@article{IgiligiVielhauerEhrenwirthetal.2023, author = {Igiligi, Anthony and Vielhauer, Armin and Ehrenwirth, Mathias and Hurm, Christian and Summ, Thorsten and Trinkl, Christoph and Navarro Gevers, Daniel}, title = {Assessment of Conservation Voltage Reduction in Distribution Networks with Voltage Regulating Distribution Transformers}, volume = {16}, pages = {3155}, journal = {Energies}, number = {7}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en16073155}, year = {2023}, abstract = {The application of voltage reduction in medium and low voltage grids to reduce peak power demand or energy consumption has been implemented since the 1980s using several approaches. Conservation Voltage Reduction (CVR), as one such approach, uses a voltage control device to reduce or increase the voltage setpoint on a busbar, thereby reducing or increasing the amount of active and reactive power supply in the network. Voltage regulation for CVR is always implemented according to established network planning standards in each country. Research in this field has proven that a CVR factor (CVRf) of 0.7-1.5 for peak demand reduction can be achieved. This is an evaluation metric of CVR. The aim of this research is to determine and validate CVRf for peak demand reduction by comparing actual results obtained during regular tap changes with other randomly distributed periods outside tap change operations, using a set of measurement data. It is important to understand CVR deployment capability by evaluating CVR potentials from historical random tap operations before a robust network-wide deployment is introduced. This research provides such guidance. It also provides a novel approach to determining tap changes from voltage measurements using a time-based algorithm. A CVRf ranging from 0.95 to 1.61 was estimated using a measurement dataset from a test field. The result of the entire evaluation shows that the CVRf are smaller during peak PV production and greater during peak demand periods. Further evaluation using statistical hypotheses testing and a control chart was used to validate the evaluation.}, language = {en} } @article{SummOyinlolaKhattaketal.2023, author = {Summ, Thorsten and Oyinlola, Muyiwa and Khattak, Sanober and Trinkl, Christoph and Z{\"o}rner, Wilfried}, title = {Statistical analysis of solar thermal collectors in the Solar Keymark Database}, volume = {2024}, pages = {103581}, journal = {Sustainable Energy Technologies and Assessments}, number = {61}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2213-1396}, doi = {https://doi.org/10.1016/j.seta.2023.103581}, year = {2023}, abstract = {Experimental, analytical, or numerical investigations are ordinarily conducted to reveal optimisation potential for solar thermal collectors. At the same time, the 'Solar Keymark Database' contains more than 2,000 test reports from certified laboratories featuring properties including thermal efficiency, dimensions, or optical properties. This dataset offers untapped potential for statistical analyses as an alternative optimisation approach. Hence, this paper aims to provide a) the first statistical findings of solar thermal collector properties listed in the Solar Keymark Database and b) insights into statistical relations between these properties. The key correlations observed from the analysis of flat-plate collectors were between efficiency and both gross height (R = 0.30) and gross area (R = 0.27). We concluded that preferable collector designs may be featured with larger area to height ratios. The analyses of evacuated tube collectors revealed a strong correlation between efficiency and transversal incidence angle modifier (R = -0.65) as a result from different tube spacing. It was noticeable that the quasi-dynamic test method reported significantly higher efficiencies (7.14 percentage points) for evacuated tube collectors, which should be carefully considered for future test procedures. Overall, the statistical analysis was in accordance with conventional bottom-up analyses and revealed insightful dependencies for the present collector data.}, language = {en} } @article{SummEhrenwirthTrinkletal.2023, author = {Summ, Thorsten and Ehrenwirth, Mathias and Trinkl, Christoph and Z{\"o}rner, Wilfried and Pischow, Kaj and Greenough, Richard and Oyinlola, Muyiwa}, title = {Effect of argon concentration on thermal efficiency of gas-filled insulating glass flat-plate collectors}, volume = {2023}, pages = {120657}, journal = {Applied Thermal Engineering}, number = {230, Part A}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-5606}, doi = {https://doi.org/10.1016/j.applthermaleng.2023.120657}, year = {2023}, abstract = {Insulating glass flat-plate collectors can save cost by being produced quickly and automatically in insulated glass production facilities, and they can be filled with argon to reduce heat loss. During its lifetime, the collector is likely to lose argon because of gradual material degradation of the sealing. However, information on the influence of the argon concentration on the collector efficiency is limited. Therefore, the objective of this research work was to analyse this effect. A theoretical material property calculation of argon-air mixtures was carried out to determine the convective losses with variable argon concentrations. Thermal collector performance was measured experimentally using an outdoor solar tracker test rig. The results strongly suggest, that the influence of argon concentration on both the convective losses and the thermal efficiency is non-linear. The measurements revealed that an argon concentration of 90 \% can increase average thermal performance by 6.7 ± 4.8 percentage points. An increase in argon concentration from 0 \% to 50 \% has almost twice the effect on average thermal efficiency as an increase from 50 \% to 90 \%. Concluding from these results, an argon leakage threshold of 2.5 percentage points per year is proposed to avoid disproportionate loss of efficiency over time.}, language = {en} } @article{BachseitzSheryarSchmittetal.2024, author = {Bachseitz, Michael and Sheryar, Muhammad and Schmitt, David and Summ, Thorsten and Trinkl, Christoph and Z{\"o}rner, Wilfried}, title = {PV-Optimized Heat Pump Control in Multi-Family Buildings Using a Reinforcement Learning Approach}, volume = {17}, pages = {1908}, journal = {Energies}, number = {8}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en17081908}, year = {2024}, abstract = {For the energy transition in the residential sector, heat pumps are a core technology for decarbonizing thermal energy production for space heating and domestic hot water. Electricity generation from on-site photovoltaic (PV) systems can also contribute to a carbon-neutral building stock. However, both will increase the stress on the electricity grid. This can be reduced by using appropriate control strategies to match electricity consumption and production. In recent years, artificial intelligence-based approaches such as reinforcement learning (RL) have become increasingly popular for energy-system management. However, the literature shows a lack of investigation of RL-based controllers for multi-family building energy systems, including an air source heat pump, thermal storage, and a PV system, although this is a common system configuration. Therefore, in this study, a model of such an energy system and RL-based controllers were developed and simulated with physical models and compared with conventional rule-based approaches. Four RL algorithms were investigated for two objectives, and finally, the soft actor-critic algorithm was selected for the annual simulations. The first objective, to maintain only the required temperatures in the thermal storage, could be achieved by the developed RL agent. However, the second objective, to additionally improve the PV self-consumption, was better achieved by the rule-based controller. Therefore, further research on the reward function, hyperparameters, and advanced methods, including long short-term memory layers, as well as a training for longer time periods than six days are suggested.}, language = {en} }