Pumps are at the heart of every water installation and drive manufacturers are continuously innovating to support the industry and help reduce operating costs as well as improve efficiency. Energy and water have several characteristics in common; they are both essential to modern life; diminishing resources pose a global challenge; sustainability can be improved by reducing the consumption of both. Addressing these issues together can benefit consumers, operators and the environment.
Brett Mernin, Bruce Grobler and Jose Giacomoni, long-time specialists of the use of variable speed drives (VSDs or drives) in pumping applications, look at the challenges facing the modern water and wastewater industries as well as the importance of VSDs in reducing operating costs and improving sustainability.
Traditional energy sources are being supplemented by renewables and some water treatment plants are taking advantage of anaerobic digestion to support their business. At the same time, reducing energy usage is equally important from a cost perspective as well as an environmental position. Furthermore, when energy costs have such a significant impact on water prices for the consumer, making the most efficient use of these resources benefits everyone.
A number of major global trends are directly affecting the water sector. Urbanisation is placing much greater pressure on the existing infrastructure, which means utilities need to make the most of the current install base of equipment and extend its service life. Adding to this, most national water assets have been in place for decades and historically utilities have a reactive approach to maintenance, only taking action when a failure occurs. In many cases, built-in redundancy ensures an uninterrupted supply of water, but the ageing infrastructure needs significant investment.
This can be supported with a proactive maintenance strategy that uses modern data collection and analysis to optimise repair schedules. Looking at the scale of urban growth, this often necessitates new treatment and water distribution sites to be constructed. In this scenario, there is the opportunity to incorporate the latest technology in terms of process and energy efficiency from the outset.
Environmental challenges, primarily droughts and flooding also affect water demand and treatment volumes. Adapting the existing infrastructure to meet the current demands on the water system is ever more difficult. Increasing volumes of drinking water need to be delivered from a diminishing resource while increased rainfall poses a significant risk of flooding, which can lead to environmental contamination from raw sewage. Coupled with greater local regulation and compliance, which are essential for high water quality, the challenges facing the water industry are numerous.
Access to water for drinking and irrigation in areas where water is becoming scarce means extraction rates need to be carefully monitored to ensure water resources are maintained. In countries experiencing significant water shortages, desalination plants may be installed, but they need to operate as efficiently as possible to minimise operating expenses and water costs to the consumers.
Conversely, in regions that are seeing significant increases in rainfall, sufficient to require new pumping stations to be built. Large water volumes require large pumps so achieving optimum hydraulic and electrical efficiency is key to minimising running costs.
The major pain point that utilities have to battle with is rising costs while delivering a basic human requirement as cost-effectively as possible. Water prices are typically governed by a fixed charge, which covers infrastructure and sewage, as well as a volumetric charge for the water consumed. Water supply is a monopoly, there is no competition in the market, so in some countries, government subsidies are used to reduce the price of water, while others have independent pricing regulators.
In all cases, maintenance costs are a constant challenge, the art lies in minimising them wherever possible. Of course, prevention is better than cure, taking pre-emptive action, based on good data, enables planned maintenance to be completed, avoiding unexpected breakdowns.
The ability to detect rag build-up on a pump impeller, for example, enables the controller to briefly run the pump in reverse to dislodge the rag before continuing to operate normally. This feature alone significantly reduces the number of call-outs for technicians, saving their time and fuel.
In addition, the risk of flooding due to blocked pumps is also minimised, which reduces the opportunity for environmental fines. Drives can also detect dry-running and prevent overheating as well as ensuring NRVs don’t slam shut, reducing the opportunity for water hammer, which can cause pipe fractures.
The global water industry depends on reliable equipment and has historically used built-in redundancy to mitigate the effects of any breakdown. The introduction of modern control systems that can drive preventative maintenance as well as reduce operating costs should be considered across the board. VSDs that have been specifically configured for the water sector also offer several advantages that go beyond the well-documented energy savings.
In the US, a national infrastructure bill has released US $55 billion to support renewal of pipework and improvements to pumping stations that include optimising energy efficiency. This is where variable speed drives offer numerous clear benefits by providing specific pump data as well as optimised efficiency.
Improvements to pumping stations can also include upgrades to pumps with revised hydraulics and drive motors. Incorporating permanent magnet technology to achieve IE4 or IE5 classifications needs to be matched with a suitable drive. Careful attention should be paid to the drive because simply upgrading the pump may not be the answer. Some drives do not have field orientated control (FOC) and are incapable of working with permanent magnet systems.
Standing out as a major benefit, retrofit solutions are relatively easy to implement because modern electronics packages are much smaller than the legacy controls, making a replacement in an existing MCC a reasonably simple task. Well-designed control systems are intuitive and commissioning is straight forward, making life easier for contractors and operators looking to achieve the ideal setup.
In some markets, water pricing can be slightly opaque with penalties for using more than twice the expected monthly consumption. Modern pump data analysis can mitigate these penalties by raising the alarm before the trigger point.
Looking at solutions that are available to the market, Control Techniques has developed a range of VSDs specifically for the water industry. The F600 offers many benefits in terms of improved efficiency, data collection, advanced warnings and a five-year warranty, which is attractive to both operators and suppliers/installers. It contains a function block that is specifically designed for pumping applications, simplifying configuration and operation.
Among the challenges faced by the water sector, some are common across the globe, others are more regional. Universally, energy prices have risen and this has a direct impact on operating costs, which affects the price of clean water and wastewater charges. At the same time, inflation is driving labour costs and the number of technical maintenance personnel is reducing.
All of these issues can be positively influenced by tackling inefficiencies and minimising maintenance costs. Upgrading controls offers opportunities for increased remote management and automated maintenance as well as reduced energy consumption. Collectively, benefits can be achieved for operators and customers alike along with the environmental advantages of improved sustainability.
Authors: Brett Mernin, Director of Business Development; Bruce Grobler, Vice-President Sales, Africa/Middle East; Jose Giacomoni, Global Product Manager, all at Control Techniques.