Low temperature geothermal thermoelectricity isolated site

Renewable energies except solar electric or thermal (seeforums dedicated below): wind turbines, energy from the sea, hydraulic and hydroelectricity, biomass, biogas, deep geothermal energy ...
dirk pitt
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by dirk pitt » 24/09/14, 13:13

just a passing note: too often one twists on the performance of a device (especially when it is very low like the Seebek effect) but it is sometimes not a problem when the source is abundant.
it is a little the case in solar PV, the output is not great but the source is free and inexhaustible.


on the other hand for the case of our friend, he tells us that he has a river available, so, here I say, do not bother with drilling, hop, a low-fall turbine, it's reliable that works 24 / 7 / 365
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Gaston
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by Gaston » 24/09/14, 13:57

dirk pitt wrote:just a passing note: too often one twists on the performance of a device (especially when it is very low like the Seebek effect) but it is sometimes not a problem when the source is abundant.
If we had a hot spring and a cold source available without consuming anything, it would be perfect regardless of the performance of the generator.
Here it is necessary to pump ... and thus that the production exceeds the consumption of the pump ...

dirk pitt wrote:it is a little the case in solar PV, the output is not great but the source is free and inexhaustible.
But PV does not need to power accessories to produce.

dirk pitt wrote:on the other hand for the case of our friend, he tells us that he has a river available, so, here I say, do not bother with drilling, hop, a low-fall turbine, it's reliable that works 24 / 7 / 365
Totally agree, but our friend already seems very decided on his solution (drilling and peltier are essential).
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by Gastonn » 24/09/14, 14:44

the concern of the PV is its daytime use and the necessary surface not to mention the low rate of sunshine

the concern of the production with a low fall turbine will be the uneven flow and the space heating impossible with this system
with my drilling I hope to reach a temperature of "preheating" + electricity production

that's why I'm interested in this solution
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by Obamot » 24/09/14, 15:42

dirk pitt wrote:
dirk pitt wrote:on the other hand for the case of our friend, he tells us that he has a river available, so, here I say, do not bother with drilling, hop, a low-fall turbine, it's reliable that works 24 / 7 / 365
Totally agree, but our friend already seems very decided on his solution.

Totally agree, I had seen that (but I did not dare to propose, for the same reasons + lack of detail on the implementation, no photos, etcsss) ;-)
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by Gastonn » 25/09/14, 11:17

I am not particularly fixated on a method, but rather on results.
what solution to supply and heat a local 200 m2 cold isolated site and little sun (1680 h / year less haze)?
the hydro source will be put to profit but will only produce 280 / 310 w, the solar too but with all its production defects.
I still have to heat up, neither of them can.
(except to verify a solution by summer thermal storage in soil but to weight because of the low average temperature)
that's why I naturally considered a geothermal solution, on the one hand to pre-heat (17 / 18 degrees it is already not so bad) and therefore more to produce electricity, since anyway the drilling will be there.
that was my approach, but if I'm wrong, I'm open to any other solution.
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by Obamot » 25/09/14, 13:43

Hello Gasonn,

The interest of your project is that it can constitute an interesting springboard to a geothermal solution for a lot of people ...

I understood that, but above all, I tried to put myself in your shoes and reason in the direction of what would be in your vested interest by setting the "priorities that are going well".

From there, it would be well to explore different possibilities to prioritize according to the means you want to implement.

So in your place - and taking into account what you told us - I would proceed as follows.

1) Given the fact that you told us that a borehole would be within your reach since you are in the game, I will start with a borehole to start, on an experimental basis and at -366 meters.
Indeed, if it turned out that the result with a borehole, does not correspond to your expectations, it should be sufficient at least to heat the room to 20 ° C ... So nothing lost, even if you don ' do not get the coveted electric power ... (In the opposite case it's all good ...). Anyway, it would be good to do a coring at various depths to determine what basement you have to do, So both take the opportunity to drill frankly and that it serves something.

2) With a little bowl (since there is a river it is very likely) you could fall on a water table .... And then there, depending on its temperature, you would eventually need to drill more deeply! Who knows ?!?!

3) Then, depending on the result, you could see if you would go to hydro or PV (or both) or anything other than drilling if luckily your goals were met.

4) On the other hand, I remain convinced that the best return would be achieved with cogeneration when it comes to "producing electricity", because here at least we are sure of what we can obtain with high temperatures (but as long as you have a wooded area as a deposit not too far away). As I said above.

It's just my opinion, but I could be wrong. Anyway drilling is interesting, and you can experiment with this solution.

Moreover, this is the right time to do it, since we are heading towards the cold season, you could thus see what it would already be possible to capture in depth, and until the summer, and to establish a statistic! So you would gain 1 year ... Whereas if you waited until March or April, you could hardly draw the appropriate lessons! (Ditto for taking readings of the flow of the river or for the level of sunshine, if at all you would see an interest with PV panels. Notice that there are "sun maps" for your region, and by country) Anyway, the time is right!

In summary, I think drilling is worth trying whatever happens, there is nothing to lose.

Kind regards.
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by Gastonn » 25/09/14, 14:26

absolutely, that's quite my conclusion
I am actually setting up a low diameter drill (30 / 40 mm) to probe the ground over several hundred meters.

one must not forget a fundamental fact: the cost of the current drilling is constrained by the depreciation of the tools (several hundreds of thousands of euros) and their obligation of speed of drilling: a building site can not be blocked several weeks for a hole ...

if we go on deeper and slower boreholes, the costs collapse.
we did slow drilling tests on large depths (by discretion I would not spread too much) and with light tools, it works and this is one of the reasons for my choices.

I have more to do than Gainsbourg ...
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by Obamot » 25/09/14, 18:53

Wow! 40mm only?

Don't you fear that with such a small diameter, the heat transfer fluid will cool down as it rises from the depths, to drop to 12 ° C ("average" temperature of the first hundred meters)? In addition in this diameter, it will also be necessary to subtract the thickness of the duct! Finally, because of the small diameter, I fear that the hole will fill up as the drill head is withdrawn? Or does it depend on the drilling method that would lay the PVC pipe as it goes (and the head would be dropped to the bottom once the desired depth is reached)?

Well, it's not my job too much, drilling ...

(I gave a link with the locative witness / project of the EPFZ, it seems to me that it was more than that).

gastonn wrote:one must not forget a fundamental fact: the cost of the current drilling is constrained by the depreciation of the tools (several hundreds of thousands of euros) and their obligation of speed of drilling: a building site can not be blocked several weeks for a hole ...

if we go on deeper and slower boreholes, the costs collapse.

Wouldn't you rather say that the longer the site lasts, the more the prices "explode" (or I didn't understand ..?)

In my area, just "site installation" costs € 1'250.— (although I find it not very expensive.)
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by Gastonn » 26/09/14, 12:22

the 40 mm are only for probing and checking the temperature
I then consider a drilling @ 100mm (by progressive drilling)

for the problems of thermal losses of the fluid, I envisaged a solutions in corkscrew on the lower part to increase the exchange surface of the pipe (as in the new geothermal probes) and the rest in vertical and isolated tubing.
but it is true that I do not know how to calculate the thermal equilibrium of the system, if anyone knows how to do it ...
from my discussions with geothermics, it seems that the loss to be expected is 1.5-2 degrees ... I will still try to clarify this point before drilling.

the collapse of the well is also a question. it seems that it really depends on the terrain with zero landslide cases with partial hitching cases.
as in any case I opted for a solution of drilling and clearing in two stages, I hope that I would have at least the time to push my pipes.

regarding drilling costs, I think it's the obligation to go fast that costs a lot:
all is due to the fact that at the base drilling was developed for heavy industry :(petroleum research, construction of building, passage of lines etc ...)
so it can not be a bottleneck and its machines are very expensive.
the need for energy and small boreholes is very recent and nothing has been done in this direction yet.
in any case, we arrive at prices of 100 € + per ml while light techniques "collapse" this price, such as for example pneumatic rockets which are around 20 € per ml
and I do not even mention here all the drillers who regularly go to 50 / 60 ml with artisanal solutions and that we find mainly among the ancient dowsers who have developed these light techniques.
(I'm talking about the real dowsers of trades not charlattans with a baguette)

We must not forget that we are just talking about making a hole in the ground and that we are at a time when we can fly a drone 10 km with a live camera for 1 000 € or
buy a 10 000 w 10 w engine for 400 $ ...

I'm greedy maybe, we'll see, in any case I would be at least amused to try, it's already not so bad
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by chatelot16 » 26/09/14, 16:53

if the peletier module gives you a yield of 1% when it is directly placed between the hot and cold source it means that it takes 10kW of heat to make 100W of electricity

what flow does it take to carry heat 10kW? I'm afraid the pump consumes more than 100W

it is necessary not to pump that in the drilling, it is also necessary to pump or to ventilate the other face of the module peletier

this is the whole problem of the use of low temperature, not only the maximum yield allowed by carnot is low, but the transport of the large amount of heat eats all

in the case of the thermal energy of the sea, the bottom water is pumped into a large diameter pipe, which reduces the pressure drop and limits the pumping power.

with a borehole it will be necessary to be satisfied with small diameter: the least pump will blow all

at sea there is only to circulate, no pressure due to the height of the ground above the water table where you pump
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