James Hrynyshyn in Class M:
Sure wind power contributes only fraction of what coal does to the U.S. electrical grid, but it turns out it's already competitive with natural gas in some markets. Yes solar photovoltaics are expensive, but costs are falling fast (as opposed to nuclear power) and it's only a matter of five or 10 years at current rates before even PV arrays make economic sense for select consumers.
Finally, we're getting some honest assessments. First up is a pair of papers in the journal Energy Policy by Stanford's Mark Z. Jacobson and UC Davis' Mark A. Delucchi collected under the common title of “Providing all global energy with wind, water, and solar power.” Part 1 deals with the physical issues and Part 2 the economics. The conclusion of their exhaustive research is that is it entirely possible to run the entire world on wind, water (hydro-electricity) and solar power (both PV and concentrated thermal) by 2050. And they aren't restricting themselves to the electrical grid. This includes replacing all fossil fuels with batteries and fuel cells:
Such a WWS infrastructure reduces world power demand by 30% and requires only 0.41% and 0.59% more of the world's land for footprint and spacing, respectively. We suggest producing all new energy with WWS by 2030 and replacing the pre-existing energy by 2050. Barriers to the plan are primarily social and political, not technological or economic. The energy cost in a WWS world should be similar to that today.
How will we build it? Well, the numbers at first look daunting.
We estimate that ~3,800,000 5-MW wind turbines, ~49,000 300-MW concentrated solar plants, ~40,000 300-MW solar PV power plants, ~1.7 billion 3-kW rooftop PV systems, ~5350 100 MW geothermal power plants, ~270 new 1300-MW hydroelectric power plants, ~720,000 0.75-MW wave devices, and ~490,000 1-MW tidal turbines can power a 2030 WWS world that uses electricity and electrolytic hydrogen for all purposes.
But given how rapidly a modern industrial nation can build things like tanks and airplanes — as the American experience during the Second World War proves — the author's argument that we DO have the technology is pretty convincing.