Housing on the water

Explore the ever-expanding market profile for ground source heat pumps


In this blog, Stephanie Gregory, Director of Marketing at Kensa Heat Pumps, explores the market drivers and emerging applications of ground source heat pumps.

Fifteen years ago, innovative self-builders were the early adopters of ground source heat pumps; the technology was an obvious investment for those intending to remain in a dwelling for a lengthy period and benefit from the ultra-low running and ownership costs.

Offering efficiencies of 350% – that is for every 1kW of electricity used to power the heat pump 3-4kW of heat energy are produced – ground source heat pumps are an attractive technology for those looking to invest in a sustainable long term heating solution; especially attractive given the heat pump has a life expectancy of 20-25 years, whilst the ground collectors – pipes used to extract heat energy from the ground or water to feed into the heat pump – should last for 100 years.

The technology has changed relatively little since this time; indeed when you get to the very nuts and bolts of it all ground source heat pumps operate in the very same way. However, the market profile for ground source heat pumps has changed dramatically.

Self-builders remain a keen advocate for ground source, thanks in part to the Government’s Renewable Heat Incentive (RHI). In stark contrast to the boom and bust of headline grabbing (not for all good reasons) solar PV, wind and biomass, ground source heat pump sales have been modest; thanks to the Government’s commitment to continue with the RHI to 2021 with ground source attracting one of the most favourable rates, and their strategy to deliver 2.5 million heat pump installations by 2030, the political and financial case for ground source heat pumps is a significant market driver for self-builders looking to achieve that dream low carbon home.

Domestic bliss – A look at the Domestic RHI

The structure of the domestic RHI lends itself well to rewarding installations in larger properties and this is where ground source heat pumps in particular can have a significant part to play.  With an attractive tariff of 20.89p/kWh paid over seven years, the RHI pays on the renewable heat contribution from a heat pump system, with payments “deemed” (calculated) based on the annual heating and hot water energy consumption of the property, based on an EPC.

By their nature, the larger the property, the higher the overall energy consumption is likely to be and therefore annual RHI income will be greater for larger properties.  Where ground source scores is that the installation cost per kW tends to decrease with increasing system size.  This means that the overall returns under the RHI become significantly more attractive for larger properties.  For example:

  • 3 bed semi: 8kW system.  RHI income:  £11k/7 years
  • 4 bed detached: 12kW system. RHI income:  £17k/7 years
  • 5 bed detached: 15kW system.  RHI income:  £20k/7 years
  • 8 bed country house: 24kW system.  RHI income:  £37k/7 years

A restriction often associated with heat pumps is the limitation on outputs of much more than 12kW available on single phase electricity supplies.  Indeed, for air source units – where the capacity typically drops with the air temperature – a nominally rated “12kW” air source heat pump may only provide around 8kW of useable heat at design conditions of -2°C.  While ground source doesn’t typically suffer from this issue – the heat source temperature (i.e. the ground) is relatively stable all year long – there are few single phase units available on the UK market that have output suitable for very large properties.  However, a small number of ground source heat pump manufacturers have developed products that are able to provide a range of single phase ground source heat pumps to meet these larger property’s needs. Kensa Heat Pumps for example offer single phase ground source heat pumps up to 24kW, as well as clever “hybrid” models which can provide single phase outputs of up to 21kW for heating and hot water at a flow temperature of 65°C.

District heating – A look at the Non-Domestic RHI in domestic applications

The enhanced tariffs under the Non Domestic RHI for ground source heat pumps level the playing field in the market compared with other renewable heat technologies and ensure ground source heat pumps can be considered a viable and financially attractive proposition for businesses, public sector organisations, care homes, schools and many other non-domestic applications

So while the domestic strand of the RHI will provide some lucrative opportunities in the large domestic sector, there is a wider opportunity emerging for projects involving multiple residential properties or outbuildings, either refurbishment or indeed new build by using the non-domestic strand of the RHI.  While primarily designed for commercial buildings, the non-domestic RHI also supports residential district heating systems. This has provoked innovative thought leaders in renewables to design domestic ground source applications that attract a significant financial return on their investment through the ‘commercial’ stream of the RHI, whilst delivering the energy savings and benefits ground source naturally brings; thus opening up new market opportunities and transforming the market profile for the technology.

A particularly innovative advancement in the technologies application is that of district heating. Previously the domain for costly and impractical plant room systems, ground source heat pumps are quickly being recognised as a means to deliver a durable energy infrastructure, with individual units and controls per dwelling, on projects from small holiday parks to large multi-occupancy dwellings.

The ground source district approach features individual ground source heat pumps installed in each property, served by a shared communal ground array.  And by using the low grade heat circulated through the ground array as the “district” part of the scheme, the system architecture overcomes many of the shortcomings of traditional central plant district heating systems, for example eliminating distribution heat losses through the district pipework and complications over apportioning of energy bills – as in the micro district approach, each property has its own ground source heat pump and own electricity bill.

District ground source heat pump systems are of particular interest because they deliver on a number of key factors: they are eligible for a 20 year income through the Non Domestic RHI; they are eligible for an upfront ECO grant in social housing on retrofit schemes; they significantly reduce fuel bills and as a consequence fuel poverty; they meet carbon compliance requirements in new build developments; they can be used for as few as two properties.

The last point is particularly interesting – ‘they can be used for as few as two properties’. DECC has confirmed that as few as two properties linked together in this way meets the requirements of a district heating system, opening up the opportunity for many small residential developments, where for example multiple out-buildings are being converted for sale or rent.  In fact the concept can apply to a wide range of applications, from care homes, student accommodation, holiday lets, blocks of flats and social housing. This approach is being viewed by many as the solution for rural, off-gas grid homes, and particularly those in fuel poverty – typically social housing.

Off-gas developments are traditionally heated by oil, LPG, or electric night storage heaters. Costly and impractical – when you need the heat most it is either unavailable (in the case of night storage heaters which emit heat during the day, not night, when the temperature drops), or the heat source is in short supply (in the case of oil or LPG when the weather turns it becomes increasingly problematic to make fuel deliveries – and the cost tends to go up) – traditional off gas heating methods are not the most economical, efficient, or environmentally friendly of systems.

However, the district approach featuring ground source heat pumps is changing the rural heating landscape. Particularly cost effective in small clusters of properties, district heating solutions are popping up all over the country. A social housing scheme in Burton-on-Trent has recently seen 17 of their off-gas sites, totalling 130 homes, connected to mini district heating schemes, or ‘micro district’ schemes. Replacing night storage heaters, the project for Trent & Dove Housing was delivered by Kensa Heat Pumps, and featured pairs of bungalows connected to shared communal borehole ground arrays, which feed heat into individual Kensa ‘Shoebox’ ground source heat pumps that are located inside each property. Tenants immediately reported fuel bill savings of between £300-£500, whilst Trent & Dove Housing were able to get upfront subsidy support via the ECO to reduce initial costs, and 20 years of quarterly payments through the Non Domestic RHI.  Trent & Dove Housing have since completed a ground source district scheme replacing night storage heaters in 60 off-gas flats.

Micro district systems also have a place in new build developments, too. Government policy driving new build social housing developments, coupled with increasingly stringent Building Regulations on environmental standards and energy efficiency mean that low carbon forms of heating are becoming a standard requirement.

Developments in rural or off gas grid areas featuring ground source heat pumps benefit from reduced CO2 emissions and improved carbon compliance compared to traditional fuels. Unlike other renewable heating technologies, ground source heat pumps do not require planning permission regarding noise emissions. Equally, in gas connected areas ground source heat pumps provide a carbon compliance solution without the need for supplementary carbon saving measures, such as solar PV.

Shropshire Rural Housing are a pioneer of renewables in the new build housing sector, having completed a retrofit scheme featuring individual boreholes under the Domestic RHI, they have recently opened a new build housing scheme featuring clusters of properties connected to a borehole array under the Non Domestic RHI.

Ian Richardson, Shropshire Rural Housing Association Chief Executive, says:

“The delivery of affordable warmth is important to Shropshire Rural. Given that the majority of our housing stock doesn’t have access to mains gas, Kensa’s micro district ground source heat pump solution is proving to be very helpful.

We now have more than a third of our homes getting their heating and domestic hot water in this way; whether through retrofitting or by incorporating the ground source heat pump into new homes.”

Ground source district heating is not just the domain for social housing, however. The expected increase in staycations is triggering an increase in the number of holiday homes and lodges. Typically these complexes have large land areas, or even water sources (think lakes, ponds, fisheries even) – opening up the scope of district schemes utilising a number of different heat sources and extraction methods. One such innovative example of the diverse range of ground arrays for district heating is a holiday park in Wales.  The ‘Secret Yurts’ development features shared horizontal boreholes arrays, which were drilled into the side of a hillside. This method was chosen because of the water level hindering potential depth of a vertical borehole, and thus the hillside offered an elegant solution to deliver the sustainable heat to the ground source heat pumps located throughout the eco park’s lodges and buildings.

Clearly, renewable heating technologies like ground source heat pumps have a significant role to play in mitigating climate change. But closer to home, their impact socially should not be forgotten. Market incentives which enable the quicker adoption of sustainable technology are a very tasty carrot for those who are able to build their own dream home. Equally, for those who provide homes, the market drivers and innovative applications of ground source heat pumps are creating opportunities for the UK housing sector to enjoy sustainable, controllable, durable, and efficient heating solutions, with an infrastructure that will last for a 100 years from now.

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