Hybrid Heating – A Practical Response For The Commercial Built Environment
Adveco looks at the changing face of commercial hot water & heating, and the increasing importance being placed on the development of hybrid applications to address the real-world challenges of achieving carbon reduction levels set by the government through to 2050.
Around 40% of UK greenhouse gas emissions are accounted for by heating, cooling, ventilation, the provision of hot water and lighting the built environment, and, according to 2019 figures issued by the Department for Business, Energy and Industrial Strategy (BEIS), business remains the third-largest emitter at 17%. In order to achieve climate-neutral building stock by 2050 commercial organisations need support from the industry to provide immediate and practical measures.
Through the expansion of wind power and photovoltaic systems, the generation of electricity from renewables and the importance of electricity in the heating market is increasing, but natural gas still dominates. As attention shifts to a mix of district heating, heat pumps, wind and solar energy, studies show that over the next two decades renewable electricity will be crucial to the energy supply in the heating market.
That said, there remain strong differences with regard to the expected share of renewable energy supply. Independent research clearly argues for a multi-dimensional approach with an energy mix consisting of renewable energy and gaseous fuels with a high share of renewable energies. Studies that are more “almost all-electric” argue in favour of almost complete dominance of the heat pump, while the technology-open scenarios also predict large proportions of heat pumps, but also assume the use of gaseous fuels.
Just as electricity is becoming greener, via an ever-increasing share of renewable energy, so too over time will the gaseous fuels such as ‘green’ hydrogen gas and synthetics.
Why Take The Hybrid Route?
So, let’s consider the advantages of the hybrid approach. This, 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. Often, a hybrid heat pump system consists of a heat pump (air source) designed for a system part load (baseload) and a gas condensing boiler for peak load, for example during 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.
Compared to a conventional combustion heating system though, there will be issues of logistics and space requirements, but as hybrid systems are particularly relevant to buildings in which there is already a gas connection this is generally less of a concern. That said, a hybrid system will require two heat generators and two energy connections, one of which is an environmental heat source. This leads to higher complexity of the plant, requiring more effort and expertise from the system designer, supplier and installer. This all leads to higher CAPEX cost. It is typically estimated that the purchase and installation of a hybrid heating system compared to a pure condensing heating system is going to drive initial costs up by approximately 50 to 60%. So, what are the advantages that outweigh these initial costs?
For older commercial properties where a new heating system is required, but wider renovation is either not feasible or required, a hybrid system can control and avoid issues of project congestion when refurbishing, as the heat pump is used to supplement the pre-existing fossil-based heating system. This helps to save costs as existing boilers can continue to be operated on the currently installed heat distribution, heat transfer and flue systems while the heat pump can benefit from an advantageous coefficient of performance (COP) in the right conditions and setpoints.
A hybrid heat pump/gas boiler system is able to reduce the maximum power consumption of a system by smartly balancing the heat generators for greater efficiencies and lower operational costs whilst guaranteeing high system temperatures to ensure the comfort of those still living or working in the building during refurbishment work. If the hybrid system is also equipped with a buffer tank and domestic hot water (DHW) tank the heat pump can achieve a high proportion of cover for space heating and DHW heating increasing the profitability of the system.
A hybrid heating system cannot only be controlled cost-effectively but it can also be optimised for CO₂ emissions by selecting the optimal (ecological) heat generator whenever possible via an energy management system that incorporates smart metering.
Hybrid systems for commercial properties will typically be planned according to individual project requirements. In cold phases, the heat pump in the hybrid system can only take over part of the heating load due to the design. If necessary, the condensing boiler, especially on cold, dark days with high demand, but a limited supply of renewable energy, completely covers the heating load.
This versatility enables the energy manager to react to price fluctuations, especially in the power grid and possibly also in the gas grid.
Should the building envelope subsequently be renovated, the required heating load decreases and the existing gas boiler can take on less of the annual heating work or eventually could be put out of operation.
In part 2 we consider the continuity of using gas for future hot water applications