Water & Wastewater Treatment Magazine
Issue link: https://fhpublishing.uberflip.com/i/801555
8 | APRIL 2017 | WWT | www.wwtonline.co.uk Comment T his month marks a long-awaited milestone for many in the industry as the non-domestic retail market opens for competition. While it will take time before data becomes available on switching rates and the level of savings being achieved - and any view can be taken on the success of the development – it is certainly worth celebrating the collaborative, methodical and relatively seamless way that the industry has reached this point. That's due in no small part to Ben Jeffs, chief executive of MOSL (see Industry Leader, p19) who has brought his energy sector expertise to bear on the central machinery behind the newly-expanded market. There's a lot at stake, and Yorkshire Water's late change of plans on the future of its business customer base Change in the air (see news, p4) illustrates that tough decisions still lie ahead for the sector. On the wholesale side, however, the industry's substantial and growing ability to generate its own power is cause for much more optimism. What's more, generative capability comes with the ability not only to make assets more resilient but to add to profitability through demand response initiatives with the grid. Therefore, the prospect of storing the energy generated so it can be used or supplied to the grid at the most opportune time is extremely appealing. That's why our round table discussion on energy storage and on-site generation (p14) is so timely. As we heard, participants from across the spectrum of water companies are keen on using battery storage, if the technology can be made more economical to install, helping to support the business case. Speaking of business cases, this issue also sees us get under the skin of resilience (p35) a tricky concept to nail down, but one which it is safe to say will feature in all water company business plans for PR19. It is one thing to work out how to make assets and systems more resilient against risk, but another to calculate exactly the James brockett eDItor JamesBrockett@fav-house.com Twitter: @wwtmag Expert view sponsored by martin richardson, Water Framework manager, Drives & controls, abb Ltd You may recall how some leading brands in the automotive industry misled the market with vehicle emission efficiency levels. But what if the same thing was happening in the water and wastewater industry? Do you really know the true efficiency of your pump systems and the impact and interaction of individual components, such as transformers, electric motors Is the automotive industry the only one massaging its efficiency figures? and variable speed drives (VSDs)? If not, then any aspiration or plans you have to cut energy costs could be severely threatened. Here's an example of the problem. If you study the standard EN 50598-2, a relatively new standard relating to the efficiency of VSDs and VSD systems, there is clearly flexibility allowed in the calculations/measurements and corresponding efficiency values that are published. The point to note is that a VSD's switching frequency can have a huge effect on the efficiency of the drive system. ABB uses 4 kHz as a default switching frequency and typically delivers its drives using this figure. However, other manufacturers choose to use 2 kHz. This lower switching frequency improves the figures that the manufacturer can publish for the VSD's efficiency. However – and this is the bad news - the lower switching frequency has a negative impact on the overall electrical system efficiency. This is because the standard does not consider the entire system variations and the interactions of other components such as transformers, motors and filters. Going back to the automotive industry, most of us are aware that the way we drive affects the 'actual' miles per gallon that we can achieve. There is far more to consider such as fuel type, inflation level of tyres, roof bars and weight of passengers/luggage. The individual setup and use of the car clearly affects the efficiency. And so it is with your VSD arrangement. Drives without chokes and filters seem to be more efficient, but in practice this is not the case. Furthermore, 12-pulse and 6-pulse drives seem to be more efficient than low harmonic drives because you do not have to include the transformer losses. However, this is not how it is in practice. The message is clear: don't believe everything that you read. Dig beneath the actual published efficiency figures for each component that is powering your pump system. For more information visit ABB's dedicated system efficiency webpage: http://bit.ly/TOTEX_System_Efficiency value of the risk avoided and therefore how much investment in that process or protection is worth. As Brendan McAndrew of MWH points out in our Digging Deeper feature, a relatively small failure – akin to the proverbial missing horseshoe nail – can lead to a major failing, such as a pollution incident that leads to environmental damage and a multi-million pound fine. In such circumstances, understanding what makes your system susceptible to larger failings is the key, rather than worrying about every potential flashpoint. Finally, this issue of WWT sees our first CPD-accredited article: on the optimal design of pump sumps (p38). It's important for professionals of all stamps and seniority to keep learning throughout their career, and so I would encourage as many readers as possible to take the time to digest the information and then log on to the website, where you can answer questions on what you've learned and receive your Continued Professional Development (CPD) points. We hope this will be the first of many opportunities for WWT to bring you ongoing and relevant learning materials.