5 ms·

> New solar cells can sometimes take greater than the life of the product to recoup the energy spent on creating them. If you live in, say, Massachusetts [...]

by jsrn 17y ago

> New solar cells can sometimes take greater than the life of the product to recoup the energy spent on creating them. If you live in, say, Massachusetts [...] you'll probably never net an energy savings. "False. The energy yield ratio (the ratio of energy delivered by a system over its lifetime, to the energy required to make it) of a roof-mounted, grid-connected solar system in Central Northern Europe is 4, for a system with a lifetime of 20 years (Richards and Watt, 2007); and more than 7 in a sunnier spot such as Australia. (An energy yield ratio bigger than one means that a system is A Good Thing, energy-wise.) Wind turbines with a lifetime of 20 years have an energy yield ratio of 80." source: http://www.inference.phy.cam.ac.uk/withouthotair/c6/page_41.shtml http://www.inference.phy.cam.ac.uk/withouthotair/c6/page_41.... (I assumed that the sun in Central Northern Europe shines with an intensity similar to the intensity in Massachusetts.)

ivankirigin 17y ago
Thanks for the info.
randallsquared 17y ago
Wait, your data imply that wind turbines pay for themselves in ~3 months. This is definitely not the case for the vast majority of turbines and locations, so 80 seems far too high.
- jsrn 17y ago
  > your data imply that wind turbines pay for themselves in ~3 months. No, it doesn't imply that - the data just imply that the energy needed to build the wind turbine is recouped after 3 months. Energy cost to build something != Cost to build something. In the case of the wind turbine, consider: R&D costs, material costs, marketing costs, etc.
  - ars 17y ago
    Not correct. Energy is exactly equal to the cost. Material costs: why does stuff cost? Because it takes energy to make it, and to transport it. R&D, marketing: You have pay someone. Why does he need money? Because he spends it on things that cost energy to make. Follow it all the way down and energy is exactly equal to cost. (Note that energy is not equal to environmental harm, which also needs to take into account pollution, which is not reflected in the cost.)
    - jsrn 17y ago
      > Energy is exactly equal to the cost. Ok, what does that mean? In physics, if something is exactly equal to an amount of energy, it has to be measured in the same unit as energy (joule). But cost is measured in dollars (or some other currency). So the above statement makes no sense. > why does stuff cost? Because it takes energy to make it, and to transport it. That is a factor for cost, but not the only factor. > R&D, marketing: You have pay someone. Why does he need money? Because he spends it on things that cost energy to make. By this argument, a product takes more energy to produce if the workers negotiate a better wage - because after work, they spend their extra money on something that costs energy to make. I'm not convinced that this makes sense. Taken to the extreme this would mean: A product made by unpaid volunteers takes far less energy to produce than an equivalent product made by paid workers.
      - ars 17y ago
        Energy is measured in dollars, not just in joules, so yes, energy and cost are equivalent. > That is a factor for cost, but not the only factor. Actually, yes it is. It's the only factor. Name any other factors, and I'll show you how each one actually boils down the to the energy used for it. > By this argument, a product takes more energy to produce if the workers negotiate a better wage - because after work, they spend their extra money on something that costs energy to make. Correct. Real world example: Americans use a lot more energy per capita then Chinese. Americans earn a lot more per hour then Chinese. Check if you like, in every area $/h = energy/capita > A product made by unpaid volunteers takes far less energy to produce than an equivalent product made by paid workers. Also correct. Think of a dorm with lots of volunteers. It costs far less energy to house and feed them than 10 separate houses. Since they have no money, they buy nothing. Since they buy nothing, no one spends energy making things for them. An important note: Just because it uses less energy doesn't mean it's better! A slave uses very little energy, but is obviously bad.
        ars 17y ago
        If someone has time, perhaps they could take the data from: http://en.wikipedia.org/wiki/List_of_countries_by_energy_consumption_per_capita http://en.wikipedia.org/wiki/List_of_countries_by_energy_con... http://en.wikipedia.org/wiki/List_of_countries_by_GNI_(PPP)_per_capita http://en.wikipedia.org/wiki/List_of_countries_by_GNI_(PPP)_... http://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nominal)_per_capita http://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nomin... http://en.wikipedia.org/wiki/List_of_countries_by_GNI_(nominal)_per_capita http://en.wikipedia.org/wiki/List_of_countries_by_GNI_(nomin... And see how well they correlate.

by jsrn 17y ago

ivankirigin 17y ago

Thanks for the info.

randallsquared 17y ago

Wait, your data imply that wind turbines pay for themselves in ~3 months. This is definitely not the case for the vast majority of turbines and locations, so 80 seems far too high.

jsrn 17y ago
> your data imply that wind turbines pay for themselves in ~3 months. No, it doesn't imply that - the data just imply that the energy needed to build the wind turbine is recouped after 3 months. Energy cost to build something != Cost to build something. In the case of the wind turbine, consider: R&D costs, material costs, marketing costs, etc.
- ars 17y ago
  Not correct. Energy is exactly equal to the cost. Material costs: why does stuff cost? Because it takes energy to make it, and to transport it. R&D, marketing: You have pay someone. Why does he need money? Because he spends it on things that cost energy to make. Follow it all the way down and energy is exactly equal to cost. (Note that energy is not equal to environmental harm, which also needs to take into account pollution, which is not reflected in the cost.)
  - jsrn 17y ago
    > Energy is exactly equal to the cost. Ok, what does that mean? In physics, if something is exactly equal to an amount of energy, it has to be measured in the same unit as energy (joule). But cost is measured in dollars (or some other currency). So the above statement makes no sense. > why does stuff cost? Because it takes energy to make it, and to transport it. That is a factor for cost, but not the only factor. > R&D, marketing: You have pay someone. Why does he need money? Because he spends it on things that cost energy to make. By this argument, a product takes more energy to produce if the workers negotiate a better wage - because after work, they spend their extra money on something that costs energy to make. I'm not convinced that this makes sense. Taken to the extreme this would mean: A product made by unpaid volunteers takes far less energy to produce than an equivalent product made by paid workers.
    - ars 17y ago
      Energy is measured in dollars, not just in joules, so yes, energy and cost are equivalent. > That is a factor for cost, but not the only factor. Actually, yes it is. It's the only factor. Name any other factors, and I'll show you how each one actually boils down the to the energy used for it. > By this argument, a product takes more energy to produce if the workers negotiate a better wage - because after work, they spend their extra money on something that costs energy to make. Correct. Real world example: Americans use a lot more energy per capita then Chinese. Americans earn a lot more per hour then Chinese. Check if you like, in every area $/h = energy/capita > A product made by unpaid volunteers takes far less energy to produce than an equivalent product made by paid workers. Also correct. Think of a dorm with lots of volunteers. It costs far less energy to house and feed them than 10 separate houses. Since they have no money, they buy nothing. Since they buy nothing, no one spends energy making things for them. An important note: Just because it uses less energy doesn't mean it's better! A slave uses very little energy, but is obviously bad.
      - ars 17y ago
        If someone has time, perhaps they could take the data from: http://en.wikipedia.org/wiki/List_of_countries_by_energy_consumption_per_capita http://en.wikipedia.org/wiki/List_of_countries_by_energy_con... http://en.wikipedia.org/wiki/List_of_countries_by_GNI_(PPP)_per_capita http://en.wikipedia.org/wiki/List_of_countries_by_GNI_(PPP)_... http://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nominal)_per_capita http://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nomin... http://en.wikipedia.org/wiki/List_of_countries_by_GNI_(nominal)_per_capita http://en.wikipedia.org/wiki/List_of_countries_by_GNI_(nomin... And see how well they correlate.