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New Tripoli, PA, United States, 2011/04/13 - New technology can replace expensive solar tracking systems by using a coating of nanomaterials on top of the solar cell - SolarPA-Inc.com.
Solar tracking systems are used to continually orient photovoltaic panels towards the sun and can help maximize the investment in a solar installation. They are beneficial as the sun’s position in the sky will change gradually over the course of a day and over the seasons throughout the year.
Debate continues as to the economic benefit of a tracking system. A rigid, standalone solar installation is a very reliable and uncomplicated source of energy production - the panels don’t move and require little maintenance. Adding a solar tracking system means adding moving parts and gears, which will require regular maintenance of the solar system and repair or replacement of broken parts. Trackers are structurally less rigid then permanent mounts and hence can be vulnerable to storm damage.
There are different types of tracking systems, active and passive, and within these categories single-axis and dual-axis.
Then, of course are the costs. A 2010 article in Solar Choice: solarchoice.net.au/blog/solar-trackers.html, notes that costs are lower with larger installations, and payback time ranges from 9 to 12 years for an installation in Sydney Australia compared to a rigid installation. Of interest is a graph of output power of an installation over the course of a day of a fixed versus dual axis tracker:
Privately held SolarPA (solarpa-inc.com) has shown that it can use a coating of its proprietary nanomaterials on top of a completed cell to obtain a similar result, as show in the graph below:
Not only is the efficiency higher by above 20% at grazing incidence of sunlight (such as dawn and dusk), but the efficiency of an uncoated cell at 90 degree incidence to the sun (such as noon) is higher by 9.4% when coated with its NanoCoat.
The 9.4% increase is efficiency at 90 degree illumination also has some important ramifications. As the output of a solar plant is increased by 9.4% with the addition of the coating, a 50 MW plant now becomes a 55 MW plant. More importantly, this technology can move binned marginal efficiency cells above a company's minimum level to become useable. This is critical. Every day solar cell manufacturers make low-efficiency cells, some days are worse than others, because the manufacturing process, although highly automated, is subject to outside forces, such as the quality and defects of the solar cells and variations in materials and processing parameters. One estimate I've seen is that as much as 20% of annual production results in marginally efficient cells. If a 50 MW plant makes 10 MW of marginal cells at a production cost of $1 per watt, that's $10 million that could be lost. Increasing the efficiency of these cells by up to 10% at a cost of a few cents per watt is a huge factor in cost effectiveness.
This is a clear indicator that for home, office, or commercial building solar installation, tracking systems can be definitely eliminated. The effect of this coating, which sells for about 2.5 cents per watt, on solar farms is also if interest in reducing or eliminating the need for tracking. The efficiency of solar cells degrades with increasing temperature, due to changes in the bandgap of silicon at higher temperatures. Another graph from SolarPA shows that the efficiency degradation is less than an uncoated cell at 50 degrees C. In this graph, the room temperature (25 degrees) increase in their NanoCoat cell was 8.4% above a non-coated cell but the relative efficiency increased to 10.4% above the uncoated cell at 50 degrees. Thus, the NanoCoat cells not only work better at elevated temperatures than a standard cell, and additional benefit could also be the elimination of tracking systems.