اثر شایستگی سفارش : تجزیه و تحلیل دقیق از اثر قیمت تولید برق تجدید پذیر بر قیمت های بازار لحظه ای در آلمان

The German feed-in support of electricity generation from renewable energy sources has led to high growth rates of the supported technologies. Critics state that the costs for consumers are too high. An important aspect to be considered in the discussion is the price effect created by renewable electricity generation. This paper seeks to analyse the impact of privileged renewable electricity generation on the electricity market in Germany. The central aspect to be analysed is the impact of renewable electricity generation on spot market prices. The results generated by an agent-based simulation platform indicate that the financial volume of the price reduction is considerable. In the short run, this gives rise to a distributional effect which creates savings for the demand side by reducing generator profits. In the case of the year 2006, the volume of the merit-order effect exceeds the volume of the net support payments for renewable electricity generation which have to be paid by consumers.

The development of renewable electricity generation in Germany has been characterized by considerable growth rates throughout the past 15 years. This development is mainly driven by a guaranteed feed-in-tariff which has been in place since 1991. The actual conditions of the German support scheme were revised in 1998, 2000 and 2004 (see also Lauber and Metz, 2004; Wüstenhagen and Bilharz, 2006). Since 2000 the Renewable Energy Sources Act is in place. According to the law the German grid operators have to buy electricity generated by specified renewable energy sources at a guaranteed feed-in-tariff. In a second step the electricity is sold to the electricity suppliers according to their market-share. The additional cost for the feed-in-tariff has to be paid by the consumers in the end. There is a considerable debate on the efficiency and the cost of the renewable support scheme. Publications on international level on the analysis of cost and efficiency of different support schemes on the European level (Ragwitz et al., 2007; Huber et al., 2004) and the United States (Palmer and Burtraw, 2005) show that this discussion is not only a German phenomenon. As a consequence of the continuous growth of supported renewable electricity generation in Germany from 18.1 TWh to ca. 52 TWh per year in the period of 2001–2006 the payments for the feed-in-tariff rose according to the association of German grid operators from 1.6 billion € to 5.6 billion per year (Verband der Netzbetreiber [VDN], 2007). Additional aspects are necessary extensions of the grid and the increased demand for system services. However, recent studies show that the additional cost for these aspects are within the range of 1–10 €/MWh of renewable electricity generation which equals ca. 52–520 million € in the year 2006 (Auer et al., 2006; Klobasa and Ragwitz, 2006). But the electricity generated by renewable energy sources also has a value which has to be taken into account in the current discussion. Leaving minor aspects like necessary grid extensions and the increased demand for system services (see also Deutsche Energie-Agentur [DENA], 2005) aside the additional costs of the support from a consumer perspective could be defined by the feed-in-tariff minus the market value of the renewable electricity. An estimation of the market value of the renewable electricity generation can be calculated by multiplying the electricity production by the spot market price. Based on the market prices and the volume of the renewable electricity generation the market value of the generated renewable electricity can be estimated to ca. 2.5 billion €, almost 45% of the support payments. In another recent study which takes electricity trades on future markets into account the market value of renewable electricity generation is estimated at 44 €/MWh (Wenzel and Diekmann, 2006) or 2.3 billion €. The rising fuel prices and the introduction of the European emission trading system have led to a heavy increase of electricity prices which was not foreseen in the futures markets (European Energy Exchange [EEX], 2007a). This aspect leads to slight differences regarding the estimation of the market value. In addition the electricity generated by renewable energy sources also has an impact on the market prices itself. The central contribution of this paper to the current discussion of renewable support schemes is the analysis of this interaction. A stylized overview of the discussed effects of renewable electricity generation for a single hour is given in Fig. 1. It is assumed that the electricity demand is inelastic in the short-term perspective of a day-ahead market. Since the electricity generated by renewable energy sources has to be bought by supply companies in advance the remaining demand load that has to be purchased on the electricity markets is reduced correspondingly. Therefore the guaranteed feed-in of electricity generated by renewable energy sources has the effect of a reduction in the electricity demand. In the picture the German merit-order-curve, which is a step function of single plant units in the real world, is simplified as a linear supply curve. As long as this supply curve has a positive slope the reduced demand on the markets leads to lower prices. As this effect shifts market prices along the German merit-order of power plants this effect is called merit-order-effect in this paper. A central goal of this paper is to assess the actual value of the merit-order effect of German renewable electricity generation in the period 2001–2006. Another important interaction of renewable electricity generation is the interaction with the European emission trading system. A discussion of the interrelation of the German feed-in-support for renewable electricity generation and the European emission trading system can be found in recent publications (Rathmann, 2007; Walz, 2005). Future work will have to take this aspect into account. Since electricity demand and renewable electricity generation vary on an hourly basis, an estimation of the actual value of the merit-order effect is far more complex than the estimation of the market value. Therefore the analysis is carried out using the PowerACE Cluster System which is able to simulate hourly spot market prices.

This paper analyses the impact of the supported renewable electricity generation on spot market prices in Germany. The analysis is based on the detailed electricity market simulation platform called PowerACE Cluster System. The model-based analysis shows that the renewable electricity generation has a considerable impact on market prices. In the year 2006 the reduction of the unweighted average price reaches 7.8 €/MWh. If it is assumed that the entire electricity demand is traded based on the simulated prices the financial volume of the merit-order effect can be calculated. The analysis for selected years in the period 2001–2006 shows a considerable growth of the volume of the merit-order effect from 1 billion € in 2001 to 5 billion € in 2006. In a sensitivity analysis the driving factors for this development are determined. Besides the growing renewable electricity generation the main driving factor for the strong growth of the merit-order effect is the development of fuel prices. Thereby the gas price is the most important fact with a disproportionately high impact on the result. A considerable increase of gas prices and a moderate increase of coal prices have increased the slope of the supply curve (merit-order curve) in the analysed period leading to a higher financial volume of the merit-order effect. A central assumption for the calculation of the price effect is that the growth of renewable electricity generation had no major impact on the development of the power plant portfolio up to the year 2006. Although this assumption is reasonable additional scenarios are analysed where it is assumed that some of the decommissioned and mothballed capacity are caused by renewable electricity generation. Even in the very unlikely scenario that the entire decommissioning of the period 2001–2005 is caused by renewable electricity generation the volume of the merit-order effect reaches the remarkable value of 2.8 billion € in the year 2006. Another open issue is the impact of renewable electricity generation in Germany on imports and exports of renewable electricity generation. It is possible that renewable electricity generation leads to changes in the export and import load flows of electricity. In this case the parts of the volume of the merit-order effect spread across national borders. The integration of this aspect requires a detailed simulation of hourly prices on European level, which is a demanding task. However, a comparison to recent studies analysing the price effect based on statistical data of real world prices shows that the price effect of renewable electricity generation is comparable to the results presented in this study. In recent studies the impact of wind energy on market prices in Denmark (Morthorst, 2007) and Germany (Neubarth et al., 2006) price reductions of 12–15% are observed. As a result of the thorough sensitivity analysis and the comparison to the literature it can be stated that the claim that the merit-order effect for the year 2006 reaches a considerable volume in the order of magnitude of 3–5 billion € is robust. The considerable value of the merit-order effect shows that the cost for the EEG support to renewable electricity generation for consumers is dramatically reduced once this effect is taken into account. The support payments amount to 5.6 billion € in the year 2006. If the value of the renewable electricity of ca. 2.5 billion € and the volume of the merit-order effect of up to 5 billion are subtracted from the support payments a net profit for the consumers occurs. The merit-order effect shifts profits from generation companies to consumers. If the market value of renewable electricity and the potential savings for consumers created by the merit-order effect are taken into account the feed-in support can lead to a net profit for consumers in the short run. Whether the savings created on the wholesale market are passed on to consumers heavily depends on the competitiveness of the electricity supply system, especially the consumer market. A central question for future research is how the volume of the merit-order effect can be estimated for future years.