Introduction

Harbour Project Management recognised that heat networks often focus on large cities, leaving behind residential areas where alternative low carbon heating solutions such as air sourced heat pumps are very challenging (within terraced streets for example).

We proposed the idea of ‘small repeatable heat networks’ to Innovate UK, who then provided funding to explore the concept as part of the Liverpool Net Zero Living programme.

The main aims of our innovative heat network approach were to:-

• Use repeatability (cut and paste design) to achieve efficiency and economies of scale.
• Focus on unlocking the use of geothermal heat in the UK.
• Reduce future strain on local electricity networks.

The aim was to compare the use of ‘small repeatable heat networks’ against an alternative option, being the installation of air source heat pumps within each individual building. 

We assembled and led a team of experts to:-

• Develop the concept.
• Test the concept in a sizable case study area.
• Finalise the concept.
• Test how it would work at different scales (city, town, village).
  

A series of very detailed reports have been produced by the project team, the content of which is far too much to share here.

The Concept

The concept for ‘small repeatable heat networks’ can be described as follows:-

• Waste and natural heat is collected and distributed through an enhanced ambient loop. A particular focus is placed upon geothermal heat extraction.
• The enhanced ambient loop provides a constant supply of 40°C water to up to 20 local energy centres.
• The local energy centre boosts the 40°C water to 70°C and distributes the heat to customers through the local distribution network.
• Each local energy centre typically serves the equivalent of 1,200 homes.
• Customers receive heat at 70°C through a heat interface unit (HIU), which replaces their existing boiler and provides all of their heating and hot water.

For a more detailed description of the concept a video has been prepared:-

Testing The Concept

To see how the concept might perform in the real world, an area of Liverpool around Newsham Park was selected. This is a sizable sample area of over 5.5km², containing more than 18,000 buildings. The concept was applied to the sample area. This included locating energy centre sites, finding and modelling geothermal heat extraction, visiting and assessing sample buildings for pipework connections, assessing electricity grid capacities, designing pipework routes etc.

This phase of the research project aimed:-

• To test the conceptual model for ‘small repeatable heat networks’ in a representative sample area of circa 18,000 building connections. The idea was that if it can be shown to work in this very challenging area it would stand a good chance of being applied in other areas.
• To test the use of an ‘enhanced ambient loop’ fed by geothermal heat in a real location.
• To explore the practicalities of delivering energy centres and heat distribution pipework in local areas. This included finding energy centre sites and designing sample local network areas.
• To understand how to connect the network to existing residential areas, in particular rows of existing terraced homes.
• To provide a real-world example of the impact of the concept to the local electricity network.

Our approach was to:-

• Obtain local heat demand data by using the DESNZ produced national zoning model (NZM).
• Commission a Liverpool specific geological report to understand the local geothermal potential.
• Develop a detailed geothermal heat extraction plan based on local geological conditions.
• Visit a range of residential properties and prepare detailed costed options for network connection.
• Work with the District Network Operator (DNO) to understand electricity grid impacts, including the costs of local network upgrades required for both the concept and an alternative solution.
• Prepare a network design and 40-year techno-economic model.
• Feed the lessons learned into an updated conceptual model.

The Final Conceptual Model

A detailed report was produced to capture the concept and the findings from the Newsham Park case study. Overall, the model proved viable and worthy of further development. The key finding were that:-

• The concept performs well financially when compared over a 40-year period to the counterfactual option of air source heat pumps in each building:-

• The above table assumes that all buildings in the area connect, and that no work is done to reduce heat demand through insulation and other measures. To stress-test the concept, the calculations were re-worked to assume only 80% of buildings connect. In addition, 80% those buildings reduce their heat demand by 40% over a 25-year period. This changes the results as follows:-

• In relation to the use of geothermal heat and an enhanced ambient loop, the solution appears to be both technically and financially viable as a long-term investment. The below table shows the breakdown of the main LCOH figures. As can be seen, the geothermal heat and enhanced ambient loop elements are only a small part (17%) of the overall cost of the network:-

• The local connections and local distribution network accounted for more than 50% of the overall cost. The vast majority of this is due to the high costs used in the assumptions for excavation of tenches for pipework. An example of this can be seen the the below table, which breaks down the assumed cost to bring a connection from the pipework main (in the middle of the street), into the customers home:-

• As can be seen, for a terraced home, £9,600 of the £16,508 cost is for the external works. Of this £9,600 the largest cost is digging a shallow trench 6m in length (£7,488). The high cost of excavations required for pipework installation is an area where large savings could be made, significantly improving the cost effectiveness of the concept. This is an area worth of further exploration.

• In relation to local grid impact, the work has demonstrated a significant potential for reductions in electrical demand, in particular peak demand. The below table highlights the results for the Newsham Park area:-

Scaling the Concept

The project team applied the concept to the following three scales:-

• City scale (entire Liverpool area).
• Town scale (population of 35,000).
• Village scale (population of 2,000).

For the city scale work, a high-level masterplan as completed and modelled for the whole Liverpool area. This covered over 180,000 buildings, resulted in 15 separate ambient loop networks with their own location specific geothermal heat inputs, and 193 local energy centres.

A detailed report was prepared, the very high-level summary being that the concept seems to perform equally well at all three scales. This suggests that ‘small repeatable heat networks’ could be viable for village, towns, and cities across the UK.