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I don't understand why STES - or more specifically BTES (Borehole thermal energy storage) - isn't more popular.

I understand that is has a high implementation cost; excavation, drilling, evacuated heat pipes, (and usually a centralized heat exchanger). But is that the only downside? Or are there other factors which make this solution less practical?

  • I've seen good results reported from an installation in Germany. But high upfront costs are very off-putting at least until the reliability is proven - repairs could get expensive. You also need the right seasonal variation - hot summers and cold winters - otherwise it offers little over ground source heat pumps. – Chris H Mar 29 '16 at 20:07
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    It may be a matter of it not being widely known. If it's not known about it can't be discussed and be in the forefront of people's minds. – Fred Mar 30 '16 at 1:51
  • The energy payback period is likely to be quite high compared to ground source in most places - the target for STES is most likely places where simple ground source isn't feasible for some reason. That's even more relevant for most countries where building standards are so low that the easy wins (draught-proofing, insulation etc) are still available. Like, say, Australia, where I live. – Móż Mar 30 '16 at 2:36
  • It's my understanding that ground source (heat pumps) are more geographically restrained to climates with hot summers, and cold winters, because if you only extract heat, you may reduce the system's operating temperature and cause it to be less efficient. Living in a colder climate - I'm predominantly looking for a heating solution. So injecting summer-time heat gathered by evacuated heat pipes seems to make more sense, in terms of efficiency. But to acknowledge your point, yes.. It seems that STES is the solution to a geographically-limited problem. – Aaron Mar 30 '16 at 14:21
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Pretty much any and every energy system needs lots of storage - either real, or virtual in the form of demand-side response.

The old energy system, the one we inherited, had absolutely vast amounts of energy storage built into it, in the form of oil, coal and gas storage. And that's the main reason there's no market for STES.

But for about 40 years, we've known that the price for that was way too high - the pollution is destroying us.

However, it meant that for a very long time, there was no economic incentive to build much storage at all. The only storage that got built, really, was either to cope with inflexible nuclear power (overnight storage heaters) or their intermittency (pumped hydro storage to provide rapid-response power within seconds, for a few hours, when very large power plants drop off the grid).

And because most countries have had powerful incumbent fossil fuel supply chains, then although this is a problem we should have started fixing 40 years ago, many countries are only starting on it now.

So, we have little understanding of how to build seasonal thermal energy storage (even though it can be pretty simple engineering), and of its whole-life costs. And there's still no market for it.

Some places, such as Denmark, are building larger stores for their district heating schemes. And to their credit, they did start on heat storage decades ago, in response to the 1970s oil crisis, and never stopped.

Other places are now looking at thermal energy storage of various forms, and there are demonstration projects in place.

  • To clarify; you're suggesting that there's no market for STES because of a lack of public understanding, and the uncertainty of whole-life costs. Is this correct? – Aaron Mar 30 '16 at 14:09
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    @Aaron the main reason that there's no market for STES is because fossil fuels provide vast amounts of storage already. – EnergyNumbers Mar 30 '16 at 14:32

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