Above the earth’s surface, temperatures change with each passing season. Below-surface temperatures remain consistent and can be captured with geothermal systems. An idea has emerged that, using existing water mains, could empower more communities to take advantage of the “earth heat” trapped below.
In this episode of the Local Energy Rules Podcast, host John Farrell speaks with Jay Egg, a geothermal expert, about the potential of minimizing the carbon footprint of heating and cooling buildings by adapting water mains to capture the heat just below the Earth’s surface. They discuss successful geothermal projects in Canada and the triumphs and challenges of projects in the U.S.
Listen to the full episode and explore more resources below — including a transcript and summary of the conversation.
|Jay Egg:||The client is now paying $20, $30, $40 a month for the privilege of using BTU exchange with the water main. And everybody’s happy that water companies doubling their money cause most water bills aren’t that large. Anyway, they’re $20, $30, $40 a month. And so now they’re doubling their money and they haven’t had to add any major infrastructure. That’s the 4.0 answer. And that’s essentially the best way I see to do this.|
|John Farrell:||The low carbon secret to building heating and cooling may be under our streets. Geothermal energy literally means earth heat, and it taps the near constant temperature of the ground several feet deep to heat or cool a building. Think of it like a refrigerator for your whole house, keeping your home cool in the summer by pushing hot air outside or keeping your home warm in the winter. By pushing cold air out by tapping near constant temperatures underground geothermal energy systems can provide this benefit using much less energy than gas furnaces or boilers. And they work for heating and cooling. Geothermal has had one drawback, however: it typically involves drilling deep holes to access these constant temperatures underground. But what if it could tap an existing source under our streets? Jay Egg, a geothermal consultant, writer, author, and educator joined me in July 2020 to explain how we could tap city water means as a heating or cooling source for geothermal systems, allowing homes and businesses to lower energy costs, carbon emissions, and to increase revenue for city water utilities. I’m John Farrell, director of the energy democracy initiative at the Institute for Local Self-Reliance. And this is Local Energy Rules, a podcast sharing powerful stories about local, renewable energy. Jay, welcome to Local Energy Rules.|
|Jay Egg:||Well thank you for inviting me, John. I’m glad to be here.|
|John Farrell:||We came across your name as we were looking into investigating this notion of using city water mains as a heat source and source of energy for geothermal systems in part, because there was a fascinating project that took place in New York doing this, using a water main, and you recently worked with the city of Oneonta, New York on setting up a water main geothermal project for a local hospital. Could you give us some background on what the city was hoping to do with the geothermal system that’s connected to the water main?|
|Jay Egg:||I certainly can. And I wondered, do you have a good idea about the school that was put onto a water main in New York in 2016? Would that be a good backstory in a few words?|
|John Farrell:||Please, do give that backstory.|
|Jay Egg:||I think it really, when we talk about the Valley Stream school, the school in Valley Stream, New York that went onto a water main, it kind of leads into this. What happened is in 2015: this school whose water utility was named American Water got together with the New York Department of Regulation. It’s the regulator for the utilities. And I don’t know if I said that particular acronym right. But I got together with them and they decided that they wanted to do this water main source system that would heat and cool this 40,000 square foot school simply by putting in the geothermal heat pumps and using the water main as exchange for the heat pumps to heat and cool.|
And the way they did that is they develop the plans and they cut into the water main and they ran the water main through it and exchanger and threw some pumps in an exchanger double-walled titanium exchanger. They put it in a separate building and then they had a, a completely detached loop called the condenser water loop that ran through and provided heat and removed heat from the building, depending on the mode it was in, to provide all of the heating and cooling for this school. And this was a brilliant landmark project that had a lot of promise and it was actually funded for testing by Oak Ridge National Laboratories who completed their test in 2018. The test is available online to anybody. The executive summary said that they found there was no reaction or situation with regard to the potable water coming out of the exchanger that would indicate any problems with doing potable water exchange on any other systems. So, it was a remarkable 50-page report. Many of the folks in New York in clean, heating and cooling were excited by it. And they were looking at the potential for potable water exchange to start picking up in other public buildings and municipalities throughout New York. After this report came out in 2019, and that kind of brings us up to Oneonta.
|John Farrell:||Let me jump in really quick, just for folks to understand why there’s excitement about this, which is when you normally do a geothermal project, you’re digging a big hole and you’re laying a whole bunch of loops of heat transfer fluid—like antifreeze in these—in these loops underground and all that digging is expensive. You’re either digging a really deep hole or you’re digging a really wide field to do all these loops. And the idea of using a water main is you already have this thing that’s underground, that’s at the right temperature. And so you don’t have to do all that extra digging, right?|
|Jay Egg:||That’s exactly right. And that’s part of what you said very well. My emphasis or my focus is not to do the basic, but to use some of the fluid that’s part of what I term the water-energy nexus to use fluid, that’s already moving beside or in the vicinity of a building and use it for dual purposes because it’s not something that has not been done before this a matter of fact, and I really didn’t want to get into this, but I should mention just right now, cause it’s a perfect time. In Toronto, our neighbors, just to the north in New York, the city of Toronto has three main lines that go in there. Don’t want to say they’re about 48 inches. They go down into Lake Ontario and they pull in their water from the Lake and treat it for drinking to become drinking water for the city of Toronto.|
And the interesting thing about this is 15 years ago, they put in a bank of exchangers and they run that drinking water. After it’s been treated through the exchangers, which preaches the water for all of the downtown buildings, 72,000 tons of exchange capacity that provides all the air conditioning for downtown. So that’s using potable water. That’s already been treated. After it’s been treated, they run it through the exchangers. Then they send it on out to Ontarians to Toronto enhanced for their potable drinking water. So it’s, it’s been operating 15 years and it’s been operating so well. They’re actually tripling the size of that system too. So, it’s not new. It’s just that if we’re having a little trouble getting folks to come together on that, and that’s why we were so excited when this happened in Valley Stream.
|John Farrell:||This is super helpful, I think because we have—and we’re going to get to this a little bit later—a lot of cities around the United States that are really focused on how do we decarbonize our energy system? How do we do a low carbon heating and cooling? Geothermal is sort of down the list right now of things that people are thinking about, but it’s usually because of this issue of having to dig big holes. And so, it’s fascinating to me that we not only have a recent example with this school, but we have an example started 15, 20 years ago and has already been doing this for a while for the exact purpose we’re talking about. So, let’s get back now finally to the place where you’ve been working in Oneonta about doing this water main geothermal project.|
|Jay Egg:||Wonderful. So first of all I did in Otsego, I think it’s called Otsego County there. Oneonta is one of the cities, Cooperstown where the baseball hall of fame is one of the cities around there. And all these little towns and villages are all kind of together as part of this Otsego chamber of commerce and where it really started was late in 2018. I think it was sometime mid-2018. I do a lot of speaking events and I was the keynote speaker for a clean energy thing going on there. Otsego was at this conference where there were a lot of mayors, there were a lot of city managers, there were a lot of dignitaries from the local area there. And I did a presentation on geothermal and one of the things that I shared was a lot of the great things going on in New York, one of the things I shared was this great story with this Valley Stream school that tied into a water main and the executives or the chief management officials with NYSERDA, which is the New York State Energy, Research and Development Authority.|
And that is the arm of New York that funds projects like this like municipal projects that are doing good things for energy and reducing emissions. They were there because they have a clean heating and cooling division and they were very interested in what’s going on with the potential for using water mains or potable water to heat and cool buildings. As I talked about it, it became a great subject of interest.
So, lo and behold, before too long, I get a call from Oneonta, Greg Mattice is the city engineer and George Korthauer, who was another city engineer, all got together with me and some of the folks from NYSERDA and said, “we are replacing a water main running down through Main Street in our town where we’ve already contracted to do it. Do you think there is a way that we could use this since we’re opening up the street, this water main to help install a geothermal capacity for the buildings along Main Street?”
Everybody agreed that that was a great idea to investigate that. So they hired us, they put us under contract with the city of Oneonta. And, you mentioned you’ve seen the headline on that. We went under contract and began this study where we ran into a problem was everything was fine until it got to the New York Department of Health. They have some clause— and I wrote this actually in an article —and plumbing engineer, let’s see the DOH pushes back. The New York Department of Health has a regulation that was shared by Roger. Sokal the Director of the New York Division of Environmental Health Protection in May 2019 that prohibits the introduction of potable water after heat exchange. It’s this obscure rule. And I say, it’s obscure, I’m sure there’s a reason for it. I’m sure somebody did something wrong sometime in the last several decades that that made that rule come into being.
But nonetheless, it says it, he states that a direct cross connection is a direct contradiction to what they call—and this is an actual thing— “The 10 State Standards” and contradicts the U.S. Environmental Protection Agency’s guidance in document WSG one 17. It went on to say that Jeffrey Snyder director of Environmental Health and Madison County Department of Health notes, that part 8.10.2 of the “10 State Standard” does not allow water use in conjunction with heat exchangers to be returned to the public water system. And that’s when I say a little bit tongue in cheek in my article said, perhaps somebody should tell that to Toronto since they’re doing it.
And they’ve been doing it for 15 years, very effectively. So what that comes down to what that argument comes down to John is they’re saying they will not allow potable water to be exchanged with the refrigeration system and continue to be potable. In other words, it has to be thrown away. I pushed back a little bit and I haven’t gotten an answer to this yet, but I said, let’s talk about a drinking fountain on the wall that goes through refrigeration, and you allow people to drink from it. Let’s talk about a domestic hot water tank that uses it’s a heat recovery tank that has the compressor on the top. They’re selling by the thousands. Now that uses a compressor and exchanger to heat that water. You want to go even larger. You let’s talk about ice machines, potable that’s potable, solid water ice machines go through a refrigeration process and we’re allowed to drink it.
So there are potable water refrigeration systems. There are thousands of systems that have been rated by NSF. What they really need to do is look at the specifics of what happened, because probably if I had to guess what happened that created this rule that prohibits the introduction of potable water after heat exchange is probably where somebody did it in their backyard. I’m not suggesting and nor is anybody else suggesting that people are allowed to take potable water necessarily into their home, do their exchange and bring it back. No, what we’re wanting to do is let the potable water authority do their heat exchange. Blend in line was done at Valley Stream. There was a separate exchange or building that exchange. And it’s a controlled by the water department. It’s a completely controlled process. They use the water, they exchange it and they send it back into the water main. That’s exactly what Toronto does. This is what we were trying to do in the Oneonta situation.
|John Farrell:||I just want you to clarify too, for folks on this, because what I find so fascinating about it is maybe something that people, when you, you mentioned the word exchanger, like I can picture what a heat exchanger is for other folks. Just think about a refrigerator, right? So we’re talking about the stuff on the back of your refrigerator that runs through those coils is never in your refrigerator. It’s never getting in, mixed in with your food. And the same thing is true of these systems. The water is never leaving the pipe, the water main pipe to be tampered with. You’re literally just wrapping a piece of metal around it to extract the heat from it. This regulation has nothing to do with how people might be sticking their fingers in the water. They’re never touching it. It has to do with, as you’re saying, with kind of who manages that heat exchanged on, on whose property it’s happening and some of these other issues. And I guess there’s another issue too, that is mentioned, that was researched in that study you mentioned about heat and how that might impact the water, but we’re not talking about anybody, contaminating water supply by running it out into a cup and pouring it back in. And now it’s going to someone else’s house.|
|Jay Egg:||Right? And that is what is so important to understand. It’s not being tampered with, by anyone and every situation, including Toronto and including Valley Stream. This is a Water Department controlled exchange process. And as a matter of fact, if they would open their minds, and this is the hardest thing to do for authorities having jurisdiction, it takes a lot of work to do this. It takes a lot of work to actually open your mind, to get a process going. But these are the things that change the world when people will step up and do it. When I say it takes a lot of work, they have to understand when I say a lot of work, it’s not the engineering. They just have to understand it and have a competent new verbiage, put into their codes to show how it’s done. In this case, we would borrow verbiage from what they did at Valley Stream, or we would borrow verbiage from what they did in Toronto or any number of other places.|
As a matter of fact, I was so impressed to see that when I first met you, I had talked to your assistant Lilli Ambort, and she had sent me something I didn’t even know anything about. The Energy Policy Act of 1992, Public Law, 102-486, October 24th says on geothermal heat pumps. It says encouraged States, municipalities counties, and townships to consider allowing the installation of geothermal heat pumps to permit public and private water recipients to utilize the flow of water from and back into public and private water mains for the purpose of providing sufficient water supply for operation of residential geothermal heat pumps. That is the perfect 4.0 solution. But I understand where water departments might not want that to happen inside the space. They would want to control it outside, but that’s a perfect law that in my opinion, and could be very effectively used if they just use an NSF approved appliance that does this exchange, because then they can certify there’s nothing happening to it. But again, the projects that I’ve seen approved in a large scale involve water company, managed facilities, and the water company ends up selling. They not only sell the water, but they also sell the BTUs from the water when it does the heating and cooling. So they have two income streams then, and they’re doing a benefit to the clients.
|John Farrell:||We’re going to take a short break. When we come back, I asked Jay whether water main geothermal would work for homes and how the city’s water utility would play a role. We also explore what he calls the water energy nexus, discussing other ways that we can capture the energy and water systems from gray water to wastewater, to power our economy. Hey, thanks for listening to Local Energy Rules.|
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We’ve spent a few minutes now talking about this particular project that barrier you ran into at the health department and kind of how it works. And the rationale for this, like this is worth investigating, of course, because it makes geothermal cheaper to do, you’ve got this ready resource that’s already flowing instead of having to make your own loop field and bore big holes in the ground. We have cities, there’s over a hundred cities now in the United States that have made commitments on some timeline to 100% renewable energy. Sometimes it’s just electricity, but most of the time, it’s all energy sources. So they’re thinking about building heating and cooling.
And right now we’ve got, especially in the Northern part of the country, most homes are being heated with natural gas, which is relatively inexpensive because we don’t count pollution impacts and the price that we pay for it obviously. And so it’s hard to find stuff to replace it that is affordable. And this seems to me to be a perfect candidate, not only because you have a technology that would allow people to lower their carbon emissions and do it affordably, but because most cities own their own water department already and where they can’t regulate the gas utility. In fact, there are big political fights around this, right now, they do own a water department. And gosh, darn it, cities probably need some money too. And like you just said, they have an opportunity to make money selling heat energy if they ran this kind of system. So let’s just talk a little bit about what would be involved in a city doing this kind of system. Let’s just say they wanted to start with a pilot, a few blocks of residential property. Can they just use the water main that’s there? Do they have to do it with a water main upgrade? How would a city get started on this?
|Jay Egg:||What they would do—And this is a model that we’ve looked at, you know, how each home or each apartment has a water meter out front, it’s usually in a concrete box or something like that. That box would, if would be a perfect place because that’s owned by the water department, it’d be a perfect place for one of these exchanges to be put in that would be owned by the water company. And so it would be an upgrade. It would be something perfectly engineered and it would have the capacity to exchange with the water main, all of the heating and cooling needs for the geothermal heat pump in the building. What would change with the building is they would still have their water main coming in their water line coming in, but then two other lines would be added off of this exchanger. And they’d just be trenched up to the building and stubbed in significantly less than the 15,000 or $20,000 investment that’s needed for ground loops. This would probably be somewhere in the neighborhood or one or $2,000 investment for the water company, which they wouldn’t even need to charge for, because now they’re selling BTUs to the client. The client is now paying 20, 30, $40 a month for the privilege of using BTU exchange with the water main. And everybody’s happy that water companies doubling their money cause most water bills aren’t that large. Anyway, they’re 20, 30, $40 a month. And, and so now they’re doubling their money and they haven’t had to add any major infrastructure. That’s the 4.0 answer. And that’s essentially the way, the best way I see to do this.|
|John Farrell:||Let me just give you an example. And I stuck with this, of course, cause I have a house in Minneapolis. So my water meter that measures how much I use is actually inside my house. But I know there’s also a shut off valve in the sidewalk, right? Between my house in the street. So where in that, could they put it in my house? Would they put it under the street? Like where would they put that exchanger?|
|Jay Egg:||If they knew they could always get into your house to deal with any emergencies? I would say, put it in your house. But knowing the authorities, having jurisdiction that I’ve dealt with, they would probably want to put a concrete box in the ground right there that had the exchanger in it right in line with the water coming into your house. And they would put the exchanger there and that would have the BTU meter or the GPM meter for what you’re doing for your heat pump. So they would have to put something big enough to hold an exchanger that can exchange the number of beats you use in your house, which is not going to be that big. A typical exchanger might be the size of a, I wish I had a picture to show you right now, but there might be 12 to 14 inches high and 12 to 14 inches wide and about eight to 10 inches thick. So this is what one of these exchanges looks like. And they have the water main pipes coming in one side and then they would have the in and out pipes from the geothermal coming out the other side. And it would just be in a simple vault. And if this were a video or a visual, I could show you what one looks like, but that’s what they would do at each house in the simplest of forms, then that would work in your house.|
|John Farrell:||And then tell me about what the customer would need to do. So let’s just say the water utility, they get on board with this, they’re offering to do this installation for customers, customers. Now I’ve got a heat exchanger, whether it’s in the street or in their house, they’ve got, they’ve got access to BTUs now that they can supply their house just like they would come in through the gas line. For example, just in a different form. What equipment does the customer need to take advantage?|
|Jay Egg:||If you imagine what a forced-air furnace looks like, which a lot of people have that use natural gas, they would exchange that furnace for a geothermal heat pump, which normally fits in the same footprint of a forced-air furnace, that geothermal heat pump. They use it electricity, just like a forced-air furnace to drive the fan and the compressor. So they would put it in place, hook up the electrical service. And then the pipes for that would normally go to a ground loop would now tie into that exchanger. And a small circulator would be put in a micro horsepower circulator just to circulate the water between the heat pump and the exchanger with the water main. So that would be all it would be needed in the house, no drilling, no loop fields outside, just tying into the, the pipes that have been run in or are available from the water company now.|
|John Farrell:||And you’re, if you’re talking about a house that has central air conditioning too, you can actually replace both with this system, right? It’s going to heat and cool.|
|Jay Egg:||Yes, absolutely. If you, if you are familiar with this, many of the forced air furnaces have an air conditioning coil in them, if they have air conditioning too, it’s a combination unit. That unit, it can be completely replaced with a geothermal heat pump, cause it does both heating and cooling. And in addition to that, and they have the domestic hot water generator option that can provide a good portion of the hot water needed in a home.|
|John Farrell:||We’ve talked a lot about what the city would need to do for this. Are there any kinds of engineering or other challenges? So we, when we talked about the health department issue in New York, their concern was I think, largely around just they had this regulation. And as you mentioned, it might’ve had something to do with someone messing with it on their own private property. Before now everything’s being controlled by the water utility. It’s all kind of locked up in and away from the customer’s hands. The only other concern that I have read anything about is this issue of every time a customer tapping into the water main draws out a little bit of heat. The water that gets sent back is a little bit colder, obviously. Cause, and so I guess my question is if you’re the 20th house in a row on that water main that wants to do this, is the water still have enough heat in it for you to take? Are you ever gonna freeze the water and the water main? And is that the only other kind of issue that we would need to confront?|
|Jay Egg:||There is definitely a master engineering concern here. The primary part of this that is the most important is figuring out what is an improved way for water utilities nationally, to do this. And we just talked about some of those opportunities and it’s very easy to do. It just gets approved by UL. It gets approved by NSF and it’s an appliance, it’s a package that becomes the exchanger that gets installed. So the next question you just mentioned is an infrastructure question. Is there enough water going through there to handle the heating and cooling load that isn’t overwhelming? Yes. In most situations, the amount of water used per household per day is usually far more than enough. Isn’t moving at the right time. Is there a possibility when everybody’s got it on and freezing? It certainly there is. And that’s something that each jurisdiction would have hire an engineering engineering firm like mine or somebody else that does master plan engineering.|
And they would look at the consumption for that city or that, uh, or that township. And they would look at the potential BTU exchange and find those thresholds where there’s going to be problems. And rather than saying, this won’t work because there’s not enough water flow. What happens in many of these situations, cause we’ve already modeled them is if you don’t have enough water flow going by, you put pumps in and you turn and you close the, the ends of the lines and you start circulating them in a circuit where it keeps the water moving at a, at a great enough rate so that they can, it can be used for geothermal exchange or heat exchange. So that’s not the case in nearly all of the situations, but in the most extreme and dense of situations that may need to happen. And there haven’t been extensive studies done on that because there hasn’t been a real, uh, there has not been a real effort to make this possible or plausible for the individual municipalities. The answer is it’s absolutely doable. We just have to look at each one individually. And the most that’s going to happen is they’re going to have to modify some of the piping to get, to keep flow continually going through the water mains. And that will be more than compensated for, by the amount of energy they’ll be selling to the customers. They’ll probably be doubling their income just because they’re selling BTUs now and doing a great service to the industry.
|John Farrell:||Yeah. I had a question for you about kind of the economic and environmental benefits. I think we’ve covered these pretty well. I just want to rattle off a summary here and then see if he has anything that I’ve missed, but we’re talking about, you know, we’re going from a fossil fueled system that provides the BTUs to now. We’re just getting the BTUs from a benign source from the water main, you’re probably cost competitive with natural gas, given that you’re just to pay for energy through this heat exchanger and not an actual fuel, you have to burn for the customer that you’ve got a water utility that can actually make money now competing with the gas company or whoever else is selling energy for this. You’re are going to use some more electricity to operate your heat pump then than you did, like when you’re burning gas for a guest furnace, but you don’t need, you know, relative to how much you need energy use. You need to do for natural gas. For example, you actually do burn and consume all of that fuel. Plus you need electricity to push it around the house in your forced air furnace example here, you’re really only using the electric energy to run the exchanger and then, and to push the air through the house. Did I get all of that pretty close?|
|Jay Egg:||You did. You did. And it’s just to bring it home and electric heat pump is exactly that it’s no different really than a water pump. If you think about a water pump, it’s, it’s a device that’s used to pump water from one place to another and a heat pump is exactly that. So it’s an electrically driven device that is used to extract heat out of fluid streams. And so that’s what it does in this case. This heat pump is extracting heat from the water main in the summertime. It’s rejecting heat into the water main. So there’s a little give and take and that’s all it’s doing is exchanging heat. Kind of like if you take your hand and hold it against a soda, your hand gets cold. Your hand did not become a soda. You didn’t get any soda on your hand, you just exchanged heat with it, right?|
And so that’s exactly it. As far as the economics of it, the natural gas is a consumable. They have to bring in more natural gas. The more that is burned. And then of course, it’s got the CO2 emissions. This is not a consumable. This is something that is completely renewable. It’s just BTUs in and BTUs out of a commodity we’re already using which doesn’t affect anything adversely. And the cost for the natural gas furnace is about the same as what it costs to pay the electricity, to run a heat pump, to heat a building. The fact of the matter is you can’t use natural gas to cool the building. So you’ve got the air conditioner. Now the air conditioning function to do that. And if you compare the cost of a standard air conditioner to a geothermal sourced air conditioner, it’s far less, it’s about 60% of what an air source air conditioner charges.
|John Farrell:||I wanted to at least ask you one question about something you talk about in your writing, what you call the water energy nexus, which discusses the overlap between water and energy use. And it seems like this is a perfect illustration of how maybe people haven’t thought about that before. One of the I’ve heard of this before in the context of we use a lot of energy to pump water. So whether it’s for agriculture and irrigation or just pumping water for homes out of aquifers or for wells, but tell me a little bit more about like how you see this intersection of water and energy and how this is playing a role in that.|
|Jay Egg:||I want to start with the very simplest overview water and energy are coupled because water is the best fluid on earth—including every other chemical combination—it’s the best fluid on earth to effectively move BTUs. A hydronic system, which is a system of pipes that have water in them, move energy around a building more effectively in the form of BTUs than, than refrigerant or any other or duct work or anything. So right away, we understand that water moves be to used very effectively when we’re talking about the water energy nexus, the first and most obvious thing is if you have a structure next to a river, that river is part of the water energy nexus. All you have to do is put your devices, your air conditioning exchangers, to exchange heat with that. And then we’ll provide all the heating and cooling you need. As a matter of fact, the UK did a study that surface water in the United Kingdom would handle all of the needs for heating and cooling for for 80% of their population 100% of the time, just because of proximity and the amount of water.|
Now, beyond that, we just talked about the city water mains and the potential. If the water’s moving anyway, once again, you have a BTU stream where it really doesn’t matter. You might as well use it for removing BTUs or adding BTS to homes. When you get into big cities and other applications in New York, for example, they are constantly, de-watering the subways. There are millions of gallons per minute of water being pumped out of subways and down the streets and into the East river and into the Hudson river, that water. And it’s just something we’re working on right now with New York city. And the MTA can be run through buildings and colleges and so forth and provide all their heating and cooling exchange needs for the entire building for the chillers.
And you keep going along on this again, I live in Florida, we have sprinklers going all the time. Those sprinklers are part of what we call the gray water system. We have actually two pipelines running down our street that have semis potable water. One is gray water it’s only used for, and that’s water. That’s gone through the waste treatment that water could be used for exchange. Another thing that’s part of the water energy nexus is it’s been proven that wastewater in the U.S.—wastewater that goes down the drain includes 350 billion kilowatt hours a year of energy we’ve paid the heat. Think about all the showers we take. Think about all the dishes we wash, the laundry we do. All of that is energy. We paid the heat and all we need to do is extract the heat from it. And it sounds like a gross thing, but it’s a huge energy recovery. A segment of the industry now, because a company called wastewater energy systems out of Vancouver has gone public.
And they’re doing city-based systems that provide all the heat needed for entire cities, just off of their wastewater plants. And they actually created a device that hooks up to an apartment building and it strips the heat out of all the wastewater before it goes into the main sewer pipes and can provide all of the domestic hot water needs for an entire apartment complex. Just off of that waste heat. I could go on and on about this, but this water energy nexus is just about—and if I were to show you a picture of under a street, you would see gray water, wastewater, stormwater, potable water—that goes to anything that’s fluid is moving by has the potential to exchange heat with the buildings and stop wasting these resources we have right in front of us.
|John Farrell:||Let me ask you one question about the wastewater, cause that’s fascinating to me, if we’re talking about a water utility building, installing an appliance in my home to tap for heat, is there an opportunity to have an appliance that taps both of those resources or would it be sort of silly because one’s cold and one’s warm?|
|Jay Egg:||Yeah, no, it would probably in the perfect world. There are a lot of things that we, we can see above right now that we go, wow, that’s going to take a lot of engineering. And, but in the perfect world, the more perfect world we’re coming into these types of things become easily engineered and they become just an appliance. It’s just a heat recovery appliance that strips the water out of the heat, out of your water, coming in the house, strips the heat out of the water, going out of the house. It could be one, one device. And then, and all it happens is the contractors that install your home, know that they have this energy recovery device that’s required by code now. And it provides all of the waste heat that you need for it to operate your heat pump. That’s the perfect answer. If a, if a device has made that can strip it all out, then you become a more energy conscious home because you’re not wasting heat coming in or out of your home.|
|John Farrell:||Jay, I just want to thank you so much for taking the time to talk with me about all of this. It’s been great! Before I let you go, what should cities, if they want to learn more about doing geothermal on the water main?|
|Jay Egg:||They should study what they’ve done in Toronto. They can Google “Egg Geo” and I’ll tell them anything about it. But if they just want to read an article, I just did this because of my whole situation I ran into with New York. And I wrote an article,|
“Potable Water-Thermal Exchange is Opening Opportunities”. That’s where I wrote about what they’re doing in Toronto, what they did in Valley Stream and the, and the dead end I ran into temporarily with the New York department of how health I was very kind. Didn’t put, throw anybody under the bus, but I said, this is what we can do. This is what we have to get past. And it’s got everything in there that I think an entry level person would want to see. They can see how it’s done and where some of the stop gaps are right now that we can, we need to get past.
|John Farrell:||Great. Well, we’ll have a link to that article in our show notes, Jay. Thanks again, really appreciate your time.|
|Jay Egg:||Thank you so much, John. This has been such a pleasure.|
|John Farrell:||This is John Farrell, director of ILSR’s Energy Democracy Initiative. I was speaking with Jay Egg, a geothermal consultant writer, author, and educator about the opportunity to tap city water mains, to deliver low carbon and low-cost heating and cooling to homes and businesses. You can get an overview of water, main geothermal and an article by Jay called “Potable Water-Thermal Exchange is Opening Opportunities” linked on our show page. You can also find more information on the ILSR website, where we explain the concept and share the story of Toronto discussed in the interview. While you’re at our website, reviewing this and other resources, you can also find more than 100 past episodes of the Local Energy Rules podcast. Until next time, keep your energy local and thanks for listening.|
The Water Energy Nexus
Jay Egg is an author, educator, geothermal consultant for the Department of Energy, and owner of his own firm, Egg Geothermal. Egg Geothermal publishes essays on the power of geothermal energy, provides a landing page for geothermal projects nationwide, and showcases books that Egg wrote.
At the start of the interview, Egg discusses a case study conducted at a Valley Stream, New York elementary school from 2015 to 2018. It was a landmark project that allowed the school to tap their potable water main to heat and cool the school. After completing the study, they released a report that Egg describes as a great resource for future geothermal projects — including his current project in Oneonta, New York.
Farrell mentions hearing the phrase ‘water energy nexus’ when talking about geothermal energy, and asks Egg to explain. Egg says that water is the best medium for heat exchange in the world and that this nexus is any system that has to do with water that receives that heat energy.
[A] river is part of the water energy nexus. All you have to do is put your devices, your air conditioning exchangers, to exchange heat with that. [The river will] provide all the heating and cooling you need.
The part of the nexus that Egg is interested in is the system of pipes feeding houses in a city: the water main. Here, the interaction between the water source, water use, and water recycling neglects the heat energy that water dispels or absorbs from the earth. Unlocking that resource is key to a cleaner future, Egg notes.
A New Approach to Geothermal
Egg’s approach to geothermal is different, Farrell mentions, because the utility opted to tap into an existing underground system: the water main. The ground beneath the earth’s surface remains a relatively constant temperature year round, as does the temperature of water mains, despite seasonal changes. Geothermal systems use the ground’s constant temperature to extract heating or cooling. Traditional geothermal systems require trenches to install ground loops to harness the heating and cooling potential. The school instead opted to use a spur from the water main to harness the energy of the water main, saving $600,000 by not drilling boreholes.
The water from the spur goes through a double walled heat exchanger to provide the school’s heat and cooling, but the water is never actually used by the school. If the water was recirculated, other water utility customers could use the water even after it has gone through the school’s geothermal system. Egg sees this extension of water utility service as harnessing the valuable energy that flows beneath cities everyday.
One example of larger-scale water main geothermal that Egg comes back to often is in Toronto. The city of Toronto installed heat exchangers on its water main 15 years ago that are still in operation, providing air conditioning to the downtown area.
[Water main geothermal is] not new. It’s just that we’re having a little trouble getting folks to come together on that.
New York County Wrestles with Legal Obstacles
The recent proposed geothermal project in Oneonta, N.Y. was brought about when City Engineer Greg Mattice and City Manager George Korthauer approached Egg with an idea. The city had the idea to connect their water main to a geothermal heat exchanger during recent improvements to the city’s Main Street water line.
Incorporating geothermal heat pumps into a residential water main is simple, explains Egg. Small modifications to an existing water main converts the piping to allow for an exchange of heat energy. The process is similar to how AC/HVAC systems operate to remove or generate heat.
Egg’s work in Oneonta has run into legal problems: state laws restrict the usage of potable water through heat exchangers. According to the New York Division of Environmental Health and Protection, this could pollute the water. Egg disagrees, saying that “perhaps somebody should tell that to Toronto, since they’re doing it.”
It takes a lot of work to actually open your mind, to get a process going, but these are the things that change the world when people will step up and do it.
When Toronto changed to geothermal, the community, the water utility, and businesses all saw savings in heat energy. Those savings also reduced the reliance on electricity or gas, which would have been used to heat or cool homes.
Water utilities prefer to keep hardware that manages water flow in their control. In the case of installing geothermal on a water main, Egg says that the most likely option is the addition of a heat exchanger near the water meter of each building. This exchanger would be easily accessible by the utility and would connect to the water lines responsible for heat absorption.
The heat exchanger would use one unit of electricity to extract and distribute several units of heating and cooling from the water. A heat pump would then deliver cooled or heated air from the heat exchanger throughout the building, but for a fraction of the energy cost.
Read our report on Water Main Geothermal, released October 2020.
Egg says the small upgrade far undercuts the price of digging up the earth and installing ground loops. Those savings would pass right to the water utility and their customers.
Certain issues, like lines that could freeze over in particularly cold climates or communities that need greater cooling capacity during hot summer months, need local solutions. Egg says that these circumstances are where the experience of engineering firms like his would be paramount.
Compared to other sources of heating and cooling, Egg says that geothermal energy has a much diminished carbon footprint. Given the rise of clean, renewable electricity sources, the small amount of electricity required for heat exchange can be even less carbon intensive.
The rise of Egg’s type of geothermal energy in the U.S. has seen many roadblocks, but he assures Farrell and the listeners that he still has hope. He and many others are working tirelessly to change the policies, engineering, and perceptions surrounding this groundbreaking technology.
See these resources for more behind the story:
- Read Jay Egg’s article: Potable Water Thermal Exchange is Opening Opportunities
- Read an article from Newsday announcing Valley Stream Elementary’s geothermal project
For concrete examples of how cities can take action toward gaining more control over their clean energy future, explore ILSR’s Community Power Toolkit.
Explore local and state policies and programs that help advance clean energy goals across the country, using ILSR’s interactive Community Power Map.
This is episode 111 of Local Energy Rules, an ILSR podcast with Energy Democracy Director John Farrell, which shares powerful stories of successful local renewable energy and exposes the policy and practical barriers to its expansion.
Featured Photo Credit: Kent Kanouse (CC BY-NC 2.0)