I found recently the existence of Geothermic Energy and i didn’t really understand It.
There are zones where the underground is so hot we can get energy (Electricity) from it. How?
I read that One of the first to do It was in Italy, in the 1904 or something, and i don’t understand how could they build something without…well die. If the heat is so High wouldnt people be hurt? How could they build something like that? I guess that now is more easy but at that time how was that even possible?
In: Other
Lava is deep underground and very hot. If you put water near the hot lava, it turns into steam. If you pipe the hot steam into a turbine, you can make something spin. If you stick some magnets on a spinning thing and have them spin near coils of wire, you get electricity.
It’s pretty simple. You drill a borehole, you put a U shaped pipe in it, you pump water through it and use the hot water at the surface to generate energy. (I.E. steam spins a turbine, wich spins a generator)
No human needs to get into the hole, and they’d indeed not survive it.
How deep you have to drill before it gets really hot is also regionally very different. Like, in regions with active vulcanoes you can find places where you only need a few hundred meter to reach boiling hot water, while in other areas it’s more like a kilometer deep
The core of the Earth is hot for multiple reasons, residual heat from the formation of the planet, nuclear decay, tidal action, etc.
To get access to this heat in places where it isn’t conveniently getting to the surface by itself (hot springs and other volcanic things) they drill a very deep hole hole, using many of the same techniques as oil drillers. Then they pump water down the hole if there isn’t a convenient layer of groundwater there. The water seeps through the porous rock and heats up because the rock is hot and is then pumped up through a separate hole. Then a heat pump extracts the heat from the water to boil some other water, the steam produced spins a turbine and produces electricity and the now cold water is pumped back down to be heated again.
It doesn’t require special pockets of high heat, though they can be harnessed. Basically, everywhere that you dig, the ground is about 50 degrees Fahrenheit and the Earth is really big and has a huge thermal mass, so if you move energy from that ground it will heat back up from the energy of the ground around it and you can continue removing heat from it.
[removed]
I’ll point out that in addition to geothermic energy there’s geothermal for the purpose of building conditioning. This is more broadly available and common because you don’t need access to exceptionally hot geothermic activity like a volcano.
In short: As others have pointed out certain regions have easy access to very hot temperatures to create steam to generate electricity but geothermal for building heating and cooling uses broadly available steady mild geothermal temperatures just below the surface. This isn’t used to produce electricity because there’s not enough energy density to make steam which is what’s required to generate electricity. It is however good to use as a heat-sync.
In long: Most air cooling is done by moving heat from an interior space using a refrigeration cycle to the exterior air using electricity. The reverse can be done to heat an interior space by moving heat from the exterior to the interior by reversing this refrigeration cycle. This is done with an indoor unit connected to an outdoor unit with refrigeration piping. This would be called an air cooled system. The refrigeration cycle is doing the work of moving the heat but the final heat sync for that heat is the outside air. One of the drawbacks of this is that outside air varies considerably and usually in the opposite direction of what would be efficient. You’re trying to pump heat from a 70F building to a 80-100F outside air and when you’re trying to heat the building you’re trying to maintain a 70F interior by pulling heat out of the -20F to 60F exterior air.
Instead of an air cooled system you can use a geothermal system. The same refrigeration system is used but instead of using an exterior refrigeration to air heat exchanger you use a geothermal loop to refrigeration heat exchanger. The ground several feet below the surface maintains a fairly constant 50F, water is pumped through loops in this region either by going vertically down hundreds of feet over a small surface area footprint or it can go horizontally in a shallow area taking up a larger land footprint. Now you’re not relying on changing outdoor air temps and fighting up hill against the seasons but using a steady temperature heat sync that’s closer to the temperature you’d trying to maintain indoors. This system is more expensive to impalement than air cooled because you need to either drill wells or a large trench whereas an air cooled system just requires a place to put a condensing unit outside but due to the increased efficiency of the refrigeration cycle having to do less work the geothermal can result in cost savings over time. This tradeoff gets better with scale – might make more financial sense for a large building to implement than a residential single family house. Geothermal also has the added benefit of not needing a mechanical unit outside which helps with aesthetics. A large hotel or university or mansion can put the geothermal unit in the basement or a nice looking out building without needing either a big ugly outdoor unit with noisy fans or multiple smaller ugly boxes with noisy fans.
Ok so power plant basics.
Coal, Oil, Nuclear, Wood, etc.
Get bunch of stuff HOT. Use heat to boil water. Use steam to spin turbine (windmill). Turbine spins generators.
Geothermal just replaces the pile of burning stuff with the Earth’s core (well Nuclear isn’t “burning” but close enough).
Hydro and Wind cut out the heat and use water or air to spin the turbine.
Natural gas is a bit more complicated, because in a combined plant you basically have a big jet engine spinning the turbine and then use the exhaust to spin more turbines. There might be a steam loop in there somewhere too.
Solar panels are the only source that produces electricity directly.
Maybe just an addition to the point “wouldn’t people be hurt”. For using geothermal energy, you normally still have to drill a few hundred up to thousands of meters to the Earth, the surface isn’t that hot. But there are occasions where the heat comes directly to the surface, like Geysers and volcanic eruptions. And they definitely can hurt people. It’s also possible that the temperature on the surface is too low for a power plant, but just enough to heat water to the temperature of a hot tub, so you can bath in it.
Geothermal*. Most power plants convert heat into electricity via hot water rotating a fan. The neat thing is it doesn’t matter where the heat comes from, as long as it’s hot enough to spin it.
Outside of solar, wind and hydroelectric (which combined are only about 15% of power generation), pretty much all the electricity we generate in the entire world is done by boiling water into steam and using that steam to spin a turbine. What we use to heat the water varies from coal to natural gas or diesel fuel, or nuclear.
Geothermal energy is just another way to heat the water. If you’re in an area where it’s really hot underground due to volcanic activity, you can pump the water down there, let the earth warm it up, then pump it back up and use it for the same water-boiling-turbine-spinning process.
It doesn’t have to be brought all the way up to boiling, just made significantly hotter. Normally, if the water starts at 20 degrees you have to use a lot of coal/gas/whatever to heat it all the way up to 100 degrees to boil it. Maybe you can use geothermal energy first to bring it up to 80 or 85 degrees, now you’re starting with much warmer water so it takes much less coal to heat it up the rest of the way to 100.
Latest Answers