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Calculations

📄️ How HOMER Calculates the Maximum Battery Charge Power

In each time step, HOMER calculates the maximum amount of power that the storage bank can absorb. It uses this maximum charge power when making decisions such as whether the storage bank can absorb all available surplus renewable power or how much surplus power a cycle charging generator should produce. The maximum charge power varies from one time step to the next according to its state of charge and its recent charge and discharge history.

📄️ How HOMER Calculates the Radiation Incident on the PV Array

The Solar GHI Resource page allows you to specify the global horizontal radiation (GHI) for each time step in the HOMER simulation. The GHI is the total amount of solar radiation striking the horizontal surface on the earth. But the power output of the PV array depends on the amount of radiation striking the surface of the PV array, which in general is not horizontal. So in each time step, HOMER must calculate the global solar radiation incident on the surface of the PV array. The following describes that process, which is based on the methods in the first two chapters of Duffie and Beckman (1991).