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Project Focus: Wessex Water goes solar at Sutton Bingham WTW

A rooftop installation of 192 solar panels in a 50kW photovoltaic system is helping Wessex Water meet renewable energy goals

Julia Clarke surveys the solar panels at Sutton Bingham WTW, which is near Yeovil Julia Clarke surveys the solar panels at Sutton Bingham WTW, which is near Yeovil


John Leonard, Energy Manager, Wessex Water:
“Sutton Bingham is an important site for Wessex Water and has seen significant additional quality requirements imposed over AMP5. The successful completion of the recent solar PV scheme has not only reduced the grid electricity requirement, but reduced Sutton Bingham’s carbon footprint.”

James Lovell, Supply Controller, Wessex Water:
“The solar PV project represents a successful innovation collaborated by the energy team and the Sutton Bingham production team. We look forward to realising the carbon savings thatthe solar PV will enable and will look to understand potential locations for further installations.”

Nick Spicer, Operations Director, Your Power UK:
“We’re delighted with the efficiency of the install. We conducted a number of site scoping studies before we began, making sure we thoroughly understood site dynamics to ensure Wessex’s regular operations were not adversely affected.”

by Julia Clarke, Energy Generation Analyst, Wessex Water

The energy team at Wessex Water recently installed the company’s first rooftop solar PV electricity generating system, at Sutton Bingham Water Treatment Works.

The 50 kW scheme was approved by the board, tendered, installed, commissioned and had the Feed in Tariff (FIT) application approved within two months, all prior to the FIT deadline of 31 December 2014.

Wessex Water aims to be a carbon neutral company, and has set a target of generating 30% of its own energy from renewable sources by 2020. Consistently high energy prices and increasing taxes are a few of the reasons why the company is turning to renewable energy to power operational sites.

Wessex Water and subsidiary company GENeco already generate electricity from hydro turbines and combined heat and power (CHP) fuelled with sewage gas and food waste gas. In 2014, 38.5 GWh of renewable electricity was generated and used on Wessex Water’s operational sites.

Why Photovoltaic?

Previous to the Sutton Bingham PV scheme, the company had concentrated on the development of the CHP portfolio as a means of increasing renewable energy generation. Smaller scale technologies and lower capital cost sources of energy generation were investigated. Solar photovoltaic appeared to have the greatest benefits due to the low environmental and local impact, quick installation and most beneficial use of developed land. Rooftop options were preferred over ground mounted, due to the limited available space on operational sites and fewer planning restrictions.

The business case for solar PV was helped by the Feed in Tariff (FIT) which largely depends on the size of the array and time by which it was installed. Solar panels are expected to last at least 25 years, and come with a warranty which guarantees the output to be >90% for the first 12 years and >80% over the next 13 years, and therefore is considered to be a good investment.

The Wessex Water energy team, a dedicated resource for energy efficiency, data and billing accuracy and small scale renewables, were responsible for the project. The team selected Sutton Bingham water treatment works out of the 2,545 sites consuming electricity for the following reasons:

• Sutton Bingham has a consistently high baseload of >100 kW during hours of daylight and therefore is able to displace the PV generated to take full advantage of avoiding rising electricity costs
• The local electricity grid had the capacity to increase the export agreement to account for maximum generation with no site load in case of power downs
• The site’s Energy Performance Certificate (EPC) was level D or above which qualified any eligible generation to the highest FIT rate
• The roof on Treatment Block 2 (TB2) is south facing with no obstructions, enabling maximum electricity generation
• The roof was considered strong and large enough to take a sizable PV array
• Any reflection from the roof would not impact on local surroundings or residents due to the height

Tender and Installation

The energy team tendered for the maximum sized rooftop solar installation that was possible under permitted development rights and invited companies to determine the size of the array. Planning permission on a scheme of this size would have increased the cost of the project and as a result increase the payback period.

There was a requirement for the payback period to be less than five years, and the preferred size of installation was as close to 50 kW as possible to fall within the 10-50 kW retro-fit bracket which had a FIT rate of 12.13 p/kWh. This FIT bracket was 1.79 p/kWh higher than for larger installations of up to 100 kW. If the installation had been 51 kW, the difference in FIT payments over the course of 20 years would have amounted to over £20,000.

The site surveys and tender brought a mixture of proposals, from 34.7 kW to 49.9 kW, and a significant variance in price. Your Power UK, part of the Your Group company based in Bristol, won the tender and proposed an installation of 192 panels of 260 W each totalling 49.9 kW peak power. The predicted generation from this size of array is over 46,301 kWh per annum. Forest Electrical was appointed as the contractor for the electrical works having won the electrical tender. Stark Software International Limited (with WPD Metering) were contracted to install and provide data from the generator sub meter as they were already an approved contractor.

The contracts took two weeks to set up, which enabled Your Power UK to schedule the scaffolding erection for the 3rd December. On 8th December Your Power UK began installing the racks and panels, and by the 15th December the system was completed and commissioned.

The FIT application was completed and submitted the day after site commissioning and the electricity supplier approved the application within three days. This process was helped by good communication prior to the formal FIT submission.


There were a few challenges as part of this project and meticulous project management was required to enable a smooth installation. One of the challenges was the number of contractors and staff that required access to the site. Sutton Bingham has little available space, with a single access track through the site and minimal parking. In order for the scaffolding and panel deliveries to be able to reach the far side of the site, it was necessary to liaise with site staff and contractors to avoid operational disruption.

Sutton Bingham water treatment works PV scheme proved to be a good example of how solar PV can benefit the company. There are likely to be more of these sized projects in the future to help reduce energy costs and carbon emissions.

Hear more about Wessex Water’s energy and carbon strategy at WWT's Energy and Carbon Management conference, 17th September 2015 in Birmingham: www.wwt-energy.net

Topic: Energy/Water Nexus
Tags: solar , photovoltaic , feed in tariff , energy


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