Postcard from the Future: Denmark

denmarkRenewable energy records are falling every day.   Germany hits 59%!  Xcel Energy in Colorado peaks at 60% wind!  Wind is the #1 power supply in Spain for three months!

But that’s chump change.  Let’s look at Denmark.  According to data from, the national grid operator, wind power has produced 30% of gross power consumption to date in 2013.  This includes over 90 hours where wind produced more than all of Denmark’s needs, peaking at 122% on October 28, at 2:00 a.m.

And Denmark has plans to get to 50% wind by 2020, creating even bigger hourly peaks.  Energinet predicts the country may hit as many as 1000 hours per year of power surplus.

hourly danish data

Click to enlarge

To champions of renewables, these are daily validations that a clean energy future is possible, and that the transition is already underway.  These regions also give insight into what is to come, and what needs to change to keep a reliable and affordable power system as clean energy grows.  As part of America’s Power Plan, we have developed a series of “postcards from the future,” describing places like Denmark that are already grappling with a high-renewables future.

Many Tools

Studies and real-world experience are underscoring that there are many tactics available to deal with the variability of wind and solar, and that these tactics are largely substitutes for each other.

While energy storage comes to mind first for many people, the truth is that the grid has functioned just fine with very little storage.  Power system operators have to deal with variability all the time, with or without renewables. Demand fluctuates with the weather, time of day, social activities, and industrial operations.  And supply varies unexpectedly too, like when a power plant breaks down.  The fluctuations of wind and solar, especially at moderate levels, is just one more variable – and one that may or may not add to overall variability, depending on the system and timing.

Power system engineers use a whole suite of tools to match supply and demand, in both minute-to-minute and longer time frames.  The most obvious is a dispatchable power plant, like a gas turbine.  But they also benefit from bigger balancing areas (trading power with neighbors), more transmission connections to reduce congestion, faster-acting fossil power plants, direct load control and demand response, targeted energy efficiency, and curtailment of wind and solar plants.  Hydro power, and indeed fossil fuels, are the traditional forms of energy storage, but many more are emerging, like using power to heat district heating systems, compressed air, batteries and flywheels, and charging electric cars during the renewable peak.

And it is increasingly common to treat wind power as a controllable generator, rather than just letting it go full out.  System operators in New York, Texas and the Midwest direct wind farm owners to submit 5-minute forecasts of output, and ramp up and down if necessary to meet system demands, just like conventional generators.  The Midwest ISO enforces this with a “dispatchable intermittent tariff.”

122% wind?!

So how can Denmark be 122% wind powered?  Where does the extra power go?

Denmark is part of an integrated regional grid, with the Scandinavian countries and parts of Germany. They have a constant trade with utilities in the region, especially hydro plants in Norway.

The Nordic Pool

Click the image for real-time data.

As renewables grow, and Denmark attempts to phase out fossil fuels altogether by 2050, they are aggressively adopting smart grid  technologies, leading Europe in research and demonstration projects on a per capita basis.  The island of Bornholm will be a test bed, with extensive smart grid and renewable deployment.  Demand response is beginning to grow, though in a different form than in the US.  Denmark has big goals for electric cars, and has exempted them from the 180% sales tax applied to gas and diesel vehicles.

But conventional solutions will be the first solution, through greater links between countries.  As Germany’s Agora Energiewende has put it in their 12 Insights report, “grids are cheaper than storage facilities.”  More grid connections allow surplus power to be shipped off rather than curtailed or stored.  Larger balancing areas reduce the variability of wind and solar across a wider geographic area.  Agora thinks storage will only be necessary when renewables hit 70% of total supply.

As in the US, European regulators are grappling with policies to integrate large amounts of renewables.  While technical issues remain, they are not really new, only of a larger scale. Most of the integration tools are known; they just need to be bigger and more capable to deal with bigger variations.

Policy Questions

Less known are the policy issues.  How big should control areas be?  How much should be invested in transmission lines, and who should pay for them?  What is the relative value of energy payments, versus capacity payments or ancillary services?

Most of all, how should we pay for the services we need to keep the lights on?  In America’s Power Plan, Mike Hogan of the Regulatory Assistance Project, calls for aligning power markets with clean energy goals, giving proper incentives for market flexibility.

With 2020 just around the corner, it will be instructive to see how Denmark deals with getting half their power from the wind.  What will they do with a 200% wind day?


CAISO system snapshot

Click for real-time data from California ISO.

A number of power system operators have put their real time data online and in iPhone apps, so you can track hourly progress on renewables.