Welcome to this session on integration of variable wind power generation into the power system. My name is Poul Sarensen and I'm professor in wind power integration and control. After this lecture you will be able to tell about the successful growth of wind power. You would also, hopefully, be able to understand some of the basic challenges of operating power systems with large scale variable wind power generation. And finally, you will be able to explain the role of electricity market, the balancing of reserves in the power system and how they are effected by the variable wind power generation. This slide shows the fast growth of wind power. In 2013 wind power supplied 3% of the total global electricity consumption. In Denmark, however, in 2014, wind power covered 39% of the electricity consumption, which is a world leading record. And the targets we have in Denmark is by 2020 to supply 50% of the electricity consumption from wind power, and in 35 the target is to supply 100% of electricity from the renewables. Now these are very high numbers but actually, also the wind power development in Ireland is very impressive. Because Ireland is not like Denmark, strongly interconnected through neighboring countries, which makes it even more impressive that they could in 2014 produced 19% of the total electricity consumption on the island from wind power. This graph shows the case in January last year where there was another record with 84% of the electricity during that month supplied from wind power. And what we see is that this corresponds to 236 hours, or 32% of the time, actually we were generating more wind power than what we were consuming. And, this is of course only possible, because, we are strongly interconnected to our neighboring countries and we, Denmark is participating in well-functioning Nordic market, where our neighbors are buying this wind power, and then when wind power is not producing, then we can buy cheap hydropower in Norway. Until today, most of the wind power has been installed on shore by far. But now the off shore development is growing very fast, and it is going to increase to a massive installation off shore in the not so far future. This is illustrated in the two maps we have here. To the left we see the expected development of about 40 Gigawatts off shore in North Europe by 2020. And to the right we see about 100 Gigawatt offshore by 2030. What we also see here is that the offshore wind power is very concentrated. This massive amount of offshore wind power is concentrated in relatively small areas. And this means because the wind turbines will see similar wind speeds in these areas. The total summed power will fluctuate more than what we are used to seeing from onshore wind power. I will now show you a video where we have done some simulations based on a weather situation we had in 2009. And we are simulating how this will affect the power fluctuations coming out from the offshore wind power in 2020. What we will illustrate with this animation is the situation when a storm is developing and passing over the North Sea, how this will affect this total wind power generated by the off-shore wind turbines here in this area. The thing is that when a storm is passing, then usually wind turbines will shut down at a certain wind speed. And this will be illustrated in blue. But, what we will also show here. In red at the same time is the situation where if the wind turbines are not shut down but they are powered down to produce less power instead of stopping completely. Then it will affect this the total generation of the off-shore wind power. That will be shown in red. So we can say the state of the art is the blue, and the more intelligent way of controlling the wind plant will be shown in red. So if we now start the animation then we will see how the wind, how the storm is approaching here. And we see in both cases the winds power is increasing. But then we have a sudden drop in the blue case. Because the storm is passing, but in the red we also have some reduced power, but not at all as much. And what we see now is that the storm is passing by, and then the wind turbines are restarting, and continue to produce in a normal way. The last slide will show the role of electricity markets in balancing and reserves in a power system with a large-scale wind power, and we will use the Danish example to illustrate this. In the Danish system, we have to cope with the forecast errors that we have on wind power and balance this. So what happens first is we are looking at the hour of operation here, and then we will see how the story develops. The first thing that happens is that the power is traded on a spot market which is done the day before the hour of operation. This is illustrated over here, and it is done based on a prognosis that we have at that time. This is the green curve we see down here. Then during the day of operation, there is an intraday market which is actually not used so much today. But on this market also the independent power producers, they can also trade and balance because they may have things to adjust, not necessarily wind power forecast errors, but maybe other plants have stopped, or you name it. So there is a possibility for the power producer to trade when he knows better, based on an intraday prognosis. Now when we come to the hour of operation, then the transmission system operator takes over the responsibility because now it becomes very important that we have balance between produced and consumed power in the power system. And what happens there is that half an hour before the hour of operation, the Energinet the Danish TSO is making a plan for how to balance the system. And this is done based on an hour ahead prognoses which is also shown here in the graph. This is what is shown with blue. And then Energinet is buying regulating power and balancing according to that prognoses. Now something may happen, before the actual real time of operation. And then there might be also some online real-time balancing, based on online prognosis. But most of the balancing actually takes place an hour before the hour of operation. So this can be a smaller adjustment. Now finally, there will be, the final production will not be perfect compared to the hour a head forecast. This will be the black curve here. And as you see, it fluctuates a little more than what is forecasted. And there will still be then some imbalances, and they will activate automatic reserves in the power system, which are allocated by the transmission system operator also. So by the end of the day because the automatic reserves would also have some response time and also limited volume, there will actually be always inevitably final imbalance. And this will be shared between the interconnected countries. And if we want to look more into how that balances then we can do dynamic simulations. So what we have talked about and learnt in this lecture are first of all, about the successful growth of wind power until now and also in the future. Also some understanding some basic challenges that we have with operating power systems with large scales of wind power generation. And finally, we illustrated the role of electricity balancing and reserves.