The UpWind Project, which is funded by the EU, is attempting to create ginormous 20 MW offshore wind turbines. You can’t just take a 5MW tubine and make it bigger because the laws of physics intrude rudely.
However, scaling laws show that if you scale dimensions to the power of two, the weight goes up to the power of eight. This means you’ve got four times as much energy but eight times as much weight, and therefore, cost!
Also, the blades needed to be redesigned so they have a independent flap like an airplane wing. This cuts the weight of the blade by 25%.
Models of these turbines work in the lab. No one knows yet if such behemoths can be sited successfully in the ocean. If they can, then each 20 MW turbine could produce energy for 13,000 homes.