Abstract

The Swedish Nuclear Fuel and Waste Management Company (SKB) applied in 2011 for a permit to construct a disposal facility in the municipality of Östhammar. Given this is still an ongoing permit process the aim with this study is to investigate how informed the Swedish citizens are in these issues. Telephone interviews were conducted in December 2018 to January 2019. A majority of the citizens, 55%, are aware of the plans of a nuclear waste repository. Most don’t know where the repository is planned to be located, but surprisingly many knows that copper canisters are suggested to be used. This together with a cluster analysis is presented and discussed in the paper.

Abstract

In 2011 the Swedish Nuclear Fuel and Waste Management Company (SKB) applied for a permit to construct a disposal facility in Östhammar. The Swedish government is expected to make a decision in 2019. The Swedish National Council of Nuclear Waste did a survey to investigate how informed the Swedish Parliamentary Members were in these issues. The first study was done with Members of Parliament (MP) in 2013 and the second with the MPs in 2016. The results of these surveys is discussed in this paper.
Most MPs were aware of the ongoing application process. Rather surprisingly, there were more politicians who knew about the suggestions to use copper canisters, than knew that it is the government that will take a final decision on the matter.

Abstract

This paper presents a power management strategy to control a DC microgrid considering the operation in the grid connected mode. The analyzed system is composed of the utility grid interfaced with a voltage source converter, an energy storage system (ESS), a distributed generator and the customer loads. The proposed power management is considered as a master-slave technique, in which the VSC operates as a master grid-forming converter, while the ESS is a slave grid- supporting unity and the distributed generator works as a grid-feeding unity tracking the maximum power point. This management strategy is presented in details and its impact over the DC link voltage, the power flow and the ESS state of charge is analyzed. MATLAB/Simulink simulations are performed to obtain the results. The obtained results show that the proposed strategy is reliable and leads to better controllability over the power flow in the DC microgrid when compared with the hierarchical control.

Abstract

An optimal lighting maintenance plan that considers the lumen degradation failure is proposed for energy efficiency lighting retrofit projects. In lighting retrofit projects, lamp population is subject to decay, resulting in reduction of the project performance. The decay of lamp population is mainly caused by the burnout failure or lumen degradation failure. In the previous studies, lighting maintenance plan is investigated by modelling the burnout failure. In this study, we present an optimal lighting maintenance plan by modelling the lumen degradation failure. The effectiveness of the formulated maintenance plan is demonstrated by a practical residential light-emitting diode (LED) lighting retrofit project.

Abstract

Permeability is known as a key factor affecting the gas production effectiveness from the natural hydrate reservoir. The formation and dissociation processes of gas hydrate in the sediments also have an influence on the permeability. In this study, samples from hydrate reservoir in Qilian Mountain permafrost were taken for the measurement of permeability changes before hydrate formation, with hydrate and also after hydrate dissociation. An unexpected permeability decrease was observed after the dissociation of methane hydrate, which was explained as the “reservoir formation damage”. Permeability variation is also related to hydrate saturation in the sediments.

Abstract

The prediction of building heat demand using engineering models will take unbearable long simulation time when they are applied to large energy networks. To deal with this problem, this paper uses the artificial neural network (ANN) to replace the engineering model in predicting the heat demand of buildings in a district heating network. To train the ANN with efficient learning process, the key data, such as the weather profiles, building fabrications, heating times, and customer heat demand, is collected from the simulation results of sample buildings in engineering models. The ANN trained with data from sample buildings is finally used to predict the heat demand of buildings in a district. In addition, different number of sample buildings for data collection and different percentage of data for training are achieved to balance prediction performance and training speed. The result shows that the ANN-based statistical model has a strong capability to accurately predict the heat demand of buildings with different types of operational functions in a district-level energy network.

Abstract

CO2 enhanced gas recovery (CO2-EGR) technology can exploit more natural gas fuels from the depleted gas reservoir and simultaneously sequestrate CO2 into the underground formation. The perforation position of CO2 injection well and injection parameters play key roles to the natural gas recovery of CO2-EGR applications. In this work, CO2-EGR simulations in a quarter of square ‘five-spot’ well arrangement of a depleted natural gas reservoir were carried out with perforation positions of CO2 injection well at the bottom, middle and top layers of the reservoir model. The optimal perforation position is determined as the top layer of the reservoir, and the reason should be attributed to the accelerated vertical displacement due to the gravity effect. Moreover, an optimization method was built by integrating genetic algorithm (GA) and TOUGH2 for the determination of the optimal injection rate. The optimal injection rate of CO2 is obtained as 0.0824 kg/s while the perforation is set at the top layer of the reservoir, and the final natural gas recovery achieves up to 65.37%. This work provides some insight for the CO2-EGR employment in the depleted natural gas reservoirs.

Abstract

Researchers of this paper have shown interest in low carbon high-rise buildings due to limited available studies in Hong Kong. In this study, a potential pathway to carbon reduction through an extensive use of Building Integrated Photovoltaics (BIPV) in low energy high-rise buildings is explored. A typical high-rise building model is developed to conduct a comparative lifecycle energy and carbon assessment based on the Zero Emission Building-Operational and Materials Embodied Energy (ZEB-OM) ambition level of the Norwegian Research Centre on Zero Emission Buildings. The net total impact is expressed in terms of the Cumulative Energy Demand (CED) and Global Warming Potential (GWP).
The results show an increase in GWP for the material production and maintenance phases due to the use of BIPV façades in the alternative design scenario. However, GWP and operational energy reduction from the BIPV generated power far outweigh the increment caused by its production and maintenance. As a result, about 21% reduction in GWP can be achieved compared with the reference model. Also, the BIPV façade is found to be economically viable with a payback period of 4.13 years. Future research will be expanded to all lifecycle phases and other BIPV materials.

Abstract

Heating, Ventilating and Air Conditioning system is leading a trend of optimization for occupant-relevant built environment energy performance. In this study, we present a new indicator, comfort equity and optimization technique to improve this occupant-related system energy performance comprehensively with the utilization of indoor trajectory data. Multi-objective particle swarm optimization algorithm is used to conduct optimal temperature setpoint solutions to optimize thermal comfort, comfort equity and energy efficiency.

Abstract

Natural gas hydrate (NGH) is a potential fuel resource. Radial Jet Drilling (RJD), turning sharply in the casing and drilling laterals by using water jet, is a valid approach to solve problems of high cost, low efficiency and formation collapse during the exploitation of NGH resources in permafrost and continental margins. Traditional finite element methods, which tend to produce mesh distortion, cannot accurately depict the water jet drilling efficiency. This paper presents a numerical investigation of Arbitrary Lagrangian Eulerian (ALE) method for analyzing both NGH and Hydratebearing Sediments (HBS) erosion process using water jet. Firstly, a coupled nozzle‐target model is solved by ALE method. The material constitutive models are established based on the characteristics of water, NGH and HBS. After that, several case studies are conducted in air, submerged water and confining pressure environments (different working conditions). Not only the flow field, but also the deformation and erosion of the materials induced by water jet are estimated. Finally, the simulation results, such as damage field, variation of internal material stress and erosion pit characteristic, are compared with each other. The relation curves between erosion depth and hydraulic parameters are consistent with the experimental results. The results show that the ALE method can better simulate the water jet flow field, by which the water jet rock breaking simulation is more in line with the reality and accurately predict the fracture result. Additionally, water jet has obvious destructive/damage effect on NGH and HBS, the presence of confining pressure will inhibit the breaking of materials.