25 years of drilling straight down. How hot is it down there? Could we convert the hole to a geothermal power plant by placing a down water loop down the length of the hole?
25 years of drilling straight down. How hot is it down there? Could we convert the hole to a geothermal power plant by placing a down water loop down the length of the hole?
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> Could the super deep bore hole produce geothermal power? 25 years of drilling straight down
Assuming we’re talking about Kola or something similar, while activities there stretched across a few decades, it’s not as though (1) drilling was active that entire time or (2) it took that long for a single hole to reach the total depth. I.e., it’s not as though it took 25 years of consistent drilling of one particular borehole to reach the 12 km+ depth of Kola.
> How hot is it down there?
If we look at results from the deepest hole at Kola, i.e., SG-3 (Popov et al., 1999) the temperature at the base of the hole (measured ~20 days after drilling had completed) was ~190 C (e.g., Figure 5 in Popov).
> Could we convert the hole to a geothermal power plant by placing a down water loop down the length of the hole?
190 C at a depth of 12 km is pretty cold, all things considered. If we look at variation of critical parameters for the productivity of a geothermal power plant and the conditions in Kola, geothermal gradients (i.e., rate of increase of temperature as a function of depth) top out at ~25 C / km but are much lower for much of the borehole depth (Figure 4 of Popov) and heat flux (which in the case of Popov is referred to as heat flow density) hovered around 60 mW/m2 for much of the borehole. If we compare this to global databases of geothermal gradients and heat flux, like those in Kolawole & Evenick, 2023, we can see that these geothermal gradients are basically at the low end of what you’d expect in continental crust. In contrast, areas of thinner continental crust, would have average geothermal gradients of 50-100 C/km.
In terms of geothermal power generation (and it being worth the effort to drill holes for it), generally higher values of geothermal gradients are better because (1) hotter rocks are going to be more efficient at heating up the fluid you’re circulating and (2) drilling is expensive so if you can drill in a location that has a high geothermal gradient, you can drill a shallower well to get to a suitable temperature. So, if you drilled a hole in a place with a 100 C/km geothermal gradient, you’d only have to drill ~1.9 km deep to get to the same temperature at the base of Kola, i.e., Kola would make a pretty bad geothermal power well.
Geothermal power is used to generate electricity in many places https://en.wikipedia.org/wiki/Geothermal_power but it has varying success in different places depending on how close to the surface the magma is.
There was an experimental geothermal project in England in the 80s that decided it wasn’t commercially viable as an electric power plant but it was worth reusing the holes to produce the heat for homes. https://en.wikipedia.org/wiki/Southampton_District_Energy_Scheme You don’t need as much heat to provide hot water for radiators compared to boiling water into steam to turn turbines.
The Kola Superdeep Borehole is in the middle of nowhere. It’s an extremely rural area up near the pole, the region is twice the size of Rhode Island with a third the population. They’ve got a hydroelectric dam and don’t really need a geothermal power plant.
My question would be is it economical/feasible for a pump/pumps to move water that distance. I know you could use a positive displacement pump to actually move it as they pump the same volume regardless of outlet pressure, but they are relatively low volumetric flow rates. At almost 18000 psi at the bottom of 40000 feet, seems unlikely to happen.
Check out Pushkin’s “What’s your Problem” episodes with Fervo Energy or Quaise Energy Which are two examples of companies using Oil & Gas drilling knowledge to expand geothermal energy.
In theory yes, this was tried in Helsinki for district heat with two 6km boreholes, you can read an interim report here, it’s hard to find info but I believe this project actually failed – it seems the return water temperature wasn’t very high.
Depends on how you define geothermal, but ground source heatpumps work pretty well for heating homes (including heating water) and can be as shallow as a meter or two.
It doesn’t take much depth to have a fairly constant ground temperature all year round and that can be used to heat homes. It’s not that the ground is particularly warm, but it works as a giant heat sink and that can be used to reach much higher temperatures via compression.