Technical Brief

Water Cooling Method to Improve the Performance of Field-Mounted, Insulated, and Concentrating Photovoltaic Modules

[+] Author and Article Information
Matthew K. Smith, Hanny Selbak

Department of Chemistry and Department
of Mechanical and Materials Engineering,
Portland State University,
Portland, OR 97207-0751

Carl C. Wamser

Department of Chemistry,
Portland State University,
Portland, OR 97207-0751 
e-mail: wamserc@pdx.edu

Nicholas U. Day

Department of Chemistry,
Portland State University,
Portland, OR 97207-0751

Mathew Krieske, David J. Sailor

Department of Mechanical
and Materials Engineering,
Portland State University,
Portland, OR 97207-0751

Todd N. Rosenstiel

Department of Biology,
Portland State University,
Portland, OR 97207-0751

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING. Manuscript received June 6, 2013; final manuscript received December 23, 2013; published online January 31, 2014. Assoc. Editor: Santiago Silvestre.

J. Sol. Energy Eng 136(3), 034503 (Jan 31, 2014) (4 pages) Paper No: SOL-13-1159; doi: 10.1115/1.4026466 History: Received June 06, 2013; Revised December 23, 2013

The installation rate of crystalline silicon photovoltaic (PV) modules worldwide is at an all-time high and is projected to continue to grow as the cost of PV technology is reduced. It is important to note that PV power generation is heavily influenced by the local climate. In particular, for crystalline silicon-based PV devices, as the operating temperature of the panel increases, the efficiency decreases. Higher operating temperatures also lead to accelerated material and mechanical degradation, potentially compromising system effectiveness over the lifetime of the panels. In addition, atmospheric pollution can cause particle deposition on the surface of PV modules (soiling), reducing the amount of solar irradiance that reaches the PV material and reducing panel efficiency. Various cooling and cleaning methods have been proposed in the literature to mitigate these problems. In this study, a uniform film of water was continuously recirculated by pumping over the surface of a solar panel using an emitter head attached to the top of the panel. The water cooling technique was able to maintain panel temperature below 40 °C while adjacent untreated panels were operating near 55 °C. Besides the efficiency improvements due to cooling, the film of water also kept the panels clean, avoiding any reduced power output caused by panel soiling. Additional studies were carried out with artificially chilled cooling fluid, insulating materials, and side mirrors to examine the cooling system performance under different installation scenarios. Water cooling is concluded to be an effective means of increasing the efficiency of monocrystalline silicon photovoltaic panels. Under normal operating conditions, the increased energy output from the panels is more than sufficient to compensate for the energy required to pump the water.

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Grahic Jump Location
Fig. 1

Schematic representation of the experimental modules, where x represents the location of temperature sensors. Panel 6B was the only one fitted with the water cooling system.

Grahic Jump Location
Fig. 2

Power gain and temperature reduction using surface cooling on panel 6B on May 12, 2012. The pump was activated at 11:10 am. Power outputs and temperatures of control panels 6A, 6C, 6D, and 5A–5D are shown for reference.

Grahic Jump Location
Fig. 4

Power gain and temperature reduction using both surface cooling and concentrating mirrors on Panel 6B from 12:30 to 3:00 PM on July 7, 2012. Power outputs and temperatures of control panels 6A, 6C, 6D, and 5 A–5D are shown for reference.

Grahic Jump Location
Fig. 3

Power gain and temperature reduction using surface cooling on panel 6B when both panel 6B and panel 6C were insulated on July 9, 2012. Power outputs and temperatures of control panels 6A, 6C, 6D, and 5A–5D are shown for reference.




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