Finally, I know what you’re thinking: VAWTs, while benign to birds – isn’t that great! – are known for their inefficiencies. Jonathan and Linda recognize this fact, and they say that they have developed a turbine that overcomes that downfall. The key, they say, is Sky Farm’s size — 50 kW — and its expected use on high-rise rooftops of 300 feet or more. The total weight of the turbine, in case you’re wondering, is 4,698 lbs. — relatively light for machinery that is located on highrises, the designers say.