CARBON AND ENERGY REDUCTION
emissions from DHW in these buildings can be daunting. However, while there can be no silver bullet solution, there are numerous opportunities to achieve more sustainable, energy-efficient hot water generation across healthcare premises. The focus should be on reducing operational energy usage and increasing renewable energy supply where possible, all the while prioritising safe water. With this in mind, let’s explore some of the options.
Energy efficiency The first step should always be to identify and act immediately on any opportunities to reduce energy demand. Energy efficiency is critical, because it lowers energy consumption and associated emissions and costs. The cleanest and cheapest kWh of energy is, after all, the one we don’t use. Where hot water is concerned, quick wins might include switching to low volume shower heads and taps to lower water and energy usage, or adding lagging to pipework to reduce heat losses.
In buildings where a central boiler plant and calorifier provide both heating and hot water, separating out the hot water is advisable to avoid unnecessary energy use. Heating is typically only required from autumn through to spring, and is needed constantly while the building is occupied. Hot water is an annual requirement, and required each day that the building is in use. However, there are peaks and troughs in demand for hot water throughout the day. For this reason, it is senseless to generate these two very different requirements from a single source. Having dedicated plant for each means that the chosen technology can be sized more closely, and, therefore, accurately, to meet the specific requirements for each building. This makes more effective use of energy, and opens up the ability to site direct electric or direct gas-fired hot water equipment at – or very close to – point of use. Another option to improve energy efficiency might be to upgrade any non-condensing direct-fired water heaters to more energy-efficient
Figure 2: With refurbishment projects, for example, where the natural gas supply might be maintained, there is the opportunity to use air source heat pumps to preheat direct gas-fired water heaters.
condensing models to drive down energy consumption and emissions.
Heat pumps For the larger task of replacing the heating system, air source heat pumps (ASHPs) are widely viewed as one of the favoured technologies to decarbonise heating and hot water across the NHS estate. Using refrigerant technology to heat domestic hot water is an attractive proposition for reducing associated emissions, as the potential efficiency of air source heat pumps can be up to 400% in many cases. This means that for every 1 kWh of electricity used to run the heat pump, you get up to 4 kWh of heat output. Certainly, in newer buildings, heat pumps will play a key role in achieving low carbon hot water. It can, however, be more challenging to make older hospitals benefit from an ASHP solution. Converting large existing
hospitals that use gas-powered steam or high temperature water heating systems to a low-carbon solution, for example, will typically need to be carried out in several stages. Available space, time, and budget will be some of the factors that should be considered at the outset. The electrical capacity of the site will be a further consideration when switching to electrical heat, especially where EV charging points are in place. Putting a clear roadmap in place – identifying the overarching goals, the available time to complete the work, the budget and any funding opportunities – will make it possible to plan out and design the various stages of work. Experienced manufacturers and heat experts will be able to advise on the available options, as well as the latest technologies and designs to help Trusts plot the most appropriate
June 2023 Health Estate Journal 55
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