Step 7 — Determine True Sustainability
There is a big problem in considering what mix of future alternative energy systems will sustain a livable civilization. We cannot just assume that various forms of solar, wind, and geothermal will actually be solutions to our energy needs. The problem stems from the fact that in order to produce usable energy (exergy) we have to expend energy building the energy conversion capital equipment and distribution infrastructure. Right now that energy comes from fossil fuels, for the most part. For example the manufacture of silicon photovoltaic cells depends on a tremendous amount of electricity generated by coal-fired power plants. It is true that once in place collecting solar energy these cells will produce a stream of electrons for perhaps the next 30 years (with maintenance). But will they produce enough excess energy, above that needed by the economy for other work, to go toward producing their replacements at the end of their useful life? That is the big question. It is the ultimate energy return on energy invested (EROEI) question.
No one currently knows the answer to that question. Studies of energy requirements for manufacturing solar panels, shipping, installation, and even scrapping at the end of their lives, have been done showing that there is a net gain over that time. But all of these studies suffer from a framing problem. They do not account for other, more long-range energy inputs into the life cycle of these systems. For example, they do not include all of the energy inputs into the physical plant that houses the manufacturing equipment. They do not include all of the labor and overhead (heating and lighting) or capital (building and equipment) requirements appropriately amortized over the number of panels built. Going even further out, they do not include the energy inputs to construct and maintain the farming and commercial activities that apportion to the solar panel manufacturing plant, the transportation system, the installation workers and so on.
There is a vast energy web that supports all manufacturing processes. And there are flows of energy through that web that effectively form a pyramidal structure superimposed on it, with the manufacturing facility at the apex. It is true that the amount of energy flowing upward through this web becomes almost infinitesimally small at the extremes. One is tempted (and the researchers were) to ignore these inputs. Either we can lump them together and estimate their influence or just leave them out altogether. The problem is that all of this energy is coming largely from fossil fuel sources that basically act to subsidize the construction of these alternative energy equipment. Figure 1, below, provides a graphic view of this concept.
Figure 1. Sustainable energy production requires that there is enough "excess" energy produced from the collection/conversion capital equipment to re-invest in building replacements.
Raw energy must be converted into a usable form, which we call exergy. This is the energy which is available to do useful economic work. Here I have separated that work into other consumption by generic "Energy Users" and the infrastructure needed to build and maintain the energy conversion capital. The produced exergy is split into two streams, one used for other economic work and one used to supply the construction and maintenance infrastructure. This includes energy subsidization of agriculture to feed labor supplied to all the supporting industries. The white arrows represent energy flows, the black arrows represent material flows. The white wavy arrows represent the inevitable loss of heat from all processes. In the world of energy everything must balance and all wastes must be accounted for. Note that thinner arrows represent a proportionally smaller amount flowing per unit of time.
It takes lots of energy to extract raw materials and form them into usable material inputs to the manufacturing process. It takes a lot of energy to build and run the manufacturing plant. Where does all of that energy come from? Currently it comes from fossil fuels with smaller contributions from nuclear and hydroelectric. But even those nuclear and hydro plants were built and are maintained by use of fossil fuels! No matter what kind of energy conversion capital we talk about, conventional or alternative, all of them must be able to pass the long-term sustainability criterion. They must all produce more energy than they supply to other economic consumption in order to be self-sustaining. And they must do it forever, effectively. Of course fossil fuel energy can't meet this latter constraint because we are running out of it. As I have already pointed out, we look to have passed the peak of global oil production and that will be followed within decades by the peaks of natural gas and coal. And that will be the end of that easy money.
There are, of course, different ways to achieve this criterion. If we insist that the energy supply to the economy (other than the energy capital infrastructure) must exactly replicate our current fossil fuel-based level then it is unlikely that any combination of alternative sources will meet this criterion. If we insist that we need to consume as much energy as we do today to keep our over consumptive lifestyles unchanged then when the fossil fuels run out (or become excessively expensive) we will not be able to even build replacement solar cells and wind turbines! We will be up s**t creek.
On the other hand, if we get wise, we will start decreasing our wasteful energy consumption ways now and reserve fossil energy for bootstrapping our alternative energy infrastructure in such a way that it can achieve the long-term sustainability criterion. We need to phase out reliance on fossil fuels and phase in a closed loop system as diagramed above, one that is self sustaining. This won't be easy to do, especially in the current economic system that assumes that when fossil fuel prices go up people will switch over to alternatives. The reason is that since the whole alternative energy infrastructure is subsidized by fossil energy now, as the price of fossil fuels increase the costs of producing alternative conversion capital will increase as well. In other words, alternatives will never come to be cost competitive (in dollars but also in energy terms) and will forever be behind the eight ball. Unless we make a conscious decision to subsidize the production of alternative capital AND demonstrate that that capital equipment can be self-sustaining we are just digging a deeper grave for modern civilization.
We could build a demonstration (proof-of-concept) system in the dessert. A large solar photovoltaic plant could supply energy to produce silicon cells and associated equipment. Its energy could be used to produce biofuel for extracting, transporting, and forming the raw materials, includding food for the workers. It would resemble a living plant organism, taking in sunlight, and accessible raw materials and producing another copy of itself with no other energy subsidies! Over its supposed life cycle it might replicate itself several times over, meaning that some of those copies represent increases in the flow of energy to society. That would be an interesting experiment wouldn't it? Figure 2 shows this idea of a system replicating itself in order to be self-sustaining.
Figure 2. Every alternative energy conversion plant needs to be able (essentially) to replicate itself over its useful life, plus provide usable energy to the economy. After an initial bootstrap from fossil fuel-based energy sources, the system needs to become self-sustaining. The surrounding circle represents a boundary where no other forms of energy can enter other than sunlight (for this solar PV example) after that first system is built from fossil sources.
Work on researching the energy sustainability criterion for various alternative energy source proposals should commence immediately. Had we done this before developing policies to subsidize and encourage corn ethanol we would never have gone down that road. If anyone out there knows John Holdren, President Obama's science advisor, or knows how to contact him (with influence!) would you please point him in this direction?! Seriously, those in charge really should know that this is the only physically feasible definition of sustainability.