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The structural transformation and dynamical heterogeneity in Germania (GeO2) are investigated via molecular dynamics (MD) simulation. The MD model with 5499 atoms was constructed under pressure up to 150 GPa and at a temperature of 3500 K. The structural transformation mechanism has been studied by observing domain structures and boundary oxygen atoms. The simulation result reveals that GeO2 consists of separate domains and boundaries in its melt structure. Under compression, the structure of GeO2 changes gradually and represents many types of structures. The melt structure exhibits many structural domains Dx, and polymorphism appears at pressures of 12 and 20 GPa. The change of tetrahedral structure to octahedral structure in germanium coordination occurred in parallel with the process of merging and splitting of domain structure. Moreover, the existence of high- and low-density phases in GeO2 melt is indicated. The high-density phase is D6 domain and boundary oxygen while the low-density phase is D4 and D5 domain. The compression mechanism in GeO2 melt mainly is a reduction of average Voronoi volume of oxygen and Voronoi volume of D6, boundary atoms oxygen. Furthermore, we find the dynamical heterogeneity at ambient pressure. The separate "fast" regions and "slow" regions in GeO2 are detected via link-cluster function. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effect of demand response (DR) on power and energy flexibilities with three types of district heated buildings (apartment building, cultural center, and office building) in Finland and Germany. A rule-based control algorithm was applied for the DR control with two country-specific dynamic district heating (DH) prices, the more fluctuating Finnish synthetic DH price and the flatter German synthetic DH price. This research was implemented with the validated dynamic building simulation tool IDA ICE. Set-point smoothing of the indoor air temperature was applied to minimize the rebound effect. Nighttime set-back was adopted in the cultural center and the office building. The results show that the DR control without smoothing creates additional peaks in power demand, while the set-point smoothing significantly decreases the peak power demand. The DR control can significantly shape the heating power demand of the buildings and increase energy flexibility. The range of the resultant seasonal energy flexibility factors is from 3 to 26% for charging and from −6 to −31% for discharging, depending on the building types and countries. Cases with nighttime set-back have higher power and energy flexibilities, while this causes additional peaks, which is detrimental to DH systems. [ABSTRACT FROM AUTHOR]

Research activities with regard to membrane construction at HFT Stuttgart In the presented article we give an overview to some of the recent and ongoing research projects at Hochschule für Technik Stuttgart (HFT) in the context of membrane buildings. One of the major challenges in the context of membrane building is the regulation of the radiative heat flux entering the building as well as thermal losses across the building envelope while still providing comfortable room temperature and daylight use for the inhabitants. The accomplishment of this task, investigated by means of measurements and numerical simulation was the scope of several research projects at HFT Stuttgart. Within the research project "SoFt" the compatibility of insulation and translucency was investigated and realized within the roof construction of a sports center in Germany. One of the objects of the research project "FMESG" was the realization and numerical simulation of an angle‐selective static solution for partial shading, analogous to a miniature saw tooth roof configuration, up to the point of a working prototype. The project "Follow‐e2" tackled the influence of low emissivity surface coatings on the energy balance of membrane constructions by means of numerical simulation. Within the project "FLEX‐G" the potential for reduction of energy demand by dynamic shading with electrochromic elements was investigated by means of dynamic building simulation and heuristic optimization. [ABSTRACT FROM AUTHOR]

The increased impact from fluctuating energy sources like wind and photovoltaics significantly affects the operational regime of conventional power plants. In the near future, even former base load power plants such as the large-scale lignite plants in Germany will need to start and shut down to balance the electricity system. As frequent starts were not in the focus of optimisation in the past, an extensive potential can be expected to reduce start-up costs and environmental impacts. In order to investigate such optimisation potentials, a comprehensive dynamic simulation model has been developed including process components such as boiler and water-steam cycle but also the power plants control system along with start-up sequence control. After successfully reproducing a reference start of the power plant, the model has been used to identify restrictions for faster start-ups, less fuel consumption and less emission while keeping the thermal and mechanical stress, caused by higher ramp rates, within acceptable bounds. [ABSTRACT FROM AUTHOR]

This paper describes a method to decrease the additional measurement effort during a model calibration/verification to create reliable models for plant optimisation. The method is based on the deterministic processes creating the dry weather inflow to municipal treatment plants, which can be described by a simple influent composition model. This method was applied to two wastewater treatment plants of Lippeverband and the usability is indicated by the good correlation between routine online effluent measurements and simulation results. This paper presents one of these applications, the case study WWTP Dorsten. The resulting model is used to analyse the current plant performance, to analyse bottlenecks and to develop future improvements of operation and control of this plant. A selection of control options is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: To evaluate the environmental impact of massive heat-pump introduction on greenhouse gas (GHG) emissions in different electricity-generation systems, dynamic simulations have been carried out for four European countries, namely, Belgium, France, Germany and the Netherlands. For this purpose, the simulations are performed with Promix, a tool that models the overall electricity-generation system. Three heating devices are considered for each country, namely classic fossil-fuel heating, heat pumps and electric resistance heating. Both direct heat-pump heating with a coefficient of performance (COP) of 2.5 and accumulation heat-pump heating with a COP of 5 are investigated. The introduction of electric heating in an electricity-generation system increases the demand for electricity and generates a shift of emissions from fossil-fuel heating systems to electrical plants. The results of the simulations reveal that the massive introduction of either heat pump or resistance heating is always favourable to the environment in France. The most environmentally friendly scenario in 2010 is projected to reduce GHG emissions by about 3.8Mton compared to the reference scenario. In Belgium and Germany, the largest reduction in GHG emissions occurs with accumulation heat pumps. Belgium can save up to 220kton of GHG emissions, while Germany can attain reductions of 800kton in 2010. In the Netherlands, a significant reduction can be achieved by considering the addition of gas-fired combined cycle (CC) power plants, together with the introduction of electric heating, resulting in emissions savings of 410kton. [Copyright &y& Elsevier]

The selector activated sludge (SAS) systems are known to prevent excessive growth of filamentous microorganisms responsible for bulking sludge, but these systems were hardly ever modelled. This study aimed to develop a model capable of predicting rapid substrate removal in the SAS systems. For this purpose, the Activated Sludge Model No. 3 (ASM3) was extended with three processes (adsorption, direct growth on the adsorbed substrate under aerobic or anosic conditions). The modified ASM3 was tested against the results of batch experiments with the biomass originating from two full-scale SAS systems in Germany. The endogenous biomass was mixed with various readily biodegradable substrates (acetate, peptone, glucose and wastewater) and the utilisation of substrate (expresses as COD) and oxygen uptake rates (OURs) were measured during the experiments. In general, model predictions fitted to the experimental data, but a considerable number of kinetic (5) and stoichiometric (2) parameters needed to be adjusted during model calibration. The simulation results revealed that storage was generally a dominating process compared to direct growth in terms of the adsorbed substrate utilisation. The contribution of storage ranged from 65-71% (Plant A) and 69-92% (Plant B). [ABSTRACT FROM AUTHOR]

In the end of the year 1999 a new concept for Hamburg's wastewater treatment plants was commissioned to cope with the additional load of 250,000 PE which has been connected to the existing plant serving 1.85 million population equivalents. The new concept consists of an additional tank for the storage of sludge liquor to avoid peak nitrogen concentrations in the effluent of the plant. This solution has been developed within a study assessing a wide range of concepts with costs between initial €100 million and the final construction costs of €1 million. Here the dynamic simulation showed to be a very efficient planning tool. Within the first three years of operation the chosen solution showed to be able to fulfil the requirements. In 2002 the concept has been improved by a few more measures, mainly the equipment of one of the storage tanks as a SAT tank for further cost effective nitrogen removal. For a further improvement of the treatment capacity additional measures are planned to be carried out within the next years. [ABSTRACT FROM AUTHOR]

Work on aggregation of district heating networks has been in progress during the last decade. Two methods have independently been developed in Denmark and Germany. In this article, a comparison of the two methods is first presented. Next, the district heating system Ishoej near Copenhagen is used as a test case.For the 23 substations in Ishoej, heat loads and primary and secondary supply and return temperatures were available every 5 min for the period December 19–24, 2000.The accuracy of the aggregation models has been documented as the errors in heat production and in return temperature at the DH plant between the physical network and the aggregated model. Both the Danish and the German aggregation methods work well.It is concluded that the number of pipes can be reduced from 44 to three when using the Danish method of aggregation without significantly increasing the error in heat production or return temperature at the plant. In the case of the German method, the number of pipes should not be reduced much below 10 in the Ishoej case. [Copyright &y& Elsevier]

The assessment of regional bioenergy potentials from different types of natural land cover is an integral part of simulation tools that aim to assess local renewable energy systems. This work introduces a new workflow, which evaluates regional bioenergy potentials and its impact on water demand based on geographical information system (GIS)-based land use data, satellite maps on local crop types and soil types, and conversion factors from biomass to bioenergy. The actual annual biomass yield of crops is assessed through an automated process considering the factors of local climate, crop type, soil, and irrigation. The crop biomass yields are validated with historic statistical data, with deviation less than 7% in most cases. Additionally, the resulting bioenergy potentials yield between 10.7 and 12.0 GWh/ha compared with 13.3 GWh/ha from other studies. The potential contribution from bioenergy on the energy demand were investigated in the two case studies, representing the agricultural-dominant rural area in North Germany and suburban region in South Germany: Simulation of the future bioenergy potential for 2050 shows only smaller effects from climate change (less than 4%) and irrigation (below 3%), but the potential to cover up to 21% of the transport fuels demand in scenario supporting biodiesel and bioethanol for transportation. [ABSTRACT FROM AUTHOR]

Biomass combined heat and power plants (CHPPs) can operate target-specifically because of their controllability while supporting decarbonization in district heating. The transition from the German Renewable Energies Act funding, which has promoted biomass CHPPs but is now about to expire, to direct marketing, is a major economic challenge for many biomass-heating grids. To successfully accomplish it, the flexible operation of biomass CHPPs, compared to the previous baseline-operation, is becoming an increasingly important requirement if participation in the electricity markets is to remain profitable. This paper presents a techno-economic assessment of flexible CHPP operation in a modeled district heating system with a CHPP, a peak load boiler and a thermal heat storage. The simulation model compares two cases - a natural gas and a wood-chip gasifier CHPP. The analysis of the results investigates the parameters that need to be adapted to make biomass-fired CHPP heating grids more efficient compared to fossil-fired CHPP heating grids in a flexible operating scenario. It highlights the technical and economic superiority of a fossil-fired CHPP in flexible operation in comparison to the wood gasifier system. The introduction of a CO 2 -tax on natural gas as a fuel, currently under discussion in Germany, would increase the competitiveness of the wood gasifier. • Simulation model of a district heating system. • Model units are wood or natural CHP plant, peakload boiler and heat storage. • Three scenarios for CHP plant dispatch under consideration of electricity prices. • Focus on dynamic differences of the CHP plant operation strategy. • Results show limitations in operational flexibility of the wood gas CHP plant. [ABSTRACT FROM AUTHOR]

• Autumn-sown sugar beet may intercept more PAR due to a faster canopy closure in spring. • Based on a 3 year field trial, a crop growth simulation model for autumn-sown beets has been developed. • It considers specific aspects like leaf losses due to frost, vernalisation and bolting. • The model was able to satisfactorily estimate total and root dry matter. • A 12 year simulation revealed that autumn-sown sugar beet achieved a 29% higher total DM than spring-sown ones. Autumn-sown sugar beets may achieve a faster canopy closure in spring compared to spring-sown sugar beets, thus increasing radiation interception and yield. However, to date yield benefits of autumn-sown beets cannot be quantified, as they start to bolt in spring. Therefore, simulation models for winter beet need to be developed. From 2009 to 2012, field trials in northern Germany were carried out with sugar beets sown in spring (conventional sugar beet) as well as sown in autumn (bolting winter beet). Based on these data, a dynamic simulation model was developed and calibrated for winter beets. The model is based on light use efficiency (LUE) approach and considered winter beet-specific aspects like leaf (area) losses due to frost, vernalisation and bolting. For conventional sugar beets, the validation revealed a RMSE of 164 g m-2 and a model efficiency (EF) of 0.93 for root dry matter. For the total dry matter (DM tot) of bolting winter beets, the validation showed a RMSE of 216 g m-2 and an EF of 0.69. Implemented assumptions regarding the non-bolting winter beets allow the model to simulate this beet type as well. A simulation over 12 years (1998-2010) for the site Hohenschulen estimated 1921 g DM tot m-2, 971 g DM tot m-2 and 2474 g DM tot m-2 for conventional sugar beets, bolting winter beets and non-bolting winter beets, respectively. Our results suggest that developing non-bolting winter beets seems be a promising approach to increase beet yields. [ABSTRACT FROM AUTHOR]

This paper shows how the dynamic simulation of municipal wastewater treatment plants can be used for assessing the performance of a plantunder different legal requirements. In this study, the situation is described, when it was uncertain, how the requirements of the German law (ARAN 199 1) would be adapted to the requirements given by the EC-directive concerning urban wastewater treatment (EC directive, 1991). The requirements of these two are compared to each other. A simulation study is described, in which the future results of a plant to be extended am calculated for the period of one year. It is shown that, concerning the effluent concentrations of ammonia and total nitrogen,this plant will be able to meet both laws. (c) 1998 IAWQ. Published by Elsevier Science Ltd [ABSTRACT FROM AUTHOR]