Whither Energy?

One of the most important concepts to grasp in any discussion of energy is "net energy gain." This is simply the usable energy released by a process less the energy consumed in the production of that energy. A century ago, petroleum extraction yielded about 50 barrels of oil for each barrel used to find and extract the oil. Today, each barrel of oil used to find and extract oil yields only about five barrels of oil, and this number is falling rapidly towards unity for new fields. It makes no sense to drill for oil in any field where the energy recovery ratio is unity or below, as such a field would produce no net energy gain.

Any prospective energy system must be measured against its net energy gain. Under reasonably favorable conditions, wind energy and hydropower yield significant life-cycle net energy gains. Photovoltaics ("solar cells") have improved considerably in their net energy picture, from well below unity in the beginning to somewhat over one year to energy break-even. (The picture is cloudy, because no one really knows how long a cell will be able to produce electricity.) This technology therefore has the capability to deliver large net energy gains today.

Simple solar collection systems offer net energy gains for space- and water-heating in most areas of the world, and these systems should probably be deployed on a large scale as soon as possible. This has already been done in parts of the tropics, where it is clearly cheaper to provide domestic hot water from solar energy than from fossil fuels.

There are a myriad of other potential energy systems, such as energy from biomass, seawater temperature differences, geothermal energy, wave energy, and tidal energy. Some of these systems have already been demonstrated to work; others are still only prospects. Unfortunately, the systems that have been shown to work can only be applied on a limited scale, and the net energy picture for some of these approaches is still unclear.

No discussion of net energy gain is complete without mention of the often- touted "hydrogen economy." While hydrogen will doubtless eventually replace natural gas and petroleum in most of their current uses, this begs the question of where the hydrogen will come from. Hydrogen is not a "primary fuel" because it does not exist in free form in nature. Hydrogen is today produced using natural gas and coal, but only with a large net energy loss. In the future, hydrogen will probably be produced by electrolyzing water, which requires large amounts of electricity in a process that also causes a large net energy loss. The fundamental question thus becomes how hydrogen can be produced using sustainable energy sources. Almost any form of renewable energy can be used, directly or indirectly, to produce hydrogen, so the matter turns on the question of ultimate capacity of the sustainable energy infrastructure, a matter that cannot now be answered with any precision or certainty. We can, however, be sure that the hydrogen-powered economy is no panacea.

Nuclear fusion is a possible hope for the future, but 50 years of exhaustive, expensive research have not come close to net energy gain. (The most recent efforts have reached thermal break-even, but this is still a very long way from net energy gain.) Nikos A. Salingaros has demonstrated mathematically that the current torroidal confinement systems being pursued in the USA can never work. He has not ruled out the possibility that inertial confinement systems could yield a net energy gain, but not much work is being done in this area. I believe that it is foolish to base any energy policy on the hope that fusion may some day become a safe, practical, net producer of energy. Furthermore, nuclear fusion is far from being free of high-level nuclear wastes, a point not often mentioned by its proponents.

Finally, we must turn to one of the cornerstones of the Bush energy proposal: massive new construction of nuclear power plants. Historically, nuclear power plants have been net producers of energy in spite of the considerable electrical energy consumed in the necessary enrichment of uranium. Nuclear power faces two huge hurdles (leaving aside the widespread public revulsion for this technology). The first is the question of nuclear waste disposal and the second is safety.

The nuclear waste disposal issue is complex and has so far proven intractable. However, proposals have been made to separate nuclear wastes into short-lived isotopes, those which decay to safe levels within a few hundred years, and long-lived isotopes, some of which remain dangerous for a million years. The long-lived isotopes are almost entirely the so-called "trans-uranic elements," those heavier than uranium. These elements can be fissioned in reactors designed specially for the purpose, which causes most of the radioactive material to break into short-lived isotopes (and releasing useful amounts of energy in the process). The long-lived isotopes produced in these reactors can be recycled into other reactors, so that the amount of high-level radioisotopes that need to be stored for very long periods of time can probably be reduced below the amount of currently-existing high-level waste, thus actually helping to solve the existing waste disposal problem. This technology is only prospective - it has never been demonstrated, and the difficulties are not yet understood, but further research is clearly indicated.

Nuclear safety has been, with the glaring exception of Chernobyl, fairly good. We now have more than 30 years of experience with commercial nuclear power generation, and it certainly appears to be a safer way to generate electricity than burning coal, the mainstay of the Bush proposal. We can assume that no more graphite-pile reactors (the Chernobyl type) will ever be built. The various types of water-moderated reactors used in North America, Europe, and Japan would appear to be comparatively safe even in their current rather primitive form.

The world now possesses a considerable quantity of weapons-grade plutonium, a substance that we would dearly love to be rid of. There is no way to permanently and definitively dispose of this material except to fission it in nuclear reactors. Given the need to dispose of the plutonium, coupled with the need for enough energy to bridge the gap while developing a fully sustainable energy infrastructure, it may be sensible to develop advanced reactor technologies that would improve the safety of nuclear power by at least an order of magnitude and to develop the fuel recycling systems that can largely eliminate the high-level waste disposal problems. This would permit us to dispose of the existing stock of plutonium and also allow the construction of uranium reactors to provide energy during the most difficult period of the transition, which is likely to be between 20 and 50 years in the future.

I do not believe that current nuclear generation systems should be replicated. I propose that the US government embark upon a research program to develop greatly improved nuclear technologies over a 15 or 20 year period. The waste disposal question must be answered and newer, safer reactors designed. If these systems are successfully developed, they can become one of the bridge energy sources we will need to build a sustainable energy infrastructure.

We must never forget that the future of nuclear fission is also limited - the supply of uranium is not large, and a significant fraction of the total supply has already been mined. The breeder reactor has been abandoned as a safe, practical method for converting non-fissile uranium into fissile uranium. It is possible that more workable approaches could be developed, but we should make no plans on this basis until the technique is proven, and perhaps not even then. Above all, we should not use nuclear energy to postpone the day when we begin the difficult work of providing our civilization with a sustainable energy infrastructure. We should conserve first, and only add additional nuclear power capacity as a stopgap during the most difficult period of the changeover.

Read Part One: Fossil Fuels Forever?
Read Part Three: Making a Long-Term Plan