The purpose of the webtool is to give a first basic idea about the performance of the selected agrivoltaics system. Therefore, caution should be taken with the results of the simulation tool. This is because these results are based on a number of assumptions. Below, these assumptions and the input/output parameters of the tool are explained in more detail.
First, the location for which the simulation is being performed must be selected by entering the latitude and longitude of the corresponding location. In reality, of course, not all locations across Europe were simulated individually. Europe was divided into 10 horizontal strips where it is assumed that all locations in a strip have approximately the same climatic conditions. After entering the exact coordinates, the tool will determine to which strip this location belongs and then display the results associated with this strip.
Once the location has been set, the structural parameters of the PV array can be changed using the sliders. However, the tool is limited to arrangements in a shed structure, as shown in the figure below.
The height parameter is defined as the distance between the canopy of the crops and the lowest point of the PV array.
The ground coverage ratio or GCR is a parameter used to express PV density. The GCR is calculated as the ratio between array width and row-to-row distance. In this tool, a fixed array width of 2 meters is used. Therefore, if a GCR of 40% is chosen, it corresponds to a row-to-row distance of 5 meters.
The tilt angle of the PV setup describes the vertical angle of the solar modules, as shown in the figure above.
The direction angle of the PV setup describes the orientation of the PV modules in the horizontal plane, with 0° facing south and 180° facing north.
The last geometric parameter is the module transparency which describes the amount of light the PV modules allow to passthrough. In standard solar parks, opaque PV modules are used (transparency degree of 0%) because the goal there is solely on generating electricity. However, in an agrivoltaics setup, standard opaque PV modules may be taking too much light away from the crops. In these situations, it may be interesting to use semi-transparent PV modules. A transparency degree of 40% then means that over the surface of a PV module 60% of the light is blocked for the generation of electricity and still 40% is let through for the crops. The figure below shows an example of a semi-transparent PV module with a transparency degree of 40%.
Lastly, the crop type needs to be selected to be able to give a rough estimation of the expected crop yield. Crops are divided into shade intolerant (-1), shade tolerant (0) and shade loving (1):
Shade intolerant crops are crops that every reduction in light results in a reduction of crop yield.
Shade tolerant crops can tolerate reduced amount of light up to a certain level, but if there is too great a drop in light, crop yield will also decrease considerably.
Shade loving crops are crops in which a decrease in the amount of light will cause an increase in crop yield. However, if the amount of light continues to decrease, this crop will also be negatively affected by the light reduction and the crop yield will decrease.
If it is not known to which group a specific crop belongs, it is recommended to choose the shade intolerant option as this represents the worst-case scenario. This classification is then used to make an initial rough estimate of the effect of an agrivoltaics system on the crop yield based on models from literature.
The tool returns a couple of KPI’s that allow for an initial evaluation of the agrivoltaics setup.
The installed power is expressed in MWp/ha which makes it easy to scale up this result to larger areas. The PV modules used in this tool are bifacial PV modules with a power of 214 Wp/m² and a bifaciality factor of 0.7.
The energy yield is expressed in MWh/ha per year and is calculated based on average weather data from over 10 years (TMY data from PVGIS). In order to calculate this energy yield the albedo (the fraction of solar radiation incident on the ground that is reflected) is set at 20%.
The average DLI (daily light integral) expresses the absolute amount of light that is reaching the crops on average over the period from April until September. This parameter is also calculated based on average weather data from over 10 years.
The remaining PAR percentage is used to compare the amount of light reaching the crops in the agrivoltaic setup with the amount of light reaching the crops in a reference field (without PV modules). A remaining PAR percentage of 100% means that the agrivoltaic crops get the same amount of light as in the reference field. A remaning PAR percentage of 75% means that the agrivoltaic crop get 25% less light, and so on…
The deviation PAR is a parameter that expresses the homogeneity of the light distribution on the field under the agrivoltaic setup. The presence of solar panels not only results in less light, they also cause an uneven distribution of light across the field. It is therefore possible that one zone of the cultivation surface gets all the light, and another zone almost none. It is obviously desirable that the light distribution is as homogeneous as possible an therefor the homogeneity factor should be as low as possible. The deviation of the PAR is shown here as the standard deviation of the PAR distribution under the agrivoltaic setup.
The relative crop yield gives a rough estimate on how the agricultural yield would be influenced by an agrivoltaic setup. For example, a relative crop yield of 90% means that the agrivoltaic setup provides 10% less crop yield compared to a reference field without agrivoltaics. However, these results must be treated with great caution. These yield estimates are based on theoretical models that have not yet been validated with actual field trials. Thus, the results are still very uncertain and should be interpreted accordingly.
The LCOE or Levelised Cost Of Electricity is a parameter used to evaluate the economic feasibility of an agrivoltaigs setup. The LCOE is the average net cost of electricity generation for an agrivoltaic installation over its lifetime. This value can be compared with the market price for selling electricity or the LCOE of other generation technologies in order to evaluate the economics of a agrivoltaic project.
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