stone age simple geothermal
 

Ok, we all know the benefits of thermal mass and using the ground as a wonderful heat sink. Just for the sake of experimenting I have come up with an interesting experiment. I have a rather small house and I live alone so I think I can get away with this. I have posted an statement to all friends and family asking for donations of empty milk jugs. I will clean and fill these milk jugs with water to the tune of near 1000 or more of them hopefully. I will attempt to place them all throughout the house in areas out of the direct sunlight. My plan is to use them as thermal mass and see exactly how much I could offset the running of the AC in the summer. Now clearly I will still have to potentially run the AC the same amount to remove the heat but I have 3 plans for that.

Plan 1: If the nighttime low will cool enough to assist in cooling my thermal mass I can open my windows and blow all the heat back out.

Plan 2: This is wear the stone age part comes in, I could store a reserve of 200 or so milk jugs in the basement on the concrete floor where they would release their heat into the concrete and hopefully equalize around ground temp. I could manually make 100 trips or maybe 50 if I could devise a way to easily carry 2 in each hand. I would then rotate my thermal mass slowly and take 200 warm jugs down and bring 200 cool jugs back up.

Plan 3: I signed up for a program with my power company called power smart pricing where I will pay market price for power which changes by the hour. Last year on July 25th the cost of one KWH between 3 and 4 PM was over 11 cents however the cost of one KWH between 3 and 4 AM was at 2.5 cents. This means that I could pre-cool my thermal mass for around 25 percent of the price I might pay during the more demanding parts of the day.

Where are any large flaws anyone sees with this idea. In some ways it relies on me being single and young and especially cheap.

At least here it really is the humidity and not so much the heat, that is why we bought a window A/C unit, to dehumidify the house so it feels cooler, hauling milk jugs up from the basement will warm you up and working harder to go up and down the stairs will release humidity and heat in to the house, I'd sooner opt for sleeping in the basement.
I do like the thermal mass idea, but placing them in the shade in the house makes it sound like you have window shades open in the summer, limit the amount of direct light coming in the house and it will stay much cooler!

Personally I don't think you have the surface area nor the heat differential for the milk jugs to make a huge difference.

I am quoting from the First Book of Renovations, Chapter 1, Verse 8:

-AC

That really made me laugh. I agree pumps would make life much easier but I could certainly use the excercise! Making 50 trips up and down the stairs with 32 pounds would certainly help my fitness level which in term helps my body regulate temp on its own. Pumps also add significant cost and increase complexity a lot. With many small jugs I can quite easily manipulate where I put the mass to determine what might be the best location.

I also considered the single room air conditioner and may try that out but considering how small my house really is I have to think my central air is a bit more efficient with a few added benefits and added comfort for my labrador.

Everyones suggestions would clearly seem like the better idea but I am hoping to use this experiment to actually find which locations I could benefit from adding thermal mass when I do remodel. Passively heating and cooling would be ideal and I only suggested carrying jugs around just to put another dimension to my experiment.

Humans are about 20% efficient. If your trip down to the cellar is 3 meters and say you weigh 90 kg with your water, just the trips up are going to add
3*90*10*5 = 13,55 joules of heat to your home every trip.

That does not sound too bad, but remember that the heat load is added to your home in a short time. Well... first to YOU, and then to the home ;)

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Your comment in the OP that you would place the water away from direct sunlight suggests a better place to start for passive cooling: Shade those windows from the outside.

Scottorious,

Find a used waterbed. Don't use the heater. They do exactly what you are thinking of while providing another purpose also.

There are limitations to how much heat you can exchange with the basement. I tried this in July 2010 by running a ducted blower upstairs and gave up when my basement hit 75 degrees and the upstairs was still mid 80's and the house was muggy since the A/C wasn't running to remove the humidity, even the basement was uncomfortable. Eventually the concrete warms up and you lose the battle. I later decided to let the upstairs get to mid-80s on its own and sleep in the lower level of the house without using power to even out the temperatures. I then ran the A/C for 2 hours on my thermostat schedule at the coldest point of the night(but not colder than 60 degrees outdoors for the A/C's sake) and that took the humidity out of the air nicely and added just enough comfort to the house to where I had no complaints.

Your mileage may vary, I don't want to discourage your experiment but 1000 milk jugs would be tedious.

I think 50-100 trips up and down the stairs will have you wanting to stand in front of an air conditioner... Instead of all that consider this... use the jugs as stationary heat storage devices. Leave them down in the basement then use your furnace blower to move the heat down to the basement. In theory your AC won't have to work as hard and your heat sinks can "recharge" (release their heat) at night when it cools down.

Although 50-100 trips up and down stairs is great exercise. If that is one of the reasons then I say go for it. Just have some water in the tub or pool so you don't get overheated.

Glad you saw the intended humor...

But seriously, I think that what you are doing will be very useful to you, because you will come to deeply understand energy in a way that most people only think about.

No matter what the outcome of your efforts may be, your understanding will be priceless.

Keep going...

Best,

-AC

So, collectively everyone thinks manually moving water is a bad idea. So I'll just scratch that from my planning. Consider just leaving the jugs where they are and just using cheap electricity during the early morning hours to "recharge" my mass to at least slow down heat gain throughout the year. Saying I was going to put them in a shaded area was the wrong way to write that. I was just implying that they would not be in an area where they would be subject to heat gain via direct sunlight. The current shading of my house and windows is also being dealt with as well as insulation. If I was spending money on this project I would agree with others that maybe I should spend it elsewhere first but I hope that my large amount of containers required will be donated free from friends and family. Which means if it produces any beneficial results it's well worth it.

I remember a fellow telling me that he built a "wall of water" on his southern wall for the effect you are hoping for. The trick is to well shade the wall during the daytime in the summer.

The winter is a problem though, because the wall temp will tend towards the median daily temperature outside, and that is cooler than your home.

All in all, I am not a fan of thermal storage. I think PassivHaus design, meaning passive solar and cooling with excellent ventilation and air quality management is the way to go.

How deep in the ground is your basement? if it is much below grade, the milk jug mass would be best set up there, near the wall area below grade and on the floor. Water does an awesome job at leveling out air temperature, given enough surface area. With this type of arrangement, air could mingle between the individual jugs well. The jugs would be out of the sun, so heat gain wouldn't be an issue. They would draw the "cold" from the walls and floor well if not very insulated below grade, not so well if insulated well.

However, heat rises and cold falls, so you would need to move the cold air upstairs. Like razor said, you could move the air with your furnace blower by routing an existing duct to a low point on the level. I would suggest using a small fan (300 cfm or less) to suck air from the low point and exhaust it into your central air ductwork. When the central blower isn't running, the small blower would blend the cool air at the bottom with the warmer air above, drawing some warmer air from above slowly into the basement. When the central system kicks on, the cooler air in the ductwork would be the first to arrive where it is needed.

I have a setup like this running between the main level and the second story of my home. I rigged a HEPA air cleaner to the lone central vent upstairs so that it blows warm air down into the central ductwork below. Using this blower, along with my window a/c unit turned air source heat pump, I found that my heating needs are being met down to about 45F by the heat pump alone. This winter, I estimate I have saved over $1000 in natural gas bills at a cost of around $300 in electricity! Before adding the blower rig, the window heat pump did a good job of keeping the upstairs warm, but the gas heater still ran more than it needed to.

I like that idea, if I could create "columns of water" 5 feet tall that could sink any heat into the ground with plenty of space in between these columns. for air to freely go through. What would make an ideal column? Five gallon buckets would be easily sourced but the small contact between two buckets would be less than ideal.

Why don't you just live in the basement during the summer?

I think that's what any self respecting, simple, stone age human would do.

-AC

My dog(labrador) would hate being stuck in the basement all day(no windows to look out) and he would pretty much hate life in an 85 degree house. I am considering sleeping down there anyway. I am still holding to the idea that if I could use electricity at 3 am when its around 3 cents a KWH I could pre-cool my house and my thermal mass to cruise through peak demand times.

Perhaps, but then you would close off your home to the free cool outside air.

In my climate, I ventilate my house like crazy at night, and then put effort in preventing the house from heating up during the day.

Shade, insulation, shade :)

I'm just musing ....

You have a temp gradient in your home, from colder at the basement floor, to hotter at your ceiling.

How about a pipe with a fan in it that collects air from the basement floor and deposits it at the ceiling ? You might end up with a reverse chimney.

opening the windows is always an option if it looks like the temperature will drop to a comfortable level. I just wrapped up an experiment with a single gallon of water in a plastic jug. With my picaxe I logged data points at every minute for the last 3 hours to track how much heat a gallon might absorb just sitting in on a chair. The graph isn't perfect to read but the water started out at 48 degrees F which was from the tap. In 3 hours it rose in temperature to 58 degrees with the ambient air temp at a pretty consistent 68F. The other line that holds at 62F was a third temp probe that was just resting on the side of the jug. The probe in the water was roughly dead center of the jug. Raising 10 degrees in 3 hours absorbed 80 BTU. If this scaled up in the same manor that would be roughly 80,000 BTU in total or a bit over 26,000 BTU an hour. 26,000 BTU an hour seems like a nice help to the central air. I know in the summer it would be difficult to get water to 48 overnight. However I think the 20 degree temp difference could be achievable. Diurnal temp swings in July can be about 20 degrees. Just opening the windows late at night could feasibly remove a large portion of the heat boosted by the central air at off peak rates.

http://i1111.photobucket.com/albums/...allongraph.jpg

I don't think your notion of cooling at night is going to save you money. I am only reasoning here and relying on my experience at home, so I may be off ...

Homes have quite a bit of thermal mass themselves. If the home thermal mass has not reached low ambient temperature by the AM, it implies that there is unutilized mass, and adding more is not going to make a difference.

In my home, I open all the windows for night ventilation AND run a whole house fan, yet my home AM temperature is at least 5F above the outside night time nadir. As summer progresses my interior nadir temperature slowly rises. This is in part from mean temperatures rising, but it is also my home's thermal mass that slowly increases in temperature despite my best attempts to cool it down at night.

Now, you have a choice to cool the home thermal mass and water with AC, but as you run the AC more, the inside-outside temperature difference increases and thus so does the loss of energy to the outside.

This really sounds like a case where one hand gives, the other takes.
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I'll also mention that your quite optimistic scenario of collecting 80k releasable btu (net) in the 1000 gallons of water is equal to about 2.5 -3 kwh of electricity a day using the AC in the usual manner if the AC's COP is about 3.0.

I'll all for saving energy, but even I would draw the line at 1000 jugs of water in the house for 3 kwh a day :)

I use a program called power smart pricing (powersmartpricing.org) and I pay rates that vary greatly. As an example I used a day in the heatwave we had last year. june 29 had prices as low as 1.9 cents per KWH which occured for 3 hours during the early morning. During peak demands prices jumped to 9 cents per KWH. here is the link to that graph. Hourly Prices for Wednesday, December 31, 1969 : Power Smart Pricing /29/2012&display=table so if I could use thermal mass to shift when I use the AC....that is WHEN I use the A/C, I could save quite a bit of money. Even if I still ran the A/C the same amount or even a little more than I currently do but at hours that are off peak I could save money. I'm not trying to get anything for free just attempt to slow heat gain down so I can use the A/C at 3 am instead of 3 pm. Pre-cooling with a decent amount of mass sounds like a feasible way to make that happen.

Explain what is optimistic about my 80,000 BTU estimation. if 8 pounds raises 10 degrees in 3 hours why would 1000 pounds of water in 8 pound containers not raise 10 degrees?

The btu arithmetic is correct, that is not the problem.

Answer this: would the idea of night time cooling work absent the water ? If no, why not ?

I think pre-cooling my house could work to an extent. I guess I would say it seems like it might work as well as putting a 12 pack of cold coke into a cooler with no ice and expecting it to stay cold all day. I know that jugs of water are not ice but I'm only looking to cool my house 20ish degrees cooler than outside, not trying to achieve a frosty 35 degree soda. I'm in the beginning stages of planning a large scale experiment in one of my rooms to attempt to verify how well this might work.

That is not a helpful analogy.

We all know that e.g. in the winter, turning down the thermostat during the night saves energy, even though we use energy to heat the house right back up in the AM. Why ?

scottorious,

You're not sounding very caveman anymore.

However, you might not be able to 'pull the coolness' from the milk bottles filled with water as rapidly as you would like to. Experiments like this that were performed earlier used plastic soda pop bottles, which would give larger area per gallon.

If you did some experiments with an array of milk bottles, arranged as you expect to use them, and measured the rate of temperature decline... maybe plotting the temperatures against time, you'd begin to know if you could get the effect you expect.

If you actually did this, you would learn a lot... and if you shared your results in this forum, we'd all learn a lot.

If it didn't release coolness as fast as you wish, some smaller containers might be called for, like maybe a bunch of soda bottles. Or, going the other way, some plastic 50 gallon barrels (three would give you 1,252 pounds of water) with some pumps and fans and heat exchangers with larger areas than you could get with milk bottles.

BTW, have you searched through some of the alternative energy books that were written during the 1970's? There was a lot of work being done then, some very good, some not so much.

I went to our local really big used book store, and they have a very big section on alternative energy books, that are concerned with citizens taking energy issues into their own hands, similar to what you seem to be talking about doing.

One day, I actually went through all of the books, noting the number of alternative energy books that were published in each year. It was interesting to see that these kinds of books were remarkably absent before the 1973 oil embargo, and then a building tidal wave of books appeared and continued to grow until 1981, the year Ronald Reagan was elected, and then they rapidly declined to insignificance afterwards. But then again, beginning about 12 to 15 years ago, books on these topics began to reappear in numbers that approaching those from the 70's.

You might find some very interesting material there...

-AC

Here is my last attempt to explain why I think you will waste energy and money:

1. Cheap energy to cool the water -- good
2. (Albeit Cheap) energy to cool the *entire* thermal mass of the house to temperatures below what you would otherwise would, causing an increased gain of heat until the house equilibrates with the outside ambient -- not good.

Your approach requires (2.) to achieve (1.)

This will make more sense if you are familiar with Newton's law of heat transfer.

And they are....?

-AC

I understand what you are saying about cooling the mass past the point that I would normally cool my house. However My intention was to not cool the house to a point cooler than I would normally cool my house. I'll give my entire strategy in detail with hopes to clarify what I want to do or for someone to better explain where my plan is failing. I may be so far off on this but nobody has provided clear reasoning other than just saying it won't work.

for this example lets say I use 100 KWH a day to run the A/C and its spread out throughout the day. Its an effective plan however when the A/C wants to run the most will be when the power cost the most.

In my plan lets say I still use 100 KWH of energy in a 24 hour time frame. However instead of spreading that out all day I use most or all of it during the hours when electricity is the cheapest. Maybe my house will see larger swings in temperature but as I insulate more and more I hope to lessen that swing. and I can deal with the temp not being a constant 70. I also would have to make a great effort at reducing heat gain from cooking/showering.

In my head(and Ive been known to be way off before) whether I run the A/C all day or once a day it is still removing the same amount of heat, or no?

Another question, would running the A/C in the cooler temps of the night be more efficient for it? Last question, would running the A/C once for an hour be more efficient than running it for 3 20 minute periods over 2 hours. Basically is start up power enough that running the A/C fewer cycles but longer periods would amount to anything?

scottorious,

I'm wondering what other projects have you completed, and do you have any photographs of your work that you would like to share with the rest of us?

-AC

I have only owned my house for a year now so I have not had much time to ecomod it yet. I'm currently remodeling the entire second floor which is getting a lot of insulation, Wiring to accomodate DC lighting and an DC brushless motor driven fan in the bathroom for settings such as when you just want enough airflow to remove unwanted smells or when you need to quickly remove excess heat and humidity. I have only installed an on demand water heater. I have experimented with solar ovens quite a bit in the past and aeromodded a 99 saturn sc2 to get 52 mpg highway. Pictures for the saturn can be found on facebook(it has its own facebook page) the project was called ecorod. Currently I am working to improve the already fantastic fuel mileage of my 1986 honda elite 150. I built a picaxe controlled Power Meter that would give an update on power used every 15 seconds however since they changed out my meter for the new power smart pricing meter I have to recalibrate it and may not worry about it because my power bill will include a 24 hour breakdown. My house is on septic and used to have all the gray water flow into a cistern, past homeowners changed that and had some gray water flowing into the septic so I rerouted all gray water to use the cistern(I haven't devised any pump to use this water but I will). To lessen the load on the septic I built a nice little composting toilet(it stays outside and is only used when its warm enough to have your pants down outside). I guess I can't forget the bubble wrap on the windows this last winter. So I guess I'm not a supreme ecorenovator yet but as time and money allow I will certainly be working on projects.

Those all sound like really great efforts.

You should put some photos up for others to see.

Best,

-AC

"Another question, would running the A/C in the cooler temps of the night be more efficient for it? Last question, would running the A/C once for an hour be more efficient than running it for 3 20 minute periods over 2 hours. Basically is start up power enough that running the A/C fewer cycles but longer periods would amount to anything?"

Yes.

My air conditioner is a cheap not too efficienct unit from 1986. Here is the power input to my 22,000BTU/hr air conditioner for different outdoor temperature ranges when the sun isn't pointing at the unit. This includes the furnace blower as well as the compressor so you are seeing the whole system.
77-81+? 2400 watts
68-76 2300 watts
60-68 2200 watts
<60 2100 watts

Not only does the lower outdoor temperatures cause less power to be used by my unit, if I operate the air conditioner at colder than 60 degrees outside and the supply temperature isn't warmer than 80 degrees, the coil will freeze. I've frozen the lines going all the way back to the condenser twice from evaporator icing. If you aren't familiar with your system, try to keep it from running when it is cooler than 65 degrees outside. In my case I should install a freeze thermostat to the evaporator coil but I'm really not interested in throwing money away at trying to save an old inefficient unit that took the abuse twice already so I'm just more careful.

Basically what I'm saying is that the evaporator temperature is also lower along with lower power consumption which allows for better humidity removal. My supply registers have a measurably colder difference between indoor ambient to supply temperature. What this means is better efficiency.

Runtime, last summer I made sure to run my air conditioner 2 hours at the coldest point of the night as long as the temperature didn't have a threat of getting below 60 degrees outside. Dew points were extremely high last summer so opening the windows would actually increase the energy bill in the end and cause basement mold where I live. 20-30 minutes is just about the time that your evaporator is covered in water and is starting to drain off to remove the humidity from your house. In my case it is 30 minutes and I run the unit for 2 hours to try to remove as much moisture from the house as possible overnight so that the output of the unit when it is using more power is going to the sensible load(temperature) rather than the latent load(moisture removal).

266kwh $40.33 was my highest electric bill last year. Temperatures weren't where most people would like it but I was comfortable because I was able to sap the moisture from the air effectively and use a fan appropriately. This year the bills will be significantly higher because I'm not sharing the house with a picky female and I don't know if I can allow the evening temperature to rise enough to run a nightly 2 hour run without dropping the temperature below where I really want it. Her picky nature with the heat has this extreme conservationist a bit on edge over what will happen in the summer, hoping she's just a coldbaby.

Wow thanks for that info! Just another reason to figure out how to shift my peak load into the night hours.

Throwing money away?
 

This sounds like a clear case for improvement over the status quo. If you are not getting enough dehumidification with what you have now, swap out that cap tube for a TXV. At low outdoor temps, the unit will move much more latent heat outdoors and not freeze your evaporator. Your power consumption will rise slightly in proportion while the unit is running, but overall your run time will drop. At daytime temps, this option will pay for itself quickly by matching your indoor coil load with all that the condensor can supply, again reducing run time.

If you don't want to mess with the refrigerant circuit, increase the airflow at night. Just find a higher rated blower for your air handler and wire the speed taps to a 3-way light switch. The evap will not freeze up at night while the unit is running at max airflow. Depending on... blah blah detail detail ... the system will still pull just as much water out of the air at night while cooling the air like it is supposed to. This option will not save you as much money, but is easier to accomplish with less work involved. But you'll have to flip the switch for night speed.

Or you can always just go and buy a 20 seer ac unit and have someone else put it in. This may or may not be considered throwing away money since the unit would eventually pay for itself in energy savings. Especially if you went and bought a heat pump.

Scottorious,

You mentioned earlier that you have gray-water cistern on your property. I can't help but think that this would be a huge source of thermal mass for your idea. You may not need to load up your living space with tons of water to acheive your cooling needs during the day. Could you humor me and elaborate on the cistern?

Evaporative roof cooling...
 

Try putting a soaker hose along the ridge of your roof, and controlling the hose with a garden hose timer.

The idea is to let the evaporation do the cooling.

-AC

Ive considered the roof cooling.

The cistern is about 4 feed wide with the surface of the water at about 18 feet. I don't really know how deep it goes. Just an old brick cistern. Access at the top is only about 5 inches wide though. My house is on city water now but used to be on a well. I just got the well running again to use it to water my garden plus it looks really cool when its running. I don't know how anti-green this is but I had thought about using the pre-existing pump I have on the well to draw water out and use it for some type of cooling and discharge it into the cistern.

Now that sounds awesome! Use the cool well water as your source, pump it to your choice of air cooler in the basement, then run the somewhat warmed water upstairs to another air cooler. Discharge the warmed water to wherever it would be most useful. Set up the water pump to run off of your picaxe using temp differential control above an indoor temp setpoint.

just some sort of heat exchanger? radiator?

Yeah, that's a great way to look at it, kind of through an 'exergy' lens... using the appropriate heat energy (or in this case 'cool energy') at different steps as the energy cascades it's way down to an unusable entropy level.

That's a very sophisticated approach. There is even a book that is no longer easy to get called, "Low Temperature Heating and High Temperature Cooling REHVA Guidebook". You might be able to find it in libraries somewhere (inter-library loan). There was considerable work done on this front in Europe. A consortium called LowEx was formed and there was a broad effort to get other countries involved, including the US, who declined to get involved (you can lead a horse to water, but it's still a horse).

As far as I can see, the Europeans have internalized the lessons learned and are applying them to their approaches to heating & cooling.

I started a thread on EcoRenovator as a repository for information and discussion on this topic. The entry that has the most useful links to information is HERE.

I have searched for and found papers that detail 'Exergy Analysis' of heating and cooling projects. Most of the papers I have found at the time of my searches seem to come from Germany, Denmark, India and China.

Best,

-AC