Recent suggestions that worthwhile additional cooling of 1.0-1.5 degrees C below what glass covers in solar cell modules already achieve, hence raised power output, will occur via enhanced thermal radiation to the sky with special nanostructures, is examined. Rigorous thermal models indicate these observations require a much lower hemispherical emittance (E-H) for the benchmarks of silica and glass covers near 0.75. If the currently accepted value for E-H of glass of 0.84 applied even E-H=1.0 would provide inadequate extra cooling. An accurate angular emittance profile for glass does predict this lower E-H. Complete models include solar heating, heating by atmospheric radiation, cooling by convection and side/base losses. Unfortunately any large lift in radiative output from raised E-H at normal cell temperatures is mostly annulled by the accompanying fall in convective cooling. The link of E-H to angular IR response points the way to novel coating approaches which may achieve the desired cooling gains. This has wider implications for buildings and other solar technologies. Direct power gains from accompanying anti reflectance add value. (C) 2016 Elsevier B.V. All rights reserved.