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District Heating

District heating with ground source heat pumps connects communities to a low-carbon future. Helping to achieve zero emissions in the UK by 2050, Kensa’s Shared Ground Loop Array is the scalable and sustainable, low-cost and low-carbon alternative to traditional district heating.

What is district heating?

District heating is a system that distributes heat to numerous properties. In traditional networks, heating and hot water is delivered to multiple properties from a centralised system.

Kensa’s Shared Ground Loop Array is our decentralised approach to Fifth Generation District Heating. In Shared Ground Loop Array schemes, individual Shoebox ground source heat pumps are installed into separate dwellings and connected through clusters of communal district networks. Perfect for social housing and developments.

Kensa's form of Fifth Generation District Heating using a Shared Ground Loop Array network

What is the best type of district heating?

The most efficient type of district heating system is known as Fifth Generation. This is the latest, most innovative version of district heating. Going a step further, Fifth Generation District Heating schemes featuring Shared Ground Loop Arrays makes for the best type of low-carbon district heating.

What is Fifth Generation District Heating?

A Fifth Generation District Heating and cooling network is a thermal energy supply grid, which circulates low-grade heat sourced from the ground, the air or waste heat processes, around a network of pipes to heat pumps. The heat pumps then upgrade this heat to deliver low-cost and low-carbon heating. The system can also provide cooling.

The lower the temperature of heat distributed through a district heating network, the higher the system’s efficiency. Generations of district heating have evolved as temperatures circulating the district network reduce, thus improving efficiencies.

Heating efficiency through the generations:

  • First Generation District Heating: Steam (120°C)
  • Second Generation District Heating: Boiling water (95°C to 100°C)
  • Third Generation District Heating: Hot water (70°C)
  • Fourth Generation District Heating: Low temperature flow (50°C to 60°C with a return of 35-40°C)
  • Fifth Generation District Heating: Ambient temperature flow (-5°C to 20°C with heat pump boost)

What are the benefits of Fifth Generation District Heating?

  • The ambient loop does not suffer from heat losses, improving system efficiency, reducing construction costs and combatting overheating in buildings.
  • The low temperature of the ambient loop allows for the exploitation of waste heat and other energy boosters to enhance heating and cooling efficiencies.
  • Fifth Generation District Heating supports the electrification and decarbonisation of heat, allowing integration with smart energy systems and opportunities for aggregated energy demand supply.
  • Heat transfer via heat pumps removes the use of combustion heating technology, benefiting air quality by reducing pollution, significantly reducing carbon emissions and improving safety.

What is the lowest carbon form of district heating?

District heating with ground source heat pumps

Ground source heat pumps have emerged as a simpler, more effective and efficient heating system compared to traditional district heating measures such as gas Combined Heat & Power (CHP).

SAP 10.1’s proposed reduction of electricity’s CO² factor from 0.519 kgCO² / kWh to 0.136 kgCO² / kWh shows that, as a result of rapid decarbonisation of the National Grid, even the small portion of power consumed by ground source is lowering in carbon.

Fifth Generation schemes featuring ground source heat pumps help to meet CO2 reduction targets. These schemes allow progression from fossil fuel heating to a system that efficiently exploits the decarbonisation of electricity. Opportunities such as dynamic electricity tariffs make this possible, as ground source heat pumps can shift times of consumption to when the grid has its lowest carbon supply, from renewables such as wind and solar.

Combining with other renewable technologies

The effectiveness of ground source heat pumps in Shared Ground Loop Array schemes can be further enhanced when combined with other renewable technologies, such as:

  • Phase change heat storage.
  • Town scale battery storage.
  • Utilising cheap, low carbon electricity at low demand parts of the day and night.

What is a Shared Ground Loop Array?

Kensa’s Shared Ground Loop Array is an ultra-efficient form of Fifth Generation District Heating. The scheme incorporates clusters of communal ground arrays, such as boreholes or slinky trenches, which deliver heat to the district pipework. This ambient heat is then fed to individual ground source heat pumps inside each dwelling.

How do Shared Ground Loop Arrays work?

Kensa’s Shared Ground Loop Array design features a ground source heat pump per dwelling, which are each connected to a Fifth Generation District Heating ambient loop. This loop receives heat energy from the clusters of ground arrays.

The clusters of ground arrays, usually boreholes, transfer heat temperatures of -5°C to 20°C from the ground to the communal ambient loop, which feeds ambient temperatures to each individual heat pump. The ground source heat pump, typically a Shoebox, then upgrades the ambient heat energy from the ground to provide independent and controllable heat to radiators or underfloor heating for space heating, and a cylinder tank for hot water.

How does it work for each dwelling?

Every shoebox heat pump in each dwelling features a circulating pump, which pushes the heat transfer fluid through the borehole. If one dwelling within an entire building requires heat, the circulating pump has enough power to deliver the flow rate that one heat pump needs – providing heating on demand.

What are the advantages of using Shared Ground Loop Arrays for district heating?

The Renewable Heat Incentive

Shared Ground Loop Arrays connecting two or more dwellings with ground source heat pumps qualify for the Non-Domestic Renewable Heat Incentive (RHI) and Energy Company obligation (ECO) funding.

Affordable heating bills

Ground source heat pumps produce 3 to 4kWh of heat energy for every 1kWh of electrical energy used, making them 300-400% efficient. A typical boiler is 90% efficient.

Minimal maintenance

With a design life of 20 years, ground source heat pumps don’t require annual servicing or maintenance.

Independent heating

As a unit is installed into each property, end users are in complete control of their own heating and energy bills. They can easily switch between energy tariffs, and only have to pay for their own heat consumption.

Single appliance

Shared Ground Loop Arrays do not require any additional heat source or appliance other than the ground source heat pump; the unit provides 100% of the properties heating needs all year round.

Year-round supply

The ground temperature remains a stable and reliable 8-10°C all year round. Compare this reliability to air source heat pumps, which are impacted by external fluctuating air temperatures, creating higher bills when you need heat the most.

No combustion

Avoiding any need for flammable gases, Shared Ground Loop Array networks provide a safe and worry-free heating alternative to traditional district heating schemes. Conforming to fire safety and building regulations, a ground source heat pump delivers heating and hot water with peace of mind to flats, tower blocks and high-rise buildings.

Lower emissions

Because a ground source heat pump extracts so much free energy from the environment, CO2 emissions are lower than any other type of heating system.

Free cooling & no overheating

With heat being generated at each dwelling’s point of use, the heat circulating the property is low temperature, so there is no heat loss contributing to overheating in risers and corridors.

The use of ground arrays with ambient loops offers an unparalleled opportunity for schemes to utilise waste heat, as well as provide free passive cooling for a comfortable living environment all year round.

Smart cities

Ground source heat pumps with Shared Ground Loop Arrays offer unique benefits when incorporated with smart energy grids to balance demand, costs and carbon.

How are Shared Ground Loop Arrays better than District Heating systems?

Designing out district heating issues

Kensa’s ambient Shared Ground Loop Arrays design out the issues of traditional district heating and heat networks, which can be energy-wasting, financially front-loaded systems. Such networks tend to be admin heavy, liable to heat provider exploitation, and require large amounts of space for plant room equipment and a backup system in case of failure.

When it comes to tenant wellbeing, traditional networks can be wasteful and pricey – not only do the heat losses have to be paid for, but overheating can occur in risers and corridors from distribution pipework. Central plants require split billing, highly specialised servicing and the restriction of a single energy provider.

Shared Ground Loop Array schemes leave behind unsightly central plants, complex controls or expensive heat losses. Instead, tenants have with their own unit, their own energy bills and simple controls. Other than minimal, straightforward maintenance, there is no mandatory servicing requirement thanks to the safe, non-combustion technology.

Shared Ground Loop Arrays compared to traditional district heating

Shared Ground Loop ArraysTraditional Heat Networks
+ Ambient loop - no heat losses- Heat loss through network
+ No overheating - no requirement for expensive pipe insulation- Overheating in risers & corridors
+ Independent billing- Requires split-billing
+ Independent heat - freedom to switch suppliers- Single heat energy provider
+ Receives Non Domestic RHI- Complex funding claims
+ Deemed heat for RHI - no heat meters- Networked heat metering
+ No plant room - individual heat pump per dwelling- Large & unsightly central plant
+ Lowest bills & low standing charges- ESCO purchases energy
+ No servicing & minimal maintenance- Highly specialised servicing
+ Robust and reliable- Back up system required
+ Carbon compliant - easier & cheaper SAP10 compliance
+ No emissions
+ Free passive cooling
+ Integration with existing internal controls & standard plumbing
+ Integration with smart controls
+ Multiple heat source options
+ Integration with waste heat
+ Inter seasonal heat storage
+ Flexible and scalable
+ Heat metering and billing regulations exempt

How are Shared Ground Loop Arrays different to Fifth Generation District Heating systems?

Although Fifth Generation District Heating and Cooling networks remove some of the negatives of traditional district heating schemes, such as reducing heat losses and the need for energy centres, Kensa’s ambient Shared Ground Loop Arrays go a step further.

No central plant

By providing an individual heat pump to each dwelling, shared ground loop systems remove the need for a plant room, complex billing and restrictive energy supplier contracts, safeguarding against whole system failures. They can even use a ground array to provide flexibility for integrating additional energy sources and permitting inter-seasonal heat storage.

No overheating

Kensa’s decentralised Shared Ground Loop Array approach results in an even more efficient system, as high-grade heat is only generated at the point of use by the ground source heat pump inside the home. However, in traditional Heat Networks and some Fifth Generation District Heating systems, heat is generated in a central plant and circulated inside the building continually. This leads to heat losses and overheating, particularly in risers and communal areas.

Ability to passively cool

Furthermore, as the Shared Ground Loop Arrays’ cold side infrastructure extends all the way to the individual dwelling, it is easy to add passive cooling to the system.

What projects would benefit most from Shared Ground Loop Arrays?

The unique Shared Ground Loop Array design allows property owners and developers of two or more dwellings to take full advantage of ground source heat pumps. First and foremost, such projects can tackle issues such as fuel poverty and achieve easier and cheaper carbon compliance.

Providing rewarding returns, Shared Ground Loop Array schemes qualify for Non-Domestic Renewable Heat Incentive (RHI) payments in both new-builds and existing housing stock. They also create external funding opportunities for fully-funded ground arrays and ultra-low-cost heat pumps.

Housing associations

Alleviating fuel poverty and assisting with compliance, Kensa’s shared ground loop design helps social landlords to finance affordable and low-carbon heating replacements using ground source heat pumps. For high-rise buildings featuring gas combi boilers, where like-for-like replacements are no longer permitted, ground source heat pumps offer a compliant and viable non-combustion alternative.

Kensa ground source heat pumps district heating Shoebox heat pump diagram

See more about social housing

Developers

Ground source heat pumps with Shared Ground Loop Arrays offer the affordable way to achieve carbon reduction targets over and above building regulations. They are ideal for developers working to achieve more than 30% carbon savings compared to building regulations.Shoebox minus background

See more about developments

How much do Shared Ground Loop Arrays cost compared to traditional district heating?

Based on a 1,500-unit new build development, compare the financial and carbon costs of a Shared Ground Loop Array and ground source heat pump system against a gas CHP district heating system with HIU (Heat Interface Units):

 GSHP with shared ground loop arraysGas CHP (incl. infrastructure & HIU)
Installation cost£8,000£6,500
Carbon offset*£871£4,093
Total£12,556,500£15,889,500
* Based on SAP 10 carbon figures and £95 per tonne of carbon.
Discover typical project costs

Communal ground loops with individual heat pumps are the most economic solution of all (at approximately £500/yr) and are also compliant with London’s key objectives in terms of air quality and carbon emissions. They combine several advantages: they are very energy efficient and do not require dedicated heat metering and billing.

Greater London Authority (GLA), ‘Low Carbon Heat: Heat Pumps in London’ (September 2018)

What funding is available for Shared Ground Loop Array schemes?

The Non-Domestic RHI

The district nature of Shared Ground Loop Arrays qualifies them for 20 years of guaranteed quarterly income via the Non-Domestic RHI. This guaranteed tax-free income provides a return on investment, creating the opportunity for developers and property owners to confidently invest in Shared Ground Loop Arrays.

Non-Domestic RHI payments for residential properties linked to shared ground loops are paid on the deemed heat consumption taken from the property’s Energy Performance Certificate (EPC). This reduces capital costs (as meters are no longer needed) and eliminates the administrative burden of quarterly readings and submissions.

Ground array funding

To lower the upfront installation cost, property owners, developers or social landlords can attract external funders to own the ground array and receive the RHI in return. The investor can even choose to charge connection fees if they wish. This is known as split ownership.

The ECO

Importantly for the retrofit sector, district ground source systems can attract funding from the Energy Company Obligation (ECO). Particularly where electric heating or oil are being displaced, landlords can benefit from an attractive capital subsidy in addition to long-term RHI payments.

Find out more about funding

What heat sources can be used for Shared Ground Loop Arrays?

Shared Ground Loop Arrays harvest heat for ground source heat pumps using one of the following popular forms of ground array collectors:

Ground sources

  • Boreholes. Deep holes are drilled to depths of 100m to 250m, and collector pipes are set in grout to collect the heat from the surrounding geology. This is particularly useful where large areas of ground are not available. Boreholes are the most common ground array for Shared Ground Loop Arrays.
  • Horizontal collector pipes. Slinkies (coiled pipe) buried in trenches 1 – 2m below ground is a cost-effective and easy-to-install means of collecting heat without any specialist equipment. However, a large area of land is needed – approximately 300m² for an average 3-bed family home.

Water sources

  • Surface water, closed loop. Water is an especially efficient heat source. This is an ideal option for developments next to rivers or lakes, where pond mats can be positioned in the body of water to extract the heat.
  • Seawater, open loop. Seawater is pumped from the sea and the heat is extracted via a land-based heat exchanger.
  • Aquifer or mine water. Extract groundwater from an underground aquifer or mine – this can produce super-efficient systems, as mine water temperatures are typically around 15°C to 18°C.
Mine water for a ground source heat pump

Waste heat sources

  • Waste heat from data centre cooling, heat from underground transport tunnels, air handling units, space cooling, process cooling, or PV-t.
  • The ambient loop offers flexibility to integrate additional energy sources to act as energy boosters, reducing the cost of the ground array.
  • When ambient loops incorporate heat from waste heat sources, the load profile for the heating may not match that for the cooling requirement; the ground array, therefore, acts as a natural ‘heat store’ allowing for inter-seasonal heat storage.
Find out more about heat sources

What if my project isn't suitable for ground arrays?

Air source heat pumps, dry air coolers (a fan) or sources of waste heat can also act as primary heat sources for ambient loops if a ground array is not possible, however, they require secondary appliances inside the property to manage and deliver the heating and cooling. Ground source heat pumps with Shared Ground Loop Arrays require no additional appliances.

In some cases, where a ground array may not be possible, ground source heat pumps can work with secondary appliances and no ground array, for example, using air source heat pump dry air coolers as the heat source. However, the ground array provides design robustness and greater opportunities. The constant temperature of the ground provides stability unlike air temperature fluctuations and depending on the geology, the ground array provides the opportunity for natural energy storage.

Kensa can provide a full design review to establish your options if ground arrays may not be feasible.

Share your project plans

What is the best ground source heat pump for Shared Ground Loop Arrays?

Shoebox Heat Pump

Shoebox ground source heat pump 3kW product banner to scale

Developed with Shared Ground Loop Arrays in mind, Kensa’s super-small Shoebox heat pump is typically installed under the kitchen sink or in an airing cupboard.

The 3kW Shoebox heat pump works exceptionally well in new build homes up to 75m2, where the excellent fabric insulation and airtightness specifications mean the peak heating load is very modest.

Kensa’s 6kW Shoebox Twin heat pump suits larger new-build properties or retrofit developments where the build condition may demand a higher peak heating load.

Evo Heat Pump

Evo ground source heat pump product banner to scale

The latest evolution in Kensa’s ground source heat pump product ranges, the Evo series offers the highest heating efficiencies.

Alongside the latest advances in acoustic insulation, the Evo’s elegant design complements the interior of the most stylish homes.

What is the impact of heat pumps with Shared Ground Loop Arrays on the electricity grid?

The energy source for ground source heat pumps – the ground – is stable all year round, which makes it extremely useful for decarbonising the electricity 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 storage, 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; a heat pump is now a key component to a broader household energy system.

By electrifying the grid via ground source heat pumps, overall investment in electrical generation goes down. Once we have achieved widescale deployment of heat pumps, they will offer even greater grid balancing opportunities.

average cost and carbon intensity of electricity graph - impact of heat pumps on the electricity grid*Daily average cost and carbon graph: Base electricity charges based on Sheffield averaged on the Big Six once a month – average electricity cost per kWh (www.ukpower.co.uk/home-energy/tariffs-per-unit-kwh, www.nottenergy.com/energy_cost_comparison). Octopus Agile Tariff (average over 24hrs). Average CO2/kWh over 24hrs in winter (www.carbonintensity.org.uk)

FAQs

Got a question about Shared Ground Loop Arrays? Read through some of the most common questions below. If you can’t find the answer to your question, please contact us or send us your project details for a bespoke quote.

Looking for advice on a district heating project?

Our sister company, Kensa Contracting, specialises in Shared Ground Loop Array schemes. They provide a fully MCS-accredited service with everything from tenant liaison, to project management and installation support.

Get advice from kensa contracting

Want to learn more about Shared Ground Loop Arrays?

Digging into the depths of district heating with ground source heat pumps, Kensa offers Continuing Professional Development (CPD) on the subject of Shared Ground Loop Arrays. Get in touch with Kensa to get started.

Contact us

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