Hot water
aware, although it is well recognised that many clients today are seeking ‘green living’ options, making this just as much a fiscal decision as any other. Other factors, though, can include everything from geology to available space. A care home’s location will instantly direct certain decisions, as the hardness or softness of the water will impact options. For instance, stainless steel cylinders will be preferential in soft water areas as they are resistant to the corrosive nature of the water, while lower-cost glass-lined vessels are preferable in harder water areas. However, high-intensity heating, such as that delivered by electric immersion, can be extremely detrimental in hard water regions, accelerating limescale generation to the point that it can irreparably damage a system in a matter of months if not correctly maintained. That does not preclude electricity as a choice, but it does affect how applications should be designed. The real leading question is: do you choose gas or electricity? If gas, do you opt for direct or indirect heating systems; if electricity, do you choose an immersion or electric boiler as your source of thermal energy? Whichever route you decide upon, your system will additionally require a low-carbon heat source which will preheat the water, reducing the energy consumption of the water heater and, in turn, reducing carbon emissions and the running costs of the water heater. There are several choices for securing
low carbon heat, including biomass, combined heat and power (CHP), ground or
Solar thermal collector options for commercial buildings
Do you electrify all equipment now on the basis that the grid will become zero carbon, or hold out for the option of carbon-free gas such as hydrogen?
water source heat pumps, air source heat pumps (ASHP), solar photovoltaics (PV), and solar thermal. Through a mix of cost and simplicity, the best technologies to use for domestic hot water (DHW) systems required by care homes are either ASHP or solar thermal.
Heat pumps are a technology that
operates most efficiently at lower temperatures. While this makes heat pumps highly applicable to domestic applications, care home DHW systems require 60°C working flow for safe operation and anti- legionella processes. The heat pump can be pushed to deliver a higher percentage contribution, generating temperatures of 45- 50°C for preheat, but this comes at the cost of performance efficiency, requires electrical energy, and has operating cost implications. Compared to an equivalent-sized direct- electric (ie. from the grid) system, one with an ASHP can achieve carbon reductions of 42-47 per cent, while saving 25-35 per cent of the energy costs. The system will still be required to top up heat to the necessary 60°C, using either immersion or an electric boiler. This, combined with the heat pump’s reduced operational efficiency, means it will still be much more expensive to run than an equivalent-sized gas-fired system based on a modern and efficient (109 per cent net) water heater.
The recommendation in this case is to Adveco R32 ASHP installation April 2023
www.thecarehomeenvironment.com
keep electrical demand down by increasing the size of the hot water storage, which is then heated more slowly. This is very different to the high energy input, low storage seen with gas-fired systems. A 30kW energy source can heat 750 litres/hour by 34°C, so when the system draws hot water at a faster rate than it can be heated - say, to 44°C for hot showers - you start to get complaints that the water is ‘cold’. The larger volume cylinder helps to overcome this undersizing, allowing for a two hour reheat cycle that maintains enough water at 60°C to meet daily demand while slowly heating reserves through the night when demand is minimal, to meet the morning
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