• Energy Research
• 2016-2025close
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Abstract The urge to increase renewable energy penetration into the power supply mix has been frequently highlighted in response to climate change. South Korea was analyzed as a case study for which the government has shown motivation to increase renewable energy penetration. Herein, a hybrid renewable energy system (HRES) including solar and wind energies were selected due to their relatively stable and mature technology. In addition, Power-to-X has been incorporated to cover other renewable energy options such as hydrogen and synthetic natural gas (SNG). Therefore, an approach of forecasting the weather characteristics and demand loading over a relatively long timeframe was implemented via deep learning techniques (LSTM and GRU) and statistical approaches (Fbprophet and SARIMA), respectively. A deployment strategy incorporating HRES and Power-to-X is then proposed in correspondence to the forecasted results of the 15 regions considered in this study. An extension of this, the reliability of the designed system is further assessed based on the probability of the demand losses with the aid of Monte-Carlo simulation. With the proposed deployment strategy, a total annual cost of 9.88 × 1011 $/year and a greenhouse gas reduction of 1.24 × 106 tons/year are expected for a 35% renewable energy penetration. However, only SNG shows relatively competitive cost (at 23.20 $/m3 SNG), whereas the average costs of electricity (0.133 $/kWh) and hydrogen (7.784 $/kg H2) across the regions are yet to be competitive compared to the current market prices. Nonetheless, the priority of deployment across regions has been identified via TOPSIS.

Abstract As interest in the distributed generation of solar power system in a building facade continues to increase, its technical performance (i.e. the amount of electricity generation) should be carefully investigated before its implementation. In this regard, this study aimed to develop the nine-node-based finite element model for estimating the technical performance of the distributed generation of solar power system in a building facade (FEM9-node), focusing on the improvement of the prediction performance. The developed model (FEM9-node) was proven to be superior to the four-node-based model (FEM4-node), which was developed in the previous study, in terms of both prediction accuracy and standard deviation. In other words, the prediction accuracy (3.55%) and standard deviation (2.93%) of the developed model (FEM9-node) was determined to be superior to those of the previous model (FEM4-node) (i.e. 4.54% and 4.39%, respectively). The practical application was carried out to enable a decision maker (e.g. construction manager, facility manager) to understand how the developed model works in a clear way. It is expected that the developed model (FEM9-node) can be used in the early design phase in an easy way within a short time. In addition, it could be extended to any other countries in a global environment.

Abstract Considerable effort has been directed at improving the power conversion efficiency of organic photovoltaics, using oxide/metal/oxide multilayers as transparent electrodes, because of their numerous advantages including lower sheet resistance, higher transmittance, and higher flexibility in comparison to typical indium tin oxides. However, to date, most organic photovoltaics based on oxide/metal/oxide electrodes exhibit a lower conversion efficiency than indium tin oxide-based organic photovoltaics, without any clarification. In this investigation, we identify crucial factors that influence the power conversion efficiency of oxide/metal/oxide-based organic photovoltaics to fully exploit the potential of these devices, based on the correlation between the optical cavity and the transmittance. For this purpose, we fabricate five sets of inverted organic photovoltaics using poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) and [6,6]-Phenyl C71 butyric acid methyl ester-based active layers and ZnO/Ag/ZnO electrodes with top ZnO layers of varying thicknesses, with reference organic photovoltaics using indium tin oxides, on both rigid and flexible substrates. The highest power conversion efficiency of 8.71% and 7.53% is obtained from single-junction organic photovoltaics with 40/9/8-nm-thick ZnO/Ag/ZnO electrodes on each substrate, due to strong micro-cavity effects between the top and bottom Ag layers, despite the relatively low transmittance of the electrode. This result is supported by the relation between the electric-field intensity and the transmittance curves of the ZnO/Ag/ZnO/solution-based ZnO/active bulk optical stacks based on simulation results. Furthermore, flexible organic photovoltaics with the ZnO/Ag/ZnO electrodes demonstrate much better performance in mechanical bending tests in comparison to the performance of standard indium tin oxide-based organic photovoltaics, and the previously reported oxide/metal/oxide-based organic photovoltaics.

Abstract Based on an extensive dataset containing aggregated hourly energy consumption readings of residents during March 2011 and October 2012 in South Ontario, Canada, this paper estimates the energy consumption of circulating pumps of residential swimming pools (CPRSP) non-intrusively, and quantifies the impact of CPRSP on the power system. The main challenges are that, first, widely used non-intrusive appliance load monitoring (NIALM) methods are not applicable to this work, due to the low sampling rate and the lack of the energy consumption pattern of CPRSP; second, temperature-based building energy disaggregation methods are not suitable for this work, as they highly depend on the accurate base load estimation and predefined parameters. To overcome these issues, in this paper, first it is found that, during the pool season, for homes with and without swimming pools, the ratio between their base loads is approximately equal to the ratio between their temperature-dependent energy consumptions, then a novel weighted difference change-point (WDCP) model has been proposed. The advantages of the WDCP model are that, on one hand, it doesn’t depend on the base load estimation and predefined parameters; on the other hand, it has no requirement on the data sampling rate and the prior information of energy consumption patterns of CPRSP. Based on the WDCP model it is shown that, the average hourly energy consumption of CPRSP is 0.7425 kW, and the minimum and the maximum hourly energy consumptions are 0.5274 kW at 9:00 and 0.9612 kW at 17:00, respectively. At the peak hour 19:00, July 21, 2011, CPRSP contributes 20.36% energy consumption of homes with swimming pools, as well as 8.48% peak load of all neighborhoods. As a result, the peak load could be reduced by 8.48% if all CPRSP are stopped during the peak hour.

Abstract Reducing a building’s energy consumption and providing better indoor environmental quality (IEQ) are the two major issues that building professionals are facing all over the world. It is not easy, however, to simultaneously address both issues. Therefore, this study aimed to establish the optimal occupant behavior that can simultaneously reduce total energy consumption and improve the IEQ, using an energy simulation and optimization tool. This study also developed an integrated IEQ score by combining three different IEQ indices (i.e., thermal comfort, indoor air quality (IAQ), and visual comfort) for building users to easily understand the IEQ condition. To analyze the effects of occupant behavior by region, the education facility was selected as the target facility, and five target regions were selected considering the Koppen climate classification system and the C40 Cities Climate Leadership Group. Finally, a total of 5 × 1.01 × 1022 occupant behavior combinations can be generated in the five target regions. As a result, among the four target variables (i.e., total energy consumption, thermal comfort, IAQ, and visual comfort), the total energy consumption of the optimal solution was found to have changed most dramatically compared to that of the basic condition in terms of percentage (94.7%), due to its strong correlation with the overall occupant behavior (the highest correlation coefficient: 0.879). Therefore, it is shown that occupant behavior has more influence on the total energy consumption than on the three IEQ indices. Among the three IEQ indices, the IAQ of the optimal solution decreased most significantly compared to that of the basic condition (the highest reduction ratio: 4.04% in Ulsan), which indicates that the IAQ has more influences on the integrated IEQ score than thermal and visual comfort. The facility manager and the building user can operate the building for reducing total energy consumption and improving the IEQ considering occupant behavior, which can be used as the building management guideline in various regions.