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Energy Savings

Welcome to Environmental Protection’s Quiet Waters blog. "Only in quiet waters do things mirror themselves undistorted. Only in a quiet mind is adequate perception of the world.” – Hans Margolius

There has been a lot of talk recently about energy and energy savings. The aftermath of Hurricane Katrina taught us all just how volatile energy costs can be. When gas goes up, so does everything else.

But how much energy is used in water and wastewater plants? Not much, right? Wrong. As paraphrased from a a previous blog: Water and wastewater facilities' energy usage equates to 56 billion kilowatt hours (kWh) and $4 billion. Pumping represents more then 87 percent of a water utility's energy usage, and aeration and pumping represent more than 70 percent of a wastewater utility's energy usage.

Do you know if your plant is efficient? Many operators don’t because the energy bill is routed through accounting, and most facilities don't have a benchmark to judge their usage by. Both of these problems can be solved easily. First off, get accounting to send the bill to you and study it closely. Second, EPA has extended the Energy Star program into the water and wastewater market, allowing you to compare your facility against others. Studies have shown that just monitoring a criterion against a benchmark can affect its behavior.

But what do you do for larger energy savings? Many plants only have a single meter at the point of utility tie-in, and it is used for billing purposes. More power meters will allow you to see where energy is being used and when. Of course, the equipment you are using can make a big difference. Many facilities are using inefficient means to aerate. This could be the blower, aerator, or diffuser. Also, pump impellers can have an impact. Once these have been examined, look at variable frequency drives. Did you know that for a pump or blower, a motor at 80 percent of full speed only uses 50 percent of full power? That is why VFDs are so popular. To make them more attractive, many power utilities provide a rebate for using VFDs.

How you control a facility also can save energy and money. A lot has been written about dissolved oxygen control and energy savings in aeration basins. This is all good stuff. Also, changing the time when towers are filled can eliminate or minimize demand charges.

What if you want serious energy savings? For these opportunities, advanced modeling is the key. Pump modeling or multi-parameter aeration basin control can have a dramatic impact on energy savings.

Your facility may not be able to purchase more efficient equipment outright, but engineering firms and suppliers are starting to look at performance contracting,, which uses energy savings to pay for upgrades. In this model, a facility is given a guaranteed energy savings from the supplier or engineer. Then the supplier or engineer provides all the equipment and pays for the installation cost. Once installed and running, the energy usage is measured. If the energy savings meets or exceeds the guarantee, then the facility pays the supplier or engineer from the energy savings until the system is paid for. If the energy savings is less then the guarantee, then the facility is paid the difference between the energy usage and the guarantee. Performance contracting can provide a win-win solution for the facility and the supplier or engineer.

So what are your experiences with energy savings? Are you looking at your energy bills? If so, what do you see? What is your facility's viewpoint on energy?

Posted by Grant Van Hemert, P.E., Schneider Electric Water Wastewater Competency Center on Apr 06, 2010

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