turbines were installed at all houses where economical in the UK, they would
generate in total roughly 0.7 kWh/d/p. They advise that roof-mounted tur-
bines in towns are usually worse than useless: “in many urban situations,
roof-mounted turbines may not pay back the carbon emitted during their
production, installation and operation.”

63Jack-up barges cost £60 million each.
Source: news.bbc.co.uk/1/hi/magazine/7206780.stm. I estimated that we
would need roughly 50 of them by assuming that there would be 60 work-
friendly days each year, and that erecting a turbine would take 3 days.