Strategic energy options
Ewan Group considers efficiency savings through pump optimisation
With Ofwat poised to wring yet further efficiency savings from the water companies during AMP4, every way is being explored to meet the demanding targets proposed. Having exhausted all immediately apparent options during AMP3, scope for the water companies to cut back further is limited, according to management and technical consultant to the utilities, Ewan Group. With the regulator pegging back the water companies' submissions by about 50% on average of the sum they had requested, and setting even higher targets for efficiency savings - by around 5% for capex and 10% for opex - AMP4 is going to demand a far more rigorous approach from companies. Having secured gains from tariff negotiations and switching suppliers, water companies' options for cutting the amount they pay for energy have been exhausted and the focus must now shift into areas like operational optimisation to reduce overall costs.
Among possibilities is implementation of a more strategic approach to energy efficiency. Specifically, Ewan advocates that application of a proven pump optimisation programme warrants closer scrutiny. "Given the need to explore every avenue to maximise efficiency, water companies could consider pump optimisation to improve operational efficiency and reduce costs. This is an area that we have already done a lot of work in and one that could be developed a lot further," explained Ewan's technical director Mark Randall-Smith. "A project undertaken for Yorkshire Water involving operational and pressure management has previously demonstrated how successful this can be. The results would suggest this is perhaps an area in which greater resources should now be applied, given the current financial constraints facing the industry."
While comparatively small in scale with some 4,000 properties served, the study proves valuable, Ewan claims, owing to its variable circumstances, split urban/rural characteristics and composition of several different cascading pressure districts. The system included five pumping stations and six reservoirs and, because of the complexity of operation, Yorkshire Water anticipated there would be scope for improving the way the pumps operated.
The results of the study suggested savings of up to 40% could be achieved by rationalising the trigger-on and trigger-off levels at pumping stations within a given system, at the same time preserving the minimum emergency storage requirements as assessed by Yorkshire Water. Ewan's Genetic Algorithm (GA) optimisation technology has the potential to evaluate not just optimal pumping and pressure zoning arrangements, but also alternative capital options (such as increasing storage volume) or pressure zoning options. This allows the overall optimal system configuration to be identified and implemented, to maximise savings. An optimised re-zoning and pressure management solution using GA at Batley for the same water company also resulted in a 35% reduction in leakage and a payback period of 15 months.
In an earlier project for Essex & Suffolk Water, optimised system reinforcement of any of 2,500 pipes in the north-east London zone, to overcome projected pressure deficiencies, saved £2M or 49% against the manual solution. Ewan has applied the technology further afield for the regional municipality of York in Ontario, Canada. Here, following earlier studies to optimise resources and strategic supply routes to the region, the firm carried out an extensive optimisation of the regional infrastructure needed to meet water demands in 2031 when population is projected to double. The optimisation used GAs applied to a calibrated hydraulic model, which was developed as part of the project. Capital and operational expenditure was considered so that preferred solutions reflected 'whole-life' costs, primarily those relating to pumping energy, rather than capital costs alone. While no directly comparable cost for a manual solution was available for the ultimate planning horizon of 2031, the phased solution from Ewan for 2011 determined a cost of Can$102M instead of the previous manual solution cost of Can$156M - a saving of Can$54M or 35%.
Typically, according to Ewan, where this technology has been applied, overall scheme savings of between 10-30% can be delivered. The extent to which this is achieved obviously depends on the complexity and individual characteristics of each particular case. Another strategic option for water companies arises from the possibilities they have within their asset base to deliver small-scale hydro-electricity outputs, as undertaken successfully by South West Water at Mary Tavy. The plant works with smaller stations at nearby Morwellham and Chagford to produce nearly 3,500kW of electricity from the water resources of Dartmoor.
This decision to purchase and refurbish a hydro power site not only establishes the firm as a supplier to the National Grid, increasing dramatically its production of renewable energy, but as such gives the company additional tariff benefits on its whole supply, which equates to significant energy savings. The programme at Mary Tavy is the first part of a scheme to increase production of renewable energy at a total of nine existing hydro-electricity sites. In addition, a new station is being built and there are plans for a further four. It would seem logical that similar opportunities are available throughout the country and the enterprise demonstrated by South West Water should serve as an example of what can be achieved. Ewan's approach to these latest efficiency challenges is based on a far greater understanding of the bigger picture as part of a wholly integrated strategy. This means acquiring a much deeper understanding of the potential of assets. It also means developing a better understanding of sustainability and future proofing of assets, along with integrating the preparation of maintenance and opex regimes. Also integral to success is the use of better performance indicators, establishing a more robust understanding of the mechanism of asset failure and deterioration rates, evaluating capex and opex trade-offs, and determination of the effectiveness of various interventions - short and long-term. Now the efficiency squeeze is really on, is it time for the water companies to take these approaches seriously? Ewan certainly believes it is.