No Tech Magazine

Trees as Indicators of Prevailing Wind Direction

"In mountainous areas, winds are often complex and the available wind data are limited and provide little information on wind direction. One technique for determining the mean wind direction is tree flagging. Trees have been used for hundreds of years as an ecological indicator of wind direction, wind exposure and as a measure of the severity of wind and ice damage. This handbook will describe techniques for 'reading' the information written on the trees by wind."

"Flagged trees only reflect the prevailing wind direction of the strongest winds, which may occur during only part of the year. Seasonal variations in the wind have a pronounced effect on the type of wind deformation and these effects are characterized in this handbook. Techniques for estimating the mean annual wind speed have been developed using indices of wind effects on trees. These indices have been calibrated on two widely distributed species of conifers. The main conclusions are that trees provide a simple, inexpensive and quick method for identifying promising locations where more detailed measurements can verify the wind potential."

Trees as an indicator of wind power potential (.pdf), John E. Wade & E. Wendell Hewson, 1979.
Vegetation as an indicator of high wind velocity (.pdf), DOE report, John E. Wade & R.W. Baker, 1977

More low-tech wind power.

Wind Farms Can Be Made 10 Times Smaller

"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."

"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 Receding Horizons of Renewable Energy

"Widespread installed renewable electricity capacity would be a very good resource to have available in an era of financial austerity at the peak of global oil production, but the mechanisms that have been chosen to achieve this are clearly problematic. They plug into, and depend on, a growth model that not longer functions. If we are going to work towards a future with greater reliance on renewable energy, there are a number of factors we must consider. These are not typically addressed in the simplistic subsidy programmes that are now running into trouble worldwide.

We have power systems built on a central station model, which assumes that we should build large power station distant from demand, on the grounds of economic efficiency, which favours large-scale installations. This really does not fit with the potential that renewable power offers. The central station model introduces a grid-dependence that renewable power should be able to avoid, revealing an often acute disparity between resource intensity, demand and grid capacity. Renewable power (used in the small-scale decentralized manner it is best suited for) should decrease grid dependence, but we employ it in such a way as to increase our vulnerability to socioeconomic complexity.

Renewable energy is best used in situ, adjacent to demand. It is best used in conjunction with a storage component which would insulate consumers from supply disruption, but Feed-In Tariff (FIT) programmes typically prohibit this explicitly. Generators are expected to sell all their production to the grid and buy back their own demand. This leaves them every bit as vulnerable to supply disruption as anyone who does not have their own generation capacity. This turns renewable generation into a personal money generating machine with critical vulnerabilities. It is no longer about the energy, which should be the focus of any pubicly funded energy programme.

FIT programmes typically remunerate a wealthy few who install renewables in private applications for their own benefit, and who may well have done so in the absence of public subsidies. If renewables are to do anything at all to help run our societies in the future, we need to move from publicly-funded private applications towards public applications benefitting the collective. We do not have an established model for this at present, and we do not have time to waste. Maximizing renewable energy penetration takes a lot of time and a lot of money, both of which will be in short supply in the near future. The inevitable global austerity measures are not going to make this task any easier."

Read more at The Automatic Earth. Pictures credit.

Small wind turbines put to the test (2)

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."

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."

Windmills and Wind Motors - How to Build and Run Them (1910)

"I have endeavoured in the following pages not only to interest the practical amateur in a branch of mechanics unfortunately much neglected, but also to present a series of practical original designs that should prove useful to every reader from the youngest to the most advanced."

Chapter 1 : windmill evolution
Chapter 2 : a small working model windmill
Chapter 3 : a small American type windmill
Chapter 4 : a small working windmill
Chapter 5 : a practical working windmill
Chapter 6 : production of electricity by wind power

Windmills and wind motors - how to build and run them (1910).

Related: Wind powered factories / A wind-powered knitting machine / Scale models of Dutch Industrial Windmills / The home made windmills of Nebraska.

TimberTower: a High-Tech Wind Turbine, Made from Trees

Our article on industrial windmills appeared on The Oil Drum and, as could be expected, this generated many interesting comments. One in particular was made by a reader named "anyone", who sent in a link about a high-tech wind turbine placed on a tower made entirely of wood.

So while we suggested to redesign traditional windmills by using modern, high-tech materials, the German company TimberTower proposes the opposite: redesign modern wind turbines by using traditional, low-tech materials.

Large wind turbines are usually made of steel, and while they definitely deliver more energy over their lifetime than it takes to produce them (contrary to small wind turbines), using no energy at all would of course be even better - and cheaper.

Wood is easier to transport (the TimberTower is manufactured out of glued laminated timber panels which are assembled on-site), doesn't need to be mined, has no corrosion issues (think of offshore turbines), and it captures carbon. And while trees bend in strong winds, they usually don't break.

Using a timber tower for a 100 metre high wind turbine can save approximately 300 tons of sheet steel, writes the company at their website. One "TimberTower" also ties up approximately 400 tons of CO2. They say they can build them as high as 200 metres. Serial production should start in 2010. More:  TimberTower. Related: wooden pipelines, wooden bridges.

Kite Power

Italian company Kite Gen is building a full-scale 3 megawatt version (video) of its promising wind turbine concept, we learn from MetaEfficient. A large kite is drawn upward to altitudes around 800 metres, where average wind speeds are four times as strong as they are near ground-based wind turbines. The kites power turbines by rising and flying back to gound level continuously. The retrieval phase is said to require a small fraction of the power that is generated during the flight. A first prototype was built in 2006. One of the recent improvements is an automatic launching system, powered by fans. The technology generated an interesting discussion at the Oil Drum last summer. Previously: Floating windmills - energy from the clouds. Related: Kiteboating & Kite Aerial Photography.

The Folly of Building-Integrated Wind

"The study found that predicted performance exceeded actual performance by a factor of 15 to 17. With the worst-performing systems, the electricity required to run the electronics exceeded the electricity production, so the wind turbines were net consumers of electricity". Read.

Thanks, Brent Eubanks. Related: Small windmills put to the test / Urban Windmills harm the environment.