Alternative Energy

Now we know that oil reserves are not going to last forever we are searching for alternative energy resources keenly. We are reading about new ways to tap energy from renewable resources. Sometimes these alternative energy resources seem quite odd and impractical. But we never know how they will shape up in future or how they will perform in future. Imagine New York being lit up by high-flying kites in the sky! These kites are supposed to utilize the wind power of New York.

Scientists at the Carnegie Institution and California State University are exploring the above mentioned possibility. They are considering New York as the prime location for exploiting high-altitude winds. Their estimate is that high-altitude winds contain enough energy to meet world demand 100 times over. The researchers have marked the eastern U.S. and East Asia as best suited for wind harvesting. Though, they have to think about the wind fluctuations.

Scientists of the Carnegie Institution and California State University were taking the help of twenty eight years of data from the National Center for Environmental Prediction and the Department of Energy. Ken Caldeira of the Carnegie Institution’s Department of Global Ecology and Cristina Archer of California State University, Chico, compiled the first-ever global survey of wind energy available at high altitudes in the atmosphere. The researchers evaluated the potential for wind power in terms of “wind power density.” Wind power density takes into account both wind speed and air density at different altitudes.

“There is a huge amount of energy available in high altitude winds,” said coauthor Ken Caldeira. “These winds blow much more strongly and steadily than near-surface winds, but you need to go get up miles to get a big advantage. Ideally, you would like to be up near the jet streams, around 30,000 feet.”

Ken Caldeira is talking about jet streams. Jet streams are relatively narrow bands of strong wind at altitudes between 20 and 50,000 feet in the upper levels of the atmosphere. Jet winds shift seasonally. But they are persistent features in the atmosphere. Jet stream winds are usually steadier and 10 times faster than winds near the ground. So we can safely conclude that they are a good source of clean and green energy. Several technological projects have been planned to harvest this energy. Scientists think that tethered, kite-like wind turbines could be utilized to produce power. By employing the current technology we can generate up to 40 megawatts of electricity and transmit it to the ground via the tether.

Lead author Archer informs us, “We found the highest wind power densities over Japan and eastern China, the eastern coast of the United States, southern Australia, and north-eastern Africa. The median values in these areas are greater than 10 kilowatts per square meter. This is unthinkable near the ground, where even the best locations have usually less than one kilowatt per square meter.”

Tokyo, New York, Sao Paulo, Seoul, and Mexico City fall in the category of high altitude wind belt. Archer elaborates, “For cities that are affected by polar jet streams such as Tokyo, Seoul, and New York, the high-altitude resource is phenomenal. New York, which has the highest average high-altitude wind power density of any U.S. city, has an average wind power density of up to 16 kilowatts per square meter.”

Tokyo and Seoul can be put under the area of high wind power density because they are under the influence of the East Asian jet stream. Mexico City and Sao Paulo are situated at tropical latitudes, so they are at a disadvantage. They rarely get affected by the polar jet streams. Sometimes they are affected by the weaker sub-tropical jets. Therefore they have lower wind power densities than the other three cities.

Caldeira points out the sore spots of jet streams, “While there is enough power in these high altitude winds to power all of modern civilization, at any specific location there are still times when the winds do not blow. Even over the best areas, the wind can be expected to fail about five percent of the time. This means that you either need back-up power, massive amounts of energy storage, or a continental or even global scale electricity grid to assure power availability. So, while high-altitude wind may ultimately prove to be a major energy source, it requires substantial infrastructure.”

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