Danfoss pumps reduce energy costs and CO₂ emissions in Hawaii

Like many other island communities, electricity prices on Hawaii Island are high. Although renewables are on the rise, local utilities still rely heavily on imported oil to power generators. Fuel represents about half of the typical electricity bill – a significant cost for RO water producers.

Community managers were interested in the most energy efficient solution available both to reduce its energy bills and its carbon footprint. Located on the exclusive Kona-Kohala Coast, the community celebrates traditional Hawaiian values and design, and its owners are dedicated to the preservation of the area's unique environment. By reducing the power consumption of its golf course's irrigation system, community managers could save unnecessary expenses and at the same time reduce the community's carbon emissions.

Could Water Works find a way to reduce the community's power consumption – and deliver not only financial and CO₂ savings but a solid business case for a retrofit, too?

The community previously relied on multi-stage centrifugal pumps deployed across four parallel arrays, all with energy recovery devices (ERDs), to filter brackish water from underground wells. Water Works' lead engineer for the project, Mark Maki, was familiar with Danfoss APP pumps and suggested retrofitting one of the four centrifugal pumps to prove the retrofit concept – and deliver rapid energy and CO₂ savings.

"Depending on the season, the four-array plant usually runs at 50 – 75% of capacity," explains Maki. "With a total capacity of 900 gallons per minute distributed across four arrays, there was little risk for the customer to retrofit one of them with APP technology and much to gain. We decided to install two APP 26 pumps – at 25 HP each for a total of 50 HP – on one of the arrays to replace one of the older centrifugal 75 HP pumps."

"For some companies, such a retrofit might be demanding. The existing arrays were built around centrifugal pumps with different inlet and outlet connections, so we did have to change some piping and electrical. But Water Works thrives on such projects. We don't do "catalogue" water treatment plants, and we have a lot of smart people who think outside the box to find the best solution for every project." 

The retrofit went on line at the end of May 2017 and has been running practically non-stop since "The APP-driven array has become the workhorse of the entire plant," says Maki. 

"With energy savings of 38%, the community is running it nearly 24/7 to reduce usage of the three centrifugal arrays and maximize cost and CO₂ savings. And the APPs are happy to cooperate. Danfoss assured us they could run continuously, and that's what they've done. These are low-maintenance pumps with long service intervals, with reliability we and our customers can bank on."

Total cost of ownership is a key parameter for Water Works, whose managers calculate a payback time of just 18 months for the first retrofit. "The return on investment for this retrofit is convincingly fast," says Maki. "Since two arrays are typically operating 24/7, the payback for retrofitting a second array will also be about 18 months. This second retrofit is planned for the near future."