efficiency appliance that acts as the auxiliary heat source. Modern condensing water heaters recover as much heat as possible from combustion gases, helping to improve energy efficiency.

Solar panels: Solar thermal collectors can contribute heat directly to the system or supply a buffer tank. This heat can be used before the system calls on the heat pump, boiler or water heater.

Control unit or smart thermostat: The control system acts as the brain of the installation, deciding which heat source to use based on real-time conditions. Many systems incorporate weather compensation and predictive controls.

Buffer tank or hot water cylinder: These are optional but recommended where the system supplies domestic hot water. A buffer tank helps smooth out fluctuations in demand and can improve efficiency. Additional cylinders may also be used to provide minimum water content or meet higher hot water demand.

Sensors and meters: These monitor temperature, flow rates and energy use, providing data to the control system and enabling automatic switching between heat sources.

Hybrid water heating provides a viable method of reducing both costs and carbon emissions while maintaining reliable operational performance. For domestic and commercial customers who are not yet able to move to a fully decarbonised system, hybrid technology can offer a practical and effective alternative.