Chew Valley School is situated 8 miles south of Bristol between the villages of Chew Magna and Chew Stoke and provides education for around 1,200 pupils. It stands on a 30-acre site in open countryside overlooking Chew Valley Lake. The school buildings are surrounded by very pleasant grounds and landscaped gardens. There are extensive playing fields and tennis courts along with a sports hall.
PV Array Details
In 2011 the school decided to install a PV array to be fitted to the SE faces of the sports hall. (These can be seen on the image below .) The installation consists of 217 individual panels, with each rated at 230 watts. This gives a peak capacity of 49.91kWp. The array uses three inverters to convert DC output into AC power, which is then fed into the school’s LV distribution network to reduce the amount of energy that is imported. The initial capital cost of the array was just under £113,000. At the time there was an anxiety to have the system installed before the government reduced the level of support offered through the Feed In Tariff scheme. (“FIT Scheme”) It was installed by Bristol-based provider, Your Power Ltd.
How has it performed?
The project has performed very well. At the time it was commissioned and accredited by Ofgem, the project secured a subsidy rate of 32.9p/kWh through the Feed In Tariff scheme. This is paid to the school each quarter based on the generation output from the panels. In addition, the energy that the array produces means that the school needs less power from the grid, saving this import cost. The FIT payment has risen with inflation each year since installation and is currently worth around 45.76 p/kWh (as of 2022).
The FIT is guaranteed for 25 years, and so the school will continue to enjoy the subsidy right through until 2036! Mark Farley, the school’s Facilities Manager confirms that the system has performed very well and has required no replacement parts to date although inverter replacement is anticipated around year 15. Average annual production is 47,769kWh which equates to 957kWh/kWp. The school has enough demand to ensure that it uses every kWh of energy produced on the school site. Typical consumption and production profiles are shown below.
All of this means that the investment has been very successful, with a payback of five years, and the annual cash benefit to the school in 2018 was worth around £25,500. The panels are expected to have a useful life which stretches beyond the 25 years of the current FIT support, however taking an investment horizon of 25 years, the expected lifetime contribution from the project is significant.
With the uncertainty surrounding the future price of electricity, the project has provided the school with a very useful hedge against price increases, as well as playing a part in the curriculum as a real life example of climate
Carbon Emissions Reductions
The impact of the investment has been to reduce the carbon emissions at the school site by around 20te CO2e per annum using the original 2011 grid conversion factors. As the grid decarbonizes and more renewables become part of the energy mix, this saving will reduce. Current Investment Prospects The economics of solar PV in the UK have changed significantly over the past ten years. The typical installation cost for systems of 50kWp has dropped from £2,270/kWp at the time of the CVS project and are now approximately £700/kWp. This means that the same array would probably cost the school around £35,000 today. At the same time the rates of subsidy payable under the FIT scheme have been cut to reflect this falling capital cost and the generation tariff for PV was removed altogether in April 2019.
The main benefit of installing solar PV is now the ability o offset the rapidly rising cost of imported energy, with typical daytime import power currently costing schools around 30p/kWh (Feb 2022 figure). A solar PV array is currently expected to deliver payback within 6 years, and still provides a meaningful level of cost savings against electricity bills.
The capital cost for these assets can be met through Salix Energy Efficiency funding, which provides interest free loans to publicly funded entities including schools and colleges.