Abstract

This work focuses on a multi-scale framework for the design and comparison of low-carbon heat generation solutions to serve the residential and commercial thermal energy demand of high energy density urban areas. The adopted methodology assesses the cost and performance of four configurations integrated in a district heating network: (i) centralised cogeneration with gas turbine and bottoming steam turbine with flexible heat-to-electricity ratio; (ii) centralised cogeneration with gas-fired internal combustion engine; (iii) distributed building-integrated ground-source heat pumps for domestic hot water only; and (iv) distributed building-integrated ground-source heat pumps for both domestic hot water and space heating. Cost and performance data were obtained by conducting relevant market research and developing a simplified heat pump thermodynamic model. The different configurations are evaluated utilizing whole-year space heating and hot water demand profiles for the Isle of Dogs area in East London, UK. Scale effects are included by considering various technology size scenarios and the results indicate that a 50 MW centralised internal combustion cogeneration system appears to be the most profitable option, while the competitiveness of building-integrated heat pumps is dependent on their size.

Abstract

Widely known as the largest contributor to global carbon emissions, electricity sector has always been considered as a top priority for carbon emission reduction. Global energy interconnection (or, connecting power grids in different nations) could be one of the important measures to maximize the use of renewable/clean energy in different nations. However, its effects in carbon emission reduction have not well studied in a quantitative way. Taking North America as an example, this study uses a bottom-up energy system optimization model to study the carbon emission reduction effects of different interconnection scenarios. To capture the multiple possibilities of energy interconnection, we set up two scenarios for electricity demand: high and low; and two scenarios for power grid interconnection, weak connection and strong connection. The power electricity supply in different nations will change because of the different interconnection scenarios, which will make the CO2 emission generated by electricity go up or down. When considering the power substitution and strong connection scenario, carbon dioxide emissions can be reduced by as much as 48% compared with the weak connection scenario.

Abstract

In this paper, two bio-inspired meta-heuristic optimization techniques, e.g., cuckoo and harmony search optimizations, are proposed to optimally design a power system stabilizer (PSS) for a 3-machine, 9-bus Western System Coordinating Council power system. For simultaneous control of damping factor and damping ratio, an eigenvalue-based multiobjective function is explored to damp out the low-frequency oscillations from the system. The parameters of PSS are designed so that lightly and/or unstable damped mode eigenvalues are placed to a particular D-shape region in the left half of the s-plane. These optimisation techniques are used to determine PSS parameters and compared with the same parameters obtained by genetic algorithm, particle swarm optimization. The performance of all intended PSS controllers are observed, for three specific operational cases as well as unforeseen operating cases by eigenvalues analysis; non-linear simulations and performance indices, under a severe disturbance. The comparative analysis has revealed that the cuckoo search optimization based PSS design significantly improved the damping of the system.

Abstract

The thermal conductivity of the I-β cellulose nanocrystal is one of the basic thermal physical properties which can affect its utilisation. The precise simulation of the temperature gradient of cellulose nanocrystal is the preliminary step for calculation of the thermal conductivity. In this study, both the non-equilibrium molecular dynamics and its reverse method are employed with different thermostatting methods. A triclinic box containing 4×4×8 unit cell is built with the β-D-glucose as the monomer structure of cellulose molecules. The simulation is performed under the ambient temperature and pressure. The reactive force field, i.e., ReaxFF is used. The exact temperature profile obtained indicates that the molecular dynamics simulation is a promising and capable method to calculate the thermal properties of cellulose nano crystal.

Abstract

Supercapacitor (SC) is a novel and potential device in energy storage system (ESS), which owns the characteristics of high power density, fast response time, and long lifetime expectancy. As closely related to the reliability of SCs, lifetime estimation plays an important role in performance evaluation and device sizing. This paper presents a review on SC lifetime models, and depicts the reliability-oriented design procedure of SCs system. At first, physics-of-failure (PoF) mechanism is discussed as the fundamental of lifetime modeling. Afterwards different models from literature are analyzed systematically according to different concern of stressors. At last, a reliability-oriented design procedure is given for SCs system, from the perspective of users. This paper serves to provide a clear picture of the stateof-the-art research in lifetime modeling, and give some application-oriented suggestions and future research directions for SCs.

Abstract

With increasing capacity of renewable energy power generation system, energy storage sizing problem raised with growing attention. Optimal energy storage capacity minimizes system cost while ensuring renewable energy meet grid codes. The modified minmax dispatch method has been proved to be one of the superior dispatching methods in wind power integration. In this paper, this dispatching method is applied to photovoltaic grid-connected system, and the corresponding optimal capacity of energy storage system is calculated. Moreover, state of charge (SOC) and depth of discharge (DOD) is considered in the determination of energy storage capacity. Using lifetime cost function as the optimization objective of energy storage capacity. The data of this study are derived from the measured data of the photovoltaic power generation experimental platform in Jinan, China.

Abstract

Cooling performance of a portable cold box for cold chain was studied in this paper. The effects of melting point of the phase change materials (PCMs), the locations of the PCMs, and the insulation material on the cooling duration time were numerically compared using the experimentally validated model. Firstly, five distributions of PCMs inside the box (case 1: 100% of the PCMs at the top, case 2: 20% at the top and 20% on each side wall, case 3: 25% on each side wall, case 4: 20% on each side wall and 20% at the bottom, case 5: 100% at the bottom). Secondly, five different PCMs, with melting point at 2 °C, 3 °C, 4 °C, 5 °C and 8 °C respectively, were used to verify the cooling effect of the box. Finally, two different insulation materials (polyurethane, vacuum insulated panels) were compared under the same operation conditions. It was found that different PCMs locations, melting point of the PCMs and the insulation materials leaded to different cooling duration times. The location of PCMs with 20% at the top and 20% on each side wall, the melting point at 3°C, and the vacuum insulated panel (VIP) as the insulation material could maximize the cooling duration time of the box.

Abstract

To reduce the fuel consumption and toxic emissions, this paper developed a plug-in hybrid hydrogen vehicle (PHHV). The PHHV is powered by a hybrid hydrogen-gasoline engine (HHGE) which is fueled by the pure hydrogen at the cold start to minimize HC and CO. For normal working conditions, the HHGE is fueled with hydrogen and gasoline simultaneously to gain higher thermal efficiency. Furthermore, the PHHV has adopted the idle elimination and hydrogen restart strategy to cancel the idling condition. The hydrogen consumed by the HHGE is produced by an onboard water electrolysis hydrogen generator placed in trunk of the PHHV. The hydrogen generator could gain electricity from charging pile of the electric vehicle to realize the plug-in hydrogen production. The performance of PHHV is also tested according to the New European Driving Cycle. The test results showed that, compared with the original engine fueled with the pure gasoline, HC, CO and NOx emissions from the PHHV were respectively reduced by 57.8%, 52.1% and 10.2% within the driving cycle. Moreover, PHHV also acquired a 12.2% reduction in the total fuel consumption.

Abstract

We do not know the impact of distribution network constraints on grid expansion planning and how uncertainty may influence the transmission and distribution level investment decisions. This paper presents a novel stochastic integrated grid planning approach considering distribution network constraints, combining a two-stage optimization grid expansion model with a distribution network hosting capacity (HC) assessment for a stylized representation of the Malaysian grid. Our result shows that omitting distribution constraints and ignoring uncertainty in grid investment planning has a significant impact on the optimal solution and quantifiable economic consequences. We also evaluate the benefit of integrating solar PV and battery storage, which, as we show can lead to potential savings of 0.86% ($2.37billion) of the expected cost.

Abstract

Electricity thefts in connivance with employees of electricity distribution companies, remain the Achille’s heel of power sector, addressing which continue to be the holy grail. The lackluster performance of technological measures to curb electricity thefts highlights the need to investigate the human aspectstoo. That’s what this study aims at. The findings, grounded in the responses of the nineteen employees of the Indian electricity distribution companies, detail the factors that induce employees to collude with consumers in electricity theft.