Renewable Energy has many parts, and some of them can do jobs that others cannot do. It is important to work together to bring the best renewable Energy to the world that we can hope to achieve.
This diagram represents a short overview over different elements of a renewable energy network, and what the different parts can do, and what not.
For example, Hydropower can be both an energy source (flowing water through a turbine) but also a means of energy storage (by keeping the water behind the dam). Renewable Biomass can be stored well, but can also be turned into a renewable source of energy. Batteries can store energy well, but cannot produce energy.
Where does geothermal fit in all this? I don't think it can really be used as an energy storage system unless there's some technique I'm not thinking of, but since it isn't as intermittent, it doesn't really need much energy storage either, as far as I'm aware.
I've noticed it seems to get left out of a lot of discussion on renewables, but I'm not sure why.
Biomass and hydro* aren't storage for intermittent power (*except pumped hydro). Rather they are natural sources of accumulated solar power that can be tapped on demand. In that sense, so is geothermal.
More a potentially infinite (within human lifetimes) heat source from a still-warm Earth interior. Limited in that you can't harness it from anywhere other than local.
Nah it's friction from rocks banging into each other when the Earth was being formed. The surface of the Earth cooled down, but you dig down deep enough it gets really hot. Hot enough to melt rocks, or as the pros call it... "magma". Dump some water down there and you get steam and you can drive a turbine with that steam. Though actual geothermal energy implementations are probably a little more complicated than that. But that's the gist of it.
The Earth has an internal heat content of 1031 joules (3×1015 TWh), About 20% of this is residual heat from planetary accretion; the remainder is attributed to past and current radioactive decay of naturally occurring isotopes.
In that sense, it's the only renewable energy source we have that's not indirectly powered by the sun. It's most similar to (proper) nuclear power, but the latter isn't "renewable" because it requires digging up fuel from the crust.
In some senses the whole planet is storing a huge amount of energy underground.
But yeah I think in the context of this kind of discussion it's would be a renewable energy source. While it's probably technically not renewable, but there's so much of it we'd never run out. I mean if you want to be super-pedantic, solar and wind aren't renewable either because we don't have a way to make a new sun when that thing burns out, but it's like come on.
But probably not a storage solution, because why would you put energy into the Earth's core? We worried about hell freezing over or something?