HOSPITALS, HOT WATER AND THE NET ZERO CHALLENGE

The NHS has set an ambitious goal of reaching net zero from its directly controlled emissions by 2040, with a target of an 80% reduction in emissions between 2028 and 2032. For energy managers, understanding the profile of each building across the hospital estate, including how and where energy is being consumed, is fundamental to identify key areas for improvement. But with emissions from hot water and space heating systems alone accounting for 80% of NHS emissions, this is likely to be a key area to address. In particular, hospitals consume large quantities of energy to produce hot water. Let’s consider here some of the common challenges and identify opportunities to improve domestic hot water (DHW) delivery.

Patient safety and wellbeing are a top requirement in healthcare environments. Delivering an adequate hot water supply quickly ensures that healthcare professionals have the water they need to keep patients safe and comfortable.

At the same time, an effective water management programme is essential to prevent the risk of bacterial build up, mostly related to the control of legionella bacteria in often complex water systems. Using hot water temperatures to manage legionella is a fundamental control measure. The Health and Safety Executive (HSE) advises that DHW should be stored at least at 60ºC and distributed so that it reaches 55ºC in healthcare premises1. As the risk of patient scalding or burning increases when water temperatures are too high, temperature control needs to be provided at hot water outlets to protect patient safety.

With this in mind, what are some of the options for energy managers to improve hot water delivery?

Energy efficiency is the logical starting point. The quick wins such as low volume shower heads to save water usage and energy for heating water should already be in place. Similarly, proactively reducing heat losses by lagging pipework. 1 https://www.hse.gov.uk/

In older hospitals that rely on central boiler plant and a calorifier or steam systems, separating out the hot water might be the first step.

Upgrading existing technology to more energy-efficient units is another option. For example, if the building uses non-condensing direct-fired gas water heaters, replacing them with condensing units could drive down energy-related consumption, emissions and costs by as much as 20%.

Heat pumps also offer a promising solution for low carbon hot water generation. With an exceptionally high seasonal co-efficient of performance (SCOP) of up to 400%, heat pumps can deliver up to 4kWh of heat output for every 1kWh of electricity used.

There are two types of air source heat pumps. Some, like the high temperature heat pump coming soon to our Remeha range, are able to deliver the high flow temperature required to meet the design stored hot water temperature. This removes the need for an alternative technology to achieve the required stored DHW of 60ºC or higher, bringing greater design flexibility.

However, it should be noted that the coefficiency of performance of heat pumps falls off at higher temperatures. Another solution, therefore, might be to use lower temperature air source heat pumps with direct-fired electric water heaters.

This approach would involve much higher volumes of stored domestic hot water, so potential issues relating to available space and the weight of the larger cylinders should be considered – particularly when dealing with roof top or non-basement plant rooms. Additional forms of legionella control within the larger volumes of stored water will also need to be managed.

On projects where an all-electric solution is not considered suitable, a multivalent approach to hot water generation should not be overlooked. With refurbishment, 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 (DGFWH).

Using high efficiency DGFWH – especially those like the Andrews MAXXflo EVO which come with antilegionella functions as standard – can bring several advantages over indirect

DHW systems (boiler calorifiers) and even direct electric systems.

This is because DGFWHs have considerably reduced storage compared with other systems, meaning less weight and fewer issues with roof top plant rooms. Control of legionella is more straightforward and recovery times reduced. It is also generally accepted that where a design includes renewable technology, such as heat pumps, solar PV or CHP for example, project costs are higher.

When planning your route to more sustainable hot water generation, there is, unfortunately, no silver bullet but rather a number of options. The most appropriate solution will depend on a number of factors including – but not restricted to – the diverse building types and hot water systems across the estate, where you are on your decarbonisation journey, and the available budget. https://www.remeha.co.uk/ products/heat-pumps/e-hpaw-air-source-heat-pump https://www.andrewswaterheaters. co.uk/products/condensingwater-heaters/maxxflo-evo https://www.heatraesadia.com/ products/cylinders-and-hotwater/unvented-calorifiers/ megaflo-commercial-flexistor

At the same time, the need to ensure a safe water supply is paramount, which is why we now have a dedicated Public Health technical sales team to offer expert advice on a project-byproject basis. Working together, we can help you improve hot water delivery and reduce energy and water waste as part of your net-zero pathway, all the while prioritising a safe, reliable, and efficient hot water service.