Scottish Water has reported significant growth in the number of its sites across the country which have become self-sufficient through the use of hydro, wind, solar and waste conversion.
Over the past six years, the utility has increased renewable energy self-generation capacity to 63 Gigawatt Hour (GWh) per annum – three times the capacity available in 2013.
With more than 70 of the country’s water and wastewater treatment works now either self-sufficient or partly sufficient in their power requirements, combined with a range of energy efficiencies being achieved across the organisation, Scottish Water says it is achieving regulatory renewables and energy targets ahead of schedule.
There are now 38 hydro turbines, 20 sites with small-scale wind turbines installed, 42 solar schemes, four Combine Heat and Power plants and three biomass boilers.
Figures highlighted by the firm during Climate Week show that the national water and waste water services provider now self generates 35 Gigawatt hour (GWh) per annum of energy – enough to power around 11,000 homes a year.
Scottish Water is one of the biggest users of electricity in the country and consumes about 440 GWh per year of grid electricity at its sites. The organisation is committed to becoming net zero by 2040, five years ahead of the national milestone.
Fraser Purves, Energy Manager at Scottish Water, said: “As a significant user of electricity a key objective is to reduce our reliance on grid power to make us greener and reduce operating costs. We are fortunate our infrastructure provides various opportunities for us to act sustainably to deliver our service and maximise financial value for our customers.
“In 2018/19 our sites self-generated more than ever before. This was down to ongoing investment at various locations throughout the country.”
Scottish Water Horizons, the utility’s commercial business that works to encourage growth and invest in renewable technologies, has made a significant contribution to Scottish Water’s renewable programme.
Donald MacBrayne, Business Development and Delivery Manager at Scottish Water Horizons, said: “Finding and developing innovative ways to generate power from our assets plays a key role in helping us achieve renewable targets and tackle growing energy demands.
“The diversity of our renewable and low carbon energy portfolio is fundamental – whether that’s increasing biogas production at Scottish Water sites, generating green energy from food waste, recovering heat from waste water networks or exploring the potential to produce hydrogen from recycled final effluent.
“Already we have a strong pipeline of further sites of various sizes and stages of development to increase the sustainability of Scottish Water’s operations and help drive forward its net zero goals.”
Scottish Water says it has also cut its overall carbon footprint with an increase in energy efficiency at many of its sites – and has achievement its renewables and energy efficiency target two years ahead of target.
This was done by hosting third-party private generation, including large-scale windfarms, along with working with local communities and land-owners, to identify suitable Scottish Water sites which can purchase power via private wires from local community-owned renewable assets
In 2015 the utility announced plans to save 17.5GWh by 2021 – the most ambitious energy saving drive it had ever undertaken. As well as reaching this target ahead of time it has brought about the savings under budget.
Mr Purves added: “Our advances in both self-generation and energy efficiency demonstrate how Scottish Water is making a significant contribution to Scotland’s overall national economic, carbon and renewable energy targets. Scottish Water will continue to use these techniques as well as other new ways to save energy and reduce its carbon footprint and will be working towards new energy saving targets.”
Scottish Water’s operational carbon footprint for 2018/19 was 13% lower than the previous year. Overall, its footprint has fallen by 41% since 2006/7.
Some examples of how Scottish Water says it was able to increase self-sufficiency at its sites include the following:
• Hydro power at Firrhill water service reservoir in Edinburgh
This hydroelectricity site in Oxgangs is powered by treated drinking water and generates electricity as a byproduct. Energy is harnessed from the flow and pressure of water arriving at the site powered through a hydroturbine. A 160kW Turbo Impulse turbine machine sits next to a generator and harnesses the pressure and converts it to energy It holds 18,200,000 litres of fresh drinking water and works so efficiently it runs itself and feeds 60 000 kWh of electricity a month to the grid.
• Wind power on Stronsay
The utility’s most remote renewable site is on the Orkney island of Stronsay WTW which supplies water to just 350 people. The site generates 30 per cent of its own power (enough to power 14 homes) from three 5 kw wind turbines installed in one of the most northerly parts of the country. Additionally with the grid restrictions in place in Orkney – where there is no more capacity on the grid to export power – Scottish Water had to install off-grid heaters to utilise the generation in more creative ways – it does this by heating the works instead of creating electricity with some of the generated power.
• Combined Heat and Power (CHP) at Galashiels Waste Water Treatment site
The site generates electricity from sewage sludge, the semi-solid by-product of waste water treatment using a CHP. It generates more than 18,000 kWh/week of renewable energy – enough to power 204 homes for a year.
• Solar photovoltaics at Spey
Nearly 5,000 solar photovoltaic (PV) panels have been installed at two borehole sites which take water from the River Spey. Power generated will be used to help pump water from the ground to the nearby water treatment works at Badentinan. The largest solar scheme of its kind built by Scottish Water Horizons, the solar scheme is expected to provide a fifth of the site’s annual electric needs – saving the equivalent of 437 tonnes of carbon dioxide every year.
