In physics, energy economics and ecological energetics, energy returned on energy invested (EROEI or ERoEI); or energy return on investment (EROI), is the ratio of the amount of usable energy acquired from a particular energy resource to the amount of energy expended to obtain that energy resource. When the EROEI of a resource is less than or equal to one, that energy source becomes an "energy sink", and can no longer be used as a primary source of energy.
Read more about Energy Returned On Energy Invested: Non-manmade Energy Inputs, Relationship To Net Energy Gain, Economic Influence of EROEI, Criticism of EROEI, EROEI Under Rapid Growth
Famous quotes containing the words energy, returned and/or invested:
“The scholar may be sure that he writes the tougher truth for the calluses on his palms. They give firmness to the sentence. Indeed, the mind never makes a great and successful effort, without a corresponding energy of the body.”
—Henry David Thoreau (1817–1862)
“Then the LORD said to Moses, “Stretch out your hand over the sea, so that the water may come back upon the Egyptians, upon their chariots and chariot drivers.” So Moses stretched out his hand over the sea, and at dawn the sea returned to its normal depth. As the Egyptians fled before it, the LORD tossed the Egyptians into the sea.”
—Bible: Hebrew, Exodus 14:26,27.
“Children are intensely invested in getting their way. They will devote more emotional and intellectual energy to winning arguments than parents ever will, and are almost always better rested.”
—Jean Callahan (20th century)