Using basement sump water to cool the house

[Piwoslaw]

I got this idea today - What if you moved the heat exchanger from the living room to the furnace duct? That way you could cool/dehumidify the whole house by turning on the furnace fan.
The up side is much simpler plumbing - the furnace is usually in the basement close to the sump, no need for the plumbing to go between floors.
On the other hand, there might not be enough cooling capacity in the sump loop, plus you may only want to cool one room instead of the house.

[AC_Hacker]

Originally Posted by Piwoslaw

That way you could cool/dehumidify the whole house by turning on the furnace fan.

In the 'Manifesto' thread, randen initially tried using water straight from his ground loop to cool his shop... it was an idea that many of us at EcoRenovator have had before... difference is he actually tried it.

He ran the ground water through a converted heater that already had a fan... He found that it did lower the temperature of his shop, but the perceived humidity detracted from the comfort.

So what was happening is that the warm air went through the HX and it's temperature was lowered. When that happened, the ability of the air to carry water was reduced and he had condensation in the HX (he did report that a lot of water was coming out). So the air that was cooler, now had a higher relative humidity than before and perspiration-cooling was not working on the surface of the skin as effectively as before.

I think that at this point, a very small amount of mechanical dehumidification would have been very effective, and would have produced a large amount of comfort, compared to the energy used.

-AC_Hacker

[Daox]

I'm a bit confused, if he is dehumidifying the air... why would that make it feel more humid?

I think my test worked great although with a limited btu output.

[AC_Hacker]

Originally Posted by Daox

I'm a bit confused, if he is dehumidifying the air... why would that make it feel more humid?

It has to do with the difference between relative humidity, and the total water content of air.

Relative humidity is the amount of humidity in air divided by the maximum amount of humidity that the air can hold.

Hot air can hold more water.

Cold air can hold less water.

Here is a psychrometric chart...

If we have cold air (36F for instance) that is at maybe at 60% RH (blue dot on chart above), and warm it up (70F for instance), it will still have the same amount of water in it... but now, because it is warm, it can hold more water... so it's relative humidity would be lower. So the new relative humidity is 20% RH (red dot on chart above). And this is why your Wisconsin winters are so dry when you are indoors and you don't have a humidifier.

So here is what I think is pretty close to randen's shop when he was running ground water (assume 60F) through his converted heater...

The air temp was around 94F and 60% RF (red dot on chart above), it ran through the converted heater and hit the coils which were around 60F (blue dot) and SOME of the humidity condensed out, but not all, and the air was mixed and cooled to about 84F (green dot)... so the air is cooler at about 84F, and it has less humidity, but its relative humidity is now 70% RH instead if 60% RH.

If he put it through mechanical dehumidification, it would be something like this...

The coils on mechanical dehumidifier would be about 18F and moisture in the air would freeze onto the coil (it's not on the chart, but the black dot is as close as I could get), it would also chill the air quite a bit and when mixed, it would look similar to the magenta dot.

So the ground source would certainly help a lot, but if you already have a high level of humidity in your summer air, a bit of mechanical dehumidification will work wonders.

-AC_Hacker

[Daox]

Alright, that kinda makes sense. What if he were to run the system longer though? Obviously at some point the ~50° water would no longer be cool enough to condense water so the dehumidifying would stop, and then you would just have the cooling effect. Obviously not as good as traditional A/C, but the power consumption of my setup was rediculously low and COP was very high.

[AC_Hacker]

Originally Posted by Daox

Alright, that kinda makes sense. What if he were to run the system longer though? Obviously at some point the ~50° water would no longer be cool enough to condense water so the dehumidifying would stop, and then you would just have the cooling effect. Obviously not as good as traditional A/C, but the power consumption of my setup was rediculously low and COP was very high.

Well, I wasn't there to see his setup, but even though he had "insulated well", it would have helped the situation if he had insulated more. So, you had the higher RH, and there was cooling, but not that much, and some heat was continuing to enter... As you can see from the pic above, he has plenty of reason for the RH to be high.

And so his ground loop had already done a lot of the 'heavy lifting' by lowering the air temperature, and at very little expense... if he had hacked a medium-sized dehumidifier, so that the evaporator coil was in the air path after his converted fan, and the condenser coil was outside of the building envelope, I think it would have made a large difference in comfort, with a modest energy penalty.

So, are you trying to use sump water to cool the basement, or the whole house? And what is the summer temp of your sump water, and how much of it (flow rate) do you have?

Randen used earth moving equipment and put in two trenches with about a bazillion feet of pipe in the ground... pretty major ground loop.

-AC_Hacker

[Daox]

These are all the results I have so far. My setup was only a test, but I would like to go forward with the idea and develop it. It really doesn't need to cool down the whole house, one room's worth would make me happy. As you can see below I didn't actually use the sump in the test. The sink and barrel were simply used as reservoires. The basement eventually cooled them off (albeit very slowly).

I have very high humidity but not that high of temperatures to deal with. If I can even get this to the point where it lowers the humidity a fair amount I'd probably be happy. Unfortunately, I didn't take humidity readings while doing the test.

I did later find out the 60F temperature was due to the basement being 60F. The ground water here is normally 55F.

Originally Posted by Daox

Well, I got my first results tonight. I only have it hooked up with one barrel atm and am using the downstairs sink instead of the sump. However, it is working. Here is a picture of the setup.


Here it is in the basement.




Here is the fan setup upstairs. Yes, it is quite ugly, but it is sealed pretty good against the radiator.






I can say it does work, but needs work. Here are the measurements I took.

Flow rate = .7 GPM / 42 GPH
Radiator temp at the bottom = 60F (not sure why its so warm)
Radiator temp at the top = 70F
Ambient = 81F

That gives me about 3500 BTU of output.

Now, the box fan I'm using is pulling 120W of power and the pump is pulling 25W, so combined we have 145W of power used (measured with a kill a watt). 1kWh is roughly 3400 BTU. So, it looks like I have a COP of around 7.0! Not bad at all IMO.

However, I would like to improve the design. Mainly, I'd like to increase the output. I think the first thing to look at is either a new fan, or improving the ridiculously poorly slapped together shroud. There really isn't that much air flowing through the radiator. So, I'm going to take a look at a squirrel cage fan I have off a wood furnace. I'm curious how much power it draws, but I know squirrel cage fans can hold more pressure than axial fans, and that should move more air through the radiator. I also need to deal with the condensation the unit makes.

Suggestions are welcome!

...


I just turned the system off for the night. After a few hours of operation, the bottom of the radiator was up to 65F and the top was up to 73F. This brings the BTUs down to ~2800. The water in the sink was up to 66F. I'll take a measurement again before turning it on tomorrow to see how much it cooled off.

[AC_Hacker]

Originally Posted by Daox

These are all the results I have so far. My setup was only a test, but I would like to go forward with the idea and develop it.

Your results look promising, you should continue. Might try a cardboard shroud & lots of duct tape for the testing.

How about getting your hands on a water heater tank and using that for your reservoir? That way you could get a bit of pre-heat for your DWH, too.

I don't know what your property is like, but my little yard is a full-canopy tree-filled situation. It makes it less than ideal for GSHP, but very nice for summer time air temperature moderation. In fact, my back yard, which is where the late noon sun would normally be beating down, is usually 8 to 10 degrees cooler than the front. Everybody that drops by my house in the summer remarks as to how cool and comfortable the house is, and they love the back yard.

Have you thought about, and do you have room for lots of trees on the south & west of your house?

Maybe pears & apples and a strategically-located grape arbor along the sunny side of the house.

It is very nice to sit in a comfortable chair, in the shade of a tree and eat fruit that you grew yourself.

Good COP, too.

-AC_Hacker

[Daox]

I'm pretty well set on the trees. I have a very tall maple off the southeast corner of the house. There is also a tree line that wraps around from the south to the west. It definitely keeps the temperature down in summer time. Its one of the reasons I liked the property. I get the same reaction when people come to my house in the summer. "Wow, you don't have air conditioning?"

A new shroud is definitely in order. However, I'm really thinking that when I put the next incarnation of this thing together I'll use a squirrel cage fan instead of an axial fan. I believe it'll move much more air through the heat exhanger. Even on high that box fan wasn't moving a lot of air through the radiator. I'm sure that was in part due to the poor quality shroud, but also just do to the design of an axial fan which simply can't hold pressure like a squirrel cage can. Its pretty evident that I need more airflow just by looking at the low flow rate and lack of temperature differential over the radiator input/output.

[AC_Hacker]

Originally Posted by Daox

...lack of temperature differential over the radiator input/
output.

I thought your delta-T was pretty good. Did you measure your water flow through your system?

How did you measure your water-in temp, and water-out temp?

And do you know how much cooling you will need?

Have you calculated how much water flow you'll need for that much cooling?

Gary has a home heating calculator, that looks like it's based on Manual-J. He might have a cooling version, or you might be able to trick it to calculate your cooling load.

Also, I don't know what your water cost is, but don't neglect the possibility of using a sprinkler on the roof with a timer that could turn it on briefly at fairly frequent intervals during the day. Evaporation really helps.

I suggested this to a convenience store owner. He tried it and said that it lowered his inside temp by 10F. Not too bad.

Your humidity is part of the problem and temperature is another part.

-AC