Results 1 - 10 of 11
Results 1 - 10 of 11. Search took: 0.018 seconds
|Sort by: date | relevance|
[en] In this research, an export coefficient based dual inexact two-stage stochastic credibility constrained programming (ECDITSCCP) model was developed through integrating an improved export coefficient model (ECM), interval linear programming (ILP), fuzzy credibility constrained programming (FCCP) and a fuzzy expected value equation within a general two stage programming (TSP) framework. The proposed ECDITSCCP model can effectively address multiple uncertainties expressed as random variables, fuzzy numbers, pure and dual intervals. Also, the model can provide a direct linkage between pre-regulated management policies and the associated economic implications. Moreover, the solutions under multiple credibility levels can be obtained for providing potential decision alternatives for decision makers. The proposed model was then applied to identify optimal land use structures for agricultural NPS pollution mitigation in a representative upstream subcatchment of the Miyun Reservoir watershed in north China. Optimal solutions of the model were successfully obtained, indicating desired land use patterns and nutrient discharge schemes to get a maximum agricultural system benefits under a limited discharge permit. Also, numerous results under multiple credibility levels could provide policy makers with several options, which could help get an appropriate balance between system benefits and pollution mitigation. The developed ECDITSCCP model can be effectively applied to addressing the uncertain information in agricultural systems and shows great applicability to the land use adjustment for agricultural NPS pollution mitigation. - Highlights: • An export coefficient based optimization model was developed in this research. • The model can deal with uncertainties associated with agricultural system. • The model can be utilized to support agricultural NPS pollution mitigation. • Desired land use patterns and nutrient discharge schemes can be obtained.
[en] Climate change may alter the geographical pattern and intensity of near-surface winds which are the 'fuel' for wind turbines. In a context of fast current and planned development of wind power worldwide, investigating the impacts of climate change on wind power generation is necessary. This study aims at assessing future changes in the potential for wind power generation over the whole Europe and in the effective wind power production from national wind farms operating at the end of 2012 and planned by 2020. For this purpose, a simplified wind power generation model is applied to an ensemble of 15 regional climate projections achieved from 10 Regional Climate Models down-scaling six Global Climate Models under the SRES A1B emission scenario from the ENSEMBLES project. The use of a relatively large multi-model ensemble allows the identification of robust changes and the estimation of a range of uncertainties associated with projected changes. We show with a high level of confidence that, under the A1B scenario, over most of Europe, changes in wind power potential will remain within ±15 and ±20 % by mid and late century respectively. Overall, we find a tendency toward a decrease of the wind power potential over Mediterranean areas and an increase over Northern Europe. Changes in multi-year power production will not exceed 5 and 15 % in magnitude at the European and national scale respectively for both wind farms in operation at the end of 2012 and planned by 2020. Therefore, climate change should neither undermine nor favor wind energy development in Europe. However, accounting for climate change effects in particular regions may help optimize the wind power development and energy mix plans. (authors)
[en] We study the structure of locational marginal prices in day-ahead and real-time wholesale electricity markets. In particular, we consider the case of two North American markets and show that the price correlations contain information on the locational structure of the grid. We study various clustering methods and introduce a type of correlation function based on event synchronization for spiky time series, and another based on string correlations of location names provided by the markets. As a result, this allows us to reconstruct aspects of the locational structure of the grid.
[en] Emission reduction is one of the most efficient control measures in fuel-powered locomotives. The purpose of this study was to determine the reduction in particulate matter (PM) and black carbon (BC) emissions following the installation of a fuel activation device (FAD). The FAD was developed to enhance fuel combustion by atomizing fuel and to increase the surface area per unit volume of injected fuel. Emission reduction by the FAD was evaluated by installing a FAD in an operating diesel locomotive in Mongolia. The test was conducted on a train operating on a round-trip 238-km route between Ulaanbaatar and Choir stations in Mongolia. The fuel consumption rate was slightly reduced following the FAD installation. The FAD installation decreased PM and BC emissions in the diesel locomotive, especially coarse PM. The PM10 reductions achieved after FAD installation were 58.0, 69.7, and 34.2% for the constant velocity, stopping, and acceleration stages of the train's operation, respectively. The BC reduction rates were 29.5, 52.8, and 27.4% for the constant velocity, stopping, and acceleration stages, respectively. - Highlights: • The FAD was developed to enhance fuel combustion by increasing the surface area per unit volume of injected fuel. • Emission reduction by the FAD was evaluated by installing a FAD in an operating diesel locomotive in Mongolia. • Under all operating conditions, the reduction efficiency increased as the particle diameter increased. • The FAD installation decreased PM and BC emissions from the diesel locomotives, especially for coarse PM.
[en] Life Cycle Assessment (LCA) has been used to assess the environmental sustainability of the chlor-alkali production in Europe. The three current technologies applied nowadays are mercury, diaphragm, and membrane cell technology. Despite, having achieved higher energy efficiencies since the introduction of membrane technology, energy consumption is still one of the most important issues in this sector. An emerging technology namely oxygen-depolarised cathodes (ODC) is suggested as a promising approach for reducing the electrolysis energy demand. However, its requirement of pure oxygen and the lack of production of hydrogen, which could otherwise be valorised, are controversial features for greener chlorine production. The aim of this work is to evaluate and compare the environmental profiles of the current and emerging technologies for chlorine production and to identify the main hot spots of the process. Salt mining, brine preparation, electrolysis technology and products treatment are included inside the system boundaries. Twelve environmental impact categories grouped into natural resources usage and environmental burdens are assessed from cradle to gate and further normalised and weighted. Furthermore, hydrogen valorisation, current density and allocation procedure are subjected to sensitivity analysis. Results show that the electrolysis stage is the main contributor to the environmental impacts due to energy consumption, causing 99.5–72% of these impacts. Mercury is the less environmentally sustainable technology, closely followed by diaphragm. This difference becomes bigger after normalisation, owing to hazardous waste generated by mercury technique. Conversely, best results are obtained for ODC instead of membrane scenario, although the reduction in energy requirements is lesser than expected (7%). - Highlights: • Environmental profile of emerging vs current chlor-akali technologies • LCA approach based on natural resources and environmental burdens methodology • Majority of impacts due to energy consumption in electrolysis stage • Hydrogen valorisation through electricity generation to tackle energy dependency • Expected results for emergent technology worsen due to lack of hydrogen production.
[en] Highlights: • Mk1 FHR performs favorably compared to both utility and IPP built NGCCs. • Mk1 FHR main performance drivers: electricity price, NG price, and the discount rate. • Mk1 is much more attractive in markets where NG prices are high compared to NGCCs. - Abstract: Understanding the financial performance of an engineered system is a key step to its commercialization. In this study, the economic performance of the Mk1 PB-FHR using a nuclear air combined cycle to produce base load nuclear power, and highly efficient peaking power with gas co-firing, was estimated for a regulated electricity market structure. Initially, a survey of major U.S. nuclear utility holding companies’ financials was performed to estimate a credible range of input parameters. In combination with the main cost parameters of the Mk1 estimated in a companion paper, a base case analysis was performed, demonstrating the economic attractiveness of the Mk1. A sensitivity study demonstrated that the main metrics of concern were electricity price, natural gas price, and the discount rate. These all pointed to possible ways to further reduce the Mk1’s investment risk, such as long term fuel contracts and improved construction management, in order to further increase the attractiveness of Mk1 deployment. Finally, a comparison between the Mk1 and two different natural gas combined cycle (NGCC) plants was made. The Mk1 performance lies in between a utility built and an independent power producer built NGCC. The Mk1 becomes a much more attractive investment than conventional NGCCs in markets where natural gas prices are high.
[en] The cultivation of seaweed as a feedstock for third generation biofuels is gathering interest in Europe, however, many questions remain unanswered in practise, notably regarding scales of operation, energy returns on investment (EROI) and greenhouse gas (GHG) emissions, all of which are crucial to determine commercial viability. This study performed an energy and GHG emissions analysis, using EROI and GHG savings potential respectively, as indicators of commercial viability for two systems: the Swedish Seafarm project's seaweed cultivation (0.5 ha), biogas and fertilizer biorefinery, and an estimation of the same system scaled up and adjusted to a cultivation of 10 ha. Based on a conservative estimate of biogas yield, neither the 0.5 ha case nor the up-scaled 10 ha estimates met the (commercial viability) target EROI of 3, nor the European Union Renewable Energy Directive GHG savings target of 60% for biofuels, however the potential for commercial viability was substantially improved by scaling up operations: GHG emissions and energy demand, per unit of biogas, was almost halved by scaling operations up by a factor of twenty, thereby approaching the EROI and GHG savings targets set, under beneficial biogas production conditions. Further analysis identified processes whose optimisations would have a large impact on energy use and emissions (such as anaerobic digestion) as well as others embodying potential for further economies of scale (such as harvesting), both of which would be of interest for future developments of kelp to biogas and fertilizer biorefineries. - Highlights: • Analysis of Energy and GHG was conducted for a Swedish macroalgae supply chain. • The effects of upscaling on the energy and GHG emissions performances are studied. • Energy analysis was used to also identify potentials for economies of scale. • At Sea processes were found to have the highest potential for economies of scale. • Upscaled system surpassed break even energy return on investment and GHG savings.
[en] Nowadays, water and energy consumption is intensifying every year in most of the countries. This perpetual increase will not be supportable in the long run, making urgently to manage these resources on a sustainable way. Domestic consumptions of water and electric energy usually are related and it's important to study that relation, identifying opportunities for use efficient improvement. In fact, without an understanding of water-energy relations, there are water efficiency measures that may lead to unintentional costs in the energy efficiency field. In order to take full advantage of combined effect between water and energy water management methodologies, it is necessary to collect data to ensure that the efforts are directed through the most effective paths. This paper presents a study based in the characterization, measurement and analysis of water and electricity consumption in a single family house (2 months period) in order to find an interdependent relationship between consumptions at the end user level. The study was carried out on about 200 baths, divided in four different scenarios where the influence of two variables was tested: the flow reducer valve and the bath temperature. Data showed that the presence of flow reducer valve decreased electric energy consumption and water consumption, but increased the bath duration. Setting a lower temperature in water-heater, decreased electric consumption, water consumption and bath duration. Analysing the influence of the flow reducer valve and 60 °C temperature simultaneously, it was concluded that it had a significant influence on electric energy consumption and on the baths duration but had no influence on water consumption. - Highlights: • Domestic consumption of water and electricity in the baths were assessed; • Presence of flow reducers decreases water/electricity consumption; • Presence of flow reducers increases the duration of the baths; • Lower temperature in water-heater, decreased water/electricity consumption and the baths duration; • Flow reducer and lower temperature, had a significant influence on electricity consumption and on the baths duration.
[en] Electricity prices on the European market have decreased significantly over the past few years, resulting in a deterioration of Swiss hydropower firms’ competitiveness and profitability. One option to improve the sector’s competitiveness is to increase cost efficiency. The goal of this study is to quantify the level of persistent and transient cost efficiency of individual firms by applying the generalized true random effects (GTRE) model introduced by Colombi et al. (Journal of Productivity Analysis 42(2): 123–136, 2014) and Filippini and Greene (Journal of Productivity Analysis 45(2): 187–196, 2016). Applying this newly developed GTRE model to a total cost function, the level of cost efficiency of 65 Swiss hydropower firms is analyzed for the period between 2000 and 2013. A true random effects specification is estimated as a benchmark for the transient level of cost efficiency. The results show the presence of both transient as well as persistent cost inefficiencies. The GTREM predicts the aggregate level of cost inefficiency to amount to 21.8% (8.0% transient, 13.8% persistent) on average between 2000 and 2013. These two components differ in interpretation and implication. From an individual firm’s perspective, the two types of cost inefficiencies might require a firm’s management to respond with different improvement strategies. The existing level of persistent inefficiency could prevent the hydropower firms from adjusting their production processes to new market environments. From a regulatory point of view, the results of this study could be used in the scope and determination of the amount of financial support given to struggling firms.
[en] The ability to charge battery electric vehicles (BEVs) on a time scale that is on par with the time to fuel an internal combustion engine vehicle (ICEV) would remove a significant barrier to the adoption of BEVs. However, for viability, fast charging at this time scale needs to also occur at a price that is acceptable to consumers. Therefore, the cost drivers for both BEV owners and charging station providers are analyzed. In addition, key infrastructure considerations are examined, including grid stability and delivery of power, the design of fast charging stations and the design and use of electric vehicle service equipment. Each of these aspects have technical barriers that need to be addressed, and are directly linked to economic impacts to use and implementation. Here, this discussion focuses on both the economic and infrastructure issues which exist and need to be addressed for the effective implementation of fast charging up to 350 kW. In doing so, it has been found that there is a distinct need to effectively manage the intermittent, high power demand of fast charging, strategically plan infrastructure corridors, and to further understand the cost of operation of charging infrastructure and BEVs.