Optimising pump systems for improved efficiency


Given the global rise in energy costs, there has never been a better time to review and assess the efficiency of your pumping systems – whatever their size, complexity or area of operation. Gary Wilde, Technical Services Officer at the British Pump Manufacturers Association (BPMA), explains how a pump system audit can increase energy efficiency, improve CO₂ reduction and shorten capital expenditure payback times.

Pump systems are widely believed to account for 20% of the world’s electrical energy and are the single largest user of electricity within industry across the European Union, consuming over 300 TWh of electricity each year, which in turn accounts for over 65 Mton of CO₂ emissions.

It is also well documented that rotodynamic pumps, which account for 80% of the installed base, are typically between 20-30% oversized. There is, therefore, the potential to save significant amounts of energy.

When building a new pumping system, most pumps are selected with a safety factor for potential future uprates or to allow for wear in the pump or fouling of the system. Often, many different parties are involved in specifying and building a system, and the safety factor can grow exponentially. This results in the pump delivering much higher flows than required. There may also be the need to vary the flow due to process conditions or varying heating and cooling needs within buildings.

Traditionally, throttling is used to regulate flow in a pumping system. While throttling reduces the flow, the motor still runs at full speed and works even harder as it must work against a restriction. By using a variable speed drive (VSD) to reduce the speed of the motor, no more energy than necessary is used to achieve the required flow. A centrifugal pump running at half speed consumes only one-eighth of the energy compared to one running at full speed. Utilising a VSD is the simplest and most economical way of controlling the pump and matching it to the pump system.

Across most industrial sites, around two-thirds of the total energy consumption is used to power electric motors, with many powering pumping systems. The overall cost associated with operating these essential pieces of equipment throughout their life span can be broken down as 5% for the initial purchase/installation costs, 10% for ongoing maintenance and a massive 85% for the energy used to run them. Clearly, any reduction in the energy consumed by electric motors is important, and in addition to the savings made through employing VSDs, upgrading older motors to more efficient modern designs can see a reduction in energy use of as much as 30%. It is also evident that many pumps and motors are constantly operated at full power, irrespective of process needs, and so across the installed base, there is the potential for significant energy savings, savings which can, in turn, drop to the bottom line and increase the profitability of any business.

Clearly, the key to realising potential energy savings is understanding where they can be made. And that is where an energy audit comes in. The purpose of an energy audit is to reduce operating costs by reducing energy consumption, and the government has estimated that most companies can reduce their energy consumption by 10% to 20%. Indeed, energy audits conducted by BPMA members have shown that savings from 30% to 50% are not unusual. So, when deciding whether or not to carry out an energy audit, a good starting point is to assume that you will save at least 10% of your current energy consumption. By reviewing utility bills, you can get an indication of the savings to be made and the investment that you should be prepared to put into the auditing process.

BPMA involvement

Given the amount of energy pumps consume through their normal operation, and the potential for energy efficiency gains within pump systems, the BPMA has developed a Certified Pump System Auditor Scheme (CPSA).

Through the CPSA, pump engineers are being trained to correctly assess the efficiency of pump systems and to provide appropriate recommendations to improve those systems’ efficiency. The CPSA accreditation is achieved by completing a four-day residential course, followed by the satisfactory completion of a pump system audit. Only then can ‘Certified Pump System Auditor’ status be achieved.

Within the full Energy Savings Opportunity Scheme guidance document, covering the energy assessment scheme mandatory for large organisations in the UK, the ISO 14414-Pump System Energy Assessment standard is referenced as an auditing methodology that can be accepted by Lead Assessors approved by the Environment Agency. Accordingly, it is hoped that CPSA accredited persons (trained according to the IS0 14414 standard) will be recommended by Lead Assessors to undertake the pumping system elements of company-wide energy audits.



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