Wednesday, July 01, 2009
in other news... Wind power!
I thought this was interesting.
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From http://arstechnica.com/science/news/2009/06/potential-in-the-wind-23-times-current-us-consumption.ars:
Potential wind power is 23 times current US electricity use
A trio of researchers have calculated the sort of yields we might see if the world took advantage of all the wind power available to it. It's a bit of a thought experiment, but the numbers are still impressive: 40 times the current global electric use.
By John Timmer | Last updated June 23, 2009 6:15 AM CT
When the National Academies of Science recently looked at the potential for renewable energy deployment in the states, its expert panel made some reasonable assumptions, such as limits imposed by manufacturing capacity and the current electric grid. This week, the NAS Proceedings will see the publication of a paper that considers what would happen if we dropped reasonableness from the analysis and calculated what we might achieve if we pushed wind power to its maximal capacity. The paper is an odd mix of these unreasonable assumptions and conservative estimates, and is probably best viewed as a sort of thought experiment. Still, the numbers that come out of the analysis are quite impressive: maxing out deployment of current-generation technology could produce five times the total energy used in the world today, and 40 times the electricity.
To a certain extent, this shouldn't be a complete shock. The amount of energy deposited on earth by the sun every year dwarfs any conceivable estimate of future energy use, and estimates are that as much as one percent of that winds up being converted to wind. The authors calculate that the fraction of wind energy that winds up on land is over 1014 watts, which is a lot to work with. The key question is how much of that to harvest.
The authors take the total land mass and subject it to a process of elimination. Areas permanently covered in ice are out, so Antarctica and Greenland have to go. Forests and densely populated areas are also out. But the authors supplement their land-based analysis with a second that considers offshore potential. There are plenty of ways to slice up the continental shelf when it comes to feasibility, but the authors keep things simple: the area has to be less than 200m deep, and within about 90km of the shore.
Obviously, wind energy isn't going to be evenly distributed across the areas that are left once this first pass is done, so the authors modified their model to take typical wind speeds into account. Typical global wind behavior was obtained from NASA's GEOS-5 system, with the wind values taken at 100m—the height of a current generation 2.5MW turbine (3.6MW turbines were assumed for offshore installation). Each turbine was given a quarter of a square kilometer footprint in order to limit their interference with the performance of neighboring units. Things like air density at altitude were also considered, and the utilization cutoff—the fraction of time that winds were strong enough to run the turbine—was set at 20 percent.
The authors produced a heat map of wind power capacity, which shows Greenland, the Amazon basin, and Central Africa whited out due to their ice cover or extensive forestation. The Great Plains of the US, the Russian steppe, and the tundra on the east side of Hudson Bay all have lots of potential, and the Patagonian grasslands positively glow. Divided up by nation, Russia comes out way ahead at over 118 PWh (Petawatt hours), with Australia in second at 86; Canada, the US, and Argentina round out the top five. Those same nations dominate the offshore potential as well, which adds another five to 25 PWh to their totals.
For the US, the total that could be generated within its territory is more than 23 times its current electricity consumption. By this measure, even China would have an 18-fold excess in production. If the world wanted to supply all its current electric needs, it could do so exclusively by relying on sites that could run turbines at full efficiency for up to half the year. To handle all its energy needs, it would only have to drop to sites with 36 percent efficiencies, about the same as the current typical install in the US.
Of course, the typical problems with renewable energy come out of this analysis as well. For starters, most of the generating capacity isn't where the people are, so long-distance transmission would be needed. By focusing in on the US, the authors detect two further issues. In the states, electrical use peaks in the summer, which happens to be the time where wind power hits its low point. The summer also turned out to be the time that the wind supply in three distant states (Minnesota, Montana, and Texas) showed the highest degree of correlation. This means that, when the wind stops blowing in one, it's likely to drop in the rest, too.
The last issue is that, at some level, putting this many turbines in place will undoubtedly change the dynamics of the lower atmosphere, with results that are probably difficult to predict.
Again, it's important to emphasize that this isn't being presented as a realistic plan to achieve a renewable energy nirvana; it's simply an attempt to provide a sense of what's possible. In the end, though, the study does make clear that supplying a lot of our energy via wind is possible, and that finding should inform debates about the degree to which it makes sense to do so and the adjustments we'll need to make to our existing energy systems in order to make it happen.
_____
From http://arstechnica.com/science/news/2009/06/potential-in-the-wind-23-times-current-us-consumption.ars:
Potential wind power is 23 times current US electricity use
A trio of researchers have calculated the sort of yields we might see if the world took advantage of all the wind power available to it. It's a bit of a thought experiment, but the numbers are still impressive: 40 times the current global electric use.
By John Timmer | Last updated June 23, 2009 6:15 AM CT
When the National Academies of Science recently looked at the potential for renewable energy deployment in the states, its expert panel made some reasonable assumptions, such as limits imposed by manufacturing capacity and the current electric grid. This week, the NAS Proceedings will see the publication of a paper that considers what would happen if we dropped reasonableness from the analysis and calculated what we might achieve if we pushed wind power to its maximal capacity. The paper is an odd mix of these unreasonable assumptions and conservative estimates, and is probably best viewed as a sort of thought experiment. Still, the numbers that come out of the analysis are quite impressive: maxing out deployment of current-generation technology could produce five times the total energy used in the world today, and 40 times the electricity.
To a certain extent, this shouldn't be a complete shock. The amount of energy deposited on earth by the sun every year dwarfs any conceivable estimate of future energy use, and estimates are that as much as one percent of that winds up being converted to wind. The authors calculate that the fraction of wind energy that winds up on land is over 1014 watts, which is a lot to work with. The key question is how much of that to harvest.
The authors take the total land mass and subject it to a process of elimination. Areas permanently covered in ice are out, so Antarctica and Greenland have to go. Forests and densely populated areas are also out. But the authors supplement their land-based analysis with a second that considers offshore potential. There are plenty of ways to slice up the continental shelf when it comes to feasibility, but the authors keep things simple: the area has to be less than 200m deep, and within about 90km of the shore.
Obviously, wind energy isn't going to be evenly distributed across the areas that are left once this first pass is done, so the authors modified their model to take typical wind speeds into account. Typical global wind behavior was obtained from NASA's GEOS-5 system, with the wind values taken at 100m—the height of a current generation 2.5MW turbine (3.6MW turbines were assumed for offshore installation). Each turbine was given a quarter of a square kilometer footprint in order to limit their interference with the performance of neighboring units. Things like air density at altitude were also considered, and the utilization cutoff—the fraction of time that winds were strong enough to run the turbine—was set at 20 percent.
The authors produced a heat map of wind power capacity, which shows Greenland, the Amazon basin, and Central Africa whited out due to their ice cover or extensive forestation. The Great Plains of the US, the Russian steppe, and the tundra on the east side of Hudson Bay all have lots of potential, and the Patagonian grasslands positively glow. Divided up by nation, Russia comes out way ahead at over 118 PWh (Petawatt hours), with Australia in second at 86; Canada, the US, and Argentina round out the top five. Those same nations dominate the offshore potential as well, which adds another five to 25 PWh to their totals.
For the US, the total that could be generated within its territory is more than 23 times its current electricity consumption. By this measure, even China would have an 18-fold excess in production. If the world wanted to supply all its current electric needs, it could do so exclusively by relying on sites that could run turbines at full efficiency for up to half the year. To handle all its energy needs, it would only have to drop to sites with 36 percent efficiencies, about the same as the current typical install in the US.
Of course, the typical problems with renewable energy come out of this analysis as well. For starters, most of the generating capacity isn't where the people are, so long-distance transmission would be needed. By focusing in on the US, the authors detect two further issues. In the states, electrical use peaks in the summer, which happens to be the time where wind power hits its low point. The summer also turned out to be the time that the wind supply in three distant states (Minnesota, Montana, and Texas) showed the highest degree of correlation. This means that, when the wind stops blowing in one, it's likely to drop in the rest, too.
The last issue is that, at some level, putting this many turbines in place will undoubtedly change the dynamics of the lower atmosphere, with results that are probably difficult to predict.
Again, it's important to emphasize that this isn't being presented as a realistic plan to achieve a renewable energy nirvana; it's simply an attempt to provide a sense of what's possible. In the end, though, the study does make clear that supplying a lot of our energy via wind is possible, and that finding should inform debates about the degree to which it makes sense to do so and the adjustments we'll need to make to our existing energy systems in order to make it happen.
# posted by John Colton @ 10:20 AM 
