Dust: The Main Environmental Hazard for Solar Energy

Solar energy has become the world’s best and most promising technology for new energy installations, rapidly gaining global acceptance thanks to ever-decreasing costs and ongoing mega-programs.

Advances in technology are also a key driver in improving the efficiency of solar energy, with the current double-digit boost coming from bifacial panels.

Dust: The Main Environmental Hazard for Solar Energy

Image Credit: OTT HydroMet - Solar Energy

The projected lifetime of photovoltaic systems has also been extended to a significant degree, from an initial 20-year standard to as many as 25 or 30 years in some instances.

Despite this groundswell of solar growth, one key factor continues to limit the performance of PV systems – dust and other forms of soiling accumulate on the glass surface of solar panels, preventing light from reaching the embedded cells.

Soiling is largely impacted by location as well as weather, meaning this is worse in areas suffering from air pollution, deserts (for example, the U.S. Southwest) and solar arrays that utilize flat tilt designs.

Soiling on residential rooftop systems, industrial or commercial PV installations or utility-scale arrays can have a surprisingly significant impact.

Even moderate soiling resulting from a failure to clean panels on a monthly basis has been calculated to account for a 30% energy yield loss per year. In the longer term, cumulative soiling, cementation or hard caking of dust and other materials can lead to a 100% loss of yield.

Soiling remains a complicated and challenging solar industry problem.

Analysis by the U.S. National Renewable Energy Laboratory has found that soiling causes uncertainty of supply, driving up the cost of solar energy due to lost production, higher maintenance costs, and, therefore, higher financing rates.

Developing an Effective Cleaning Schedule

A recent white paper on soiling produced by Kipp & Zonen entitled “Solar Panel Soiling” provides detailed information on the soiling issue from an economic, geographic and technical perspective.

The white paper also features a review of available panel monitoring solutions and an array of options for cleaning technology.

Addressing soiling requires owners first to understand soiling and recognize how to clean panels appropriately. The development of an appropriate and effective cleaning schedule is often the most elusive element in the soiling solution, however.

Being able to measure the soiling losses, seeing the soiling trend line and knowing the local precipitation forecast makes it is easier to decide whether to clean or wait. Local factories or composting facilities that produce dust can be a factor in areas where one wouldn’t expect PV panel soiling to be an issue.

Donald van Velsen, Product Manager, Kipp & Zonen

One highly advantageous tool for ascertaining the cost-effectiveness of panel cleaning is the DustIQ monitoring system from Kipp & Zonen.

Dust: The Main Environmental Hazard for Solar Energy

Image Credit: OTT HydroMet - Solar Energy

The system leverages the power of Optical Soiling Measurement (OSM) technology to determine the amount of soiling while utilizing a photodiode to measure any light scattered by dust and other soiling materials on the solar panel glass. 

DustIQ features its own PV cell, which enables the unit to be calibrated to accommodate local dust characteristics to better predict soiling – these characteristics can vary greatly in terms of particle size and color.

Van Helsen elaborates: “It’s not the color of the dust that influences the effect of the soiling but the sunlight reflection and absorption of the local actual soiling. This is why the DustIQ offers a local dust calibration using the sensors and an actual built-in PV cell.”

Once owners are aware that the energy yield of a specific PV system is down 5%, 10% or more, they can make informed decisions to clean panels at the most cost-effective time, defining an appropriate trigger-point at which to act.

Cleaning Options

Professional solar panel cleaners typically charge between $10 to $20 per panel when cleaning residential systems, but the majority of DIY owners will perform the task themselves.

This self-cleaning is a viable option for a solar homeowner who requires only a step ladder and a hose to clean the panels twice a year. Utility solar system owners, however, are faced with comparatively expensive options when cleaning large-scale installations.

A typical solar maintenance company will quote close to $500 per day to equip and run a maintenance truck. Manually operated, water-free cleaning systems can be costly, prompting the increased mainstream use of robotic solar panel cleaning systems, including drone-based solutions.

It is estimated that up to 100 gigawatts of new solar is installed globally every year, prompting solar system maintenance to become a substantial industry by itself. This growing market has also led to an increased preventative demand for special coatings for solar panel glass that are able to shed soiling.

A 2017 study by Transparency Market Research entitled “Solar Panel Coatings Market – Global Industry Analysis, Size, Share, Growth, Trends, and Forecast, 2017-2026” highlighted that the market for solar panel coatings – which shed dust among other functions — was estimated at $2 billion per year.

The analysts conducting this study also suggested that the solar coatings market will expand at a rate of approximately 27% over the following five years.

Acknowledgments

Produced from materials originally authored by Charles W. Thurston from OTT HydroMet.

This information has been sourced, reviewed and adapted from materials provided by OTT HydroMet - Solar Energy.

For more information on this source, please visit OTT HydroMet - Solar Energy.

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