Denmark is frequently held up as a country that shows how you can get to high levels of wind energy. From a simple factual point of view some things are rather clear.
Last year Denmark produced 39% of its electricity from wind turbines. This is much more than any other country. And four times more than Germany or Britain.
Yet, this high level of penetration is enabled by Denmark’s unique position. The uninformed claim once made in the Guardian that “the intermittency issue is easily dealt with as, for example, demonstrated by Denmark” is simply not true.
Consider the times when Danish wind farms produce more than 100% of its electricity demand. Electricity cannot be stored, at least not on a large scale. So, on these occasions Denmark simply has to export the excess to its neighbours. This option is not available to most countries. Furthermore, getting even close to 100% is currently technically unfeasible except in rare countries such as Denmark.
Wind turbines do not provide what is called inertia to an electricity grid. As a result grid operators think they will have to restrict wind power to somewhere between 60 and 75% of instantaneous demand. Any excess above this limit will have to be shed. As a result, in most countries getting to 40% wind energy would result in a large amount of the energy produced by wind farms being curtailed and thus not used. (The issue is discussed in this recent paper about the Irish grid.)
So, how does Denmark do it?
It’s simple. They are interconnected like crazy. A simple comparison with Britain is revealing
Average electricity demand in Britain is roughly 40 GW, while it is around 4 GW in Denmark. A difference of a factor of, then, in electricity consumption.
Yet, Denmark actually has more interconnectors than Britain. Denmark has around 6 GW compared with Britain with less than 4 GW.
So, if it’s windy in Denmark all they do is export the stuff on a large scale to their neighbours. They don’t need to worry about excessive wind production. But everyone else does.
Britain, for example, would need to build 40 GW of interconnectors to be interconnected like Denmark. So, don’t listen to people who tell you Denmark shows that the problems of intermittency are “easily dealt with”.
And here is some actual data showing just how much of Denmark’s wind power is exported. Using data for 2012, the graph below compares hourly wind generation with net exports. The relationship is clear (the blue curve is a simple regression). More wind generation equals more exports.
Similarly, we can compare hourly wind farm output with actual load. Below I show hourly wind farm output versus how much of the load is met by wind farms. As you can see this frequently gets close to or exceeds 100%. This is not an option for most countries. In fact, the dots you see above 60 or 75% or so are currently not technically feasible outside Denmark.
So, there you go. Denmark is an excellent example of a country that has been able to massively expand wind energy. It is also an example that cannot be copied by many.