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- Energie · Gebäude · Umwelt (EGU) (307) (remove)
Das Spektrum technischer Filter zur Niederschlagswasserbehandlung reicht von kompakten Anlagen im dezentralen Maßstab bis zu zentralen Anlagen mit mehreren Hektar angeschlossener Fläche. Die hier vorgestellten zentralen Systeme werden im Aufstromverfahren durchflossen. Der Zufluss wird dabei durch Sedimentation oder eine Sedimentation-Lamellen-Kombination vorbehandelt. Das Spektrum der eingesetzten Filtersubstrate ermöglicht den Rückhalt feiner Partikel (AFS63) bis hin zu gelösten Stoffen. Die Rückhaltewirkung von technischen Filtern kann sehr hoch sein, allerdings muss der Kompromiss zwischen Wirkung und Wartung gefunden werden. Die Überwachung der Systeme ist durch Bilanzierung der Füllstände vergleichsweise einfach. Erste Ansätze für eine Bemessung der Systeme werden vorgestellt.
Stormwater tree pits with storage elements enable the irrigation of urban trees and can potentially act as decentralized rainwater retention basins. This paper mainly focuses on analyzing this potential. Field tests were conducted to investigate the irrigation behavior and the storage effect of a storm water tree pit system using Perl hoses as irrigation elements over a period of two years.
The rainfall, storage volumes, and soil moisture within the employed planting pit were measured.
With the help of system modeling, the retention ability of the storm water tree pit system was analyzed. The available storage volume was sufficient to irrigate trees for several days. During the measurement period, about 15% of the inflowing rainwater was fed to the root zone of the tree. With practical storage volumes of 200 to 300 m3/ha, a remarkable amount of water from heavy rainfall could be completely stored, thus significantly reducing the risk of flooding. The retention effect and irrigation behavior largely depend on the soil conditions and the technical possibilities of the equipment supplying the root area (in this case, Perl hoses). Further investigations are required to determine the influence on the growth conditions of trees and optimize of the system for discharge into the root zone.
Wind energy plays a major role among renewable
energies. Its expansion is therefore important in order
to achieve the climate targets. Repowering is an
important element in the expansion of wind energy.
On the one hand, it offers a solution for many wind
turbines in Germany that are no longer subsidised due
to their age. On the other hand, modern turbines are
significantly more powerful and enable more efficient
land utilisation. This article provides an overview of
the most important aspects of onshore repowering.
There is a lot to consider when repowering wind turbines.
The legal situation for repowering aims to
be improved through simplified authorisation procedures.
Even though efforts are being made by the
government, there is still room for improvement. The
repowering potential is also dependent on the various
distance regulations to residential buildings in
the federal states. These regulations might also be
improved in the future. Another aspect is the remuneration,
which is now closer to market developments
due to the market premium model. It is also subject
to greater competition as a result of the tendering
process. At the same time, interest rates and turbine
prices have risen, which creates economic challenges
for the operators of future wind farms. Last but not
least, repowering also depends on public acceptance.
This is also to be regulated by law in the future.
As Germany aims to increase its utilization of wind
power, the potential threat to bird populations due
to this expansion is a controversial issue. This paper
aims to collect data on the magnitude of bird strikes
on wind turbines, review existing protective measures
and explore innovative solutions. After a thorough
examination of the literature, it was concluded that
although the impact on bird populations is significant,
it may be overemphasized in popular debates. This
statement is not final as further research is necessary
to assess the impact of bird strikes and explore new
solutions. Comprehensive studies on this specific topic
in Germany are limited, which makes a thorough evaluation
challenging. While there are measures in place
to protect species that may be negatively impacted, it
is possible that these measures will not be adequate
for all of them. While several innovative methods
are under examination, progress in testing and implementation
is slow. Lastly, an information problem
was identified. Since the topic is highly politicized
and polarizing, it is crucial to provide the public with
accessible and reliable information on the discussed
themes. This is currently not the case due to a lack
of data and missing information campaigns.
The upscaling of wind turbines has been increasing in
recent years and will continue to play a significant role
in the future, as it allows for the reduction of electricity
generation costs. Various challenges arise when it
comes to upscaling. This article summarizes the technical
challenges associated with upscaling wind turbines
and presenting their problem-solving approaches
and research trends based on other reviews. It was
found that the most frequently cited challenges are
related to individual components, such as rotor blades,
drive train, generator, tower, and noise impact.
For rotor blades, the challenges are increased flexibility,
more aeroelastic vibrations, increased wear,
interferences with radar and transportation difficulties.
Proposed solutions include the use of carbon-fiber
blades, prebending, novel paints, and for transportation,
segmented rotor blades and on-site manufacturing.
In the gearbox, torque increases, leading to
higher weight and susceptibility to errors. As a result,
the trend is moving towards gearless systems with
permanent magnet synchronous generators. Transportation
is the major issue with towers, which can
be resolved with on-site manufacturing. In terms of
noise emission, reducing aerodynamic noise plays the
most significant role.
This paper outlines the three main areas relevant
to dismantling: the rotor blades, hub and nacelle,
the tower and the foundation. The paper discusses
the dismantling procedures, including the removal of
the top structure, the tower and the foundation, and
evaluates various methods of dismantling the tower,
such as modular dismantling, collapse blasting, folding
blasting, wrecking ball demolition and hydraulic
ram demolition. The assessment of these methods
in practice and the potential challenges and considerations
for future dismantling, particularly as wind
turbine heights increase, are also addressed.
This review paper provides an initial overview of the
state of the art of common corrosion protection methods
for offshore wind turbines. The functions of the
individual corrosion protection methods and their
interaction are explained. In addition, the specific corrosion
protection of different zones and components
of an offshore wind turbine will be discussed. Finally,
some information is given on current and possible
future developments in this subject area.
The pursuit of Offshore Wind Energy (OWE), integral
to the German government’s ambitious renewable
energy goals raises concerns about the environmental
impact of noise emissions on marine life. This paper
delves into the theoretical background of Offshore
Wind Turbine (OWT) noise, exploring its various
phases from the survey to decommission. It examines
the types and causes of noise emissions, their effects
on marine wildlife and potential mitigation measures.
Highlighting the regulatory framework in Germany,
the paper emphasises the need for nuanced approaches
to balance renewable energy objectives with marine
ecosystem preservation.
This article analyses the impact of robotics on the
operation and maintenance (O&M) of offshore wind
turbines (OWTs), with a particular emphasis on the
challenges and benefits. As the world’s reliance on
renewable energy, particularly offshore wind, increases
to reduce climate change, the growing number of
OWTs requires effective O&M. Challenges consist
of logistics, accessibility and high costs. The paper
presents the application of climbing robots, unmanned
aerial vehicles and underwater robots to overcome
these challenges.
The combination of multiple robotic platforms, such
as autonomous surface vehicles and autonomous underwater
vehicles, represents a collaborative approach
to O&M. Obstacles include the need for accurate navigation,
building trust between humans and robots,
and research into artificial intelligence.
In conclusion, the integration of robotics in O&M
presents considerable advantages, increasing efficiency,
safety and cost-effectiveness. Further progress and
research into artificial intelligence are crucial in achieving
complete automation, which will transform the
O&M of OWTs.
The construction and operation of hydropower plants
for energy generation is a major issue in sustainable
energy production. Nevertheless, hydropower plants
have a negative impact on fish populations. It is crucial
to understand the causes and consequences of fish
mortality in hydropower plants in order to find sustainable
solutions that reconcile the need for energy
with the conservation of aquatic ecosystems. This
article examines the fish protection measures that can
be implemented to reduce fish mortality and maintain
ecological balance. Based on the main literature reviewed,
this article mainly refers to Germany in terms
of studies carried out and hydropower plants.
This document presents a comparative analysis of
horizontal and vertical small wind turbines for urban
areas in three power classes up to 10 kW in different
categories. The main objective was to conduct a market
analysis to assess the marketability of these wind
energy systems. The aim was to make it easier for
potential customers to make a decision. However, due
to the limited availability of data, the project encountered
considerable difficulties. As a result, the study
became a comparative assessment, which led to results
that may not be readily transferable to urban environments,
slightly missing the original objective of the
study. The results underline the difficulties associated
with conducting a comprehensive market analysis in
this sector and highlight the need for an independent
series of tests under specific conditions. The paper
concludes with a plea for future research efforts to
adapt data collection methods to urban conditions in
order to improve the relevance and applicability of
such studies in practice.
The annual wastewater flow that is treated by public
wastewater treatment plants in Germany amounts
to approx. 10 ∗ 10^9 m3/a and forms an ”artificial” hydropower
potential that can be used for energy generation
or recovery. In the context of this paper, energy
recovery in the outlet of wastewater treatment plants
is examined using the specific example of the water
wheel at the Warendorf central wastewater treatment
plant. The ”artificial” hydropower potential can be
roughly estimated at up to 20 to 105 GWh/a , whereby
this is largely dependent on the hydraulic gradient.
The strong variance results, among other things, from
the findings of the water wheel operation in Warendorf.
The decisive aspect here is the differential factor,
which describes the deviation between the theoretical
and actual energy yield of the water wheel. The
factor includes maintenance work, downtimes and insufficient
inflows, which are associated with a loss of
output. In the case study, the annual energy recovery
amounts to approx. 2 % of the annual electricity consumption
of the wastewater treatment plant and can
be estimated to 23,500 kWh (2022). In the context
of the economic analysis, it can be seen that despite
the ”low” yield, economic operation is possible if the
system is viewed as a long-term investment - payback
period of the example is approx. 14,5 years. The
27-year operation (1996 - 2023) of the water wheel
at the Warendorf central wastewater treatment plant
confirms this and important findings on successful
practical operation can be shown in the context of
this paper.
The preservation of water bodies continuity is fundamental
for aquatic communities, particularly for fish
populations. Various structures impede watercourse
continuity, impacting fish migration and habitat distribution.
Conventional fish passages often fall short
in diverse scenarios, prompting the development of
specialized solutions. This article proposes a criteria
catalog for these special fish passage solutions based
on DWA leaflet DWA-A 509. It discusses the need
for these solutions, presents a selection of specialized
options, and outlines criteria from DWA-M 509, construction
guidelines, and economic perspectives. It
scrutinizes criteria ranging from target fish species to
cost considerations. Three examples, including the
Runserau fish lift, the bristle ramp fish lock, and the
Fishcon sluice, illustrate these specialized solutions,
their functionalities, advantages, and drawbacks. Additionally,
the article compiles criteria from industry
standards and guidelines into a comprehensive evaluation
catalog. The criteria, when applied, assist in the
selection of suitable fish passage solutions based on
specific site conditions and fish species requirements.
This holistic approach aims to optimize fishway selection,
fostering the ecological sustainability of watercourses.
However, this catalog remains dynamic
and open to expansion with evolving research and
practical application, urging further exploration and
validation of these criteria through diverse case studies
and technological advancements in the field.
Wind turbine structures take a major role in the
modern conversion to renewable energy sources and
contribute to the creation of a greener world. In recent
years, the development and installation of wind
turbines have seen rapid growth. However, with the
increasing capacity and size of wind farms worldwide,
there are growing concerns about the safety and reliability
of these installations. Therefore, structural
health monitoring and the detection of damage to
wind turbines have gained considerable importance in
research. Wind turbine blades are particularly susceptible
to various types of damage due to environmental
influences. This article provides an overview of signal
responses, sensors used and non-destructive testing
techniques in the field of damage detection on wind
turbine blades. The intention of the article is to give
an insight into the possibilities of structural health
monitoring and at the same time to point out unsolved
problems in this field.
This article discusses the use of artificial intelligence
in the wind energy industry, particularly in addressing
challenges and optimizing the expansion of renewable
energies in Germany. It highlights the application
of artificial intelligence in wind forecasts and yield
predictions, bird detection, wind turbine and farm
design, condition monitoring, and predictive maintenance.
Additionally, it introduces the “WindGISKI”
research project, which aims to use artificial intelligence
to identify new areas for wind turbines. The
project utilizes a neural network to analyze and predict
flight routes, potentially reducing bird mortality.
The document also emphasizes the potential broader
applications of “WindGISKI” in other fields of activity,
such as land use planning and city development.
Overall, it underscores the significant role of artificial
intelligence in addressing challenges in wind energy
and outlines the potential for artificial intelligence
to drive the expansion of renewable energies while
addressing key obstacles.
Meanwhile, renewable energy sources such as hydropower, solar and wind energy and biomass are increasingly being used to reduce dependence on fossil fuels and thus counteract the ongoing global warming. However, these are also associated with environmental impacts. To that effect, this article takes a closer look at tidal power plants, which are classified as hydroelectric power plants, by conducting a systematic literature review. The results show that the strength and form of the environmental impact depends on the specific location and type of plant. Tidal power plants have an impact on the habitats of marine animals and thus influence their behavior and population. In addition, the operation of tidal power plants changes the sediment distribution, causes a reduction in current velocities and a change in current direction in the surrounding area and leads to a change in wave height. The construction of the power plants is associated with noise, which primarily causes changes in the behavior of some species. Furthermore, the electromagnetic fields generated can also affect marine life. In order to assess the environmental impact of tidal power plants in comparison to other renewable energies, further studies should focus on the environmental impact of the different technologies in relation to the energy yield.
This study identifies supply options for sustainable urban energy systems, which are robust to external system changes. A multi-criteria optimization model is used to minimize greenhouse gas (GHG) emissions and financial costs of a reference system. Sensitivity analyses examine the impact of changing boundary conditions related to GHG emissions, energy prices, energy demands, and population density. Options that align with both financial and emission reduction and are robust to system changes are called “no-regret” options. Options sensitive to system changes are labeled as “potential-risk” options.
There is a conflict between minimizing GHG emissions and financial costs. In the reference case, the emission-optimized scenario enables a reduction of GHG emissions (-93%), but involves higher costs (+160%) compared to the financially-optimized scenario.
No-regret options include photovoltaic systems, decentralized heat pumps, thermal storages, electricity exchange between sub-systems and with higher-level systems, and reducing energy demands through building insulation, behavioral changes, or the decrease of living space per inhabitant. Potential-risk options include solar thermal systems, natural gas technologies, high-capacity battery storages, and hydrogen for building energy supply.
When energy prices rise, financially-optimized systems approach the least-emission system design. The maximum profitability of natural gas technologies was already reached before the 2022 European energy crisis.
This review paper presents a short overview of current power system modelling tools especially used for analysing energy and electricity systems for the supply and demand sector. The main focus of this review lies on open source tools and models which are written and used in the programming language “Python”. The modelling tools are represented in a comprehensive table with key information. Five modelling tools with an open source license can be filtered out. The modelling tool PyPSA can be considered as a high performing tool especially as the gap between power system analysis tool (PSAT) and energy system modelling tool.
This review is about where and which tidal power systems are currently deployed. It starts with an insight into the variety of different tidal power systems. With the help of a list from the European Marine Energy Center about currently used systems for tidal power plants, it quickly becomes apparent that two systems stand out. These are the vertical and horizontal turbines. The latter are particularly common, as they are used for both tidal stream and tidal range power plants. Determining the regions with high potential for tidal power is not always easy due to the many influencing factors. Influencing factors are, for example form and conditions of the seabed, topographical features of the coast or currents in the sea [1]. Therefore, each region must be considered separately. n this paper the focus is on the UK, the literature shows that the coastal regions around the UK provide about 50 TWh/year of the European tidal power potential. This is due to the location between the oceans and the geological conditions, which act as a channel for the tides. The two areas with high potential where planning
and construction of tidal power plants is currently underway are in the north of Scotland and in the southwest of England in the Bristol Channel.
The use of wind power is rapidly expanding worldwide. It is important to examine the impact of wind turbines on the environment to see if they provide a net benefit and to identify potential for improving. Therefore life cycle assessments (LCA) of different wind turbine types are compared in this short review. The results are then shown side by side in tables for comparison. Overall the LCAs show that wind turbines compensate the required energy and emitted pollutants after approx. 6-16 months. The energy payback period (EPP) for 2 MW onshore wind turbines remained roughly the same since 2009 with approximately 7 months. Onshore wind turbines have a higher impact due to emissions but a shorter EPP than offshore wind turbines. The estimated service life of 20 years should be maximized to ensure a high energy yield ratio. The biggest impact on the environment results from the processes to provide the building material e.g. steel and cement. That impact could be reduced by 20 % if recycled steel would be used. It is shown that wind power is one of the cleanest energy sources. But further investigations in material processing and recycling are important to improve the eco-balance of wind turbines.
For the increasingly important storage of renewably generated electricity, this review explains the construction of a surface and underground pumped storage
power plant. The problems for the construction of an underground pumped storage power plant are further listed. These are geological, environmental and
economic problems as well as a low acceptance by the population. The geological problems are concerns about leaching of minerals and heavy metals as well as the statics of the cavities. Mining companies in Germany are obligated to renaturalize the landscape areas again, which could be realised by a lake. Furthermore, care must be taken to ensure that the mine water does not come into contact with the groundwater. According to a survey by RISP on the subsequent use of the mine areas for an underground pumped
storage power plant, the acceptance of the population is over 70 percent. The economic consideration concludes that the arbitrage profit for a difference between off-peak and peak of 10 €/MWh is about 2.7 M€/a and for 100 €/MWh about 27.3 M€/a. With investment costs of about 630 M€, despite the assumption of 100 €/MWh, more than 20 years are needed for an underground pumped storage power plant to be amortized. The acceptance could be increased by creating a lake as a recreation area as well as being used as an upper storage reservoir. Thus, the cost of renaturation decrease when combined with the creation of the storage basin. The problem of ground conditions can be solved by creating new cavities by means of tunnel boring at an inclination. For static safety as well as against leaching of minerals and heavy metals, the cavity walls can be sealed with reinforced concrete. The technology of underground pumped storage power plants can be used for better utilisation of renewable energies. This is especially in flat and densely populated regions a possibility to store energy, because the main part of the power plant is underground.
The Spreadsheet Energy System Model Generator (SESMG) is a tool for modeling and optimizing energy systems with a focus on urban systems. The SESMG is easily accessible as it comes with a browser-based graphical user interface, spreadsheets to provide data entry, and detailed documentation on how to use it. Programming skills are not required for the installation or application of the tool. The SESMG includes advanced modeling features such as the application of the multi-energy system (MES) approach, multi-objective optimization, model-based methods for reducing computational requirements, and automated conceptualization and result processing of urban energy systems with high spatial resolution. Due to its accessibility and the applied modeling methods, urban energy systems can be modeled and optimized with comparatively low effort.
Baumrigolen und (Stadt-)Bäume zeichnen sich durch eine multifunktionale Wirkung aus. Bäume prägen das Stadtbild, spenden Schatten und kühlen durch Verdunstung. Der Rigolenkörper speichert Wasser, dass unmittelbar in den Untergrund eingetragen und teilweise auch zur Baumbewässerung verfügbar ist. Darüber hinaus kann die Rigole einen Beitrag zur Überflutungsvorsorge leisten.
The Influence of Pressure-Swing Conditioning Pre-Treatment of Cattle Manure on Methane Production
(2020)
Due to a limited number of available measurements on agricultural biogas plants, established process models, such as the Anaerobic Digestion Model No. 1 (ADM1), are rarely applied in practise. To provide a reliable basis for model-based monitoring and control, different model simplifications of the ADM1 were implemented for process simulation of semi-continuous anaerobic digestion experiments using agricultural substrates (maize silage, sugar beet silage, rye grain and cattle manure) and industrial residues (grain stillage). Individual model structures enable a close depiction of biogas production rates and characteristic intermediates (ammonium nitrogen, propionic and acetic acid) with equal accuracy as the original ADM1. The impact of different objective functions and standard parameter values on parameter estimates of first-order hydrolysis constants and microbial growth rates were evaluated. Due to the small number of required model parameters and suitable system characteristics, simplified model structures show clear advantages for practical application on agricultural biogas plants.
Rigorous process models provide a reliable basis for model-based monitoring and control of anaerobic digestion plants. Due to the complex model structure and non-linear system characteristics, the established Anaerobic Digestion Model No. 1 (ADM1) is rarely applied in industrial plant operation. The present investigation proposes a systematic procedure for successive model simplification and presents the description of five model variants of a mass-based ADM1. Individual model structures greatly differ in their number of implemented process phases, characteristic components and required parameters. Simplified model variants combine nutrient degradation and biogas formation based on first-order sum reactions, whereas complex model structures describe individual degradation pathways and intermediates during acido- and acetogenesis. Characteristic features of the derived model structures as well as the stoichiometric methane potentials and microbial biomass yields of the underlying degradation pathways of individual model variations are evaluated and discussed in detail.
Different model structures were compared to simulate the characteristic process variables of the anaerobic digestion of maize, sugar beet and grain silage. Depending on the type and number of the required components, it can be shown that in comparison to the complex Anaerobic Digestion Model No. 1 (ADM1) different simplified model structures can describe the gas production rate, ammonia nitrogen and acetate concentration or pH value equally well. Since the reduction of the predominantly fast kinetics of the methanogenesis, acetogenesis or acidogenesis will only have little effect on the simulation of the specific gas production, it can be proven that the hydrolysis is the rate-limiting step during the uninhibited anaerobic digestion of complex particulate substrates. However, the stoichiometric comparison reveals that the model protein gelatine is not suitable for a representative characterization of agricultural energy crops.
Different methods for optimization the anaerobic digestion (AD) of sugarcane filter cake (FC) with a special focus on volatile fatty acids (VFA) production were studied. Sodium hydroxide (NaOH) pretreatment at different concentrations was investigated in batch experiments and the cumulative methane yields fitted to a dual-pool two-step model to provide an initial assessment on AD. The effects of nitrogen supplementation in form of urea and NaOH pretreatment for improved VFA production were evaluated in a semi-continuously operated reactor as well. The results indicated that higher NaOH concentrations during pretreatment accelerated the AD process and increased methane production in batch experiments. Nitrogen supplementation resulted in a VFA loss due to methane formation by buffering the pH value at nearly neutral conditions (∼6.7). However, the alkaline pretreatment with 6 g NaOH/100 g FCFM improved both the COD solubilization and the VFA yield by 37%, mainly consisted by n-butyric and acetic acids.
Inter-laboratory reproducibility of biomethane potential (BMP) is dismal, with differences in BMP values for the same sample exceeding a factor of two in some cases. A large group of BMP researchers directly addressed this problem during a workshop held in Leysin, Switzerland, in June 2015. The workshop resulted in a new set of guidelines for BMP tests published in 2016, which is the subject of the present commentary. The work has continued with two international inter-laboratory studies and one additional workshop held in Freising, Germany, in 2018. The dataset generated by the two inter-laboratory studies were used to refine the validation criteria for BMP tests. Based on these new results an update to the original guidelines is proposed here.
Flexible biogas production can enable demand-oriented energy supply without the need for expensive gas storage expansions, but poses challenges to the stability of the anaerobic digestion (AD) process. In this work, biogas production of laboratory-scale AD of maize silage and sugar beets was optimized to cover the residual load of an electricity self-sufficient community using a simple process model based on first-order kinetics. Experiments show a good agreement between biogas demand, predicted, and measured biogas production. By optimizing biogas conversion schedules based on the measured gas production, a gas storage capacity of 7-8 h was identified for maximum flexibility, which corresponds to typical gas storage sizes at industrial biogas plants in Germany. Various stability indicators were continuously monitored and proved resilient process conditions. These results demonstrate that demand-oriented biogas production using model predictive control is a promising approach to enable existing biogas plants to provide balancing energy.
Local and regional energy systems are becoming increasingly entangled. Therefore, models for optimizing these energy systems are becoming more and more complex and the required computing resources (run-time and random access memory usage) are increasing rapidly. The computational requirements can basically be reduced solver-based (mathematical optimization of the solving process) or model-based (simplification of the real-world problem in the model). This paper deals with identifying how the required computational requirements for solving optimization models of multi-energy systems with high spatial resolution change with increasing model complexity and which model-based approaches enable to reduce the requirements with the lowest possible model deviations. A total of 12 temporal model reductions (reduction of the number of modeled time steps), nine techno-spatial model reductions (reduction of possible solutions), and five combined reduction schemes were theoretically analyzed and practically applied to a test case. The improvement in reducing the usage of computational resources and the impact on the quality of the results were quantified by comparing the results with a non-simplified reference case. The results show, that the run-time to solve a model increases quadratically and memory usage increases linearly with increasing model complexity. The application of various model adaption methods have enabled a reduction of the run-time by over 99% and the memory usage by up to 88%. At the same time, however, some of the methods led to significant deviations of the model results. Other methods require a profound prior knowledge and understanding of the investigated energy systems to be applied. In order to reduce the run-time and memory requirements for investment optimization, while maintaining good quality results, we recommend the application of (1) a pre-model that is used to (1a) perform technological pre-selection and (1b) define reasonable technological boundaries, (2) spatial sub-modeling along network nodes, and 3) temporal simplification by only modeling every nth day (temporal slicing), where at least 20% of the original time steps are modeled. Further simplifications such as spatial clustering or larger temporal simplification can further reduce the computational effort, but also result in significant model deviations.
Heating networks are highly relevant for the achievement of climate protection goals of urban energy systems. This is due to their high renewable energy potential combined with high plant efficiency and utilization rates. For the optimal integration and sector coupling of heating networks in holistic urban energy systems, open source energy system modeling tools are highly recommended. In this contribution, two open source approaches (the "Spreadsheet Energy System Model Generator"-integrated DHNx-Python module (DHNx/SESMG) and Thermos) are theoretically compared, and practically applied to a real-world energy system. Deviations within the results can be explained by incorrectly pre-defined parameters within Thermos and cannot be adjusted by the modeler. The simultaneity is underestimated in the case study by Thermos by more than 20%. This results in undersized heating plant capacities and a 50% higher number of buildings connected to the network. However, Thermos offers a higher end-user usability and over 100 times faster solving. DHNx/SESMG, in contrast, offers the possibility to adjust more model parameters individually and consider multiple energy sectors. This enables a holistic modeling of urban energy systems and the model-based optimization of multi-sectoral synergies.
Abfiltrierbare Stoffe (AFS) werden als Indikatorparameter für die Verunreinigung von Oberflächenabflüssen und zur Wirksamkeitsbetrachtung von Regenwasserbehandlungsanlagen verwendet. Das Arbeitsblatt DWA-A 102 (DWA/BWK, 2020) empfiehlt den Feinanteil der Abfiltrierbaren Stoffe (AFS63) zur Bewertung der Verunreinigung von Niederschlagswasser und der durch Einleitung hervorgerufene Gewässerbelastung. Als AFS werden sämtliche Sink-, Schweb- und Schwimmstoffe bezeichnet, die ein Filter mit einer Porengröße von 0,45 µm zurückhält. Der Feinanteil AFS63 fasst die Abfiltrierbaren Stoffe der Größenordnung 0,45 µm bis 63 µm zusammen. Die Einflussgrößen und Bedingungen bei der Bestimmung des Parameters AFS63 sind jedoch komplex. Das beginnt bei der Entnahme einer repräsentativen Probe und setzt sich bis zur Bestimmung des Parameters fort. Während die Bestimmung der AFS in Normen geregelt ist, wird die verbindliche Bestimmung von AFS63 derzeit diskutiert. Vor dem Hintergrund, dass mit dem Parameter AFS63 die Wirksamkeit von Behandlungsanlagen nachgewiesen wird, ist eine korrekte Ermittlung zur Bilanzierung der Verunreinigung von Zu- und Abflüssen von besonderer Bedeutung. Als sinnvolle Ergänzung zur bisherigen Bestimmungsmethode hat sich eine vergleichsweise einfache und repräsentative Bestimmung mit einem Partikelzähler herausgestellt.
(1) The use of renewable energy for power and heat supply is one of the strategies to reduce greenhouse gas emissions. As only 14% of German households are supplied with renewable energy, a shift is necessary. This shift should be realized with the lowest possible environmental impact. This paper assesses the environmental impacts of changes in energy generation and distribution, by integrating the life cycle assessment (LCA) method into energy system models (ESM). (2) The integrated LCA is applied to a case study of the German neighborhood of Herne, (i) to optimize the energy supply, considering different technologies, and (ii) to determine the environmental impacts of the base case (status quo), a cost-optimized scenario, and a CO2-optimized scenario. (3) The use of gas boilers in the base case is substituted with CHPs, surface water heat pumps and PV-systems in the CO2-optimized scenario, and five ground-coupled heat pumps and PV-systems for the cost-optimized scenario. This technology shift led to a reduction in greenhouse gas emissions of almost 40% in the cost-optimized, and more than 50% in the CO2-optimized, scenario. However, technology shifts, e.g., due to oversized battery storage, risk higher impacts in other categories, such as terrestrial eco toxicity, by around 22%. Thus, it can be recommended to use smaller battery storage systems. (4) By combining ESM and LCA, additional environmental impacts beyond GHG emissions can be quantified, and therefore trade-offs between environmental impacts can be identified. Furthermore, only applying ESM leads to an underestimation of greenhouse gas emissions of around 10%. However, combining ESM and LCA required significant effort and is not yet possible using an integrated software.
The development of compact treatment devices with high removal efficiencies and low space requirements is a key objective of urban stormwater
treatment. Thus, many devices utilize a combination of sedimentation and upward flow filtration in a single system. This study, for the
first time, evaluates the flow field inside a combined filter-lamella separator via computational fluid dynamics. Herein, three objectives
are investigated: (i) the flow field for different structural configurations, (ii) the distribution of particulate matter along the filter bed and
(iii) the dynamic clogging in discrete filter zones, which is addressed by a clogging model derived from literature data. The results indicate
that a direct combination of a filtration stage with a lamella separator promotes a uniform flow distribution. The distribution of particulate
matter along the filter bed varies with configuration and particle size. Clogging, induced by particles in the spectrum ,63 μm, creates
gradients of hydraulic conductivity along the filter bed. After treating about half of Germany’s annual runoff-efficient precipitation at a rainfall
intensity of 5 L/(s·ha), the filtration rates increase in the front of the filter bed by þ10%. Thus, long-term operating behavior is sensitive to
efficient filter utilization in compact treatment devices.
Techno-Economic Assessment of Solid-Liquid Biogas Treatment Plants for the Agro-Industrial Sector
(2022)
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.
Indicators for the optimization of sustainable urban energy systems based on energy system modeling
(2022)
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.
Die Ursachen und Merkmale einer Überflutung durch urbane Sturzfluten und einer Überschwemmung aufgrund eines Flusshochwassers sind unterschiedlich. Die Folgen einer urbanen Sturzflut beschränken sich zumeist auf Sachschäden. Bei einem ausgeprägten Hochwasser, wie beispielsweise im Sommer 2021, stehen neben verheerenden Schäden an Gebäuden und Infrastruktur vor allem die Gefahr von Leib und Leben im Mittelpunkt. Die Möglichkeiten der Risikokommunikation hängen maßgeblich von der Art der Ereignisse ab. Grundsätzlich kann zwischen der grundlegenden und dauerhaften Kommunikation (Bürgerinformation) und der Risikokommunikation in akuten Fällen durch Warnhinweise unterschieden werden.
Zunehmend gewinnen naturnahe Systemlösungen zur Entwässerung urbaner Räume an Bedeutung. Ziel künftiger wasserwirtschaftlicher Konzepte ist die ortsnahe Rückhaltung mit unmittelbarer Versickerung und Verdunstung des Regenwassers, statt der raschen Ableitung und Einleitung in ein naheliegendes Oberflächengewässer. Baumrigolen sind ein wesentliches Element dieser Form der Regenwasserbewirtschaftung im Kontext einer wasserbewussten Stadtentwicklung. In diesem Beitrag werden Systembeispiele und wasserwirtschaftliche Aspekte von Baumrigolen beschrieben und aktuelle Forschungs- und Entwicklungsvorhaben zur Untersuchung der multifunktionalen Wirkung von Baumrigolen vorgestellt. Zur Multifunktionalität zählen die Überflutungsvorsorge durch ortsnahe Retention und die Nutzung des Regenwassers zur Bewässerung von Stadt- und Straßenbäumen. Abschließend erfolgt eine Zusammenstellung zahlreicher Ökosystemleistungen der Systeme im urbanen Raum.