Is Renewable Energy Adequate for Our Needs?

Ignoring intermittency and assuming that land acquisition for collectors and transmission lines is possible, that adequate exotic materials are available for manufacturing collectors, and cost is no object, with today’s technology how large an aggregate system would be required to convert from fossil/nuclear to 12 terrawatts of renewables for 6 billion people now? How large for 18 terrawatts in 2050, with 9.4 billion? Using existing data, the best possible case for solar thermal or photovoltaic is now approximately 6 watts per square meter and it will not get much better until major collection areas move closer to the equator. Thus, solar arrays totaling 2 trillion square meters – the area of Texas, New
Mexico, Arizona, California and Nevada – are needed now, and 3 trillion square meters – add Utah, Colorado, Nebraska, Kansas, and Oklahoma – in 2050. Wind farms, using NREL’s 10 blade diameter unit spacing recommendation to define the perimeter of the farm, would require 10 trillion square meters now, and 15 trillion in 2050 – five times the area requirement for solar collectors although land between the turbines can be shared. This example, using the western United States, only gives a notion of the size of collector areas scattered over the earth. Acquiring or confiscating that much real estate is not very likely, but only 45 percent of the earth’s land mass lies between the Tropics – optimum solar collectors must be built on one sixth of the total global area. Simple arithmetic indicates that exclusive use of renewables cannot support energy demand much beyond the 18 terrawatts needed in 2050, even with aggressive exploitation of equatorial locations for solar and wind beyond coastal limits.

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