Video Transcript – Ice Rink HVAC System and Design

Hi everybody. I’m Andrew Knutson. I’m starting things off for team CFM. We had the ice rink HVAC system and design project and Matt if you want to kick it to the next slide for me real quick. So our project is about the theoretical design around this facility you’re seeing rendered right here. It’s a theoretical facility for two ice skating rinks here in the Treasure Valley. It would contain two Olympic-sized ice skating rinks contained in those two large enclosures you see on the right and left with a small area in the middle for facilities administration, food, etc. Now if we flip to the next slide I can outline our project objectives which were to determine the heat loads for this entire building, be it what we need to cool off the ice rinks, what we need to do to keep things comfortable for visitors, what we need to do to keep the facility functioning and within spec for regulations due to comfort or how the ice rinks need to stay cold. And then from there we needed to determine how to achieve those goals – what kind of systems do we need to use to achieve those heat load goals. Do we need to use a direct or indirect system which some of my teammates will get into later during this presentation? What kind of refrigerant do we need to use? There’s several choices: ammonia, Freon, CO2 etc. and then the most important objective of this project was the cost analysis of operating this facility. We wanted to design in the big view sense of what kind of system would allow us to have the most cost efficient facility in the Treasure Valley because cost efficiency is what drives the ability to run a facility. If it costs too much to run you’re gonna have to charge people more to use it. If people won’t use it, you’ll go out of business. So I will now pass it on to I believe Bobby for the next section of our presentation.

All right good afternoon everyone. Thank you very much for that introduction. My name is Bobby Herlt we’ll take a moment here and talk about our ethics and ethics decision-making process during this project. So our guiding principle or our benchmark for ethical study here was provided by the Makula center for applied ethics and we from that looked at five, the five, different ethical perspectives that you can read there. So one of the unique things about our project was it’s highly codified meaning that we are moving within constraints that are already defined for us. So that really narrowed down our ethical, any type of ethical dilemmas that we would have, meaning we didn’t have any at all. And as a matter of fact too as a team we wanted to make sure that employees in the future that would be working with the system that we’ve developed would receive extra training in order to try to mitigate some of those things as well. If you go ahead and go to the next slide Matt.

So as we continued through and we we entered all of our parameters for our assessment we come back with an ethical score of 96. And it just confirmed what we already knew as a team, that we were you know operating very ethically within in our decision making which kind of circled back to how we felt as a team that we felt informed throughout the whole process and you know we felt very enabled as a team to make good smart decisions. And one more end of that, there wasn’t an internal struggle with this particular team trying to choose courses of action. So with the way that the parameters were set up we were pretty well defined and worked out very well ethically going forward. So having said that I’m going to go ahead and pass it over to John who’s going to continue the presentation.

Hello everyone my name is John Bowman and today I’m going to be talking about the chiller system which is used to cool the ice. Now in order to cool the ice we need a refrigerant. And for ice rinks the main choices you have are ammonia and CO2. Ammonia has been around for a long time it’s very efficient however it is toxic whereas CO2 is fairly new. Actually the first ice rink to use 100% CO2 as a refrigerant was in 2010. So just 10 years ago. So it’s very new. An advantage of it is that it requires high pressure and so that pressure can be used to heat the rest of the facility by utilizing excess heat from the condenser. And so if you want to go onto the next slide we’ll talk about the the chiller type.

So there’s two main types that you can run a chiller. The first and most efficient type is the the direct type of chiller and that runs the refrigerant directly under the ice. And then you also have the indirect where the refrigerant indirectly cools ground water, which then that is what is actually run under the ice. And so the indirect system is much safer and less refrigerant is needed. Ammonia’s is much more toxic and so with that we would only be considering the indirect system whereas CO2 since it’s safer we can utilize the the efficiency of the direct system and use that for CO2. So on the next slide, if you can go on to the next. There we go.

So here’s how I decided which refrigerant to use and which which type of chiller type. So I first used the diagram on the right to figure out the COP and what that actually is is it’s the amount of electricity that’s used for every unit of heat that needs to be removed from the ice. Next I figured out that amount that needs to be removed from the ice which is the cooling load. Then finally I’ve determined the power needed to be able to run the compressor, to run both systems. And then finally from that I could determine the the cost of the electricity to be able to run both systems. And so on the next slide.

Here’s the maximum amount of power that is required to run each type. And how I determine this was I did that calculation but on the hottest day of the year, so that’s a worst case scenario. And from that you find that ammonia is more efficient because it’s got a much higher coefficient of performance and because of that the amount of power is much lower than CO2 and so it’s much much cheaper to run ammonia with an indirect system. And then on the next slide I’ll talk about the average throughout the year.

And so this is where it’s kind of interesting you’ll see that on average CO2 and ammonia during the winter months is very similar but then when you get to the summer you see that CO2 becomes drastically less efficient. And that’s because at that point it actually becomes transcritical so what that means is the condenser isn’t able to actually condense the CO2 to a liquid because it’s just too hot outside. And so to overcome that you need to actually add extra pressure to be able to uh needs to be added to the compressor to be able to reduce it to a liquid to be able to use it. And then after this Matt is going to talk about how some of the costs can actually be saved with the CO2 system by reusing some of that excess heat to heat up the rest of the facility.

Thanks John. John just finished up a comparison as which type of chiller would work best in the Treasure Valley. One thing we wanted to make note was the elevation we’re currently at. We’re at roughly 2,800 square feet we just round up to 3,000 square feet for simplicity. And everything to the south of 3,000 square feet you know uh 1,000, 2,000 square feet uses ammonia and everything north uh 3,000 plus typically uses CO2. That was just one thing I wanted to bring in before we went over this but if you look at the CO2 chillers the CO2 chillers can use the heat that is generated by the chiller system and recycle that from heating the rest of the facility, which in turn uses more electricity to power the equipment to do so. That costs around $55,000 a year and that’s what the graph is showing you. It shows the electricity for each month. The more conventional approach in the Treasure Valley is everyone uses natural gas which is about $45,000 a year and that’s what we did the HVAC design around. On this slide here you’re looking at the table graph and it shows the heat generated for just one ice rink which is about 25,000 square feet. You’ll notice some negative numbers around the floor transmission. That would be the ice rink chillers itself and you’ll notice how high those numbers are in the opposite direction. One thing to note for this facility is there is a lot of roof transmission and wall transmission. The roof transmission itself is based off of how big the the roof itself is. It’s 25,000 square feet so you’re getting a lot of energy through the roof and that temperature on the roof at the hottest days per year is about 171 degrees Fahrenheit. And then in this table here you’re looking at the reception area. One thing to note here is the people. Each ice rink we did a calculation of around 900 people in that facility and that was just for the standards we used in ashrae. And in the reception area just out of the sheer volume of people and how the people are burning energy as opposed to the ice rink they would most of them would be sitting. In the reception area everyone’s gonna be walking around, they’re gonna be eating, they’re gonna be doing all those things. So that’s where the energy, that’s where the heat generations really come from for those people. And you’ll also notice that the partition in the floor transmission is negative. The partition transmission would be the energy that is being taken from the ice or that’s going to the ice rink walls. And then the floor we’re using we would we did a concrete slab so the slab was also taking energy as well. This is the overview of the heat generation for the whole facility. I put them together just so you had a comparison. Notice the people how it’s really high in the recreational zones and then the ice rink how much floor transmission is for the floor itself.

And then when you look at the economics you’ll notice that the orange tab itself or the ice rink chillers and I put the cost effectiveness. And then I put the blue tab itself says the HVAC so you’re looking at about you know eleven thousand dollars for worst case scenario a month just to power this facility and then whenever you’re most efficient you’re looking at just under under six.

Hi my name is Adam King. I’ll be taking over the rest of the presentation. Kind of think about planning for the future you know. During this current pandemic we actually made our system capable of providing 100% outside air. And what that means is we have some optional vent fans they’ve been turned on instead of recycling some of the air we can actually output all 100% air from the outside. You know this is an industry and HVAC that they’re still learning a lot of best ways to design about the current pandemic and making sure that we can provide a clean environment. And so this is one of those things that we included on our design in the scenario that more HVAC facilities are kind of moving this direction so it’s a I think it’s a good opportunity for us to plan for the future.

All right in conclusion you know from our findings we did a lot of calculations, analysis, and design. We overcame a lot of current pandemic challenges during this project and we even were able to take some of those things into including in our design. And we calculated the heat load for the entire facility. We even chose a chiller based on cost efficiency. Using our results and findings we’ve concluded that ammonia indirect system is going to be the most efficient for a treasure of this facility in the Treasure Valley. And at this time we have opportunity to answer any questions that you may have. Feel free.

Thank you for that presentation I just have a quick one. What does CFM stand for is that cubic feet per minute or how do you come up that name?

Matt you want to answer that one? It does. That would be cubic feet per minute. We just decided to do a pun on the HVAC world. All right, thank you.

So I have a question, and I know a little bit about ammonium systems. And so one of the things that you know, they’re highly regulated right? We mentioned this earlier but ammonia is particularly regulated because it is so toxic and there’s a, there’s a threshold of amount the number of pounds of ammonia you have on site, that if you get above that a whole other set of regulations kick in. Did you run into that? If you looked into that, do you know where you sit in that in that spectrum with how this design was set?

So that’s a big reason why we chose the indirect system since that uses very little ammonia and I can’t remember what that exact amount is, what that threshold is where those extra regulations start to kick in. But the advantage if we would have used a direct system which would be slightly more efficient, we would run into all those issues. And so that’s why we chose the indirect system so it limited the amount of ammonia that we actually had to use.

Okay and can I elaborate a little bit on that for some people that may not know the difference between direct and indirect? For a direct system you would be pumping the fluid underneath the ice and for a 20,000 square foot ice rink that would be a lot of refrigerant that you’d be using to pump under the ice. So we used a refrigerant in that case and that is where most of our refrigerant is and we’re using an indirect system that uses ammonia and uses this much smaller amount that is transferring the energy through those two fluids. And also all that ammonia is contained in a special area away from the people. So worst case if there was a leak it would just be that area that would have to be shut down, whereas with the other type of system if there was a leak it would be running throughout the entire facility and everything would have to get shut down. So not only do you limit the amount of refrigerant needed with the type of system that we use but it’s also away from the majority of people in case something does go wrong.

So speaking of that, I don’t know if anyone anybody on the team has ever been downtown. So you know where the Idaho Power building is, I think it’s like 13th and Main or something. On the corner of that is a dairy processor and they have a wind sock on every corner of that building. And I would see that for years. I’d go down and visit people I know at Idaho Power and I’d say, why do they have a wind sock there? And I’d look in the satellite view and there’s no heliport up there. You know, there’s just nothing but you know, buildings and machines and stuff. And and the answer is that they’ve got a ammonium-based chiller system there and the windsock is so when you hear the alarm you know which way to run. You want to run up wind. So that’s, it’s a little, you know a little uh little known fact, that they don’t tell anybody else that, just the employees. But you know, so yeah, it’s an incredibly potentially dangerous thing and yet we use it all the time. I’ve taken students through a dozen factories that have ammonium chillers. It’s a technology that’s gone very well with very little, very very few problems.

Yeah by default you know for any ice cream using ammonia there is a lot of regulations by default, which maybe inclined to kind of some of what you referred to. But for example, we have to have like staffing throughout the day, every day, as well as yearly training and whatnot for ammonia cases and such. And even I believe, I think it’s a class t maintenance room is required as well so there is a lot of those regulations that even with those things included into our cost analysis and saying we’re going to train these people every year and they’re going to get certified and we’re going to have our staffing our cost efficiency was still significantly better than CO2. And so kind of keeping those things in mind.

So Isaac had a question and I was going to go ahead and answer it. Yes ammonia did have a factor uh in our ethical score but we were able to mitigate a lot of that factor with the precautions that are already set forth in the standards that Meridian uses and Meridian uses a standard called Ashray and they also use the international plumbers standards as well. And what that basically means is, there’s sensors and there are detection systems every five feet of that facility. And when I say that I use that word very vaguely but we were able to mitigate that based on the standards. But if you looked at the ammonia and the CO2 systems, the CO2 system is so much more inefficient in Treasure Valley that we found it unethical to use more energy in other aspects. So yes we are more dangerous in a very controlled area. We are much more efficient and we’re saving energy in a lot of other ways. So it’s a call, it’s a lost game aspect. Hopefully that answers your question Isaac. If you have more you can always go unmuted or you can just continue sending questions through the chat board. That goes for everyone else as well.

In really thinking about you know the ethical analysis when it came to kind of decisions Bobby referred to earlier, you know our biggest ethical question was the type of chiller system we used and really we were looking at three to four main types of chillers and they were all basically around CO2 and ammonia and we found that the CO2 direct system was the most cost efficient but also the most dangerous. And we found that a CO2 or sorry an ammonia direct system was most cost efficient and the most dangerous and so we really you know hit that middle ground where we can do an ammonia indirect system, you know causing – allowing us to put a lot more safety precautions using less refrigerant in addition with the employees that are getting regularly trained and having a the costing mechanical room, being outside the facility, you know at that point we did our diligence on what that would look like ethically but between the cost savings and everything we were able to do by doing an indirect ammonia system.

Thanks for that Adam does anyone else have any questions for us?

So I had a couple more questions if nobody else does. We’ve got we got five more minutes. Talk to me about the condenser. What are you, how are you going to reject the heat? What does that look like?

So there’s actually, so from the condenser there’s a lot of pressure in there from the compressor has to be pumped up to uh to give it extra pressure so the CO2 can go through. And then after the condenser there’s actually extra pipes that the CO2 which would otherwise just be uh or not the CO2 but the heat from the CO2 would otherwise just be brought outside. It’s recirculated through pipes back into the rest of the facility. So we’re just able to use some of that heat which would otherwise be thrown away and recycle it back in and use that instead of natural gas or anything else to heat the rest of the facility.

So that was for the proposed CO2 so you’re going to use an ammonia system so that actually leads another question. Why was that recycling the heat not an option with the ammonia system but it is for the CO2 system?

So for ammonia the pressure is so low that you would actually have to add much more pressure and that waste heat is actually better off just being thrown outside whereas it’s actually just more cost effective to heat it in traditional methods whereas with CO2 because it requires those extreme pressures – 15 megapascals I believe it is whereas ammonia is more on the several hundred kilopascals if I remember right. That pressure can actually be used without needing any pumps or anything to recycle that heat throughout the system. Whereas ammonia is just such a low pressure that conventional means are more efficient.

Okay good good that makes that clear. So you have the ammonium system and you have a condenser so there’s actually several different styles of condensers of ways to get rid of that heat did you guys look into that about which what are the different versions and what were you gonna do?

Yeah so we actually opted for the the air cooled condenser. We found that that was more efficient than the the temperature doesn’t quite get hot enough throughout the year in Boise the average temperature stays fairly low so that was uh we found was actually the most efficient is to use the just the outside air to be able to cool down and condense the refrigerant.

And what are the other options if you don’t use air cooled?

There’s also water cooled, then there’s a variable condenser. So I think those three were the main ones we really looked into.

Okay, I have one last question then I’ll shut up. Did anyone talk to the folks who run the ice ice world out the city boise facility out by the airport?

Am I unmuted? I am. Okay sorry about that. Yes we did actually have a few responses from them and their biggest avenue that they gave us was making sure that your most heated wall was well insulated because in certain parts of the year half of their ice rink facility is slush. And another aspect they also had was just making sure that we were staying up to date on the technology because you can fall behind rather quickly. Yeah. But that was the big all of it gathered in one scoop.

Isaac had another question. I actually messaged him in a private chat because he had questions for me and he was wondering more about the CO technology. Is it so new? Because it’s so new, is there any research that will make it more viable? And the response to that all the CO2 systems are in Canada and further north. The best reason to let you know why it’s more efficient there is the coefficient of performance is much higher in those areas for CO2 because the temperature is much lower. As the temperature raises, you know to the American temperature which is about you know 70 to 100 degrees, CO2 coefficient performance goes down much much lower much more quickly. So that’s why the technology isn’t really viable in America at this moment.

Yeah and it really just like Matt was referring to, is that temperature is really the main determining factor. So if you live in those colder environments and get a better COP from it. In addition to that you can also be recycling the heat so there’s that added cost savings and you’re being efficient, as efficient as ammonia is. So it’s kind of a win-win in those areas. I think what it is is if you’re looking to put a facilitated ice rink in a metropolitan area or an area that the they have a normal winter summer seasonal aspect to it and not kind of cold all year round is when we really have to kind of dive in and explore other options over CO2.

Thanks for that response Adam. Did anyone else have any questions? I was going to leave the floor open for another minute or so uh and if not I think we can call this presentation good but uh we’re gonna stay here as long as needed we’re here to answer any questions that anyone may have.

And we do appreciate everyone joining our session today you know it was a fun project that we did over the last year and some interesting challenges popped up that I don’t think it normally happened during a senior project such as this one. So I want to thank you for joining us and kind of see what we have, what we’ve done so far.

Great well nice work gentlemen. I appreciate it. It was interesting. And good luck to you as you get out of here.

I appreciate it. Thank you doctor. Okay take care guys.