Floating Wind Power
Floating wind turbines will be located where the wind is best. Manufacture of the towers, nacelles, and blades is international and highly competitive. But there is room for innovation in making the floating foundations. Concrete is cheap and provides welcome inertia in tossing seas. Large concrete foundations manufactured at waterside rock quarries could be made economically and would provide the desired stability. We explore that idea here.
Cheap Electricity from Offshore Wind
Further offshore has the best wind. The water is deep there, so the wind turbines must be floating. Floating offshore wind could power the whole world - many times over. The only way to realize that huge potential is to make it cheap. Here are several ideas that could bring the cost down.
A rowboat in a storm is tossed about; an aircraft carrier much less so. Mass has a stabilizing effect. The heavier our foundation, the more inertia to resist movement. Conclusion: big heavy foundations can resist oscillation better than lighter foundations. We might naturally think of concrete. It is heavy, cheap, and readily available most everywhere.
Let’s get an idea as to scale:
The International Energy Agency has designed the “IEA 15 MW Reference Wind Turbine”. The turbine blades would be 117 meters (384 feet) long. The steel tower would be 6 to 10 meters (32 feet) in diameter and 150 meters (492 feet) in height. Weight would be about 2,000 metric tons.
As turbine size increases, electrical output increases per dollar of investment. Bigger is thus cheaper. On land, trucking of giant components is prohibitive. But, floating foundations and components transported by ships, scales easily. Our candidate concrete foundation would be an hexagonal platform with an array of six hollow cylinders providing flotation (sketch available). It would weigh approximately 10,000 metric tons.
How could this be cheap?
It is made at an aggregate plant located on the coast. With the aggregate sourced nearby, and mixed with ship delivered cement, we would have the cheapest concrete anywhere. To enthuse environmentalists, cement could be supplied from the "greenest" source worldwide.
The foundation would be built on a slightly sloped casting bed. Once semi-cured, it could be post-stressed and jacked off the casting bed onto into the adjacent deep water. Many foundations could be stored, floating nearby.
There are not many waterside rock quarries. And those few may not have dock and storage space to receive shiploads of components. To minimize logistics, it would seem most economical to transport each manufactured foundation directly to its final permanent location. Once there it would be permanently tied in place.
The wind turbine components would be arriving by ship from around the world. The turbines could be assembled complete at established harbors where dock space, storage space, and skilled workers are available.
Transporting a 600+ foot high wind turbine in the upright position would be hazardous. It would be better not to catch too much wind until anchored. And, some suitable harbors have limiting bridges (Golden Gate Bridge). Vertical transport seems impracticable.
For convenience of assembly and subsequent ease of transport the turbines could be assembled in the horizontal position onto special transport vessels. Those vessels would transport the turbine in the horizontal position directly to their permanent locations.
At the final location, with a series of simple moves, the turbines could be connected to the in-place foundation, pivoted to the vertical, and bolted into final position. (No giant seagoing crane required.)
Economical Dockside Assembly:
The wind turbine tower would be assembled whole at dockside. A large dockside crane would place the assembled tower onto a padded cradle on the transport barge (see sketch). Next, the male half of the temporary hinge would be bolted to the tower base. (The female half would have been previously bolted to the foundation at the foundation manufacturing site). Next the nacelle, with its axis near vertical, would be bolted onto the tower. The blades would be bolted on semi-horizontally. The low assembly elevation and stable dockside location makes these operations much easier than with a crane-ship at sea.
The transport barge takes the completed turbine horizontally to its permanent location in the wind turbine array. It feeds the male hinge half into the female hinge half on the foundation. Hydraulically activated hinge pins make the connection. Using its large sea-water hydraulic cylinder, the transport barge erects the turbine at its final location (see figures 1 and 2).
Economical Seabed Anchorages
Another important element of cost is anchoring the spar’s guy lines to the seabed. Piling and giant steel ship’s anchors are commonly used. But more economical would be steel rods cemented deep into the seabed. A self-propelled autonomous underwater drill rig could drill high strength steel rods over 100 feet long into the seabed (drill rig sketch available). They would be cemented deep into the underlying strata. In this way, it is the weight of the seabed that holds the wind turbines in place.
Another option is to manufacture heavy concrete bins at the same facility that manufactures the foundations. The anchor bin bottom would be customized to the seabed. The bins would be sunk at the vertices of the turbine array, and then filled with rock. Each rock bin could restrain four anchor lines.
With the Climate Crisis looming, electricity supply agencies around the world want Green Energy Now. But, as it stands today, the timing of permissions is frustratingly indeterminant. When permission finally comes the pent-up need then still requires more waiting for manufacture. There is entirely too much waiting. An alternative to such waiting is Windmill Stores.
Synopsis: Some far-seeing and well financed wind development organization commences the mass production of large floating wind turbines. They build a stock of giant foundations and float them in storage. They order and stock all the components lined up within crane reach of dockside. These turbines would be ready-to-go. This might be financed by philanthropies, hedge funds, pension funds, sovereign wealth funds, or any other shrewd deep pockets. The most visionary of the oil majors might be likely.
Windmill Stores, by offering immediate availability, could corner the market. Profitability could be assured. More importantly, they would help abate the Climate Crisis. After struggling through permitting, financing, and all the other delaying hindrances what organization, we ask rhetorically, wants to additionally wait through turbine ordering and fabrication? Perhaps none, not when the Windmill Store offers immediate delivery.
In electricity starved regions around the world, in regions considering diesel, gas, or (still) coal, offshore green power immediately available might swing their choice. Just call the Windmill Store and, in a few days, your very own Giant Wind Turbines will be headed straight to your offshore location.
Immediate availability would incentivize orders. Lots of orders would require mass production. Mass production generates profits and instigates low prices. The Model T got cheaper every year as Henry Ford got rich. The country that pioneers Windmill Stores could become the Saudi Arabia of wind.