Published: Dec. 14, 2020


One of the main problems with photovoltaic energy conversion is that the sun shines only in the daytime. Without inexpensive and efficient energy storage, alternative energy production systems must be available to provide around-the-clock power. This invention provides a method for generating renewable power during nighttime, as well as during the day.

One potential source of nighttime power is radiation from the surface of the earth. The problem with this scheme is that devices that operate at ambient temperature cannot harvest radiation from an object at that same temperature. According to well-known Carnot conversion efficiency limits, there must be a substantial difference between the source and the conversion device to produce usable power.


Dr. Garret Moddel at the University of Colorado Boulder has invented a method to harvest energy from an ambient temperature source. As discussed in the background segment, this would seem to be impossible because of the Carnot requirement that the source and converter be at different temperatures. However, this invention demonstrates that there is a way to circumvent this requirement. The invention works by using an ambient heat source, such as the Earth, that passes its heat through a conversion device that provides usable electrical power from thermal power passing through it. This heat is radiated out into space, which is cold. So that the atmosphere does not interfere with the radiation, it is limited to a narrow band of wavelengths over which the atmosphere is highly transparent. Continuous electrical power is generated during nighttime, as well as during the day. 

figure a


  • Around-the-clock power
  • Potentially low-cost thin panels


  • Continuous power for lighting
  • Remote power source for communications
  • Trickle charging of batteries


This technology is available for exclusive or non-exclusive licensing.


Nicole Forsberg: