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This study developed a grid-connected biogas power generation system for a rural community using a 3-phase 2.2 kW squirrel-cage induction machine as the self-excited induction generator. The generator was driven by a 196 cc single-cylinder spark-ignition engine fueled by biogas. We developed a back-to-back converter that consists of a 3-phase PWM rectifier as the generator-side converter and a single-phase LCL-filtered grid-connected inverter. The generator-side converter transferred the active power to the grid-side converter and supplied the reactive power control back to the generator. The notch filter-based bus voltage control on the generator side mitigated the inter-harmonics in the generator current. The injected grid current complied with the IEEE 1547 standard because of the multi-frequency unbalanced synchronous reference frame control. The proposed system was validated with biogas produced from pig manure at a pig farm in central Thailand, which found a maximum output of 1.2 kW with a thermal system efficiency of 10.7%. The proposed system was scheduled to operate at 1.2 kW for 8 h per day with a levelized cost of 0.07 US$/kWh, 42% cheaper than the retail electricity price, and a payback period of 2.76 years. The proposed system is suitable for a farm with a minimum of 34 pigs.

Abstract This study investigates the influence of Ni–Al coating thickness on the spectral selectivity and thermal performance of a parabolic trough collector (PTC). Three thicknesses of Ni–Al coating for use as solar absorber material were successfully prepared on the outer surface of a stainless steel 316L (SS) tube by flame spray. The phase, morphology, and reflectance (R) of the Ni–Al coatings were characterized using several techniques. The PTC and solar receiver tube were specially designed and constructed for observing the collector thermal performance by following ASHRAE 93-1986. Looking at the results, the actual average thicknesses of the three Ni–Al coatings turn out to be 195, 215, and 299 μm. The morphology and chemical composition of all three thicknesses are similar. The chemical composition in the cross-sectional view exhibits non-uniform distribution. The three thicknesses of the coating are composed of NiO and Al2O3 phases, which also corresponded to the results of SEM–EDX mapping. The differences in a solar absorptance (α) of the three thicknesses of Ni–Al coating are not statistically significant, with an average α value of 0.74–0.75. However, there are differences in thermal efficiency of the PTC depending on the thickness of the Ni–Al coating. Of the three samples, the thickest one (299 µm) demonstrates the highest ability to convert solar radiation into thermal energy.

The purpose of this study is to develop a thermoelectric egg incubator (TEI) integrated with a thermal energy storage (TES) system, using electricity from photovoltaic (PV) cells in order to operate without on-grid electricity. The TEI was constructed with the same dimensions as a commercial egg incubator (CEI), which was made to the required dimensions for hatching 24 eggs per period of 21 days. The TEI was designed with 2 operating modes of heat sources: a thermoelectric (TE) module used for daytime operation and a TES containing phasechange materials (PCM) which supplied heat to the TEI for nighttime operation. The PV panels were designed to be the primary energy source for generating 360 W of electricity, which was supplied to heat sources of TEI according to the energy load for providing fertile chicken eggs (24 eggs/hatching). The incubating temperature and relative humidity (RH) inside the TEI-TES were controlled under optimum environmental conditions for hatching (36-39°C and 60-80% RH) to stimulate embryonic growth. As a result, the TEI-TES achieved and maintained an optimum incubating temperature in the range of 36.7-38.8°C and the correct RH of 66±0.2 % in the warm weather of Thailand over the incubating period of 21 days. The TEI-TES was able to maintain optimum environmental conditions for chicken-egg hatching, and its performance was comparable to that of the CEI. The working mechanisms of the TE module and TES are also discussed. The results show that the TEI-TES with PV panels as the primary energy source is suitable for use in remote areas which have no on-grid electricity supply. [ABSTRACT FROM AUTHOR]