Now consider that the deep soil (eight feet or 2.5 meters deep) in a Chicago-like climate NEVER drops below around 52°F or 11°C. We have invented very simple hollow-tube devices which NATURALLY BRINGS that 52°F deep-soil warmth up to the underside or your sidewalk or driveway or garage floor, the ThermoSiphon Version of which does not have ANY moving parts and does not need any motors or pumps or anything else, because that device works on a NATURAL process called ThermoSiphon.
Our devices, SnowMelt and IceMelt, quickly and CONTINUOUSLY causes the pavement above our ThermoSiphon device to ALWAYS be at around a 45°F or 7°C temperature! The cold air above the pavement is certainly cooling it down from the top, but the nice supply of 52°F air underneath the pavement is also warming it! Any ice that might have been on the pavement HAS TO MELT and flow away as water. The same thing happens with any snow that happened to have been there. And when another rainstorm or snowstorm dumps more precipitation onto that rather warm pavement, IT INSTANTLY MELTS and no snow could ever accumulate and no ice could ever form! (The photo is of one of our devices being lowered into a tractor-augured hole in Idaho in 2010.)
NO SHOVELING SNOW!
Have you also realized that in your 'unheated garage', a 52°F warm concrete floor would always make your vehicles start easily and be decently warm when you get into them? It is WONDERFUL!
You may have noticed that Manhole Covers NEVER have any snow or ice on them, actually for nearly the same reason, but in a less sophisticated way! The deep walls of sewers down there are warm due to the warm deep soil around them, and ThermoSiphoning occurs to the air inside the sewer mains, which heats the Manhole Covers from underneath.
As air inside our (sealed) device is warmed up to around 52°F or 11°C down near eight-feet deep, that warmer air becomes less dense and it rises (red arrows in our drawing). And the air that had been near the top of the device is pushed down through an interior passageway back down to the bottom (the blue arrows in our drawing). That is a description of how ThermoSiphon works! It is all a NATURAL process!
This results in our (naturally) HEATING the pavement directly above our ThermoSiphon device so it is never cooler than around 45°F or 7°C in winter (near Chicago). It is actually comfortable to walk barefoot on this nicely warmed pavement, and I even ate a picnic lunch while sitting on such a sidewalk during a Winter snowstorm while the outdoor air temperature was around 25°F or -4°C! (although I admit that I had a plastic tarp over me at the time!)
Under sidewalks, under driveways, under streets and highways, under concrete garage floors, this is an amazingly simple and inexpensive way of ensuring that no one slips on ice and sues you! It also eliminates the need to shovel snow (which I have personally always hated to do!).
Imagine a downtown retail store area, where all the sidewalks had these devices installed, and all parking lots and streets also have them. There would never again be any cost regarding snow removal or the scraping or salting of ice! More customers??? I think it is possible, along with those reductions of winter costs. It also would eliminate the need for a lot of Road Salt that damages the environment and many plants.
There is even a bonus advantage from our devices! In hot summer, a black asphalt parking lot can get too hot to walk on. But even in Summer, the deep soil is still at around 52°F or 11°C (for a Chicago-like climate). The Thermosiphon actually works backwards in Summer, to where the effect is that the hot Summer parking lot pavement is actually COOLED by that ThermoSiphoning to the deep soil which is around 52°F or 11°C!
It ARTIFICIALLY uses warm air which was produced by a house central furnace (or, in our case, our 100% totally solar heated house, which provided warm air to be blown through shallow horizontal passageways just below a sidewalk or driveway or a garage floor.
BEFORE a sidewalk or driveway or garage slab is poured or paved, a series of closely spaced (one foot spacing is my choice) pattern of parallel plastic 4" (ABS) tubes, which are sold as Field Tiles. I like them because they only cost about 1/3 of what the similar 4" PVC pipe costs, where both perform nearly identically for our purpose. So we use a standard furnace blower and an air damper to be able to send heated air through such passageways, which warms the sidewalk, driveway or garage floor from underneath. At the end of the sidewalk which is near the house, a plenum is made (which can even be poured concrete for simplicity) and a buried and INSULATED warm air duct from the house feeds it, through a DAMPER which can shut it off to not waste house heat. The opposite ends of the tubes also go into a plenum which feeds a short decorative duct which sticks about a foot above the ground nearby and has a screened cover. This last is necessary to keep the tubes from filling with rainwater and vermin, and which allows the used house air to exit, allowing room for new warm air to enter the pipes.
(That earlier blower-driven system was NOT a ThermoSiphon system!)
You have already figured out the rest! A cold sidewalk which is covered by ice or snow at 32°F or 0°C or lower normally needs YOU (or a teenaged son!) to go out to shovel it clear. But by opening that damper, your house heating system, whether a conventional furnace, an HG 3a device or the NorthWarm Version 1 100% Totally Solar Heated house (heat from storage in that case) can feed warm air through those tubes. That warms the ground around the tubes. Heat naturally rises so the concrete sidewalk immediately above it quickly warms up. Getting the concrete up to 50°F or 10°C is easy and does not take too much house heat. The snow and ice laying on top of that nicely warm concrete sidewalk or driveway quickly melts!
In fact, if you plan ahead maybe an hour, you can have the sidewalk ALREADY at 50°F as the snow or sleet begins to fall, and it IMMEDIATELY MELTS and your sidewalk REMAINS CLEAR of any snow or ice. Not even just avoiding having to shovel snow, but absolutely ice-free sidewalks that NO visitor might slip and fall on and sue you!
This invention was first developed in 1980, with the Thermosiphon version of it added in November 2010. This presentation was first placed on the Internet in April 2011. I do NOT give any manufacturer any authorization to use either application of this invention unless I have given written authorization, as related to a contractual arrangement.
Pretty cool, huh? Or WARM, actually!
Late in 2010, I discovered what I consider an even better version of this! NO HEAT FROM THE HOUSE IS EVEN NECESSARY OR WASTED!
NO ducts from the house heating system here! Find some nearby Farmer who has a tractor with a posthole auger on it, and with compliments, possibly money and possibly beer, have him drive his tractor to your building site! He would bore what seem like a LOT of postholes, in either two or three rows (depending on how wide your sidewalk is) and every foot or two along its whole length.
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Because YOU are then going do DROP into each of those holes a VERY SIMPLE and VERY CHEAP "thermosiphon heat exchanger" into each of them, and cover them all up with a few inches of dirt or gravel ballast for the sidewalk. By the time the concrete truck shows up to pour the sidewalk, they would never know that there is anything underneath!
Why do this?
Have you figured it out? In a climate like Chicago's, the DEEP SOIL never drops to below about 52°F or 11°C during the winter. You are going to make simple HOLLOW TUBES with END CAPS to drop into each hole. There is a natural process called ThermoSiphoning where WARM air or water RISES and COOLER air or water SINKS. Inside each tube, the air near the bottom is HEATED by the 52°F or 11°C soil surrounding the tube (WARM) and up near the top the air inside the tube is COOLED by the winter cold surface temperatures (COOL), including the concrete sidewalk.
Thermosiphon immediately occurs (just like in the pot of water you boil on a kitchen stove) and the net effect is that HEAT from the deep 52°F soil gets moved to warming air inside the top of the tube, and therefore the soil and concrete sidewalk above it.
The result of this is that YOUR SIDEWALK then ALWAYS stays near 52°F through the entire winter, constantly and continuously being warmed from the Earth's enormous supply of heat!
You then have that situation of the pre-heated sidewalk, where snow or sleet immediately melts as it falls! Snow accumulates on your yard on both sides, and can become 12" inches deep, but the sidewalk will ALWAYS remain snow-less and ice-less!
Details? For a sidewalk, in anywhere except northern Alaska, Siberia or Antarctica, 4" PVC or iron pipe seems to be fine. Iron pipe end caps cause that choice to be a little more expensive, but if you have a welding machine, you could weld on end disks of steel onto the pipe. In fact, the TOP end cap might then be an 8" square plate of 1/4" plate steel, to create an even LARGER SURFACE of the warmth to more widely warm the sidewalk which will later be above it.
How deep, or equivalently, how long should these things be? Certainly THREE FEET is a minimal, even for a sidewalk. No more than four or five feet for any sidewalk application. The Tractor posthole borer (without some simple modifications to go deeper) can commonly only bore holes which are three or four feet deep, so you might check with the Farmer first before making them.
IF you want to enhance the performance, you could complicate things a bit. It turns out that this simple arrangement causes ThermoSiphoning that is somewhat disorganized inside the tubes, and therefore less of overall efficiency in transferring heat up to the sidewalk. For a sidewalk, I do NOT see the following improvement to be necessary! But a smaller tube (2" diameter PVC or iron pipe) can be rigidly installed INSIDE each tube, centered and about four or six inches SHORTER than the main tube is (as shown in the drawing above). This allows the heated air to rise through an OUTER passageway, where it is also exposed to sidewalls which are somewhat warm, and the cool air at the top sinks back down through the smaller central tube passageway. ThermoSiphoning works a LOT better this way! That inner tube must NOT go all the way to either the top or bottom, and needs to be HUNG to permit easy and smooth airflow.
To make a driveway self-melting, I recommend LARGER tubes, 8" in diameter and WITH the central smaller tube inside, AND longer, and therefore deeper. The posthole auger needs to then have that modification to be able to bore deeper holes. And the holes can be a little farther apart, where I consider a grid of holes two feet apart in both directions should be fine. I consider a MINIMUM of 5 feet and an ideal 8 feet deep to be the goal. PVC is not available at reasonable prices in such diameter, so I recommend buying several 20-foot lengths of the 8" iron pipe or steel tubing (at least 1/4" thick) and using welding equipment to cut them to the lengths you will need and then weld on the two end plates of 1/4" steel, again with the top one being optionally square and larger, maybe 16" square. You will then also be able to weld in either an inner steel tube or at least support brackets to support an inner 4" PVC plastic tube.
Under a new garage concrete slab floor, the driveway guidelines are fine. The garage would then always stay at 52°F or 11°C, so the engine will always start immediately and you will get into a car which is NOT horribly cold!
There ARE other applications of this which are obvious. EVERY (northern) city now spends MILLIONS OF DOLLARS to buy a bunch of snowplows to mount on the city's trucks and for the wages of the snowplow drivers and for many tons of road salt that they use up every winter to try to melt fallen snow. So each town and city can obviously SAVE MILLIONS OF DOLLARS normally spent that way (every year) by adding this snow-melting feature under every street as it is scheduled to be repaved.
By the way, since the PAVEMENT is then NEVER SUBJECTED TO FREEZING TEMPERATURES, NO POTHOLES COULD EVER FORM (which are not only ugly and dangerous but expensive to fill in and re-patch). And the LIFE OF THE PAVEMENT would certainly be MANY YEARS LONGER, meaning millions of dollars which now has to be budgeted for annual road repairs might be far less!
The City Attorney of every town and city should also love this, as there would then be VERY FEW VEHICLE ACCIDENTS since cars and trucks would not be sliding around on snow or ice covered roads! That simply cannot occur!
Those same City Attorneys should love the fact that pedestrians would be SUING THE TOWN LESS OFTEN, as they would not be falling due to slipping on icy public sidewalks or when crossing public roads!
Continuing this theme, city store owners would love being able to have a parking lot for their customers which would NEVER HAVE ANY SNOW OR ICE! MORE customers, eh? And walking FROM that ice-free parking spot to their store? Ice-free sidewalks, of course!
Not bad for a system which is invisible, requires NO fossil fuels ever, and which should last for more than 40 years, and which is not horribly expensive to install in the first place!
State Highway Departments might also want to try to make ice-free highways, although their situation might not be cost effective due to having to modify so many miles of roads.
But AIRPORTS definitely SHOULD install this IMMEDIATELY for their runways. Imagine an airliner being able to land on a PERFECTLY CLEAR AND DRY RUNWAY, even in a snowstorm or hailstorm or sleet storm? Only a 50-foot-width of the runway probably needs to be modified, but most of its length should be. Yes, that might be a fairly expensive project, BUT IT ONLY EVER HAS TO BE DONE ONCE in the airport's lifetime! The devices for an airport runway should be sturdier than I have otherwise described above.
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C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago