Wind Farms Can Be Made 10 Times Smaller

July 14, 2011 by kris de decker Filed Under: Wind Power, Wind turbines

Size of wind farms “Modern wind farms comprised of horizontal-axis wind turbines (HAWTs) require significant land resources to separate each wind turbine from the adjacent turbine wakes. This aerodynamic constraint limits the amount of power that can be extracted from a given wind farm footprint. The resulting inefficiency of HAWT farms is currently compensated by using taller wind turbines to access greater wind resources at high altitudes, but this solution comes at the expense of higher engineering costs and greater visual, acoustic, radar and environmental impacts.”

“We investigated the use of counter-rotating vertical-axis wind turbines (VAWTs) in order to achieve higher power output per unit land area than existing wind farms consisting of HAWTs. Full-scale field tests of 10-m tall VAWTs in various counter-rotating configurations were conducted under natural wind conditions during summer 2010. Whereas modern wind farms consisting of HAWTs produce 2 to 3 watts of power per square meter of land area, these field tests indicate that power densities an order of magnitude greater [21 to 47 watts] can potentially be achieved by arranging VAWTs in layouts that enable them to extract energy from adjacent wakes and from above the wind farm.”

Small wind farm “The results suggest an alternative approach to wind farming that has the potential to concurrently reduce the cost, size, and environmental impacts of wind farms.”

Read more: ‘Potential order-of-magnitude enhancement of wind farm power density via counterrotating vertical-axis wind turbine arrays’, John O. Dabiri. Introduction. Research paper (pdf). Via Ecogeek. 

The Homemade Windmills of Nebraska

May 12, 2011 by kris de decker Filed Under: DIY, Random, Sawing machines, Wind Power, Windmills

home made windmills of nebraska

“The merit of homemade mills has enjoyed such prompt recognition that they are going up daily. Not to the detriment, we are happy to say, of those important adjuncts to the farm, the shopmade mills, but in addition to them.

In a given community, the man who puts up the first mill generally furnishes the model for the rest of the community. Hence it seems the more desirable that good models should be at hand, the better models are often of quite as easy constructed and no more expensive than the poorer, and their efficiency considerably greater.

It is advantageous to have good models to copy, and the next best thing to the actual model is a good simple drawing. This is the first object of this paper on our homemade windmills; it aims to supply cuts illustrating all sorts of windmills, as found in this State.”

“The homemade windmills of Nebraska” (pdf), Erwin Hinckley Barbour, 1899. Illustration: a wind powered sawing machine.

Related: Windmills and wind motors – how to build and run them (1910), Building plans of Dutch Industrial windmills (1850).

Can Renewables Power Consumer Societies? The Negative Case

May 11, 2011 by kris de decker Filed Under: Energy, Renewables, Wind Power

“Virtually all current discussion of climate change and energy problems proceeds on the assumption that technical solutions are possible within basically affluent-consumer societies. There is however a substantial case that this assumption is mistaken. This case derives from a consideration of the scale of the tasks and of the limits of non-carbon energy sources, focusing especially on the need for redundant capacity in winter. The first line of argument is to do with the extremely high capital cost of the supply system that would be required, and the second is to do with the problems set by the intermittency of renewable sources. It is concluded that the general climate change and energy problem cannot be solved without large scale reductions in rates of economic production and consumption, and therefore without transition to fundamentally different social structures and systems.”

Read more: “Can renewables solve the greenhouse problem? The negative case” (pdf), Ted Trainer, Energy Policy, March 2010. Also check out the author’s website, where you can find similar papers, like this one.

How to Rig a Windmill Sail

January 10, 2011 by kris de decker Filed Under: Random, Wind Power, Windmills

how to rig a windmill sail

Source: “Travailler au moulin / Werken met molens”, Jean Bruggeman, 1996.

Tree Windmill (1901)

December 6, 2010 by kris de decker Filed Under: Random, Trees, Wind Power, Windmills

windmill treeLast year, William Kamkwamba made headlines around the world with his crude windmills built out of tree trunks and scavenged materials.

He could have saved himself some work if he had seen the illustration on the right, which I copied from a 1901 Dutch newspaper. The accompanying text says:

“Windmills are ugly contraptions and many attempts have been made to make them look better. This illustration shows how nature and mechanics can coexist.”

“It is a windmill constructed in combination with two trees. The trees only serve as a support for the upper part and for the ladder to reach the top. The mill was built in Illinois (US) and worked so well that several have been constructed.”

I could not find any more information about it.

Small wind turbines put to the test (2)

September 15, 2010 by kris de decker Filed Under: Wind Power, Wind turbines

The Oil Drum runs an extended and rewritten version of our 2009 article on small wind turbines – including additional tests results from the UK.

“Two real-world tests performed in the Netherlands and in the UK confirm our earlier analysis that small wind turbines are a fundamentally flawed technology. Their financial payback time is much longer than their life expectancy, and in urban areas, some poorly placed wind turbines will not even deliver as much energy as needed to operate them (let alone energy needed to produce them). Given their long payback period relative to their life expectancy, most small wind turbines are net energy consumers rather than net energy producers.”