Water and Energy: A Crucial Conversation
Lack of communication (and much-needed funding) often prevents water providers from efficiently and cost-effectively managing their energy use.
By Dan Rafter
Allan Hoffman knows why so many municipalities consume far too much energy when moving drinking water through their systems: Water people and energy people simply don’t spend enough time talking to one another.
And this is a problem that Hoffman, a visiting professor of renewable energy and desalination at the Gulf Organization for Research and Development in the Arab state of Qatar, says has gone on too long.
And it’s one that will continue to vex municipalities as they try to reduce their energy consumption while also trying to deliver water.
“For a long time, energy people thought minimally about water. They didn’t think about how much energy it takes to move water,” says Hoffman. “On the other hand, water people never really thought seriously about energy. They just figured that a diesel engine would always be there to deliver their water. We’ve gotten away with that approach for a long time. But I don’t think we can any more.”
Hoffman, who recently retired as a senior analyst at the US Department of Energy (DOE) and is now writing a chapter on the water-energy nexus for a new book about energy poverty, is far from alone in this belief.
Municipalities are spending a lot on the energy required to both treat wastewater, and deliver drinking water to their customers. In a 2012 report, the Energy Sector Management Assistance Program (ESMAP) found that electricity costs usually account for 5% to 30% of the total operating costs of water and wastewater utilities. And that cost is usually higher in developing countries, often reaching up to 40% or more.
It’s essential, then, for water utilities to take whatever steps needed to reduce the amount of energy it takes to treat and deliver water. This is especially pertinent in today’s struggling economy, a time during which most municipalities are desperate for any cost savings they can find.
|Photo: American Water
High service pump station
The good news? The ESMAP found that water utilities generally see their energy consumption drop by 10% to 30% after they take some of the more common technical measures to boost their energy efficiency. And these measures typically pay for themselves within one to five years.
Municipal officials and manufacturers agree that pumps represent the biggest energy drains for water utilities. These devices play an obviously key role in delivering and treating water. But they also require a lot of energy.
Therefore, water utilities can enjoy the greatest amount of savings by updating to more efficient pumps, properly maintaining their pumps, and carefully monitoring how they are using these essential pieces of equipment.
There are challenges, though. Many water utilities are still relying on older-model pumps that simply aren’t as efficient as newer models, but balk at paying the upfront costs required to invest in more efficient versions. Other utilities simply resist any change; while, still, others don’t realize the wasteful nature of their current pumps.
And then there are the many municipalities that still treat water and energy as separate issues, Hoffman says.
“You just can’t separate the two issues,” he says. “Energy and water are both critical resources for sustainable economic development. You have to plan for them jointly. You can’t just have a water group and an energy group and not have them talk to each other. In general, though, water has been an issue at the state and local levels, while energy has been mostly a federal issue. That’s the problem. Everyone needs to talk to each other more.”
New Tech, New Efficiencies
Pumps work hard. It’s why they consume so much energy. Just ask Dale Conway, vice president of engineering with Thompson Pump in Port Orange, FL.
“Pumps can have such a large impact on the energy that water utilities consume. Traditionally, these pumps operate upwards of 10 to 12 hours per day every day,” says Conway. “Some operate more. Some operate less. To have a pump running for that amount of time, though, you can see why it would consume so much energy.”
The good news, though, is that water utilities can often lower their energy usage dramatically just by replacing inefficient pumps with newer models that consume less energy while providing the same amount of power, Conway says.
A water utility, for example, might be relying on older pumps that are now operating at 50% efficiency. Utilities can bring in new pumps that operate at 85% efficiency and immediately enjoy significant energy savings, Conway says.
“A lot of times, it’s as easy as taking out a pump that is installed at the site and replacing it,” says Conway. “You don’t have to change a lot of the piping systems that way.”
And there are plenty of options today for utilities that want to upgrade to more efficient pumps, Conway says.
“The technology is always improving,” he says.
There are two main parts of a pump that determine how efficiently it will do its job, Conway says. First there’s what Conway calls the heart of any pump, its impeller. Then there’s the casing around the impeller, the skin that protects this heart.
“Just in the last 20 years, manufacturers have put in a lot of engineering work in those two areas to boost the efficiencies of pumps,” says Conway. “The industry has been able to raise efficiencies from the 50% range to the middle 80% range.”
A substantial change has come in the shape of pumps’ impellers, Conway says. Manufacturers used to build impellers with vanes that looked like the spokes on a bicycle tire. They all extended from the center in a straight line.
That design moved water. But it did so inefficiently. So manufacturers upgraded the impeller. Instead of a straight line, today’s impeller vanes are curved. Known as swept vane impellers, these devices move water far more efficiently. They move water while reducing turbulence.
At the same time, engineers made advances to the casing around these impellers. Instead of a traditional circular casing, today’s more efficient pumps boast a conch shell design. These casings expand from a small point, growing larger as they near the final discharge point. This combination of a conch shell casing and swept vane impeller results in a water pump that is far more efficient than were older models.
These tech advancements mean that utility managers relying on older pumps can achieve rapid energy savings simply by upgrading to modern middle-of-the-road pumps. This is crucial in today’s tough economic times; utilities don’t have to spend a small fortune on top-of-the-line pumps to see their energy bills fall.
Conway says that he’s worked with utilities that were relying on pumps that were 30 to 40 years old to deliver their drinking water. This, he says, is something that’s both good and bad.
On the bad side, when these pumps do break down—and this is inevitable considering their advanced age—the municipalities relying on them can no longer find replacement parts. The pumps are simply too old and are no longer being built. In many cases, the companies that built them are no longer in business.
The good side of this? It forces water utilities to upgrade to more efficient pumps. This might not seem like good news for utility managers. But they will be happy to see the lower energy bills that come from relying on more efficient pumps. And these energy bills will help quickly mitigate the upfront costs of buying new pumps.
“Not too long ago, we got a call from a municipality that had pumps from the 1940s,” says Conway. “They were asking for new parts. They couldn’t find anything online. They ended up replacing the old pumps with our technology, and now they’re enjoying lower energy bills.”
The Importance of Testing
American Water is no small utility. The utility provides drinking water and wastewater services to an estimated 15 million customers located in 30 states and portions of Canada. So when this utility, based in Voorhees, NJ, decides to reduce its annual energy consumption by 8% by the end of 2016, it’s momentous news.
And when American Water wants to reduce its energy consumption? It makes pump maintenance and upgrades a priority.
“We feel that the pumps by far account for the largest majority of our energy expenditures,” says Doug Potts, senior design engineer at American Water. “We use electricity for our office buildings, of course. But that’s a small drop in the bucket compared to the electricity we use in delivering our water.”
Potts estimates that upwards of 90% of the energy consumed by American Water is used for the pumping of water.
“Water is heavy. It requires a lot of energy to pump it,” says Potts. “The other electrical loads in our treatment plants, the electricity we use to operate our valves and run our flocculators, require a small amount of horsepower by comparison.”
To make sure that their pumps are working efficiently, managers at American Water utilities engage in regular wire-to-water efficiency testing of these machines. This is the most effective way to measure just how efficient a pump is. And it also helps utilities determine which pumps need to be replaced, Potts says.
This testing has become routine now at American Water utilities, with utilities expected to test their large water pumps once every two to three years. Before the decision to reduce energy consumption though, testing was—as Potts says—“hit or miss”, depending on the maintenance group at American Water’s various state utilities.
“It is important that we keep testing on a regular basis,” says Potts. “Ideally, you’d like to test the efficiencies of your large pumps every two to three years. Then you can chart and see if there has been any steady decline in their efficiency or if they are holding steady.”
What’s most compelling is what American Water’s testing has found. The largest pumps at the utility tend to operate at an efficiency level of about 65%, Potts says. According to his own research, large water pumps at utilities across the country tend to operate at about 60% efficiency, meaning that American Water’s pumps are consuming less energy on the whole than is typical.
But Potts has also discovered that utilities’ older pumps aren’t necessarily less efficient than their newer ones.
Testing has found several old pumps operating at efficiency levels at or above those of newer pumps because they have been maintained well over the years.
“As it turns out, being old does not necessarily mean that it is inefficient,” says Potts.
What kind of maintenance have these older pumps received that has kept them running so efficiently? Potts says that maintenance workers have regularly rebuilt these pumps over the years, replacing, say, their bearings and wear rings.
Wear rings play an especially vital role in the efficiency level of water pumps, Potts says. When wear rings are tight, they create tight clearances in their pumps. But if the wear rings have loosened over the years, pump clearances can open too wide. Pumps then recirculate water from the discharge side to the suction side. And that can hurts a pump’s efficiency.
But the regular maintenance of their pumps won’t help utilities reduce their energy consumption if these utilities don’t first determine how best to operate their pumps for their particular systems, Potts says.
And those utilities that don’t operate their pumps properly won’t realize significant energy savings even if they order the most-efficient pumps on the market, he adds.
“It’s not just about maintaining the pumps,” says Potts. “You can have a pump that is brand-new in tip-top condition. It might have the best efficiency available. But if you are not operating it as it was designed to be operated—if you are operating it at the far right end or left end of its curve—you will not realize the efficiency levels you want. The key is to operate that pump at the best efficiency point possible.”
The Holistic Approach
Tony Naimey, global mechanical technology leader for the water business group of CH2M Hill, an Englewood, CO-based consulting, design-build, operations, and program-management firm, says that every water utility should strive to meet a triple bottom line: one that includes specific goals for sustainability, economics, and customer and community impact.
The only way to be successful in all three of these areas is for utilities to take a holistic approach to running their facilities. This means selecting not just the right pumps, but taking steps so that they are operating this equipment at right speeds and at the right times of day.
But utility officials can’t just concentrate on their pumps if they want to reduce the energy their utilities consume, Naimey says. They must also look at their conveyance piping system to see if it upgrades should be initiated. They must look at whether they can make changes to the times of the day when they pump water; they might save valuable dollars by increasing pumping during off-peak hours, when energy costs are lower.
They must train their employees properly in how to best maintain and operate all the equipment needed to deliver and treat water.
“When all that is taken into proper consideration, when a utility performs its due diligence you get your best chance of achieving those triple bottom line goals,” says Naimey.
Utilities that want to operate at peak efficiency levels will benefit from employing integrated controls that analyze their conveyance systems, pumps, and water needs. The controls can then pinpoint the optimum number of pumps needed, while also determining the best operating speeds in order to enable optimal efficiency, Naimey says.
|Photo: American Water
Staff perform wire-to-water testing
as part of routine maintenance.
Communication is the key to boosting efficiency, Naimey says. Utilities today need to work directly with pump manufacturers to custom design pumps for their systems. Doing this is the best way for these utilities to reduce their energy expenses.
“They can work on vane angles, impeller specifications,” says Naimey. “I am the technology steward for our mechanical group. I make sure that the pump manufacturers and motor manufacturers are in agreement and coordinated. That way there are no surprises. That way the goals are consistent when it comes to the pump efficiency that we want to achieve.”
Like other experts interviewed for this story, Naimey says utility officials make a mistake when they simply select the most efficient pump possible without looking at the bigger picture of how they are operating these pumps.
Those who take the wire-to-water approach—looking at the total energy costs from the beginning to the end of the delivery or treatment process—will be far more likely to experience money-saving boosts in efficiency, Naimey says.
The question is, are utility operators taking this holistic approach?
The answer isn’t a surprising one: Some are. Some aren’t.
“I have asked that very question to the major pump suppliers that serve our water market,” says Naimey. “There are some very good engineers and engineering companies out there that do take this longer view. But the suppliers will tell you that there isn’t that consistency there. Many look at pumps in a deeper way. But others perhaps place less emphasis on a deeper understanding of the ramifications associated with pump selection.”
A More Efficient Future?
What does the future hold for water pumps and their efficiency levels? Conway says that advancements will continue to be made, but not always in efficiency levels.
For instance, Conway predicts that pump manufacturers will make dramatic improvements in the metallurgical technology of their pumps. In other words, pumps will be made of better materials. As an example, Conway points to the problem that water utilities have had with zinc.
Many pump materials have long had zinc in them. Over time, water will attack the metal of pumps, sending some of that zinc into drinking water. Utilities don’t want their customers consuming zinc, so many manufacturers are now using only zinc-free metals in their pumps.
Conway expects to see more of these are the kind of metallurgical improvements in the future.
At the same time, efficiency levels will constantly trend upward in newer model pumps, Conway says. Consider that just two years ago, the United States passed a law mandating higher efficiency standards for any electrical motor manufactured in the country. As motors improve, efficiency standards will rise, Conway says.
“If a municipality has a drinking water system running monthly energy bills of $5,000, it could realistically convert to a more efficient pump and motor and cut that bill in half every month going forward,” says Conway.
Hoffman, Conway, and Naimey, though, all agree that utilities will always consume more energy than necessary if they don’t first invest in that crucial holistic view of their delivery and treatment processes.
And, as Hoffman says, until energy people and water people start talking together seriously about the energy it takes to move water—and how to reduce that energy—utilities won’t ever maximize their energy savings.
That would be a shame, especially as utilities around the country look for ways to reduce their budgets without decimating their staffs.
“Water as a whole is an issue that is not going away,” says Hoffman. “Water might turn out to be the big issue of the 21st century. There is not a shortage of water. We are a water-rich planet, but we are not delivering or using that water properly.”
Author’s Bio: Dan Rafter is a technical writer and frequent contributor.