Simulate freshly fallen snow for 30 continuous years.
Leverage bifacial solar panel technology in solar farms.
The solar market is actively moving to embrace bifacial solar panel technology. But to realize maximum gain of the second side or the back side of solar panels, many external variables need to be in place, including the 1) reflectivity of smooth freshly fallen snow, 2) best time of day, 3) best geographic location, 4) module mounting height, 5) most effective tilting of the solar array and a few others.
This reflectivity AND smoothness (of freshly fallen snow) is measured with an albedometer and prior studies have indicated that the ground must have an albedo of .8 or higher to assist in maximum gain.
From our conversations with numerous bifacial panel users, it appears that many do not clearly understand the foregoing. Developers are investing in bifacial technology without the assurance that gains (often stated by bifacial panel manufacturers on their product technical data sheets with specific percentages) are possible. Albedo is the fraction of light reflected from the surface. So, because a manufacturer states that the second side of a bifacial panel is capable of xx% gain increase, that gain cannot be guaranteed without the five external variables mentioned above.
To approximate freshly fallen snow, we have spoken to many developers who have considered and tested these materials:
1. White Gravel or Rock: Because some white rock is inconsistently colored, the albedo might be less consistent. When maintenance vehicles drive over white gravel, their tires will tend to disburse the rocks which may “fly” and other rocks will be pushed further into the soil. So, at some point, additional white gravel or rock may have to be delivered. White gravel or rock can cost $15-$17/sqm
2. White Agricultural Fabric: While white fabric agricultural ground cover is an option, it will not last for 30 years. White specialty fabric can cost $4 per sqm. Costs do not factor in installation and maintenance cost.
In 2019, Burns McDonnel shared the following in their white paper “Bifacial Modules” authored by Will Porter:
“Albedo — Annual energy production increases of 5% to 10% are typical with bifacial modules. In most areas, imported groundcover is often needed to push the increase much over 10%. The question is, does it pay to bring in light-colored gravel or roofing to control albedo? The answer to this question is both location- and project-specific, and a cost evaluation is needed to make the final determination. The estimated albedo for various surfaces is outlined in Figure 2.”
Green field / grass 23
White painted concrete 60-80
White gravel 27
White roofing material 56
Light gray roofing foil 62
White roofing foil for solar >80
Texas-based Eco Estates International, in conjunction with the University of Texas worked to create a liquid soil stabilizer that permanently binds and transforms the ground into a concrete-pavement-like-layer.
When sprayed on prepared soil, the soil stabilizer changes the color of the ground and achieves the albedo of snow. The soil stabilizers are proprietary polymer-based emulsions that use water dilutions for the application process.
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Fundamentally, the soil stabilizer represents a highly sophisticated piece of equipment.
The higher the albedo of the surface under your bifacial panel, the more gain you can realize from your bifacial panel. The darker the surface under your bifacial panel, you will not be able to realize the complete xx% UNLESS you have the albedo of smooth fresh fallen snow which is 0.80 to 0.90. We believe this soil stabilizer can give the ground a permanent, consistent and highly reflective surface.
We believe it will solve the albedo problem and provide easier financial modeling, accurate engineering design and accurate prediction for bifacial panels.
As Asphalt roads are not eco-friendly and their construction comes with the generation of toxic fumes and high costs, we believe this soil stabilizer will enable the creation of cheap eco-friendly access roads to reach a solar farm.
Because the soil stabilizer behaves as pavement, we believe it will block vegetation growth where it is applied: possible savings in maintenance costs might result.
Because the soil stabilizer behaves as pavement, it can reduce Shading Loss. Therefore, a possible increase in power generation might result.
Results (data summary, findings)
Before applying our soil stabilizer, we prepared the soil with painstaking care:
- First, the grass layer was completely removed from the surface.
- Secondly, a professional grade soil grader and a soil compactor were used by a professional road building team
- Thirdly, the piles for the mounting structure were drilled and the piles put in.
- Finally using a special water truck, we applied the soil stabilizer.
- After being evenly and thoroughly distributed into the soil on 3 separate passes, the soil stabilizer began the process of irreversibly transforming from a liquid to a solid.
Applying soil stabilizer on new solar farms
This installation does not exist. This picture has been retouched using Photoshop so one can see a proposed installation of soil stabilizer on a fixed tilt system.
Data for a 600 MW project in Vietnam now fully funded by investors, but not yet built
Because the KWh pricing of some areas of the world (like U.S.) is more than 50% less than Vietnam, we have inserted adjusted pricing.REVENUE Increase
Annual revenue with soil stabilizer: (adjusted to $39 Million USD)
Annual revenue without soil stabilizer: (adjusted to $31 Million USD)
Conservatively ~25% increase in revenue with soil stabilizer
NOTE: With land use of 2.5 acres/MW, we believe one can expect payback in 8-10 years. This will vary based on PPA and solar irradiation. We suggest and use of 1.6 acres / MW.
Here are the variables that we found to be important to calculating the gain to be achieved from bifacial technology and soil stabilizer working together.
Location of the project to determine the irradiation in average solar hours/day.
Number of MW and ratio of MW per acre or hectare:
Area reserved for solar panels only and Area reserved for access roads only
Height of the piles to determine the ground that will always be in shadow.
Space in between the solar row piles.
Type of mounting structure: Single Axis, Double Axis, Fixed Tilt, etc.
Bifacial power efficiency increase for different albedos from backside of Technical Data Sheet.
Your PPA, desired IRR and the income with and without having high albedo.
The minimum ground area needed to be covered to achieve the additional income with high albedo.
Analyze soil layers (vegetation & sand) and Review expected car or truck traffic.
Assumptions upon which the soil stabilizer albedo performance is based
One company that specializes in energy efficient roof solutions is Derbigum. One of the products that they offer is called Derbibrite, which is a white colored high reflective roof membrane. According to the manufacturers’ data sheet, Derbibrite has an albedo of 0.81.”1
White paint is shown to have an albedo of 0.8.2
Attribution to be added
Results of testing to-date
Soil stabilizer products have been independently tested and cited by NREL (National Renewable Energy Laboratory, Department of Energy USA).
Product testing, done by San Antonio Testing Labs showed no detectable concentrations of volatile, semi-volatile, heavy metals or petroleum hydrocarbons.
DECEMBER, 2020 Testing done by Sandia National Laboratories, finished its testing of soil stabilizer in regards to heavy metal contaminants, organic contaminants and water pollution and comparison of the results with those for AEP (Asphalt Emulsion Product). The inductively coupled plasma mass spectrometry from SANDIA National Laboratories have revealed that in most cases, soil stabilizer exhibited far less to no heavy metal contaminants compared to AEP.
The volatile organic analysis revealed extremely low petroleum hydrocarbon content and outgassing in the soil stabilizer products, while AEP revealed extremely high levels.
Physical Properties of soil stabilizer indicate it is 3x stronger than concrete and 4x more flexible than concrete.
Charts converted from metric. Thus, they represent approximations.
Permeability of soil stabilizers
Because the permeability of soil stabilizer formed structures is very low, engineers and contractors may need to design water run-off systems that may contain permeable structures at appropriate intervals in the solar farm.
Related Technical Notes:
Summary of Laboratory Testing: Erosion Resistance Test
New to the Solar Industry, our soil stabilizer is already in use in the Transportation Industry
One Month Later
2 Years Later
Summary of results/findings – key points or contributions of the study.
Our study reveals that a soil stabilizer in conjunction with carefully prepared soil should be able to simulate freshly fallen snow for 30 continuous years under certain conditions.
• We believe a soil stabilizer will solve the albedo problem and provide easier financial modeling, accurate engineering design and accurate prediction for bifacial panels.
• As Asphalt roads are not eco-friendly and their construction comes with the generation of toxic fumes and high costs, we believe this soil stabilizer will enable the creation of cheap eco-friendly access roads to reach a solar farm.
• Because the soil stabilizer behaves as pavement, we believe it will block vegetation growth where it is applied: possible savings in maintenance costs might result.
• Because the soil stabilizer behaves as pavement, it can reduce Shading Loss. Therefore, a possible increase in power generation might result.
Additional resources/next steps
Our next steps include:
- Tests to prove the long-term albedo delivery of the soil stabilizer and the pigment it contains
- Software to be created that will enable solar farm developers with understanding where exactly to place the soil stabilizer to achieve the best gain of their bifacial panels
Submitted by Sharon Bailey Beckett of Beckett Solar Energy