Ron Gehl - President EOS Research

Solar Thermal is Hot – Ron Gehl of EOS Research

“I think one of the most striking memories I had was of helping uncover an entire tanker truck full of chlorinated solvents that was buried in one piece.” ~ Ron Gehl, president EOS Research, Ltd.

I’ve got a great show for you today. My guest is Ron Gehl, founder and President of EOS  Research. Ron has spent thirty years tackling difficult engineering problems in environmental protection and renewable energy. He’s also Chair of the Solar Thermal Division of the American Solar Energy Society. We’re going to talk about solar thermal or solar hot water heating, the sometimes underappreciated workhorse of the renewable energy world. Ron started his career in hazardous waste remediation before discovering his passion for solar thermal applications.

Ron Gehl, President of EOS Research

RG: My name’s Ron Gehl. I’m president of a company called EOS Research and am chair of the solar thermal technical division of ASES.

DB: Alright. And where do you live and work Ron?

RG: I live in New Hampshire. Our office is in Rochester and I live in the middle of nowhere.

DB: So you don’t go into the office everyday then.

RG: I try not to but unfortunately I’ve got to spend a little more time there than I would like. I’d rather be out in the field all the time.

DB: So, solar thermal. I think a lot of people just don’t know much about solar thermal really. They think of photovoltaic panels when they think of solar.

RG: Constant struggle for those of us that are solar thermal practitioners. I’ll just point out that I’m not one of the guys who goes up on the roof and installs solar thermal systems but we kind of approach it from a control systems standpoint and from that angle have been able to see a lot of different systems being installed and what works well and how to optimize performance and all that. But from the standpoint of ASES’s solar thermal division, our work has to be focused on pointing out how much more efficient a solar thermal application is than a comparably sized photovoltaic application. So we’re always three to four times as much energy that can be generated from a solar thermal installation of the same size as a photovoltaic installation.

DB: Can you explain why that is?

RG: Well it’s basically the process of converting the sun’s photonic energy into useable energy for humans is more efficient when you can transfer infrared radiation to, typically water is the medium that we use in solar thermal, versus converting it to electrons in photovoltaic panels.

DB: So you have a whole different set of challenges with using that energy and storing it and transporting it. So give us a flow chart for what a solar thermal system is.

RG: Okay. Well you mentioned storage and that’s one of the components of a solar thermal system that is really advantageous. It’s much easier to store solar thermal energy than it is to store electricity of course. But, generally speaking what you have are a series of panels that are of different designs, they can be evacuated tubes they can be flat plates, but generally speaking they’re dark colored and they absorb infrared radiation and the idea is to transfer as much of that as possible to a fluid medium, typically water or a glycol solution, and then bring it down to the ground or to a storage tank where you can actually hold it aside for when you need it or put it to immediate use. So the applications can be as simple as domestic hot water heating. They are increasingly being used for industrial processes or things as mundane as a car wash, that’s a fantastic example of a solar thermal application that’s really beneficial, to even solar cooling applications. So through the use of absorption and adsorption chillers you can actually convert solar thermal heat to cooling that can be very beneficial particularly for larger buildings. We’re going to have a fair bit of content talking about that here at the conference.

DB: Can you try to do an audio explanation of a solar absorption chiller? That sounds like something that needs a drawing really.

RG: It really does but I’ll keep it simple and think about comparable to a refrigeration cycle if you will. Something that has been used for many years, for instance in disposing of process heat from industrial facilities through the use of an absorption chiller which is basically using chemicals that can evaporate liquids off that then can allow you to take advantage of the cooling that comes as a byproduct of that.

DB: Okay. That makes sense. What is the efficiency difference between solar thermal and solar PV?

RG: Solar Thermal can be three to four times as efficient as solar PV. The key aspect of course is being able to store that energy and use it efficiently, which is something that is frankly often ignored in a solar thermal system. Put it aside. Put it in a well-insulated container if you will and then you’ll have the beneficial use of three to four times the energy that you can get from a comparably sized photovoltaic panel.

DB: So the first big solar rush, during the Carter administration or around that time, that was mostly solar thermal for domestic hot water right?

RG: That’s right.

DB: What would you say led to the end of that period?

RG: Well ultimately it was a political change that resulted in the elimination of some of the tax credits that went along with the installation of solar thermal. But frankly the industry itself boomed so quickly back in the late 70s and 80s that there was some pretty shoddy workmanship that went out there. So that was a great detriment to the entire industry actually. But these days with solar PV booming so quickly and having immense economies of scale, particularly in the manufacturing side of things, some have erroneously claimed that there’s no need for solar thermal anymore. Well, maybe if one were looking at an individual residence it’s a little harder to look at a compelling argument that a solar thermal system makes sense depending on your circumstances. But when you really look at all of the energy use in the world that is really derived from creating heat that is where solar thermal can really bring its greatest benefit. We have essentially in excess of 50% of all the energy use in the world is for creating heat. And it makes no sense from an engineering standpoint to first turn it into electricity before you turn it back into heat. So one of the things that we’re emphasizing a lot these days and trying to encourage, and we’ll see a lot of that at this conference, is commercial, larger scale, net-zero buildings applications for solar thermal and how they fit into the larger picture of how we can get to lower carbon consumption.

DB: And every time you convert energy from one form to another you’re going to lose some along the way, right?

RG: Yep. Obviously, you have an efficiency loss there almost immediately and we like to encourage people to have well-designed systems that can store that very effectively and water is one of the most effective energy storage mechanisms there is out there, when you really think about its energy density. What you can do with just a tank of water is pretty incredible.

DB: It sounds like kind of a no-brainer for industrial solutions, especially anything that uses a lot of water. For a single family dwelling, somebody told me recently that it now made more sense to use a geothermal water heater and offset the electricity for that with PV. Would you agree with that?

RB: Yeah, the heat pump water heater has gained an awful lot of traction in the system and the thing is about heat pump water heaters is, yes the initial up front cost for an installed system can be considerably less than a solar thermal system there’s no question about it but they will not last as long and when you take a slightly longer term approach you’ll find that a solar thermal system is a much higher return on investment. We do have a challenge in that very few people think longer term and so that’s why I think it has become rather attractive to throw in a heat pump water heater, particularly if you’re just going to get rid of the house in two years, for domestic applications they may make sense. But we like to try to draw attention to return on investment. That’s really where solar thermal shines.

DB: What do you do as part of the solar thermal technical division for the American Solar Energy Society?

RG: Our primary role is to get the word out, encourage very high quality technical content to disseminate. Our biggest function, frankly, is making sure that what’s presented here at Solar 2015 and ASES’ annual conference is the highest quality that it can be and is in keeping with what the industry needs. So this year you’ll find as compared with previous years for instance, considerably stronger focus on larger scale applications. That’s really where solar thermal’s going to fit in best. We see our role as the solar thermal technical division to encourage the dissemination of the highest quality technical content that there is.

DB: Okay. Is your background in engineering?

RG: It is but not directly. I actually spent a number of years traipsing around hazardous waste sites trying to figure out how to clean them up so I have an environmental engineering background but interestingly an awful lot of the principles that we applied with the treatment systems and moving water and measuring process parameters and all that translate extremely well into solar thermal and that’s where we spend a lot of time these days doing control systems.

DB: What was your favorite hazardous waste site that you’ve ever been to?

RG: Favorite (laughs). Oh I’ve seen some pretty interesting ones I can tell you that. There’s always some good ones in New Jersey. I think one of the most striking memories I had of helping uncover an entire tanker truck full of chlorinated solvents that was buried in one piece. Rather than properly dispose of it elsewhere, they found it easier to do it that way. You run across some pretty interesting things there.

DB: I used to work for the Hazardous Waste Branch in Kentucky and we had a D.O.E. site, the Paducah Gaseous Diffusion Plant where they used to bring in tanker trucks of PCE or TCE and they started to worry about what would happen if one of them derailed in the winter so they did an experiment and they lifted one up on a crane and dropped it onto a concrete pad and either they chilled it or it was a very very cold day and sure enough it did rupture and it was a tanker full of trichloroethene. You know they could have just tried water or something for the experiment but.

RG: Right. A little mess to clean up after.

DB: Yeah, I don’t think they got it all either.

RG: Boy. That never seems to be the case.

DB: So how did you get interested in solar?

RG: Really it was a personal quest if you will. In looking at newer more sustainable energy choices for home and business that got me most interested in it and you know, frankly, I thought initially I was going to be most interested in geothermal applications, having some geological engineering background and pretty quickly it came to me that solar thermal was a much more efficient and more interesting process to work with.

DB: Well I really appreciate you spending some time with me Ron and I hope you enjoy the rest of the conference.

RG: It’s gonna be a great one.

DB: Alright. Thanks a lot.

If you’d like to find out more about Ron and his company you can go to To find out about the Solar Thermal Division of the American Solar Energy Society that Ron chairs go to and click on divisions.

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