Renewable Technologies A combination of Solar PV for the electricity and a biomass boiler for the heat was selected as the most appropriate, renewable combination to meet the buildings need.
Biomass was selected as there was an existing serviceable wet radiator system already within the church which suited a high temperature system. A ground source heat pump or the connection to an existing biomass plant at a farm estate complex on the other side of the road had to be discounted due to the archaeological issues of any excavation within the churchyard. Due to the low weekly use of the boiler (7 hours per week) it was feasible to propose a manual loaded system for the wood pellets, which would be supplied in 10kg bags. This removed the need for a large hopper in which to store the pellets. The manual load hoppers store 250 kgs and, at the use of 60kgs per week, this requires filling every 4 weeks.
The removal of the oil tank from the churchyard was seen as an additional benefit by providing more space and removing both pollution and a security risk from theft of oil.
As with most churches, this building has an east/ west orientation of the aisle which, as the nave has a pitched roof, one side of the pitch faces due south. The roof is at 30 degrees and entirely hidden by a parapet around all sides. The installation of PV would therefore be ‘invisible’, which was then acceptable for this listed building. The size of the array was selected as a balance between more than meeting the estimated annual electrical demand of the building and filling the optimal roof space available. A 3.24kWp system of 24 panels covering 24.05m2 was choosen.
Challenges and Innovation The key issue with the solar panels was one of fixing them to the existing roof. No penetrations were permissible through the copper clad roof and therefore a self-weighted system on a pitched roof had to be adopted. While self-weighted systems for flat roofs are available, a more innovative approach based on a ‘roof ladder’ principle had to be adopted. This involved extensive investigation into the structural capacity of the existing roof.
Additionally careful consideration had to be given to the cable route from the panels to the meter. The cables now use the route of the rainwater goods.
With the biomass installation, the significant challenge was getting the sizable and heavy boiler down the narrow stairs into the existing plant room. A Froling P4 pellet boiler was selected, as this could be largely dismantled to allow for improved access.
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Costs and Figures The biomass installation is a 38kW Froling P4 biomass pellet boiler which replaces an old oil boiler. Previous oil usage was 4,000l/year at a cost of around £1,500; carbon emissions were 12,116kgCO²e/year. The use of biomass pellets is estimated to be around 2 tonnes at a cost of £400/year. Carbon emissions from these are estimated to be 0.052kgCO²e/year. The biomass installation will therefore save £1,100 per year in fuel costs and over 12 tonnes in carbon emissions. The cost of the installation was £23,110.
The PV installation is a 3.24kWp array of 24 Kyocera modules, which will have an estimated annual generation of 2,592kW. The total cost (including specialist structure design) was £18,057. The system will gain Feed in (Generation) Tariff of £1,070 per year and an estimated export of 80% providing a further £62/year, a further £60 will be saved by avoided purchase.
The unimproved electrical consumption was 2,930kWh/ year, costing £338 and emitting 1,594 kgCO²e/year. Following efficiency measures this has been reduced to 1,838 kWh/year. The efficiency measures cost £510 to complete providing an annual saving of £125/year and 595kgCO²e/year.
The church will have an overall net export of electricity of 754kW/year providing a positive carbon abatement of 410kgCO²e/year and more than meeting its zero carbon status.
Image far left: Outside of the church. Image middle: Solar panelling on the roof. Image below: The new Solar powered/ biomass boiler.
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