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.
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.
The combination of a solid oxide fuel cell (SOFC) and a gas turbine (GT) provides high-efficiency power generation solutions and is currently a popular field of research. In this study, a supercritical carbon dioxide Brayton cycle (SCO2BC) was incorporated into an SOFCGT system as a bottom-layer subsystem to absorb the high-temperature exhaust of the GT, with the aim of fully realizing the cascade utilization of energy. Then, process simulation and sensitivity analysis of the SOFC-GTSCO2BC hybrid system were conducted to investigate the effects of five parameters (fuel flow rate, fuel cell operating temperature, gas turbine pressure ratio, fuel utilization factor, and CO2 turbine inlet pressure) on the thermal efficiencies of the hybrid system and its SOFC-GT and SCO2BC subsystems.
An increasing demand for sustainable gaseous fuels, such as biomethane and hydrogen, stimulated intensive efforts for developing new technologies and novel materials for gas separation and storage. Herein, a feasible strategy is developed for fabricating metalorganic frameworks (MOFs) nanofiber via combining electrospinning and in-situ growth method for high performance of biogas upgrading and storage. This approach rends the highly porous MOF materials highly distributed on the surface of the PAN nanfiber, which affords the resultant hierarchical porous structures without sacrificing their extraordinary properties such as ultra high surface area, thus contributing to the excellent gas storage capacities. The approach thus providing an promising strategy for structuring MOFs for gas storage applications.
This study established a heat-transfer model for pipeline networks, taking into account the attenuation and delay for district energy systems. The model can transform the hourly load of each building into the hourly output of the energy station to level the load. Furthermore, the hourly output of the energy station was calculated based on three scenarios that represented the locations of energy stations. The results indicated that there was a great difference between the superposition value of all the users and the output of the energy station.