Regarding generating electricity by prison treadmills, that was one of a large number of cost-cutting schemes put forward by the public to the Government last year. This news article mentions that particular suggestion:
The suggestion got through the Treasury moderators but unfortunately it doesn't look like it is going to be implemented.
If Huhne does go to prison, it would be advisable for him to show more common sense than the last prominent Green-leaning ex-minister who ended up in prison. Elliot Morley, former environment minister and former president of the shadowy GLOBE International organisation, who is currently serving a prison sentence over the MPs expenses scandal, turned up at the prison wearing a £3000 Rolex watch. Word got around the inmates that Morley had an expensive watch, and as might be expected, an inmate assaulted him and stole his watch.