By 2020, more than half of electricity consumption is to be covered by wind power.
It is an ambitious target, but one that looks manageable in view of recent progress. In 2011, with just nine years to go, wind generation was equivalent to 28.6% of electricity use. This had grown from a 25% share in 2010, when Denmark's electricity consumption amounted to 31.81TWh and wind generation contributed 7.81TWh, according to data from the Danish Energy Agency (ENS). If this annual 3.6% increase can be repeated each year to 2020, Denmark can even expect to exceed its target.
So far, the country is coping well with steadily growing amounts of wind energy. But the difficulty lies in continuing on the expansion path without undermining the quality of the electricity supply or causing dramatic power price fluctuations.
Several reasons lie behind the success so far. First, a big part is still played by fossil fuel co-generation plants, whose output can be controlled at will, albeit partly constrained by heat needs — when little heat is needed they operate at a low level or switch off. Coal and gas had respective shares of around 43% and 20% in Danish power generation of 38.78TWh in 2010. Coal will not be finally phased out until 2030.
Another advantage is Denmark's relatively unrestricted exchange of electricity with its neighbours. Cross-border transmission capabilities add up to 5.89GW, even more than the 3.8GW of wind power in operation in 2010, and approaching half of the country's total generation capacity at the end of that year, according to ENS data.
A third substantial plus-point for Danish wind integration is that the country is firmly embedded in the Scandinavian market trading system, operated by Nord Pool, and is linked through a market coupling system with the German energy exchange EEX and its spot-market arm, Epex Spot. This trading system means that even when the wind blows strongly Denmark can optimise the sale of its surplus energy on the market.
After all, price trends in the market are significantly influenced not only by wind power but also by amounts of rainfall in Norway and Sweden, where electricity production is dominated by hydropower and is therefore sensitive to water levels in rivers and hydropower plant reservoirs. Fossil-fuel and CO2 prices are also a factor.
But changes on the horizon,such as the expansion of the wind industry in Norway and Sweden, could affect the Scandinavian market and reduce its efficiency in accommodating excess wind from Denmark.
Such developments could upset the traditional trading roles among the countries. For instance, Finland is a substantial importer of electricity, but if the delayed 1.6GW Olkiluoto 3 nuclear reactor finally starts running in 2014, producing around 38GWh/day, the country's role as a sink for electricity will diminish.
The Danish government admits that 50% wind will be a challenge to security of the electricity supply. But it can be managed if, at the same time, Denmark moves towards a more intelligent energy system with flexible electricity consumption, strong connections abroad and an efficient international electricity market.
Danish network firm Energinet.dk plans to expand its interconnector capacity considerably over the coming years, says Bjarne Christian Gellert, the company's head of transmission grid planning. Links to Germany are expected to expand from 1.2GW to 2GW by the end of this year, to 2.5GW by 2020 and 3.5GW by 2030, he says.
Energinet.dk has an holistic view of the future energy system, in which the elements to be combined include intelligent integration of electric vehicles and heat pumps for demand-side management, more responsive conventional power stations and intelligent systems to allow increased interaction between electricity, heat, gas and vehicle transport systems.
It is not going to be easy, but the Danish government encourages wide participation. "The green transition is only possible if everyone participates," it says in its 2011 report "Our Future Energy’.