Tuesday, September 29, 2009

Solar vrs Wind

My last tirade about rooftop photovoltaic installations prompted a request for alternative suggestions.

The problem with rooftop solar photovoltaic electricity generation is that it costs too much. According to this a 4 KW rooftop photovoltaic installation costs $32000 or $8000 per KW. By comparison a 1.5 MW GE wind turbine like those in the Walnut Wind Farm appears to cost about $3000000 or $2000 per KW. So the wind turbine is 1/4 the cost per KW. It can be expected to have a better capacity factor as well. Note rooftop solar in particular will often have a lower capacity factor because of unfavorable location or orientation. So wind is much cheaper.

The above figures are rough estimates. For a sanity check see this account of a HSBC investment report which says in part:

What’s really interesting about HSBC’s new report is how solar power stacks up today against other ways of generating electricity—it doesn’t. That is, all the other power-generation technologies are in roughly the same neighborhood, even wind power—but not solar.

For instance, HSBC estimates costs per megawatt for different options: Combined-cycle gas, 43 euros; regular coal, 62 euros; onshore wind, 58 euros; nuclear power, 48 euros; geothermal, 43 euros. Photovoltaic solar power costs 290 euros per megawatt; concentrated solar power 181 euros.

Again wind power is much cheaper than photovoltaic solar power. In fact if we ignore the fact that wind is intermittent it is competitive with fossil fuels.

So wind is real, rooftop photovoltaic is just symbolic.


  1. Agreed - Wind Farms could easily solve a number of our green energy needs. Still, I think solar panels are the most interesting in the sense that they seem to be 'evolving efficiency' over time. There is indeed a lot of venture capital and faith invested in the tech, but we already have the tech to build offshore wind farms!

  2. Wind turbines are also getting more efficient. And the gap with rooftop solar is very large. One problem with rooftop solar, particularly when retrofitted, is every installation is unique making mass production cost reduction techniques less effective. I just don't see rooftop solar as anything other than an expensive diversion.

    As for offshore wind, it is attractive in that there are some good locations near population centers. But I think the much greater construction and maintenance costs mean it is not competitive yet.