Scientists in China have developed a new snow-removal system for off-grid and grid-connected PV systems that makes very little use of grid electricity.
The “domino-like snow removal system” (DSRS) uses electricity from uncovered PV modules to remove snow from solar arrays, string by string.
“With a high snow removal efficiency, it is almost free of utility power consumption,” researcher Wen Liu told pv magazine. “The snow removal principle is verified to have no negative impact on the performance of PV modules by experiments cooperated with Chinese PV module manufacturer JA Solar.”
The researchers said that the string that initially removes snow supplies power for the subsequent snow-covered strings, in a sequence that they compare to falling dominoes. The system only uses grid electricity with the first panels, as the PV electricity is responsible for subsequent snow removal.
The DSRS is connected to each of the PV system strings via tee-type MC4 connectors and PV cables. It uses the thermal effect of resistance to uniformly heat the entire PN junction area of the PV modules.
“The heat is transferred to the snow layer through the EVA film and the tempered PV glass, which causes the snow to melt,” the Chinese team said, noting that the system relies on a maximum power point tracker (MPPT) algorithm that launches the removal process with high sunlight utilization.
“The snow melting process occurs at the surface of PV modules, which is regarded as a one-dimensional heat transfer perpendicular to the surface of PV modules,” said the scientists.
The researchers tested a system prototype in a real winter snow-cover environment and found it can achieve “good” snow removal in environments with, a minimum tilt angle of 27 degrees, a minimum temperature of –14.8 C, and minimum fluctuant solar radiation of 248 W/m2 in an off-grid mode.
“The DSRS can deal with different types of snow, whose densities range from 121.05 kg/m3 to 480.10 kg/m3 with thicknesses varying between 15.5 mm and 32.5 mm,” they explained.
They said the system could have a cost of between CNY 0.17 ($0.025)/W and CNY 0.29 CNY/W installed in PV systems ranging in size from 10 kW to 30 kW. The payback time is estimated between 2.9 and 4.3 years.
“The bills-of-material (BOM) cost for this additional box is less than $500 and its installation can be performed with only a few more electrical cables and three port connectors, so the cost is really low,” Liu said. “To my best knowledge, there isn't any low-cost solution for snow removal so far and I believe that this technology may become widely adopted.”
The research group presented the system in “A novel domino-like snow removal system for roof PV arrays: Feasibility, performance, and economic benefits,” which was recently published in Applied Energy. The group includes academics from the University of Science and Technology of China, the Xiong'an Institute of Innovation, and JA Solar.
“This paper presents a systematic work around the feasibility, performance, and economic benefits of the domino-like snow removal system and confirms it is an excellent solution to removing snow on PV modules and has great potential to promote PV deployment where the snow covers for a few months in winter,” the group concluded.
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