Wildfire Smoke Slashes Great Lakes Solar Output

Smoke‑driven aerosols cut solar irradiance by up to 10% across the Great Lakes

During the peak of the July 2024 wildfire episode, clear‑sky solar irradiance and observed global‑horizontal irradiance (GHI) fell as much as 10 % below average across the Great Lakes and the U.S. Northeast, according to Solcast’s high‑resolution satellite‑AI analysis. The loss was driven primarily by a > 6 % drop in clear‑sky irradiance, with the remaining gap coming from cloud‑related variability.

Solcast, a DNV‑owned data‑provider, tracks clouds and aerosols at 1‑2 km resolution using satellite imagery and proprietary machine‑learning algorithms. Their model bias is typically under 2 %, making the figures reliable for utilities and large‑scale PV owners that collectively manage >300 GW of solar assets worldwide.

Wildfire activity in Ontario created a dense smoke corridor

By mid‑July, more than 100 active fires were burning across northern and north‑western Ontario, a number that later rose above 180 as the province’s fire‑danger rating hit “extreme”. Smoke was advected southeastward, blanketing southern Ontario, Quebec, and then spilling over the Great Lakes into the U.S. Midwest and Northeast. Cities such as Toronto, Chicago, Detroit and Minneapolis recorded some of the world’s poorest air‑quality indices between 14‑17 July, prompting alerts in over 20 U.S. states.

Copernicus/CAMS PM10 data showed particulate concentrations peaking at 8 × the pre‑event baseline over north‑western Ontario on 17 July, while Toronto and southern Ontario saw a three‑fold rise. These fine particles attenuated sunlight even under clear‑sky conditions, directly reducing the GHI that PV systems could capture.

Soiling losses amplified the irradiance drop

The smoke‑laden air not only blocked sunlight but also deposited particulate matter on panel surfaces. Soiling losses accelerated dramatically, persisting until a rain event on 18 July finally washed the panels clean. This dual impact—optical attenuation plus surface soiling—exacerbated the overall irradiance deficit, a phenomenon documented in peer‑reviewed studies of aerosol‑induced PV performance loss.

Why aerosols matter more than clouds in this event

Machine‑learning‑based solar‑radiation research identifies aerosol optical depth as a primary driver of clear‑sky irradiance uncertainty, often outweighing cloud optical depth in smoke‑heavy scenarios. Solcast’s clear‑sky anomaly maps make this distinction visible: the aerosol‑induced dip appears before any cloud‑related fluctuations, underscoring the importance of high‑resolution aerosol monitoring for accurate PV forecasting.

What it means for Israel’s solar owners

Although the smoke event unfolded far from Israel, the mechanics are directly relevant to local PV operators. In Israel, a typical 10 kWp residential system in the central region yields about 17 000 kWh / year, valued at roughly ₪8 160 under the residential tariff of ₪0.48 /kWh. If a similar aerosol event reduced irradiance by 10 %, annual energy production and revenue would fall proportionally, modestly extending the payback period for such a system. Solar owners can mitigate these risks by monitoring aerosol forecasts (e.g., via Solcast or Copernicus) and scheduling cleaning after high‑soiling episodes, a practice increasingly recommended in the IEA‑PVPS best‑practice handbook.

Looking ahead: integrating aerosol data into PV forecasts

The wildfire episode highlights a growing need for real‑time aerosol monitoring in solar‑resource modeling. Researchers are already embedding aerosol optical depth into AI‑driven forecasting pipelines, improving prediction accuracy for both clear‑sky and cloudy conditions. As climate change fuels more frequent wildfires, utilities and large‑scale PV developers are likely to adopt these enhanced models to safeguard energy yields and grid reliability.

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Key takeaways

• Wildfire smoke in Ontario cut clear‑sky solar irradiance by >6 % and total GHI by up to 10 % across the Great Lakes region in July 2024.
• Over 180 active fires created a dense smoke corridor that spread to the U.S. Northeast, driving severe air‑quality alerts.
• Aerosol‑induced soiling persisted until rain on 18 July, adding extra losses.
• A 10 % irradiance dip would modestly extend the payback period for a typical Israeli 10 kWp home system, underscoring the value of aerosol‑aware forecasting.

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Sources & further reading

• Publications using Solcast data
• Machine-learning-based approach for solar radiation model...
• Influence of Clouds and Aerosols on Solar Irradiance and... - MDPI
• Seasonal solar irradiance forecasting using artificial intelligence...
• Insights from Recursive Feature Selection and SHAP Analysis