“The advantages for a commercial

site from a hybrid heat pump/gas

boiler system is the ability to smartly balance the heat generators.”

the cold, dark winter months. In a fully hybrid heat pump system, both heat generators can cover the entire heating load, where the energy sources can be freely selected according to definable criteria including efficiency, emissions and price.

With two heat generators and two energy connections, even when there is a pre-existing gas connection, there will be new issues of logistics, space requirements and increased complexity of plant, hence a higher (50 to 60%) CAPEX cost compared to a pure condensing heating system.

The advantages for a commercial site from a hybrid heat pump/gas boiler system is the ability to smartly balance the heat generators, guaranteeing all important high system temperatures while reducing the maximum power consumption for greater efficiencies and lower operational costs.

As well as being able to be cost-effectively controlled, it can also be optimised for CO2

emissions by selecting the

optimal (ecological) heat generator whenever possible via an energy management system incorporating smart metering. Should the building envelope subsequently be renovated, the required heating load will decrease further, and the existing gas boiler can take on less of the annual heating work and eventually could even be retired.

If the building is big enough, we can also make a case for incorporating combined heat and power (CHP) into the hybrid system. The CHP is not used to offset low- temperature heat pumps, but rather the gas heater. Sat between the two, the CHP generates onsite electricity from a gas powered engine, efficiently recovering heat from the process.

Such an approach will still offer some carbon savings, definitely cost savings and, if that CHP is a low NOX

appliance (m-CHP) when compared to the boiler, then we also have NOX

saving. At worst, such a system is going to be carbon neutral but crucially low NOX which is

gas fired water heating. Just as electricity is becoming greener, so too can the gaseous fuels which, looking ahead, will contain larger shares of renewable energies, such as ‘green’ hydrogen gas and other synthetic fuels.

So do you go all in on renewable electric, hold out for ‘green’ gas but take a hit in the short term from SECR, or take a more practical, hybrid route that combines the advantages of both fuels to cost effectively meet the immediate demands of delivering sustainability across the built estate?

A hybrid approach, at the most basic for heating systems, consist of two heat generators, of which at least one is operated with renewable energies and one with fossil fuel. For instance, a system could consist typically of an air source heat pump (ASHP) designed for a system baseload and a gas condensing boiler for peak load, such as during

increasingly a requirement for consultants and specifiers to pass building planning. m-CHP also benefits from inclusion in the new SEG legislation so excess generated electricity can be sold to offset the CAPEX. The addition of m-CHP does require a certain level of oversight, so it is important to factor in the costs of regularly monitoring, managing and maintaining the system to ensure long term guaranteed efficiencies and relatively rapid ROI.

By its own appraisal, the government’s fourth and fifth carbon budgets are currently off track, meaning pressure will fall to facility managers to address sustainability across their estates. Grounded in the real world, a hybrid approach is a practical and cost effective method of balancing the new with the familiar, leveraging and optimising existing gas infrastructure which remains the most common choice for the provision of heating and DHW. It gives a proactive response to sustainability in the short to mid-term and gives managers the breathing space to appraise new technologies that will emerge and help achieve Net Zero by 2050. TOMORROW’S FM | 47 micro

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