Despite the current economic travails, I read about the importance of renewable energy and wind power on an almost daily basis. But is it making such an impact? Should we bother researching it? The engineering challenges have been significant, but I am absolutely convinced that this technology is developing fast and will make a significant contribution. It may contribute directly to your career, or you may become involved in an industry supporting renewable energy. It may have an impact on your building or simply become a source of power for your next project. In any event, whatever discipline you work in, you will need to talk knowledgeably about it. So read on – it may be a worthwhile investment of your time. And I welcome comments from the experts amongst you. I will publish your feedback in the next newsletter.
%’s and dollars and cents
The windmills that Don Quixote used to tilt at are old fashioned, albeit aesthetically pleasing, have been around for thousands of years, but only generate a tiny amount of power. Wind turbines, on the other hand, have developed considerably since the early ‘80’s when they only had tens of kW capacity. The new machines have 1.5M to 2.5MW capacity. Globally, wind power produces only 1% of the world’s energy; but a significant amount for some countries such as Denmark (20%) and Germany (7%). In China, the capacity has doubled every year. Installations are expected to triple from 94GW (2007) to 290GW by 2012. By 2017, their share of total production could be nearly 6%. Stanford University (in 2000) estimated that the global wind-energy potential is five times the world’s total energy demand. Furthermore, costs are falling - from 30 cents per kWh in the early eighties to 10 cents per KWh in 2007. – However, it is still more expensive than for “filthier” methods of energy generation. But with a carbon tax, windpower would be immediately competitive.
Now to the technical nuts and bolts
Sunlight heats the earth and this heats the atmosphere. This results in hot air rising and cooler, heavier air blowing in to fill its place. Thus wind is everywhere. Wind turbines exploit aerodynamic lift (similar to aircrafts) to spin. On one side of the turbine the blade is curved and on the other it is almost flat - causing the air to flow more rapidly over the curved side and to create an area of low pressure which moves the blade. The blade causes a rotor to turn and then in turn a drive shaft. The drive shaft interfaces to a gearbox which increases the speed of rotation. This facilitates the production of electricity in the generator which is then fed into the grid.
The Danes ended up with a standard architecture of a three-bladed horizontal axis, upwind machine. The vertical axis machines (great for coping with variations in wind direction) were not considered to be as aerodymically efficient (as they move against the wind for half of the time). The two bladed rotors are not as dynamically balanced as the three-bladed rotors, making them harder to design. They also have to spin faster than the three bladed designs to extract a similar amount of energy and are thus noisier. And interestingly enough, people prefer the appearance of three-bladed rotors.
The latest generation of wind turbines extracts about 50% of the kinetic energy of wind. The theoretical limit is 59%.
The machines are growing in size. Onshore machines are typically up to 3MW in capacity and some prototype offshore machines are up to 10MW in capacity. Even though they can cost up to 40% more, offshore sites are preferred. - These generally have higher wind levels with less variation in wind speeds and they can be positioned near densely populated areas without being seen. Furthermore, they are away from people so noise is not an issue - this has resulted in the resurgence of the two bladed, cheaper designs.
Engineering out the challenges
A few challenges have emerged:
• There is public opposition to wind turbines because of the noise they generate, the fact that they can kill birds and interrupt the view
• Expensive new transmission lines are required to populated denser areas
• Wind power is not always available so other stand by sources must be available to handle the short falls when the wind isn’t blowing.
What to do next?
• Read and talk to your peers about the opportunities to harness this technology
• Look for ways of hooking your current services and products into the wind power technology market
• Look for opportunities to build wind farms
• Watch the developments of the climate change carbon tax which will result in the acceleration in use of this technology
Thanks to The Economist, DNV Global Energy Concepts, and the International Energy Agency (IEA) for references used above.
As Bertha Calloway remarks: ‘We cannot direct the wind, but we can adjust the sails’. And presumably not only the sails, but also the technology to take greater advantage of this marvelous and freely available power.
Yours in engineering learning