IPTEK, Journal of Engineering, Vol. 5, No. 1, 2019(eISSN: 2337-8530) 9 Experimental Study the Effect of Additional Flat Plate Reflector to Performance the Sinusoidal Solar Water Heater Dedy Ashari 1 , Djatmiko Ichsani 1 AbstractNew Renewable Energy is currently not fully utilized. Energy sourced from the sun is one of the most exploited energy sources today in several countries in the world, which in large scale has been used as a power plant. The solar collector is a heat exchange device that serves to convert solar radiation energy into a form of heat energy to heat a working fluid, such as water and air. Various methods have been undertaken to improve the performance of solar collectors, including using flat plate reflectors. Reflectors are used to reflect the diffused sunlight to focus on solar cells and ultimately increase the value of solar cell output power. Experimental studies in this study were conducted to see the performance of a solar collector sinusoidal with and without the addition of reflectors under varying discharge conditions. Variations of mass flow rate in this study were 18 and 20 liters/hour. The reflector angle on the solar collector is set at 40° on both sides of the reflector. From this study, the results for the efficiency of a solar collector with the addition of a reflector are the highest at 43,91% at a mass flow rate of 20 liters / hour. Keywords Solar Collector, Water Heater, Sinusoidal, Reflector, Intensity of Solar Radiation I. INTRODUCTION 1 lectricity is one of the main needed by humans around the world. At this time, the source of electrical energy is mostly derived from fossil energy such as petroleum and coal which is a type of non-renewable energy or energy source that can’t be renewed, which in the future will be exhausted. So the solution that can be used is to use other renewable energy sources or so-called renewable energy that comes from water, wind or sunlight. The solar collector is a heat exchange device that serves to convert solar radiation energy into a form of heat energy to heat a working fluid, such as water and air. Solar Water Heater (SWH) has proven to be an effective technology to convert solar energy into heat energy. Solar Water Heater (SWH) has been widely used around the world due to its economical and simple system [1]. The conversion efficiency of solar heat is around 70% when compared to the direct conversion of electricity from the sun which has an efficiency of only about 17% [2]. SWH can be classified into several types, including passive SWH and active SWH. In passive SWH, cold water in the SWH absorber tubes gets heated due to solar radiation and rises to the top and the cold water takes the place of hot water and the cycle continues until the temperature of the water equalized. Active SWH uses external source like pump for water circulation in the system [3]. Flat plate reflector in the solar collector serves to reflect solar radiation towards the collector, so that it can increase the amount of solar energy that can be received by the collector [4]. 1 Dedy Ashari and Djatmiko Ichsani are with Department of Mechanical Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, 60111, Indonesia. E-mail: dedyashari89@gmail.com; djatmiko@me.its.ac.id. [5] Theoretical analysis of research on solar collectors with flat plate reflectors has been done before. He predicts that solar radiation absorbed by collectors throughout the year is greatly influenced by the tilt angle of the collector and reflector. [6] Conducted a study on the effect of adding a V-reflector on a solar water heater (SWH), the results of his research showed that the addition of a V-reflector can improve the performance of the solar water heater. Research on determining the position of collector solar on the total heat energy produced by solar collectors is also done by [7]. The flat plate reflector is made of aluminum with the same dimensions as the dimensions of the flat plate solar collector. The solar collector is installed with an angle of β = 45˚. The results showed that the addition of a flat plate reflector at optimal position 45˚ collector solar can increase the amount of heat energy produced by solar collector around 35-44% in the summer period (June - September) compared to without using a reflector. [8] Conducted research on the addition of reflectors that can be adjusted to tilt angles on both the left and right sides of the solar water heater collector to improve efficiency. The reflector tilt angle is determined at 60˚ for the left side and 30˚ for the right side, can be seen in Figure 1. The slope of the solar collector is β = 45º, and the mass flow rate is 0.1 and 0.2 liters / minute. From the study, the maximum efficiency of the collector was recorded without using a reflector of around 51%, while the addition of the reflector efficiency was 61%. It can be seen that the addition of a reflector to a solar collector can increase efficiency by 10%. In this study the reflector is made of flat mirrors, using solar radiation reflections from the reflector is expected to increase heat reception in the absorber. This research will be focused on increasing the efficiency of heat transfer in E