Debate over PV in Germany
As photovoltaics continues to boom in Germany, experts disagree over what the impact on the grid will be. The only thing that everyone seems to agree on is that PV will increasingly cut into the base load.
In an article in the Financial Times Deutschland of April 15, 2011 (PDF in German), German journalist Sascha Rentzing reports that photovoltaics could soon peak at 100 percent of power demand. "Then, conventional power plants would have to completely switch off at midday and then ramp up again abruptly in the evening."
Rentzing has faced criticism for this article, most recently at Sonne, Wind & Wärme, which pointed out some flaws in Rentzing's thinking. For instance, SW&W points out that 70 gigawatts of installed photovoltaics by 2020 – roughly equivalent to peak German peak power demand of 76.7 gigawatts last year – would not be equivalent to 100 percent of demand because 70 GW of the PV would only produce around 50 GW of power when it peaks. SW&W could, however, also be criticized in its calculation because the 76.7 GW peak occurs in late November; on the weekends in the summer, when PV production peaks, power consumption can indeed be as low as 50 gigawatts on a Sunday afternoon – so Rentzing is right, though only in exceptional cases.
SW&W disagrees with Rentzing that conventional power plants would have to be "abruptly" ( schlagartig) ramped up, and indeed the production that curve for photovoltaics does have quite a gradual slope. The question is whether that slope is steep enough to constitute an abrupt change for conventional power plants; for an estimate, see the charts in this article (PDF) from Photon (in German) from December.
SW&W also argues that Germany has a total power plant capacity of 135 GW to meet that peak demand of around 77 GW, but we must also keep in mind that roughly 45 GW of that was solar and wind last year, neither of which can be ramped up as need be. Germany therefore has no more than 90 GW of plant capacity that can be switched (or kept) on, and the current moratorium on nuclear plants has reduced that capacity even further to just above 80 GW. Clearly, things are getting tight.
Whoever you agree with in this debate, an international comparison on this basis is revealing . For instance, Rentzing quotes an expert from Fraunhofer who claims that around 98 percent of installed photovoltaic capacity in Germany is connected to low-voltage lines, whereas SW&W points out that the figure is no more than 85 percent based on statistics from the inverter manufacturer SMA. In either case, this fact once again shows the extent to which photovoltaics – and, indeed, renewables in general – is being implemented as small, distributed homeowner and community systems in Germany, in stark contrast to the utility-scale wind farms and giant solar arrays going up in the US, for instance.
In addition, markets are often spoken about in absolute megawatts, which are interesting from the viewpoint of business people trying to sell products. But clearly, Germany is far closer to reaching a point of saturation for photovoltaics – however defined – than any other country. In terms of grid impact, Germany will be the first test case for PV. (cm)