Hi everyone - long post ahead with too many numbers.tl;dr - I'm thinking about the feasability of using well water for air conditioning. What do you all think of the concept, the trade-off of energy savings vs water waste, and any other design or practical considerations?Just to address the 'don't fix what ain't broke' sentiment - I enjoy projects like these. If it looks like there might be some benefit, I'll be glad to test it! This would also result in a much more simplified system.Pros - Power savings. Would also be nice not to have a large, loud AC unit outside. Don't have to deal with refrigerants or expensive AC unit maintenance.Cons - Lots of water needed, although I would hope to offset the majority of that with agricultural use. Also will have a lower cooling capacity and higher minimum temperature. Current AC has more capacity than needed, so reduction is okay as long as it isn't too low. The minimum air temperature could be a pro or a con - less cold air means fewer and slower temperature swings... Thinking about it, it's probably more of a pro, but I want to start somewhat pessimistic.Setup: I have a central HVAL system right now. Figure I would just cut open the duct just past the filter and stick a heat exchanger in. This seems like a good fit: https://ift.tt/2RpcWyT AC unit is a Trane XL 15i 4TTX5042A1000BA with a capacity of 42,000 BTUs/hour. The ZAS169NZA heat exchanger has the same BTU/hour capacity with a 30º F temperature differential. My well water is 55º F and target air temperature in summer is 78º F, so with a differential of only 23º max... let's say 30,000 BTUs/hour. I have a feeling that will still be more than enough for my home since it is very well insulated and sealed.How much water is that? Hoping to get the water to 70º F before discharge, so that's a 15º F change. Specific heat capacity of water is 4.18 joule/gram ºC. So with 15º F change, ~34.8 joules/gram. 30,000 BTUs/34.8 joules give about 908,000 grams or 240 gallons per hour. Agricultural needs are around 2,000 gallons/day for the hay field alone, a bit of which is offset by rain. I estimate the AC would run no more than 8 hours/day on the worst days, so that volume is usable. Watering would be done via buried lines, so evaporative losses would be minimized.I have no idea how much airflow would be needed to achieve that level of heat transfer, but I imagine the manufacturer's rating is for somewhat realistic levels.So how much electricity is that? Let's say 3.5 kW for the AC and... estimating around .4 kW for the well pump. Call it 3 hours run time/day for the AC and 6 for the water based system and that's a bit over a doller saved per day depending on energy rates. Selling the Trane would easily cover the upfront costs of the new system, so saving would be effective immediately. Obviously I wouldn't sell the current system until the new one is tested!Corrosion of the new system shouldn't be a big problem. Our water treatment system puts out water a bit purer than bottled water, although I'd probably bypass the softener and micron-level filter since extra sodium isn't good for the plants. The heat exchanger is so cheap that replacing it every 5-10 years would still be more than made up for in energy savings.Condensation collection... haven't completely figured that out. I'm concerned the airflow rate will be high enough to pick up and carry drops from the heat exchanger. Will probably figure that one out after installation unless you all have good ideas! There is a drain in the same room that it can end up going to - just need to figure out a good way to get it out of the duct. via /r/DIY https://ift.tt/2AGb4e7
