Soiling

Module soiling is important for solar modeling, particularly in heavily snowed or dusty environemnts. In Solesca, you can choose to either specify your own soiling values or have Solesca calculate them for you.

Solesca's Automatic Soiling (Recommended)

Solesca's Auto soiling/snow loss feature allows you to have Solesca do the hard work for you! To enable, just toggle the button on. This can be done on the engineering template or on a project-by-project basis. If enabled, Solesca will automatically calculate soiling when running an energy simulation.

There are two parts to total module soiling, snow and dust/debris. Solesca uses the Townsend Snow Model to calculate snow losses and the Kimber Model to calculate dust/debris losses. We use the closest NOAA and NCEI weatherstation annuals for the calculations. Both the Townsend and Kimber models are aggregated together to get the total soiling losses for the system, which is displayed in the Advanced tab within the project. You can see these values updated after every simulation, as they will change based on array type, tilt, and location.

Note: if we cannot find a NOAA station within 150km of your array location we will default to using your entered or default soiling values.

Recommendations for entering soiling manually

When entering in your own soiling values it is recommended to have 2% set in your engineering template for all months and then enter on a project-by-project basis within the Advanced tab.

Understanding snow and soiling losses

The two components of total soiling are snow and soiling losses.

Snow Losses: The more north your project is, the higher the likelihood of significant snow losses in the winter months. It is not uncommon to see months with >10%, or even >30%, soiling losses in November through March due to snow. Tilt angle also greatly affects the snow loss rate, as a lesser angle will build up snow more than a greater angle. Therefore, it is recommended to test different tilt configurations at higher latitudes (starting with 30°) to find the best system production.

Soiling Losses: The Kimber Model assumes a linear increasing of dust/debris until a rainfall. It must rain over a threshold to 'clean' the modules and reset the soiling to 0. Solesca uses your weatherfile and the NOAA annuals to calculate when we predict it to rain (and by how much). The summer months are the dry months, so it is not uncommon to have up to 10% soiling in June through September (since no rain is falling to clean the modules). This is primarily observered in places like California or Arizona, where there is no predicted rainfall for mutiple months. It can even get to >20% losses!

If you believe any months are too conservative, you can have Solesca automatically calculate total soiling for you and then toggle the button off. This keeps the calculated values and allows you to change the month(s) in question on a case-by-case basis.