20 Journal of Advanced Thermal Science Research, 2017, 4, 20-30 E-ISSN: 2409-5826/17 © 2017 Avanti Publishers Performance Evaluation of a Modified DC Compressor Powered by Solar Energy Orhan Ekren * Ege University, Solar Energy Institute, Bornova, Izmir 35100, Turkey Abstract: In this study, a modified direct current compressor (MDC) is tested experimentally. The experimental study is conducted in order to observe the performance of a solar energy powered MDC. Then, the performance of this MDC is compared with brand new direct current compressors (BNDC) in the market. The experimental setup has a mini fridge with 50 liters capacity, a photovoltaic panel, a battery, a charge regulator and measurement equipments. Also, a pyranometer is used to define solar radiation on the photovoltaic panel. Experiments are conducted for various cabinet loads such as no storage items, low, nominal and over load at steady state condition. Keywords: Photovoltaic, solar energy, DC compressor, energy analysis, mini fridge, solar radiation. 1.INTRODUCTION Since HVAC&R systems are one of the most common used equipments and the high energy consumed equipments, decreasing energy usage and improving efficiency is important in these systems. This may help to decrease the expenses as well as to create environmental friendly systems in the worldwide. Mostly, energy savings in refrigeration systems are realized via optimum working conditions by using control techniques. Although these methods provide savings, they may not provide environmental friendly solution. Therefore, environmental friendly systems should be developed. Direct current (DC) compressor usage instead of alternative current (AC) provides opportunity using renewable energy sources also may help energy savings in refrigeration systems. Since DC applications require low voltage and direct current supply such as 12-24 volts. Small refrigerator usage is very common at many vehicles and domestic requirements. Using a DC compressor in a small refrigeration system provides a big opportunity to supply the energy by renewable energy technologies such as solar or hybrid of renewable sources because of their low power requirement. Since small refrigerator usage is very common, decreasing energy usage and improving efficiency on these systems may have big potential of savings. Some investigations have been conducted concerned with the renewable energy assisted refrigeration systems in the literature. These studies can be classified as analysis of AC compressor powered by solar energy via inverter and analysis of *Address correspondence to this author at the Ege University Solar Energy Institute 35100 Bornova, Izmir, Turkey; Tel: +90 232 311 5011; E-mail:orhanekren@gmail.com DC compressor powered by solar energy. Ewert et al. [1] studied refrigeration systems supplied by batteries and solar energy. They investigated three different cooling technologies such as free piston stirling, thermoelectric and vapor compression with DC compressor in the same vacuum insulated cabinet which is 365 liters. Also phase change material is used in the cabinet for thermal energy storage. In the experimental study, coefficient of performance (COP) of three systems is compared at steady state conditions. Results showed that COP is 0.04, 0.14 and around 1 for the thermoelectric solar refrigerator, stirling cooler and vapor compression cycle, respectively. Kattakayam and Srinivasan [2] is investigated AC operated domestic refrigerator powered by solar energy with a battery bank and an inverter for vaccine storage. This paper presents cool- down, warm-up and steady state performance of domestic refrigerator which has an internal volume of 165 liters, 100 W cooling capacity and uses CFC-12 refrigerant. According to the results of conducted experiments this kind of refrigerators could be used to improve the energy efficiency of domestic refrigerators. Also, performance can be improved by switching cabinet with vacuum insulated panels since heat leak contributes maximum to the cooling capacity. However, vaccine storage near wall of the door should be avoided. Cherif and Dhouib[3] presented performances, simulation responses and dynamic behavior of a solar energy powered refrigeration plant using latent storage at several climatic conditions and under load disturbances. They used a new storage strategy which allows to evaluate solar energy system reliability and to compare its performance with classic battery storage system. According to them, efficiency of the system and its performance decrease relatively with solar radiation disturbance because solar energy system requires good climatic conditions to reach the