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Using ONLY locally available materials, it is possible for ANY
homeowner to virtually eliminate their electric bills for air conditioning
FOREVER! If a million California homeowners would choose to individually
save this money, they would collectively reduce the electricity power load
on the California power grid by around 5,000 Megawatts! That reduction
might even help the electricity suppliers keep up with their demand!
A grass-roots solution for a problem that the honchos can't solve! This is a method for supplying plenty of cooled, de-humidified air for almost any house or many commercial buildings, WITHOUT needing to run an electricity-eating air conditioner compressor! Even better, it is fairly inexpensive to install and unbelievably environmentally friendly! All of the rooms of a house will be EXACTLY as comfortable as if that expensive compressor was running! The temperature, humidity and comfort level can even be regulated by the very same wall thermostat you already have! This system is extremely logical and actually very simple. It involves moving the house's air through large tubes (like tunnels) underground. In technical terms, these tubes are "heat exchangers" that use long-proven simple techniques to transfer heat FROM the house air INTO the cool deep soil. The temperature a few feet down in the ground is remarkably constant throughout the day and year. In Chicago, for example, that deep soil remains approximately 52°F, day and night, summer and winter. In the summer, the hot house air is blown through some underground tubes and that hot house air is cooled by contact with the cool (52°F) walls of the underground tubes. It turns out that it is also de-humidified, too! By the time the air has returned to the house, it is exactly the same as the cooled air that would have come out of a standard central air-conditioner. Air conditioning is accomplished without running an energy-expensive compressor, virtually eliminating air-conditioning expense. In the winter, there is even a bonus effect! Make-up air for the house, that might sometimes enter the house at -10°F, would enter the house at around 52°F instead! The heat load of the house can be significantly reduced, minimizing heating bills.
Have you ever been in a cave? Remember how cool it was, even if it was 90°F outside? The air inside that cave that you were breathing did not start out in the cave. Some winds had blown air in through some opening somewhere. Hot outside air that had gone into the cave had been cooled by the cool walls down there. That's pretty much what we are doing with this system. You can do this with locally available materials, which should cost on the scale of $500, in just a day or two, which would mostly be digging up and refilling trenches across your yard! If you hire a backhoe or trencher to do that might be another $500. Adding in some other expenses, the whole works might be do-able for well under $2,000. (These estimates depend on house size, climate and other factors, and are suggested as a ball-park estimates.) Simple, easy, fairly inexpensive, perfect!
By being able to entirely and continuously cool a house all summer, without a compressor running, many homes could save $1,000 or more, EVERY summer! This is certainly a great thing for the homeowner, who has to pay the bills, but it can also help many energy-strapped utility companies. If a substantial number of people would install this system, the summer electricity demand could be substantially reduced. Does it GET any better than this? You SAVE $1,000 (or more) every year for the rest of your life. You have a cooling system that is unbelievably environmentally friendly. AND you're helping the short-sighted electric companies past their crisis. And all this does not even cost an arm and a leg! (Maybe a toe or two!) There are a lot of variables, like home size, climate, soil type, etc, but a do-it-yourselfer could put the whole system in for under $1,000 for some houses. (Contractors would charge more, but probably still a manageable cost.)
Some Technical StuffThere is a somewhat similar energy source called Geothermal Energy. That is actually different from the energy involved in this device. Geothermal energy taps energy that is coming upwards from the hot center of the Earth. Most geothermal energy applications involved rather deep wells or a location near natural hot springs. This system does not need that energy source. Most of the energy involved in this system is actually solar energy, which had arrived months earlier and became stored in the mass of the earth, just a few feet deep.Each location on Earth has a certain annual energy input from the Sun and a certain energy loss from radiation (into space), conduction and convection. In the long-term, these two must be identical. The consequence of this is that Equatorial locations, which receive more solar energy during a year, must necessarily have a higher average ground temperature in order to radiate, conduct and convect that greater amount of incoming heat away. Polar regions have colder earth for the same reason. Very near the surface, the ground temperature is greatly affected by day and night and summer and winter, but even three feet deep, those effects are fairly minimal.
Here is a map of the US showing average deep soil/well temperatures.
Just find your location. The usual indoor design air temperature for
air conditioning is 76°F, so if the deep soil in your area is under
76°F, this approach will work! (Even if it was above, house air could
be substantially cooled, reducing the need for a central air conditioner
to work, STILL saving you a lot of money! |
This technology is being GIVEN away, FREE. Beginning in November,
2000, we have tried to get word out to California homeowners that this
option is available to each of them. It is given in the spirit of
one human being helping a neighbor. We are just trying to offer assistance for people who seem to be destined for some great adversity. We have heard that in San Diego, electric rates quadrupled in 2000. People who paid out $1000 the previous year for a summer of air conditioning are amazed at their recent bills for this and all following summers! And the electric companies have basically confirmed that blackouts will occur for up to ten years, until they have enough new power plants built. How could caring people NOT offer a solution where none other seems to be available? But the response has been amazing. The bulk of officials and politicians seem to assume that if this had any value, we would certainly be trying to make piles of money on it, so they are polite, but clearly cannot wait until the conversation is over. Some California homeowners DO seem to be aware of upcoming problems, but they seem to almost universally believe that there really IS no shortage and that this whole fiasco is some ploy on the part of the power companies to be allowed to charge them more. And, they have been conditioned so totally that government and executives can solve all of their problems, that most seem willing to patiently wait until government somehow bails them out of whatever "minor" inconveniences they will face. These problems ARE very real. Yes, they seem to have been made far worse by greedy businessmen and poor bureaucrats, but the problems exist. It seems certain that those many people are going to be very upset as they realize the severity of the problem, AND that they probably face similar or worse problems for the next nine years! At whatever point any homeowners feel the need to solve their own problems, on a grass roots level, this page should be here. It is, and forever will be, offered as a Public Service. No incredible breakthrough is presented here. The concepts have been known for many decades. I heard a rumor that even the ancient Romans "air conditioned" a few buildings with this method (but I doubt it!) Our primary contribution is to figure out a system that only costs on the order of one or two thousand dollars and which would probably save the homeowner more than that outlay every single year, forever. We have a single request. The fact that we are giving away a pretty thorough explanation of this system, does NOT mean that we are also offering unlimited free engineering expertise as well! For unusual houses, or ones in unusual locations, or in especially hot climates, it is sometimes prudent to have individual engineering calculations done, to ensure proper performance. Any local engineer (HVAC, civil, mechanical, chemical, etc) should be able to do the necessary calculations. If they (or you) wish, we can provide all the necessary technical equations (and examples) for such analysis, which anyone that understands algebra should be able to use. Alternatively, we could do such specialized engineering. In both of these cases, which are beyond our offer of this free technology, we think it is only fair to be paid for whatever additional time and effort would be used, so the end of this presentation includes such matters. We feel that most houses in most climates do NOT need this extra engineering effort! C.
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Actually, the temperatures shown here are nearly always very close to
the average of the summer and winter average temperatures. (In Chicago,
the average December temperature is 28°F and the average June temperature
is 72°F, which averages to 50°F, close to what this map shows.)
Heat-pumps are much more efficient than normal air conditioners, but they still have compressors that use a lot of expensive electricity. Because they use that compressor, they have the capability of sort of "multiplying" the heat/cool from the ground to even provide complete winter heating (for some climates), where our system, without a compressor, does not try to accomplish that. But we don't have to pay for electricity for that compressor, either!
Because any substantial volume of earth contains enormous amounts of heat/cool storage but the many soils are so poor at heat conduction, the AREA of the interface (tube wall) between the soil and the tube contents nearly always is the greatest limiting effect on short-term system performance. Ground-source heat pumps generally have very small diameter copper tubing, so the circumference and the outside surface area in direct contact with the soil is very limited. This tends to make ground-source heat pumps to often act like they have depleted the energy source very quickly. Fortunately, they have their compressor that just has to work harder, but can still continue to work during fairly severe depletion. And, in any case, energy from nearby soil replenishes the energy source in just a few hours.
Our approach is to use much larger diameter tubing underground, which greatly increases the contact area between the soil and the tubing surface. This total "area of contact" is one of the most important characteristics to design for in this system! Again, in more technical terms, heat exchange is proportional to the surface area of the heat exchanger. It determines the amount of heat (or coolness) that can be given to the house air that is flowing through the tubes, in other words, the Btu/hr rating of the system (or short-term performance). Even normal ground-source heat pumps would benefit from such a larger surface contact area, but their compressor allows designers to calculate very minimal systems, to keep their digging (and copper tubing) costs at a minimum.
Further, our approach is to divide the underground air passageway into several "parallel" paths, separated from each other by around six horizontal feet. This configuration takes into account the very slow soil heat conductance and yet allows using a FAR larger mass of soil to participate in this system, which determines the long-term performance of the system.
This drawing suggests a very compact arrangement. For example,
if a 50 by 50 foot area of yard was involved (about 1/16 acre), nine
parallel tubes (six feet apart, or 48 feet across all of them),
and each 50 feet in functioning length as shown, a total of around 450
feet of functional tube length would dissipate house heat into the
soil. You would probably need around double that amount of the sewer
pipe, since they are "bundled" together on their way to and
from the building, as the small cross sectional drawing shows.
Our drawing does not show the three identical tubes above the top of
the drawing This arrangement would represent a way of installing around
500 lineal feet of heat exchange surfaces in that fairly compact area
(counting the bundles). Such a configuration makes sure that one or another
of the tubes is within three feet of well over a million pounds of cool
soil. (Simple engineering calculations show that that much soil
represents over 10,000,000 Btus of cooling available!)
In case you're still skeptical, the "heat exchanger" arrangement we are describing has a coefficient U that is around 8 Btu/hr/square foot/° difference. If you look at ONE of our nine tubes, its circumference is around one foot and it is 50 feet long, so its area is around 50 square feet. If the house air begins at 90°F and the deep soil temperature is 53°F, there is 37°F difference. Multiplying these (8 * 50 * 37) gives an effective rating of 14,800 Btu/hr. That's ONE of our tubes, and there are nine of them! This suggests that the total system is capable of about 135,000 Btu/hr cooling, around four times as much as the normal house requires! Well, it could (almost) actually do that for a few minutes, but there are a number of factors that would get it down below 100,000 Btu/hr of cooling in under an hour and within a few hours to the 36,000 Btu/hr that we designed our "standard configuration" for.
Many larger houses and hot climates should probably have specific engineering done to determine that that is enough, but a million pounds of cool soil would often be sufficient for many houses and climates.
Basically, we are using modern engineering concepts to maximize the effectiveness of a natural phenomenon!
There are many variables involved, but many installations should be able to use 4" plastic PVC drain/sewer pipe, available at any local 'home' store. (Technical Comments). At around $3.50 per ten-foot length, the 900 feet of pipe mentioned above (90 lengths) and a bunch of elbows would only cost around $350. A trencher (sort of like a roto-tiller) can be rented for around $220 per day. The sections are light and easy to handle, and available almost everywhere. Standard PVC Cement glues the sections together. A do-it-yourselfer could do this amazingly inexpensively and quickly and easily!
| Materials List | |
|---|---|
| 90 pieces 4" PVC THINWALL sewer (ASTM D-3034) | ~$316 |
| 18 pieces compatible PVC sewer elbows (ASTM D-3034) | ~$36 |
| a lot of PVC cement | ~$15 |
| Rental of DitchWitch #1820 Trencher |
~$220 |
If you do a reasonable job of providing these three considerations, your system is bound to work!
(Alternate Configurations).
(More Technical Comments).
Virtually all of the heat that replenishes this system (or ground-source or water-source heat pumps, close cousins) originally began as solar energy that heated the surrounding fields, often months before. Virtually no actual "geothermal" heat is involved. However, there is no commonly accepted name for this process and we suspect that it will generally be thought of as geothermal heating/cooling. Oh, well!
This article is presented separately from the NorthWarm Solar System presentation because this feature could be added to most houses, either while they are being built or to be retrofitted later to existing houses. This sub-system can be fairly inexpensive and can be configured to completely eliminate ALL conventional summer air conditioning usage (and those huge electric bills!) In the winter, the same system significantly reduces home heating cost by reducing the necessary heat load. Yet another benefit is that recent Indoor Air Purity concerns can be addressed in a way that is not costly or wasteful. Finally, you cannot get much more environmentally friendly than this system!
Now, you probably already see the obvious logic of this system. Some fairly large-scale (expensive) systems have been occasionally installed for at least 30 years, and the relatively similar ground source heat pump system has been marketed for twenty years, so the concept is well proven. We are just presenting a low-cost version of it for residential use.
You are probably curious if the designer of this system uses it! Actually, his house has an unusual environment, and he uses a variation of this system which required much more design engineering but works even better! Here is a description of it.
This might lead you to believe that no planning or engineering is actually necessary! Well, technically, you would be right! If you chose to bury a mile-long culvert, it would certainly work excellently! However, most people couldn't afford to do that! They would want the shortest, most compact arrangement possible, both to fit under their yard and to minimize the digging expense.
The example described above will work extremely well for most medium-sized homes in moderate climates. So, no additional engineering is necessary for such applications! But, where soil is extremely dry, or the climate is extremely hot, or the house is especially large, prudent design might involved extra engineering. There is even often an alternative here, too! OK! You make 4' deep trenches and place the PVC tubing in the bottom of them. Instead of immediately filling in the entire trenches, for such applications, consider filling in ONE foot deep of fill in the trenches! THEN, get (cheap) 100 foot-long coils of black polyethylene 1/2" water line from the store, and drill LOTS of small holes in it! Make water connections to this set of water pipes, which are now one foot above the much bigger air tubes below. THEN fill in the trenches and re-plant your grass.
IF the system should ever seem to lose effectiveness in the future, it would generally be because the soil had gotten too dry down there, and the coolness was not able to flow through the soil to the tube. By briefly running some water through those water lines, you can quickly saturate the soil around the air tubes, TREMENDOUSLY increasing the system's performance (often by over a factor of EIGHT!) This "accessory" to this system is really inexpensive to add, and if your climate or soil dryness or house size is even moderately unusual, it might be a good idea to add this feature, even if it turns out that you never need it.
Let's say you have a moderate sized house in a moderate climate and you want to have 36,000 Btu/hr of cooling. Again, there are straightforward engineering conversion formulas that indicate that this is equivalent to about 10.5 Kilowatts of actual cooling effect. Our thoughtful government has provided us with a SEER (Seasonal Energy Efficiency Ratio) or COP (Coefficient of performance) for each air conditioning system sold. Let's say for a moment, that yours happens to have a SEER of 10 (about the same as a COP of 3.0). You would just divide the cooling load (36,000) by the SEER (10) to know how much electricity will actually be used (about 3.6 kW) of electricity. If you knew the COP instead, you would divide the cooling effect (10.5 kW) by the COP (3.0), or again, about 3.6 kW of electricity.
Most actual central air conditioners have a lower SEER than 10. Government studies have established that home central air conditioners average using 1.49 kW of electricity for the compressor and another 0.14 kW for fan motors, for each "ton" (12,000 Btu) of rating. Our example 36,000 Btu/hr system (3 tons) would therefore probably use about 4.9 kW of electricity (which calculates to a SEER of about 7.3).
Still with us? Now say you have a REALLY hot day, and the compressor ran virtually continuously for all 24 hours (not particularly good for the compressor!). You would have used up 4.9 * 24 or around 118 kWh of electricity that day. Look at your latest electric bill and it will tell you what each kWh costs you. Recently, electric rates have been going wild in many parts of the country. In an area where such rates are still relatively stable (Chicago), the rate is still only around 10 cents per kWh. One hundred eighteen kWh would therefore cost 118 * 0.10 or about $12. That single very hot day would have cost $12 in air conditioning. This is for a very moderate sized house and air conditioning system and for very reasonable priced electricity. We have shown you this logic here so you could figure these things out for YOUR system using electricity available to YOU.
You can probably now better understand the very large electric bills you receive during the summer. Twelve dollars for a hot day could easily account for $200 per month. Far more, for larger homes and for where electricity is more expensive than ten cents per kilowatt-hour.
The system described here does not involve any compressor! The only electricity necessary is for a fan or blower to push the house air through the underground tunnels! In many cases, this can be accomplished with a fan or blower that only uses 200 watts (0.2 kW) or less of electricity. In terms of SEER, the effective rating would be (36,000/200) around 180! That's nearly TWENTY TIMES as energy efficient as the very BEST heat pump or air conditioning system!
On that example very hot day described above, let's look at the figures. Instead of continuously using up 4.9 kW of electricity, this system only needs 0.2 kW. In 24 hours, that's 4.8 kWh. At the electricity cost mentioned above, that's $0.48 of electricity instead of $12.00! A full month of such heavy cooling would cost around $10 instead of over $200!
There are actually even some possibilities of eliminating the cost of running the fan, too, eliminating even that last $10 of monthly operating expense! However, it is such a minimal remaining expense, it is probably not worth even trying to do that!
This basically states the point of this system (regarding air conditioning). If you have a moderate sized house in a moderate climate and you have moderate electricity costs, you are STILL likely to sometimes save $200 in a single month! In a whole summer, this "eliminating" of the cost of air conditioning the house or building, might easily save you $1,000. Basically, whatever your total electric bills were last summer, inflated for the recent price hikes, THAT'S what you would save! And, that savings would be EVERY year, for the rest of your life! What a deal!
In areas where electricity costs have drastically risen in recent months, they are not likely to ever fall back to where they were. Using the logic presented above, you should be able to figure out approximately how much air conditioning will cost you. Or just check the electric bills from a previous year and multiply by how much the cost of electricity has multiplied. We are guessing that there are many millions of homeowners who are going to find it no longer possible to regularly air-condition their homes, just because of this tremendous increase in the cost of electricity. Well, that's a main reason we are presenting and offering this page! Each homeowner who would install this simple and obvious system, will virtually certainly save more than $1000 every summer (depending on climate, of course), forever! If a new monthly TOTAL cooling cost becomes only $10, even if it some day doubles, that's only $20!
And the coolest (pun intended) part of this is that all of the comfort in the house is PRECISELY identical to that when using conventional air conditioning. The temperature and humidity levels will be identical. Of course, you would not have a noisy condenser unit running outside your house, so if you like that sound, you're outa luck! All this, in a system is about as "natural" as you can get! And bonus $$$ savings in the winter!
If you live in ANY house, and YOU pay the electric bills, you must now see the exquisite logic of this system. It even has a bunch of additional bonus characteristics. For example, there is virtually NO chance of ever being charged for any repairs to the system, because there is virtually nothing that could ever break or fail or leak!
It seems to us that such homeowners will even be doing good things for society and the environment, as well as pocketing an extra $1,000+ each year. Consider California and its amazing energy woes, particularly electricity. Even during the winter, their electric companies and power grid have great difficulties in keeping up with electrical demand. Consider if a million California homeowners decide to save $1,000 each, every summer, with this type of system. They're smiling! LOTS of happy people in California! But consider this! If a million California homeowners are NOT taking 5 kW each from the power grid during the summer, that's a reduction of load on the power grid of FIVE THOUSAND MEGAWATTS! It is unclear if that would "solve" the lack of planning of California's electricity needs, but it would have to help!
(I know! I know! There are far too many exclamation marks in the previous paragraphs! But several of these concepts are pretty amazing! Huh?!)
Until around 1985, all houses built had significant infiltration (leakage), and many thousands of cubic feet of heated house air would therefore leak out each hour and be wasted. This added considerably to the heating load of the house or building, but it actually naturally assured indoor air purity because any air seldom actually remained in the house more than an hour or two.
After some energy shortages in the late 1970s and early 1980s, houses were built to be extremely tight, because of this very situation. Air infiltration was nearly eliminated. This significantly improved the energy efficiency of the house, but it caused the air in the house to not have any way of ever leaving. Where the smell of a cigar would have left in an hour or two in an older house, it is now trapped for days or even weeks in the new, tight house.
This situation eventually caused great concerns regarding Indoor Air Purity. (It is amazing that no one saw that coming!) Not because any more pollutants were being created in the house, but because the ones created in the house could never leave.
By the middle 1990s, Building Codes were starting to add new rules, where motorized house pressurization or similar schemes were required in new construction. In a darkly humorous sense, they are defeating the entire advantage accomplished by making the houses so very tight only a decade earlier! Some States' new (bad) rules require motorized exhausters, which is a truly bad idea because it causes the house to be at negative atmospheric pressure. That could cause fumes from a car in an attached garage to be sucked into the house, or smoke from a fireplace drawn out into the room as air is sucked down the chimney, or paint fumes from a workshop in the basement be pulled upstairs. Others of the new rules, slightly more thought through, require a similar motorized device to forcefully inject fresh outdoor air into the house. In principle, this is a far better idea, since it slightly pressurizes the house. If any leakage would happen associated with a garage, it would be (warmed) house air being forced out into the garage. Regarding a fireplace, warmed house air would be forced up the chimney. Wasteful of heat, but not a source of Indoor Air Pollution.
By the way, this pressurization approach has existed in most large commercial stores for decades. Did you ever notice how air whooshes (outward) past you as you enter the door of such a store? That's actually unnatural, because the "chimney effect" tends to always suck cold outdoor air INWARD near the ground and it leaks out through cracks high in a building. They pressurize such buildings for several reasons, but that is one of them. They don't want their incoming customers to have to feel an incoming blast of cold outdoor air!
Amazingly enough, some of the new laws realized that a motorized pressurizer couldn't actually push any new (clean) air into the house unless old (stale or polluted) air was able to get out, so they ALSO required PERMANENT openings in the house where this air could leave. Some new windows are built with these permanent openings in the frames! In principle, those windows act like they always remain slightly open! It's sort of hilarious! The older laws mandate super insulation and all that (costing the owner $$$) to make the house more energy efficient. These new laws require expensive motorized blowers and special windows and such which are designed to completely defeat the purpose of the original added expense, only at additional expense! Only in America!
Since some amount of outdoor air must then be brought into the house (by the motorized pressurizer), if the outdoor temperature is below zero, this adds greatly to the heating load for the house, and therefore to the cost of supplying heat for the house (unless you have our NorthWarm Solar Heating System!) In principle, you are bringing in extremely cold outside air and then having to add quite a bit of heat and humidity to it.
We're finally getting to our (winter) improvement! Assuming you have a large yard, imagine digging a trench about four feet deep all the way across the yard, and maybe then even zigzagging around the yard. In the bottom of this trench, place a large diameter pipe, and then fill the trench back in. At the one end of this pipe, have it pass through the basement wall and open into the basement or some other low part of the house. At the opposite end, (for primarily heating systems) have it elbow upwards so it sticks up out of the ground. (Make it decorative somehow!) (For primarily cooling systems, see below, and the descriptions earlier.)
The motorized pressurizer would be set up to draw its air through this long underground tube. When the air was first drawn into the tube at the outer end, that air might be below zero. But the ground several feet deep is much warmer. In the Chicago area, for example, it always stays around 52°F. As the air was drawn through the long tube, as long as the tube was designed and dimensioned properly, it would pick up heat from the surrounding pipe and soil. By the time the air arrived at the house, it would have been (naturally!) heated from the original 0°F to around 52°F. Only a minor amount of heating would then be necessary to raise it to the 70°F for the house, around 1/4 of that needed otherwise!
Any existing furnace/air conditioning system already has a 'Summer Fan' switch on the wall thermostat. This switch just turns on the blower, without activating the furnace or air-conditioner, and could easily be used to control the airflow through the underground tubes. Alternately, the 'Air Conditioning' switch position on the thermostat could be used. This would then allow the wall thermostat to automatically turn on and off the blower, blowing the house air through the underground tubes as necessary to maintain the desired temperature set on the thermostat! Absolutely automatic! Absolutely identical in usage to traditional air conditioning!
Interestingly enough, this system actually lets you control a comfort parameter that normal air conditioning does not, the Indoor Relative Humidity! Massive government tests have determined that the ideal summer indoor conditions are 76°F dry-bulb temperature (normal temperature) and 40% Indoor Relative Humidity (See any ASHRAE Handbook). Store bought air conditioners were designed to accomplish approximately the right IRH as a function of the temperature, so you don't actually have any control.
This system actually does (if you wish it!) Much of the foregoing discussion has mentioned air returning to the house at 52°F in our examples. This system can actually be used in that way, but that is usually not the ideal situation. If the air passing through the tube actually gets down to 52°F, then the great majority of its moisture content would condense out on the walls of the underground tubes. That's a desirable goal, but in this case, we're doing TOO good a job! Once that air comes out into the house and becomes warmed to the 76°F room temperature, it will only have around 13% IRH.
Since we would probably rather have the air come out with around 40% IRH (at 76°F), it turns out that it would be better to have the air exit the underground system (to the house) at 60°F. When this air heats up to 76°F, it will have 40% IRH. Going to the other extreme, if we arranged it so the air came out at 68°F, when that air warmed to 76°F, it would have an IRH of around 70% and it would feel muggy, even though the temperature was fine.
So, how would we control the IRH? By controlling how long a time that individual air molecules would be inside the tube system! There are elegant engineering ways of calculating what cfm of blower airflow would provide final airflow temperature, but it is generally easier and more accurate to just measure the (web-bulb) temperature as the air re-enters the house. If it is 60°F, then you will get 40% IRH. If it is higher or lower, just adjust the air flow cfm through the tube system so that the air returns at that saturation temperature. For locations where the ground temperature is higher than that 60°F, the house humidity level may be higher than desired, and, under some circumstances, a de-humidifier may be necessary in the house.
It might seem that changing the air flow through the tubes, and therefore the temperature that the air returns to the house, would affect the overall system Btu/hr capability. In general, it doesn't. A LOT of air coming back at 60°F has as much cooling effect as a lesser quantity of 52°F air. The actual coolness being delivered is proportional to the PRODUCT of cfm and temperature differential. So, with 80°F air entering the system, either 1000 cfm at 52°F or 1400 cfm at 60°F, would provide the same Btu/hr of cooling. Only the IRH would be different.
Depending on the climate of the house, it might be desirable to arrange this system for primarily or exclusively A/C operation, with little or no concern about winter benefits. In such a situation, there can be additional benefits from looping the tube around so that both ends of it come through the basement walls. Ducts (with dampers) would connect the existing furnace (or air handler) ducts to this path. At whatever point the wall thermostat would call for cooling, that existing blower would turn on and appropriate dampers would move so house air is blown through the underground tubes. This recirculating method has certain advantages, like better control of house humidity, better usage of the available cooling effects (higher net efficiency), and air filtration advantages. A pure recirculating system would have the potential of the super tight house Indoor Air Purity concerns. Probably the ideal solution for a primarily cooling installation would be a primarily recirculating system with a small intake provision for bringing in a little make-up air (for pressurizing the house).
With the underground tubing, the effect of all this is much more prominent, and the moisture that condenses out of the air is collected and removed, very much like a normal air conditioner does.
The basement floor has plenty of "interface area" so short-term performance can be great. If you live in a climate where air conditioning is only needed for a few hours at a time, you could probably get most of the benefits of air-conditioning from just recirculating your upstairs house air through the basement, using the existing house blower/air handler.
If there is NOT thermal insulation under the basement floor, then fairly simple engineering shows the short-term benefit you can get from this cool basement floor. Say the house is 25 feet by 40 feet, so the basement floor is 1,000 square feet. If the ground underneath it is at 52°F and the house air is at 80°F, then the "cooling effect" is seen to be (1,000) * 8 * (80-52) = 224,000 Btu/hr! That would be PLENTY to cool your house, and that's why recirculating the upstairs air through the basement can quickly cool the house. Just sending that air through the basement does not actually send all of that air right along the basement floor, so the "basement effect" winds up to be far less than 224,000 Btu/hr, but can definitely be the 36,000 Btu/hr of cooling that your house actually needs. (Keep in mind that this approach does NOT remove moisture from the house air, so there is no de-humidifying effect and a separate de-humidifier would be needed).
However, if your air conditioning needs are for more than a few hours at a time, this approach will soon lose its effect. Gradually, the soil underneath the basement floor will warm up. Since it is a finite volume of soil (basically the size of the house), once it has all warmed up, the cooling effect would be greatly reduced, until an extended period of non-use occurred so the soil could again cool back down. Anyone who has tried to cool their house in this way has noticed the reduction in cooling effect over time.
Any engineer can solve this Integral Kelvin equation to determine this effect. (By the way, this is the scariest of the equations involved! And the technical information package described below includes a table of solutions for this equation for all practical situations.) If a common, fairly dry, Midwestern soil is under the house, and if this example house needed continuous cooling of 36,000 Btu/hr, the solution shows that the soil a foot below the basement floor would have risen in temperature by 24°F after just one week! By then, the floor would have been at 76°F and there would have been no cooling effect at all. Even after just a couple days, the cooling ability would have dropped to about half, because the soil down there would have heated up to around 64°F. With a more moist common Midwest soil down there, the effect is only half as bad, with a decent cooling effect existing beyond a full week.
A simplistic engineering approach could also be used to roughly estimate long-term performance. In VERY approximate terms, the soil temperature one foot down would probably reflect the overall effect on TWO feet deep of soil down there. One thousand square feet, two feet deep is 2,000 cubic feet or about 200,000 pounds of soil. The specific heat of dry soil is around 0.3, so the heat capacity of this mass of soil is around 0.3 * 200,000 or 60,000 Btu/°F. If 60,000 Btus are put into that ground, it would rise an average of 1°F. Since we are talking about putting 36,000 Btu/hr down into that soil, that's 864,000 Btu/day. This implies that the soil would rise in temperature by around 14°F in a 24 hour period of operation, relatively in line with the solution of the more precise Integral Kelvin equation.
These comments are included to emphasize the need for calculating the long-term performance. Even though a basement floor starts out with incredible short-term cooling capability, in just a few days of use, that cooling effect gets depleted. Larger volumes of soil need to be involved when extended periods of cooling as necessary. The network of underground tubes accomplishes this.
We had mentioned using nine parallel 4" tubes for the total of about 120 square inches of area for the airflow. We have discovered that some people have read this page and decided to "improve" on it by making one very long air path of a single 4" pipe 500 or more feet long. Well, that WOULD actually work, but it would have a disadvantage. In the same way that firemen use a 3" diameter hose instead of a 1/2" garden hose (to carry far more water for putting out the fire), a single 4" air path would greatly limit the amount of air that could be cooled. True, it would be cooled really well, but there would be very little air flow through the tube, the effect being a lot like the garden hose trying to supply enough water to put out a big fire. The larger area is very important!
Now, if you have 6" pipe available to you locally, roughly five parallel tubes would be necessary to match the air flow through the nine 4" pipes. In that case, the air flow would be fine, but the total tube surface area would be slightly less (making the short-term system performance a little less, and the amount of soil within three feet of a tube would only be 5/9 as much, substantially reducing the long-term performance. So, before you go changing any major aspect of this system, make sure you understand all the consequences of that change!
Four inch PVC drain pipe should be available everywhere. Six inch is nearly as widely available.
Some people might fabricate a round or rectangular duct of some sort, and have the branch runs come off of it. A second similar possibility is to just have one large 15" diameter PVC Sewer Main duct come through the basement wall and have all nine separate 4" PVC pipes elbow branch off of it, but that requires more design engineering and probably more expensive large tubes.
If you want our help, we have two possible fees that could be charged. The first is a flat fee of $250, for a collection of equations, formulas, charts, (pre-calculated solutions of that Integral Kelvin equation!), and a lot of additional guidance regarding designing of the intake tube sizes, materials, lengths, and a bunch of general suggestions. If you happen to be or to know a thermodynamics engineer, he could probably do all this for you and you wouldn't have to pay us anything! The second is a flat fee of $500 (for a single-family, fairly normal residential house) which would involve US doing the design calculation work (of those equations and formulas) necessary. For this, we would need you to supply us with a variety of information, so we can take into consideration the size of the house, the climate it is in, its estimated heating/cooling load, the number of members of the family, the size and shape of the yard available, the type of soil, etc., to determine the diameters, configurations, patterns, depths, etc. of the components of this system. Many variables are sometimes involved, including mountains, lakes, forests, and other local conditions.
For many climates, the necessary yard area that would have to be dug up for this network of tubes might only be 50 feet square! If you followed our "basement" discussion, this area of tubes would involve a volume of soil of about 56 feet square (about 3,000 square feet) and about double the vertical depth of soil (because the basement "hole" is not there). In other words, even this moderate area of yard could be used to supply around SIX TIMES the long-term cooling effect of the basement floor example. (3,000 * 4 or 12,000 cubic feet of soil instead of 2,000). In hot climates, a larger area of yard would obviously be necessary.
If your application is anything other than a fairly standard single-family house with a large yard, our (second) fee will likely be higher. (The first fee would be the same, because the same basic equations and logic would still apply.) Unusual situations regarding house or yard, and ANY commercial or industrial application would be billed on a time-basis. The above-mentioned (second) fee is specified because we have a good idea of how much time would be involved for us to do the calculations for a normal house with a large yard.
In case you are concerned that we are talking about a (moderate) amount of money here, in a technology that is being given away for free, we hope the situation is obvious. We don't want to LOSE money as a result of this offer. It wouldn't seem fair for people to ask for free engineering as well, because it is fairly time consuming to do all of the necessary calculations and engineering. We encourage you to find a local civil engineer who could equally do the math. We are making this engineering offer because we have already done a LOT of research and collected all the useful stuff in that collection of information. We are hoping that a $250 fee would not cause a hardship on anyone for that information.
You know how house gutters slightly slope, so they drain? Just an inch or two in a ten-foot length? That should be done for these underground tubes. NO corrugated tubing should be used, because it would trap such condensed moisture in lots of little puddles. The tubing should have a smooth interior. Since it is relatively hard to confirm that a minimal slope has no low spots (far harder than for gutters), it is generally a good idea to provide a somewhat greater slope than normally used in house gutters. The slope should probably go downhill along the direction of the airflow, so the moving air would tend to push the water along. This could terminate in a central condensate collection point in the tube system, or it could continue all the way back into the house, where the water would be collected and then sent down a sewer drain. These considerations would eliminate any danger of a puddling or bacteria problem in the tube system.
NOTE: Before you go digging, make absolutely sure that no easements are across the property. You DEFINITELY do not want to dig into high voltage electrical cables or gas mains or water mains!
But, let's say you don't get our help and you happen to not bury enough pipe. Well, even in that case, you come out fine, because the system would do much of the air conditioning (depending on how well you planned the piping) and will greatly reduce your air conditioning bills anyway. So, even if you somewhat mess up by not doing any preliminary engineering, you still win!
In nearly all cases, the existing furnace blower or air handler, and wall thermostat could be used, so there's virtually nothing necessary except for the tubing and the trenching. And there's nothing bizarre about operating the system, either, since the normal wall thermostat would be used exactly as before.
We believe this to be a feature that nearly all houses could benefit from. Considering recent large price hikes for electricity and natural gas, we felt it appropriate to present it as a separate system, where it has always been considered a relatively minor part of the full NorthWarm Solar Heating System.
Even if you have already paid for an existing central air conditioner, this intake arrangement could quickly pay for itself in combined heating and cooling savings. Just do the cost calculations suggested above to find out what YOU might save. And, even if you happen to be in a climate, like Miami, where you might feel it too involved and costly to bury all the necessary piping for an entire system, any size system that you would install would greatly reduce your air conditioning electricity costs.
Since we're basically telling you how to generally do this, for free, we feel it's fair to ask a single favor in return. If you happen to live in or near California, and you install this system, please call ANY local newspaper, radio or TV reporter to look at what you did. We don't really care if we get any credit in the matter, but it's important to get the word out to all California homeowners that they each have a way to greatly reduce their summer electric bills. And, if enough of them actually do that, collectively we might help avert a big summer problem of blackouts out there. In the process of this, you might even get yourself on TV, if that's important to you! It might seem surprising, but WE don't want any publicity from this effort at trying to help California deal with a big problem. We just believe that we have a grass-roots solution for it, and that people should help one another.
Performance and storage will be extremely great. The VERY large collector area and storage space make it certain that NO back-up heat will EVER be necessary for heating the house.
Performance and storage will be great, but the necessarily smaller collector area and storage space make it possible that back-up heat will sometimes be necessary for heating the house.
This liquid-based version has potentially higher installation costs than either of the air-based systems above. It would certainly involve much more maintenance time and cost. It also has all the advantages and disadvantages of a water-based system.
It has very good performance but has intrinsically less performance ability than any of the other three NorthWarm versions. It is a low-tech approach to solar heating.