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Figure 2: Aggregated electricity productions and consumptions in West Denmark together with day-ahead prices (Spot price) 6th December 2016. These productions and market data are shown online at www.emd.dk.
Figure 1: Annual electricity productions at distributed DHCP CHP in Denmark
An example of the flexible operations of Danish DHCP CHPs is shown in figure 2 and figure 3, showing respectively the aggregated electricity productions and consumptions in West Denmark together with day-ahead prices (Spot price) for the 6th December and 27th December 2016. The day-ahead prices rose at 7 o´clock on 6th December 2016 to the double compared to the prices in the night hours, which caused the DHCP CHPs (shown as local CHP units in the figures) to go from an electricity production of a little more than 300 MW to an electricity production of nearly three times bigger. Figure 3 shows a more extreme situation, where spot prices became negative until 7 o´clock on 27th December 2016 and the DHCP CHP production fell to approximately 100 MW. Comparing the two days (figure 2 and 3) shows a changed production from 100 MW to 900 MW, a flexibility in production of a factor 9. An important question could be why the DHCP CHP production was not reduced down to 0 MW when the day-ahead prices were negative – or another way to ask, which DHCP CHP is willing to pay around 400 DKK/MWh for being allowed to enter electricity into the grid. The simple answer is that it is the Danish Transmission System Operator (TSO) that is willing to pay so. These remaining 100 MW are mainly biogas CHP- plants, to which the TSO pays a feed-in tariff (FIT) independent of the hour in the day. The TSO is balancing responsible party (BRP) for these FIT-productions and sells the electricity from these plants as price independent production in the day-ahead market. In figure 3 it is further seen that a part of the wind production was curtailed until 7 o´clock. The wind production is as well offered in the day-ahead market, and some of the wind turbines use a bidding price around 0 protecting them from having to pay for producing electricity in certain hours. In fact, it is seen in figure 3 that the economic curtailments changed both at 6 o´clock and 7 o´clock, showing that wind turbine uses different bidding prices. Why, then, did not all wind turbines stop in these hours? The reason is probably that some of the wind turbines are old wind turbines that are not able to be operated/stopped remotely.
Figure 3: Aggregated electricity productions and consumptions in West Denmark together with day-ahead prices (Spot price) 27th December 2016. These productions and market data are shown online at www.emd.dk.
Wind power and PV with bidding prices around 0 lower the price in the day-ahead market, with negative consequences for CHP. Yearly average day-ahead prices in West Denmark 2011-2016 are shown in figure 4. By 2025, it is estimated that wind power and PV in Germany and Scandinavia will cover one quarter of the production there and thus depress power prices significantly with important consequences for DH and CHP. This side-effect of wind power development causes the Danish TSO to assess that 90 PJ of heat from CHP plants will be decimated to 5 PJ in 2050 when having 100% renewable energy.
Figure 4: Annual average day-ahead prices in West Denmark 2011-2016
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