I’ll preface with my qualifications, so if a more qualified person comes along you can disregard me. I’m an engineer who has taken a few thermodynamics courses and has worked as an engineer for a hvac manufacturing plant. I’ve never done anything strictly related to geothermal, but I’ve read a decent bit about it (and watched Technology Connections’ video on the subject, it’s a good entry point)
You may want to call up a company who does geothermal cooling and see what options you have, they’ve gotten pretty creative on how to bury the cooling lines. (See the video mentioned before)
Going the route of just sticking a large water tank underground probably won’t do a ton. I expect that you will have a poor surface to volume ratio, which means poor heat transfer, which means you’ll saturate your thermal mass fairly quickly. What this may allow you to do is run your HVAC system during the night/morning when it’s much more efficient, and ‘charge’ your thermal mass for the hottest part of the day.
Assuming you use 300kg of water in a day, and you can get a 10°C delta, my very rough back of the napkin math says you’re only going to have about 3 kWh of cooling from just the cold water, which is a decent bit, but it’s not a ton. Best case scenario you cut your cooling needs by around 10-20%.
I’m too lazy to do the math of the heat exhange with the ground, but my bet would be you’re better off spending any money you have set aside for this on better insulation techniques and/or a proper geothermal cooling system.
Thanks, hoping that your back of the napkin math is in the correct ballpark, 10-20% lowering of cooling bills sounds very lucrative to me.
And I owe a clarification after reading your analysis since I’m not hoping to achieve any geothermal gains by heat transfer between water tank and ground. I’m assuming that the water will heat up as it cools the room down. But since fresh water is supplied periodically and this fresh water is relatively cool, it will keep the cooling cycle running. I will try to build the tank in shade and isolated from direct heat of the sun as far as possible.
As regards your point on the budget, i don’t think that two car radiators, some insulated tube and a small water pump will cost much, more so if I can run the pump off a small solar panel in the day time.
All said and done, if there is nothing in theory that advises me against trying this, i would like to give it a shot and document it so that someone else might learn from it.
Engineers describe heat transfer with a “heat transfer coefficient”, and the rate of heat transfer is this coefficient multiplied by the temperature difference. So you can calculate what the heat transfer coefficient must be by measuring room air temperature initially, water temperature initially, and then running your system for a little while and measuring the room temperature again. The smaller room area you can cool the more accurate this will be. You will need to look up heat capacity and density of air (easy to find), and the temperature change of the air with the volume of the room and the temperature change will together give you an amount of heat you removed from the air to the water. Simple!
While I have a background in science, this is not the specialization i chose and so almost all of it is almost Spanish (won’t say Greek, since at least I’ve heard of the words) to me.
I thank you for summarising the science of it though. It gives me enough keywords to start learning.
Well there is plenty of reason to not do it, but I’m assuming you’ve thought about what tampering with your water supply means (and that car radiators are not food safe, and could contain lead or other nasty metals). I think it goes without saying you’re also running the risk of leaks, a high water bill, and mornings without water if your system has issues.
I’d also like to cover my ass a little and do the typical engineer thing and remind you that an idealized number like this is never realized. You will have to account for losses due to inadvertent and incomplete heat transfer. But you may also get a higher reduction due to the ground heat exhange, which I am still too lazy to work out. ¯\(ツ)/¯
All of that said, I really hope you succeed at getting cheaper cooling and have fun doing it. There are houses which use water piped through concrete flooring to regulate temperature, so you’re not very far in uncharted territory. Doing big projects like this are also a really good way to learn a lot very quickly.
I also still highly recommend getting a quote for a reputable geothermal cooling system. If nothing else but to brag about how much you saved by DIYing
Thank you for your reply. It has given me the factors to consider and the terms to look for. I’m going to cross verify the values you have quoted and if it is indeed as bleak, I’ll just temper my expectations.
But I’m not giving up on it totally yet. What I’m still not sure is how geothermal cooling can provide more heat exchange as compared to the system I’m proposing. At most geothermal systems also only have a few tens on meters of piping underground.
You’re describing a fancoil supplied with cool, regularly replaced, municipal water (normally this water would be a fully closed loop cooled with an air source or ground source heat pump). Your energy needs will just be a circulation pump. You’ll probably notice a little cooling but it depends on how cold the water is, the surface area of the radiator, and the flow rate of the water. It has the advantage of being low maintenance so give it a shot and perhaps build it in a way you can access the components and improve / experiment over time.
Look into an approach / methodology called Passive House. Passive House focuses on making buildings that have near zero heating and cooling load. If you get the math right / design from scratch with this in mind you can make a Passive House in nearly any climate. Common modern single-family-home building techniques are generally not at all closely aligned with building a Passive House.
When trying to keep a house cool, here are the things I would focus on (in order of priority):
Reduce solar heating impacts: either place shade trees or awnings to block direct sun on the entire structure (or the windows at a minimum).
Build a highly-insulating enclosure (~R30 walls and ~R50 roof at a minimum, but you could push that further). If you are set on building with lumber you still can, you could building an offset double-stud wall filled with insulation, and of course an appropriate amount of exterior insulation a well. The goal in addition to insulation quantity is to reduce thermal bridging. Consider a “simple” house layout. Avoid too many corners / details / flourishes that add construction complexity.
Utilize free-cooling first: as your first stage of cooling, open large windows close to the ground and open clearstory windows in the roof / top of a stairwell or similar, it really depends on the layout of the home (and ideally the layout is design around this concept). This allows the heat to be drawn out naturally via convection. Include ceiling fans for comfort. This approach will work until outdoor air temperatures get quite high. Once free-cooling will not longer work
Once free-cooling will not longer be effective you can transition to mechanical cooling. Close all windows and cool your space either a high-efficiency air-source heat pump (and / or your free-cooling municipal water fan coil).
Similar to the design methodology to encourage natural air / heat flow out clearstory windows or “solar chimneys”, also consider just having higher ceilings where heat can pool but you won’t feel it. Your exhaust should pull from these areas.
Dedicated outdoor air system (DOAS): don’t design your mechanical ventilation system to cool using air (aside from the free-cooling described earlier). It’s inefficient. Hydronic heating and cooling (moving heat with water) is much more efficient. That means heat pumps for heating as well as cooling. Mechanical ventilation rates should be the bare minimum, just enough for fresh air but not for temperature control. Perhaps look at flow rates included in ASHRAE 62.1 or a standard more focused on residential homes. Also, your supply air can be separately ducted to each room (not a shared trunk), each being much smaller than what you see in a “normal” house, this gives more control for every single room.
ERV: of course you’ll want to install an energy recovery ventilator to capture what heat / “cold” you’ve worked to produce before instead of throwing it away along with your exhaust air.
For heating your domestic water, get a heat pump hot water heater (with tank). Instead of making heat it takes heat from the surrounding room and puts it into your domestic water tank. That means it “outputs cold” into the surrounding room, the opposite of a gas or electric resistance water heater.
Earth tubes: to naturally pre-condition your supply air by running it through the ground first. Another form of free-cooling but useful when the house is “buttoned up” because outdoor air temperatures are too high. This is when you’re only supplying minimum ventilation air.
Limit the things in the house that make heat. Efficient refrigerators / freezers (see energy star website), computers that are no more powerful than what you need, etc. Place these things in areas where the heat won’t bug you as much.
I can’t thank you enough for taking the time to write all of this. I have come across most of these concepts and have been considering them with respect to the options I have.
I’m trying to design the house considering the natural air flow and sun angles. There is a garden with trees on one side of my plot and I intend to make use of it while also planning for other sides. Currently I’m making house plans on my own and discussing with some people I know. This is helping me understand what we want/need, or not, in our home. At some point I’ll definitely take it up to the professionals. There used to be a community of floorplaners and home builders on Reddit but it was not much active.
Stone is the cheapest construction material in my area but it practically converts the house into a furnace unless the walls are very wide. I plan to avoid it at all costs. On my radar is a technology called EPS (Extended PolyStyrene) Core panels which are nothing but high density PolyStyrene with a galvanized steel mesh in it. It is supposed to be load bearing and good enough to build the roofs along with walls. It has been used in some countries at various levels of success though not in this exact form (with wire mesh). It is supposed to be highly non conductive in terms of heat and so good for maintaining inside temperatures with minimal cooling. Most of the material available online are either research papers or companies selling it, both of which only have the incentive to talk good things about it. I intend to go and meet people who have actually built using this technique and take their feedback before I commit to it.
As regards this pet idea of mine, I think the consensus in this discussion is that it will not cause much difference. But since it does not involve much effort/investment, I’m going to try it anyway.
Another cooling technology that has my attention is desiccant based cooling. That too has some research papers and a nice set of videos by Tech Ingredients (www.youtube.com/watch?v=5zW9_ztTiw8). It looks more daunting and more suited for humid regions/months.
I keep dreaming about a setup with evaporative coolers for dry spells and desiccant based thing for humid ones, assisted with this pet tech of mine.
I hope I’ll have the courage to implement these ideas finally.
Someone with more experience can correct me, but I doubt you’ll get enough energy transfer via the radiator in the house.
I think you’d get a lot more mileage out of an attic fan. Keeping the attic cooler during the day will slow the heating of the house.
You may also want to take a look at better roofing materials. There are roofing materials designed to reflect more of the sun’s energy as well as radiate what heat does get absorbed better than others.
I have been considering newer construction materials and the trouble is that most of the material available online is either research papers or companies selling it: both of which only talk good things about it.
I liked one such tech and intend to seek and meet people who are living in houses made using it. That should definitely assuage my doubts.
For those curious about the outcome: I added a red oak splint with dowels and two hose clamps and reassembled the chair on Sunday. So far everything’s held and there have been no more disturbing splintering noises.
I’m hoping to hold off on buying any new kitchen appliances until we renovate the kitchen, but who knows when we’ll get to that. The racks in this dishwasher definitely aren’t going to make it.
It’s not necessarily an issue with the brand, but rather the tier of the appliance. Builder’s grade appliances are just made way cheaper. Bottom tier options from all brands are bad. They’re bad enough that you can’t even buy them at most places. Only contractors can get them by ordering directly from the manufacturer.
Builder grade and contractor grade are interchangeable.
One thing to check is that the machine is leveled properly. If it’s not, the frame will flex and cause leaks.
I have a GE Quiet Power 2 dishwasher that I bought second hand 5+ years ago and that thing has been rock solid. All I’ve had to do is replace the plastic strainer on the bottom with a stainless steel one after it warped from being close to the heating element, and replace a rubber hose going to the pump after a mouse ate a hole in it.
I just put up an awning over our back deck. Now it’s time for modifications. I’m going to adjust how the straps connect for the fabric so it’s tighter and water runs off better. then I’m going to seam seal and put on some waterproofing spray.
After that, my daughter and I are building a padded bench for a window nook in her room. The design and measurements are done. Fabric and foam have been purchased. Actual work completed: zero.
Just got a bunch of stuff delivered to build my own hyperhdr tv backlight. Its a relatively small project, but im hoping itll have a huge impact on my viewing experience 😊
Ooo is there a guide you are following for this? I tried setting this up a few years back during covid and never could get it working right. I still think it was faulty hardware but I went through at least a half-dozen grabbers.
Yeah, there is a guide for the raspberry raspberrypi.com/…/raspberry-pi-tv-ambient-lightin…I donk know if hyperhdr would run on weaker, more readily available hardware than the pi 3. ive seen some YouTuber (dont remember who) use Hyperion with a Pico, but here was noticable delay. Since hyperhdr is a more optimised fork of hyperion intended for 4k content, the pico may be able to to run hyperhdr for 1080p content, but im not willing to take that risk. Also check what kind of power supplies you can even get. 5v 15a power supplies apparently don’t exist in Germany, so i had to use 30 led/meter strips instead of 60
Awesome, thanks! I may dive back into this project again since I would still really like to do it. I think I actually have a spare Pi 4 around here somewhere that I got for my 3d printers but ended up swapping that to a thin client. Appreciate it!
Thank you! The surfacing part was actually done mostly by hand because if a chicken and egg situation of making the inside components and adding the hinge, without throwing things off balance on the lathe. But after four prototypes, I definitely learned a lot!
We celebrated our 8th wedding anniversary yesterday, easy peasy 👍 The trick is simple, don’t marry someone who is an asshole. I certainly didn’t, and hope my wife feels the same way 😅
Trying to repair a spice grinder. After swearing a bunch and cutting up my fingers I gave up putting the original switch and safety lock and decided to cannibalize a new switch from a space heater that isn’t a POS.
Making progress on linen shorts. The belt fits, despite some unfortunate inaccuracies while attaching the waistband. Button hole and button are next. Or hemming…
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