Let there be light - 1000 year old Gloucester Cathedral becomes the oldest building of its type in the world to install solar PV
Gloucester Cathedral - Installation date: November 2016
In September 2016, Mypower was awarded the prestigious contract to install 150 commercial solar panels on the roof of the nave at Gloucester Cathedral. Principle Architect for the cathedral, Antony Feltham-King, was highly impressed with Mypower's proposal: "Your submission was the most technically developed, and provided an excellent range of options for further discussion with us."
The 38kW solar array will reduce the Cathedral's energy costs by 25%, helping it deliver the Church of England's ambitious 'Shrinking the Footprint' campaign, which aims for an 80% reduction in its carbon emissions by 2050. The 150 panel system is a relatively small installation for Mypower, yet Gloucester Cathedral has been our biggest challenge by far. Not because of the install itself but because of the intricate detail and sensitivity around such an important and historic building.
The 1000 year old Grade 1 listed building is famous for hosting the Coronation of King Henry III and for being the final resting place of King Edward II, as well as providing a location for three of the Harry Potter films.
The 30m high roof of the Nave provided the ideal position for the solar panels as the parapet wall and crenellations hide the panels from ground view. However, the height of these obstacles meant that, during the winter months, there would be some shading issues.
Mypower created animated graphics showing shading changes throughout the day and at different times of the year to demonstrate the anticipated yields for different types of panels and inverters. This allowed the Cathedral to choose the right balance of capital cost and electricity yield whilst ensuring the panel design closely matched the roof, with aesthetics overriding costs. The REC TP model was top of the list with the shading, however despite having received all the panels from the supplier, Ben suggested a last minute switch to the REC BLK2 model to improve the look. Thankfully our supplier, Wind and Sun, was willing to accommodate this.
Left panel: REC TP = Highest yielding
Right panel: REC BLK2 = Best match colour
Photo right: Non-penetrating fixing rail system and ballast
The choice of inverter was an easy decision to make. SolarEdge optimisers and inverters are perfect for this type of shading issue, while their fire safety features and monitoring system a major benefit.
Using a specially designed nonpenetrating fixing rail system from Sunfixings, the panels sit on top of the lead roof on the Nave, weighed down by 4.5t of ballast. This meant no holes were made nor fittings attached to the lead roof of the ancient cathedral.
"The installation of solar panels on such a beautiful and beloved building as Gloucester Cathedral has raised interest locally and nationally so it's been fantastic that Mypower have been taking such great care with the work. Since starting on site, the team have identified a way of hiding the ballast beneath the panels which our structural engineer is delighted with. And they've managed to accommodate both the physical restrictions of the site and the fact that we're a place of worship as well as a busy destination for visitors."
Anne Cranston, Gloucester Cathedral's Project Manager
What makes Mypower different?
Ballast, using concrete lintels provide weight to the non-penetrating fixings and prevent uplift of the panels. In the original structural and engineering designs, prior to Mypower's tender, these ballast blocks were to sit fully exposed below the solar panels. Unhappy with this arrangement, Ben Harrison set out to find an alternative solution. Ben spent hours of unpaid time finding a solution which would provide the security and structure needed but not compromise the beauty of this ancient historic building (even though the structure would not be visible form the ground). This was above and beyond what was required of Mypower but illustrates their ethos... honesty, tenacity and always looking for perfection.
The 150 solar PV panels will generate 29,000 kWh of energy a year, enough to power seven semi-detached houses or make 250,000 cups of tea per year! Energy costs will be reduced by 25 percent, saving £190,000 over the next twenty five years. All this with no Feed-in Tariff subsidy due to the project being grant funded. The solar installation will provide 16 tonnes of CO2 savings per year, the equivalent of planting 3.5 acres of woodland per annum.
In November 2016, the Very Reverend Stephen Lake, Dean of Gloucester, switched on Gloucester Cathedral's new solar panels for the first time. To mark the occasion, the Dean blessed the panels from the 100 foot high nave roof and the Cathedral's famous tower was illuminated green. Speaking on BBC Radio, the Dean of Gloucester said: "It's actually an incredible installation, it's so well done by Mypower... it's a work of art when you can see it and, of course, when people do in time go up one of the tower tours, that's the only place from which they'll be able to see the solar panels."
Ben Harrison of Mypower said: "From the first moment I stepped onto the roof of this incredible building, I knew it was going to be a challenging but thrilling project to be involved in. Everyone has worked together in full cohesion to deliver a common goal - to protect this historic building and create a green energy source for the long-term sustainable future of the Cathedral. We are all incredibly proud of what has been achieved - it has been the opportunity of a lifetime."
The Dean of Gloucester & Ben Harrison of Mypower
Gloucester Cathedral Case Studies
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