Chuleeporn Sriyam, Amnat Chidthaisong*, Kazuyuki Yagi, Sirintornthep Towprayoon and Sudarut Tripetchkul

Abstract: This study aimed to determine the rates of N₂O and CO₂ production under different soil temperature and moisture conditions. Soil samples were collected from the 46-years long-term fertilizer experiment plots in Lopburi province. Three treatments were included in the present study; control or no fertilizer (NF), chemical fertilizer application (CF) and organic fertilizer application (OM). The soils were incubated at 25°C, 30°C, and 35°C under moisture content of 60 and 80% water-filled pore space (%WFPS) for 14 days. Long term fertilizer experiment (46 years) revealed that the application of cow or chicken manure has increased soil carbon stock (SOC) by 5-7 MgC ha-1 compared to that of no fertilizer and chemical fertilizer application. The N₂O production rate from all treatments was increased 2-9 times under 60% WFPS and 5-18 times under 80% WFPS when the temperature was increased from 25° to 30°C, but was decreased when the temperature was increased from 30° to 35°C, except the CF which was increased. The OM had highest N₂O and CO₂ at any temperatures investigated. Only the temperature above 30°C that the effects of moisture on N₂O production was observed. The mean value of N₂O production in OM under 60% WFPS and 80% WFPS differed only under 25°C. On the other hand, CO₂ production rates was enhanced 1-2 times along with increasing temperature and moisture. These results indicate that the longterm fertilizer application has significantly changed the production potential of N₂O and CO₂, and so their sensitivities to temperature and moisture changes.

Keywords: Long-term experiment, N₂O and CO₂ production, soil temperature, soil moisture.

Damson Daniel Kadete, Pipat Chaiwiwatworakul* and Surapong Chirarattananon

Abstract: This paper presents an investigation of the daylighting from external multiple shading slats integrated with photovoltaics (PV). Experiments were carried out at an outdoor chamber with a south-facing window. Based on the measured results using various sensors, the daylighting characteristics were analyzed for an office environment under varying tropical sky conditions. Relationships of the exterior daylight illuminance and the interior daylight distribution could be empirically formulated, and they were used to determine the required artificial light from electric lamps to supplement the transmitted daylight from the window. In the assessment of the daylighting potential of the PV shading slats, a monthly adjustment scheme of the slat angle to fully intercept the direct sunlight from the south window was proposed together with the task-ambient lighting concept. By using our experimental room as the demonstration case, the analysis showed that the daylighting of the PV slat system could reduce the lighting energy consumption by 80% compared to the typical office case designed with the uniform lighting concept. The generated solar energy from the PV array on the slat surface was estimated to be sufficient for the lighting by the direct-current LED lamps. However, battery storage was required due to the time mismatch between the solar power generation and the required electricity for supplement lighting.

Keywords: Daylighting, dimmable lighting, PV slats, tropical climate, workplane illuminance.

Asama Tavornpongstid, Sudarut Tripetchkul*, Sirintornthep Towprayoon, Chart Chiemchaisri and Komsilp Wangyao