What you need to know:

• Dirt on solar panels reduces their efficiency and profit
• Solar O&M decision-makers must schedule panel cleanings
• Unexpected rain can make committing to cleanings difficult
• Solar Unsoiled’s ‘red-light, green-light’ cleaning feature, powered by Salient, de-risks rain unknowns
• The bottom line: tens of millions of additional revenue dollars to solar asset owners

“Soiling” decreases the electricity generated by solar panels

Soling is a well-known issue in the utility-scale solar industry. The most basic definition of soiling is small particulate matter – from dust, dirt, pollen, pollution, etc in the atmosphere – that lands on solar panels and blocks their ability to absorb light. Soiling decreases panel efficiency – read: electricity generation – by 1-40% depending on the region and season.

The solutions to soiling are two-fold:

1. Schedule panel cleanings
2. Wait-pray-hope for rain to clean panels*

A cleaning via rain costs nothing, while a scheduled cleaning is $1,000-$3,000 per Megawatt. Read more about the pros, cons, and ROIs of different approaches to cleanings [here]. 

*Note that rain-based cleanings only work in areas of the country where dust is the primary contributor to soiling (in the American Southwest, for example). In other areas, like the American Southeast, where pine pollen soils panels, scheduled cleanings are a must.

Unknown risks of rain can make committing to expensive cleanings difficult

In areas where soiling losses are heavily impacted by rain [read about ‘dirty’ vs. ‘persistent’ soiling environments here], Solar Unsoiled provides seasonally-optimized cleaning schedules. Optimization windows take into account 10 years of historical precipitation trends, but the risk of unexpected rain events is ever-present, especially in a changing climate. These seasonal anomalies contribute to fear around spending solar O&M budgets: decision makers don’t want to be in the situation where they’ve just cleaned their panels, only to have a rain event occur a few weeks later – one that could have recovered the asset’s efficiency losses at no cost.

Solar Unsoiled’s feature, powered by Salient, de-risks rain unknowns 

What is the probability of rain tomorrow? How about in the next 7 days? Or in the upcoming weeks? If it does rain, how much will impact the soiling on my panels? 

These are the kinds of questions solar asset owners and operators are asking when it comes time to schedule and implement optimized cleanings. Solar Unsoiled and Salient Predictions teamed up to make the answers easily available and digestible right in the Solar Unsoiled platform.

Using probabilistic rain predictions as a ‘red-light, green-light’ for cleanings 

Solar Unsoiled’s rain risk feature is active for solar farms in regions where soiling losses are influenced by rain events. At these sites, proactive, optimized cleanings have been recommended to Solar Unsoiled customers. Leading up to the cleaning date, customers can use the rain risk feature to see the likelihood of an upcoming rain event and determine if a change in plans is warranted. The forecasts in this feature – powered by Salient Predictions – show the likelihoods of different rain event scenarios over various forecast periods. These forecasts are updated daily, allowing users the ability to see changes in likelihoods and make necessary scheduling adjustments if a high probability of rain is evident.

No forecast is perfect. How does this help? 

No forecast is correct 100% of the time. But reliable, calibrated forecasts make a big difference over no forecast, or an unreliable forecast, over time. Salient climate scientist Brian Zimmerman describes how and why this is the case on Climate.gov using basketball as a metaphor.

The Salient and Solar Unsoiled ‘red-light, green-light’ feature won’t always be perfect, but sticking to a decision support system in the face of unexpected seasonal events will, in the long run, enable an O&M decision-maker to maximize profit - whether that be performing an optimized cleaning or holding off for rain to do the job.

The bottom line

Leveraging Salient’s predictions in a decision-support and risk-mitigation feature, Solar Unsoiled equips its customers with the tools to make informed decisions when spending tight O&M budgets on soiling mitigation.

The upshot: together our technologies can help the solar farm industry capture additional revenue – to the tune of an additional $66.7M per year in the US Southwest for example [read more].