Energy Superhub Oxford Live Blog

Follow our smart renewable heating trial

First Phase | Heat


Follow the pioneering trial of smart renewable heating with Stonewater Housing Association and Kensa Contracting on this live blog page!

Part of the £41m Energy Superhub Oxford (ESO) project, this blog charts our journey as we upgrade the heating of 60 homes in Blackbird Leys, Oxford. Individual Kensa Shoebox heat pumps will be installed into each home and integrated with smart controls and time-of-use tariffs to cut costs and carbon for residents. This is the first phase of the ESO project, where homes are set to feature smart renewable heating over the next two years.

The project overview

Installations in Blackbird Leys:

Individual Shoebox ground source heat pumps will be retrofitted into each property and connected to a communal ground array, displacing 56 night storage heaters and 4 gas boilers.

The heat pumps will work together with behavioural-learning controls to produce space heating and hot water at the optimum times based on the individual householders preferences. To deliver this as cost effectively and sustainably as possible, the systems will access flexible tariffs and automatically run the heat pumps when electricity is at its cheapest and lowest carbon.

This ‘load shifting’ will help to stabilise the grid, without compromising on customer comfort, and will become an increasingly important component for the mass deployment of heat pumps. Residents will benefit from clean, renewable heat, and are expected to realise demonstrable savings on their heating bills, compared to a standard ground source heating system without smart controls and automated load shifting.

Key facts:

  • 60 Kensa Shoebox ground source heat pumps
  • Smart thermostats – create the perfect heating profile for each property based on the occupant’s preference and building’s fabric
  • Time-of-use energy tariffs – 100% green electricity with dynamic plunge pricing
  • Heat optimisation software – takes a day-ahead forecast of half-hourly electricity costs and automatically shifts the operating times – allowing occupants to make savings from dynamic tariffs without having to change their behaviour.

Live blog milestones:

Follow our blog to stay up to date with this innovative world-first project with Kensa Contracting and consortium partners Oxford City Council, Pivot Power, Habitat Energy, Invinity Energy Systems and the University of Oxford.

Over the coming weeks, we will bring you live updates as they happen. Click the titles below to follow the updates.



Design elements of a ground source heat pump project are extremely important. At this stage, Kensa engineers undertake a detailed survey of each property to ascertain building fabric, which inputs into a room-by-room heat loss calculation. Using the kWh figure from these calculations and the specified efficiency of the product - in this case, a Shoebox heat pump - it is possible to calculate how much energy is required from the ground, and consequently, the depth and number of boreholes required.

In a different situation, boreholes would be drilled to approximately 200m to capitalise on the drill rig placement and ensure boreholes are kept far apart as possible - generally, they would be spaced apart at an average distance of 12m. However, this will not be possible on the Oxford sites.

Oxford has a long and well-documented history of artesian water pockets. Artesian water is a body of water stored below ground and surrounded by an impervious layer of geology, which keeps the water in place and under pressure. When drilling into these pockets, water can be released under pressure, potentially causing fountains of water at a height dictated by the water pressure. This can slow down operations, and wherever possible, Kensa Contracting avoids or designs out these risks.

Geological Assessment - Blackbird Leys

FormationClassification Conductivity (W/mK)Thickness (m) Depth bgl (m)
TopsoilN/AN/A< 10
Beckley Sand MemberSANDSTONE2.31212
Temple Cowley MemberSAND & SILTSTONE2.21426
West Walton FormationSilty MUDSTONE2.11945
Oxford ClayMUDSTONE1.688133
Kellaways FormationSILT, SAND & MUDSTONE2.14137
Great Oolite Group LIMESTONE2.846183

A detailed geological assessment from Genius Energy Lab suggested that the pocket of artesian would be at a depth below 137m. The Environment agency prefers that installations stick to the Oxford Clay formations and do not penetrate the layers below. Therefore, engineers have designed the system so that the boreholes will not be installed below this depth. This means more boreholes are needed, so twice as many have been installed than would otherwise be required.

Furthermore, to place these on-site, the separation has been reduced to 10m, which again, means the project needs more boreholes. Otherwise, it would mean extracting a fixed amount of energy from a smaller piece of ground. Although this design should mitigate the risk of artesian, Kensa will also ensure there are the necessary materials to manage the artesian if encountered - however unlikely it may be. All boreholes are monitored for the geological banding to ensure that Kensa engineers encounter the as-expected conditions that impact the thermal properties of the design.

Cudderson Way - Borehole Design - 07.08.2020


Kensa Contracting engineers encountered artesian water (a sub-surface water body) early on in the drilling process. This was at a slightly shallower depth than expected, but they are now in the process of re-designing the borehole arrays. They have a solution, but they need to confirm it in writing for plans. In the meantime, the artesian has been sealed and this borehole will form part of the array as planned. A re-design of the borehole arrays is being planned with input from geology, drilling, project management, design, and the director. Confirmation by site visit tomorrow (13/08/20).


The Project Manager has measured up and relocated some boreholes as part of project re-design.


Those on-site are meeting with the design team and geologist to confirm the re-design.

Operating safely through Covid-19


Due to the current pandemic, Kensa Contracting and our client, Stonewater, have been careful to screen all customers to make sure on-site engineers and subcontractors are not undergoing any work or installations which may adversely affect the health and wellbeing of tenants, staff and partners.

On this and other projects, Kensa Contracting waits for tenants who are shielding to declare themselves fit and comfortable enough to allow installers into their home to carry out internal installations. A rigorous and flexible set of risk assessments and method statements has been developed with the input of stakeholders to ensure Kensa Contracting delivers the safest possible outcome.


Researchers from Oxford Universities are being careful to wear face coverings and carry out their work at a social distance outside the property.



Preparation of the documentation must be planned and authorised by the local authorities, Oxford City Council and Oxfordshire County Council. They will authorise the use of nearby spaces and approval for lawful development certificates, which apply to this type of project.

All tenants are contacted to explain the process of installation, what the project entails, and of course, to see if they have any questions. A booklet is supplied by Kensa Contracting for the tenants to refer to, and they always have the opportunity to speak to Kensa or, once the project commences, to speak in person to the Kensa Contracting representative on-site.

Prior to any work commencing on-site, the drilling rig and other equipment need to be delivered. The equipment usual moves straight from a previous project, and often, from a site a long way off - such is the demand on drilling rigs and their expert teams in general. This is why Kensa Contracting relies on partner Geodrill, as they have supported Kensa for many years.

As well as making sure the necessary equipment is in place, it is essential that all of those working on-site are properly briefed and inducted for safety purposes. That way, they know precisely what is required of them in terms of the project delivery requirements. During the planning phase, there are several iterations and modifications of plans, so the latest version must be in use by everyone. The client, Stonewater, must be kept updated on progress and approve any changes.

Compound area, storage & welfare - Cuddesden Way - 10.08.2020

Summer 2022

A University of Oxford study of the ESO ground source heat pump installations noted most tenants reported saving money, in many cases around 50%, thanks to the Ground Source Heat Pumps in comparison to running costs of their previous direct electric night storage heaters. Initial trials of load shifting the ground source heat pumps have been successful, demonstrating the concept works in practice, whilst maintaining the comfort levels of the residents.



Today, drilling began for the first heat pump borehole. As part of the drilling process, subcontractors use a Mud Puppy - a machine which filters and separates mud and water from larger drilling. Drilling can be unpredictable, but Kensa engineers learn from the geology they encounter and use it to their advantage.


Drilling recommences

Drill rig - Cuddesden Way - 11.08.2020


Drilling is complete on the first borehole. The drilling rig moves to the location of the second borehole.


Drilled to depth today. Extreme care was taken when approaching the previous level of artesian.


Today, the loop was dropped in and grouted. The loop is the term used for the pipework in the borehole and grouting is a thermally-enhancing material. Grouting provides good thermal contact with the pipes in the ground array and the surrounding geology, maximising the heat obtained for the system.

Drilling also commenced on the third borehole. Oxford City Council, Innovate UK, and Oxford University were shown the drilling operation during the day.


Drilling of the third borehole at Cuddesden Way is almost complete.

A team of three drilling specialists were required to operate the drill and associated plant and equipment. This included a telehandler for lifting and moving equipment and a Mud Puppy. The specialists loaded each of the drilling rods onto the rack, to be later connected to the drill.

Drilling Specialists operating the drill and associated plant and equipment - 21.08.20


Two further boreholes have been drilled. Kensa Contracting's subcontractors will prepare and hopefully commence drilling the sixth borehole prior to the bank holiday weekend.


Borehole number six has been completed. A total depth of 544 metres across all of the boreholes has been drilled so far. Three more boreholes are to be drilled at Cuddesden Way.


This is the seventh borehole drilled so far; the loop is prepared before being dropped into the borehole. The bottom of the loop is weighted to ensure it reaches the total depth, prior to which it is cut to the required depth. After this borehole has been grouted and tested, the drillers will move onto preparations for the next borehole.

Loop being prepared prior to dropping into the heat pump borehole - 3.09.20


The eighth borehole at Cuddesden Way has been drilled and the drilling team are completing the grouting of the borehole.


Drilling at Cuddesden Way has been completed. The next stage is for grounds workers to attend and connect all the boreholes together to make two borehole arrays: one of five and one of four boreholes. Each array will be fed under the surface to a central manifold and from there to a position outside the properties. In the meantime, the drillers are moving to Balfour 3 and preparing that location for drilling. The client, Stonewater, has arranged for a local company to remove part of a hedge to allow access for the drilling rig and other equipment at Balfour 3.


The first borehole has been drilled at Balfour 3, including dropping in the loop and grouting.


The rig has now moved to Balfour 3. Since drilling commenced there on Monday (14.09.20), two boreholes have been completed. From the photograph below, it’s possible to see that the drilling team have had to use their skill and experience to manoeuvre the drilling rig precisely into position in order to work in the limited space available.


The drilling team has been continuing their work at Balfour 3.  At this stage, they are drilling the fifth out of ten boreholes that will be drilled at this location.

Balfour 3 drilling - 25.09.20


Borehole number seven out of ten has been drilled at Balfour 3. This means that drilling at this location is expected to finish by the end of this week (Monday the 5th of October at the latest). The team will then move on to the next location, which is Balfour 2.


Drilling has finished at Balfour Road 3 and the drilling rig and other equipment have moved a short distance away to Balfour Road 2. Drilling will commence here this week.


Four boreholes have been drilled at Balfour Road 2 meaning that drilling is progressing according to schedule.

Drilling at Balfour 2, borehole number 5 - 15.10.20


In the process of drilling the fifth out of nine boreholes at Balfour 2.


Drilling is complete at Balfour 2. The drilling team have now moved to Poulton Place


Three boreholes have been drilled at Poulton Place so far. In the area below ground, there are utility services. Above ground there are trees and resident's vehicles.  This can make maneuvering the drill rig into position a challenge. Therefore time and care is crucial.

Oxford University Survey


Researchers from Oxford University Environmental Change Institute, in collaboration with Oxford Brookes University, are conducting research into the tenant’s experiences of the installation and use of their new heating systems. Data will be collected over an 18-month period to monitor patterns of energy consumption, including internal temperatures. Tenants will be contacted at intervals over the survey period to obtain their views.

The researchers are interested in understanding how the tenant’s routines and habits may change, and how easy or difficult it is to achieve comfortable levels of heating with the new system. As part of these surveys, tenants will be asked if they are willing to allow the installation of technology to enable remote monitoring. By doing so, researchers can remotely monitor their energy usage necessary for the success of the data-gathering part of the project, while limiting the number of face-to-face contact visits

Kensa Contracting engineers also meet with the University researchers for the first time today. After a quick tour of the drilling area and some Q&As, they moved on to carry out the surveys. The timing of surveys - designed to be around 15 minutes - vary depending on the tenant and how many questions they may have, but the format of the surveys seemed to work very well. Any data collected is collected with the express permission of the tenant and is anonymised before use or further distribution.

From the 10 properties in Cuddesden Way, five of the tenants opted to take part in the surveys. Surveys will continue this afternoon at Balfour 3 and at a date to be arranged with the researchers again next week.

Tenant Surveys - 11.08.20


Raj from the University checked readings were being recorded on the monitoring equipment.


Continued research surveys were carried out at Balfour 2, which resulted in five more tenants agreeing to take part.


Although installations are coming to end, Kensa is still on hand to collaborate with the Oxford University project.



When hand-digging test trenches, experts on-site found that the location was very busy with services cables and pipework - not all of which are shown on the plans obtained by the energy providers. Adjustments have had to be made and Kensa Contracting remains flexible while staying within the parameters needed to ensure the borehole array collects sufficient energy.


As drilling has finished at Cuddesden Way the team from Leazes Energy will now come in to carry out the trenching and headering. Headering is the terminology used to describe installing horizontal pipes from the top of the vertical pipes in the boreholes to a central manifold. From the manifold this is piped again to a location adjacent to the property and capped off, ready for the internal installation team to arrive and commence their part of the work. The photograph below shows the area at Cuddesden Way where the work has been taking place. A new layer of topsoil has been added, graded, and reseeded.

Cuddesden Way - soil added - 25.09.20


Trenching and headering will commence at Balfour three next week (week commencing 19th of October) and take approximately a week. After completion, the installation teams will commence work within the properties.


At Balfour 2, Leazes Energy has installed horizontal pipes and manifolds which have been connected to a further pipe which ends at the flats themselves. This means the internal team can now take over.

First installation and commissioning


The internal installation teams arrived and started to remove the old technology which consisted of electric storage heaters. The team is now installing the new ground source heating systems. Two of the properties at Cuddesden Way are due to be completed by Friday the 9th of October.

The tenants will be able to control their heating systems using user-friendly Switchee Econa control units that will be connected to the new system.

Heating system control unit (being prepared for installation) 07.10.20

Heating system control unit being prepared for installation


Two tenants had their heating systems installed which marks a significant milestone in the project. Initial reports and feedback about the installations from the tenants has been very positive. Householders will benefit from being able to choose how much control they have over their heating by the use of the latest Swithcee Econa units. The smart system learns the heating habits of the occupiers and it will gradually learn the favoured times, temperatures, and tariff rates of the user.


Two more tenants are expected to have their new heating systems installed by the end of the day. During the installation process, Kensa Contracting worked closely with Stonewater to ensure that all tenants were aware of the dates and times that their heating systems would be installed.


The installation of six heating systems for tenants at Cuddeson Way has been completed. Initial feedback from tenants suggests that they are happy with the warmth, that their new heating systems are providing. They have also acknowledged the benefits of being able to control their heating and hot water to the level and times that they desire.


The internal installation team has almost finished installing the heating systems at Cuddesden way and will soon move to Balfour 3.


Out of the 60 properties, installations have finished in 57 of them. As the last of the installations are finished, Stonewater has arranged for the replacement of fences that were removed to gain access. All the drains have been cleared and jetted out to ensure there are no blockages and all grassed areas are now level and have been re-seeded. Therefore, in a month or two it will be very difficult to tell that workmen have been on-site with heavy machinery.



Councillor Tom Hayes from Oxford City Council joined Kensa Contracting's Managing Director, Dr. Matthew Trewhella, for a day of filming on the active site. The installation process was explained and discussions took place on how ESO can provide a blueprint for future projects. A tenant shared their experience of the installations and their thoughts on the Kensa Shoebox heat pump. Filming will continue tomorrow.

Filming with a tenant - 15.10.20


Kensa Contracting hosted a webinar with the Energy Superhub Oxford (ESO) consortium to give an expert insight into the groundbreaking project. The footage from filming was used to produce a virtual tour of the pilot heating phase in Blackbird Leys. The virtual tour is hosted by Dr. Matthew Trewhella, Managing Director of Kensa Contracting, and includes Oxford City Councillor Tom Hayes, and Adam Masters, Stonewater's Environmental Sustainability Manager.

Watch the virtual tour here:


After the government announced their 10-point plan to get the UK back on track to meet net-zero targets, the BBC reported from the Energy Superhub Oxford to demonstrate the low-carbon technologies that are already working towards a green revolution. The broadcast featured an interview with Kensa's Director of Sales, Dr. Stuart Gadsden. Simon Jack of the BBC also spoke to Paul Brennan, a satisfied tenant, who discussed his new ground source heat pump system.

Kensa - BBC - Nov 2020

Load Shifting


Tenants have noticed an improvement in their electricity bills from their new heating systems. Kensa is on hand to help tenants and assist with the ongoing load balancing exercise This should be beneficial for the tenants, in reducing their bills and also for other potential customers of a ground source heating.

Summer 2022

A University of Oxford study of the ESO ground source heat pump installations noted most tenants reported saving money, in many cases around 50%, thanks to the Ground Source Heat Pumps in comparison to running costs of their previous direct electric night storage heaters. Initial trials of load shifting the ground source heat pumps have been successful, demonstrating the concept works in practice, whilst maintaining the comfort levels of the residents.

The entire UKRI-backed ESO project is made possible through the Prospering From an Energy Revolution (PFER) programme, which encourages new approaches to delivering cleaner, cheaper and resilient energy.

Read more about the role of the entire two-year ESO project in the electrification and decarbonisation of heat, power and transport here.

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