iwhat are some not-so-well known alternative energy sources. google it and you don’t find much. when i google alternative energy i usually get:
hyrdoelectric energy
photovoltaic energy
wind energy
geothermal energy
ethanol
biodiesel
biomass
tidal energy
hydrogen fuil cells
passive solar
besides that i know of:
microbial fuel cells
artificial photosynthesis
syngas
biogas
what else is there?