The Future of Solar Water Heating

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By Dwell / Published by Dwell
Dwell hosts a Q&A with Mike Landau, solar water heating program manager for SoCalGas and Nurit Katz, chief sustainability officer and executive officer for facilities management at UCLA, exploring innovations in solar water heating.

Dwell: Nurit, how is UCLA leading the charge in sustainable solar water heating and reducing carbon emissions?

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The Sustainable L.A. Grand Challenge, a UCLA initiative with 150 faculty across 40 different departments, has the stated goal of bringing the L.A. region to 100% sustainability in water and energy while enhancing biodiversity by 2050.

Nurit Katz: At UCLA we have a broad sustainability program that includes a lot of goals in different areas. The one that relates most closely to solar water heating is our greenhouse gas emissions reduction goal. The UC system and UCLA have a goal of carbon neutrality by 2025, and solar water heating is part of our portfolio that helps us move toward renewable resources and away from fossil fuels. There are still a lot of people who unfortunately politicize climate change. Even if you don’t believe that climate change is the important and critical issue that it is, there are still plenty of reasons to use technologies like solar water heating. It’s really just the smart thing to do. UCLA’s first installation was 18 years ago, with 452 flat solar collector panels on residence halls. They work rain or shine, and on sunny days sometimes you don’t even need boilers. We’ve seen $3,600 annual savings in one residence hall. All of this fits into one of UCLA’s groundbreaking programs, the Sustainable L.A. Grand Challenge. This is an initiative with 150 faculty across 40 different departments coming from different disciplines to work on getting the L.A. region to 100% sustainability in water and energy while enhancing biodiversity by 2050. We essentially view the campus as a living laboratory for sustainability. We’re able to demonstrate what’s possible in the broader region.

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The UC system and UCLA have a goal of carbon neutrality by 2025, with solar water heating an important part of that goal.

Dwell: Mike, what’s the basic functionality of solar water heating?

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A typical home uses somewhere around 150-200 therms of natural gas to heat water each year. With a solar system, usage is reduced to around 100 therms a year.

Mike Landau: Solar water heating converts solar radiation to conductive heat to raise water temperature. It works with traditional water heaters. Solar water heating systems replace natural gas and electric energy normally used to heat water. It can be used with a conventional water heater. Heating water from the sun reduces your energy use, reduces your utility bill, and reduces your carbon footprint. Basic solar hot water systems can be upscaled from residential to multiunit collectors, and can even have hundreds, even thousands, of collectors. There’s a pump that circulates transfer fluid from the tank to the roof, where solar collectors absorb the sun’s thermal energy and heat the transfer liquid. The transfer liquid enters a heat exchanger, warming the water in the storage tank, and the hot water flows to a traditional water heater (it works with tankless water heaters too) that provides backup heating when the sun isn’t shining. This is an active system that circulates water via a pump. The California Solar Initiative is represented by four entities: SoCalGas, Southern California Edison, the Center for Sustainable Energy, and PG&E, and it allows for rebates for homes and businesses.

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Solar water heating converts solar radiation to conductive heat to raise water temperature. A pump circulates transfer fluid from the tank to the roof, where solar collectors absorb the sun’s thermal energy and heat the transfer liquid. The transfer liquid enters a heat exchanger, warming the water in the storage tank, and the hot water flows to a traditional or tankless water heater that provides backup heating when the sun isn’t shining.

Dwell: The economics of solar water heating are so much easier to quantify than the environmental benefits; give us an illustration of the sustainable benefits.

Mike Landau: The benefits of using solar hot water heating include using less natural gas to heat your water. Your typical home on an annual basis uses somewhere around 150-200 therms a year. With a solar system, you’d save over half of that, around 100 therms a year. With a commercial application, it’s a multiple effect, say thousands of therms in energy use by using solar hot water technology.

Dwell: Nurit, you’ve been tasked at UCLA with going carbon neutral by 2025. For a community with such diverse needs as UCLA, how can solar water heating be adapted to such a diverse population?

Nurit Katz: In our case, we have high-rise residential, which isn’t so different from a large apartment complex or a hotel or other buildings, so solar water heating was a pretty good fit.  It’s not a technology that’s necessarily dependent on the type of buildings so it can go for a house or a large commercial scale. I think it’s pretty adaptable in that way. I actually first learned about solar water heating not from UCLA but from my grandparents, who installed it I think in the ’80s, so I grew up swimming in their pool, which was solar water heated, so it wasn’t difficult adapting with a diverse and large population like ours.

Dwell: When UCLA installed its first solar panels 20 years ago, it was not a technology that was widely adopted. So what’s the role of civic policy makers to be leaders on this?

Nurit Katz: I really see universities as having a responsibility, particularly a public university like UCLA—we are custodians of state resources—it’s our responsibility to be on the leading edge of efficient and responsible stewardship. So we’ve been championing energy efficiency for a long time, long before sustainability was in the public sphere or awareness; now we have researchers at UCLA that are developing thin-film solar for example, or smart EV charging. So we get to pilot that stuff on campus and demonstrate that it works in hopes that it will be more broadly adapted throughout the city.

Dwell: Mike, the pubic approaches new green technology with open skepticism sometimes, what are some misconceptions about solar water heating and its effectiveness and reliability?

Mike Landau: I think people assume that this is a new technology, but solar water heating has been around for centuries, if not thousands of years. You can run a hose from on top of your house and just heat your pool water now. The technology’s been around for decades, but it has improved over time. It has become more efficient and reliable—components and electronics are more reliable. People are assuming there’s a reliability issue here, when there isn’t. Everything that’s installed has a 10-year warranty on it for the most part, so it’s very reliable technology, and you have very experienced contractors in the area right now.

Nurit Katz: There’s a quote that I share with my students in the sustainability certificate program. I’m paraphrasing, but it’s "I’d put my money on the sun and solar energy. What a source of power! I hope we don’t have to wait until oil and coal run out before we tackle that." Every year I ask the students, Who do you think said that? And they’ll say Obama or Gore. It turns out it’s actually a quote from Thomas Edison in 1931. So the idea that the sun is a good source of energy is not a new one, and unfortunately we’re still not at widespread adoption. I think it’s not a technological challenge but really a behavioral and cultural challenge, so when you ask about myths and misconceptions, one of the biggest ones is that people have this perception that it’s always business versus environment; that going green has to cost more. And I think the message that we’re really trying to demonstrate is it doesn’t. There’s a lot of synergy in places where you can save green by going green and I think the more we can get that awareness out there, the faster we can adopt this technology, as Mike pointed out, that has been around for ages.

Dwell: Southern California is the ideal environment for solar. What are the applications and abilities in less sunny climates?

Mike Landau: In less sunny climates, there’s still that solar radiation on clear days. It doesn’t necessarily have to be a hot day to be able to absorb the sun’s radiation. As long as it’s clear there’s still the possibility of getting some solar energy out of that. There is backup: Most solar systems, almost all of them, are installed with some sort of backup. Whether it’s a boiler or a water heater or whatever is used in some of these colder climates, probably six months out of the year you can still get some decent solar energy to heat your water. It shouldn’t be limited by colder temperatures. There’s even hybrid collectors that provide hot water and electricity at the same time. So you have that kind of hybrid technology in the marketplace. The applications are almost limitless in terms of how we can use solar hot water technology.