Editor’s note: This commentary is by Willem Post, a retired engineer, who now writes about energy issues, currently specializing in energy efficiency of buildings and building systems. He is a founding member of the Coalition for Energy Solutions.
[T]he sum of Germany’s variable wind and solar energy has become a large percentage of all energy on the German grid during windy and sunny periods. However, to balance the variable energy supply with demand, the output of other, flexible generators, usually fossil-fuel-fired, is needed. As a result, Germany’s total generation significantly exceeds demand before, during, and after these periods.
Curtailing the wind turbine output would reduce the excess energy, however, feathering wind turbine blades likely would produce unfavorable media attention. Instead, the excess energy is exported to nearby foreign grids, usually at near-zero or negative wholesale prices, i.e., Germany is paying countries to import its excess energy.
The German system is constrained by a somewhat fixed capacity of “must-run” plants for essential services, such as hospitals, trains, street and traffic lights, various three-shift industries, etc. Those plants cannot be reduced in output below about 50 percent, to prevent them from being unstable, i.e., they cannot sufficiently “get out of the way” of the larger surges of wind and solar energy.
Wind turbines, which are asynchronous generators, do not support the stability of the German grid (help maintain frequency and voltages within defined ranges), because they usually consume reactive power, instead of providing it, as do traditional, synchronous generators. As wind energy becomes a greater percentage on the German grid, and synchronous-generator energy a lesser percentage, grid stability issues arise, which are exported to connected grids. New utility-scale wind turbine plants will need to comply with new rules regarding connecting to the grid to enhance grid stability. See here.
Foreign countries, such as the Netherlands, France, Denmark, Norway, Poland, the Czech Republic, etc., usually welcome Germany’s low-cost energy. They export energy to Germany at much higher wholesale prices, when Germany’s wind and solar energy is insufficient. As Germany is closing its nuclear plants, and continuing its ENERGIEWENDE-2050 wind and solar build-outs, Germany’s money-losing energy trading is likely to increase in future years. (New York Times link)
On May 15 Germany met all but 300 MW of its energy demand with renewable energy (mostly wind and solar) for a few hours.
However, Germany’s energy exports have run into some roadblocks. France, Belgium, the Netherlands, the Czech Republic and Poland have installed phase shifting transformers to protect their grids from unwanted surges of German energy exports, and it’s only 2016. (Politico link)
On May 8 based on EPEX spot data,
• The lowest export price was -178.01 euro/MWh, with a weighted average of -144.78 eur/MWh, between 12:30 and 12:45
• Later in the day, prices went down even further to -374.00 eur/MWh, between 14:30 and 14:45
On May 15 Germany met all but 300 MW of its energy demand with renewable energy (mostly wind and solar) for a few hours. At that time, mostly fossil and nuclear plants, with a total capacity of about 12,800 MW, operating at about 60 percent of capacity, had an output of about 7,700 MW. The resulting excess energy was sold at negative prices, per EPEX spot data. (Bloomberg link)
Remember, the legacy cost of the ENERGIEWENDE energy is about 19 eurocent/kWh. The legacy cost of Germany’s traditional energy is about 5 eurocent/kWh. For example, with, say 95 percent renewable energy on the grid, and total energy generation at about 105 percent of demand, the cost of that energy mix would be (5c x 10%; traditional + 19c x 95%; renewable)/1.05 = 17.67 eurocent/kWh, of which about 5 percent would be exported at significantly negative prices.
No wonder Germany has been reducing its wind and solar build-outs, due to complaints and blockages from nearby countries and losing money on energy exports. With energy exports partially blocked by the phase shifting transformers, Germany could respond by:
• Curtailing wind and solar energy production during windy and sunny periods, but that would attract adverse media attention.
• Adding quick-starting, flexible, gas-fired, plant capacity, MW, but that would “lock-in” CO2 emitting fossil fuels and gas imports.
• Building more north-south HVDC transmission grid, but that has been constrained due to NIMBY for more than 15 years.
• Adding battery-based energy storage, but that would be expensive and take many years, because economically viable, utility-scale storage, suitable for seasonal variations, has not yet been invented.
Germany is very rich in money and technology, unlike many other countries, and likely will find a way to make it work. It will be interesting to see how it all will turn out.
