battery
benzene
black
bulb
business
button
charge
cloud
commercial
conservation
contemporary
drop
ecological
ecology
efficiency
electricity
energy
environment
factory
fan
filling
fire
frame
fuel
globe
icon
industrial
isolated
light
line
motor
nuclear
nucleus
oil
petroleum
power
propeller
realty
recycle
recycling
simple
smoke
solar
stack
station
sun
symbol
ventilator
wind