Convert cloud cover to GHI using a linear relationship.

        0% cloud cover returns ghi_clear.

        100% cloud cover returns offset*ghi_clear.

        Parameters
        ----------
        cloud_cover: numeric
            Cloud cover in %.
        ghi_clear: numeric
            GHI under clear sky conditions.
        offset: numeric, default 35
            Determines the minimum GHI.
        kwargs
            Not used.

        Returns
        -------
        ghi: numeric
            Estimated GHI.

        References
        ----------
        Larson et. al. "Day-ahead forecasting of solar power output from
        photovoltaic plants in the American Southwest" Renewable Energy
        91, 11-20 (2016).

def cloud_cover_to_ghi_linear(self, cloud_cover, ghi_clear, offset=35,
                                  **kwargs):
        """
        Convert cloud cover to GHI using a linear relationship.

        0% cloud cover returns ghi_clear.

        100% cloud cover returns offset*ghi_clear.

        Parameters
        ----------
        cloud_cover: numeric
            Cloud cover in %.
        ghi_clear: numeric
            GHI under clear sky conditions.
        offset: numeric, default 35
            Determines the minimum GHI.
        kwargs
            Not used.

        Returns
        -------
        ghi: numeric
            Estimated GHI.

        References
        ----------
        Larson et. al. "Day-ahead forecasting of solar power output from
        photovoltaic plants in the American Southwest" Renewable Energy
        91, 11-20 (2016).
        """

        offset = offset / 100.
        cloud_cover = cloud_cover / 100.
        ghi = (offset + (1 - offset) * (1 - cloud_cover)) * ghi_clear
        return ghi