Light carries energy and heat, and plays a key role in many energy-conversion processes. The capabilities
to tailor electromagnetic energy transfer at the nanoscale represent important opportunities for novel
energy applications. In this talk I will present two sets of studies integrating experiments and theory. In
the first part, I will discuss how to use near field electromagnetic energy transfer for energy conversion
and photonic refrigeration. I will begin by showing an experiment achieving a 40-fold enhancement of
thermophotovoltaic conversion rates, by reducing the distance between a thermal emitter and a
photovoltaic cell to the nanoscale. This lays the foundation for exploring near-field thermophotovoltaics
for waste heat recovery. I will then show a demonstration of active photonic refrigeration through control
of the chemical potential of photons. This points to a fundamentally new, promising way for solid state
refrigeration by combining nanoscale photonics and optoelectronics.
In the second part, I will discuss how to turn the cold outer space to a thermodynamic resource for passive
cooling and energy efficiency. I will introduce our first demonstration of passive radiative cooling to
below the ambient air temperature under direct sunlight. Next I will show an experiment achieving
passive cooling to 42 ˚C below the ambient temperature, pointing to new regimes of applications such as
food preservation in remote areas. I will also show results of lowering the temperature of a solar absorber
by 13 ˚C while maintaining the sunlight absorption, pointing to significant efficiency improvement for
solar cells. Finally, I will give an overview of my future research directions.