Like the dew on the mountain, Like the foam on the river,
Like the bubble on the fountain, Thou art gone, and forever!
–The Lady of the Lake
by Sir Walter Scott (Canto iii. Stanza 16)
© J. Dirk Nies, Ph.D.
Renewable energy is touted as a sustainable solution toward meeting our country’s voracious energy needs. But is energy actually renewable? We recycle paper, plastic, glass and metal. We compost organic materials for later use in the garden. In nature, moisture evaporating from the salty ocean falls to earth renewed as pure rainwater. These examples demonstrate that atoms can be recombined into new materials and recycled myriad times with no loss in their inherent properties and value. But is the same true for energy; can it be recycled and renewed?
The First Law of Thermodynamics says that energy can neither be created nor destroyed, so it would seem reasonable that it could; yet the answer is emphatically no. Energy is not renewable. Furthermore, once energy has run its course on earth, regardless of its source, “like the bubble on the fountain,” it is “gone, and forever!”
Energy—from the Greek meaning “at work”—is a subtle concept to grasp. Physicists elegantly describe what it does and how it behaves, but stumble when expressing what it is. Energy has no substance. It is immaterial. It possesses no essence. It often hides itself and appears in many guises. Like yin and yang, energy is sometimes active, as in the radiant energy of sunlight and the flowing energy of a waterfall; while at other times it is passive, like electrical potential stored within batteries and food calories stored in a grain of corn.
Life—our lives and all life on earth—requires energy that flows. This holds true for an individual organism, for large ecosystems, for the entire biosphere of earth. For life to exist, for our economy to function and prosper, this is a universal, steadfast rule: energy must come in, energy must be processed, energy must leave. To do the work of life, energy must flow through life. Energy must visit but it cannot stay.
To illustrate this idea, I will use flowing water as a metaphor for energy. Picture a waterwheel beside a gristmill. The weight of the water and its forward motion push against the paddles, causing the wheel to turn a shaft that rotates the runner millstone that grinds corn against the stationary bed stone—a proven technology in use for more than 2,000 years!
The wheel will continue to transform energy into the useful work of grinding corn into cornmeal until either the water dries up or the flow of water downstream is impeded.
In the first case, no more water means no more energy. This we readily can understand. In the absence of water, the wheel stops. But equally important, in the second case, if water can’t flow away from the wheel, the millstream eventually will create a lake deep enough to engulf the wheel, causing it to stop turning. In other words, even in the presence of energy, when energy stops flowing, work ceases.
Now imagine our waterwheel, with the water able to freely flow again, operating a water pump instead of a millstone. There are two millponds in this scenario; one located just upstream and the other just downstream of the waterwheel. The water pump is situated in the lower pond. As water flows over the wheel and into the lower pond, the pump continuously returns a corresponding amount of water through a pipe back to the upper pond. In theory, this waterwheel could turn forever. The water (energy) could be perpetually “renewed” by returning it back to the upper pond.
Here’s the catch. The water could be renewed to the upper pond only so long as we did not have the waterwheel do anything else but operate the pump. This is the key point. Energy can only be renewed if we make no demands upon it to do anything else but renew itself. But this is a futile exercise, like walking around in a circle. Nothing new is accomplished. You merely end up where you started from. Moreover, in the real world of friction, turbulence, chaos and entropy, all perpetual motion machines (including our imaginary waterwheel-powered pump) eventually will stop. No machine, no matter how advanced in its technology, can turn energy into work, work into energy, or convert energy from one form into another and back again with 100 percent efficiency. This is the Second Law of Thermodynamics. Some fraction of energy always dissipates away and is lost to the environment, often in the form of waste heat.
A corollary of the Second Law of Thermodynamics is that heat always travels from hot to cold. Consequently, the bitterly cold expanse of outer space is energy’s ultimate destination. This is where all energy on earth eventually travels to. Space is the final frontier and dumpsite for waste heat generated by work performed here on the planet. This is true whether the source of energy to power our economy and to do the work of life is renewable or not.
Getting back to the main point, since energy is not profitably renewable, what do we mean when we say “renewable energy?” We mean that we extract energy from a resource more slowly than the resource itself is being replenished by natural processes.
The sun, by slowly transforming its mass into sunlight, is the principal source of energy here on earth. Solar energy and its manifestations found in hydroelectric power, biomass, wind and waves are considered renewable because we are tapping these resources slower than they are being naturally restocked. Conversely, we are consuming non-renewables such as coal, oil, natural gas and nuclear materials much faster than the earth, sun and stars are replenishing them.
In conclusion, for life to exist, for our economy to work, energy must flow. Life flourishes and grows in richness, complexity and diversity over time because the rotating earth (like a waterwheel) receives a steady stream of high-value energy from the sun. This inflow is balanced by an equal outflow of energy wafting back into space. And we can thank our lucky stars that the cosmos is big enough and cold enough to handle our planetary outflow so heat doesn’t get dammed up here on earth.
Energy’s lot in life is to survive when used, but with a diminished capacity to do more work. This behavior explains why we are in constant need of high-value, work-capable energy. Relying heavily on non-renewable energy to do the work of life is like living off an inheritance; a sure path to insolvency. The remedy is to switch to naturally replenished energy resources. We can rest assured that there always will be sufficient funds in our bank account so long as deposits are greater than withdrawals, so it is with renewable energy.
To power our economy from replenishable energy resources, however, will take a lot more than luck. Hard work and thoughtful choices need to be made. We can find encouragement and fortitude for tackling the monumental task of moving our economy in the direction of more closely emulating the energy economy of nature in the knowledge that in doing so, we will establish not only a more secure energy future for ourselves and our children, but also promote harmony between planetary inward and outward flows of energy. But that’s another story which I will address next time.