'Massive leap' wins engineering award
bbc.co.uk
bbc.co.uk
There is an animation and a good description here:
So as I understand it, their system allows one to disconnect volume and pressure of the fluid coming out of the pump, with the actual speed at which the pump is operating. That lets you vary the work done by the hydraulic motor independently of the speed of the pump without resorting to a transmission.
Given that they have it running on a 7MW turbine that is pretty cool. (ok a 7MW wind turbine is pretty cool all by itself)
It would seem like maintaining the valve system and controller would be easier than maintaining a gearbox (they say as much in their overview) but I didn't find any good operational metrics (is it 100 hrs a month of maintenance vs 10 hrs? Or 60hr of maintenence for every kWh vs 6hr? something like that)
Nowadays diesels don't use that anymore, they've moved to a very high pressure common rail and electronic valves.
The problem it is trying to solve: wind turbines have a significantly variable range of speeds/energies. The wind speed varies significantly from the bottom to the top. It is desirable to have the generators directly produce power at 50/60Hz grid frequency to avoid needing lots of power electronics. To match this variable but low speed system to the generator you need a gearbox. (There are other systems using low freq generators but I'm vague as to how they work.)
A conventional gearbox (ie cogs) which can handle the massive energy transmission is expensive enough, but one which can change gears to deal with a range of input speeds is even more expensive and heavy. Since the gearbox is at the top of the turbine tower it also makes construction and maintenance more difficult. Many turbines spend time with their blades locked because the wind is too strong - they would turn too fast for their gearbox to handle. Also significant downtime for gearbox repairs.
The alternate solution is to change from kinetic rotational energy to hydraulic transmission, where the blades drive a pump, which pumps a fluid, which drives a motor, which is directly connected to an electric generator. These hydraulic systems have good power density and reliability but typically suffer from low efficiency if not at full load (high frictional losses from un-required piston actions).
The innovation is that they are able to achieve high efficiency in the pump/motor at a variety of input loads through use of computer controlled valve actuators. This doesn't sound that revolutionary, and indeed people have been working on it for a long time, but maybe they have something that works.
http://hydraulicspneumatics.com/hydraulic-pumps-amp-motors/h...
It seems they invented this technology for wave power, some fancy engineering. I wonder if they can retrofit present turbines with this new tech.
All have constant speed(1) and variable blade pitch.
(1): gusts can change that momentarily. No mechanical gear could react to gusts anyway.
This has an explanation why it's not always useful to go at max speed: https://en.wikipedia.org/wiki/Tip-speed_ratio
In general, the modern technology trend has been replacing mechanical components with electrical ones. Frequency converters have become successful, and they have no moving parts and are very efficient.
On the other hand, if this can get rid of the mechanical gear at the same time, it might be a wash.
But since Vestas and Mitsubishi wind power are combining and it seems the hydraulic technology used in that Mitsubishi prototype power plant will not see immediate use.
Ironically, ABB and Mitsubishi developed the integrated gate commutated thyristor that's used for those frequency converters. https://en.wikipedia.org/wiki/Integrated_gate-commutated_thy...