Experimental Investigation of a locally fabricated low-cost solar parabolic trough in Thailand

The current political tensions resulting in sharp increases in oil and gas prices, has further highlighted the need for energy independence by nations. Renewable energy technologies are one way of achieving this, so countries need to focus on developing indigenous technology to harness renewable energy. This study focuses on developing a solar parabolic trough collector for Thailand. Solar energy is a renewable energy source that can be used indefinitely. It will also play an increasingly important role in the future energy structure. Solar Parabolic Trough (SPT) is a device that has a curved shape of cylindrical parabolic. It consists of a shiny surface to reflect sun radiations towards the focal point. There are several factors that can affect the performance of the solar parabolic trough such as the accuracy of the sun model, the reflection of the sun radiation, fluid flow, the heat transfer to fluid and so on. The latter absorbs the incoming radiations and transforms them into thermal energy. This study experimentally investigates the thermal performance of a Solar Parabolic Trough collector with a sun tracking system designed for the Thai contexts. A set of three Solar Parabolic Trough (SPT) were designed and built in Srinakharinwirot University (SWU). Each had a focal length of 300 mm; length 5.1 m. Water was used as the working fluid circulated through a 60 litres water tank. Experiments were run at five (5) different flow rates of 0.5, 1, 2, 3 and 4 litres per minute. Located at the parabolic troughs focal point is the vacuum tube collector which consists of a 10 mm smooth copper tube, enclosed in 47 mm diameter sealed glass tube. Type K Thermocouples were used to measure the temperatures at different points in the fluid and recorded using a data logger, and a sun tracking system was used for controlling stepping motors in the solar parabolic trough. Experiments were run over 5 days between 10:00 – 16:00 Nakhon-Nayok city, Thailand. Solar radiation during the period ranged between 462.60 – 1021.59 W/m2 (average 800.86 W/m2 ) and ambient temperature ranged from 36.54 – 39.17 °C (average 38.48 °C). The results showed that the water flow rate had an inverse relationship with the efficiency of the solar parabolic trough. The flow rate of 0.5 liters per minute resulted in the highest temperature of 56.70 °C and the maximum total rate of heat transfer was 955.65 W. The maximum efficiency was observed to be about 12%. This low efficiency is similar to what has been observed in similar studies. Overall, the study shows promising performance results for the deployment of locally made solar parabolic trough collector in Thailand.