• Energy Research

Abstract In future energy systems with high shares of non-dispatchable renewable generation, the storage of electricity will play a key role. Today, a number of different storage options are discussed to cover the fast growing demand for storage. One of these options involves federal waterways for pumped hydro storage plants. The paper analyses the concept and the results of achievable storage potentials for Germany. The total storage potential for Germany sums up to approx. 400 MWh of which the majority can be attributed to four flight of locks which have been identified as the most suitable sites.

In order to implement osmotic power as a renewable energy source it is necessary to take into account the site-specific characteristics of any river mouth location where a project is proposed. This includes the salinity structure, inter- and intra-annual flow variations, ecological and social restrictions of the flow extraction, among others. Using the case of a location with suitable conditions for osmotic power, the Leon River mouth at the Colombian Caribbean Coast is analyzed in detail. A discharge analysis is undertaken to determine the appropriate size of an osmotic power plant by studying the relationships of the flow extraction with the installed capacity, load factor and yearly generation of the power plant. Furthermore, hydrological and ecological characteristics of the river are taken into account. Once the design flow is determined, the impact of the flow extraction on the salinity structure is analyzed for different climatic scenarios defined by the ENSO phases. The developed methodology can be taken as a basis to assess the osmotic power potential of other rivers on a worldwide level.

Abstract Increasing renewable energy generation influences the reliability of electric power grids. Thus, there is a demand for new technical units providing ancillary services. Non-dispatchable renewable energy sources can be balanced by energy storage devices. By large-scale battery energy storage systems (BESSs) grid efficiency and reliability as well as power quality can be increased. A further characteristic of BESSs is the ability to respond rapidly and precisely to frequency deviations, making them technical ideal candidates for primary control provision (PCP). In this paper environmental impacts of PCP by novel Li-ion BESSs are compared to impacts of PCP by state-of-the-art coal power plants (CPPs) using a Life Cycle Assessment (LCA) approach and considering German control market conditions. The coal power plant stock is characterized by varying properties. Thus, different scenarios of CPP operation are analyzed by varying sensitive parameters like efficiency loss and required must-run capacity. Finally, PCP by BESSs and CPPs are compared in terms of environmental performance. The more must-run electricity generation is attributable to PCP of CPPs, the higher are the environmental impacts of these CPPs. This leads to a better relative environmental performance of BESSs in most scenarios. Contrary, comparative or even better environmental performance of CPPs compared to state-of-the-art BESSs can solely be achieved if power plants without load restrictions for provision of primary control and with extreme low efficiency losses caused by PCP are applied. Consequently, the results of this paper indicate that BESSs are a promising option to reduce environmental impacts of primary control provision.

This paper analyses the market conditions for energy storage systems in today's day-ahead and secondary control market. It also deals with the question, to which extend market designs need to be changed to enable the competitiveness of storage systems. On basis of the market development in 2012 the maximal break-even capital expenditures for new storage systems in the day-ahead market are 130 €/kWh. In relation to the actual costs of large scale battery systems it remains clear that batteries are still too expensive to be profitable. For the integration of battery storage systems in the secondary control market a change of the tendering framework is required to offer suitable conditions for providers with a limited storage capacity and operation time. One option would be a market division into two or more segments according to the control demand, possibly with a further reduction of the tendering period to one day or hours.

Abstract and ConclusionThe contribution points out modelling results from a techno-economic analysis of battery supported PV systems. Especially the ratio of the installed PV peak power to the useable capacity of the battery has a big impact on the rate of self-consumption, autarky and economic efficiency. Further on the impact of different household load profiles is analysed with focus on cost optimised system designs. The calculations are model-based and take into consideration the consumer load profile, technical and economical PV and battery system parameters as well as the framework of regulation. Results include the cost optimal system configuration, the operator's share of self-consumption and degree of autarky, grid feed-in and supply and various battery system parameters. One key finding is the importance to use realistic load profiles because otherwise the modelling results can be too optimistic for self-consumption and total costs. That is especially the case for aggregated profiles that do not represent a real consumer.

Abstract The techno-economic analysis investigates first the impact of tilt angle and orientation on the production profile of a rooftop solar generator and the related performance of a photovoltaic battery storage system for single family houses at a specific location in Germany. Then, a technical comparison to a different location in Almeria in Spain is performed. The calculations are model-based and take into consideration the consumer load profile, technical and economic photovoltaic battery storage system parameters as well as the framework of regulations for the case of Germany. The parameters “share of self-consumption”, “degree of autarky”, and “economic efficiency in terms of levelized cost of electricity” make up the focus of the modelling results. It is concluded that self-consumption and degree of autarky are strongly and inversely related. In terms of system design, a trade-off has to be made between aiming for high self-consumption and a high degree of autarky. Key findings from the modelling results reveal that in Lindenberg in Germany, a south orientation gives the highest degree of autarky and the lowest levelized cost of electricity, but with the lowest share of self-consumption as well. For rooftops oriented towards east/west, an interesting possibility could be to split the total installed capacity (equally) between the two orientations. This makes it possible to benefit from the high self-consumption of the east orientation and the high degree of autarky of the west orientation. In general, it has to be considered that the optimum orientation strongly depends on the consumer load profile. The technical analysis shows that changing the location to Almeria increases degree of autarky and decreases share of self-consumption for south orientation with different magnitude that depends on the load profile. Finally, the results show opposite impacts that depend on orientation and location when switching from a tilt angle of 30° to 45°. For a south orientation in Almeria and Lindenberg, the degree of autarky is increased when approaching the optimum tilt angle, while for west and east orientations in Lindenberg self-consumption increases.

Abstract This contribution presents cost optimisation results from a techno-economic perspective of photovoltaic battery systems. The simulation based optimisation takes into consideration temporal high-resolution consumer load and PV production profiles, technical and economical PV and battery system parameters as well as the regulatory framework in Germany. The results include the cost optimal system configuration under the given framework, the share of self-consumption, degree of autarky, grid feed-in and supply as well as various battery system parameters. The ratio of the installed PV peak power to the useable capacity of the battery was found to have a significant impact on self-consumption, autarky and economic efficiency of the overall system and is one of technical key parameters for a cost-optimised system sizing. The break-even battery system price compared to PV systems without BESS is calculated to approx. 900 €/kWh (without BESS support scheme) to 1200 €/kWh (with German BESS support scheme). However, the individual taxation of revenues can lower the break-even costs significantly. Furthermore, the techno-economic analysis identifies a high sensitivity to regulation frame conditions and support schemes of PV and BESS for cost optimisation. Another key finding is that realistic load and production profiles must be used in order to allow for reliable statements concerning technical parameters and economic feasibility. Otherwise, cost optimisation results might overestimate self-consumption and lead to an incorrect calculation of the total costs.

Abstract Regarding the supply of primary control reserve (PCR), stationary battery energy storage systems (BESS) are a promising alternative to fossil fuel power plants. They offer the ability to respond fast and precisely to grid frequency deviations and may contribute to reducing the must-run capacity of fossil fueled power plants. In Germany, primary control reserve is traded on a separate auction market with specific regulations, which enable the BESS to use a number of measures to balance its charge level and preserve operability. However, little is known about how the requirements from primary control deployment and the measures to keep the BESS operational during PCR contract periods affect operational parameters of the system. This study investigates the impact of operation strategies on different parameters including energy exchange through schedule transactions, total energy turnover, full cycle equivalents (FCE), and state-of-charge (SOC) distributions in a case study for a 2 MWh BESS under the German regulatory framework. The results of this study are key to the economic assessment of BESS providing PCR, to an optimization of BESS operation, and to an estimate of battery aging in this specific application field. Based on battery operation simulations, individual elements of operation strategies are identified and their influence on BESS operational parameters is analyzed in a parameter variation. These elements include the chosen measures for charge level management, the SOC ranges, within which these measures are used, parameters defining the schedule transactions, and the prequalified power rating of the BESS. The results show that the choice of the measures for charge level management, the choice of schedule transaction parameters and the prequalified power rating of the BESS have a major impact on energy exchange through schedule transactions. The choice of the measures for charge level management and the choice of schedule transaction parameters have limited influence on the total energy turnover and the resulting number of FCE. These values are mainly influenced by the system design.