# Grid Availability

The Grid Availability Effect quantifies the amount of energy lost because the electrical grid to which the PV plant is connected is not available to accept power, meaning the PV plant must shut down and will not be able to generate.

Currently, SolarFarmer users simply specify the percentage power to be deducted from long-term as a result of grid unavailability (\(\Delta_{\text{grid,avail}}\)) and this input will equal the Grid Availability Effect reported in the Effects Diagram.

As the Grid Availability effect is intended to capture the long-term impact of an effect that is essentially binary on the timescale at which SolarFarmer calculations are typically run (10 minute to 1 hour time steps \(-\) the grid is assumed to be either available or not available for the whole of any given time step), it does not make sense to apply the Grid Availability Effect to non-aggregated data; i.e. it is not applied to 10 minute or hourly PV plant production data calculated from the input resource data. However, it is applied to time-aggregated data, for example monthly or annual data.

In order to calculate the energy potentially yielded to the grid over a period from power output data at the modelled frequency, power output at each step should be multiplied by the time step \(\Delta t\) of the data (in hours, assuming energy yield in kWh or MWh is desired) and summed:

$$E_{grid,pot} = \sum_{t}^{}{P_{trans,out}\left( t \right) \bullet}\Delta t$$

Provided \(\Delta t\) is constant throughout, clearly \(P_{\text{trans,out}}\) can be summed over the desired period then multiplied by \(\Delta t\) at the end.

The power delivered to the grid is then given by:

$$E_{grid,act} = \ \left( 1 - \Delta_{grid,avail} \right)E_{grid,pot}$$