Numerical and computational analyses of interface position during inward solidification of composite phase change materials (PCM) in spherical container were explored in this study. The applications of methods such as perturbation, strained coordinates and (improved) quasi-steady solution on spherical inward solidification were investigated and compared with the results of numerical simulation. The solidification positions of porous composite PCM with different porosities solved by strained coordinates and (improved) quasi-steady methods were compared when the Stefan number was 0.1. The complete solidification time was found to be rapidly shortened as the porosity decreased.
Ambitious targets were set in Sweden to increase the share of renewable energy resources and reduce greenhouse gas emissions. Renovating old detached houses can assist in achieving the abovementioned targets, since they make up a great share of the final energy consumption and carbon dioxide emissions in Sweden. Although, several attempts were taken to improve the energy performance of the detached houses, the implementation of energy efficient renovation is yet low due to mainly high investment cost. Former studies evaluated the cost effectiveness of various energy efficient renovations in renovating detached houses in Sweden, but they provided no information how possible climate futures affect the determination and adoption of energy efficiency policies, such as monetary instruments. Accordingly, this study considered three distinct energy renovation packages and analyzed the subsidies required for implementing renovation packages for given interest rates and lifetimes. Furthermore, three different climate scenarios were considered to analyze the effect of possible climate futures on subsidies required. The analyses of results show that increasing the lifetime have greater impact on required subsidies than increasing the interest rate. Furthermore, the results show that variation in future climate conditions changes the required subsidies when implementing energy efficiency renovations. Results can be used as an aid when adopting energy efficiency policies.
Detachment from the national gridline makes the remote mines in the cold climate regions of Canada solely dependent on diesel generators for power generation purposes. Notwithstanding, more than 30% of the consumed diesel by these generators is frittered away as heat through the exhaust. To endure the long harsh winters, these mines also require substantial amounts of heating which is usually provided by burning diesel or propane. In such a scenario, the installation of a diesel exhaust heat recovery system in these remote mines has been considered as a sustainable strategy to preheat the mine intake air. However, this combined heat and power generation strategy cannot provide all the necessary heating due to the daily misbalance between the heating demand and the available heat in the exhaust of the diesel generator. Coupling seasonal thermal energy storage with the waste heat recovery system is a possibility that seeks to resolve such issue. This study investigates the integration of a seasonal thermal energy storage with a diesel exhaust heat recovery system in a remote mine in northern Canada by analyzing several possible alternatives regarding capacity and rates of energy loss. The financial impact of these parameters has been added to show the viability of the proposed strategy
CO2 capture from high operating temperatures are of special interest as it is economically appealing over low temperature CO2 capture process in Post-combustion capture. This work contributes to the estimation of new and complementary density data for CO2 confined in ‘L’ shaped carbon slit pores at high temperatures and pressures. CO2 adsorption capacities in ‘L’ shaped carbon slit pores of heights 20Å, 31.6Å, 63.2Å, 94.85Å and 126.5Å at 673.15 K and 873.15 K over a pressure range of 500 kPa to 4000 kPa are predicted by Grand Canonical Monte Carlo simulations. Elementary Physical Model is employed to model CO2 at these temperatures and pressures both in bulk and confined phase. CO2 adsorption capacities and the unique structural properties of the confined CO2 at all the condition mentioned above has been estimated in presence of the wall-fluid interactions and the fluid-fluid interactions. The Steele wall potential is used to model the wall-fluid interactions inside carbon-based adsorbents that have a slit shaped geometry.
This study investigates a fuel spray development process of gasoline–biodiesel blended fuel (GB) in macroscopic and microscopic scales. Long-distance microscopy and shadowgraph were utilized as optical methods to capture the highly transient spray development. Different injection pressures were tested, which ranged from 40 to 120 MPa with a fuel temperature of 323K. Tested four fuels were neat gasoline and biodiesel addition (5%, 20%, 40% by volume) to gasoline in three different ratios. The results regarding the development process for the initial spray near the nozzle show that the spray penetration and the spray tip velocity both decreased with decreasing biodiesel blending ratio. This relationship appears to be due to the associated differences in the mass flow rate and the radial direction velocity vector of the spray. In addition, the different spray tip velocities at the start of spraying result in different atomization regimes between the fuels. The GB fuels with the low biodiesel blending ratio were disadvantaged in spray atomization due to their lower spray penetration and tip velocity. However, as the injection pressure increased, the differences in microscopic spray penetrations between the fuels became smaller, along and there were changes in the atomization characteristics.
Accurate and robust real-time state estimation is essential to the reliable and safe operation of the hybrid energy storage system. This paper handles a closed-loop method for state-of-charge estimation of lithium-ion battery and ultracapacitor hybrid system. In this work, a fractional-order model is developed to approximate the dynamic behavior of the lithium-ion battery and ultracapacitor. Then, a closed-loop method is proposed for model parameter and state-of-charge estimation. Experiments under dynamic load profiles are used to verify the proposed method. The experimental results indicate that the proposed method can obtain robust estimation results for the hybrid energy storage system, and is appropriate for real-time systems.
Phase change material board (PCMB) is considered high potential as an efficient passive solution to energy saving in building applications, especially in hot weather. A numerical investigation is conducted on PCMB, with both sides subjected to periodical temperature variations to examine its thermal behaviour. The experimentally validated model is based on the enthalpy method. The inner surface temperature variation is used as a comparison factor, further with two newly introduced parameters, thermal comfort ratio (TCR) and energy saving potential (ESP), to parametrically analyse the influencing factors in terms of both thermal comfort and energy saving aspect. Melting range, latent heat capacity, convective heat transfer coefficients for inner/outer surfaces, thermal conductivity and PCMB thickness are studied parametrically. Furthermore, the optimal heat storage capacity of a PCMB placed on the inner side of a traditional brick-concrete exterior wall is theoretically obtained.
To support home energy management, users or operators prefer appliance-level energy consumption information than the house monthly electricity bill report. Two methods exist for appliance energy usages recognition: Non-intrusive Load Monitoring (NILM) and Intrusive Load Monitoring (ILM). Both have not been widely used due to either insufficient performance or high cost. This paper proposed a practical socket-level non-intrusive load monitoring method. First, through socket submeters, the load disaggregation accuracy can be improved by reducing occurrences of indistinguishable appliances when using simple power features; Second, by involving users’ feedback, the load classification accuracy can be enhanced by feature registration and match. An unsupervised hierarchical clustering algorithm was used for load disaggregation, and the dynamic time wrapping algorithm was used for appliance feature match. This method was validated through a public dataset and showed a great promise.
This study use a dynamic multi-sectoral CGE model with different nested structure and substitution elasticity for electricity sectors with different power sources to capture the effects of reducing renewable electricity curtailment across all economic sectors. We found that the reduction of renewable electricity curtailment would lead to a significant increase in renewable electricity generation, and a moderate decrease in non-renewable electricity generation. Among the renewable powers, wind power has the largest increase in activity level. Secondly, the reduction of renewable electricity curtailment would bring green co-benefits that carbon dioxide and air pollutant emissions from power sectors fall significantly, meantime national GDP and employment have slight increases. Third, without the cost-neutrality assumption, the impacts of reducing electricity curtailment would be largely over-estimated with CGE model. Fourth, if with multi-value simulations of CES substitution elasticity, the disparity on nested structure of power sectors would not cause serious disagreement on simulation results.
A periodic stepped fin microchannel heat sink (PSFMC) is developed to stabilize microchannel flow boiling operation and thereby improve the two-phase heat transfer performance. Flow boiling experiments are performed on the 25mm x 25mm copper based heat sink using de-ionized water as the coolant. The flow boiling performance of this heat sink is benchmarked against a conventional straight microchannel heat sink (SMC). Unlike the SMC where the confined flow passages lead to bi-directional expansion of elongated vapor slugs, PSFMC facilitates expansion of vapor bubbles or slugs in the span-wise direction at the interconnected sections. Flow reversal effects are minimized and the pressure and temperature measurements are more stable compared to SMC. The improved boiling stability coupled with higher bubble nucleation activity causes the PSFMC to provide an enhanced two-phase heat transfer performance compared to SMC particularly under the lowest mass flux of 57 kg/m2s.