Harnessing Throw-Away Energy

Check out Mike Sherer’s cover story on flight-type warewashers in this issue, and one of the things that jumps out at you is the amazing improvement in water efficiency over the past decade. When we covered this same category back in July 2001, most of the models in the story were using in the neighborhood of 325-350 gals./hr.

This year, that number is more like 125-135, and a couple models have settings that get you down below 100.

After you crunch the numbers for dishes per hour and so on, the bottom line is that today’s flight-types use roughly a third as much water as they used to—and the energy needed to heat that water drops proportionately, too.

None of which even reflects a really exciting new technology coming down the road. Three of the manufacturers in the warewasher story now offer optional waste-heat recovery systems that harness spent steam and hot water to preheat incoming water. It’s energy that’s already been used and paid for, and rather than letting that energy go down the drain or out into the work area, it’s put to work again. It’s like finding money.

How effective are the systems? One of the makers figures its warewasher with waste-heat recovery is about 30% more efficient than the same washer without it.

That’s a huge advantage, and it hints at better things to come. Energy is all around us, and humanity has just barely begun to harness it. Everybody talks now about wind and solar, and those are great potentials in lots of applications. We don’t have to dig up or drill out those kinds of energy. They’re right in front of us, everywhere and every day. And then there’s water energy, which we’ve known since the earliest days of dams and before. But dams are just one way to harness the weight and movement of water—lots of other, more portable ways will surely find widespread practical applications. We have a moon moving tides. Let’s grab some of that motion.

Last month’s cover story, “Green Made Easy,” was loaded with interesting examples of what’s being done by some of the leading chains. Yum!, for example, has a store with a solar exterior wall that preheats fresh air entering the building to reduce HVAC  load during heating months. Ducting natural light is another technique that offers advantages under the right conditions. Think of the huge window-glass areas that now reflect energy away from the building. What if those surfaces weren’t rejecting that energy, but storing it or routing it?

And then we’re back to the waste heat. It’s energy already spent, and the only question is how to reapply it. Think of flue temperatures. Think of the heat going up the exhaust hood. If we’re lucky, it’s escaping outside and becomes useless. If we’re not lucky, it heats up our workspace, and then we spend more energy to cool it. Does this sound crazy?

Better to harness it, use those exhaust-hood Btus to heat the building’s water, or to recirculate to cooking processes, or even to heat that warewasher water.

We’re on the verge of a new era.

Brian Ward

Chief Editor”””