North-West Bicester is the UK's first eco-town and we have been working on the project since 2014, delivering the energy centre and district heating network and continuing to connect homes in future phases as the project continues to develop.
“By working with the client, liaising with our supply chain and having good communications with the builders of the energy centre we were able to complete the fit out before the building construction works had been completed.”
North West Bicester is the UK’s first eco-town and the first phase, known as Elmsbrook received planning permission in 2012, with construction beginning in 2014. The flagship project is bringing investment, jobs and up to 6,000 homes to the area, with A2Dominion committed to creating a community which is good for the environment, the economy and “a great place to live.”
The ambition is for this development to become the first true zero carbon community in the UK and we were delighted to win the contract to help make the vision a reality. Our responsibilities included designing and delivering the entire energy solution including CHP energy centre, metering solutions and hydraulic interface units as well as the district heating network which would distribute heat and hot water throughout the scheme.
This project presented a demanding schedule and Phase 1 required over 2,400m of district heating flow and return pipework to be fully installed in 1200m of trenches over a 6 month period. Vital Energi worked closely with the two developers on the busy, multi-contractor site to ensure a joined-up approach to planning and delivery. Due to our in-house expertise, we were able to meet this challenging timescale, performing the fusion welding and the muffing to the strict deadline.
In addition to installing the main district heating “spine”, we were responsible for delivering the branches and house entries and designed the entire network to be “future proofed” so that it could be easily expanded to connect further phases as they came on line. The main spine is series 2 steel pre-insulated district heating pipework, designed specifically to reduce heat loss, with the branches and house entries made up of a combination of Aluflex and Steelflex pipework.
Phase 2 of the project saw us deliver the extension of the mains network and house entries to connect 72 dwellings as well as the internal riser and lateral pipework. Our engineers also installed and commissioned the hydraulic interface units and heat meters.
This phase was delivered by house builder Hill Contractors and it was essential we built an effective relationship with them as they were contracted to perform the offloading of district heating pipework and all civil works connected with the district heating network, making communications and effective planning essential.
One of the key factors of Elmsbrook was the site’s ability to generate electricity from both the energy centre and individual property PV cells. The network operator had set strict limits on total export from both sources. Vital Energi in collaboration with Silver Energy management Solutions ltd worked through a methodical process of commissioning and verification to ensure that the energy centre would operate strictly in accordance with the design specification.
Producing savings through value engineering-led design
We worked closely with the client’s professional team to enhance the original design of the energy centre. We were aiming to create an energy centre with the smallest footprint possible delivering capex savings for our client and allowing us to reconfigure plant and equipment in a way which still performs optimally, but reduces the necessary floor space. In the instance of Bicester our designers were able to configure the plant into a more compact layout which allowed the Energy Centre to be as small as possible to reduce costs and to be less visually imposing to surrounding homes.
While the energy centre design brought our clients some significant benefits, it called for extremely accurate manoeuvring and placement of plant and equipment. This was made easier as our project team used their vast experience to inform the layout design development using practical lessons learned on previous projects. Larger items, like the 27,000 litre thermal stores had extremely low tolerances for inaccuracy as they needed to match with the prefabricated pipework and the combination of careful planning and good layout design saw this area of the project proceed without any issues.
Demonstrating Flexibility to Protect Client Programme
The building envelope of the energy centre was being delivered by a third party and an unusual aspect to the project saw us perform the fit out before the envelope was cladded or watertight. This allowed our client maximum flexibility with their programme, but meant that we would have to deliver the project in a slightly less traditional method. An example of this can be seen with the installed containerised CHP engine. Usually this would arrive in pieces and be assembled on-site, but as the building envelope wasn’t weather proof, to ensure plant protection, we worked with our supply chain to have the entire CHP containerised system arrive assembled.
By working with the client, liaising with our supply chain and having good communications with the builders of the energy centre we were able to complete the fit out before the building construction works had been completed.
The energy centre utilises an 889kWe Combined Heat and Power engine, which not only generates electricity, but also hot water which is utilised within the network to provide heating and hot water for all of the dwellings. This is supplemented by two 776kW boilers and two 1750kW boiler, with the space for a further boiler to be added when demand increases. The design also includes three 27,000 litre thermal stores which have a total capacity of 81,000 litres. The thermal stores have been sized using modelling software, to provide thermal storage during periods of low demand to allow the CHP to run at the maximum rated output. The stored heat is then discharged as the demand increases, this solution allows the CHP to provide approximately 60% of the annual heating demand.
One aspect of district heating schemes which can have huge implication on carbon savings and running costs is the design of the main system pumps which distribute water around the network. Because these systems operate 24 hours a day, 365 days a year for decades, any miscalculations can prove extremely costly. We designed a solution with multiple pumps rather than the usual run and standby pumps, which gave greater control and efficiency through the phased installation and during lower demand periods, such as evenings or through the summer.
Utilising in-house expertise to reduce programme time & costs
Our Prefabrication Department based at our Blackburn Headquarters were able to deliver the prefabricated pipework and skids. This brought several advantages to the project. Quality was improved as the works were being completed in a controlled environment, health and safety was improved as there were no hot works required on site and the installation time was significantly reduced. The Vital team performed over 1,400 welds over an 8 week period at their Blackburn-based prefabrication workshop. Not only did this result in a shorter programme, but reduced the cost by 23%.