Financial risk management and market performance in restructured electric power markets: Theoretical and agent-based test bed studies

Electric power systems have traditionally been operated as natural monopolies. Restructuring has entailed un-bundling of hitherto vertically integrated organizations into independently managed generation, transmission and distribution systems. As a result, electric power markets can be divided into wholesale and retail layers. The wholesale power market design proposed by the U.S. Federal Energy Regulatory Commission (FERC) in an April 2003 white paper FERC (2003) encompasses the following core features: central oversight by an independent system operator (ISO); a two-settlement system consisting of a day-ahead market supported by a parallel real-time market to ensure continual balancing of electric power supply and demand. In this new environment electricity is traded like other commodities in ISO organized power pools. However, power systems must be in instantaneous power balance, i.e. demand must equal supply at all times. Moreover, at present, electric power cannot be stored economically in substantial amounts. The power flows on transmission systems are governed by physical laws of power flow such as the Kirchoff\u27s law, and are constrained by the overall capacity of transmission lines. During the peak hours of electric power demand, the above mentioned constraints become binding affecting outcomes throughout the grid. Transmission constraints in particular create congestion, which can impede the generation and/or injection of electric power into the grid in merit-order , i.e., from least-cost generator to high-cost generators. Electric power prices can be very volatile and hence, new forms of risk have arisen due to the restructuring. As part of restructuring, congestion on electricity transmission grids is now handled in many energy regions by means of locational marginal pricing (LMP), i.e., the pricing of electric energy in accordance with the location of its injection or withdrawal from the grid. The LMP so calculated at a node k measures the least cost to supply an additional unit of load at that location from the resources of the system. The difference in LMPs at any two buses is known as congestion rent, which is collected by the ISO. In the case of grid congestion, LMPs can vary widely across the grid, which creates price risk for all market participants. Using existing market design features, this thesis investigates the risk management issues of market participants and overall efficiency of the wholesale power markets. Additionally, I also study the market rules dealing with renewable energy sources

The responses of lager brewing yeast to low temperatures

The removal of yeast biomass (cropping) at the end of fermentation to inoculate a subsequent fermentation (serial-repitching) is common practice in the brewing industry. Between successive fermentations cropped yeast is stored as a slurry in cooled storage vessels under anaerobic conditions until required for subsequent use. Maintenance of yeast quality during storage is critical for subsequent fermentation performance. An assumption is made in brewing that all strains benefit from storage at 3-4°C. To test this assumption a model working system was initially established to assess cooling times of lager yeast in different suspension media. Preliminary investigations focussing on freshly propagated yeast slurry demonstrated that whilst the deleterious effects of extremely high storage temperatures on lager brewing yeast physiology was in line with expectation, utilization of traditionally recommended storage temperatures does not necessarily benefit yeast physiology when compared to slurry maintenance at slightly higher temperatures. Genome-scale transcriptional analysis in slurries cropped following an initial fermentation suggested that lager yeast might experience cold stress during slurry maintenance at typically recommended storage temperatures. In contrast, maintenance of lager yeast at a slightly higher storage temperature, in this case 10°C, yielded no adverse impact on key indicators of brewing yeast physiological state or on subsequent fermentation profiles following repitching into fermentations. Whilst these observations were not made using full production scale, they do indicate that optimal storage may not be currently being deployed for brewing yeast at full scale

Mixing global and local competition in genetic optimization based design space exploration of analog circuits

The knowledge of optimal design space boundaries of component circuits can be extremely useful in making good subsystem-level design decisions which are aware of the parasitics and other second-order circuit-level details. However, direct application of popular Multi-objective genetic optimization algorithms were found to produce Pareto fronts with poor diversity for analog circuits problems. This work proposes a novel approach to control the diversity of solutions by paritioning the solution space, using Local Competition to promote diversity and Global competition for convergence, and by controlling the proportion of these two mechanisms by a Simulated Annealing based formulation. The algorithm was applied to extract numerical results on analog switched capacitor integrator circuits with a wide range of tight specifications. The results were found to be significantly better than traditional GA based uncontrolled optimization methods

Cognitive and psychomotor effects of adjunctive aripiprazole or paliperidone in patients of schizophrenia receiving olanzapine: a double blind placebo controlled clinical study

Background: Emergence of atypical antipsychotics has revolutionized the treatment of schizophrenia by exploiting dual actions on serotonin as well as dopaminergic receptors. Still, monotherapy with these agents is insufficient to control cognitive and psychomotor as well as positive and negative symptoms. Hence combination therapy with antipsychotics is common in clinical practice. Objective of current study is to compare the effects of addition of aripiprazole or paliperidone on cognition and psychomotor functions in schizophrenia receiving olanzapine.Methods: This is prospective, double blind, placebo controlled, parallel group study in 90 patients of schizophrenia showing partial or no response to olanzapine measured by Positive And Negative Symptoms Score (PANSS) scale. They were randomly divided to receive adjuvant aripiprazole, paliperidone or placebo for 6 weeks.Results: Combination of aripiprazole and olanzapine shows significant improvement in most of the cognition and psychomotor parameters like attention, perception, verbal memory, thinking and processing as well as motor speed while combination of paliperidone and olanzapine is associated with improvement in only some of the cognitive and psychomotor parameters such as attention, perception and verbal memory only. Both the combinations are efficacious in controlling positive and negative symptoms of schizophrenia as assessed by PANSS scale.Conclusions: The best augmenting strategy with for olanzapine nonresponsive patients will be D2 receptor partial agonist like aripiprazole rather than D2 antagonist like paliperidone and other atypical antipsychotic agents for better improvement in cognition and psychomotor domains

Physiological and transcriptomic response of Saccharomyces pastorianus to cold storage

Removal of yeast biomass at the end of fermentation, followed by a period of storage before re-inoculation into a subsequent fermentation, is common in the brewing industry. Storage is typically conducted at cold temperatures to preserve yeast quality, a practice which has unfavourable cost and environmental implications. To determine the potential for alleviating these effects, the transcriptomic and physiological response of Saccharomyces pastorianus strain W34/70 to standard (4°C) and elevated (10°C) storage temperatures was explored. Higher temperatures resulted in increased expression of genes associated with the production and mobilisation of intracellular glycogen, trehalose, glycerol and fatty acids, although these observations were limited to early stages of storage. Intracellular trehalose and glycerol concentrations were higher at 4°C than at 10°C, as a consequence of the cellular response to cold stress. However, significant changes in glycogen degradation or cellular fatty acid composition did not occur between the two sets of populations, ensuring that cell viability remained consistent. It is anticipated that this data may lead to changes in standard practice for handling yeast cultures, without compromising yeast quality. This work has significance not only for the brewing industry, but also for food and biofuel sectors requiring short term storage of liquid yeast

A Study of the Impact of Reduced Inertia in Power Systems

Inertia in power systems plays an important role in maintaining the stability and reliability of the system by counteracting changes in frequency. However, the traditional sources of synchronous generation are being displaced by renewable resources, which often have no inherent inertia. This paper investigates the impact of reduced system inertia on several aspects of the dynamic stability of power systems, such as angular stability, primary frequency response, and oscillatory modes. This study is performed on a large-scale 2000 bus synthetic Texas model by selectively replacing synchronous generators with inverter-based generation resources. This paper also compares the analysis results obtained by the above-mentioned inertia-reduction approach of renewable integration with another approach in which the inertia constant of all synchronous generators is decreased. This paper demonstrates that only reducing the inertia of all synchronous generators in a system does not provide an accurate analysis of the challenges associated with the reduced system inertia caused by renewable integration

Process Optimisation of Steam Explosion Parameters on Multiple Lignocellulosic Biomass using Taguchi Method:A Critical Appraisal

Xylitol is a low calorie sweetener that can be produced through a bioconversion approach from lignocellulosic biomass that requires pretreatment prior to the bioconversion of xylose to xylitol. Steam explosion (SE) is an industrially scalable pretreatment (PT) process with the potential to liberate xylose monomers, however SE-PT has not been optimised for xylose release from multiple feedstock. The effect of pressure, substrate weight, phosphoric acid loading concentration and residence time on four feedstock (wheat straw (WS), corn stover (CS), Miscanthus (M), and willow (W)) for xylose release and minimal fermentation inhibitor productions (furfural and 5-hydroxymethylfurfural (HMF)) was investigated using the Taguchi methodology for design of experiment (DoE) with variation at four levels (44). An L16 orthogonal array design was utilised and all factors indicated influence on xylose release and inhibitor formation and the resulting xylose rich hydrolysate assessed for bioconversion to xylitol.. The L16 DoE gave hydrolysates containing 75-95% of xylose content in the original biomass, whilst retaining cellulose and lignin components in the fibre. The level of inhibitors were within boundary limits to enable microbial fermentation of the hydrolysates to xylitol. Fine tuning of the overall evaluation criteria (OEC) model imbibing 1.5 kg feedstock in 1.2% w/v orthophosphoric acid, 12 bar(g) and 6 minutes residence time resulted in 90% xylose recovery and production of >1000 L of wheat straw hydrolysate for bioconversion to xylitol. The advantages and limitations of the Taguchi OEC model and further improvements to this process are discussed in a biorefining contextpublishersversionPeer reviewe

Draft Genome Assemblies of Xylose-Utilizing Candida tropicalis and Candida boidinii with Potential Application in Biochemical and Biofuel Production

Non-albicans Candida species are growing in prominence in industrial biotechnology due to their ability to utilize hemicellulose. Here, we present the draft genome sequences of an inhibitor-tolerant Candida tropicalis strain (Y6604) and Candida boidinii NCAIM Y01308TpublishersversionPeer reviewe

Power market models for the clean energy transition: State of the art and future research needs

As power systems around the world are rapidly evolving to achieve decarbonization objectives, it is crucial that power system planners and operators use appropriate models and tools to analyze and address the associated challenges. This paper provides a detailed overview of the properties of power market models in the context of the clean energy transition. We review common power market model methodologies, their readiness for low- and zero‑carbon grids, and new power market trends. Based on the review, we suggest model improvements and new designs to increase modeling capabilities for future grids. The paper highlights key modeling concepts related to power system flexibility, with a particular focus on hydropower and energy storage, as well as the representation of grid services, price formation, temporal structure, and the importance of uncertainty. We find that a changing resource mix, market restructuring, and growing price uncertainty require more precise modeling techniques to adequately capture the new technology constraints and the dynamics of future power markets. In particular, models must adequately represent resource opportunity costs, multi-horizon flexibility, and energy storage capabilities across the full range of grid services. Moreover, at the system level, it is increasingly important to consider sub-hourly time resolution, enhanced uncertainty representation, and introduce co-optimization for dual market clearing of energy and grid services. Likewise, models should capture interdependencies between multiple energy carriers and demand sectors.publishedVersio