RETAIL, HOTELS & LEISURE


Roadmap to low carbon hot water


Hot water systems are big energy users in the hotel sector, so what are the opportunities to reduce their carbon intensity in a way that supports net zero goals? Andy Green looks at the scope of the challenge.


Andy Green www.baxi.co.uk


I


Head of technical solutions Baxi


n the hotel sector, as in most industries, sustainability is high on the business agenda, and with a 2050 net zero target enshrined in


law, it’s easy to understand why. One of the largest energy users in hotel buildings is the hot water system. As this vital service is typically associated with guest comfort, the system needs to be highly efficient and reliable while meeting the high volumes of hot water demand as sustainably as possible. How, then, to choose the best


approach to low carbon hot water? As with heating, each hotel building will have its own unique requirements and be at a different stage on the net zero pathway. However, there are commonalities in the way they use hot water. Hot water use in hotels is


traditionally characterised by an extremely high peak in the morning for guests’ showers or baths, followed by a long period of low demand. A second peak will typically occur in the evening with the kitchens serving the hotel restaurant having a high demand for hot water for catering and washing. In addition to meeting peak demand, the solution must generate temperatures high enough to store the domestic hot water (DHW) above Legionella temperatures (60ºC ) to meet strict hygiene requirements. With that in mind, let’s consider some of the options.


All-electric approach Ensuring reliable, efficient, low carbon hot water provision can be a complex challenge – even in new hotel buildings, which are designed to support net zero operation. For new build properties, an all- electric system will increasingly be the chosen approach using a combination of technologies including heat pumps and point of use water heaters like Heatrae Sadia Multipoint Eco. With the arrival of high-temperature


EIBI | SEPTEMBER 2024


heat pumps that use environmentally- friendly natural refrigerant R290 (propane), designers and energy managers have more flexible, space-saving solutions to meet the DHW supply. Baxi’s Auriga HP+ high temperature air source heat pump (HT ASHP), for example, can deliver up to 80°C flow temperature to ensure adequate Legionella control. The caveat is that the coefficient


of performance of HT ASHPs falls off at higher temperatures, affecting the real-world efficiency and operating costs. Running costs will also need to factor in the spark gap given that electricity is currently around four times that of gas. Ask your chosen solutions provider


for advice on the various factors – including location, budget, electrical supply, size of cylinders – that should be considered at the outset.


Retrofi t challenges In smaller or independent legacy hotels, the achievable options to improve hot water efficiency are, realistically, likely to be more restricted. Larger hotel organisations often have corporate sustainability targets in place and policies and budgets to match. However, in smaller independent hotels, capital expenditure, retrofit challenges and available time to complete the works could serve as detractors from carrying out refurbishment improvements. Ultimately, though, the direction of


travel to lower carbon technologies is clear. So whatever the building type, hotel owners and energy managers are advised to define a


One of the largest energy users in hotel buildings is the hot water system


decarbonisation roadmap to ensure future compliance with tighter regulations. Many hotels use traditional direct


gas-fired water heaters as one of the most efficient means of meeting the sudden peaks in hot water demand, as they can deliver large volumes of water in a short time. A major benefit of this approach is that it reduces energy loss between peak periods as the system will only use energy when hot water is required. However, it should be noted that


Approved Document L of the Building Regulations now effectively rules out non-condensing water heater replacement in the vast majority of buildings, in favour of more efficient condensing models. So where relevant, an upgrade to condensing water heaters should be planned now. This will help improve the efficiency of the hot water system – by up to 20% – and simultaneously protect business operation.


Hybrid solutions The next stage on the roadmap should be to consider integrating an


air source heat pump (ASHP) in the system to provide pre-heated water to the direct-fired water heaters. Using hybrid heat pump solutions


for DHW generation brings many advantages in legacy hotel buildings. The heat pump could be used to pre-heat a storage vessel, sized to contribute to the peak demand, which will feed the water heaters. This design satisfies the hot water


requirements safely and efficiently by reducing the amount of energy required to raise the hot water temperature to a useable and safe level, with the majority of demand being met through renewable energy. Technical design is a critical


area where experienced solutions providers should be able to provide valuable support. The aim should be to maximise heat pump contribution performance where possible, while taking all project limitations into account. Your chosen solutions provider should be able to provide advice on these aspects to address and avoid any conflict.


The Auriga HP+ high temperature air source heat pump can deliver 80ºC flow temperature


Working together With no silver bullet to low carbon hot water, hotels and their energy managers will look to their manufacturer or solutions provider for advice. By engineering different design options, backed with predicted energy and carbon savings and capital expenditure modelling, we can help energy managers and designers make the best choice for their hotel building. Whether the path to low carbon water requires an all-electric or hybrid approach, by providing support from the outset, working together we can ensure hotels are on track for net zero. ■


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