environmental
alternative
battery
bio
bulb
charge
clean
conservation
contour
earth
eco
ecology
electric
electricity
energy
environment
factory
generator
global warming
green
icon
lamp
life
light
lightning
line
linear
mono
natural
nature
nuclear
outline
panel
planet
plant
power
recycle
resources
save
science
sign
solar
swirl
symbol
technology
tower
tree
turbine
urban
wave
wind