This post covers the US Department of Energy (DOE) notice of proposed rule-making for pump efficiency. On June 13, 2011, the US DOE issued a Request For Information (RFI) regarding the establishment of energy conservation standards for pumps. (http://www.gpo.gov/fdsys/pkg/FR-2011-06-13/html/2011-14553.htm). After viewing the information found on the Federal Register RFI, I have serious doubts about some of the estimates presented along with the value of establishing minimum pump efficiency standard.
The RFI states there are other regulatory programs that provide energy efficiency information such as the Energy Star labeling program developed by the US Environmental Protection Agency and DOE. The Energy Star labeling can be found for a variety of products such as refrigerators, dishwashers and dryers.
The Energy Star labeling program deals with appliances that are typically standalone devices. For example, your refrigerator doesn’t work with any of the other appliances in your house, making it very easy to determine how much power it will take to operate a standalone appliance in a year.
A pump on the other hand, is part of a total system that may be called on to operate in a variety of ways during a year, with a variety of flow rates through the pump. As a result, a program similar to an Energy Start labeling program for pumps would have limited value.
The RFI continues that pumps are not covered under the Energy Star labeling. It further states in “The US DOE has the intention to evaluate the energy savings potential of energy conservation standards, labels, or both, for commercial and industrial pumps.” They continue with “After public comment on this RFI, DOE will consider developing test procedures and energy conservation standards or labels for this equipment.” (Bold & italic entered by the author.)
One area in the RFI that I have real concerns about is their estimation on the availability of pump efficiency improvements. It states:
“Reports cited in this RFI estimate potential energy savings from pumps of 10 percent to 50 percent. Because these estimates include a variety of system and pump efficiency measures including proper sizing of equipment, the lowest energy savings estimate of 10 percent, based on an European Union (EU) study of pump efficiencies (cited in (c) below), is assumed for the pump efficiency alone.”The reports cited in the statement estimating a potential energy savings from pumps of 10 percent to 50 percent are based on finding of a variety of Pumped System assessments. The energy savings are based on system related issues. A pump does not know or care how the energy it supplies to the system is used, it only reacts to the system’s needs.
For example if a pump operating with a 100 psi discharge pressure, delivering a flow rate of 300 gallons per minute and has an 80% pump efficiency, that pump consumes a given amount of energy. If the system requires 300 gallons per minute at only 60 psi a control valve could be installed to reduce the pressure by 40 psi to what is required by the system. The pump still remains 80% efficient but approximately 60% of the supplied energy by the pump to the system is wasted across the control valve. Remember, the purpose of the control valve is to reduce the excess pressure provide by the pump to that needed by the attached system.
In this example there could be a 40% saving in energy consumption by running the pump at a lower pressure and eliminating the control valve. To accomplish this, an adjustment must be made to the pump so it only produces the 60 psi required by the system. This can be accomplished by either changing the pump impeller diameter or by changing the pump rotational speed. These types of decisions are made when performing an assessment of the total pumped system.
What I really disagree with is the statement “… the lowest energy savings estimate of 10 percent, based on European Union (EU) study of pump efficiencies is assumed for the pump efficiency alone.” What they seem to be saying is based on their experience they could expect at least a 10% system efficiency improvement by improving the pump design. Earlier in the RFI it is stated:
"Pump system efficiencies depend on design factors such as surface roughness, internal clearances, solids handling capability, curve shape, mechanical shaft seal losses, and other factors.The European Guide to Pump Efficiency for Single Stage Centrifugal Pumps referenced in the RFI statement above appears to provide an indication to the pump buyer if the pump being supplied by the manufacturer is the most efficient pump. The main focus of the article is to select a pump where the system requirements are close to the pumps Best Efficiency Point based upon the pump design. I was unable to see how a pump’s efficiency could be improved by improving surface roughness, internal clearances, curve shape or mechanical seal losses.
Analyses based on data from the 2003 EU ”European Guide to Pump Efficiency for Single Stage Centrifugal Pumps ”show that for typical flow rates it is reasonable to expect an efficiency improvement of 10 percent from the mean pump efficiency to the maximum practically attainable level."
In 2009, I attended the Hydraulic Institute (the North American pump manufacturers association) annual meeting in Marco Island, FL. During that meeting I sat in on a session presented by EuroPump (the European pump manufacturers association) describing a recent statute passed by the EU to increase pump efficiency for industrial centrifugal pumps.
What was really interesting, is the EU enacted the statute without any comments or discussion with the pump manufacturers. I find it amazing that a group of bureaucrats can state that pump efficiency can be increased by 10% simply by changing internal clearances, increase the smoothness of the castings and changing the shape of the pump curve. If it was that simple it would already have been done!
Rather than looking at new ways to develop test procedures and energy conservation standards or labels for pumps the US DOE should concentrate their efforts on their Superior Energy Performancecm program. The Superior Energy Performance program is based on the recent Energy Assessment for Pumped Systems ASME E-2 2009 standard which concentrates on the evaluation of the entire system rather than concentrating on just the pump.
Pump manufacturers, as well as owners and operators of pumps and pumped systems, have done an excellent job of developing a variety of test standard and ways of presenting the data. The various standards have been developed by the ASME, HI, ANSI, and ASHRAE over the years to meet the needs of both the manufacturers and buyers of pumps. The standards are also reviewed on a periodic basis to ensure they are current and reflect the latest technology. Anyone who has been involved in the development or review of a standard will attest to the care to ensure the standard meets the needs of everyone concerned.
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Industrial Pumps has a capacity to handle suspended solids and abrasives without damage to the product or the pump. mainly used for various industrial applications such as condenser, chilled, and hot water systems in HVAC and process secondary pumping.
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