Solar panels are susceptible to dust accumulation on their surface for long term operation. Scheduled cleaning work is thus important to maintain the efficiency and reliability of the solar panel for producing electricity. The paper presents a preliminary design of the cleaning mechanism for the solar panel surface using a semiautomatic wiper control system. A DC motor is utilized to power the wiper. The amount of water is sprayed over the solar panel surface, while the wiper is moving back and forth. The manual switch buttons are used to control the rotation direction of the DC motor. The experimental tests are conducted to obtain the solar panel performance, namely output voltage, output current, output power, and panel efficiency under clean and dusty conditions. The comparison of both conditions has been made to determine the cleaning effectiveness of the proposed prototype. The test results show that the wiper swept repetition of 10, 20, and 30 times delivers 57.0 percent, 79.1 percent, and 86.7 percent of the performance of the initial clean surface condition, respectively.

Freezer cooler (CF) is one of the cooling equipment for the storage needs of frozen food at low temperatures. CF is an indispensable tool for storing food and drinks to be durable. So, it is safe for consumption. Ice cream products, for example, are susceptible to temperature variations and are easily damaged during storage. Temperature fluctuations can cause dramatic adverse effects on the quality of frozen food, ice re-crystallization temperature in ice cream, and this can create substantial economic losses, and degrade the quality of frozen food. Maintaining a stable temperature in frozen food storage is very important. Current CF cooling technology consumes large amounts of electricity. It is essential to develop research on CF cooling engines that are energy efficient and environmentally friendly. Current technology makes it possible to add PCM to the walls of the cooling machine. During the phase change process, the temperature remains constant, and a large amount of energy can be stored or released. Refrigeration technology testing with PCM integrated on the evaporator has been carried out in this study and can reduce energy consumption by 4 percentage, increase COP by 6 percentage.

Grid-tied photovoltaic (PV) installations equipped with net metering devices become significant interests among villa owners in urban areas. Such devices can help to make sure of exporting excess power to the grid as well as to favor the self-consumption ratio. The self-consumption means that the owners directly utilize PV power production. This paper is aimed at simulating the energy and economic performances of a 3.24 kWp grid-tied PV system applied in the villa. The case study is a private villa located at Tibubeneng, Bali Province, Indonesia. The Sunny Design Web simulation tool is used for the PV system assessment. The simulation results reveal that the energy yield of the PV system is 4, 653 kWh/year, out of which 300 kWh/year is feeding to the grid. The self-consumption and self-sufficiency ratios are 93.5 percent and 35.6 percent, respectively. The PV system also delivers a performance ratio of 81.4 percent, the specific energy yield of 1, 436 kWh/kWp, and the payback period of 9.3 years.