ESO in conversation: Matt Trewhella, Kensa Contracting

15 September 2020

Energy Superhub Oxford aims to install low carbon heating at 300 properties in and around Oxford. We talked to Matt Trewhella, Managing Director of Kensa Contracting, about the benefits of ground source heat pumps, time travelling and what’s needed to accelerate heat decarbonisation.

Can you tell us a more about Kensa Contracting?

Kensa Contracting installs ground source heat pumps in large scale projects, typically a minimum of 20 properties but often up to 1,000 or more properties at a time. For that reason most of our work is in social housing or new build developments where one owner can make a decision to upgrade the heating or put ground source heat pumps in all of them at the same time.

How do ground source heat pumps work?

Ground source heat pumps take a large amount of low grade energy from the ground, typically between 2-12C, and put that heat into a heat exchanger connected to a refrigeration cycle. The refrigeration cycle upgrades the temperature of the heat extracted from the ground to anything between 35-65C and distributes that to the building for heating and hot water. Essentially it takes a large amount of low-grade energy and compresses it to increase the temperature and deliver a smaller amount of higher grade energy that’s perfect for households.

What are the benefits of using a ground source heat pump?

Heat pumps provide a low carbon, low cost heating system. Typically you get around three units of heat for every one unit of electricity. The other units are coming from the ground but it means you only pay for a third of the energy that you actually use in the property, so that is very efficient and cost-effective to run. And the really cool thing about the ground is that it doesn’t really change temperature. So when you extract heat in the middle of January you get the same temperature as in the middle of July.

What role is Kensa Contracting playing in Energy Superhub Oxford? 

We’re looking after the heat element of Energy Superhub Oxford and we are demonstrating how low carbon heat can be integrated within the wider energy system. We’re going to install up to 300 properties with ground source heat pumps, and the first group of properties are just about to have heat pumps fitted. We’re going to be drilling 35 boreholes at a site in Blackbird Leys in the southeast of Oxford and that’s going to provide heat for 60 properties owned by Stonewater Housing Association.

What makes your solution innovative?

We’re putting in a Switchee thermostat to monitor temperature and learn occupancy patterns and preferences for how warm residents like to be at various times of the day. This is going to be combined with Octopus Energy’s Agile tariff, which gives you a separate price of electricity for every half an hour of the day, so 48 prices in total. We’ll then create an optimised heating schedule to run the heat pump at a time when it will keep residents warm and save them the most on their electricity bill. We’ve modelled different scenarios and usage and it looks as if we can save people at least 25% on their bills compared to running a heat pump with a standard electricity tariff, so hopefully they will see a really good benefit.

What is the most exciting thing about Energy Superhub Oxford?

For some years we’ve known that to electrify heating and transport we’re going to have to find a way of using electricity in a smarter way. So we need smart controls of vehicle charging, smart controls of heat pumps and grid balancing batteries. But to actually be putting all three together at this stage is probably sooner than most people thought possible. It is like a having a time machine and living in the future but it’s actually happening now. And we’re getting to that exciting stage where the physical infrastructure is being built and we should start to see some of the data coming back and see how it all works together, and that is going to be incredible.

What impact do you hope the project will have in Oxford and further afield?

The project in Oxford is going to have immediate impact. The grid balancing battery will be working from day one to help stabilise the grid. The increase in electric vehicle charging is going to be hugely significant for Oxford. And obviously we’ll have 300 properties that have been decarbonised by at least 70-75% with ground source heat pumps.

That’s amazing and it’s a good scale but it is small when you look at the whole of Oxford and Oxfordshire and then again when you scale across the country. But what it will do is produce a blueprint for how that can be achieved at a wider scale and help enable all of those technologies to roll out across the country and give people confidence that the system can cope when you electrify those three elements together.

How can we accelerate the decarbonisation of heat?

We need to approach the decarbonisation of heat in a much more systematic way and develop a national plan. At the moment most of the financial help has been targeted at households, but it’s much more cost-effective to decarbonise lots of properties in one go. It needs to be rolled out in the same way that the gas system was rolled out originally, i.e, street by street, and town by town.

What changes do you hope to see in the energy sector over the next decade?

We would like to see the stopping or cessation of connecting new properties to the gas grid coming forward from 2025. New build properties really shouldn’t be connected to fossil fuels right now. Renewable heating systems are competing really well and if we model over a 40-year period some of them are very similar in cost or even slightly lower cost than fitting gas. Some subsidy will be needed in the short-term, but once these systems are in place, you’ve got a 100-year energy supply.

What gives you the most cause for optimism right now?

The most exciting thing is the scale we’re deploying at is growing year by year. Feedback has been really positive, which is leading to wider acceptance. Every person from a housing association that hears about it from visiting another project goes back and starts working on their project. So the number of projects we’re working on and the number of quotations and the number of feasibility studies we’re carrying out has escalated 10 or 20 times over the last two years, and that noise and the buzz bodes well for the next 5-10 years.

Do you see any positives coming out of this period of lockdown for the low carbon transition? We’ve seen some immediate positives – people travelling less, air pollution reduced and I think everyone got to look up and see fresh air and clean skies. The carbon intensity per person also went down dramatically. Even things like the electricity grid, it was amazing to see a peek into the future, when the grid is completely dominated by renewable and low carbo


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