@techreport{Budde2021,
  author    = {Budde, Janik},
  title     = {A comparison of reverse electrodialysis and pressure retarded osmosis as technologies for salinity gradient power},
  doi       = {10.25974/ren_rev_2021_14},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136882},
  pages     = {72-78},
  year      = {2021},
  abstract  = {The global salinity gradient power (SGP) potential is between 1650 - 2000 TWH/a and can be converted by mixing two solutions with different salinities. The harnessing of SGP for conversion into power can be accomplished by means of pressure retarded osmosis (PRO) and reverse electrodialysis (RED). PRO and RED are membrane-based technologies and have different working principles. PRO uses a semipermeable membrane to seperate a concentrated salt solution from a diluted solution. The diluted solution flows through the semipermeable membrane towards the concentrated solution, which increases the pressure within the concentrated solution chamber. The pressure is balanced by a turbine and electricity is generated. RED uses the transport of ions through cation and anion exchange membranes. The chambers between the membranes are alternately filled with a concentrated and diluted solution. The salinity gradient difference is the driving force in transporting ions that results in an electric potential, which is then converted to electricity. The comparison shows that there are two different fields of application for PRO and RED. PRO is especially suitable at extracting salinity energy from large concentration differences. In contrast, RED are not effect by increasing concentration differences. So PRO are supposed to focus on applications with brines or waste water and RED on applications with river water and seawater. Moreover, just a few measured values from processes under real conditions are available, which makes it difficult to compare PRO and RED.},
  language  = {en}
}
@techreport{Wagenknecht2021,
  author    = {Wagenknecht, Fiona},
  title     = {Assessment of noise mitigation measures during pile driving of larger offshore wind foundations},
  doi       = {10.25974/ren_rev_2021_04},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136786},
  pages     = {19-23},
  year      = {2021},
  abstract  = {Wind energy is an important source of electricity generation, but the construction of offshore wind foundations causes high underwater sound pressure, harming marine life. In this context limiting values for underwater noise emissions were set to protect the marine flora and fauna. Therefore, noise mitigation measures during pile driving are mandatory to comply with these limits. Current development in the wind industry lead to increasing wind turbine sizes, requiring a larger pile diameter, which leads to higher underwater noise emissions. As a result, the state of the art noise mitigation systems might not be sufficient and a combination of different technologies is necessary. This article focuses on the issue of noise mitigation during pile driving with respect to large pile sizes. First, the most tested and proven noise mitigation techniques (big bubble curtain, hydro sound damper, and IHC-noise mitigation system) are described, following an analysis of noise reduction measurements in applications at different offshore wind farm projects. In the end the suitability of current noise mitigation systems for large monopiles is evaluated, regarding their effectiveness and practicability.},
  language  = {en}
}
@techreport{Linnenschmidt2021,
  author    = {Linnenschmidt, Jan-Niklas},
  title     = {Cost comparison between bottom-fixed and floating offshore wind turbines - Calculating LCOE based on full hours of utilization and corresponding break-even points},
  doi       = {10.25974/ren_rev_2021_02},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136764},
  pages     = {9-12},
  year      = {2021},
  abstract  = {Originally this article was supposed to be a comparison between the technological differences of bottom-fixed offshore wind turbines (BOWT) and floating offshore wind turbines (FOWT). However, several authors already contributed to this topic and came to the conclusion that the higher levelized costs of energy (LCOE) prevent FOWTs from successfully entering the energy market. Multiple sources seem to agree on this conclusion but often do not provide the reader with further information regarding the LCOE. This is the reason why this article understands itself as an in depth cost comparison between BOWTs and FOWTs. For this purpose, individual LCOE are calculated for the upcoming FOWT technologies such as spar-buoy (SPAR), tension-leg platform (TLP) and semi-submersible platform (semi-sub) as well as conventional BOWTs using the wind turbines hours of full utilization (HOFU). The resulting functions are visualized graphically in order to determine break-even points between BOWTs and FOWTs. Finally, a sensitivity analysis is carried out to determine the influence of the weighted average costs of capital (WACC).},
  language  = {en}
}
@techreport{OPUS4-13689,
  title     = {EGU Journal of Renewable Energy Short Reviews},
  editor    = {Vennemann, Peter and Klemm, Christian},
  doi       = {10.25974/ren_rev_2021_00},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136890},
  year      = {2021},
  abstract  = {The EGU Journal of Renewable Energy Short Reviews (EGUJRenEnRev) is a teaching project rather that a regular scientific journal. To publish in this journal, it is a premise to take part in the master course wind power, hydro power and biomass usage at the faculty of Energy, Building Services and Environmental Engineering of the M{\"u}nster University of Applied Sciences. Students receive an equivalent of 2.5 credit points (European Credit Transfer and Accumulation System - ECTS) for their engagement in the course and for publishing a short review article of at most 3000 words in this periodical. The publication process closely mimics the typical publication procedure of a regular journal. The peer-review process, however, is conducted within the group of course-participants. Although being just an exercise, we think that publishing the outcome of this course in a citable manner is not only promoting the motivation of our students, but may also be a helpful source of introductory information for researchers and practitioners in the field of renewable energies. We encourage students to write their articles in English, but this is not mandatory. The reader will thus find a few articles in German language. To further encourage students practicing English writing, perfect grammar is not part of the assessment. We especially thank our students for working with LaTeX on Overleaf, although LaTeX is new to some of them. In this way, the editorial workload was reduced to a minimum. We also thank our students for sharing their work under the creative commons attribution licence (CC-BY). I appreciate their contribution to scientific information, being available to every person of the world, almost without barriers. I also thank the corresponding authors and publishers of the cited work, for granting permission to reuse graphics free of charge. All other figures had to be replaced or removed prior to publication.},
  language  = {de}
}
@techreport{Wittor2021,
  author    = {Wittor, Yannick},
  title     = {Harvesting wind energy through electrostatic wind energy conversion - Comparison with common wind turbines and future possibilities},
  doi       = {10.25974/ren_rev_2021_09},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136832},
  pages     = {48-52},
  year      = {2021},
  abstract  = {Despite their important role in our energy system, common wind turbines have some disadvantages. Mainly, those disadvantages are connected to the intermediate conversion of wind energy in rotational energy. The resulting effects include maintenance costs and social acceptance problems. There are different technological approaches, that convert wind energy to electrical energy without its conversion to kinetic energy. As one of those technologies, the electrostatic wind energy conversion is to be discussed in this article. For this discussion, the historical development of this technology is presented. There are three important projects which will be presented to explain the technology and its different technological approaches. Those projects are the WPG, the EWICON and the SWET. Furthermore the results of those different experimental projects are collected and analyzed. On the basis of this analysis it is discussed, whether or not the electrostatic wind energy conversion could be of importance in a future energy system. Therefore the technology is set in relation to modern wind turbines. Also, important factors that influence the efficiency and energy output of those systems are outlined for further research. Due to different technological approaches a suggestion is made for the most promising system setting.},
  language  = {en}
}
@techreport{Schmeinck2021,
  author    = {Schmeinck, Hendrik},
  title     = {Impact of wind and wave induced platform motion on the aerodynamic properties of floating offshore wind turbines},
  doi       = {10.25974/ren_rev_2021_01},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136750},
  pages     = {3-8},
  year      = {2021},
  abstract  = {With floating offshore wind turbines, new sources of wind energy can be used, which cannot be tapped into by bottom-fixed wind turbine systems. However, due to their design, they experience additional motion caused by wind and wave loads. The motions that are induced into the system have an oscillating course. This affects the aerodynamic properties of the wind turbine and leads to changes in the thrust force and power output of floating wind turbines compared to bottom-fixed wind turbines. Furthermore, the motions lead to an earlier breakdown of the helical wake structure behind the wind turbine and moreover lead to a decreased reliability of the rotor blades. Differences in the effects of wind and wave loads on the aerodynamic performance of floating offshore wind turbines supported by different platform systems were found.},
  language  = {en}
}
@techreport{Scheffler2021,
  author    = {Scheffler, Mark},
  title     = {Low-Cost Hydropower Turbines for Developing Countries},
  doi       = {10.25974/ren_rev_2021_11},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136858},
  pages     = {57-62},
  year      = {2021},
  abstract  = {There are many hydropower turbines for low heads or low flows on a small scale. Many technologies are unsuitable for developing countries because equipment or materials are limited, high-tech machines are to expensive or spare parts are not readily available. This review combines currently available technologies with the requirements of developing countries in small, micro and pico hydropower. In small hydropower a propeller turbine from Thailand has a high efficiency of 70 to 80 percent at calculated production costs of around \$ 513 per kW. Pumps as turbines are suitable for developing countries in micro hydropower due to readily availability, low price and an large number of standard sizes. In pico-scale, a low-cost Turgo wheel can be made of spoons for \$ 48 and yields acceptable values in comparison to a 3D printed Pelton wheel for \$ 822. While the Turgo wheel is suitable for high heads, a homemade siphon turbine can be used for low heads. The siphon turbine generates up to 200 W, is made of materials that are available anywhere in the world, and costs less than \$ 50.},
  language  = {en}
}
@techreport{Hoge2021,
  author    = {Hoge, Alexander},
  title     = {Measures for mitigating avian collision rates with wind turbines - Determining an effective technique regarding effort and effect},
  doi       = {10.25974/ren_rev_2021_08},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136826},
  pages     = {42-47},
  year      = {2021},
  abstract  = {Because of the rapid expansion and widespread application of wind energy the overall environmental impacts of wind power plants have increased as well. For the further development of wind power, methods to lessen the adverse effects wind power has on avian populations have to be implemented. This review aims to find effective methods to reduce avian collision rates with wind turbines and that therefore can reduce bird fatality rates. For the assessment the different mitigation methods, for which concrete data was found, are compared with each other regarding the hypothetical effort of implementation and effectiveness in reducing avian collision rates with wind turbines. These methods are: (a) Coloring of rotor blades (b) Coloring of the tower base (c) Ultraviolet/violet lightning (d) Temporary shut-down of wind turbines (e) Auditory warning signals (f) Repowering All of the mentioned methods report influence on reducing avian collision rates or at least the behavior of birds in flight. This review found the following three methods to be most effective: (a) Coloring of rotor blades (b) Temporary shut-downs of wind turbines (c) Repowering The most effective method to reduce avian collision rates at horizontal axis wind turbines is to paint one of the rotor blades black and consequently increasing the visibility of the rotor blades. The presented study reports 71,9 percent reduction of found carcasses of birds at the treated turbines. For this method the effort of implementation is low while the effectiveness is high. The effectiveness of the found mitigation methods has been proven and they are suited for application. The method of using lightning or sound fields require more testing to determine their effectiveness. Another topic for research could be how different mitigation methods interact with each other. Is there a significant advantage to be had if multiple mitigation methods are applied at the same wind power plant or turbine? Furthermore the environmental impacts of wind turbines are not limited to birds. Other animals like bats are affected too and might require different methods of mitigation.},
  language  = {en}
}
@techreport{Steinigeweg2021,
  author    = {Steinigeweg, Joshua},
  title     = {Review of the suitability of thermoplastic rotor blades in terms of the circular economy},
  doi       = {10.25974/ren_rev_2021_06},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136809},
  pages     = {30-34},
  year      = {2021},
  abstract  = {Wind energy has steadily gained importance in the generation of renewable energy over the last 25 years. A wind turbine has an average life expectancy of about 25 years. After that, thermoplastic composite materials from the rotors, among other things, accumulate and have to be recycled. Previous methods, such as landfilling, incineration and pyrolysis, have not yet proven to be effective in terms of the circular economy because the recycled material cannot be reused for equivalent products. The use of thermoplastic materials can be a sensible alternative, as thermoplastic resins can be recycled almost without loss of value due to their properties. Recycling of fibreglass is also possible with less loss of stiffness. In the future, it will be crucial to scale up thermoplastic rotor blades and create a market for the recycled material.},
  language  = {en}
}
@techreport{Speller2021,
  author    = {Speller, Julian},
  title     = {Self-build small wind turbines - A review},
  doi       = {10.25974/ren_rev_2021_10},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136845},
  pages     = {53-56},
  year      = {2021},
  abstract  = {Self-build small wind turbines are used for rural electrification in the developed and developing world as well as for educational purposes. To give an overview about self-build small wind turbines a systematic literature review was conducted. The identified literature deals with two different vertical and horizontal axis turbine designs. The vertical axis turbines are both prototypes while one of the horizontal axis designs, the design by Piggott is widely used in rural electrification projects. Different papers dealing with the optimization of the Piggott design exist. In retrospect the conduction of a holistic review was not possible due to limited resources and length of this review. Nevertheless it can give a quick overview and a starting point for further research.},
  language  = {en}
}