They used to have a small scale nuclear reactor run by the army but it was too difficult to maintain without issue so they ended up decomming it. At mcmurdo an

They used to have a small scale nuclear reactor run by the army but it was too difficult to maintain without issue so they ended up decomming it. At mcmurdo and scott, wind power, etc are healthily supplementing and slowly substituting diesel but ultimately arctic diesel will stay a staple because it consistently operates at extremely low temps. Especially inland where the temperatures are regularly lower than -70C. As for the geothermal being banned, that's because it takes a lot of digging and "permanent changing of the environment". Doubly so since the low temperature environment means you have to use a ton of additives in your transfer fluid to keep it from freezing up during condition 1. If the circulation loop blows, those additives will stay in the environment effectively indefinitely given the weather. So as much as I prefer geothermal, it makes sense why it's banned. Even if they just accepted the risk, they'd still need diesel infra in case of emergency or else there's a very real risk of people on station dying in the middle of a long, hard condition 1 storm which would prevent fly-ins from bringing emergency supplies. Also it's only mcmurdo(~1k people), scott(~70-80 people), palmer(~40-45 people), rothera(~150 people), and signy(~10-15 people) which have actual ground contact that aren't in a pristine field lab environment (like the dry valley) so there's only a few locations that could even use geothermal. The rest are either in field lab environments where you can't risk contaminating the ground or on ice shelfs where you have to dig down a few hundred meters or even a few kilometer to find anything other than solid ice. Of those few viable locations, only mcmurdo, scott, and rothera actually justify the infrastructure cost (with all but mcmurdo only having enough people to justify it in the summer months). So ultimately instead of choosing between maintaining diesel infra and maintaining both diesel infra and geothermal which both have their own problems you know have to address, they chose to just use diesel unless a project can prove the geothermal infra won't have con 1 failure and deep ground contamination risks.