49 research outputs found
Demand-Orientated Power Production from Biogas: Modeling and Simulations under Swedish Conditions
The total share of intermittent renewable electricity is increasing, intensifying the need for power balancing in future electricity systems. Demand-orientated combined heat and power (CHP) production from biogas has potential for this purpose. An agricultural biogas plant, using cattle manure and sugar beet for biogas and CHP production, was analyzed here. The model Dynamic Biogas plant Model (DyBiM) was developed and connected to the Anaerobic Digestion Model No. 1 (ADM1). Flexible scenarios were simulated and compared against a reference scenario with continuous production, to evaluate the technical requirements and economic implications of demand-orientated production. The study was set in Swedish conditions regarding electricity and heat price, and the flexibility approaches assessed were increased CHP and gas storage capacity and feeding management. The results showed that larger gas storage capacity was needed for demand-orientated CHP production but that feeding management reduced the storage requirement because of fast biogas production response to feeding. Income from electricity increased by 10%, applying simple electricity production strategies to a doubled CHP capacity. However, as a result of the currently low Swedish diurnal electricity price variation and lack of subsidies for demand-orientated electricity production, the increase in income was too low to cover the investment costs. Nevertheless, DyBiM proved to be a useful modeling tool for assessing the economic outcome of different flexibility scenarios for demand-orientated CHP production
Modelling of two-stage anaerobic digestion using the IWA Anaerobic Digestion Model No. 1 (ADM1)
The aim of the study presented was to implement a process model to simulate the dynamic behaviour of a pilot-scale process for anaerobic two-stage digestion of sewage sludge. The model implemented was initiated to support experimental investigations of the anaerobic two-stage digestion process. The model concept implemented in the simulation software package MATLAB(TM)/Simulink(R) is a derivative of the IWA Anaerobic Digestion Model No.1 (ADM1) that has been developed by the IWA task group for mathematical modelling of anaerobic processes. In the present study the original model concept has been adapted and applied to replicate a two-stage digestion process. Testing procedures, including balance checks and 'benchmarking' tests were carried out to verify the accuracy of the implementation. These combined measures ensured a faultless model implementation without numerical inconsistencies. Parameters for both, the thermophilic and the mesophilic process stage, have been estimated successfully using data from lab-scale experiments described in literature. Due to the high number of parameters in the structured model, it was necessary to develop a customised procedure that limited the range of parameters to be estimated. The accuracy of the optimised parameter sets has been assessed against experimental data from pilot-scale experiments. Under these conditions, the model predicted reasonably well the dynamic behaviour of a two-stage digestion process in pilot scale. (C) 2004 Elsevier Ltd. All rights reserved
Systems analysis of urban wastewater systems - Two systematic approaches to analyse a complex system
High-quality observation of surface imperviousness for urban runoff modelling using UAV imagery
Modelling rainfall–runoff in urban areas is increasingly applied to support
flood risk assessment, particularly against the background of a changing
climate and an increasing urbanization. These models typically rely on
high-quality data for rainfall and surface characteristics of the catchment
area as model input.
While recent research in urban drainage has been focusing on providing
spatially detailed rainfall data, the technological advances in remote
sensing that ease the acquisition of detailed land-use information are less
prominently discussed within the community. The relevance of such methods
increases as in many parts of the globe, accurate land-use information is
generally lacking, because detailed image data are often unavailable. Modern unmanned aerial vehicles (UAVs) allow
one to acquire high-resolution images on a local level at comparably lower
cost, performing on-demand repetitive measurements and obtaining a degree of
detail tailored for the purpose of the study.
In this study, we investigate for the first time the possibility of deriving
high-resolution imperviousness maps for urban areas from UAV imagery and of
using this information as input for urban drainage models. To do so, an
automatic processing pipeline with a modern classification method is proposed
and evaluated in a state-of-the-art urban drainage modelling exercise. In a
real-life case study (Lucerne, Switzerland), we compare imperviousness maps
generated using a fixed-wing consumer micro-UAV and standard large-format
aerial images acquired by the Swiss national mapping agency
(swisstopo). After assessing their overall accuracy, we perform an
end-to-end comparison, in which they are used as an input for an urban
drainage model. Then, we evaluate the influence which different image data
sources and their processing methods have on hydrological and hydraulic model
performance. We analyse the surface runoff of the 307 individual
subcatchments regarding relevant attributes, such as peak runoff and runoff
volume. Finally, we evaluate the model's channel flow prediction performance
through a cross-comparison with reference flow measured at the catchment
outlet.
We show that imperviousness maps generated from UAV images processed with
modern classification methods achieve an accuracy comparable to standard,
off-the-shelf aerial imagery. In the examined case study, we find that the
different imperviousness maps only have a limited influence on predicted
surface runoff and pipe flows, when traditional workflows are used. We expect
that they will have a substantial influence when more detailed modelling
approaches are employed to characterize land use and to predict surface
runoff. We conclude that UAV imagery represents a valuable alternative data
source for urban drainage model applications due to the possibility of
flexibly acquiring up-to-date aerial images at a quality compared with
off-the-shelf image products and a competitive price at the same time. We
believe that in the future, urban drainage models representing a higher
degree of spatial detail will fully benefit from the strengths of UAV
imagery