@inproceedings{34155,
author = {{Krauter, Stefan and Bendfeld, Jörg}},
booktitle = {{Proceedings of the 8th World Conference on Photovoltaik Energy Conversion}},
location = {{Milano / Italy}},
title = {{{Microinverter PV Systems: New Efficiency Rankings and Formula for Energy Yield Assessment for any PV Panel Size at different Microinverter types}}},
year = {{2022}},
}
@inproceedings{34156,
author = {{Kakande, Josephine Nakato and Philipo, Godiana Hagile and Krauter, Stefan}},
booktitle = {{Proceedings of the 8th World Conference on Photovoltaik Energy Conversion}},
location = {{Milano / Italy}},
title = {{{Optimal Design of a Semi Grid-Connected PV System for a Site in Lwak, Kenya Using HOMER}}},
year = {{2022}},
}
@article{47961,
abstract = {{Due to failures or even the absence of an electricity grid, microgrid systems are becoming popular solutions for electrifying African rural communities. However, they are heavily stressed and complex to control due to their intermittency and demand growth. Demand side management (DSM) serves as an option to increase the level of flexibility on the demand side by scheduling users’ consumption patterns profiles in response to supply. This paper proposes a demand-side management strategy based on load shifting and peak clipping. The proposed approach was modelled in a MATLAB/Simulink R2021a environment and was optimized using the artificial neural network (ANN) algorithm. Simulations were carried out to test the model’s efficacy in a stand-alone PV-battery microgrid in East Africa. The proposed algorithm reduces the peak demand, smoothing the load profile to the desired level, and improves the system’s peak to average ratio (PAR). The presence of deferrable loads has been considered to bring more flexible demand-side management. Results promise decreases in peak demand and peak to average ratio of about 31.2% and 7.5% through peak clipping. In addition, load shifting promises more flexibility to customers.}},
author = {{Philipo, Godiana Hagile and Kakande, Josephine Nakato and Krauter, Stefan}},
issn = {{1996-1073}},
journal = {{Energies}},
keywords = {{Energy (miscellaneous), Energy Engineering and Power Technology, Renewable Energy, Sustainability and the Environment, Electrical and Electronic Engineering, Control and Optimization, Engineering (miscellaneous), Building and Construction}},
number = {{14}},
publisher = {{MDPI AG}},
title = {{{Neural Network-Based Demand-Side Management in a Stand-Alone Solar PV-Battery Microgrid Using Load-Shifting and Peak-Clipping}}},
doi = {{10.3390/en15145215}},
volume = {{15}},
year = {{2022}},
}
@inproceedings{22217,
author = {{Krauter, Stefan and Khatibi, Arash}},
booktitle = {{Tagungsband des 36. PV-Symposium, 18.-26 Mai 2021, online, ISBN 978-3-948176-14-3, S. 301-304. }},
isbn = {{978-3-948176-14-3}},
location = {{Staffelstein / online}},
pages = {{301--304}},
publisher = {{Conexio}},
title = {{{Einfluss von Steilaufstellung, Nachführung und Einsatz bifazialer PV-Module auf den Speicherbedarf und die Kosten einer 100% EE-Versorgung Deutschlands}}},
year = {{2021}},
}
@inproceedings{24551,
abstract = {{Access to precise meteorological data is crucial to be able to plan and install renewable energy systems
such as solar power plants and wind farms. In case of solar energy, knowledge of local irradiance and air temperature
values is very important. For this, various methods can be used such as installing local weather stations or using
meteorological data from different organizations such as Meteonorm or official Deutscher Wetterdienst (DWD). An
alternative is to use satellite reanalysis datasets provided by organizations like the National Aeronautics and Space
Administration (NASA) and European Centre for Medium-Range Weather Forecasts (ECMWF). In this paper the
“Modern-Era Retrospective analysis for Research and Applications” dataset version 2 (MERRA-2) will be presented,
and its performance will be evaluated by comparing it to locally measured datasets provided by Meteonorm and DWD.
The analysis shows very high correlation between MERRA-2 and local measurements (correlation coefficients of 0.99)
for monthly global irradiance and air temperature values. The results prove the suitability of MERRA-2 data for
applications requiring long historical data. Moreover, availability of MERRA-2 for the whole world with an acceptable
resolution makes it a very valuable dataset.}},
author = {{Khatibi, Arash and Krauter, Stefan}},
booktitle = {{Proceedings of the 38th European Photovoltaic Solar Energy Conference and Exhibition (EUPVSEC 2021)}},
isbn = {{3-936338-78-7}},
keywords = {{Energy potential estimation, Photovoltaic, Solar radiation, Temperature measurement, Satellite data, Meteonorm, MERRA-2, DWD}},
pages = {{1141 -- 1147}},
title = {{{Comparison and Validation of Irradiance Data: Satellite Meteorological Dataset MERRA-2 vs. Meteonorm and German Weather Service (DWD)}}},
doi = {{10.4229/EUPVSEC20212021-5BV.4.11}},
year = {{2021}},
}
@inproceedings{24550,
abstract = {{Efficiencies and energy yields of microinverters available on the market during 2014‒2021 have been
measured, compared, and ranked. Conversion efficiencies as a function of load have been measured indoors with high
accuracy and ranked according to Euro- and CEC weightings. Energy yields have been measured outdoors via
identical and calibrated crystalline silicon PV modules of 215 Wp (until 2020) and 360 Wp (starting 2021). Inverters
with two inputs have been fed by two of those modules. DC input, AC power output and energy yield of each microinverter have been recorded by individual calibrated electricity meters. CEC and EU efficiency rankings have been
computed and compared. To assess the influence of PV module size, two extremes have been investigated: A rather
small module with 215 Wp - as it has been used 10 years ago, and a brand-new module (2021) offering 360 Wp. Both
types of modules contain 60 solar cells in series connection. Appling the low-power modules, the challenge for the
different micro-inverters has been during weak-light conditions, using the high-power modules, some inverters
temporarily reach their power limits and yield is reduced. A method using a reference configuration of inverter &
module and a linear equation y = ax + b resulting in the actual yield, any module & inverter configuration can be
characterized by just the coefficients a and b.}},
author = {{Krauter, Stefan and Bendfeld, Jörg}},
booktitle = {{Proceedings of the 38th European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC 2021)}},
isbn = {{3-936338-78-7}},
keywords = {{AC-modules, Microinverter, Power Conditioning, Efficiency, Yield, PV module size, saturation, performance}},
pages = {{659 -- 663}},
title = {{{Module-Inverters (Microinverters): Influence of Module Size on Conversion Efficiencies and Energy Yields}}},
doi = {{10.4229/EUPVSEC20212021-4CO.3.4}},
year = {{2021}},
}
@article{21265,
abstract = {{Fast-growing energy demand of the world makes the researchers focus on finding new energy sources or optimizing already-developed approaches. For an efficient use of solar and wind energy in an energy system, correct design and sizing of a power system is of high importance and improving or optimizing the process of data obtaining for this purpose leads to higher performance and lower cost per unit of energy. It is essential to have the most precise possible estimation of solar and wind energy potential and other local weather parameters in order to fully feed the demand and avoid extra costs. There are various methods for obtaining local data, such as local measurements, official organizational data, satellite obtained, and reanalysis data. In this paper, the Modern-Era Retrospective analysis for Research and Applications dataset version 2 (MERRA-2) dataset provided by NASA is introduced and its performance is evaluated by comparison to various locally measured datasets offered by meteorological institutions such as Meteonorm and Deutscher Wetterdienst (DWD, or Germany’s National Meteorological Service) around the world. After comparison, correlation coefficients from 0.95 to 0.99 are observed for monthly global horizontal irradiance values. In the case of air temperature, correlation coefficients of 0.99 and for wind speed from 0.81 to 0.99 are observed. High correlation with ground measurements and relatively low errors are confirmed, especially for irradiance and temperature values, that makes MERRA-2 a valuable dataset, considering its world coverage and availability.}},
author = {{Khatibi, Arash and Krauter, Stefan}},
issn = {{1996-1073}},
journal = {{Energies}},
keywords = {{Solar irradiance, MERRA 2, Meteonorm, DWD}},
number = {{4}},
publisher = {{MDPI}},
title = {{{Validation and Performance of Satellite Meteorological Dataset MERRA-2 for Solar and Wind Applications}}},
doi = {{10.3390/en14040882}},
volume = {{14}},
year = {{2021}},
}
@inproceedings{22218,
author = {{Krauter, Stefan and Böcker, Joachim and Freitag, Christine and Hehenkamp, Burkhard and Hilleringmann, Ulrich and Temmen, Katrin and Klaus, Tobias and Rohrer, Nicolaus and Lehmann, Sven}},
booktitle = {{Tagungsband des 36. PV-Symposiums, 18.-26 Mai 2021}},
isbn = {{978-3-948176-14-3}},
keywords = {{Art-D, Afrika, Resilienz, Resilience, Grid stability, robustness, microgrids}},
location = {{Staffelstein / online}},
pages = {{305--309}},
publisher = {{Conexio}},
title = {{{Projekt Art-D Grids: Nachhaltige und stabile Microgrids in Afrika - eine Plattform für Forschung und Lehre für die Entwicklung}}},
year = {{2021}},
}
@inproceedings{24540,
abstract = {{With its growing population and industrialization, DREs, and solar technologies in particular, provide a
sustainable means of bridging the current energy deficit in Africa, increasing supply reliability and meeting future
demand. Data acquisition and data management systems allow real time monitoring and control of energy systems as
well as performance analysis. However commercial data acquisition systems often have cost implications that are
prohibitive for small PV systems and installations in developing countries.
In this paper, a multi-user, multi-purpose microgrid database system is designed and implemented. MAVOWATT
270 power quality analyzers by GOSSEN METRAWATT, raspberry pi modules and sensors are used for measuring,
recording and storing electrical and meteorological data in East Africa. Socio-economic data is also stored in the
database. The designed system employs open source software and hardware solutions which are best suited to
developing regions like East Africa due to the lower cost implications.
The expected results promise a comprehensive database covering different electro-technical and socio-economic
parameters useful for optimal design of microgrid systems.}},
author = {{Kakande, Josephine Nakato and Philipo, Godiana Hagile and Krauter, Stefan}},
booktitle = {{Proceedings of the 38th European Photovoltaic Solar Energy Conference and Exhibition (EUPVSEC 2021)}},
isbn = {{3-936338-78-7}},
keywords = {{Art-D, Afrika, Demand side management, MySQL, Raspberry pi, Data acquisition}},
pages = {{1505--1510}},
title = {{{Load Data Acquisition in Rural East Africa for the Layout of Microgrids and Demand–Side–Management Measures}}},
doi = {{10.4229/EUPVSEC20212021-6BV.5.38}},
year = {{2021}},
}
@inproceedings{18390,
abstract = {{ Efficiencies and energy yields of microinverters available on the market during 2014‒2020 have been
measured, compared, and ranked. Conversion efficiencies as a function of load have been measured indoors with high
accuracy and ranked according to Euro- and CEC weightings. Energy yields have been measured outdoors via
identical and calibrated crystalline silicon PV modules of 215 Wp each. Inverters with two inputs have been fed by
two of those modules. DC input, AC power output and energy yield of each micro-inverter have been recorded by
individual calibrated electricity meters. Apparently, some inverters have been optimized for high irradiance levels
and ranked better at the CEC efficiency ranking, others performed very well also at low irradiance levels, thus
ranking higher at in the EU efficiency ranking. Efficiency ranks are slightly deviating from rankings by energy yield
measurements. At one inverter, a slow MPPT algorithm that barely could follow quickly changing irradiance levels is
most probably responsible for this effect. Another inverter switched off for a while after operation at high power,
another one failed permanently. Apparently, some inverters are been optimized to show excellent datasheet ratings
for EU- or CEC- efficiency. On the other hand, two inverters (each featuring two inputs) did not show an outstanding
performance at the EU- and CEC-ratings but achieved leading ranks for AC energy yields. For the customer, AC
yield is a major performance indicator of a microinverter and should be included in the datasheet.}},
author = {{Krauter, Stefan and Bendfeld, Jörg}},
booktitle = {{Proceedings of the EUPVSEC 2020}},
isbn = {{ 3-936338-73-6}},
location = {{online}},
pages = {{935 -- 938}},
title = {{{Micro-Inverters: An Update of Comparison of Conversion Efficiencies and Energy Yields}}},
doi = {{10.4229/EUPVSEC20202020-4DO.7.2}},
year = {{2020}},
}
@inproceedings{16857,
author = {{Krauter, Stefan and Bendfeld, Jörg}},
booktitle = {{Tagungsband des 35. Symposiums für Photovoltaische Solarenergie, Kloster Banz, Bad Staffelstein (Deutschland)}},
location = {{Bad Staffelstein}},
title = {{{Einfluss der Betriebstemperatur auf den Wirkungsgrad von Modul-Wechselrichtern für PV-Netzeinspeisungen}}},
year = {{2020}},
}
@inproceedings{19393,
abstract = {{To provide a simple instrument to operate residential Load-Shifting or Demand-Side-Management
systems, the measurement of the actual grid frequency seems to be an appropriate method. Due to the present
inflexibility and the lack of sufficient throttling capabilities of lignite and nuclear power plants, a surplus of
electricity generation occurs during periods of high wind and solar power generation. While the specific CO2-
emission is decreasing then ‒ due to the increased share of Renewables, the grid frequency is increasing (to a certain
limit). Using the grid frequency as an indicator to switch-on and off certain loads (loads that do not require power
permanently (e.g. dishwashers, washing machines, dryers, fridges and freezers, heaters) could provide a simple,
inexpensive demand-side management indicator to lower specific CO2‒emssions and costs (if a dynamic
consumption tariff is available). To check the truthfulness of that hypothesis, the grid and frequency data of the
German grid of the year 2018 have been collected and a the correlation between grid frequency, power surplus, share
of renewables vs. CO2-contents and price at the European energy exchange (EEX) have been calculated. The results
show: Correlation between frequency and share of renewables is quite low (r = 0.155) due to the fact that primary
grid control quickly compensates deviations from the 50 Hz nominal frequency. There is a good anti-correlation (r = -
0.687) between the EEX‒prices and the share of renewables in the grid. Over the years, correlation between
electricity trading prices (EEX) and CO2 emissions is quite good (r =0.665), within the one year (2018) that
correlation almost doesn’t exist, possibly due to the inflexibility of the bulky lignite power plants that even operate at
negative prices.
}},
author = {{Krauter, Stefan and Zhang, L.}},
booktitle = {{Proceedings of the 37th European Photovoltaic Solar Energy Conference, 07 - 11 September 2020.}},
issn = {{ 3-936338-73-6}},
keywords = {{Keywords: Load-Shifting, Demand-Side-Management, DSM, grid frequency, EEX, electricity trading prices, renewable share, flexibility, emissions, CO2}},
location = {{online}},
pages = {{1815 -- 1817}},
title = {{{Triggering Demand‒Side‒Management: Correlation of electricity prices, share of renewables, CO2‒contents, and grid‒frequency in the German electricity grid.}}},
doi = {{10.4229/EUPVSEC20202020-6BV.5.9}},
year = {{2020}},
}
@inproceedings{19390,
abstract = {{Due to the strong reduction of PV prices, storage plays a dominating role in overall system costs. A
steeper elevation angle would result in a more balanced seasonal PV yield, at the cost of PV yield reductions during
summer, but allowing reduced storage capacities. Additionally, the effect of a single-axis tracking system has been
investigated, generating more electricity during the morning and evening hours, thus reducing daily storage
requirements. The necessary PV size and storage capacities required for the German energy supply (1,500 TWh after
electrification of all sectors) via 100% renewable energies and a 50% solar share have been calculated via the
HOMER Pro software, considering the bridging of periods of "dark lulls“ in winter, using costs of 2030 (Table 1).
Results: The increase of module elevation angles above the typical 30° leads to a reduction of investment and supply
costs. The optimum is reached at a cost reduction of -1.5% for an elevation angle at the latitude of the installation
site. An explanation is that high elevation angles are favorable for clear winter days, but not at all for the critical days
with diffuse irradiance only, so the battery capacity must be increased. For the same reason, tracking systems do not
offer any cost advantage (at least for the ones without an option for horizontal positioning during diffuse days).}},
author = {{Krauter, Stefan and Rustemovic, D. and Khatibi, Arash}},
booktitle = {{Proceedings of the 37th European Photovoltaic Solar Energy Conference, 07 - 11 September 2020}},
isbn = {{3-936338-73-6}},
keywords = {{Energy Storage, PV system integration, Large Grid-connected PV systems, Simulation, Energy Supply Options}},
location = {{online}},
pages = {{1818 -- 1819}},
title = {{{Reduction of required storage capacities for a 100% renewable energy supply in Germany, if new PV systems are installed with east-west tracking systems at increased elevation angles}}},
doi = {{10.4229/EUPVSEC20202020-6BV.5.10}},
year = {{2020}},
}
@inproceedings{18387,
abstract = {{ During comparative measurements of different PV microinverters, two yield issues came up that could
not be explored via conventional efficiency measurements, but do have a significant impact on electrical energy
yield: First category of issues are either sluggish or nervously acting maximum–power–point–tracking devices, which
lead to reduced energy yields. The other category of issues is thermal: As a first explanation for observed reduced
energy yields, it has been assumed that the conversion efficiency degrades at higher operating temperatures. This
matter has been investigated in this article: A change in conversion efficiency could not be observed for elevated
operation temperatures up to 50°C, despite high-precision and repeated measurements. But it was found that some
inverters temporarily interrupted (or entirely stopped) operation after long periods of running at high temperatures.
Also, a reduction in potential maximum power output has been detected for those inverters. Summarizing: With a
high degree of certainty it can be stated that those reported yield losses have been caused by the temporary shutdowns
and power limitations of the inverters.}},
author = {{Krauter, Stefan and Bendfeld, Jörg}},
booktitle = {{Proceedings of the EU PVSEC 2020 }},
issn = {{3-936338-73-6}},
keywords = {{AC-modules, Microinverter, Power Conditioning, Thermal Performance, Ventilation, Stability, Efficiency, Yield}},
location = {{online}},
pages = {{1179 -- 1180}},
title = {{{Elevated Temperatures Affecting Efficiency, Overall Performance and Energy Yield of PV Microinverters}}},
doi = {{10.4229/EUPVSEC20202020-4AV.3.6}},
year = {{2020}},
}
@inproceedings{19383,
abstract = {{Due to the present inflexibility and the lack of sufficient throttling capabilities of lignite and nuclear power plants, a surplus of electricity generation occurs during periods of high wind and solar power generation in the German electricity grid. While the specific CO2-emission is decreasing then - due to the increased share of Renewables, the grid frequency should be increasing (to a certain limit). Using the grid frequency as an indicator to switch-on and -off certain loads (loads that do not require power permanently (e.g. dishwashers, washing machines, dryers, fridges and freezers, heaters) could provide a simple, inexpensive demand-side-management indicator to lower specific CO2-emissions and costs (if a dynamic consumption tariff is applied). To check the truthfulness of that hypothesis, the grid and frequency data of the German grid of the year 2018 have been collected and the correlations between grid frequency, share of renewables, CO2-contents, and actual price at the European energy exchange (EEX) have been calculated. The results show: Correlation between grid frequency and the share of renewables is quite low (r=0.155) due to the fact that primary grid control quickly compensates deviations from the 50 Hz nominal frequency. As expected, there is a good anti-correlation (r=-0.687) between the EEX-prices and the share of renewables in the grid. Over the years, correlation between electricity trading prices (EEX) and CO2 emissions is quite good (r=0.665), within the one year (2018) that correlation almost doesn't exist, possibly due to the inflexibility of the bulky lignite baseload power plants that even operate at negative prices.}},
author = {{Krauter, Stefan and Zhang, L.}},
booktitle = {{Proceedings of the 47th IEEE Photovoltaic Specialists Conference (PVSC 47) 2020}},
keywords = {{CO2, EEX, Grid frequency, DSM, electricity price, Renewable share}},
location = {{online}},
pages = {{1672--1674}},
title = {{{Correlation of grid-frequency, electricity prices, share of Renewables and CO2-contents of German electricity grid to enable inexpensive triggering of Demand-Side-Management}}},
doi = {{10.1109/PVSC45281.2020.9300487}},
year = {{2020}},
}
@inproceedings{16899,
abstract = {{To compare efficiency and yield of many micro-inverters available on the world market in 2014-2020, an in- and outdoor test laboratory at the University of Paderborn has been set up. The inverters have been fed by identical and calibrated crystalline silicon PV modules of 215 Wp. To monitor accurately DC input, AC power output and energy yield, each of the micro-inverters has been equipped with a calibrated electricity meter. For micro-inverters requiring control units for grid-feeding that has been acquired also. The comparison covers efficiency-load characteristics as well as electrical energy yields. Purchase costs vary considerably between the models in comparison, sometimes inverter costs are higher than module costs, particularly if an additional grid-connection or interface device is needed for operation. The weighted conversion efficiency according to EU and CEC standards has been measured and calculated. While some inverters have been optimized for high irradiance levels, they ranked better at the CEC efficiency, others performed very well also for low irradiance levels, thus ranking higher at in the EU-efficiency tables. These results are deviating from the actual energy yield measurements, which show a slightly different ranking. At one inverter, an accurate, but very slow MPPT algorithm that barely could follow quickly changing irradiance levels could be the reason for this effect. Another inverter switched off after operation at high power output for a while. Apparently, some inverters are been optimized to show excellent EU and CEC efficiency ratings. Two of the inverters featuring two inputs did not show an exceptional performance at the EU- and CEC-ratings, but they achieved top ranks at the AC energy yield for the first years. For the customer, the AC yield is a major performance indicator of any microinverter and should be included in the datasheet.}},
author = {{Krauter, Stefan and Bendfeld, Jörg}},
booktitle = {{Proceedings of the 47th IEEE Photovoltaic Specialists Conference (PVSC 47) JUNE 15 - AUGUST 21, 2020 VIRTUAL MEETING}},
issn = {{ 0160-8371}},
keywords = {{yield, AC, micro-inverter, MPPT, CEC rating, EU efficiency, Photovoltaic, Solar}},
location = {{VIRTUAL MEETING}},
pages = {{1429--1432}},
publisher = {{IEEE}},
title = {{{Comparison of Microinverters: Update on Rankings of Conversion Efficiencies and Energy Yields}}},
doi = {{10.1109/PVSC45281.2020.9300953}},
year = {{2020}},
}
@inproceedings{16855,
author = {{Krauter, Stefan and Zhang, L.}},
booktitle = {{Tagungsband des 35. Symposiums für Photovoltaische Solarenergie, Kloster Banz, Bad Staffelstein (Deutschland)}},
location = {{Bad Staffelstein}},
title = {{{Eignung der Netzfrequenz als Instrument der Entscheidungsfindung zur Auslösung von Lastverschiebungen bei niedrigen spezifischen CO2-Emissionen und EEX-Handelspreisen}}},
year = {{2020}},
}
@inproceedings{16858,
author = {{Krauter, Stefan and Zhang, L.}},
booktitle = {{Proceedings of the 14th International Renewable Energy Storage Conference, Düsseldorf (Deutschland), 10.–12. März 2020 (verschoben: 16.–18. März 2021)}},
location = {{Düsseldorf (Deutschland)}},
title = {{{Probability of Correct Decision–Making at Triggering of Load-Shifting Intended for low CO2-intensity and low EEX trading-prices via simple Grid Frequency Monitoring}}},
year = {{2020}},
}
@inproceedings{15247,
author = {{Grabo, Matti and Weber, Daniel and Paul, Andreas and Klaus, Tobias and Bermpohl, Wolfgang and Krauter, Stefan and Kenig, Eugeny}},
location = {{Nordhausen}},
title = {{{Entwicklung eines thermischen 1D-Simulationsmodells zur Bestimmung der Temperaturverteilung in Solarmodulen}}},
year = {{2019}},
}
@inproceedings{15248,
author = {{Grabo, Matti and Weber, Daniel and Paul, Andreas and Klaus, Tobias and Bermpohl, Wolfgang and Kenig, Eugeny}},
location = {{Frankfurt am Main}},
title = {{{Numerische Untersuchung der Temperaturverteilung in PCM-integrierten Solarmodulen}}},
year = {{2019}},
}