Written evidence submitted by Recoup Energy Solutions (DHH0122)


Recoup Energy Solutions Ltd specialise in Waste Water Heat Recovery Systems (WWHRS) for showers. This is a technology that can have a dramatic impact on the amount of energy used for Domestic Hot Water (DHW) when showering. WWHRS is a completely passive technology requiring no end-user interaction and will recover up to 68% of the energy that remains in the shower water as it leaves the drain and returns this to the DHW system, potentially reducing total energy used for showering by over 50%.

Recoup are submitting a response to this call for evidence as we believe WWHRS could be a vital technology in helping the UK move towards net zero emissions, by assisting with a large energy reduction associated with hot water use within both residential and commercial buildings. As we move towards a focus on renewable energy, there is a need to reduce the demand placed on the infrastructure, especially at peak times and WWHRS can be a strong part of this approach.

Recoup Energy will focus on the first three terms of reference for the inquiry, as we believe this is where our knowledge is best placed.

1. What has been the impact of past and current policies for low carbon heat, and what lessons can be learnt, including examples from devolved administrations and international comparators?

See response below as our answer overlaps the two inquiry points.

2. What key policies, priorities and timelines should be included in the Government’s forthcoming ‘Buildings and Heat Strategy’ to ensure that the UK is on track to deliver Net Zero? What are the most urgent decisions and actions that need to be taken over the course of this Parliament (by 2024)?

Despite the large impact of hot water on energy use within buildings, focus has always appeared to be heavily towards heating alone rather than the energy associated with heating and hot water. With such an improvement in the fabric of new buildings, we now see moving forward in residential dwellings and many commercial buildings (E.g. Hotels, Leisure facilities and student accommodation) that hot water is the largest user of energy.

It is estimated that up to 79% of DHW is used for showering within the home (MEErP Preparatory Study on Taps and Showers, 2014, p86) and SBEM calculates a similar proportion within commercial buildings. WWHRS therefore could potentially reduce the buildings total emissions and energy use by up to 25% due to this high DHW load. If a single technology associated with space heating was capable of this, it would certainly already be included in current and future policies, so the same level of analysis should be given to the impact WWHRS could offer.

Current policies such as ECO3 only focus on technologies that can reduce space heating demand, due to the primary legislation, even though hot water always falls under the term ‘heat in homes’. Whilst it is vitally important to ensure that a home offers a decent level of comfort, affordability and energy efficiency associated with space heating there comes a point where either the insulation/fabric has been upgraded as much as possible or it is not financially viable to go further. If DHW was also targeted, considering this is still approx. 25% of the energy used across all dwellings (Energy Saving Trust), the resulting lower emissions and costs for the home owner or tenant would still be sizable. Technologies such as WWHRS would be installed by the same engineer who installs or upgrades the heating system, reducing the visits and different personnel required to attend a property.

Importantly, WWHRS is completely passive and not reliant on any specific energy source. Therefore, with the current Boiler+ scheme that requires a secondary measure to be installed with a new boiler to further improve the heating system, all extra measures are only associated with the heating. These measures also have the potential to be redundant in future years if there is a change to the energy source within the dwelling used for heating and hot water. WWHRS could be installed with a combi boiler in the next 5 years and then in 10-15 years if that dwelling moved to a heat pump, the WWHRS would continue to reduce energy demand for DHW, potentially making the transition easier as less stored hot water would be required and improving the performance of the heat pump by increasing the effective COP for DHW production (Discussed in point 3 below).

Finally, considering the costs associated with retrofitting and the peak energy demands that are placed on the infrastructure by DHW, where practically possible WWHRS should be mandated (Like self-regulating devices for heating) for new construction and this would greatly reduce demand on the future energy sources we rely on, be that electric or hydrogen. Canada has been using WWHRS technology for several years and in 2017 the provinces of Ontario and Manitoba have made WWHRS mandatory in new residential dwellings to ensure that the impact of the technology wat available for years to come.

3. Which technologies are the most viable to deliver the decarbonisation of heating, and what would be the most appropriate mix of technologies across the UK?

We believe that form a heating and hot water perspective, decarbonisation of the grid will lead to a much wider use of heat pumps in new buildings and upgrading heating systems in those off the gas grid with hydrogen playing a vital role moving forward to transition existing homes on natural gas to a lower carbon alternative.

In both cases, as the energy source has a lower carbon intensity from the start, the key technologies should be the ones that lower initial demand to put less strain on the network at peak demands as well as further lowering our carbon production.

As it is completely energy neutral, WWHRS systems offer a solution to both peak demand reduction and further carbon savings. As they are completely passive, no additional energy is required and as the energy recovered is local to its use, the technology greatly reduces primary energy demand.

The above is important for the adoption of Heat Pumps moving forward, as it is known that within a well-insulated home, the Coefficient of Performance (COP) for heating of a heat pump is incredibly high. However, it has been reported that for DHW the COP drops on average to 2.06 (UKGBC, Building the Case for Net Zero, Sept 2020, p24). With showering being such a large part of this demand, by ensuring that WWHRS is installed as a complementary technology to heat pumps, a large load reduction can be achieved.

With a WWHRS unit installed, the effective COP of the system (Heat Pump and WWHRS) for a 9 litre/min shower could be lifted to 4.68 when showering and if showering is 50% or 70% of total DHW load, this is an overall increase to 3.37 and 3.89 respectively. This is a large reduction to both the individual heat pump and the wider electric infrastructure (Discussed in more detail below).

WWHRS is completely energy neutral, so as well as working with Heat Pumps, it also works alongside gas/oil boilers. Considering retrofit costs of a property can be considerably higher and the desire to move away from fossil fuels in the UK to meet 2050 targets, we would suggest that having WWHRS installed in all new homes (Gas or electric) would support a transition at a later date to electric if the initial fuel of choice was gas.

Above, it was noted that an average COP of 2.06 is expected for DHW production by the Heat Pump. However, with consideration given to the primary energy factor for electricity (1.51) there is a considerably larger demand on infrastructure to supply the electric needed for DHW. As the UK looks to transition to an electric supply generated from renewable sources, focus will be placed not just on further carbon savings but also peak load demand reductions. A recent report from BEIS (Electricity Generation Costs 2020, August 2020) details enhanced levelized costs for onshore, offshore and large solar, of £56, £69 & £53 per MWh respectively. The energy saved by WWHRS over its lifetime given the costs of product and installation leads to an equivalent £/MWh cost of £7.17 (DHW heated directly by electric) or £16.15 (DHW heated via Heat Pump), leading not only to a large energy reduction at peak times but considerable savings vs project costs for renewable production.

As the UK heads towards a new period for Carbon budgets and the expected £/tCO2e to keep rising between now and 2050, even with carbon emission factors reducing for electricity over this time, the extra carbon saved by WWHRS and therefore impact on carbon budget targets could result in a £/MWh below £2 and potentially into a net saving scenario WWHRS was installed at scale across the UK. All our calculations for this area available in a separate excel sheet that we would be happy to share with the inquiry.

A transition to Heat Pumps from the popular current solution of a combi-boiler would result in the requirement of additional space required for stored hot water. WWHRS cannot remove this requirement, however, in counties where WWHRS has been used for a longer period there is a consistent approach to reducing cylinder size where WWHRS is installed (E.g. In the Netherlands, cylinder size is reduced from 300 to 150 litres where WWHRS is present). This results in smaller space requirements, less heat loss from the cylinder (Further CO2 savings) and lower costs.

We believe the above approach could also be applied to buildings that transition to hydrogen, but currently we do not have similar government figures for £/MWh hydrogen production to accurately calculate this.

It should also be considered, that once a WWHRS unit is installed, there is no operational carbon emissions associated with it and at the end of its life cycle (>40 years), the materials used in construction means that the majority will be recyclable making the technology a cradle to cradle product for embodied carbon. WWHRS installed across 10M homes could save the same amount of energy produced by 1.3 Offshore wind farms, 50 onshore or 350 large solar installations. All of these as well as having higher £/MWh costs would have much higher associated embodied carbon during construction.

December 2020