مقایسه طرح های پشتیبانی مختلف برای برق تجدید پذیر در حوزه تجزیه و تحلیل سیستم های انرژی

The present analysis illustrates how energy system models can play an important role in the long-term evaluation of support schemes for renewable electricity. Methodological approaches for the explicit representation of such instruments are presented both for price-based and quantity-based systems. In the subsequent scenario comparison, the current German feed-in tariffs (FIT) are contrasted with several alternative support mechanisms. With the current scheme, renewable generation is increased to almost 46% of gross electricity consumption in 2020 and 54% in 2030 associated with a rise in the surcharge on consumer electricity prices of 40% between 2011 and 2020. By switching to a technology–neutral certificate system which promotes only the most cost-efficient generation and adheres to the political targets renewable generation costs could be lowered by more than €200 billion between 2013 and 2030. At the same time, it has to be kept in mind that technology–neutral systems tend to cause a higher cost burden for electricity consumers. The greatest cost reduction can be achieved under a technology-specific quantity-based system with a decrease in cumulated FIT differential costs of €68 billion and of €416 billion in total energy system costs between 2013 and 2030 compared to the current system.

Enhancing the use of renewable energy sources is considered as one of the major strategies in the combat against climate change. For the European Union, an ambitious goal of raising the share of renewable energies in gross final energy consumption to at least 20% until 2020 has been established. In this context, the electricity sector plays an essential role. According to the National Renewable Energy Action Plans, the contribution of renewables to total electricity generation should rise to 37% by 2020. In order to reach this goal, by now some type of support schemes for renewable electricity has been implemented in every EU member state, with a clear domination of price-based mechanisms like feed-in tariffs (FIT) or premiums over quantity-based schemes, like tradable green certificate (TGC) systems or tendering procedures [1]. In Germany, fixed tariffs for renewable electricity have been applied since 1991 and especially the revised and expanded FIT scheme from 2000 has been highly successful in promoting renewable electricity generation raising its share in gross final electricity consumption from 6% in 2000 to 23% in 2012. However, with the growing importance of renewable energies, criticism of the instrument is also increasing due to its insufficient cost efficiency and market integration of renewable electricity. A large variety of studies has evaluated and contrasted different support systems for renewable electricity from a theoretical and empirical point of view (cf. for example [2], [3], [4], [5], [6], [7] and [8]). In general, assessment criteria like cost efficiency, distributional impacts, technology promotion, market integration of renewables, distribution of risk, transaction costs, etc. are applied in such analyses. Energy system models provide an appropriate quantitative framework for the evaluation of the long-term implications of support schemes for renewable electricity taking into account all interactions and repercussions within the energy system. Yet, so far the effects of such support schemes have in most cases only been taken into account in an indirect and inflexible way by exogenously setting the expected minimum amounts of electricity produced from different types of renewable energies without making reference to the characteristics of a specific support system (for the case of Germany cf. for example [9] and [10]). This, however, clearly reduces the flexibility of the model, as generally no changes in the electricity generation from renewable sources will occur when the scenario assumptions are altered and the effects on electricity prices are often not accounted for. Some first attempts have been made in recent years to incorporate renewable electricity generation in the optimisation approach and to explicitly represent specific support instruments (cf. the Green-X model [11], the PERSEUS-RES-E model [12], and the simulation model in [13]). With the exception of the PERSEUS-RES-E model, these approaches have the disadvantage that renewable electricity generation is analysed in an isolated manner, i.e. electricity prices are set exogenously such that no interactions with conventional power generation are considered and the effects on the demand side are neglected. Apart from that, the support systems for renewable electricity are generally modelled in a very simplified and abstract manner without keeping in mind the often complex structure of the real-world application of such instruments. In order to arrive at a modelling approach with high practical relevance, the analysis at hand uses the German FIT system as a case study and outlines a methodological approach with which instruments for the promotion of renewable electricity generation can be explicitly integrated into an energy system model such that all features influencing the competitiveness of renewable technologies are accounted for in a realistic and detailed manner and the effects both on the generation side and the demand side are determined endogenously. Germany has been a pioneer in renewable electricity policy and the FIT system has served as a model for several other European countries. Since the basic features of the FIT systems in use across Europe are relatively comparable, the methodological approach can easily be transferred to another national setting. The description of the methodology in Chapter 2 is followed by a comparative scenario analysis for Germany in Chapter 3 contrasting the current FIT system with alternative both price-based and quantity-based support schemes in terms of renewable electricity generation, costs of the support system, effects on the demand side and total energy system cost. This allows to contrast the performance of different support systems for renewable electricity in terms of important evaluation criteria such as cost efficiency of generation, distributional impacts on electricity consumers as well a technology promotion in a quantitative manner. To structure the analysis, a number of specific research questions have also been established: (1) How does the German electricity system develop under the current support scheme for renewable electricity? (2) What are the implications of a technology–neutral support scheme for technology choice and costs? and (3) Might Germany benefit from a quantity-based support mechanism where target adherence is guaranteed?

Energy system models can provide a valuable contribution to the quantitative evaluation of climate and energy policy instruments. Their main advantage over other types of energy models, i.e. top-down macroeconomic models, consists in their high level of technological detail which allows to represent the usually highly complex real-world policy measures in a realistic manner. At the same time, all repercussions and interactions within the energy system, especially between the supply and the demand side, are taken into account. The scenario comparison at hand indicates that when strictly adhering to the principle of cost efficiency the long-term development of renewable electricity in Germany would change considerably and generation costs could be lowered significantly. However, it is also shown that it is not guaranteed that consumers benefit from a support system that promotes the most cost efficient renewable technologies. A technology–neutral design can ensure a cost efficient expansion of renewable electricity, but at the same time allows renewable generators to generate high profits, especially in the case of technologies with comparatively low investment costs. Thus, countries implementing a new support system for renewable electricity should pay attention both to promoting the most cost efficient technologies and to limiting the cost burden on consumers with the help of a clearly differentiated remuneration structure. The German experience with a price-based support mechanism also shows the risk that the regulator is not able to set the appropriate remuneration level to fulfil the political targets and adjustments are subject to a certain inertia, while under quantity-based systems the remuneration is determined in a competitive manner. It has to be noted that this scenario analysis has focused on aspects of cost efficiency, distributional impacts and technology choice in the promotion of renewable electricity generation. Apart from these criteria, however, the decision for the appropriate support instrument will be guided by issues like the market integration of renewables, the target to promote technology diffusion, distribution of risk, transaction costs, etc. It is often argued that due to the planning security, FIT systems are more attractive for investors and that quantity-based systems where future revenues are uncertain entail higher risk premiums which might lead to higher support costs. For the case of Germany, it needs to be pointed out that the effects of the scenario comparison would be more pronounced if the different support systems were contrasted from the starting point of the promotion of renewable electricity in Germany in the year 2000. Here, only a shift to another system from 2013 onwards is considered such that in each scenario the first 12 years of the German FIT system have to be accounted for. At the same time, one must not forget that the transition from a FIT system to a TGC or tender mechanism might be politically difficult to realise and might entail high transaction costs, as given the necessity to “grandfather” existing installations both systems would have to be maintained side-by-side for a certain period of time. In the long term, with renewable energies becoming the dominant source in electricity generation, reform strategies will be necessary for the entire market design optimising both renewable and conventional generation.