Ben Schoenbauer recently attended the 5th annual ACEEE Hot Water Forum, held in Berkeley, CA May 21-23. I caught up with him after his return, and asked him some questions about the latest and greatest ideas on display for saving energy in water heating.
Jenny: So what is the ACEEE Hot Water Forum?
Ben: It started with the realization that water heating is an increasing part of our energy load. There were experts around the country who were dealing with issues individually, and ACEEE created a forum for them all to share their work.
Jenny: How long have you been going?
Ben: It started five years ago, and I think I’ve been to every one. It was the first conference I went to at CEE.
Jenny: Why is water heating a big deal?
Ben: As the residential housing stock becomes tighter and better insulated, space heating demand has gone down. That means water is a bigger and bigger share of our energy use, and catching up to space heating in cold climates. It is also our biggest peak load, because of when we draw that hot water. And there is a lot of potential for improvement: traditionally water heaters have 50% efficiency, and the units we’re installing now have about 90% efficiency.
Jenny: Why does it matter that water heating is the biggest peak load?
Ben: It determines sizing for a lot of things. You need a water heater that can supply 100,000 btus per hour for a shower. But your furnace can just be a 40,000 btu per hour unit.
Jenny: What were some of the biggest topics at this year’s forum?
Ben: Things seemed to break down into two paths.
One is the direction that the whole field of energy efficiency has been going in, which is the systems approach: looking at the house instead of just the water heater. There were a lot of presentations on things like the distribution systems, piping, how low flow fixtures effect everything, how different water usage in a house affects everything.
And then there are the new technologies. This year I saw a fair amount about electric heat pump water heaters, which are coming back to some extent. Questions remain if they work as well as manufacturers say they do, and how they work in cold climates. There is also often a focus on solar, and this year I heard some discussion on why there is a market in Europe and not here.
Jenny: What types of behavioral efficiency measures were talked about?
Ben: On the residential side, some new products are attempting to induce change in people’s behavior. There are touch faucets, or on-demand recirculation, where you push a button to get hot water rather than just opening the fixture and letting the water go down the drain. It works really well in a situation where you have a kitchen or a bathroom that’s way far away from your hot water heater.
They work with either an occupancy sensor or a button. So it just pulls hot water out of the pipe and circulates it back through the cold water side. And when it senses that there’s hot water demand at the sink, it’ll put hot water into the fixture. It has some energy savings but mainly is a water saving device, because you’re not putting all that water down the drain.
Jenny: That’s really interesting. What are some of the biggest issues in commercial water heating?
Ben: The majority of the forum is residential, but there were a couple of sessions on commercial kitchens. PG&E has a food service laboratory that had a couple of presentations and then a tour. That’s where a lot of the work has been done thus far, and there are a lot of kitchens that use really old technology that just isn’t efficient. They have dishwashers that are just on, using hot water the entire time the restaurant is open. That can mean thousands and thousands of gallons, and only a percentage of that is actual active use.
Then there are some new technologies that were focused on heat recovery. Heat recovery can make a lot of sense for commercial applications where you reclaim heat out of the waste stream, because you have a more continuous hot water output than you do in a house.
Jenny: What were some of the new things you saw presented that you hadn’t heard about before?
Ben: There are new methods to do thermal storage, where you have a really big tank and you heat it off-peak. There are some technologies that are trying to integrate that into the grid, to help the grid react better with renewables. So if you have a big gust of wind, it reads that the grid has too much energy coming onto it, and it increases everyone’s tank temperatures to store that extra energy instead of it having to go to waste. Obviously, you have to have a large-scale implementation before the grid can actually do anything with it. If there’s 10 out there you can’t store much energy, but if there’s 100,000 you can actually store some energy.
There are gas water heaters with a smart thermostat that it knows you’re not going to use water in the middle of the night so it doesn’t keep it hot. Which is a really great technology. The problem is that the current standard for how they rate water heaters doesn’t take any of those smart controls into account. You basically have to disable all the controls before you do the test, so there’s no benefit to the manufacturers for any of that stuff. And the other problem is, especially with natural gas water heating, it’s so cheap. I mean, you spend like $12 a month to heat your water. It’s a couple hundred dollars a year at most, so even if you can cut that use in half, you still only have a couple thousand dollars incremental cost if you’re going to have any realistic payback.
Jenny: What do you think the big opportunities for our research at CEE?
Ben: From a research standpoint, something like the tankless hot water study is a good example of what we do here. There still aren't many people doing research in this area. The ability to test new technologies in the field and have real world data is a real need in this industry. The tankless study also helped us understand how people use water. I think of the 150 or so houses in the US where ongoing water use has been monitored, 10 were through our study.
Jenny: Thanks for your time today, Ben.
Related Innovation Exchange projects:
Retrofitting Integrated Space & Water Heating Systems
Actual Savings and Performance of Natural Gas Tankless Water Heaters
DIA Lab Field Trip