ASHRAE Journal:
ASHRAE Journal presents.
Drew Champlin:
Welcome to the latest ASHRAE Journal podcast. I'm your host, Drew Champlin, ASHRAE Journal editor. On this episode, we will be talking about district energy systems and designing for longevity.
Alec Cusick:
My name is Alec Cusick. I am a technical lead within Owens Corning's industrial insulation business. I hold a Bachelor of Science in mechanical engineering, and I currently sit in on multiple technical committees within ASHRAE, including TC 6.2 on district energy systems. I also sit in on committees within the National Insulation Association and I'm a level 1 ITC certified infrared thermographer.
Steve Tredinnick:
And I'm Steve Tredinnick. I'm a professional engineer and certified energy manager located outside Chicago. I'm a graduate of Penn State Architectural Engineering program. I have over 40 years experience with close to 30 of that in focusing on district energy and large central plant design and operation. I retired from full-time employment January of this year and formed district energy specialists who are some sole proprietor.
I'm a past member and a member of the Board of Governors of the International Energy Association, IDEA. I'm a ASHRAE Fellow, past Minnesota Chapter president. I'm a corresponding member of TC 6.1, which is Hydronic and Steam Equipment Systems, and TC 6.2, which is District Energy. And also, as a co-author of the ASHRAE District Cooling Guide, second edition.
Gary Phetteplace:
Hello, I'm Gary Phetteplace. I'm the owner and principal in GWA research. I have a three degrees bachelor's from Northeastern, master's from Dartmouth, and Ph.D. from Stanford. And my Ph.D. dissertation was actually on optimal design of district heating systems. So it's something that I've been working on for a long time. I worked for about 33 or 34 years for the US military who is a owner and operator of probably the most mileage of these varied piping systems in the United States with 6,000 miles of systems in place.
So I did a lot of research for them. And since 2007 I've been operating my own company doing research, investigations, and expert witness work for interests in the field of district heating and cooling. Member of TC 6.2 for a long time along with Steve. Authors of the latest District Cooling Guide and also the District Heating Guide.
Drew Champlin:
All right. Well, we'll just jump right into this and get to the basics. First off, what is a district energy system and what are the major components for a district energy system?
Gary Phetteplace:
There's really three major components. It is a system to start with that heats a number of buildings from a single central plant, normally. We're seeing some variations on this now, but sometimes multiple central plants as well. They're very popular on universities. Many of the big cities here in the United States have them. Austin, New York, Philadelphia, Baltimore, I could go on. A lot of college campuses, military bases in Europe, they're even more popular in here and in Denmark, like 55% of the homes actually serve with district heating.
So as I started to say, There's three main components to the system. There's a central plant, there's a distribution system which takes the heated steam or hot water or for cooling purposes it would be chilled water from the central plant out to the consumers which are individual buildings. That's really the nuts and bolts of the system and those three major components and today we're really only going to talk about the distribution system part of it. It often is the most expensive part of the proposition.
Steve Tredinnick:
And the only thing I wanted to add to that is there's been a big almost logarithmic growth in the Middle East, which is where the ASHRAE District Cooling Guide was focused on the audience for that document. They have extremely large systems over there with extremely high cooling demands as well.
Drew Champlin:
That leads me into my next question. Where are the district energy systems more prevalent?
Gary Phetteplace:
Well, a bunch of those applications that I spoke of, military bases, university campuses is generally where the loads are dense and high. That's the most favorable condition. So that's why they exist and flourish in the downtown areas of places like New York City and Boston, and Detroit, and et cetera. And as Steve said, "Big cooling systems in the Middle East, in Europe." Big district heating systems, most major cities and as I said, "Denmark, it's a giant network there. So that's the applications historically. We're starting to see changes now that are being driven by trying to decarbonize the building heating and cooling industry or methods.
Steve Tredinnick:
The only thing I can add to that is as Gary mentioned, a lot of the larger systems or older systems are with a common system owner that also is the customer base, if you will. So United States government on military bases, Department of Energy labs, and similarly the college and university, it has a lot of economies of scale and maintenance and operation savings over having plants in each individual building.
Drew Champlin:
What is the current state of the art of district energy right now?
Steve Tredinnick:
We're seeing a lot of the effort going into decarbonization and as the Scandinavians define things, the fifth generation, or ambient loops where you would have a common loop as a heat sink source, and each building would have its own heat pump and you would circulate this heat source throughout a campus or city and each building's or customer's heat pump would either add or take heat from the loop.
As I say, that's what's called 5G or Fifth Generation, not to be confused with 5G mobile service. Fourth Generation for District Heating is definitely lower temperature, but it's still within a normal temperature range. A lot of these temperatures and specifics are outlined in either the ASHRAE District Heating Guide or the ASHRAE Handbook Chapter and systems on District Heating and Cooling.
Gary Phetteplace:
I think that's good. And the only thing I would add to what Steve said is one of the reasons that these can help in decarbonization is sharing of loads and so that the simultaneous heating and cooling that's going on these ambient temperature loop systems that can accommodate heat pumps either dumping to them or taking from them, that is one of the reasons why they're seeing increased emphasis.
There is other things also like they're able to take advantage of sources of heat or heat sinks that would be hard for individual buildings like for instance, data centers or mine water or seawater, even, the seawater system built in operating in Europe. And when I say seawater, they're not circulating seawater, they're using it as a heat source or heat sink.
Steve Tredinnick:
And the sources are very diverse. As Gary said, we have a lot more mature systems out in Europe in some of the heat sources to the loop. Or even like crematoriums as odd examples, but they'll grab any BTU they can and add it to the distribution loop. The only thing I wanted to add to that would be the reason why you don't see it everywhere is that it's extremely capital intensive to put the system in and as Gary said that, the distribution system is a big portion of that expense. So having a dense load distribution or dense load to the area reduces the cost of the distribution system and makes things a lot more competitive. Typically, as you see in the ASHRAE Guide, in the ASHRAE Handbook Chapter, there's an example on how to evaluate a self-generated heating or cooling system to a district cooling offer contract. And there's just a lot of components that goes into that analysis. And I think that's one of the reasons why you don't see it everywhere is that people have this perception that it's going to cost more and then once you sign a contract, you're subservient to the district energy provider.
And to be honest with you, the analyses that I have done, it's basically a wash or it's a benefit of connecting to a district energy system over the contract of the system, especially when you consider the capital outlay of the plant that you would have to have and the maintenance and operations of that. So it's not just energy costs, it's everything that goes in with that.
Gary Phetteplace:
That explains a lot why you see them applied. Where you do as people historically to have a longer timeframe for the lifecycle costs like university campuses, they're not necessarily looking for a 10-year payback. To them 100 years is their timescale. So it's people like the military and them and in big cities where there's enough load so that consumers can come and go, but there's going to be an upload there. And then the reason in Europe that you see it's better energy wise and they tend to take a long-term view on investments, especially in the Scandinavian countries.
Drew Champlin:
Moving right along guys, what are these specific challenges in direct-buried, tunnel and vaulted applications?
Alec Cusick:
Sure, absolutely. I'm excited to get your guys' perspective on this. Being an installation guy, I'm dealing with these pipes after they're in place and we got to put the installation system together. There are some unique challenges that we see that underground systems do have to experience. In direct-buried scenarios, you need to consider all the load that's going to be subject to your piping and the insulation onset piping. That's a combination of the soil backfill load after they dig the hole, put the piping in and put all the soil back on top of it.
That's going to apply some compressive forces to that piping system. But that also has to incorporate the live load of whatever's going to be on the surface of the ground above that system. So your insulation needs to withstand the soil being loaded back on top of it as well as any roadways, foot traffic, vehicles that might be present on a road that's passing along your piping systems overhead.
So you definitely need to make sure your insulation system has the compressive strength to mechanically be durable enough throughout the life of the district energy system. Hydrostatic pressure with any groundwater present is also going to be something to consider. Moisture is widely regarded as one of insulation's biggest enemies. Installations that can become saturated with water are very less thermally efficient. So if you're installing a direct-buried system in a geographic area of high-water table, you need to make sure the insulation material as well as the system as a whole can withstand water ingress from any soil water that's just going to be present throughout the life of the system.
For that reason, low permeability installations, as well as the selection of proper accessory materials, whether that be sealants and jacketings, those can all go a long way when designed properly to make sure that water stays out and is not affecting your installations R-value throughout the life of the system. And one of the thing I'd like to point out right off the bat is soil itself isn't the best insulator.
So if you have an instance where you have an insulation failure and you've got steam or hot water lines that are traveling congruently or nearby to your chilled water lines, if your insulation's not up to snuff, you could actually have heat that's escaping from your hot water or steamline and traveling directly into your adjacent chilled water line and then all of a sudden you're asking, "How come you're not getting the cooling effect that you desire for all the buildings you're trying to cool?" So insulation, there's a lot to be considered a lot of unique challenges when designing in an underground scenario, but that's why we like to work to make sure the system's going to be closed off from outside water and really be able to resist becoming compromised throughout the life of the district energy system.
Gary Phetteplace:
There's a lot of approaches that have been made in order to do just what Alec says to try to keep the water away from the insulation. And so one of the systems that was used very early on was steam tunnels and they've actually put tunnels, some of them big enough to walk through and put the system inside of there. That's an expensive type of construction.
So other alternatives were developed, trenches and then direct burial solutions. But it comes down to what Alec said, "You've got to keep the water away from the insulation." And so if you look in the ASHRAE Handbook, Chapter 12 and the system's volume, systems and equipment they call it, or the District Heating and District Cooling Guides that ASHRAE published. You'll see all of the ways of doing this that have been reasonably successful, some more than others, and they all have that focus more or less, is to try to keep the groundwater away from the insulation. The ground is not a favorable place other than you can't see it. And that turns out to be one of the unfavorable things. And soil, as Alec said, "Is not a very good insulator in most cases." And so don't fall into the trap of thinking if you bury the line deeply because you got a lot of soil on it, you've insulated it.
What you've done is made it incredibly hard to do any kind of service to increase the cost of construction, et cetera, et cetera, and made it put it in an environment where it's more susceptible to groundwater because of the hydrostatic head. So that's my two cents on that. That's the distribution part of the system requires some respect. It's not like making a waterline or a sewer line. It's a much different, more challenging task.
Steve Tredinnick:
And the only thing I want to add to that would be the challenges is cost, and again, longevity, but direct-buried is probably the cheapest installation that you can do. There's pre insulated products for that mitigate any type of joint failure or seams that you would have because you can do it, stick rope and apply insulation and put a jacket on it. Tunnels come in different variations. Gary mentioned the guides have this shallow tunnel, deep tunnel, walkable tunnels, and they all come with their expenses.
I think one of the things that I've seen is there's a shallow trench or shallow tunnel where the lid of the culvert or tunnel is actually like a sidewalk. And if it's adjacency to either streets or deicing, putting a lot of salt and freeze and thaw, and freeze and thaw, you have a lot of moisture and intrusion into the tunnel that can corrode the pipe supports and any bare metal, even the concrete itself, any rebar in it. So there's a lot of concern on not only the design, but it's the maintenance of it and trying to be sensible to not putting a lot of salt or locating the trench or the tunnel to where it's not going to have a lot of the ancillary damage.
Alec Cusick:
That's a great call out, Steve. And one thing I'd like to mention just from my observations is oftentimes these tunnels can be designed with the best intentions in mind and thought of as a suitable alternative to direct-buried systems. However, regardless as to how well we engineer things and how well our thoughts are, oftentimes these tunnels throughout enough years in cycle, throughout the salt exposure that Steve just mentioned, we've seen tunnels that weren't intended to get exposed to water experience flooding events, rainwater from the soil finds its way in.
So just because you have a tunnel that's closed off from the outside soil doesn't mean it's 100% guaranteed to not see some water exposure at some point down the road. So the installation system still should be just as high of a priority in that instance. Just because you have a tunnel doesn't get you off scot-free as much as we'd like to think it does.
Gary Phetteplace:
Yeah, that's a very good point. And if you look inside of the ASHRAE Design Guides that I mentioned in the handbook chapter, we'll tell you to design the system to expect that it's going to get wet at some point during this lifetime. You shouldn't allow that condition to go on obviously, but you got to expect it and be able to deal with it. And that said, I have been in tunnels that are 100 years old and still functioning. But they're costly, as Steve points out.
But much like a tunnel, these systems also have what we call vaults or manholes. And even direct-buried systems will have these, they're places where we can trap the condensate and drain it out of the system, have valves and things like that. And so these are buried and they're subject to the same environment. So you need to pay attention to the design of those.
And again, the ASHRAE documents help you with that suggested designs and details and stuff. So you got to allow for adequate drainage of the manholes and plan on them getting flooded, not just once in a lifetime, probably more than once. So some pumps or positive drainage of other types have to be included. And it turns out that in direct-buried systems, sometimes the manholes can serve as the Achilles heel of the system allowing access of water through the manhole into the direct-buried portions of the system.
Drew Champlin:
It's interesting stuff guys. With all that being said, how can decisions made at the design stage support longevity of district energy systems?
Steve Tredinnick:
I think for the longevity, we've mentioned expense. So district energy systems typically don't really spare any expense and they put in high quality materials, so they do last longer. But you need robust equipment, adequate space for expansion, and that also expands to the piping itself that expect growth. So you need some robustness and resiliency in the design of the system. You're typically using premium efficient equipment.
One of the tricks I like to do is to oversize the cooling towers with a higher degree wet bulb. That response to some climate resiliency for the global climate change is getting warmer as well as the wet bulb it initially oversize as the cooling towers were they're extremely efficient, have a very close approach to wet bulb in the initial years and it builds in a little bit of scaling factor in it, so they'll slowly lose the capacity before you have to replace the fill.
But oversizing things to make it more efficient and last longer knowing that this is going to be typical contracts are 20 to 25 years, but the systems themselves are out there 50 plus years, that includes a distribution system, so it's expensive initially, you just don't want to have to continually expend money for something that you cheapened up on initially.
Another item is distribution loops, and just like the city water grid or electric grid, you have multiple points of access or service to a customer. I know it's probably a future topic, but the initial operation of the system—let's just say you design a 30,000-ton plant, you're not going to have 30,000 tons of initial load. It may only be 1,000, 2000 or less.
So one lesson that I had learned that was actually an error or an omission on my part was thinking that small, that on a 30,000 ton system, the first customer might be 500 tons, we decided not to insulate the chilled water supply piping on a 30-inch main because it was deep enough and we'd have the adequate velocity in the piping system to keep the ground cool, if you will, and not have a lot of heat loss. But we didn't anticipate having initial customer being 500 tons at the remote part of the system with a huge pipe with minimum flow.
And they were a cold air distribution system, so they needed 38-degree water to their building and we actually had to open up some bypass valves to keep the water cold there for the first year of operation just to keep them satisfied. And I think if insulating that supply pipe would've helped, that type of 20-20 hindsight would've helped quite a bit. But again, it was we decided to cheapen up just a little bit and there was a success story that the customer was happy, but it was a little bit of a scramble with the realization that we should probably insulated that pipe.
Gary Phetteplace:
The insulation is not something that you want to try to cheap out on for that reason because it protects you also against things like inflation of fuel costs and stuff that you might not have realized. And nobody is ever going to complain to you that you're not losing enough heat or not gaining enough heat. It's always going to be the other round. So it's better not to do that, try to get by with too little insulation in the first instance.
And one point I would like to make is I've already talked about the ASHRAE Guides in the ASHRAE Handbook Chapter. I think that you should look in there if you haven't dealt with one of these things because we tell you how to design the insulation system, how to do all the calculation, we got soil properties. We always recommend that you get the insulation properties right from the insulation manufacturer whose insulation you're going to use, but we got typical properties inside there.
We even have properties for obsolete installations in case you should want to do some calculations on some system that's made of asbestos and manganese. So it's all in there in the calculational methods and there's an example for everything. And a District Cooling Guide does using an example for what Steve just mentioned, a service line that has a small, connected load in the beginning but is size for the built-out load. So that's a special case, but you've got to make sure that you allow for it. So it's a special case of thermal design of the system.
And you've got to actually remember to design your plant to include those loads that are on from the distribution system.
Alec Cusick:
Yeah, that was a great story Steve, it's funny to hear a real-life scenario of just this because oftentimes we see projects where the installation from a total cost perspective might be one or 2% of all the other costs associated with billing a facility or a project. So it becomes an afterthought for a lot of people from an engineering perspective, but you're not going to find any component of the whole facility design that's going to yield a better return on your investment often than the insulation itself. So definitely to echo both Steve and Gary, not something to consider an afterthought until it's too late.
Drew Champlin:
So district energy systems are often located in environments subject to significant shifts in loads such as campus-based systems. What impact does load variation have on a system?
Gary Phetteplace:
For one thing, when you're building one of these systems, you should start off with a good master plan. And even if you're operating one of these systems, if you don't have a master plan for your campus or whatever it is it's covering, then you should get one. And if you look inside of the District Heating Cooling Guides, they'll tell you how to make one of those master plans and what's important to include. But the best laid plans are going to change.
And so if you do what Steve says and you provide some extra cushion, and then also distribution systems because they're expensive, they tend to be laid out in tree-like structures, with branches out to serve each one of the consumers. But when you're doing it, look for possibilities to loop the system to interconnect some of the branches so that a customer can be served from basically two different directions. It will help you deal with that potential change in load, and it's a lot easier to build a little interconnect between two branches and it is to dig up something so you can upsize a pipe, especially in a urban or really highly developed, like New York City, environment.
Steve Tredinnick:
I think a lot of the noodle work that you do up front helps you in the long work run. So it's trying to understand the low profile of the system and what comes on first, how the system grows. And the master plan, as Gary said should assist with that. So if you have a system that's going to grow slowly, your increments of heating or cooling have to have adequate turndown for the shoulder seasons or off-peak seasons. So having a pony chiller or pony boiler initially is probably smart to turn down the loads.
And on the other hand, morning warmup or if you have a computer, high performance computing, which have extremely rapid warmups or cool downs, having some thermal storage system in the system will assist with that or having multiple units of production active and just sure limping along knowing that something's going to spike in the short term is having that ruling inventory of generation. And some systems are big enough that the volume of water in the pipe or hydronic systems actually acts as a thermal storage tank. There's just enough energy stored and there for either a spike load or morning cool down or warmup with that assist. So that's the benefit of a big system.
Gary Phetteplace:
And the systems I was talking about in Denmark, all of Copenhagen in the surrounding areas are hooked into a giant interconnected system and they do, especially for Copenhagen, just exactly what Steve was talking about for the Monday morning warmup, they're charging a network ahead of time, so if they normally run it at a supply temperature of 200° or 220°F something like that, they're going to throw an extra 10 degrees or maybe more inside of there. So when they get hit with that slug of load, when everybody opens their office on Monday morning, they're ready for it. And the hot water has got an awful lot of thermal capacity, a thermal inertia in it.
Drew Champlin:
Well, what impact can moisture have on the insulation or energy efficiency of a district energy system?
Alec Cusick:
As I quickly mentioned earlier, moisture is commonly referred to as one of insulation's biggest enemies in any application. The way most installations on the market actually work is by suspending pockets of air amongst some solid medium. So you break up the convection that heat can take through a gas and conduction that it takes through a solid and break it up into multiple individual pockets of air that the heat has to travel through.
Now, if you replace that air that's suspended in, let’s say the thickness of fiberglass or calcium silicone or any other type of insulation product, that insulation's efficiency will drop because water is a very much a better conductor of heat than air is. So your goal with any insulation system should be to maintain the integrity of those air pockets that are suspended within the thickness of the insulation, however, that may be.
For a lot of insulation products that comes down to the accessories that you use on the system as a whole. In that case, you want to make sure you're sealing all terminations entry points into manholes like Gary was talking about earlier, being a common fail point. If you're not sealing the ends of those pipes down, that's an entry place where water could squeeze its way in. You want to make sure joint sealant is used between segments of insulation.
We recommend cellular glass for a lot of high-water table underground scenarios just because we know the system is going to be exposed to so much constant hydrostatic pressure from water. In that case, it's a zero permeability insulation. So at the very least, the R-value is being maintained throughout the life of the system. But generally speaking, keeping water out should be your number one goal to maintaining your thermal resistance of an insulation system throughout its lifetime.
Gary Phetteplace:
And I would just add to that furthermore, ASHRAE did research on the impacts of moisture on the common insulation systems used in district energy systems. And so that's published in the Handbook chapter 12, the systems and equipment volume. And also, in District Heating and Cooling Guides I believe that all that research is there. It can give you some idea of what the impacts are. And for instance, with mineral wool, the factor, I happen to remember that one, it could be 50 times increase in your heat transfers for saturated mineral wool. So you want to keep it dry.
Alec Cusick:
Exactly. And it doesn't take much water to get in to have that effect.
Steve Tredinnick:
Yeah, there's seasonal things too is where steam or hot water, you may have the opportunity to dry it out eventually, but chilled water, you don't have that opportunity. Once it's wet, it's probably not going to dry out, especially if it runs all year long.
Gary Phetteplace:
In fact, what it's going to do is try to draw more moisture in. So the moisture drive is away from the heated pipe, but it's towards a chilled pipe or any pipe that's below its environmental temperature. So that chilled water is particularly difficult.
Alec Cusick:
That's a great point, and I'd like to call out the presence of tunnels. Tunnels often put steam pipes and chilled water pipes in very close proximity where they have to share one airspace. Now, if you use an insulation system that wasn't thought out too well and both installations become compromised, you could have an instance where your steam pipe is heating up and baking the airspace in that tunnel and making a very harsh, high temperature, potentially high humidity environment that just wants to drive all that vapor towards that cold pipe like Gary said. So especially when you have steam and chilled water pipes in close proximity, keeping those insulation systems intact is very much of your best interest. If things go awry, the steam and chilled water lines can play not so nicely together when they’re that close.
Gary Phetteplace:
Absolutely, and the only good side to that story is that if you have a tunnel that’s a walkthrough tunnel, you can replace the insulation or upgrade the insulation so you’re not is locked in. That’s another valuable part of that type of construction, but it is very expensive.
Steve Tredinnick:
Yeah, Alec, can probably add to this comment, but a lot of the call it a pro-tip for cooling systems is you paint the pipe next outside of the pipe before you insulate it just to add a little bit of barrier because there’s some installations that once they’re wet, they form an acid that will corrode from the outside in, and that’s the opposite way you want your pipe to age is you want it from the inside out.
Alec Cusick:
Yes, coatings are very common in the insulation industry. They can help a ton with CUI type of concerns, CUI being Corrosion Underneath Insulation. There’s a lot of good insulation materials on the market, cellular glass being one type of material. Since, the material itself is zero perm, you're a little less concerned with moisture drive getting into the insulation thickness itself.
But even in that case, you definitely need to look at all the joints between segments of insulation. Just because you have a low perm or a zero perm material doesn't mean there's no entry ways for water to get in towards that pipe surface. You need to make sure that the right joint sealant is being used between segments of insulation. Anytime you have a termination, a protrusion coming out of the pipe for a pipe support or a hanger. Those are all common failure points where they can present avenues for moisture to get in. So yes, there's a lot to consider in designing a complete zero perm installation system, but it's well worth it at the end of the day.
Drew Champlin:
Given recent extreme flooding events in the United States, what factors should be considered to protect against water intrusion and the risk that it poses to buried pipes?
Gary Phetteplace:
I guess the way I would start is by saying that you need to go back and look at if you designed your system as we would recommend to be able to handle that event at least periodically. Well, if it's going to happen more often than beef up your system a little bit. So make sure that all your drainage things are working properly that you've got—Usually we would recommend duplex sump pumps in a manhole for instance, not just one, but two.
Make sure that you're going into the manholes and cleaning debris out of the manholes that could clog the pump inlets or other forms of drainage that you have in the manhole. So I think that would be the first thing I'd do would be start to beef up the things that I already had in my design or should have had in my design.
Steve Tredinnick:
The only thing I can add to that is the weakness in hydronic or even steam systems is the field joint for pre-insulated piping systems or direct-buried and to have a double heat shrink wrap built-in suspenders to provide a little bit more protection on that joint. It's not that much of an expense to get a little bit more sleep at night factor for longevity of systems.
Alec Cusick:
That's a great call out and there's some nuance to the best practice of installing said jacketings. So I know for our systems that we recommend, we have some jacketing that are self-seal. They can be applied just with pressure by a contractor in the field. There are also ones that are torch applied where you actually have to heat up melt a bitumen-based membrane.
In those instances, it can actually be advantageous, counterintuitive to some people, but advantageous to have the shiplap of the jacketing actually facing upwards so that as your blow torching the asphalt jacketing, it lets it melt and fall back into itself to create a really efficient seal throughout the life of the system. There's some tricks of the trade there, but yes, jacketing at joints, definitely something we recommend in underground scenarios just because of how much moisture is really going to be present quite frequently.
Gary Phetteplace:
Yeah, pay attention to what the manufacturer is recommending to you and follow it in the installation.
Drew Champlin:
Well, are there any visible symptoms to look for that would indicate a problem with the installation system within piping systems?
Alec Cusick:
That's a good question. Oftentimes it can be comical how evident it can really be if you have a problem with installation, if it's a direct-buried system. We've seen examples where in the wintertime snow's falling on the ground and there's a patch of green grass with melted snow all along the surface of it in a straight line. And to those that are walking on the surface, they might not know what it is. But to a designer of a district energy system, that might mean your steam system's insulation is no good no more because it's got a lot of heat melting the snow above it.
So things like that can be quite apparent. Oftentimes, it's not as easy to spot in instances where insulation extends to above ground, you want to make sure there's no visible signs of mold, mildew, dripping water from any exposed piping. Because that could also be a telltale sign that may be on a chilled water system the insulation's not achieving its thermal resistance that it should. So sometimes insulation can be finicky. Oftentimes it's hidden beneath jacketings, but there are some telltale signs that can go off as an early alarm. That is something to look into.
Steve Tredinnick:
Yeah. Conversely, the summertime on that same steam or hot water line that melts the snow in the summertime there's the burned out grass, you can see it seasonally long and the snow is like mother nature's infrared camera that you can use an IR camera to try to detect whether some either steam leaks or hydronic leaks, either thermally or just true leaks. And then Gary, I think you're probably a little bit more in tune to some of the hydronic systems and steam systems on the pre insulated product have some integral leak detection systems.
Gary Phetteplace:
Yeah, that's right. There's several systems that are in use and I don't want to get into the scope of the systems as the technology gets a little bit complicated, but there are several systems, some that are suitable for use with systems such as conduits that have air spaces and others that are buried in the insulation and are constantly monitoring to see if the insulation is picking up moisture. So those types of systems can be installed originally and help you monitor it.
And Steve mentioned infrared survey is a great tool and you can do aerial surveys, and now actually they're doing them via drone. So that really cuts down the cost of an infrared survey. And from the air, you can get a big picture of what your situation is and if you do have areas of significant heat leakage. But if you want to follow up from the ground, you can actually learn more. And there's even methods that have been used to predict what the heat loss is based on the temperature signature at the ground surface.
And so the methods that Alec and Steve mentioned about the burnt grass and the melting snow, those are the two most common ones that I'll just tell you in Fort Wainwright, Alaska where I was working. They had a tunnel system there and I was there in April because of such a cold climate, there was still snow on the ground and children were playing baseball on top of the utilidor because it had melted such a wide swath of snow. It was a little bit of a narrow field, but it was very deep. And that's one of those tunnel systems that unfortunately had insulation that was not very good. It was old asbestos-based stuff, which made it difficult to get rid of and et cetera, et cetera. They did not have chill water and unfortunately enough.
Drew Champlin:
Well, Gary, I know you've mentioned some ASHRAE material throughout the podcast where listeners can refer to, but is there anything you wanted to add to that or mention again, just some key points of reading where if people wanted to go check some references or anything like that?
Gary Phetteplace:
Yeah, let me just try to give a little bit more proper recitation of their titles and such. And so in the ASHRAE Handbooks, most everybody is ASHRAE member is familiar with those because they get one every year. In the systems and equipment volume, which the most recent one would be 2020, so that would be the most recent version of that. And its chapter 12, and I think it's called district energy systems, is that right Steve?
Steve Tredinnick:
District Heating and Cooling, if I call it. Yeah. The TC is district energy not to be confusing.
Gary Phetteplace:
Which is TC 6.2, by the way. And so if you really want to get in depth to this topic, come to some of those meetings and you'll see Steve and I there now and then either live or virtual. And then there's two handbooks that were written by ASHRAE to provide additional detail beyond what was in the actual ASHRAE Handbook Chapter. And so there's a District Heating Guide is what is called, and that was published first in 2013.
At the same time in 2013, there was a District Cooling Guide published, and those are called the District Heating Guide and the District Cooling Guide. And if you look in the ASHRAE Bookstore, you'll find them. The District Cooling Guide was updated in 2019 and there was also an additional publication that came with it. That has a long title is something like, "Guide for building owners for buildings serve with district cooling."
Steve maybe can help me with the title, but basically what it does is tells you if you have a system, a district cooling system, and you want to design a building to attach to it, read what this says because anybody that knows district cooling systems will know that Delta T is a big problem. Well, it's controlled from the building and no place out. So we try to tell people how to design the system inside the building in that particular publication.
Drew Champlin:
Well, Alec, Gary, and Steve, thank you so much for sharing your time and your expertise on this ASHRAE Journal Podcast episode.
Alec Cusick:
Yeah, thanks so much. This was exciting to be a part of.
Steve Tredinnick:
You're welcome.
Gary Phetteplace:
Yeah. Thank you for the opportunity.
Drew Champlin:
I'm Drew Champlin, ASHRAE Journal editor. Thank you so much for listening.
ASHRAE Journal:
The ASHRAE Journal Podcast team is editor, Drew Champlin; managing editor, Kelley Barraza; producer and associate editor, Chadd Jones; assistant editor, Kaitlyn Baich; associate editor, Tani Palefski; creative designer, Teresa Carboni; and technical editor, Rebecca Matyasovski. Copyright ASHRAE. The views expressed in this podcast are those of individuals only and not of ASHRAE, its sponsors or advertisers. Please refer to ashrae.org/podcast for the full disclaimer.