Researchers in China Develop a PV-driven AC Using Ice Thermal Storage

Scientists in China from the Yunnan Normal University and the Jiaxing University have built a PV-powered air conditioner that uses ice thermal storage rather than batteries to store power. The design of the air conditioner, directly driven by distributed solar PV, was studied, and an MPPT controller was designed to effectively utilize solar energy. A variable speed compressor was found suited for PV driven cooling.

A paper entitled “Study on matching characteristics of photovoltaic disturbance and refrigeration compressor in solar photovoltaic direct-drive air conditioning system,” published in the July edition of the journal Renewable Energy, contains the results of their experiments. The paper was co-written by Guoliang Li, Youhua Han, Ming Li, Xi Luo, Yongfeng Xu, Yunfeng Wang, and Ying Zhang.

The paper presents a 3 HP solar direct-drive photovoltaic air conditioning system which operates without batteries, and uses ice thermal storage instead to store solar energy. The refrigeration compressor suffers from loss of power, cannot even startup or shut down, if the PV power generation suddenly fluctuates.

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According to the researchers, in case of solar radiation fluctuations, the system can be kept running continuously and steadily through a proper design which matches the power consumption of the solar air conditioning system with a proper PV capacity, and an adaptive controller with a suited compressor simultaneously.

For this experiment, solar air conditioners with different capacity of PV panel, with and without MPPT controller and different types compressors, were built and tested outdoors to investigate the matching characteristics of photovoltaic disturbance and refrigeration compressor.

The experimental results of the system with a variable speed compressor and a MPPT controller have shown good ice-making performance and reliable operation as well as a great improvement in the available solar energy. The highest system COP reached 0.289 when the cumulative daily total radiation was 18.2 MJ/m2 in Kunming, China.

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The researchers believe that their work shows that the direct drive ice storage by solar photovoltaic system has a certain application prospect in the regions where the electricity is tight but requiring cooling.