Wednesday, August 13, 2008

hydraulic transmission to simplify wind power?

i'm a bit out of my depth here, but thoroughly interested.

the idea, briefly mentioned here as an aside, is that a new high-efficiency hydraulic pump will allow a simplification of wind turbine design by allowing the big lump of electric generator to be relocated from the nacelle to the ground. this is advantageous because the generator is big and heavy and occasionally requires maintenance. moving a big, heavy thing that requires maintenance from the top of a 250 foot pole to the ground provides obvious advantages. the reason it isn't already a common practice is because the mechanical transmission options available have been too expensive (like a 250ft long crankshaft) or too inefficient (like the commercially available hydraulic pumps).

sounds pretty cool, no? it could reduce wind energy costs by making the turbines less expensive and easier to maintain. the unpopular knowledge is that wind turbine transmissions have long been a weak point.

my extrapolation questions based on a pretty weak hydraulic fluid background:
1) can you take the hydraulic outputs from several wind turbines to power one generator and further reduce costs? a single 100 MW hydraulic-powered generator should demonstrate significant costs savings compared to 100 1 MW generators.
2) can you economically store energy using hydraulic pressure? enough to level the power output from wind sources on a 10 minute scale? 1 hr scale? more? this would increase the value of wind power by decreasing the cost of integrating it into the power system

edit: this paper by Artemis IP in Scotland demonstrating a hydraulic transmission for wind generation suggests that moving the electric generator from the nacelle isn't terribly interesting and implies that only a very small amount of energy storage for sub-second smoothing purposes is worthwhile. the study was done for wind turbines at the 800 kW scale. maybe the results will be different at the 3-5 MW scale.


Tom said...

I wonder if the small amount of flexibility in the hoses and connections to the motor would loose energy and make it less efficient. Even the smallest change in circumference under pressure over that distance would be significant I would think.

shaun said...

i imagine it'd be like a compression spring. as long as the hydraulic hose eventually returned to the normal circumference, little energy would be lost.

U K said...

integrating this way is a pretty good idea. and i agree with shaun. if the energy is not lost as heat, it stays in the system.