a lightcell is an engine that uses light to make electricity




ultralight power

lightcells burn hydrogen/fuel mixed with sodium illuminant

hot sodium illuminant emits near monochromatic light,

which tuned photovoltaic cells collect to make electricity

sodium illuminant 

optical cavity

infrared recycling

ceramic recuperator,

 heat recycling


3000 suns

 yellow light (~2.1eV)


photovoltaic cells (~2.1 eV)



unlock the incredible energy density of hydrogen/fuel

in a highly efficient

whisper quiet package

lightcell can use hydrogen

lightcell can use fuel

natural gas







use hydrogen for most cycles

use fuel for extended duration

ideally, synthetic, net zero carbon emissions fuels


 target efficiency:    40% wire to wire

power:                 ≥  5 kw / kg

energy density:         500 watthours/L


module size:                    ≥  10kw, < 4 L 

hot sodium emits intense, 

nearly monochromatic light,

sodium's lone outer shell electron is easily excited

(vid: hacksmith, youtube, 2020)

sodium's weakly bound,

lone outer electron
"rings like a bell" at 2.1 eV, 

it takes only nanoseconds for the energy absorbed to be reemitted

as 589 nm, 2.1 eV photons
when sodium relaxes to its ground state

the transparent reaction cylinder is surrounded by a shell of "hot mirrors", which reflect infrared photons & let visible light through.

this allows for a recycling of waste heat, dramatically increasing efficiency

2.1 eV photons can be efficiently absorbed by a photovoltaic cell with a bandgap tuned to 2.1 eV

we can harness the materials developed for solar concentrating multijunction cells

a ceramic, 3d printed counterflow heat exchanger acts as a recuperator, collecting ~90% of the heat from the exhaust, and efficiently preheating intake air and fuel.

its many wiggles form an optical labyrinth, reducing losses from light leaking out the ends more than 20 fold

"hot mirror" infrared reflector reflectance vs transmission

counterflow ceramic recuperator


Physicist (Princeton PPPL)

MIT TR35, Forbes 30u30 

Inventor, lightcell

Cofounder, LightSail Energy

Danielle Fong, CEO

Steve Crane, PhD, VP Eng.

BS. MIT (Geophysics)
PhD. UCSD-Scripps

60+ patents in energy

Startup Technical Executive

Cofounder, LightSail Energy


founded: 2022

lightcell is a novel concept engine in development

there's prior art from fields such as concentrated solar, pyrotechnics (fireworks), sodium lamps, and thermophotovoltaics,

however, to our knowledge no past effort brought these concepts together.

this effort harnesses advanced new materials,
and uses physics at photon densities rarely explored.