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ENERGY INTERNATIONAL

Oct/Nov 2011 www.esb.ie/em

Water recycling not a grey area for Moneypoint

Pictured (l-r): Moneypoint Maintenance Supervisors Frank Nolan, Fergus Daly and John Lamb, who were responsible for the installation of the first station water recycling project. Inset: Moneypoint Maintenance Engineer Cormac O’Connor, who managed the second station water recycling project.

Generation Operations

INDUSTRIAL GRADE water or ‘grey water’ is required in significant amounts at Moneypoint where the wet ash handling plant for the boilers and the spray water used for flue gas abatement consume approximately 650,000 cubic meters of water a year. Until now, the station had only one water source available, the town water, or drinking-quality water, supplied by Clare County Council, which results in a significant cost to ESB and is an unsustainable use of a natural resource.

Town water is, in most cases, of a quality in excess of what is required for industrial purposes. Only 50% of the water consumed by the station needs to be of drinking-water quality, with lower quality water sufficing for the remainder of the station’s needs. Treating and supplying significant quantities of water for the station is an inefficient use of resources when water could be sourced by other means.

At the commencement of its sustainability programme, Moneypoint was quick to identify the need to find an alternative water supply. In 2009/2010, the station implemented its first water recycling initiative to capture boiler and site drainage and to redirect this to the boiler wet ash handling plant.

This project was immensely successful, achieving a total return on investment in the first half of this year, and it is capable of supplying greater quantities than was originally envisaged. Further investment in water recycling and harvesting could supply additional needs within the station.

Such was the success of this first project that Moneypoint set itself the ambitious target of recycling 320,000 tonnes of water per year from boiler drains, site and process water drainage. The primary use for this water would be the new flue gas desulphurisation units, each of which has a water demand of up to 45m³/h. Because the water used in the flue gas abatement is consumed within the desulpherisation chemical reaction and forms part of the exiting gas, there is no discharge of liquid water, in line with the station’s ISO 14001 to work towards having no water discharges at all from the site.

Following the success of the first water recycling initiative, a second, more ambitious project was completed with the aim of capturing, treating and supplying 130,000m³ of industrial grade water to the station. This project has resulted in the total capture of site drainage over 70 acres of the site. The project entailed installing a pumping and filtration station at the final site discharge point, a settlement lagoon and final filtration station and a pumping unit to deliver the water to a final industrial water storage tank. The latter systems were already in place but had not been designed to handle such a water supply. This project has delivered significant savings thus far and, after the final modifications are carried out, it is expected to surpass the 130,000m³/year forecast.

The final recycling project planned for 2011 is currently underway, again focusing on capturing process water and site drainage for the station site. The completion date for this work is the end of October this year with an expected recycle rate of 110,000m³/year. “Not only will this project reduce the station’s requirement for water, it will also help relieve pressure on the local council in relation to meeting the water needs of the county both in terms of water supply and chemical requirements for the treatment process,” said Glenn Pope, Moneypoint’s Station Manager.

Estimates put the savings that can be realised by these current projects at €5m by 2025 and future recycling projects are in the planning phase. Generation Operations Manager Nicholas Tarrant said, “I would like to congratulate everyone in Moneypoint for their hard work in achieving these results. It has never been more important to save money in our business. This work shows that sustainability projects can be environmentally beneficial and achieve a very positive financial benefit for ESB”.

Modernisation of Clady Hydro Station

Pádraig O’Donnell at Clady’s spillway extension.

P J Ó Domhaill pictured in Clady’s Control Room.

BUILT IN THE LATE 1950s, Clady Hydro Electric Station is situated in the very picturesque Gaeltacht area of Gaoth Dobhair in northwest Donegal. The catchment area of 80km² comprises mainly open moor and bog land and is dominated by the peaks of Sliabh Errigal and Sliabh Sneachta. The 4.2MW station has a typical annual output of 16,000MWh, which can rise to over 20,000MWh in very wet years – enough electricity to power over 3,000 homes with green electricity.

Clady was originally operated and maintained by the staff of the old Gweedore sod burning peat station. Today, thanks to a modernisation programme, which started in the 1990s, the station is successfully operated and maintained by two fulltime staff, P J Ó Domhaill and Pádraig O’Donnell.

PJ looks after the plant maintenance in Clady while Pádraig looks after the rivers and waterways. During the summer months they are supported by Tony McCauley (ESB Networks) and some external resources for large peaks of work.

Since construction in the late 1950s, one of the most important changes made to the plant during this time was the extension of the spillway. The original spillway of 30m was extended to 95m to remove the need for 24-hour operation of spillway gates during periods of high rainfall.

“The 4.2MW station has a typical annual output of 16,000MWh

Other recent modernisation projects undertaken in Clady include the installation of a Bosker Bandit Screen Cleaner automated trash rake. This ingenious machine eliminates the need for labour intensive cleaning of the intake screens to the weir while also aiding the fitting of screens to the weir in early April to prevent smolts entering the canal.

Current work at the station includes the modernisation of the now redundant Siemens S5 PLC (plant digital controller) with a modern S7 PLC. This equipment upgrade coincides with the change out of the control system from the Honeywell Plantscape to the Experion System. This project is part of an overall programme of work being rolled out across all hydro stations.

Work undertaken by ESB in maintaining Clady’s clean waters is widely acknowledged and the high standard to which staff work is evidenced by the presence of both Margaritifera (a freshwater pearl mussel which can live up to 140 years) and Arctic Char (a relation of the salmon). These are both rare species and can only thrive where the river water quality is excellent.

Forthcoming projects scheduled for Clady include a control room upgrade and various plant improvements, with an overall feasibly study of the plant currently underway to plan for the long-term future.

P J Ó Domhaill and Pádraig O’Donnell pictured with the screen cleaner at Clady.

Clady Hydro Station, Donegal.