But because typical renewable energy pays back the energy investment in about three years, if we just took the energy output of renewable energy and reinvested it, the amount of renewable energy production would grow at about 30% per year.
How many scarce materials would be needed? How much land area? How much toxic waste would be produced, e.g. from solar elecontronic components? Energy investment is not the only input needed for renewables.
(If you have a link that answers these and similar questions, that would be good.)
Thanks for the good questions. Wind power can use scarce materials, like rare earth permanent magnet generators. But it is possible just to use copper. Some photovoltaic technologies use scarce materials, but silicon is abundant.
US per person primary energy use is ~10 kW: Energy Information Administration. “Annual Energy Review 2007.” If we start with renewable electricity, we need less primary energy, 4-8 kW, so say 6 kW. So 10 billion people require 60 trillion watts (TW). Current wind technology could provide 72 TW: Archer, C. and M. Jacobson. “Evaluation of global wind power.” JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D12110, doi:10.1029/2004JD005462, 2005. Solar maximum on land is ~6,000 TW, but practical ~600 TW: Lewis, N.S. “Powering the Planet” California Institute of Technology presentation. If solar is 10% efficient and average solar radiation is 200 W/square meter, this requires ~0.1 acre/person: 5% of ecological footprint quota, but could be in desert or on rooftops.
Of course we need to be careful with toxic waste, but landfills take up a negligible amount of land.
How many scarce materials would be needed? How much land area? How much toxic waste would be produced, e.g. from solar elecontronic components? Energy investment is not the only input needed for renewables.
(If you have a link that answers these and similar questions, that would be good.)
Thanks for the good questions. Wind power can use scarce materials, like rare earth permanent magnet generators. But it is possible just to use copper. Some photovoltaic technologies use scarce materials, but silicon is abundant. US per person primary energy use is ~10 kW: Energy Information Administration. “Annual Energy Review 2007.” If we start with renewable electricity, we need less primary energy, 4-8 kW, so say 6 kW. So 10 billion people require 60 trillion watts (TW). Current wind technology could provide 72 TW: Archer, C. and M. Jacobson. “Evaluation of global wind power.” JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D12110, doi:10.1029/2004JD005462, 2005. Solar maximum on land is ~6,000 TW, but practical ~600 TW: Lewis, N.S. “Powering the Planet” California Institute of Technology presentation. If solar is 10% efficient and average solar radiation is 200 W/square meter, this requires ~0.1 acre/person: 5% of ecological footprint quota, but could be in desert or on rooftops. Of course we need to be careful with toxic waste, but landfills take up a negligible amount of land.