Saturday, September 20, 2008

Pump as Turbine (PAT)

This is the latest addition to the powerhouse. This split case PAT, 5X6X9 driving a 30HP 3 phase motor as generator will be able to take advantage of the much higher winter flows of the stream. The pump/turbine has been mounted at a 45° angle to eliminate 2 right angle bends in the powerhouse plumbing and there is enough room to accommodate a large flywheel on the generator shaft to enhance mechanical momentum. This will improve voltage regulation and large motor starting capability.

I have a number of Distributed Load Controllers on 1.5kW space heaters in the winter months when there is plenty of water. Then the turbine control valve is wide open all the time and DLC's will have the heaters going full blast until a refrigerator or well pump comes on. Then the DLC's will proportionally reduce the power to the heating loads to keep the voltage constant and allow the motor loads to start up. The 3KW dump load and DLC in the power house penstock is set to a slightly (5V)higher voltage to react to over-voltage situations that might arise if the valve is wide open and loading suddenly decreases. That dump load will absorb the extra power and give the (slow) motorized butterfly valve a chance to close and reduce the power. It is when we are lightly loaded in the spring and fall that I think the flywheel idea will help to regulate the voltage better. I have also just put a few DLC controlled electric heaters outside! Such a waste, but it keeps everything stable.

We are still in drought conditions and waiting for more rain before I can run at full power with the valve wide open. (Our drainage area is only 1.5 square miles) I'm thinking about adding a small efficient pelton to use around 1 gal/sec @ 210' of head so we can keep running through the summer months. Of course none of this would be necessary if we were grid connected on net metering. We are just getting started on the paperwork to get grid connected. To me it seems a bit daunting because I don't like to do paperwork or deal with bureaucrats.