District Heating

Jump to:

• What is the best type of district heating?

• What is a Shared Ground Loop Array?

• What are the advantages of using Shared Ground Loop Arrays?

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

• What projects would benefit most from Shared Ground Loop Arrays?

• How much do Shared Ground Loop Arrays cost?

• What funding is available for Shared Ground Loop Array schemes?

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

• Why is the large-scale deployment of ground source heat pumps important?

• FAQs

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 distribution pipework –  an ambient-temperature 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. These low-carbon time periods also tend to correlate with lower costs.

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 – the ambient-temperature loop. 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.

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 vs. traditional district heating

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.

Shared Ground Loop Array schemes also create external funding opportunities for fully-funded ground arrays and ultra-low-cost heat pumps. For example, the split ownership model could mean that developers could separate the cost of the heat pumps from the ground array. Through this scheme, an external investor could fund the ground array infrastructure to cover the most expensive aspect of the project. In return, the investor can charge connection fees if they wish. Meanwhile, the developer or property owner benefits from a cheaper project, with all the efficient advantages of ground source.

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):

* Based on SAP 10 carbon figures and £95 per tonne of carbon.

What funding is available for Shared Ground Loop Array schemes?

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 charge connection fees in return 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.

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.

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.

*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)

Why is the large-scale deployment of ground source heat pumps important?

Ground source vs. other low-carbon heating systems

It is proven that water source and ground source heat pumps are the most efficient renewable heating systems available, and this superior performance is important when the technology is deployed at scale. The methods used to decarbonise and electrify heat will have profound implications for supply and demand and will influence factors such as how many power stations we need.

The flexibility of ground source heating

The main benefit to the electricity grid of installing ground source heat pumps – connected to Shared Ground Loop Arrays with an ambient-temperature loop – is flexibility. Ground source heat pumps can run at any time of day or night without loss of efficiency.

Smart controls, time-of-use tariffs and energy storage mean the system can be working when the wind is blowing, or at night. This is known as ‘load shifting’ to when the grid can best support demand, and when electricity is at its lowest in cost and carbon. The heat generated can be stored and used whenever the home needs it.

Load shifting to save further costs & carbon

A ground source heat pump is best placed to participate in this type of ‘load shifting’, as they are quiet and unlikely to disturb anyone during night-time or early morning hours. A homeowner could recharge their hot water cylinder through the night when demand and price are lowest – ready to use the next day.

Another reason is that the temperatures below ground remain constant no matter the time of day or season.

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.

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 to get started.

*17kW not C&N, but often still eligible to protect consumers from upgrade costs.