Batteryless Solar Refrigerator

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The Danish Technological Institute (DTI) and project partners, Greenpeace International, Vestfrost, Danfoss, PATH, GTZ, UNEP, UNICEF and WHO have developed a solar powered refrigerator. This refrigerator operates directly on solar PV panels, without battery or additional electronics, and is therefore suitable for locations where little maintenance and reliable operation is mandatory. Moreover this refrigerator is made from mass produced standard components, which results in a favorable cost as compared to other solar refrigerators. DTI assigned us a contract to conduct a field test of 3 solar powered refrigerators in India.

The objectives of this field test program are (i) to verify the performance under various climatic conditions (ii) to verify the performance with various applications (iii) to get feedback from users on advantages and disadvantages and (iv) to achieve detailed results for eventual adjustments in the prototype.

Performance tests have been conducted measuring and analyzing data of solar irradiance, temperature inside the refrigerator at different locations, PV Panel temperature, ambient temperature and current & voltage of power supplied from PV panels. DataHog with pyranometer and thermocouple was used to measure solar irradiance and PV panel temperature. TinyTalk logger loggers were used to record refrigerator cabinet and ambient temperature. RISH Multi SI 232 were used to measure voltage, current and door openings. Findings on performance and limitations were analyzed and necessary recommendations were made for improvement of design and configurations.

Solar PV based space heating using thermally insulated granite tiles:

A private company has developed a technology for space heating using thermally insulated granite tiles. We have tested three different types of heating panels provided by the company for evaluation of efficiency and optimization of solar PV arrays.

The objectives of the test are (i) to size the PV array that is optimally matched to the samples of granite heating tiles. (ii) to determine the power requirement to maintain the heating tiles within specified temperature boundaries and (iii) to define the thermal inertia of the heated tiles and appropriateness of PV panels as a power source.

Solar PV array sizing was done based on IV characteristics of the heating panels. The best PV size is selected based on maximum power point of the PV array and corresponding operating point of the heating panel. To achieve the best result, optimum series parallel combination of PV modules and heating panels need to be carefully chosen at particular solar radiation using an optimization tool.

The granite heating tiles were tested with different power inputs and at different room temperatures to observe their efficiency. While calculating efficiency, we have considered heat transferred towards the top surface i.e. granite side as useful heat and heat transferred towards the bottom of the heating panel as heat lost to the ground. No obstruction of insulation was provided at the bottom to prevent heat loss from that side of the panel. Recommendations have been made to the manufacturer based on analysis of the results and observations.

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