Or just a small wind turbine with resistive heating; it's not like Scotland lacks wind. I imagine they didn't use PV because

1) Scotland doesn't get much sun,

2) it'd get nicked by the first viking that came along, and

3) if they put it on the roof then it'd be a nightmare replacing the thatch.

=p

They burned peat, not wood. And I think the smoke was part of the point? The article claims it kept pests out of the roof. Presumably it kept midges away too. Though obviously living with all the smoke wouldn’t be so nice.