"GEOTHERM.PRO" LLC - components for geothermal heat pumps

Geothermal probes


What are geothermal probes for?
Geothermal probes collect heat deep in the earth and transfer it to a geothermal heat pump, which heats the house with this heat.
The geothermal probe is immersed in a pre-drilled geothermal well. Due to its vertical positioning, the probe collects more heat from a unit of land area than a horizontal geothermal field.

How are our geothermal probes better than others??
We have developed and apply a unique technology of dipping geothermal probes with drill rods into a borehole of minimum diameter, and without a special expensive load.

It is possible to pump the squeeze mixture into the borehole through the drill rods, immediately after the geosonde is inserted. This significantly saves work time and eliminates a special pipe for pumping the squeeze mixture. 
Our U-turns and Y-turns have long spigots. If for some reason the welding of the bends to the pipe fails - the installer can cut out the damaged piece, and repeat the welding.
The price of our geothermal probes is lower than that of other probes. The main component of a geothermal probe is a polyethylene pipe. We are confident that it is possible to buy a quality polyethylene pipe produced locally instead of carrying the same one hundreds or thousands of kilometers. 
In addition to polyethylene pipe to assemble a geothermal probe will need U-turns, and possibly Y-turns. All components are reliable and time-tested - since 2010 we produce them, use them ourselves and sell them to our colleagues.
Welding of polyethylene pipes with thermistor couplings is simple, it's been assembling underground gas distribution networks for decades.
Regardless of whether the probe is purchased ready-made or assembled on site, the geothermal probe is tested before it is plunged into the borehole.
In the depth of the ground, unexpected obstacles are occasionally encountered that significantly increase the cost of drilling, such as rock, pebble layer or sandstone. To save the budget, you have to reduce the depth of the well, and at the same time increase the number of wells. It is risky to buy a geothermal probe in advance, it is better to make it quickly after drilling, on site, based on the actual depth of the well and the length of the connections.

What is the depth and diameter of geothermal wells?
The depth of drilling geothermal wells is recommended by the heat pump installer after discussing the geology with the driller. The shallower the depth of wells - the lower the price of drilling one meter well, but the greater the number of wells, the length of trenches to connect the wells, and more expensive collector. The usual depth of geothermal wells is 50 ... 120 meters.
The diameter of geothermal wells 90 ... 180 mm, and depends on the design and method of immersion probes.

Tamponage of geothermal wells. Why?
Wells are plugged with a mixture of bentonite clay, cement, sand and water. After the well is filled, the tamponage slurry hardens.
Tamponage of geothermal wells solves four problems:
1. environmental - it blocks the flow of water between underground horizons;
2. stability - without tamponage the ground around the well may subside;
3. energy efficiency - plugging removes air pockets in the well, contains the maximum amount of solids and the minimum percentage of water, ensures good heat transfer between the geothermal probe and the ground;
4. safe pressure in the geothermal probe installed in the ground with a very low water table.

What is the pressure in the geothermal probe? How does the probe withstand the pressure deep in the ground?
The pressure in a geothermal system is limited by the design and capacity of the heat pump. A maximum pressure of up to 6 bar is provided for in powerful heat pumps designed for heating and passive cooling of multi-storey buildings.
As the geothermal probe sinks to depth, the pressure increases, consisting of the pressure at the surface + the pressure of the antifreeze column.
The probe installed in the borehole is pressurized from the inside by antifreeze and simultaneously pressurized from the outside by water, soil or tamping of the borehole. Internal and external pressure compensate each other. The probe is guaranteed to withstand pressure up to 16 bar, so it remains intact.

What kind of antifreeze is in geothermal systems?
Antifreezes consisting of 65% water and 35% propylene glycol (food additive) or 72% water and 28% ethanol (ethyl alcohol) are absolutely safe. Other antifreeze products pose some environmental hazards. Discuss antifreeze composition with your installer.

What are geothermal probes made of?

A geothermal probe consists of:
1. Two long parallel polyethylene pipes;
2. One short U-shaped polyethylene pipe (so-called "U-turn") connecting one end of the pipes to each other;
3. Two polyethylene electrofusion couplings with which the long pipes and the U-turn are welded.


What are cluster geothermal wells? What are their advantages and disadvantages?
A geothermal probe is sunk into a pre-drilled well in the ground. Wells can be vertical, and slanted. It is possible to drill inclined wells from one location, in different directions, and get a group, or so-called "cluster" of geothermal wells. A cluster of geothermal wells occupies a minimum area on the surface of the earth, the upper part of the wells being close to each other
Geothermal probes draw heat from the ground while the surrounding ground cools. Probes that are too close together take heat from one another, so the recommended distance between vertical geothermal probes in dry ground is 10 meters. If the probes are arranged in a row and the ground at depth is saturated with water, the distance between vertical probes is sometimes reduced, but not less than 6 meters.
In the case of clustered geothermal wells, parts of the probes are less than 6 meters from each other, so it is better not to consider them as a heat source.

Lengths of cluster probes located less than 6 meters between each other, depending on the number of probes, and the angle of deviation of the probes from the vertical:

Angle of inclination
of the cluster probes,

Number of probes, pcs.
2 pcs 3 pcs 4 pcs 5 pcs 6 pcs 7 pcs 8 pcs 9 pcs 10 pcs
30° 7 m 8 m 9 m 11 m 13 m 13* m 15* m 16* m 18* m
45° 5 m 5 m 6 m 8 m 9 m 9* m 11* m 12* m 13* m
* Inclined wells + one vertical well
Example 1: If the angle of deviation of cluster wells relative to the vertical of 30 ° - the length of each of the 5 cluster wells is desirable to increase by 11 meters compared with the vertical wells.
Example 2: If the angle of deviation of cluster wells relative to the vertical of 45 ° - the length of each of the 9 wells is desirable to increase by 12 meters compared to the vertical wells, 8 wells to make a slant and one vertical.

The advantages of cluster geothermal wells are that they are placed on a minimum land area, no trenches are needed to each well.
The disadvantages of cluster geothermal wells are the increased length of the wells, the cost of inclined drilling is about one and a half times more expensive than vertical drilling. If cluster wells enter someone else's territory, there may also be ownership problems.

What is the advantage of turbine probes?
Geothermal heat moves from the ground, through the polyethylene wall of the probe pipe, to the heat transfer medium (antifreeze) inside the probe. The heat transfer coefficient of the materials:
     - ground 1.1 W/m°K;
     - polyethylene 0.4 W/m°K;
     - antifreeze 0.6 W/m°K.
Polyethylene has the lowest thermal conductivity and is a kind of "bottleneck" in heat transfer. Therefore the wall thickness of the polyethylene pipe must be as small as possible. Contrary to this, in turbine probes thickening of the polyethylene wall is made, which worsens the heat transfer.
The movement of antifreeze in either a turbocharged or non-turbocharged probe is generally in turbulent mode.
It seems that only marketers benefit from turbine probes.

How long do geothermal wells last?
The polyethylene used to make geothermal probes is indestructible underground. Polyethylene pipes are proven to be reliable and are used to make gas pipelines.
A geothermal probe will work as long as the building to be heated and cooled is standing.

What are the pros and cons of geothermal heating?
    - you have to have land where to make geothermal wells or a geothermal horizontal field;
    - relatively expensive.
The pluses are that geothermal heating is extremely efficient, and about 4 times cheaper than traditional heat sources. It's also renewable, clean energy, so it's good for you, helps pay the bills, and doesn't poison you or the environment. Geothermal heating is a good investment for the future.