Commercial and industrial pumps are used in a wide variety of applications such as irrigation, circulation of hot and cold water in commercial buildings for heating and cooling, and pressure boosting in high-rise apartment buildings.
In 2016, DOE published the first-ever standards for pumps based on efficiency levels negotiated by manufacturers, efficiency advocates, and other stakeholders. The standards, which will take effect in 2020, apply to clean water pumps between 1 and 200 horsepower and will eliminate the least-efficient 25% of pump models from the market.
The standards are based on a metric called “pump efficiency index,” or PEI, which is a ratio of the power consumption of a given pump to the power consumption of a pump that just meets the minimum standards. A pump with a PEI of 0.9, for example, would consume 10% less power than a pump that just meets the minimum requirements. The PEI metric incorporates not just the power consumption of the pump itself, but also of the motor that drives the pump and any controls.
The principal way to improve pump efficiency is to hydraulically redesign the pump to reduce losses. Beyond improvements to the efficiency of bare pumps, large energy savings can be achieved through the use of variable-speed drives in variable-load applications. In variable-load applications, the change in load is typically met by throttling the pump using valves. This control approach leads to significant energy waste. In contrast, the use of a variable-speed drive allows for reducing the speed of the pump to match the load. Reducing the speed of the pump can yield significant energy savings since power decreases with the cube of the speed. The energy-saving benefits of variable-speed drives are captured in the PEI metric such that a pump with a variable-speed drive will have a significantly better (i.e. lower) PEI rating than a constant-speed pump.