Just how much land does solar power need
Our story about a journal article in which Jesse Ausubel argues that renewable energy generation would be a disaster for the environment, because it requires the use of lots of land, really sparked debate.
Among the comments on the associated blog was one from Matthew ? thanks! drawing our attention to a possible error in Ausubel?s calculations for how much land area solar power takes up. So let s do the maths.
I fear that the solar patagonia fleece sale wholesale1panel calculations are off by an order of magnitude (or my own calculations are off by the same). One 80 watt panel is 48 by 22 , which yields a constant (24 hour) output of roughly 40 watts in sunny climes. So, one 40 watt yield solar panel is 0.00000026304 square miles. And 0.00000026304(100010001000)/40 = 6.576 square miles.
In his PVs remain stuck at about 10% efficiency, with no breakthroughs in 30 years. Today performance reaches about 5 to 6 watts per square metre. But no economies of scale inhere in PV systems. A 1000 MWe PV plant would require about 150 square kilometres plus land for storage and retrieval.
We then showed both of these calculations to John Turner, a solar power specialist at the US government?s National Renewable Energy Laboratory. He found fault with both sets of calculations:
Well they are both off, but Ausubel is way, way off. patagonia store austinIf we assume a 1000 MWe electrical generation plant, and we assume it runs 24/7 for the entire year (no down time), then that plant will generate about 8.8 billion kilowatthours per year. So we need to calculate the size of a PV array that will generate the same kW hrs.
Assuming the average US solar resource of 1800 kW hr/m2 year [how much the sun shines] and a PV system efficiency of 10%, one square meter of PV would generate about 180 kW hr/year. Therefore you would need about 48.7 million sq meters or 48.7 square kilometers. That?s 18.8 square miles.
For the sunny southwest, we have a yearly average solpatagonia alpine guide pants men'sar resource of 2300 kWh/m2. Again assuming a 10% PV system efficiency, then that would produce about 230 kWh/m2 year. So for this array, you would need 38 million sq metpatagonia fleece sale wholesale3ers or 38 sq km. That is 14.7 square miles.
This is why it is so very important to be correct with the numbers the future of our society depends on energypatagonia outlet store locations and we need to get this right! Also, PV has not been stagnating current panel efficiency is running close to 15%, which will of course reduce those areas.
In a follow up phone conversation, Ausubel stood by his figures:
My calculation is right. I looked at actual existing facilities and what they produced in recent years. It?s not an argument of what is the best possible performance of any of these technologies.
Your comments are welcome, as ever.
Phil McKenna, New Scientist correspondentAll comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please let us know, quoting the comment in questionew patagonia infant down sweater buntingn.
Hmmmm. my calcs, based on John Turner s figures yields 340.7 sq Km.
By Chemikazi on July 27, 2007 1:53 PM
I don t see how you can get 340.7 sq km from John Turner s figures. It s just a simple division:a=total power to be generated =8.8 billion kWh per yearb=power per unit area =230 kWh per sq m per yeara/b=area needed =(8.8 billion/230) sq m =38.3patagonia outlet online shopping million sq m =38.3 sq kmThat s the final number John Turner quoted. If you want to say there is something wrong with his assumptions, then you can tell what exactly you would change and why, but his arithmetic is correct. Ausubel s assumptions seem as flawed as his mathematics.1. When dealing with a rapidly advancing technology, one should not base their speculations on either the past or current state of the art. Neither should policy be based on wildly unrealisitic projections of technology improvements. The measured pace of improvement is slow and steady. The cost per watt of photovoltaics will continue to decrease as efficiency increases and manufacturing costs decrease. This technology has not had the advantage of the massive subsidies the nuclear industry has enjoyed starting with the Manhattan project nor the historic tax breaks and lease subsidies granted the coal and oil industries (at least in the US).2. One patagonia discount code sportsof the major advantages of photovoltaics is the decentralization of electricity production. How many square kilometres of rooftops are there? Let s start using them.3. The long running disaster from the increase in strip miningpatagonia expedition race 3 full and burning coal continues climbing to a level beyond our current comprehension with no end in sight.4. The price of nuclear power never takes into account the costs of storing and disposing of the waste products. The half life of plutonium (one of the most acutely toxic poisons known) is about 20,000 years. Rendering radioactive materials harmless typically requires a period of 10 half lives. These years and cost are so great, so beyond mortal comprehension, nuclear power advocates choose to ignore it. Just because these advocates refuse to assign a cost to disposal doesn t meapatagonia everlong review 5 linxn there isn t one.5. Conservation and education still offer the highest cost/benefit in the world energy equation.
By peter on July 27, 2007 3:30 PM
Tpatagonia fleece sale wholesalehis is one of the problems with wind and solar things are highly variable and dependent on location, weather, and of course technology. And why assume that photovoltaic is the way to go for large scale electrical generation? If anything it s one of the least efficient and more costly ways to generate electricity. With present technpatagonia guide jacket that zipsology photovoltaics are great for low power remote applications. At the industrial scale it s much more cost effective to use a solar tower generator with mirrors concentrating solar energy onpatagonia fleece sale wholesale0 the tower. This is what they ve done in Spain and the design even allows stored heat to generate some electricity at night after the sun has gone down. Eventually thpatagonia fleece sale wholesale2at system is expected to generate 23 GWh of electricity per year when fully developed in the next decade.
In his 27 July post, Peter makes some great points, but I must disagree with his simplistic criticism of nuclear power. He assumes, based upon present reactor designs, that plutonium (Pu) can never be used as a fuel. But there is no intrinsic reason for this; therefore, Pu does NOT need to be stored as waste for 200K years. Although Pu s natural decay half life is 20K years, under the right conditions it can undergo fission much more rapidly.
