Kensa reviews the Greater London Authority report, ‘Low Carbon Heat: Heat Pumps in London’.
Findings regarding the volume of carbon and running cost savings possible with ground source heat pumps with shared ground loop arrays have been published in a report by Etude, commissioned by the Greater London Authority (GLA), ‘Low Carbon Heat: Heat Pumps In London’ (September 2018).
The report concludes that shared ground loop arrays (which were pioneered by Kensa) – defined by Etude as a ‘communal ground loop connected to individual heat pumps’ – are the most efficient, lowest carbon, and lowest cost solution when utilised in new build houses compared to various air source, direct electric, gas and CHP configurations.
In this review, we explore the key points of the ‘Low Carbon Heat: Heat Pumps In London’ report below, including:
Why was the report commissioned?
London aims to be a zero-carbon city by 2050, with Mayor Sadiq Khan committing to expanding the existing target of zero-carbon new homes to apply to all new buildings in 2019 (read Kensa’s blog on how zero-carbon homes can be achieved here).
One of the first steps in this zero-carbon progression is the unique requirement for all new developments in London to achieve an on-site carbon reduction of at least 35% beyond the Target Emission Rate (TER). This percentage will increase over time in order to achieve the zero-carbon London ambition.
London’s Environment Strategy also identifies air quality as a pressing environmental threat to the future of health in London (read Kensa’s blog on air quality here). The Mayor of London is seeking to design integrated policies which deliver co-benefits between air quality and climate change policies.
To support initiatives to improve London’s local air quality and emissions, the GLA commissioned Etude to produce a report to develop an evidence base to inform the implementation of London Plan policies and the final London Environment Strategy publication.
It establishes the key considerations and implications of a greater number of heat pumps in new buildings in London as they are likely to play a significant role in the delivery of low carbon heat.
What were the report’s key findings?
The key conclusions and recommendations in the GLA’s report, Low Carbon Heat: Heat Pumps In London, are:
- Heat pumps are very likely to play a growing role for the delivery of low carbon heat in London.
- When applying a more up-to-date carbon factor for electricity (e.g. 233 gCO2/kWh proposed in SAP 10) heat pumps are a substantially lower carbon system than gas-based or direct electric options.
- In order to deliver low carbon and affordable heat, the efficiency of heat pumps needs to be better understood by the building industry, including policy or a guidance requirement in favour of ultra-low temperature distribution and emitters in all new developments.
- Efficient heat pumps offer a cost competitive form of heating.
The report concludes that:
Heat pump systems provide the lowest carbon heat for all case studies, though significant differences exist between the various types of heat pump. The lowest carbon heat is achieved by the residential block using ground source heat pumps coupled to a communal ground loop. This system benefits from very small distribution losses due to the ambient flow temperature and relatively high efficiencies of 380% for space heating at 35˚C and 290% for DHW at 60˚C offered by ground source heat pumps.
The scenario described above is Kensa’s ambient temperature shared ground loop array, pioneered by the company in 2012 and now utilised by many, perhaps most prominently by eight tower blocks in Enfield, London. Kensa’s Enfield heat pump project features within the GLA report as the model example for their ‘lowest carbon’ system scenario (view Kensa’s Enfield case study in the GLA report here).
Let’s look at some of the report’s key observations in more detail:
The mechanical design of building services must evolve to ensure heat pumps operate efficiently.
Heat pumps must be considered alongside the heat distribution system they will supply, as the efficiency of a heat pump reduces as the temperature it is required to supply increases.
Heat pumps can provide heat (for district heating, domestic hot water and space heating) at lower carbon factors than gas-fired CHP led systems and direct electrical heating when careful consideration of the heat distribution system is matched to enhance the efficiencies for heat pumps.
In order to deliver low carbon and affordable heat, the efficiency of heat pumps needs to be better understood by the building industry. The use of low temperature distribution systems and emitters, the method used to generate domestic hot water and the correct installation and commissioning of heat pump systems can all help to deliver low carbon emissions and operational energy costs.
Carbon factor of heat based on 302gCO2/kWh. Source: Etude, ‘Low Carbon Heat: Heat Pumps In London’, September 2018.
Heat pumps are able to provide the greatest energy efficiency and carbon saving benefits when the overall heating / hot water system is designed around their characteristics (e.g. greater efficiency when supplying lower temperatures). For this reason, new buildings offer an opportunity to optimise heat pump efficiencies.
Heat pump efficiencies (SCOP) used in Etude’s study. Source: Etude, ‘Low Carbon Heat: Heat Pumps In London’, September 2018.
When feeding low temperature heat emitters Kensa’s shared ground loop system circulating at ambient temperatures delivers exceptional efficiencies, whilst avoiding the common overheating problems associated with district heating losses entirely. The ambient ‘heat’ circulating the building is low temperature (-5°C to 20°C), and the higher grade heat for each dwelling is produced at the point of use i.e. inside the Kensa Shoebox heat pump inside the flat, and only when required so heat losses are minimised. The pipes are usually still insulated but only to prevent condensation, not to retain heat.
As such, there is no heat loss from the system to contribute to overheating in risers and corridors. Furthermore, as the cold side infrastructure extends all of the way to the individual apartment, it is relatively straightforward to add free passive cooling to the system.
Best practice scenarios should take a long term investment view. Low temperature 4* radiators would deliver even higher efficiencies and lower costs for the end user, the downside being this would result in bigger boreholes and of course associated costs. Yet the borehole infrastructure will last for 100 years. By better investing in the infrastructure, you are delivering the best immediate and long term user experience and the greatest efficiencies. This should be the best practice scenario for all.
Etude’s report raises and counter’s one of the building industry’s perceived challenges to the wide-scale adoption of ground source heat pumps in London, the perception being “its design and integration is considered to be more technically challenging and ‘risky’ than for a gas boiler or a CHP.”
Summarising the design strategies for utilising heat pumps in large scale developments, the GLA’s report advises that Kensa’s ambient temperature shared ground loop array design with individual heat pumps offers substantial advantages, and it should encourage mechanical and electrical design to evolve and embrace new alternatives over gas boiler or CHP:
As an alternative to hot water distribution, a strategy more suited to the advantages of heat pumps would be to distribute water at approximately 10ºC, straight from the borehole array. Small individual heat pumps within each dwelling would be able to feed off the ambient water circuit and generate space heating locally at an optimum efficiency temperature of 35ºC for space heating, and switch to hot water at 60-65ºC as required. This design strategy virtually eliminates distribution pipework heat losses and also enables the heat pumps to operate at a much higher efficiency at times when only space heating is required. Other advantages include:
Heat interface units and heat meters not required for each dwelling;
No central heating plant required (only pumps) allowing for a smaller plantroom;
Lower cost distribution pipework;
Minimal maintenance requirements.
In addition to the advantages of shared ground loop arrays as identified by Etude above, additional technical benefits (the introduction of waste heat, passive cooling, and load shifting) and user benefits (independent control and freedom to switch energy supplier), offer elegant solutions for the designer, developer and the end user.
SAP2012 is ‘out-of-date’, with forecast decarbonisation of the grid affecting Part L performance and exacerbating differences in performance of technology.
Etude illustrate energy demand scenarios based on Part L modelling results for SAP2012, SAP10, and benchmarked predicted energy consumption data, in order to assess the impact of heat pumps, “to estimate the potential actual carbon reduction benefits of heat pumps in operation.”
The below graphs demonstrate Etude’s three scenarios and their impacts on heating system performance against London’s 35% TER target:
SAP2012 – Comparison of Part L improvement results (assuming a carbon factor of 519gCO2/kWh for electricity). Source: Etude, ‘Low Carbon Heat: Heat Pumps In London’, September 2018.
SAP10: Comparison of Part L improvement results (assuming a carbon factor of 233gCO2/kWh for electricity). Source: Etude, ‘Low Carbon Heat: Heat Pumps In London’, September 2018.
Etude benchmarked predicted energy consumption data:
Comparison of Part L improvement results (assuming a carbon factor of 302gCO2/kWh for electricity). Source: Etude, ‘Low Carbon Heat: Heat Pumps In London’, September 2018.
Using the current electricity related carbon emissions in SAP2012 for electricity at 519gCO2/kWh, Kensa’s shared ground loop array ground source heat pump system operating at 320% efficiency (an efficiency determined in Etude’s report based on a range of data sources) produces a carbon saving of 36.9% compared to a gas combi boiler.
The proposed SAP 10 carbon factors – for which all new planning applicants in London must use as of January 2019 – reduces the figure of electricity related carbon emissions to 233gCO2/kWh, similar to those of gas, due to the increasing decarbonisation of the electricity grid with clean, renewable energy sources such as wind and solar PV replacing the burning of coal. The carbon saving for ground source compared to a gas combi boiler would be 70.9%.
Using Etude’s figure of 302gCO2/kWh for electricity Kensa’s ambient temperature shared ground loop array ground source heat pump system would produce a carbon saving of 60.2% compared to a gas combi boiler.
Whichever figure you choose, it is clear that as the UK grid becomes increasingly decarbonised, as is Government’s ambition, the carbon savings of electricity and therefore ground source heat pumps become even greater.
Decarbonisation of the grid will further enhance the efficiency gap between technologies.
Projected carbon factor of heat based on HM Treasury Green Book marginal emission factors. Source: Etude, ‘Low Carbon Heat: Heat Pumps In London’, September 2018.
Heat pumps offer an immediate and significant reduction in the carbon content of heat today and this advantage increases substantially in the future as the electricity grid decarbonises.
The efficiency of ground source heat pumps coupled with grid decarbonisation offer the most compelling low-carbon case and solution for the phase out of fossil fuels and installation of 2.5m heat pumps in homes by 2030, supporting the UK’s move towards zero carbon by 2050.
A cohesive approach to reducing carbon will deliver optimal results.
Energy efficiency reduces demand to the lowest level, heat pumps deliver low carbon heat and PVs play a significant role in offsetting on-site the residual carbon emissions.
Looking ahead to 2030, preliminary analysis indicates that very low levels of total on-site carbon emissions (i.e. approximately 2kgCO2/m2/yr) can be delivered if very high standards of energy efficiency are achieved, an efficient heat pump system is provided and roof-mounted PVs are maximised.
Estimated total CO2 emissions in 2030 (kgCO2/m2 NIA) – high standard of energy efficiency. Source: Etude, ‘Low Carbon Heat: Heat Pumps In London’, September 2018.
For a best practice scenario today using SAP10 figures, developments featuring 10% fabric efficiencies plus 25% additional energy efficiency measures such as solar PV and heat recovery ventilation, alongside a ground source heat pump, would result in a carbon offset price of £871. Compare this to a gas combi boiler where the carbon offset price would be £2,992, equating to a saving of £636,300 on a 300 unit development. (Based on a representative 70m2 new build in London with a 4,200kWh heat demand.)
Demand for electricity in the most ambitious heat pump deployment scenario decreases.
Heat pumps have the advantage of being ‘smart grid’ ready, offering a demand side management opportunity.
Enhanced levels of building fabric efficiency, moderate thermal mass and smart heating controls will not only enhance the efficiencies of heat pumps, but also minimise heat demand and running costs, whilst mitigating impacts on the electricity grid.
The impact of heat pumps on the electricity grid is sometimes quoted as one of the barriers to a greater uptake of heat pumps in London. While the use of heat pumps increases demand for electricity for heating, overall demand for electricity in the most ambitious heat pump deployment scenario actually decreases as a result of improved energy efficiency in other sectors and extensive use of energy storage technologies, driven by time of use tariffs.
Heat pumps should be viewed as part of the solution to balancing demand on the grid, rather than adding to the problem. The energy source for ground source heat pumps – the ground – is stable all year round, which makes it extremely useful for decarbonising the grid. Naturally, ground source heat pumps offer greater grid balancing capabilities than air source heat pumps due to this stable heat source. By using time-of-use tariffs and thermal stores, ground source heat pumps can be turned on and off to not only balance the grid and reduce peaks and troughs, but also to lower the carbon intensity and running costs of the heat pump. By electrifying the grid via ground source heat pumps, your overall investment in electrical generation goes down. Once we get to scale deployment of heat pumps, they will offer even greater grid balancing opportunities.
Ground source heat pumps are as cheap to run for end users as gas boilers.
Comparison of predicted heating costs for the resident of a 2-bed energy efficient apartment. Source: Etude, ‘Low Carbon Heat: Heat Pumps In London’, September 2018.
The report states:
Compared to the cheapest non-heat pump solution, a communal ground loop with individual heat pumps is the cheapest overall and is very efficient.
Carbon savings and running costs will be even greater for ground source heat pumps compared to gas once smart controls, thermal storage and time of use tariffs come into play, as the heat pumps could operate at times when the grid has the lowest emission rates, or when the costs for electricity are lowest.
Efficient systems working in harmony with time of use tariffs and storage also protects against future energy price rises, and reduces future fuel poverty, as the report highlights:
335,000 households are affected by fuel poverty in London. The issue of affordability of heating in new build should remain at the forefront of any strategic decision regarding low carbon heat. As electricity decarbonises we should remember that it remains an expensive form of energy and that its prices may rise in the future. It will therefore be important to make sure that consumers using electricity for heat generation use efficient systems and use electricity when it is cheaper by building in sufficient thermal and electrical storage.
Scale and optimised design and procurement reduce costs.
Referring to the ‘communal ground loop connected to individual heat pumps’ scenario, the report states that:
Potential additional capital costs compared with ‘business as usual’ are likely to be small in comparison to the total project costs (0-3%) and should be seen in conjunction with their potential benefits including carbon and air quality. Research commissioned by the Government in 2016 also suggests that costs could reduce by 15-20% in future.
Referencing Kensa’s ground-breaking scheme at Kensa as a model of this scenario, the report continues:
Costs of <communal ground loop connected to individual heat pumps> could be significantly reduced with scale and if design and procurement are optimised (as it is the case for the eight tower blocks in Enfield – please refer to associated case studies). Costs of heat pumps are also generally expected to reduce over time as demand increases and the supply chain develops.
Yes, ground source heat pumps get even cheaper with scale – introduce waste heat and cooling capabilities into the equation, and the costs get even lower.
The final word.
To realise the scale of the UK’s heat pump ambitions, let’s put some of Etude’s market stats into context.
In Norway 95% of new heating systems are heat pumps, compared to just 1% in the UK.
There were approximately 1 million heat pump units sold in the EU in 2016:
- France: >220,000 units
- Italy: >180,000 units
- Sweden: >100,000 units
- UK: 20,000 units!
The report outlined the key milestones to meet the UK’s carbon emission reduction targets:
- 2030 – 2.5 million heat pumps should be installed in new homes and low carbon heat networks should deliver around 40 TWh across the UK.
- 2035 – Gas boiler installations should cease.
- 2050 – Heat should be delivered in non-hydrocarbon forms.
- 2050 – The Mayor’s target for London to become a zero carbon city.
The Committee for Climate Change makes clear that more decisive policies are required if the Committee’s minimum expectation of 2.5m heat pump installations by 2030 is to be achieved. That ambition requires some transformational measures. Whereas progress to date has been somewhat reliant on the ‘carrot’ of subsidy support, the ‘stick’ of Building Regulations compliance is about to apply. (Read Kensa’s blog ‘Counting the Capital Cost of Carbon Compliance’ here)
With aims to cease gas boiler installations by 2035, and given the wide concern regarding the suggested conversion of the gas grid to hydrogen, we should at the very least stop adding to the problem by extending the gas grid to new developments now.
Next in the series:
The ‘Low Carbon Heat: Heat Pumps In London’ report delves further into the market perception of heat pumps. Forthcoming blog posts from Kensa will draw on each of these to explore and counter common misconceptions, including:
- Building industry perceived challenges
- Reasons people do not specify heat pumps
- Consumer concerns with heat pumps