Well i went and looked at one today and it perfect for a turbine. With about 10m of head pressure and plenty of flow. Been doing some research and found that navitron actually do them. Looking at £1600 for the turbine, and around £1000 for a Grid-Tie Inverter (3phase), so u can sell the electricity back to the grip. Im assuming they would pay you what you pay for electricity, around 14p per KW. That would earn you over £1200 per year.