According to the latest edition of Sierra Magazine (Mar/Apr 2013), wind power has finally made significant progress in the US energy mix. Up to the year 2000, total US wind power output had stayed unchanged around 25,000 megawatts. By 2012, wind output had multiplied to 250,000 megawatts (one megawatt delivers electricity for about 250 homes).
Which states rank highest in wind production? Texas comes first (10,394 megawatts), followed by Iowa (4,322), California (3,917), Illinois (2,718) and Minnesota (2,673). Note that Texas is an oil state, and Iowa is a farm state known for its recent oil boom. These two top wind producers are not especially friendly to alternative energy. Nevertheless, wind now accounts for 20% of total energy supply in Iowa, which puts the state second in the world after Denmark’s 28%.
How can the wind industry manage to compete? Geography plays the most important role because the wind must blow where it used to. Furthermore, with the advance in technology, wind energy has now achieved a lower cost per megawatt-hour (ranging from $48 to $95), as compared with natural gas ($61 to $89) and coal ($62 to $141).
Along the wind corridor of the US stretching from north to south, the following states have already achieved 8% or more of wind power in total energy supply: Iowa, Minnesota, Wyoming, North Dakota, South Dakota, Colorado, Kansas, Idaho, and Oregon. One study estimates that the US has the potential of producing 4 billion megawatts of wind energy in the hinterland away from population areas.
Driving through the Altamont Pass in central California, you can see one of the oldest and largest wind farms in the world built in the 1970s in response to the first oil crisis. Among the 5000 turbines erected, the new ones stand side by side with the old showing the big differences in technology. The new turbine is 650 feet tall with three carbon-fiber blades each longer than the wingspan of a 747 aircraft. It produces 3 megawatts of power. By contrast, the old turbine is only 75 feet tall and produces 0.065 megawatts.
A big wind farm normally comprises hundreds of horizontal-axis turbines where the blades are vertically mounted on a horizontal drive shaft to face the wind. The electricity generator is housed at the top of the turbine tower together with the drive shaft. On a much smaller scale, a newer turbine of vertical drive shaft is available to power a housing unit rather than a town. Its size is about that of a small tree. In this case, various designs are used instead of long blades to catch the wind. The electricity generator is placed at the bottom of the turbine, making it much easier to install. This design catches the wind whichever direction it blows but with much less electricity output. Given these two different designs, the future wind farm will comprise groups of small vertical-axis turbines situated between the required large distances separating the huge horizontal-axis turbines. This hybrid configuration will make better use of wind farm space. It will also increase the efficiency of electricity production by capturing the convoluted airflows between the huge turbines.
Wind power is the oldest energy source second only to muscle power for moving around, especially on water. After being distracted by fossil fuels for the last few centuries, humans have finally come full circle to rediscovering the power of the wind, this time for electricity generation. Although wind energy is non-polluting and renewable, two hurdles must be overcome: First, the wind does not blow with the same intensity all the time. Second, how to store and transmit the electricity generated for the consumers both near and far? Note that similar problems apply to solar energy, too.
The first problem cannot be solved by technology, but will be solved in due course. Why? When more wind farms and individual small turbines are built and spread over a wide region, the problem will naturally be reduced because the wind must be blowing somewhere and caught by some wind turbines there. To transport the electricity generated to a no-wind area, it depends on how we manage to solve the second problem.
The second problem involves electricity transmission and storage, both requiring heavy investment in technology. Electricity generated must be stored or transmitted to where needed. If not used, it will be lost. A so-called smart grid enables electricity to flow efficiently in both directions between consumers and generators to even out the distribution. Most of the existing grid is not smart because electricity only flows in one direction. Moreover, the generators do not have real-time monitor and control over the flow. Regarding electricity storage, we have to rely on battery technology and other storage possibilities. Electric batteries have made great leaps in terms of weight and storage capacity. However, the lithium battery of the electric car still cannot compete with gasoline due to the limited driving range of less than 200 miles between recharge.
There exist other possibilities for electricity storage depending on geography. Some utility companies use the surplus electricity to compress air into a natural large cave. When needed, the cave will be depressurized to drive a turbine that generates electricity. In the American northwest region where rain is plentiful, some utility companies use the surplus electricity to pump rainwater from a lower reservoir to a higher one. When needed, the water will run back down to the lower reservoir to drive a turbine producing hydro electricity. Recently, a German company has found a new way to transport electricity in the form of a gas. The method involves first splitting water into hydrogen and oxygen using the surplus electricity. Then the hydrogen will combine with the carbon dioxide in the air to form methane (CH4). Now methane is easily stored and transported by means of the existing infrastructure for natural gas. It will be burned in a combustion turbine to generate electricity when needed.
The second hurdle regarding transmission and storage will be overcome in the not-too-distant future. Maybe a technological breakthrough will happen sooner. Wireless recharge of your cell phone battery is happening nowadays. Can this be extended to recharging an electric car running on the road, or a house in the middle of nowhere? The answer is yes but we don’t know when. When that time comes, the handicap of electricity transmission and storage for the consumers will largely disappear.