• Energy Research
• other engineering and technologies close
• DE close
• BE close
• English close

Solar power appears to be one of the most promising resources to meet the medium and long term renewable energy targets. The integration of large amounts of photovoltaic (PV) generation into distribution networks faces some limitations due to the network constraints. The PV community became well aware of these limitations in the last years. While first solutions have been pointed out mainly for large installations connected to the medium voltage network, the specificities of low voltage networks are still not fully understood. This paper aims at explaining the challenges associated to the planning and operation of low voltage network with high PV penetration. The actual impact of PV infeed is quantified on the basis of real and accurate network, load and generation data. Results from unsymmetrical load-flow computations are presented and the implementation of reactive power-based voltage control is shortly discussed. 26th European Photovoltaic Solar Energy Conference and Exhibition; 4469-4478

Recently two approaches to extend the photoluminescence imaging (PLI) technique by evaluating the dynamic properties of the sample have been presented. Time-resolved photoluminescence measurements may provide calibration-free maps of the effective minority charge carrier lifetime in silicon wafers. Due to the transient measurement they minimize errors due to lateral inhomogeneities in setup or sample, which would usually contribute linearly to steady-state PLI measurements. In this work, we will focus on mechanically shuttered time-resolved photoluminescence imaging (TR-PLI), as it provides a high measurement range down to 5 μs at low hardware costs. 26th European Photovoltaic Solar Energy Conference and Exhibition; 1463-1466

Changing PV market conditions foster the use of PV storage systems and bring new challenges to the grid. This paper analyzes the influence of PV and PV battery systems on the voltage unbalance and the voltage magnitude. Different system topologies are evaluated by simulating their behavior in two different test grids. A sensitivity analysis is performed varying the size of the PV system, the size of the battery, the grid penetration of the systems and the phase connection. The analysis shows that voltage unbalance problems can occur in case of same phase connection of the systems. The results suggest that PV battery systems mitigate the problem for the two example grids depending on the PV power and battery size. For grids with equally distributed phase connections of either PV or PV battery systems, no violations of the voltage unbalance criterion are observed. 27th European Photovoltaic Solar Energy Conference and Exhibition; 3822-3828

Purpose:This research aims to develop a framework of sustainability performance measurement and to propose sustainability impact criteria that can be used to meas-ure complex sustainability impacts in the manufacturing industry. Methodology:Fuzzy-Analytical Hierarchy Process (Fuzzy-AHP) and the Delphi method were used to calculate the weights of sustainability impact criteria. Then, the impact pathway of a life cycle assessment was constructed to illustrate the inter-relationship between each impact criterion. A proposed framework of sustainability performance measurement is presented along with the suggested sustainability im-pact criteria.Findings:Based on the Delphi method and Fuzzy-AHP, the environmental aspect is the area that has received the highestconcern (49.4%). The important endpoint im-pact criteria of the environmental aspect consist of Effect on global climate, Ecosys-tem quality, Animal biodiversity, and Resource management. Originality: The biggest challenge of sustainable development that is yet to be an-swered is how to measure sustainability performance. The environmental aspect is the area that has received the most attention while the economic and social aspects are still under-represented. To fill the gap, this research proposes a framework of sustainability performance measurement that considers all interrelationships be-tween each sustainability aspect

The EFQM excellence model is a famous quality management tool. We have translated it to be useful in e-learning quality management. EFQM will be used as a framework for self-evaluation. We developed the e-learning stakeholder model. We identified the main criterion and positioned them in the stakeholder model.We present short the Kirkpatrick evaluation model of e-learning.We developed a Kirkpatrick-EFQM self-assessment framework. We propose the limited learner-centric self-assessment framework. A preliminary set of quality criteria have been identified for self-assessment by the learners.

The presented study investigates the hardness and sliding wear behavior of cemented carbides and high-speed tool steels at elevated temperatures. Therefore, experimental analysis focus on the behavior and the microstructural changes of the aforementioned materials during sliding wear at room temperature, 400°C, and 600°C. Investigations are performed with respect to materials mechanical properties, which are represented by high temperature hardness measurements. As a result a main output of this study is an overview about the interdependencies of the microstructure and the high temperature hardness of tool materials (cemented carbides, high-speed steels). Results show that the absolute value of the room temperature and the high temperature hardness of cemented carbides are connected to the WC-carbide volume fraction. In contrast, the development of the hardness with increasing temperature is mainly influenced by the volume fraction and the characteristics of the binder matrix. In addition to the investigation of cemented carbides, the hardness of HS 6-5-3 steel grade at elevated temperatures was investigated. The value of the high temperature hardness of HS 6-5-3 high-speed steel is comparable to the hardness of cemented carbide materials, having higher binder content of 30 vol.-%.The absolute value and the temperature dependent course of the high temperature hardness of the high-speed steel are further influenced by the applied heat-treatment. Moreover, detailed wear experiments and microscopic analyses of the worn surfaces of selected materials are presented. These investigations show the main differences between room temperature sliding wear and high temperature sliding wear. In the systems studied, an increase in testing temperature leads to a rapid decrease of friction and wear rate. Microscopic investigations reveal that, the reason for this effect is the formation of a tribochemical wear layer at the surface of the wear bodies. This layer suppresses direct metallic contact and changes the characteristics of the tribological system. Discussed issues of high temperature sliding wear are the formation and stability of tribochemical wear layers, their connection to and support by the bulk material as well as the fracturing and damage of the layer-bulk-material compound. International Conference on Stone and Concrete Machining (ICSCM), Vol 3 (2015)

Highly conductive ZnO:Al films are often used as a transparent conductive oxide (TCO) in photovoltaic devices. The high optical gap, high conductivity, high stability in hydrogen plasma, and the relative abundance of the composing elements make ZnO:Al ideal for application in mass production of silicon thin-film technology. The long-term electrical stability is an important issue. To investigate degradation processes, accelerated aging in a damp-heat was carried out in both H2O and D2O environments. A decrease in conductivity is observed over a period of 1000 hour, in particular for surface etched samples. We show that the sample degradation is caused by grain boundary modifications and suggest a barrier model to explain the observed degradation. The deuterium isotope was used as a marker for secondary ion mass spectrometry (SIMS) measurements to distinguish between hydrogen incorporated during or just after deposition and deuterium incorporated during the damp-heat treatment. SIMS measurements show a linear build-up of deuterium in samples treated up to 300 hours, as well as a D-H replacement mechanism. This suggests weak bonds exist between ZnO and H2O, and may explain the partial reversibility of damp-heat degradation observed by others. 24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 2774-2778

Stopping and accelerating at traffic lights is one of the main contributing factors to vehicular emissions in urban environments. The work in this paper demonstrates a generic guideline for minimizing CO2 emissions at traffic lights. This was done using an adaptive control, which uses a cost function for optimization, rather than network-specific control parameters. A new version of the emission model PHEMlight was used, which added of a fuel cut-off mode during coasting and other improvements compared to the previous version. Using this model, it could be determined that the emission optimal ratio between delay time and stops for the cost function of an adaptive control should be 1:4.8. Using this ratio a reduction of 7.6 % of CO2 emissions was achieved compared to a vehicle actuated control.