Conclusion

Analyzing the impact on VRE forecast errors on the energy system is a wide field with numerous actors and markets. This thesis had the focus on the BRPs, BSPs, TSOs in relations to the auction-based markets with day ahead trading (DAM and 15IA), the continuous market (ICM), and the balancing markets (for FCR, FRR, and RR). The balancing measures were divided in passive balancing, including internal- and external self-balancing, and active balancing of the TSOs. The general objective of balancing measures is to maintain the gird reliability and simultaneously minimizes the costs or at least charge them to those actors who caused them [25].

The energy system was designed for a high share of dispatchable power plants, which were classified according to their marginal costs. Forecasts were only necessary to determine the load profile for the following day. Based on that, the schedule of the dispatchable power plants were planned. With the increasing motivation to introduce RES into the system and the long-term goal to replace the conventional power plants, the system requirements are constantly changing since that moment. The infeed from RES is becoming an element of uncertainty for the system balance and a possible source for balancing costs. Charging the incurred costs to the operators of RES, forms a contrast to the effort to increase the share of non-pollution generators. Consequently, the system design had to be adjusted in order to make the system accessible for RES.

Therefore, incentives were given, include priority dispatch and a fixed feed in tariff. The RES under the FiT are not exposed to the prices at the markets in order to lower the investment risks an increase the overall share of installed capacity. Many of these contracts will end in the next years and from this on a rising number of RES are exposed to price signals. Consequently, further system adjustments might be necessary in the future (see chapter 2.1 and chapter 6.1).

The higher share of VRE within the system, furthermore, increased the variability of the supply side and the degree of uncertainty due to the inherent forecasting errors. The analyses of past forecasts provided by the ENTOS-E Transparency Platform [19] stated a seasonal behavior of the errors and a dependency on the gradient of the actual generation, particularly for onshore wind (see chapter 4.2). These findings are in accordance to the forecasting result of the ARIMA model (see chapter 5.3.2).

Short-term deviations between power demand and supply – amongst others caused by VRE forecast errors – need to be corrected through balancing measures. For the case that these deviations are closed through active balancing measures from the TSOs, the costs for that are in included in the EEG surcharge and in the end covered by the power consumers. A high enough IP price could act as an incentive to shift the balancing responsibility from the TSO to the BRPs which caused the imbalance. Possible limitations of the IP pricing are given in chapter 6.3. Moreover, the introduction of the 15IA in December 2014 contributed to reduce the occurrences of deviations by offering 15 minutes contracts to better represent the infeed from solar and consequently, lowered the costs of active balancing power provided by the TSOs (see chapter 6.2). Another way of correct imbalances is to trade at the ICM but there are still some barriers for many market participants to actively use this way. Some BRPs with flexible power units prefer to re-dispatch their own portfolio to keep the balance. Others are still lacking the capabilities to adequately react to short-term price signals of the ICM or to trade at non office hours or weekends.

To cope the challenges of a system with a high share of intermittent RES all the mentioned actors and system need to interlock. The first phase of the system transition had the goal to increase the installed capacity. This way must be continued but simultaneously the system must be aligned in a way that it is able to handle the intermittent character of VRE.