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122% Wind Power?: A Postcard from the Future of Energy

Renewable electricity records are falling every day. In early October, Germany recently hit a 59 percent renewable peak, Colorado utility Xcel Energy peaked at 60 percent wind at the beginning of the year, and Spain got its top power supply from wind for three months leading into 2013.

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

And Denmark has plans to get to 50 percent more wind by 2020, creating even bigger hourly peaks. Energinet predicts the country may hit as many as 1,000 hours per year of power surplus.

Q3 2013 power data from shows wind (red) and total demand (blue)

To champions of renewables, this is validation that a clean energy future is possible and that the transition is already underway. These regions also give insight into what is to come in the U.S., 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.

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, such as when a power plant breaks down. The fluctuations of wind and solar, especially at moderate levels, are just one more variable — 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, both minute-to-minute and over longer time frames. The most obvious example 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 even fossil fuels are the traditional forms of energy storage, but many more are emerging, such as using power to heat district heating systems, compressed air, batteries and flywheels, and charging electric cars during the renewable peak.

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 five-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.”

So how can Denmark be 122 percent 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.

As renewables grow and as Denmark attempts to phase out fossil fuels altogether by 2050, the country is 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 energy deployment. Demand response is beginning to grow, though in a different form than in the US. Denmark also has big goals for electric cars, and has exempted them from the 180 percent sales tax applied to gas and diesel vehicles.

But conventional solutions will be the first solution through better grid links between countries. As Germany’s Agora Energiewende has put it in its 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 constitute 70 percent of total supply. 

As in the U.S., 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.

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 its electricity from the wind. What will the country do with a 200 percent wind day?

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

America's Power Plan's picture

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John Miller's picture
John Miller on November 14, 2013

This post states: “(Germany and Denmark) also give insight into what is to come in the U.S., and what needs to change to keep a reliable and affordable power system as clean energy grows”.  What needs to probably change is the Public’s definition of “affordable power”.  In the U.S. Residential or Household electric power costs currently average about 12 cents per KWh.  This compares to Germany and Denmark, the two EU Countries with the highest electricity expenses, which have average Household power costs of 36 and 40 (U.S.) cents per KWh respectively.  Granted, Germany and Denmark have made outstanding progress in expanding their variable wind/solar and thus far have been able to reliably managed increasing levels of these non-dispatchable renewable power sources (largely with the help of neighboring EU Countries’ power grids with adequate reserve/backup-peaking power on-line capacity), but these upgrades have been extremely costly.  The issue of “affordability” will be a major subject for future U.S. Public debate and acceptance.

Keith Pickering's picture
Keith Pickering on November 14, 2013

Wind is cheap, as long as market penetration is modest. When market penetration is large, as in Denmark, the cost of wind power will rise. And in fact, Denmark has the highest electricity prices in Europe.

So when the wind is blowing strongly, Denmark exports it wind power. That’s fine, but at what cost? When Denmark puts its energy on the export market, the oversupply drives down the wholesale price. Thus on a windy day, Denmark sells its windpower cheaply. But when the wind is not blowing, Denmark must import power, and the excess demand drives up the wholesale price. So Denmark buys electricity for high prices, and sells for low prices. Economically, this is the worst of both worlds for the Danes.

And what if the rest of Europe were to follow Denmark’s lead and switch to wind in large amounts? What then on a windy day, when every country on the grid has power to export, and the demand for exported electricity is small or even zero? Then, the only solution is curtailment: shut down the wind generators to save the grid. Which means the capacity factor of wind declines, which means the cost of wind again increases.

Well America’s Power Plan is right about one thing: these problems are not new. Neither are they solved.

The obvious solution is to use wind sparingly: in small enough grid penetration to prevent curtailement, even on a windy night in October. That in turn requires significant amounts of non-fossil dispatchable sources of electricity, and the cheapest of these are hydro, where available, and nuclear, where not.

America's Power Plan's picture
America's Power Plan on November 14, 2013

John Miller,

Thanks for your comment.   European electric rates, just like in the US, are complicated and opaque.  But here is a handy source of data, from the EU.  

It says indeed that residential rates are highest in Denmark and Germany.  But also notes that “the highest proportion of taxes in the final price of electricity for [residential] consumers was recorded in Denmark, where more than half (55.8 %) of the final price was made up of VAT, taxes and levies; Germany (44.9 %) and Portugal (43.2 %) had the next highest shares.   This chart breaks out the components, showing “energy and supply” costs in Denmark are only 6.8 cents of the total 29.8 cent price.  Total prices in the UK are half of that in Denmark, but largely because power is untaxed.  The “energy and supply” cost in the UK is 11.7 cents.

It’s also interesting to note that industrial power costs in Denmark and Germany are just average in the EU.  This is partly due to the fact that most German industries don’t pay the EEG surcharge; it is charged  to residential consumers.  So pointing only to residential rates, and ignoring the components of the rates, intentionally exaggerates the supposed effect of renewables.

America's Power Plan's picture
America's Power Plan on November 14, 2013


You’d have to do some digging to find the relative value of wind vs. imports on the Nordic pool, I can’t answer that question.  This site from Energinet, the Danish grid operator, lists hourly data on consumption, production and power flows for Denmark.  You could probably correlate the import/export flows with prices to find an answer.  

I assume the Danish authorities have done that calculation and think wind is a good idea, since their goal is to go from 30% to 50% wind over the next decade.

As for curtailment, one point of the article is that Denmark is part of a larger regional grid, so curtailment is minimized. Parts of the US, like the West, are discovering that small balancing areas are more expensive to run than larger, more liquid markets.  As a workaround, Colorado grid operators are using curtailment as a way to make wind dispatchable, for up and down ramping services.  It’s like direct load control, but with wind turbines.  As long as they pay the wind farms for providing those ancillary services, everybody is whole, and overall operating costs are minimized.  So curtailment is not necessarily a failure; it is becoming an operating tool that serves the overall system.

In the long run, yes many countries in Europe are scaling up their wind and solar.  As a result, there is growing interest in consolidated balancing areas, even Europe-wide, as well as experiments in storage, hydrogen production and “power to gas” production.

Thanks for your interest.

– Ben Paulos


John Miller's picture
John Miller on November 14, 2013

Unfortunately, the incremental/variable ‘energy & supply costs’ cannot be separated from the fixed ‘network (T&D) costs’; a major issue being strongly debated within the U.S. for distributed/net metered solar PV subsidies.  Your referenced data indicates that total average Denmark Household power costs are 0.068 (EUR)  + 0.064 (EUR) = 0.132 (EUR) per KWh or $0.178 (U.S. dollars) per KWh; compared to $0.120 per KWh average U.S. Household costs.  Yes, the tax structures make side-by-side comparisons more difficult, particularly in determining the level of ‘taxes and levies’ that subsidize or otherwise benefit the renewable power investors/suppliers.  So not pointing out these equivalent cost comparisons, could intentionally understate the actual costs of renewables.

Bob Meinetz's picture
Bob Meinetz on November 14, 2013

Ben, unfortunately peak generation statistics don’t tell the whole story.

Danish citizens use an average of 6.12 MWh of electricity per capita annually while creating 8.3MT of CO2; U.S. citizens use 13.24 MWh of electricity while creating 17.6MT of CO2.

Though Americans use more than twice as much electricity, Danish carbon intensity is 3% higher than that of America – for the energy that they do use, they’re paying a lot more and creating a bigger mess.

With all of those windmills, how does that happen?

Paul O's picture
Paul O on November 15, 2013

After reading this post and then discovering that Denmark still Generates more CO2 (Carbon intensity wise) than the USA, It is forced to Export its excess power to Norway, and it Pays more than any other European Country for electricity, I am now more than ever persuaded that The United States should definitely NOT follow the Wind Power Renewables  path that is being touted by this author.


At best it is ill-considered, and at worst it is a fraud on the poor Danes.

America's Power Plan's picture
America's Power Plan on November 15, 2013


The data you cite from the World Bank show kWh consumption and total carbon — from all sources, not just power generation — per capita, but they don’t show the carbon intensity of the power systems. You are making a leap that is not supported by the data.

This report from Energinet has all the 2012 data on Danish power sector emissions and trends.  One notable fact:  power sector CO2 has fallen 41 percent since 1990, just as wind grew from 0.2% to 30% of supply.  Growth in CHP and biomass also contributed to the decline in CO2.


America's Power Plan's picture
America's Power Plan on November 15, 2013

Paul O,

According to the US EIA, the carbon intensity (emissions per GDP) of Denmark is 0.179  MTCO2 / $1000.  The similar measure for the US is 0.413.  (By another measure, emission per “purchasing power parity,” Denmark is 0.253 vs. 0.413.)

The per capita carbon emissons from energy consumption are 8.439 MTCO2 / person in Denmark and 17.621 in the US.

So carbon emissions from energy are about half in Denmark compared to the US, by person and by economic output.


– Ben Paulos

Bob Meinetz's picture
Bob Meinetz on November 15, 2013

Ben, thanks for that correction. I notice that although Energinet provides a graph for CHP carbon emissions through 2011, there are no hard numbers. The graph appears to show something around 21 MMT CO2 for 2010; another source shows it about 10% higher at 24.21 MMT

The graph then falls quickly thereafter but I can’t find any source with actual figures supporting this drop in 2011. Do you know where they’re getting these numbers?

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