TY - JOUR A1 - Candra, Dodiek Ika A1 - Hartmann, Kilian A1 - Nelles, Michael T1 - Economic Optimal Implementation of Virtual Power Plants in the German Power Market JF - MDPI energies N2 - The burden of excess energy from the high renewable energy sources (RES) share creates a significant reduction of residual load for the future, resulting in reduced market prices. The higher the share of stochastic RES, the more often the price will be 0 €/MWh. The power market needs new methods to solve these problems. The development of virtual power plants (VPPs) is aimed at solving techno-economic problems with an increasing share of RES in the power market. This study analyses a possible implementation of stochastic and deterministic RES in a VPP to generate secured power, which can be implemented in the European Power Exchange (EPEX)/European Energy Exchange (EEX) power market using existing market products. In this study, the optimal economic VPP configuration for an RES-based power plant is investigated and implemented into standard power market products. The results show that the optimal economic VPP configuration for different market products varies, depending on the energy availability and the marginal costs of the VPP components. The size of the VPP components is positively correlated to the components’ share of the energy generated. It was also found that projecting or implementing VPPs in Germany at current market prices (EPEX/EEX prices) is not yet economically feasible for a small share of market products. However, the secured power can be marketed on the SPOT and in the futures market with higher and more stable prices compared with the status quo. KW - VPP; marketing; configuration; energy transition; power market; EPEX; EEX; power market products KW - Elektrizitätsmarkt KW - Virtuelles Kraftwerk Y1 - 2018 UR - https://www.mdpi.com/1996-1073/11/9/2365 U6 - https://doi.org/10.3390/en11092365 VL - 11 IS - 11/09 SP - 2365 EP - 2373 ER - TY - JOUR A1 - Wilches, Camilo A1 - Nelles, Michael A1 - Hartmann, Kilian T1 - Representative sampling Implementation in Online VFA/TIC Monitoring for Anaerobic Digestion JF - MDPI energies N2 - This paper describes an automatic sampling system for anaerobic reactors that allows taking representative samples following the guidelines of Gy’s (1998) theory of sampling. Due to the high heterogeneity degree in a digester the sampling errors are larger than the analysis error, making representative sampling a prerequisite for successful process control. In our system, samples are automatically processed, generating a higher density of data and avoiding human error by sample manipulation. The combination of a representative sampling system with a commercial automate titration unit generates a robust online monitoring system for biogas plants. The system was successfully implemented in an operating biogas plant to control a feeding-on-demand biogas system. KW - renewable energies KW - biogas KW - process control KW - Erneuerbare Energien KW - Biogas KW - Biogasanlage Y1 - 2019 UR - https://www.mdpi.com/1996-1073/12/6/1179 U6 - https://doi.org/https://doi.org/10.3390/en12061179 VL - 12 IS - 12/06 SP - 1179 EP - 1186 ER -