def calc_heat_coll(eta_c, collector_irradiance):
    """
    .. csp_heat_equation:

    :math:`\\dot Q_{coll} = E_{coll} \\cdot \\eta_C`

    Parameters
    ----------
    eta_c: series of numeric
        collectors efficiency.

    collector_irradiance: series of numeric
        Irradiance on collector after all losses.

    Returns
    -------
    collectors heat: series of numeric

    """
    collector_heat = collector_irradiance * eta_c
    return collector_heat
