How much should we cover our rafts?
When our industry has rafts for pumping water from its productive activity, we want there to be only water: any excess of algae can cause the maintenance cost to increase. In that case, coating as much surface area as possible ensures that there is neither light nor chlorophyll enough to support life.
However, when rafts are located in natural environments, it is necessary to limit the surface of the coating, to prevent damage to the aquatic ecosystem. In that sense, research published in the American Geophysical Union in 2018 found that installing FPV, so that shadow is cast on the lake has the following effects:
This is a very interesting article but, unfortunately, they assumed as a constraint that a minimum water level is needed for the FPV, which makes the economical part of the research invalid for our design. Anyway, although our product would be more profitable than that of the study because we do not need a minimum water level, it is absolutely valid for the ecological part.
The plot below shows that a coverage ratio of 40% is suitable for algae avoidance.
Figure 2- Chlorophyll-a concentration vs FPV coverage ratio (%). Source: Energy Conversion and Management 206 (2020) 112414
Figure 3- Chlorophyll-an evolution during the year with FPV coverage.
According to the previous research, the use of the reservoir will define the FPV coverage ratio as shown below:
Table 1- FPV coverage ratio according to water use
With Yada’s current design, the 40,8% of the surface is shadowed, while we only touch the 7% of the total water surface. This number can vary dependending on the string’ size. This means that the pollution risk of the water is minimal while the quality of the water keeps optimum.
Figure 4- Algal bloom in Lake Eire (USA)
Covering the reservoir protects the water from the dust, rain, birds, and algae growth. This technology has been used in several locations in US also diminishing the water evaporation in these reservoirs. But we find it almost useless compared with a solar system.
