27.08.2014
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Assumptions about power consumption for 100 percent renewable supply

What does the recent study on the technical feasibility of 100 percent green electricity in Germany assume about power consumption, including power storage? Today, we investigate – and report on a significant finding about wind power.

It seems I cannot blog as fast as news comes out. I now see that the German Environmental Agency (UBA) has published its own study (in German) investigating a 100 percent renewable power supply by 2050, written by the Wuppertal Institute. We will have to come back to that later. For now, let’s return to the study written by Fraunhofer IWES of Kassel on behalf of German renewables organization AEE, which we have been reviewing this week.

You may want to open up the fantastic visualization again, which is unfortunately only available in German. I translate the legend for you here. And yesterday, I talked about the assumptions for power production.

In the background paper (PDF in German), power consumption is extrapolated from current consumption data, which is expected to drop slightly due to efficiency gains, though “the more frequent use of air conditioning, electric vehicles, and heat pumps” will increase demand somewhat. Nonetheless, the total power consumption drops to 532.3 TWh, a figure is not far below the current level once we factor out the direct consumption of power by conventional power plants themselves (which nearly disappears in a 100 percent green power scenario).

Power consumption is pushed up, however, because 36.6 TWh is assumed to be lost from the storage of 68.9 TWh of power. Here, we see that this 100 percent supply of renewable electricity requires roughly 15 percent storage. Nonetheless, I do not see from the background paper how we get to the 612.4 TWh consumed in a year; this figure on the visualization does not tally with the background paper.

The background paper does not say how much battery storage is required but does state that 13 GW of power-to-gas capacity is assumed.

It thus seems that the background paper is not exhaustive. To find the missing information about batteries, I therefore went over to another interactive chart that might interest you – the “scenario map” (once again, only in German). There, we find that 55 GW of batteries are assumed, along with 13.5 MW of pumped hydro and compressed air storage. The efficiency of the batteries is assumed to be 85 percent, compared to 75 percent for pumped hydro and compressed air.

One begins to get the impression that there is actually no single document summing up the entire project, not even in German. But the more you click through it, the more you find that little tidbits of fascinating information. For instance, if you open up the box on wind energy in the scenario map, you see that the total number of wind turbines installed is a mere 21,349 both onshore and offshore – fewer than we have today (the BWE lists 23,645 turbines at the end of 2013, and new ones are being added in 2014 at a record rate)!

And yet, wind power only covers 10 percent of demand this year. In this scenario, it will therefore get six times that much from roughly 10 percent fewer turbines.

The project could certainly use more PR – hey, I’m doing what I can. Perhaps some of these findings are not being announced as loudly as they deserve because the focus of the study was actually on grid integration – how many power line kilometers are needed, where are the bottlenecks, and what is the impact on the quality of power supply (frequency, reactive power, etc.). I come back to that in my next post.

(Craig Morris)

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6 Comments on "Assumptions about power consumption for 100 percent renewable supply "

  1. Charles Komanoff - 27.08.2014, 23:07 Uhr (Report comment)

    @Ulenspiegel: thanks for info. Note that your 2040 turbines would generate ~5.1x as many kWh's as the average installed 2013 turbines. (4.75 vs. 1.5 MW x 2750 vs. 1700 FLH).

  2. Charles Komanoff - 27.08.2014, 19:57 Uhr (Report comment)

    @Ulenspiegel: thanks for info. Note that your 2040 turbines would generate ~5.1x as many kWh's as the average installed 2013 turbines. (4.75 vs. 1.5 MW x 2750 vs. 1700 FLH).

  3. Charles Komanoff - 27.08.2014, 19:54 Uhr (Report comment)

    Thanks for your honest effort to distill this important work. Does the BWE data include the total capacity of the installed wind turbines, from which we could compute the average? That would help in evaluating the finding that 10% fewer turbines could provide 6x as much power.

  4. Ulenspiegel - 27.08.2014, 19:02 Uhr (Report comment)

    In 2013 an AVERAGE turbine has around 1.5 MW and 1700 FLH, a ste of the art turbine produced in 2013 has 3 MW with 2500 FLH. For 2040 I expect something like 4.5 -5.0 MW with 2500-3000 FLH (1% improvement per year), i.e. one turbine generates at least 6 times more energy than the average in 2013. The proposed 21.000 turbines would generate around 300 TWh.
    However, the 530 TWh demand are quite low, other Fraunhofer scenarios with a lot of P2G work with around 900 Twh, therefore, I expect more turbines in the long run.

  5. sam b - 27.08.2014, 17:28 Uhr (Report comment)

    Doesn't that just means that the average power per turbine of the simulation (about 6MW per turbine) is roughly 6 time bigger than the average one of the current mix ?

  6. Charles Komanoff - 27.08.2014, 16:02 Uhr (Report comment)

    Thanks for your honest effort to distill this important work. Does the BWE data include the total capacity of the installed wind turbines, from which we could compute the average? That would help in evaluating the finding that 10% fewer turbines could provide 6x as much power.

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