Nanofluid is a suspension of liquid containing metal or non-metallic nanoparticles of typical size (1-100 nm) dispersed into the base liquid. Hybrid or composite nanofluids is considered an extension of research work for single nanofluids, which can be carried out through a combination of two or more different nanoparticles-either in mixed or dispersed composites in liquids. The objective of this study is to investigate the stability of tri-hybrid nanofluids suspended in Water-Ethylene Glycol (EG) mixture. The tri-hybrid nanofluids were prepared at a volume concentration of 0.05 to 0.3% using the two-step method. Three types of nanoparticles used namely Al2O3, TiO2 and SiO2, and dispersed in a base fluid of water/EG. The investigation on the stability of the hybrid nanofluids in the present study is conducted through UV-Vis, zetapotential, sedimentation and micrograph observation. The findings from the investigations on the visual stability of sedimentation show that the differences in concentration (0.05, 0.1, 0.2, 0.3%) have been low in day 14. It was found that 10 h sonication time is the most suitable period for sonication to obtain a stable suspension. Comparison of data concentration ratio to sedimentation for single, hybrid and tri-hybrid nanofluids presents tri-hybrid nanofluids remains stable with a concentration ratio of 80%. Zeta potential evaluation conducted for the tri-hybrid nanofluids obtained the value of 25.1 mV in the classification of good stability. It can be concluded that the tri-hybrid nanofluids were successfully prepared and achieved good stability.

In recent years, research has focused on enhancing the thermo-physical properties of a single component nanofluid. Therefore, hybrid or composite nanofluids have been developed to improve heat transfer performance. The thermo-physical properties of the Al2O3-TiO2-SiO2 nanoparticles suspended in a base of water (W) and ethylene glycol (EG) at constant volume ratio of 60:40 and different volume concentrations were investigated. The experiment was conducted for the volume concentrations of 0.05, 0.1, 0.2, and 0.3% of Al2O3-TiO2-SiO2 nanofluids at different temperatures of 30, 40, 50, 60, and 70 °C. Thermal conductivity and dynamic viscosity measurements were carried out at temperatures ranging from 30 to 70 °C by using KD2 Pro Thermal Properties Analyzer and Brookfield LVDV III Ultra Rheometer, respectively. The highest thermal conductivity for tri-hybrid nanofluids was obtained at 0.3% volume concentration, and the maximum enhancement was increased up to 9% higher than the base fluid (EG/W). Tri-hybrid nanofluids with a volume concentration of 0.05% gave the lowest effective thermal conductivity of 4.8 % at 70 °C temperature. Meanwhile, the dynamic viscosity of the tri-hybrid nanofluids was influenced by volume concentration and temperature. Furthermore, tri-hybrid nanofluids behaved as a Newtonian fluid for volume concentrations from 0.05 to 3.0%. The properties enhancement ratio (PER) estimated that the tri-hybrid nanofluids will aid in heat transfer for all samples in the present. The new correlations for thermal conductivity and dynamic viscosity of tri-hybrid nanofluids were developed with minimum deviation. As a conclusion, the combination of the enhancement in thermal conductivity and dynamic viscosity for tri-hybrid at 0.3% volume concentration was found the optimum condition with more advantage for heat transfer than other concentrations.

Kebutuhan akan listrik baik untuk kalangan industri, perkantoran, maupun masyarakat umum dan perorangan sangat meningkat. Tetapi, peningkatan kebutuhan listrik ini tidak diiringi oleh penambahan pasokan listrik. Berdasarkan permasalahan tersebut, energi surya dipilih sebagai energi alternatif untuk menghasilkan energi listrik. Alat yang digunakan disini adalah sel surya, karena dapat mengkonversikan langsung radiasi sinar matahari menjadi energi listrik (proses photovoltaic). Agar energi surya dapat digunakan pada malam hari, maka pada siang hari energi listrik yang dihasilkan disimpan terlebih dahulu ke baterai yang dikontrol oleh regulator. Keluaran regulator langsung dihubungkan dengan inverter dari arus DC ke AC. Hasil pengujian modul surya (photovoltaic) terlihat bahwa hasil daya keluaran rata-rata mencapai 38,24 Watt,dan arus yang didapatkan sebesar 2,49 A (Ampere). Hal ini dikarenakan photovoltaic saat mengikuti arah pergerakan matahari akan selalu memposisikan photovoltaic untuk tetap menghadap matahari sehingga tetap akan dapat menangkap pancaran matahari secara maksimal. [Title: Design Analysis of System Power Solar Cells Capacity of 50 Wp] The need for electricity is good for the industry, offices, and public and individuals are greatly increased. However, the increase in demand for electricity is not accompanied by the additional power supply. Based on these problems, chosen solar energy as an alternative energy to generate electric power. A tool that is used here is the solar cell because it can directly convert solar radiation into electrical energy (photovoltaic process). So that solar energy can be used at night, then during the day, the electrical energy generated is stored before a battery which is controlled by the regulator. Regulator output is directly connected to the inverter from the DC to AC. The test results of solar modules (photovoltaic) indicated that the results of the average power output reached 38.24 Watt, and the currents were 2.49 A. This is because the photovoltaic follows the direction of movement of the sun and always located at the photovoltaic to remain facing the sun. Therefore, it will still be able to capture the radiant sun to the fullest.

The use of nanoparticle coolant fluid in the car radiator increases the rate of heat transfer and facilitates the reduction of the overall radiator size. In this study, heat transfer characteristics of tri-hybrid nanofluids-based water/EG (60:40) were analyzed experimental and compared with water/EG (60:40). Four different nanofluids concentrations were prepared by adding 0.05 to 0.3 vol.% of tri-hybrid nanofluids dispersed a mixture of water/ethylene glycol (60:40). Experiments were carried out by varying the flow rate of coolant between 2 to 12 LPM for working temperature of 70 °C, the velocity of airflow remained at an average of 4 m/s, to understand the effect of coolant flow rate on heat transfer. The results showed that the thermal performance of tri-hybrid nanofluids in a water/EG (60:40) mixture has been investigated for volume concentrations of up to 0.3% and working temperature of 70 °C. The maximum enhancement of heat transfer coefficient for air side is observed up to 23.8% at 0.05% volume concentration meanwhile for coolant side is observed at 39.7% at 0.3% volume concentration. The pressure drop and pumping power have the same pattern which increasing in volume concentrations.