Applied Mechanics and Materials Vol. 839

Abstract: The use of fossil energy in Indonesia shown an increasing trend in all sectors every year^[1]. Petroleum is still ranked the highest, ie 51.66%. Natural gas occupying the second level, ie 28.57%. The rest of the energy is supplied by 15.34% oil and 4.43% renewable energy. Besides this, the dominance of fossil fuel use give a major impact on air quality^[2]. Emissions from fossil fuel burning add 6.3 GtC/year (compared to a stock of fossil fuels of 16,000 Gt C) while another 2.3 Gt C/year is reabsorbed into the ocean^[3]. Therefore, it is necessary to develop the use of renewable resources to generate environmentally friendly electricity. One of the energy resource that can developed is ocean current energy. In 2009 in the Strait of Nusa Penida has been conducted a ocean current pilot project that have been successfully (technically) obtained a "proven design”. Energy utilization of ocean current in the Nusa Penida Strait is merely for lighting public facilities. The presence of power plant have given light to 25 street lamps that installed in Toyopakeh village. This study aimed to (1) identify benefit which Toyopakeh village community perceived, (2) analyze the opportunity and estimate the value of willingness to pay (WTP) community of Toyopakeh village for management of power plant. The economic and sosiocultural benefit perceived by Toyopakeh village community in the night are increasing works effectively for seaweed strappers, stalls can opened over night, easier to moored jukung and speedboat, ship monitoring, load and unloading, fishing, and ashes disposal. Citizens with high or low income had similar opportunity readiness. Citizens with high education had opportunity WTP 1.291 point more than not ready to pay. Based on Turnbull estimator distribution, the mean WTP value was at 7 894.695 IDR (0.56 US $) and 10 641.891 (0.76 US $) range.

Abstract: In a deregulated electricity market the generating and distribution companies enter into various levels of contracts for primary energy transaction. In real time, the losses due to these contracts must be economically supplied by Independent system operators (ISOs). Graph Theory is employed in many fields of engineering especially in transmission loss allocation problem to formulate a given network’s behavior. Graph theory based loss allocation method gives satisfactory results over the other existing methods in terms of technical suitability and various transactions. Loop based representation approach is used for the network formulation. Compared to other loss allocation methods, this method distributes losses to the different participants in a lucid manner. In this paper, a comparison of graph theory based loss allocation method over the other existing methods like proportional sharing, Z bus and modified Z bus loss allocation is made. The results are shown for a sample 4 bus system and IEEE14 bus system. The simulation is carried out using MATLAB (R 2014a).

Abstract: The research was performed on thermal energy storage prototype in Thailand. Concrete was used as the solid media sensible heat material in order to fulfill local material utilization which is easy to handle and low cost. Saturated steam was used for heat transfer fluid. The thermal energy storage prototype was composed of pipes embedded in a concrete storage block. The embedded pipes were used for transporting and distributing the heat transfer medium while sustaining the pressure. The heat exchanger was composed of 16 pipes with an inner diameter of 12 mm and wall thickness of 7 mm. They were distributed in a square arrangement of 4 by 4 pipes with a separation of 80 mm. The storage prototype had the dimensions of 0.5 x 0.5 x 4 m. The charging temperature was maintained at 180°C with the flow rates of 0.009, 0.0012 and 0.014 kg/s whereas the inlet temperature of the discharge was maintained at 110°C. The performance evaluation of a thermal energy storage prototype was investigated in the part of charging/discharging. The experiment found that the increase or decrease in storage temperature depends on the heat transfer fluid temperature, flow rates, and initial temperature. The energy efficiency of the thermal energy storage prototype at the flow rate of 0.012 kg/s was the best because it dramatically increased and gave 41% of energy efficiency in the first 45 minutes after which it continued to rise yet only gradually. Over 180 minutes of operation time, the energy efficiency at this flow rate was 53% and the exergy efficiency was 38%.

Abstract: Stand-alone PV system has been originally developed to feed solar energy produced by PV modules into the system by using solar charger controller at DC bus called “DC Coupling” for long time. In Late 1990 there is a new concept of feeding solar energy to the PV system at AC bus called “AC Coupling”. The AC coupling system uses grid connected inverter to convert energy produced by PV modules and synchronize output to AC distribution line. In mini grid system the common AC output of Bi-directional inverters or diesel generators performs as grid forming device to supply distribution line. Since 1990 there are stand-alone PV systems designed by using DC coupling or AC coupling which each type of PV coupling system highlight their advantage over the other. The work in this document presents a comparison of the efficiency of DC coupling and AC coupling PV system design in a hybrid mini-grid and finally proposes the alternative PV system design by using the “Dual DC and AC coupling” PV system in a hybrid mini-grid design. The HOMER Pro micro-grid analysis tool which can simulate DC and AC coupling PV system is used to compare leverage cost of energy (LCOE) of different type of PV hybrid mini-grid system. The simulation software which can do performance analyzing metric according to IEC 61724 and IEA-PVPS T2 is created in this study in order to simulate system operation and performance using DC, AC and dual DC and AC coupling PV system. The conclusion can clearly identify the best PV system in hybrid mini-grid in terms of LCOE and system performance.

Abstract: To estimate global solar radiation from easy available weather forecast data (sky condition), Markov model is used for this estimation. The five-year (1996-2000) global radiation data that are taken at an hour intervals from Nakhon Pathom station, Thailand (latitude 13.81ºN and longitude 100.04ºE) are used to construct the Markov transition matrices. The global radiation sequences in 2000 will be generated by based on the characteristic probability of moving global radiation values which were observed from the obtained data during 1996-1999. The autocorrelation function is used for checking the order of probability of moving obtained data. In this study, the five first and five second-order Markov transition matrices (MTMs), which are selected from the autocorrelation functions, are constructed, each MTMs will be used for generating global radiation values in each day with different sky conditions (clear, partly cloudy, mostly cloudy, cloudy and overcast). From the results of comparison between the statistical characteristics of observed and two synthetic generated data, global radiation data behavior slightly improved by the second order Markov model.

Abstract: A Photovoltaic rooftop system is being grown up for producing electricity in Thailand. The technical study of PV rooftop system is required especially in term of power quality impact from PV rooftop system to the grid system. The aim of this paper is to construct the simulation models of a micro grid PV rooftop system by using the simulation software PSCAD. PSCAD has an advantage that the software provides a complete model of the PV rooftop system in an electromagnetic transient software environment. The modules of study include PV array, three-phase inverter, LC filter, transformer, load, and distribution network. The constructed model is simulated under the Provincial Electricity Authority (PEA) regulations.

Abstract: Biomass is an important renewable energy resource, which is used to replace the petroleum to produce chemicals. Glucose is a monomer of cellulose, which is the main component of biomass. In this work, conversions of glucose to value-added chemical by a simple method have been reported. TiO₂ photocatalysts were fabricated by sol-microwave method. Value-added chemical production was successfully carried out via photocatalytic conversion of glucose with TiO₂ photocatalysts. Arabinose, xylitol, gluconic acid, and formic acid were produced with photocatalytic reaction of TiO₂ under UVA irradiation. The value-added products (gluconic acid, arabinose, and xylitol) can generally be further used as building blocks for biorefinery production, pharmaceutical production, and food industry. In the conventional sol-microwave method, the agglomeration of fabricated TiO₂ particle was a limitation of photocatalytic activity. Therefore, the modification of TiO₂ fabrication by use of zeolite as a TiO₂ support was applied to increase efficiency of photocatalytic conversion of glucose and its selectivity. The effect of TiO₂ dosage on zeolite (TiO₂/zeolite) on photocatalytic activity and yield of products was monitored. The results from scanning electron microscopy (SEM) images indicated that zeolite supporter reduced agglomeration of spherical TiO₂ particles. The well distribution of TiO₂ particles on surface of zeolite particles could be observed in 15%TiO₂/zeolite. It was found that the highest photocatalytic conversion of glucose (77.3%) was obtained from the use of 15%TiO₂/zeolite as photocatalyst. The yields of gluconic acid, arabinose, xylitol, and formic acid were 8.6, 26.0, 3.7, and 33.89%, respectively.

Abstract: This article presents the availability of 4 large scale grid connected photovoltaic (PV) power plants that located in Petchaboon, Nakhon Sawan, and Chai Nat province of Thailand. These power plant size are 4.5 MW and 6.5 MW. In addition, they are constructed with the same platform, component, and commercial operation date (COD) in the same year. The data were collected during 1^st August 2012 to 31^st October 2014. The study result found that availability of these power plant is over 97 % every year except Nakhon Sawan 1 plant in the first year. The internal unavailability trend is quickly reduce while external unavailability is randomly fluctuation.

Abstract: Any power system network is subjected to disturbances at any time and place. It is considered as one of the most stochastic system ever seen by the human beings. To enhance the power system reliability, System Protection Scheme (SPS) is an effective tool for utilizing the power grid during rare contingencies. This method is often employed as secondary protection schemes. SPS is also termed as Special Protection Scheme. SPS is referred with different names by different users such as IEEE as System Integrity Protection Scheme (SIPS), Bonneville Power Administration (BPA) as Remedial Action Scheme (RAS) and WECC and others as SPS. In India, only in late 90s, the concept of SPS was introduced to solve the above problem. In Indian power grid different SPS has been designed and implemented successfully. This paper presents a complete knowledge, need , general structure, characteristics and a brief description of the major SPS employed in various Indian Power grids. Post - commissioning performance of these SPS has also been analyzed briefly. Finally, highlights of major issues involved with the employment of SPS in the Indian scenario.

Abstract: A micro static var compensator (µSVC) is introduced in this work to prevent the over-voltage problems in radial distribution networks with high number of rooftop photovoltaic (PV) connections. The µSVC is aimed to use in the PV system that has the fixed-power factor inverter, which cannot provide the active voltage controllability. The µSVC is a small shunt compensator installed parallel with the PV system and providing the automatic reactive power support to deal with the dynamic voltage variations at the point of common coupling. Two reactive power control methods, Q(P) and Q(V), can be employed into each µSVC depending on the location of PV systems. Moreover, the coordinated reactive power control among µSVCs, without communication system requirement, is presented for enhancing the Volt-Var controllability to the group of PV systems located in the same feeder. The dynamic voltage control performances are examined on simulation in DIgSILENT PowerFactory software. The results showed that the proposed control method can mitigate the rise of voltage level sufficiently.