ALTERNATE ENERGY: Getting more power out of the wind

Hydrautrans BV’s crane, for bigger, better wind turbines.

Power production by wind is accelerating across the globe. Annual growth is above 25%. The U.S. National Renewable Energy Labs predicts that offshore wind will have the cumulative capacity of 500 gigawatts — the equivalent net output of about 200 nuclear power plants or about 500 coal-powered plants — by 2050.
The next step in wind turbine technology is to create longer turbine blades and taller towers. Capturing the wind is the name of the game. The bigger the better. With wind, size matters. Getting up where the wind is the strongest makes wind power energy more viable. Creating the larger wind turbine is easier said than done, however, especially when we are talking offshore.

In the Netherlands, there are plans to build the largest array of offshore’s most powerful wind turbines in the world. These turbines, I believe, will be certified cancer free too. As wind turbines become more powerful, size and height are everything. However, as they get taller and the propellers longer, the turbine hub called the nacelle gets heavier.

Building these new turbines is a challenge. The size and weight of these turbines are mind boggling. Compound that with the components that have to be assembled offshore. Each unit has to be brought in by ship. Now add a 600-ton nacelle, 200-ton rotor that is 680 feet in diameter, the lift equipment that can go vertical 560 feet, then tack on the omnipresent winds. It’s all an engineering marvel.

When the weather turns rough you can’t just run to the nearest shelter, making planning critical. For example, if someone is injured it’s at least a 3-mile ride back to shore, on one of the roughest shorelines in Europe or a ride in a helicopter if the winds aren’t too rough. The seas can kick up at any time, and they don’t care if you’re in the middle of a rotor lift.

With the enormous increase in weight, blade length, and the nacelle capturing energy from the wind comes the reality of physics. Greater wind speed means greater energy captured. This is the reason for higher heights and longer turbine blades.

Enter the new drive train HDT super solution.
The company Hydrautrans BV in Utrecht, the Netherlands, is trying to meet the demand for higher output wind machines. It is developing a 12 megawatt mechanical-hydraulic drive train to meet the needs of the next generation wind farm. Most wind turbines operate around 5-7 megawatts, but over 10 megawatts is where the challenge really starts.

Now we have to get a little techie! Technologically speaking, wind turbine components are fairly straightforward. You have the large blades that convert the motion of the air currents into horizontal mechanical energy, which turns a generator. This is no different, in effect, than the alternator in your car which converts the rotary motion of your engine into electrical power. Your car, however, produces AC which is turned in to DC while the opposite is true for large-scale wind turbines.

The tricky part is the dynamics of the wind turbine at these higher outputs. When the preferred output rises so does the stress on the mechanics of the nacelle. At the higher outputs, the mechanical gear boxes are prone to breakdown. Direct drive systems, no gearboxes, which use the slow rotational speed direct to the generator add weight exponentially as they must handle high currents at lower voltages which are then converted to AC. The efficiency of the direct drive is compromised by the increased weight and losses in electronic conversion to the required electrical characteristics required by the end user.

Hydrautrans CEO Ernst van Zuijilen believes his company has the answer: the HDT transmission. This is the hybrid Hydrautrans Drive Train. In my humble opinion, this is a very clever power transmission. It uses what is called Floating Cup Technology (FCT) developed by INNAS BV Breda, also in the Netherlands. The FCT eliminates metal-to-metal contact thus reducing friction and wear. This unique system operates four hydraulic motors that in turn drive the generator. What is key here too, is the high scalability of this drive train. It promises to handle 15-20 megawatt units for the future.

Wind turbine installation, especially at sea, is a marvel of engineering. Along with Hydrautrans, the Mammoet Company has developed a self-mounting crane system that can lift loads of 250 tons without the need for a large and extremely expensive jack-up installation vehicle. This alone is a major benefit in the construction of wind turbines.

In conclusion, the future of wind power generation lies in the ability to design systems with the intrinsic limitation of the physics of the materials, location of prevailing winds as well as the diminishing return of energy vs. cost of construction. Capturing larger and larger wind area is the only significant remaining thing that can improve wind turbines. Building and installing these new turbines are the two remaining challenges. Hydrautrans is on the right track, though, the complete large scale unit has yet to be built. There is the marketing issue of convincing current wind turbine investors that this new and yet untested technology is worth the trade off against conventional modes of wind power generation. Hydrautrans is optimistic that its design will be the investor’s choice when the prototype is completed in 2023.

I invite readers to take a gander at a YouTube video of how these present day turbines are installed at sea. It’s an eye opener!

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