A Scottish water company is utilising the flow in its supply pipes to offer dual benefits of an improved service for customers and reduced operating costs for itself.
Scottish Water has announced an ambitious £20M (US$31.5M) hydro power generating scheme that will use the considerable flow in large water supply pipes to generate electricity and protect water treatment plants from power failures. The work will reduce the power costs for water treatment by 10%, playing a key part of keeping Scottish Water’s operating expenditure down.
Water and waste water treatment is energy intensive and complex, with the majority of Scottish Water’s energy used in pumping water. Even with the generally high raw water quality in Scotland, a lot of energy is required to treat water to meet the standards set out by the Drinking Water Quality Regulator and the Scottish Environment Protection Agency (SEPA).
Currently more than 30 sites have been identified that could – using techniques most commonly seen in hydroelectric schemes – power the water treatment process in areas such as rural Lanarkshire, the Borders, Stirlingshire ,Angus and Fife. This will then be rationalised to around 20 sites.
The schemes will mostly make use of existing Scottish Water buildings and also see the construction of some small buildings and electricity infrastructure to transfer the power from the point of generation back to the water treatment works where it is required. Some of the electricity infrastructure will be ‘off the grid’ – so any major power loss by the power companies would not affect the supply of water to customers.
John Kirkpatrick, project manager of Scottish Water’s capital investment and delivery division, said: “This is a key part of our climate change strategy and will substantially reduce our carbon footprint. We’re very excited about technology that offers the dual benefits of improved service for our customers and reduced operating costs.
“This is nothing new – our asset base is already generating 5% of our power requirements across Scotland and the investment will double that output. We’ve identified a number of potential sites and these will be whittled down to the best 20 or so small hydro schemes.”
Kirkpatrick said that the company has ministerial and regulatory objectives which are aligned with a keen interest internally to invest with a view to reducing power costs.
“We are working closely with the national park authorities, community councils, power companies and planning officials to make sure these small hydro turbines have minimal effect on the landscape,” he stated. “Some of them will be situated in areas that are very remote so constructing them will require very diligent planning work on our part.”
Acknowledging that £20M is a large investment, Kirkpatrick is confident that this will soon pay itself back by allowing the company to generate its own power. “The power derived from our installations can be used by Scottish Water to offset required energy at our treatment facilities across Scotland,” he added, “or to directly feed into the National Grid system via our power purchase agreement counterparty (RWE nPower), and in some instances both.“
During the project feasibility phase, a number of various scheme types/location have been identified, for example:- Run of River; Dam compensation flows/spills; Inlet to Water Treatment Works; and Inlet to break pressure tanks and network pipe lines.
Scottish Water has set up new supplier frameworks for the hydroelectric kit. The required turbines will be sourced where possible from these framework companies (Gilkes, Ross-shire Engineering and SSE). The proposed turbines for installation range from TJ Turgos to Francis and Peltons; however detailed design will clearly identify best fit for each location to match head and available flow.
Additional civil structures will be required for the chosen sites and locations. The main civil work will be undertaken at the run of river locations. These are essentially green field sites so in order to install the hydro power solutions new intakes, penstocks, pipelines, access roads etc will be required. Although civil works will also be required at other locations, these are within existing Scottish Water operational assets which have existing pipelines and structures already in place.
Examples of how the power is produced:
• Power generation using compensation flows from (raw water) dams/reservoirs:
This is the traditional form of power recovery at reservoirs and to some extent at treatment plants. For these schemes, there is generally a constant flow of water available. Installing a hydro turbine here allows Scottish Water to tap into this existing resource and generate power which can then can be utilised to offset required energy for the water treatment works (WTW), be exported to the National Grid via a power purchase agreement counterparty (RWE nPower), or both.
• Inlet to water treatment works:
Water entering a plant for treatment will pass through a suitable turbine. This also provides power for use (off-set) on-site or again export to the grid via a power purchase agreement counterparty. Using a turgo impulse turbine at these locations allows flow control to be independent of power generation.
Kirkpatrick continued: “We have carried out feasibility on 48 sites, this was reduced to 34 sites on completion of our feasibility phase. Our identified sites range across all of Scotland, from Loch Katrine in the Trossachs, to Glendevon in Fife and to areas in the south, east and west of Scotland. Under this programme we have more than 20 sites that will progress forward to the construction phase. Within these sites, we have identified (during feasibility) that the estimated annual energy output ranges between 318MWh – 4632MWh.”
An example of the sites being utilised fall into the following categories:-
• Raw water:- run ofrRiver Schemes (green field site); dam flows to water treatment works; dam compensation flows and spills to rivers.
• Potable water locations:- Inlet to break pressure tanks or by running water through pressure reducing valves.
Scottish Water completed the project feasibility phase at the end of August 2011 and have now moved into the development phase with all 34 identified sites.
Kirkpatrick explained that that company has undertaken a partnering approach with its framework design and build contractors. The 34 sites have been split into three groupings then allocated to each of three partners:- black-veatch; Amalgamated Construction and Ross-shire Engineering.
The development phase is presently programmed for completion across all three groupings by August 2012 and discussions are currently taking place with local planning departments, SEPA, the National Parks Authority and Distribution Network Operators:- SSE and Scottish Power).
‘Our design and build partners are developing each of the identified schemes,’ Kirkpatrick said. ‘On completion of the development phase, we will identify and take forward 20 or more sites into our implementation phase (construction) to allow achievement of our regulatory outputs for this programme of works. The regulatory outputs were set by the Water Industry Commission for Scotland (WICS).’
These regulatory ouputs are as follows:
• Increase generation of renewable energy, by 25GWh per annum by 31 March 2015.
• Deliver Operational Expenditure savings of £2M (net saving) by 2014-15, as a direct result of investment in renewable energy schemes. In addition to this, an interim internal target has been set to deliver £2M OpEx savings in 2013-14
In addition to this project, Scottish Water Horizons, the commercial arm of Scottish Water, has recently installed a micro-turbine at the redundant Touch water treatment works in Stirling. This is creating power which is then sold back to the National Grid. Horizons is driving forward the green agenda as part of Scottish Water’s ambition to be a low-carbon business.
Scottish Water procurement has also set up new frameworks to cover the requirements of its hydro programme of works:-
• Design and build contractors (now in place).
• Kit suppliers (turbines, now in place).
• Operation and maintenance:- presently on going.
This work is all part of Scottish Water’s wider renewable energy portfolio which also includes wind and biogas production from food waste. The overall portfoilio of green energy projects places Scottish Water at the forefront of innovation in the UK water industry and is in line with the aspirations of the Scottish government’s Building a Hydro Nation Water Bill, which aims to harness Scotland’s renewable energy potential from water.
Scottish Water is investing £2.5B in the 2010-15 period to improve water and waste water treatment across Scotland.
John Kirkpatrick, Project Manager Capital Investment Delivery, Scottish Water. EMail: firstname.lastname@example.org