Sustainable showering

One of the biggest challenges that the UK plumbing and heating industry faces, as we decarbonise our heating and hot water systems, is consumer behaviour. The majority of UK homes have their heating and hot water delivered by gas and oil boilers with an estimated 17.5 million homes currently using a combination boiler.

The consumer expects comfort and hot water on demand, but if the market diverts its attention to the mass deployment of heat pumps during the 2020s, will it be faced with not only a skills gap but also an innovation gap?

The industry is now assessing the challenge of how it can train an additional 35,000 heat pump installers by 2028 to deliver more than 600,000 heat pumps per year. One of the hurdles that installers will need to navigate, when converting a high output gas combination boiler to a heat pump, is ensuring the domestic hot water (DHW) cylinder is sized correctly to deliver a showering experience that is the same, if not better. As we tackle this challenge, can innovative showering technology help reduce the issues surrounding the demand and space constraints of the new modern home?

Sizing the hot water cylinder to meet the consumer needs

The standard BS EN 12831:2017 Part 3 demonstrates the method required to successfully calculate the correct DHW cylinder volume to meet the needs of the consumer. The first thing that the installer needs to do is to understand the consumer’s hot water requirements before attempting to specify a specific storage volume. Common practice in the UK would be to size the DHW cylinder based upon various rule of thumb factors such as the number of bathrooms or the number of litres of water usage per person per day. However, without the benefit of the high output safety net delivered by a typical 30kW system boiler, it is critical that the installer pays more attention to the consumer’s hot water usage and volume patterns. This is an example of why the industry has highlighted a need to create a new qualification in low temperature heating and hot water systems, as there has never been a more important time for installers to expand their knowledge and skills in low-carbon systems.

Saving carbon whilst saving water

While industry and Government are focusing their efforts into reducing energy consumption, could they be overlooking the importance of water as a resource? Sir James Bevan, chief executive officer of the Environment Agency, asked last year: “How do we avoid the jaws of death – the point at which, unless we take action to change things, we will not have enough water to supply our needs?” This quote highlights the problem with the public’s expectation that the supply of clean water is infinite. One of the unique challenges of saving water compared to carbon is that we can install a new heat source and insulate our properties whilst maintaining consumer comfort, however, saving water requires a huge shift in consumer behaviour. Is the consumer prepared to sacrifice their powerful shower to reduce water consumption, and how will innovations in shower technology help support the consumer on this journey, without compromising their experience?

There has never been a more important time to innovate

The holy grail of hot water innovation would be a technology that reduces carbon emissions through the saving of both energy and water, without affecting the consumer experience. There is one such disruptive showering technology that aims to try and solve this problem which is designed to inject forced air into the flow stream of water as it enters the shower head. The novel feature of this type of technology is its potential to deliver the same consumer showering experience whilst using less energy and water, although the big question is: what does the consumer think? It is worth noting that reducing consumption at the shower outlet also plays a role in reducing carbon emissions through the pumping and treatment of water in both the supply and waste parts of our critical infrastructure.

The Venturi principle

The use of air is not a new concept for improving the showering experience using the Venturi principle. This principle restricts the water flow whilst drawing atmospheric air into the water through a small hole in the shower head (figure 1). Shower heads using this technology are often referred to as “aerating”. However, it has limitations with the boosting of performance. In fact, the Venturi principle is also used by one of the CIPHE’s Industrial Associates, Fabdec, which uses it to draw air into the cold water flow feeding the hot water cylinder. Fabdec’s inventive step aimed to recharge the expansion air gap within the top of the hot water cylinder, mitigating the risks associated with losing expansion (figure 2).

Has there been a breakthrough?

Another Industrial Associate, Kelda Technology, has invented a new patented shower product using ‘air-powered’ technology that is capable of providing an energising shower using a flow rate as low as five litres per minute – without compromising shower experience.

How does it work?

The air-powered technology uses the principle of gas turbine fuel injection technology (figure 3). Each shower features an intelligent microprocessor and powerful digital fan which delivers the water and air to the shower head. Within the shower head, the air is propelled through an array of nozzles forming a low-resistance air stream. The laminar water flow is injected into the air where it accelerates and breaks up into perfect sized droplets (larger droplets are better at retaining heat). Thanks to the low-resistance air stream, each droplet is able to travel further with more momentum to deliver an increased effective spray force.

So how could this affect the way installers design a hot water system?

Before an installer attempts to select a specific hot water cylinder, they need to assess the needs and behaviours of the consumer and the property first. One method, which is stated in BS EN 12831, is to carry out an installer/consumer co-design process by finding out the consumer’s typical peak day for hot water usage and ensuring they install a system that exceeds that demand.

Figure 4 illustrates a typical medium hot water user profile from the standard that looks at the percentage of daily hot water consumption that is used at different times of the day. As designers and installers, we need to design to peak requirements with an appreciation of not oversizing a system; but the consumer may require a system greater than that which a typical house would demand.

Therefore, apart from having the right qualification and competence for installing a low-carbon heating and hot water system, communication is the critical ingredient to a happy consumer. So, if we specify a low-carbon, low-water usage shower such as the one designed by Kelda Technology, can we reduce the size of the hot water cylinder?

Figure 4 illustrates a typical effect of retrofitting an air-powered shower compared to a standard bar mixer. It is clear that as long as the consumer showering experience is not affected, then technically the amount of hot storage volume required would be lower.

The CIPHE is working with the industry to develop a regulated qualification in low-temperature heating and hot water systems in dwellings which will include the relevant core competencies required to be a low-carbon heating and hot water installer.

This article originally appeared in the September/October 2020 edition of P&H Engineering, the magazine for members of the CIPHE. You can find out more about becoming a member here.

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