@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}
}
@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{Hinse2021,
  author    = {Hinse, Michael},
  title     = {The Wells turbine: state of the art},
  doi       = {10.25974/ren_rev_2021_12},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136861},
  pages     = {63-66},
  year      = {2021},
  abstract  = {The first oscillating water column was invented in 1940. In the past decades the need of wave energy systems has significantly increased. This article quickly describes the Wells turbine and possibilities to enhance its performance and should answer the question: what are the design parameters that can be optimized? Furthermore it gives a small outlook about the history of oscillating Water Columns.},
  language  = {en}
}
@techreport{Olbertz2021,
  author    = {Olbertz, Niklas},
  title     = {Sustainable hydro-power plants with focus on fish-friendly turbine design},
  doi       = {10.25974/ren_rev_2021_13},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-136876},
  pages     = {67-71},
  year      = {2021},
  abstract  = {The impact of hydro-power plants on the ecosystem was studied with focus on the fish mortality and types of damage for many years. The fish mortality have a wide range of causes. Types of damage can be different and are caused by different parts of the power plant. The most dangerous part of the system are the fast moving turbine blades. They can cause blade strike and barotrauma due to the high speeds. Different types of turbines were developed for a better survival rate. Five different types of different research groups and manufacturers are presented in this paper. By considering those newly developed turbine designs, a fish survival rate from 96 \% to 100 \% is achieved.},
  language  = {en}
}
@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{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{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{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}
}
@article{KlemmWiese2022,
  author    = {Klemm, Christian and Wiese, Frauke},
  title     = {Indicators for the optimization of sustainable urban energy systems based on energy system modeling},
  series = {Energy, Sustainability and Society},
  volume    = {12},
  journal   = {Energy, Sustainability and Society},
  number    = {3},
  publisher = {Springer Nature},
  doi       = {10.25974/fhms-14513},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-145136},
  pages     = {1 -- 20},
  year      = {2022},
  abstract  = {Background: Urban energy systems are responsible for 75 \% of the world's energy consumption and for 70 \% of the worldwide greenhouse gas emissions. Energy system models are used to optimize, benchmark and compare such energy systems with the help of energy sustainability indicators. We discuss several indicators for their basic suitability and their response to changing boundary conditions, system structures and reference values. The most suitable parameters are applied to four different supply scenarios of a real-world urban energy system. Results: There is a number of energy sustainability indicators, but not all of them are suitable for the use in urban energy system optimization models. Shortcomings originate from the omission of upstream energy supply chains (secondary energy efficiency), from limited capabilities to compare small energy systems (energy productivity), from excessive accounting expense (regeneration rate), from unsuitable accounting methods (primary energy efficiency), from a questionable impact of some indicators on the overall system sustainability (self-sufficiency), from the lack of detailed information content (share of renewables), and more. On the other hand, indicators of absolute greenhouse gas emissions, energy costs, and final energy demand are well suitable for the use in optimization models. However, each of these indicators only represents partial aspects of energy sustainability; the use of only one indicator in the optimization process increases the risk that other important aspects will deteriorate significantly, eventually leading to suboptimal or even unrealistic scenarios in practice. Therefore, multi-criteria approaches should be used to enable a more holistic optimization and planning of sustainable urban energy systems. Conclusion: We recommend multi-criteria optimization approaches using the indicators of absolute greenhouse gas emissions, absolute energy costs, and absolute energy demand. For benchmarking and comparison purposes, specific indicators should be used and therefore related to the final energy demand, respectively the number of inhabitants. Our example scenarios demonstrate modeling strategies to optimize sustainability of urban energy systems.},
  language  = {en}
}
@article{HoernschemeyerSoefkerRienietsNiestenetal.2022,
  author    = {H{\"o}rnschemeyer, Birgitta and S{\"o}fker-Rieniets, Anne and Niesten, Jan and Arendt, Rosalie and Kleckers, Jonas and Klemm, Christian and Stretz, Celestin Julian and Reicher, Christa and Grimsehl-Schmitz, Winona and Wirbals, Daniel and Bach, Vanessa and Finkbeiner, Matthias and Haberkamp, Jens and Budde, Janik and Vennemann, Peter and Walter, Gotthard and Flamme, Sabine and Uhl, Mathias},
  title     = {The ResourcePlan — An Instrument for Resource-Efficient Development of Urban Neighborhoods},
  series = {Sustainability},
  volume    = {14},
  journal   = {Sustainability},
  number    = {3},
  publisher = {MDPI},
  doi       = {10.25974/fhms-14854},
  url       = {http://nbn-resolving.de/urn:nbn:de:hbz:836-opus-148545},
  year      = {2022},
  abstract  = {In Germany, the current sectoral urban planning often leads to inefficient use of resources, partly because municipalities lack integrated planning instruments and argumentation strength toward politics, investors, or citizens. The paper develops the ResourcePlan as (i) legal and (ii) a planning instrument to support the efficient use of resources in urban neighborhoods. The integrative, multi-methodological approach addresses the use of natural resources in the building and infrastructural sectors of (i) water (storm- and wastewater) management, (ii) construction and maintenance of buildings and infrastructure, (iii) urban energy system planning, and (iv) land-use planning. First, the development as legal instrument is carried out, providing (i) premises for integrating resource protection at all legal levels and (ii) options for implementing the ResourcePlan within German municipal structures. Second, the evaluation framework for resource efficiency of the urban neighborhoods is set up for usage as a planning instrument. The framework provides a two-stage process that runs through the phases of setting up and implementing the ResourcePlan. (Eco)system services are evaluated as well as life cycle assessment and economic aspects. As a legal instrument, the ResourcePlan integrates resource protection into municipal planning and decision-making processes. The multi-methodological evaluation framework helps to assess inter-disciplinary resource efficiency, supports the spatial identification of synergies and conflicting goals, and contributes to transparent, resource-optimized planning decisions.},
  language  = {de}
}