Abstract

The uncertainty of distributed photovoltaic (PV) output brings difficulties to reactive power optimization of power system. A robust reactive power optimization model for power system considering the uncertain output of PV is proposed. The probabilistic model of PV output is used to solve the problem that the robust optimization solution is too conservative. The effectiveness of the proposed model is verified by an example.

Abstract

So far, the role of fossil fuels in future energy systems is still uncertain. To obtain a deeper understanding of how conversion technologies for fossil fuels act in multi-energy systems (MES), we extended our mixed integer linear programming (MILP) modeling framework for MES, first introduced by Gabrielli et al. [1], by adding gas turbines. This work presents the modeling approach for said gas turbines, focusing on the linear description of the efficiency’s dependency on load and ambient temperature. Furthermore, the model considers the possibility of selecting either natural gas or hydrogen as fuel, which affects the efficiency as well. A series of simple, proof-of-concept simulations were conducted to show the functionality of the model.

Abstract

Utilizing biodiesel from non—edible resources replacing diesel in power generation sector would reduce significant amount of carbon footprint. Biodiesel has lower carbon monoxide (CO) and carbon dioxide (CO2) providing large environmental benefits. This paper aims to study economic feasibility of applying Callophyllum Innophyllum (CI) biodiesel in power generation sector replacing diesel by varying economic factors. Although CI has advantages in technical aspects high production cost due to limited supply still is a disadvantage to CI biodiesel commercialization. A techno-economic assessment for biodiesel production is studied from feedstock acquisition till biodiesel consumption by analyzing its payback period and internal rate of return (IRR). The result shows that CI biodiesel is a feasible option considering influence of selling price, tax incentives as well glycerol selling price.

Abstract

Linear equation solver of real-time simulators for active distribution networks (ADNs) requires significant computation power. Field programmable gate array (FPGA) has many merits such as highly parallel hardware structure and programmable characteristics, which shows great potential for the real-time solving of linear equations. Considering the sparsity of the linear equation, a parallel solver is designed in this paper based on block triangular form (BTF) matrix block algorithm. The design of off-line processing on host PC and online calculation on FPGA are proposed in detail. Simulation results are compared with PSCAD/EMTDC to validate the correctness and effectiveness of the parallel solver design.

Abstract

In this study, crude Calophyllum inophyllum oil was used as the feedstock for biodiesel production. This feedstock contain high acid value of 56.3 mg KOH/g (28wt%) which is not favorable for direct conversion to biodiesel by transesterification. Therefore, this paper emphasizes the study on the pre-treatment process of degumming and acid catalyst esterification in order to reduce the high free fatty acid for successful transesterification. Single parameter study was conducted to identify the best acid with best concentration to efficiently esterify the degummed Calophyllum inophyllum oil with highest FFA conversion. Among phosphoric acid, hydrochloric acid, and sulphuric acid, 3.0M concentration of sulphuric acid was found to be the best condition for the esterification reaction providing 87.46% FFA conversion.

Abstract

To characterize the operation risk of wind power, the concept of wind power fluctuation costs is proposed, the environmental benefits of wind power integration are calculated from the perspective of wind power, which can reflect the environmental benefits of wind power more clearly. An improved economic dispatch model is proposed based on the comprehensive power generation costs calculated by the operating costs of thermal power units, wind power fluctuation costs and environmental benefits. The planned output of thermal and wind power is taken as the decision variables and solved by particle swarm optimization, and the economic change law of wind power integration is explored. The effectiveness and practicability of the proposed model are verified by IEEE 39-bus, 118-bus system.

Abstract

A present experimental study demonstrates the visual characteristics of the liquid-solid interface during the melting process in the Latent Heat Thermal Energy Storage System (LHTES) system. The instantaneous morphology of liquid-solid interface and temperature are directly obtained at the different locations in the enclosure when heated at an isothermal temperature condition. The visualization of the phase front and temperature field shows the significance of fins to alleviate the melting phenomenon by the formation of thermal plumes above the top surface of the fins. The role of natural convective transport as a governing mechanism for the phase change process in the partial assisted enclosure is also discussed.

Abstract

This paper presented an overview of the passive strategies for ventilation and air-conditioning energy saving in underground metro stations. The strategies were relevant to building envelopes, piston effect and natural cold sources. This review found that the building envelopes had made minimal contribution to the research literature and might not be applicable to the underground stations. The piston effect was the most popular passive strategy in research community for its great energy saving potential. The ground cooling strategy was another promising option for air-conditioning energy saving but it was often overlooked due to its high R&D costs. The authors hope that this study can promote the adoption of different passive strategies for the ventilation and air-conditioning energy conservation in underground metro station buildings.

Abstract

Hollow structured HZSM-5 was synthesized by posttreatment to introduce the meso-/microporous system. This resulted in the enhancement of the performance for catalytic fast pyrolysis of pine for aromatic products. Compared with traditional HZSM-5 catalyst, the hollow HZSM-5 catalyst exhibited enhanced the mass transfer ability, leading to higher selectivity of aromatics such as benzene, toluene, ethylbenzene, xylene, and naphthalene (58%). The intrinsic mechanism into the enhanced performance was further elucidated by multi-techniques such as HAADF-STEM, TGA-MS, TPD, Py-IR and NMR. This work provides a potential approach for directional production of woody biomass powder.

Abstract

Hybrid electric aircraft are developed to reduce emission and save energy. However, the thermal efficiency of turbo-electric aircraft and the endurance of battery-electric aircraft are both limited, respectively. Aircraft powered by fuel cells can achieve long endurance, low emission, and fuel consumption reduction. Solid oxide fuel cell hybrid electric jet engines without turbines for unmanned aerial vehicles was proposed in our previous work in which compressors are powered by fuel cells instead of the turbines. The hybrid electric jet engine combining the merits of a turboelectric engine and a fuel cell powered engine. To avoid component malfunctions and engine performance deterioration, determination of safe operation zone is necessary.
In this study, the performance analysis model of the hybrid electric jet engine is built and the main conclusions are as follows. The off-design performance of the hybrid electric jet engine is achieved by adjusting the mass flow of fuel injected into the reformer. The safe operating zone of the hybrid engine is not restricted by turbine inlet temperature. Under low fuel flow and low air flow, too low reforming temperature zones or too low SOFC open voltage zones exist. Additionally, the unbalanced energy zone exists under high fuel flow and low air flow. The power produced by the SOFC is over the one consumed by the compressor. In the safe zone, the hybrid engine has a characteristic of high specific thrust (837.6 N/kg.s-1 ) and high thermal efficiency (70.43%) with high rotational speed, vice versa.