Abstract: This paper presents an experimental test along with procedures to investigate the effect of dust influences on the photovoltaic efficiency under the prevailing meteorological conditions in tropical climates. The reduction of the transmittance of solar radiation and electrical power generation due to the dust on a PV module has been measured. According to the observed results during a 30-day period, the dust accumulation reduces the glass cover transmittance from 89.8% to 74.9% and also results in the decrement of conversion efficiency from 4.78% to 4.07%. The comparisons between the experimental results and the simulated results used the same meteorological data as the experiment show that the predicted results simulated by the model agree satisfactorily with those observed from the experiments.
Keywords: Photovoltaic Module, Conversion Efficiency, Dust, Transmittance.
Wanchat Sawaengsak, Passanan Assavarak and Shabbir H. Gheewala*
Abstract: This study aims to identify the suitable social and socio-economic indicators for biofuel systems in Thailand via a literature review also considering criteria for selecting sustainability indicators developed by the Society of Environmental Toxicology and Chemistry/United Nations Environment Program Code of Practice. The concept of life cycle thinking is followed as part these investigations, including, feedstock production, feedstock processing, conversion to biofuel and end use including intermediate transportation. The study was conducted by defining the key stakeholders involved in each unit process of the biofuel systems in Thailand including farmers, suppliers, workers, local community members and consumers. The results of suitable social and socio-economic indicators were aggregated into 9 areas of concern including farmers: wage paid, land rights; workers: working condition, health and safety, and discrimination; local community: local employment, and health and safety; suppliers: fair competition; consumers: food security. However, further investigations should be performed, especially field surveys, including stakeholder interviews, documenting the quality of data and direct site observations to improve data reliability and robustness.
Keywords: Social indicator, Socio-economic indicator, Biofuel, Sustainability.
Nattapong Puttanapong, Suwichak Wachirarangsrikul, Wisanu Phonpho and Varoon Raksakulkarn
Sakhon Ratchahat*, Khalid Al-Ali, Satoshi Kodama, Tawatchai Charinpanitkul, Hidetoshi Sekiguchi and Wiwut Tanthapanichakoon
Abstract: Pyrolysis and CO2 gasification were experimentally investigated by direct dispersion of cellulose powder in a high-temperature molten salt (MS) system. Ni/Al2O3 catalyst powder was suspended in MS (CLMS) to improve the production rate and yield of syngas in both cellulose pyrolysis and char gasification. A combined pyrolysis-CO2 gasification process (CPG) is known to provide CO-rich syngas which is primarily attributable to H2 consumption during the reverse water gas shift reaction (RWGS). In this study, a separated pyrolysis-CO2 gasification process (SPG) was proposed to produce H2-rich syngas. Four conceptual process designs, namely, SPG in MS, SPG in CLMS, CPG in MS, and CPG in CLMS were examined. As an idealized operating condition, the present design basis assumed that all of the pyrolysis-generated CO2 by-product could essentially be consumed in the char gasification step of the CPG. Based on a design basis of 100 kmol/h cellulose feed, the CPG produced 593 kmol/h of syngas in MS and 485 kmol/h in CLMS with an overall H2:CO mole ratio of 0.21 and 0.14, respectively. In contrast, the corresponding values of the SPG were 770 kmol/h in MS and 1,137 kmol/h in CLMS with ratios of 0.58 and 0.76, respectively. In addition, the SPG could reduce the residual char to 33 kmol/h in MS and to 30 kmol/h in CLMS from 239 kmol/h and 268 kmol/h of its CPG counterparts. The required total reactor volumes of the SPG were approximately half of the corresponding CPG. Similarly, the total heat consumption required for the SPG was also slightly less. When the present results were compared to our previous work which assumed from the actual experimental condition that the CO2 required for char gasification was fed stoichiometrically equal to the moles of the residual char, the present corresponding values of mass flow rate of salt, heat consumption rate and syngas/heat input were found to decrease 1% for the SPG and 7% for the CPG mainly due to savings in heating up the smaller CO2 feed. In conclusion, the SPG in CLMS embodied the most effective system design in terms of the quantity and quality of the syngas, the reduced residual char as well as the effective utilization of concentrated solar energy.
Keywords: Syngas; Pyrolysis; CO2 gasification; Ni/Al2O3; Conceptual process design.
Mega Octaviani, Kasemsan Manomaiphiboon* and Thayukorn Prabamroong
Abstract: This study deals with characterization of near-surface wind shear coefficient or exponent using multiple-height wind data observed in the year 2006 at 23 towers located across Thailand. The characteristics of main interest are diurnal and seasonal variations and dependence on atmospheric stability and surface roughness. The key results obtained from the study are: At most towers, wind shear coefficient is relatively large during the night and becomes relatively small in the afternoon, which is typically found or reported in the literature. However, for some towers, the pattern is reverse, which may be partly attributed to complex wind fields influenced by local topography. A set of wind shear coefficient values aggregated from all tower data by type of terrain (open and non-open/rough) and Pasquil-Gifford stability class were analyzed and given, which can be used as a reference for applications in Thailand. It is also evident that the one-seventh power law often used in wind-energy application to extrapolate near-surface wind speed from one height to another is not suitable and wind-energy workers should thus avoid applying it.
Keywords: Wind shear, power law, surface roughness, atmospheric stability, meteorology, wind energy.