Abstract

With increasing number of Electric Vehicles (EVs), more attention is being paid to EV’s charge stations. These stations play an essential role in EV industry chain. Choosing the optimal locations for these stations is becoming vitally important. Not only for power loss reduction, but also for power system security. In this paper a novel optimal charge station location method is informed based on active and reactive power flow analysis by using Genetic Algorithm (GA) in terms of power loss minimization. Results for the 36-bus Distribution Network (DN) are presented. It is demonstrated that installing three stations in optimal locations in the tested network, power loss reduces by 0.088 MW, compared with the situation with two stations.

Abstract

In order to avoid wasting resources, environmental pollution and prevent gas explosion in mine, purifying methane from low concentration coal bed methane by hydrate formation has been studied. For increasing the hydrate formation rate and methane recovery, 5.8 mol% tetrahydrofuran （ THF ） -300 ppm sodium dodecyl sulfate（SDS）solution were introduced. The key factors that influenced the gas consumption, reaction rate, methane concentration in the hydrate, methane recovery and separation factor were investigated. Experimental results indicated that the higher pressure, lower temperature, longer reaction time facilitated gas consumption, methane recovery and separation factor. The temperature was the key factor affecting the methane separation factor, and the increase of temperature is propitious to the improve selectivity of methane hydrate. Since the hydrate separation technology can substantially avoid the explosion problem caused by methane and on the basis of the results obtained in this work, we may say that this technology is quite suitable for the separation of coal bed methane mixed with air and has broad prospects for industrial applications.

Abstract

In our previous work, a traditional compound parabolic concentrator (CPC) was truncated from the positions where multiple reflections exist and a novel CPC with high efficiency and uniform flux was obtained and defined as EMR concentrator. We also figured out that there existed the highest and lowest truncation positions in EMR concentrators, which were defined as HEMR and LEMR concentrators respectively. In the present work, our objective is to design EMR concentrators with various truncation positions and obtain the optimal truncation position. Firstly, based on the geometry topology, EMR concentrators with various truncation positions were designed. Ray tracing simulation of EMR concentrators was conducted by TracePro to figure out their optical efficiencies and irradiance non-uniformities. Results showed optical efficiencies of EMR concentrators with various truncation positions were almost the same, but irradiance uniformities exhibited some difference. On one hand, for EMR concentrators with truncation positions between HEMR and LEMR, irradiance non-uniformity increases slightly with a drop in truncation position firstly and then decreases slightly. On the other hand, for EMR concentrators further truncated than LEMR, irradiance uniformity increases rapidly with a drop in truncation position. Thus, LEMR concentrator is likely to be the EMR concentrator with the optimal truncation position due to its best tradeoff between optical performance and material consumption.

Abstract

Hydrate-based technologies have been regarded as one of the most promising options for reducing greenhouse effect and obtaining clean energy resource. However, there is an ongoing search for substances which could improve the gas-liquid mass transfer without mechanical consumption and in turn enhance process economics. In this work, nanoporous materials loading the solution of promoter was proposed to promote the formation process of gas hydrate by reducing the barrier of mass and heat transfer. The pressure drop curve and gas uptake for CO2/H2/H2O hydrate formation process were studied through 13X molecular sieve loading TBAB solution, the promotion effect was also compared with the other research. The results shown that 13X molecular sieve can significantly improve the pressure drop rate and gas uptake of CO2/H2/H2O/TBAB hydrate compared with the hydrate formed by agitation.

Abstract

The renewable power systems have become more susceptible to the system insecure than traditional power systems due to the reducing inertia and damping properties. In the meantime, inevitable time delays commonly exist in different procedures of the energy systems, such as computational delay, which may lead to poor performance, or even instability. Therefore, the time-delay impacts should be properly taken into account. However, the time-delay system belongs to the class of functional differential equations mathematically. With a transcendental characteristic equation, infinite dimension will increase transformation complexity and computation pressure. To rapidly describe the time-delay impact for multiarea power systems with time delays, a dimension reduction method based on the solution operator discretization is proposed in this paper. The quantitative relationship between time delays and system damping ratio is revealed for the first time. It starts with a state space equation for the entire frequency regulation system, the spectrum of time delayed systems is transferred into the spectrum of infinite-dimensional operators, followed by discretizing the solution operator. After that, a simple approximate matrix of finite dimensions is established, which sufficiently reflects the effect of time delays. The proposed method can not only ensure low computational burden efficiency via dimension reduction, but also extract the nonlinear coupling between the time delay and the damping deterioration.

Abstract

The mix of energy supply worldwide has changed dramatically in the last few decades. In order to tackle climate change, there has been a clear movement from fossil fuels towards renewable and sustainable energy sources. Wind energy, for example, has generated 98% of Scottish electricity demand in October 2018, which has established a world-class record. On the other hand, non-renewable energies (such as oil and gas), which are not environmentally friendly, are still being recognized as the primary source of energy. This confrontation may be solved through tight integration of fossil and renewable sources. In this paper, wind sources in the Daqing oilfield of China are critically assessed to identify the potentials of using small wind turbines (SWTs) to support local oil production in remote sites. A wind power model has been built based on a one-year meteorological database. The modeling results suggested that over 80% of the original annual costs of power generation could be saved by using wind energy for oil extraction in a remote site at Daqing oilfield.

Abstract

A natural-gas-fired thermoelectric generation (TEG) system is an efficient way for simultaneously providing heat and electric power, and it can be used as a movable power system for field trips and a heatpower coordinated supply for residential homes. In this paper, a high-temperature and medium-temperature coupled TEG system driven by direct combustion heat source is proposed, and a new burner with baffle is designed to enhance the heat transfer between fired gas and the hot side of TEG. The optimal geometrical dimensions of the new burner are obtained by conducting a 2D model in ANSYS, which including combustion reactions, flow, and heat transfer in simplified TEGs. Comparative experiment results show that the inner-wall temperature of high-temperature TEG module averagely increases by 73K, and the power generation and conversion efficiency of the TEG system are improved by 42.48% and 3.38%, respectively. In order to further improve the performance of hightemperature TEG, the 2D model is developed by using an equivalent thermoelectric effects model of segmented high-temperature TEG, and its accuracy is verified by the experimental results. The influences of thermo-element length and number on TEG performance are revealed, and further improvement method, i.e. adding fins in the cold water jacket is proposed and verified.

Abstract

The efficiency of the air conditioning process can be improved by employing desiccant coated heat exchangers (DCHEs). Currently, DCHE’s performance is not sufficiently high due to the restricted sorption capacity, high regeneration temperature, and long term corrosive effect of the selected desiccating material. In this study, we have developed a composite desiccant by combining a hydrophilic superabsorbent polymer and a less corrosive potassium formate salt. Due to high absorption capacity and excellent water retention ability, the composite polymer demonstrated 4-8 times gain in the sorption capacity when compared with pure/composite silica gel. Further, it recorded two times improvement in dehumidification capacity and energy efficiency when coated on a heat exchanger as opposed to only 20-30% improvement in the case of composite silica gel with potassium formate salt. Lastly, the composite polymer desiccant could operate 2-4 times longer than silica gel coated heat exchangers.

Abstract

An optimized energy management strategy of hybrid energy plants can lead to a significant reduction in primary energy consumption. This paper documents the development of a methodology based on dynamic programming for the optimization of the energy management strategy of hybrid energy plants, with the aim of minimizing the primary energy consumption. The validity and capability of the optimization methodology presented in this paper is demonstrated by comparing its results to those obtainable by means of commonly used operation strategies. Moreover, a case study consisting of a thirteen-floors building located in the north of Italy is considered to demonstrate the developed methodology. Compared to a thermal-led operation strategy with a different switch-on priority order of plant components, the proposed methodology allows a primary energy saving between up to about 6.57 %.

Abstract

Potential future cooling energy savings can be achieved through the use of incentives. This study proposes a new electricity tariff and rebate scheme to enhance the existing scheme in Hong Kong and encourage cooling energy savings during the summer months. In the study, the per–area cooling energy consumption for the public housing sector during the summer months (May to October) is benchmarked using a 5–star rating system to the determine its incentive level on the proposed tariff list. Under the proposed scheme, 5–star households will get a higher rebate rate while those with a star only will not receive any rebate. For the same amount of energy reduced, the application example demonstrates that the proposed scheme can save money as much as two times more than the existing scheme.