My summary of LBNL scientist David Fridley’s 9-page Alternative Energy Challenges.
The showstopper is that the entire supply chain for alternative energy resources depend on fossil fuels, from mining basic (rare) metal ores, to fabrication, delivery, maintenance, and spare parts. Nor are any of these facilities capable of reproducing themselves using their own generated energy alone.
There are 2 main kinds of alternative energy:
- Substitutes for petroleum liquids: ethanol, biodiesel, biobutanol, dimethyl ether, coal-to-liquids, tar sands, oil shale), both from biomass and fossil feedstocks.
- Generation and storage of electric power: wind, solar photovoltaics, solar thermal, tidal, biomass, fuel cells, batteries.
Nature provided free solar energy over millions of years to convert biomass into conventional fossil fuels, which are energy-dense solids, liquids, and gases. All you need to do are extract and transport them.
Alternative energy depends heavily on engineered equipment and infrastructure for capture or conversion. However, the full supply chain for alternative energy, from raw materials to manufacturing, is still very dependent on fossil fuel energy.
Money and carbon footprint the wrong metrics to evaluate alternate energy
The public discussion about alternative energy is often reduced to an assessment of its monetary costs versus those of traditional fossil fuels, often in comparison to their carbon footprints. This kind of reductionism to a simple monetary metric obscures the complex issues surrounding the potential viability, scalability, feasibility, and suitability of pursuing specific alternative technology paths. Although money is necessary to develop alternative energy, money is simply a token for mobilizing a range of resources used to produce energy. At the level of physical requirements, assessing the potential for alternative energy development becomes much more complex since it involves issues of end-use energy requirements, resource use trade-offs (including water and land), and material scarcity.
The discussion is further complicated by political biases, ignorance of basic science, and a lack of appreciation of the magnitude of the problem facing societies accustomed to inexpensive fossil energy as the era of abundance concludes.
Alternate energy can not be easily substituted for oil, gas, or coal
It’s assumed alternative energy will seamlessly substitute for the oil, gas, or coal. Not true. Integrating alternatives into our current energy system will require enormous investment in both new equipment and infrastructure—along with the resources required for their manufacture—at a time when capital to make such investments has become harder to secure. This raises the question of the suitability of moving toward an alternative energy future with an assumption that the structure of our current large-scale, centralized energy system should be maintained. Since alternative energy resources vary greatly by location, it may be necessary to consider different forms of energy for different localities.
Scalability and Timing
Alternative energy must be supplied at a reasonable cost in the time frame and volume needed.
Many alternatives have been successfully demonstrated at a small scale (algae-based diesel, cellulosic ethanol, biobutanol, thin-film solar), but that doesn’t mean it will work when scaled up to a large facility.
Since alternative energy relies on engineering, manufacturing, and construction of equipment and manufacturing processes for its production, output grows in a step-wise function only as new capacity comes online, which in turn is reliant on timely procurement of the input energy and other required input materials. This difference between “production” of alternative energy and “extraction” of fossil fuels can result in marked constraints on the ability to increase the production of an alternative energy.
Often, newspaper reports of a breakthrough are accompanied by suggestions that such a breakthrough represents a possible “solution” to our energy challenges. In reality, the average time frame between laboratory demonstration of feasibility and large-scale commercialization is from 20 to 25 years. Processes need to be perfected and optimized, patents developed, demonstration tests performed, pilot plants built and evaluated, environmental impacts assessed, and engineering, design, siting, financing, economic, and other studies undertaken.
Ideally, an alternative energy form would integrate directly into the current energy system as a “drop-in” substitute for an existing form without requiring further infrastructure changes.
This is rarely the case, and the lack of substitutability is particularly pronounced in the case of electric vehicles. Although it is possible to generate the needed electricity from wind or solar power, the prerequisites to achieving this are extensive. Electric car proliferation at a meaningful scale would require extensive infrastructure changes including retooling factories to produce the vehicles, developing a large-scale battery industry and recharging facilities, building a maintenance and spare parts industry, integrating “smart grid” monitoring and control software and equipment, and of course, constructing additional generation and transmission capacity. All of this is costly. The development of wind and solar power electricity also requires additional infrastructure; wind and solar electricity must be generated where the best resources exist, which is often far from population centers. Thus extensive investment in transmission infrastructure to bring it to consumption centers is required. Today, ethanol can be blended with gasoline and used directly, but its propensity to absorb water and its high oxygen content make it unsuitable for transport in existing pipeline systems, and an alternative pipeline system to enable its widespread use would be materially and financially intensive.
While alternative energy forms may provide the same energy services as another form, they rarely substitute directly, and these additional material costs need to be considered.
Material Input Requirements
To make an alternative energy happen you need resources and energy, and if those are limited or expensive, that may limit how large or feasible it is. Especially if the technology depends on a rare earth element:
- Fuel cells require platinum, palladium, and other rare earth elements
- Solar photovoltaic technology requires gallium, and in some forms, indium
- Advanced batteries rely on lithium
- LED or organic LED (OLED) lighting (to save energy), requires the rare earths indium and gallium
Expressing the costs of alternative energy only in monetary terms obscures potential limits of the resource and energy inputs required. Successful deployment of a range of new energy technologies would substantially raise demand for a range of metals beyond the level of world production today.
Alternative energy production is reliant not only on a range of resource inputs, but also on fossil fuels for the mining of raw materials, transport, manufacturing, construction, maintenance, and decommissioning.
Currently, no alternative energy exists without fossil fuel inputs, and no alternative energy process can reproduce itself—that is, manufacture the equipment needed for its own production—without the use of fossil fuels. In this regard, alternative energy serves as a supplement to the fossil fuel base, and its input requirements may constrain its development in cases of either material or energy scarcity.
Modern societies expect that electrons will flow when a switch is flipped, that gas will flow when a knob is turned, and that liquid fuel will flow when the pump handle is squeezed. This system of continuous supply is possible because of our exploitation of large stores of fossil fuels, which are the result of millions of years of intermittent sunlight concentrated into a continuously extractable source of energy.
Alternative energies such as solar or wind power produce only intermittently as the sun shines or the wind blows. Even biomass-based fuels depend on seasonal harvests of crops.
Integrating these energy forms into our current system creates challenges of balancing availability and demand, and it remains doubtful that these intermittent energy forms can provide a majority of our future energy needs in the same way that we expect energy to be available today.
The key to evening out the impact of intermittency is storage; that is, developing technologies and approaches that can store energy generated during periods of good wind and sun for use at other times. Many approaches have been proposed and tested, including compressed air storage, batteries, and the use of molten salts in solar thermal plants. The major drawbacks of all these approaches include the losses involved in energy storage and release, and the limited energy density that these storage technologies can achieve.
Energy density refers to the amount of energy that is contained in a unit of an energy form. It can be expressed in the amount of energy per unit of mass (weight), or in the amount of energy per unit of volume. Energy density has greatly influenced our choice of fuels.
The conversion to the use of coal in the seventeenth and eighteenth centuries was welcomed because coal provided twice as much energy as wood for the same weight of material. Similarly, the shift from coal to petroleum-powered ships in the early twentieth century was driven by the fact that petroleum possesses nearly twice the energy density of coal, allowing ships to go farther without having to stop for refueling.
Even in a motor vehicle’s inefficient internal combustion engine, a kilogram of highly energy dense gasoline—about 6 cups—allows us to move 3,000 pounds of metal roughly 11 miles.
Low energy density requires larger amounts of material or resources to provide the same amount of energy as a denser material or fuel.
Many alternative energies and storage technologies are characterized by low energy densities, and their deployment will result in higher levels of resource consumption.
Gasoline has 92 times the energy density of a lithium battery in an electric vehicle (Lithium ion batteries can contain only 0.5 megajoules per kilogram (MJ/kg) of battery compared to 46 MJ/kg for gasoline). Advances in battery technology are being announced regularly, but they all come up against the theoretical limit of energy density in batteries of only 3 MJ/kg.
Energy Return on Investment
The complexity of our economy and society is a function of the amount of net energy we have available. “Net energy” is, simply, the amount of energy remaining after we consume energy to produce energy.
Consuming energy to produce energy is unavoidable, but only that which is not consumed to produce energy is available to sustain our industrial, transport, residential, commercial, agricultural, and military activities.
The ratio of the amount of energy we put into energy production and the amount of energy we produce is called “energy return on investment” (EROI). EROI can be very high e.g. 100:1, or 100 units of energy produced for every one unit used to produce it—an “energy source”), or low (0.8:1, or only 0.8 units of energy produced for every one unit used in production—an “energy sink”).
Society requires energy sources, not energy sinks, and the magnitude of EROI for an energy source is a key indicator of its contribution to maintenance of social and economic complexity.
Net energy availability has varied tremendously over time and in different societies. In the last advanced societies that relied only on solar power (sun, water power, biomass, and the animals that depended on biomass in the 17th and early 18th centuries, the amount of net energy available was low and dependent largely on the food surpluses provided by farmers. At that time, only 10-15% of the population was not involved in energy production.
As extraction of coal, oil, and natural gas increased in the 19th & 20th centuries, society was increasingly able to substitute the energy from fossil fuels for manual or animal labor, thereby freeing an even larger proportion of society from direct involvement in energy production. In 1870, 70% of the U.S. population were farmers; today less than 2%, and every aspect of agricultural production now relies heavily on petroleum or natural gas.
The same is true in other energy sectors: Currently, less than 0.5 percent of the U.S. labor force (about 710,000 people) is directly involved in coal mining, oil and gas extraction, petroleum refining, pipeline transport, and power generation, transmission, and distribution.
The challenge of a transition to alternative energy is whether such energy surpluses can be sustained, and whether the type of social and economic specialization we enjoy today can be maintained.
Indeed, one study estimates that the minimum EROI for the maintenance of industrial society is 5:1, suggesting that no more than 20 percent of social and economic resources can be dedicated to the production of energy without undermining the structure of industrial society.
In general, most alternative energy sources have low EROI values.
John Whims, Pipeline Considerations for Ethanol, Kansas State University Department of Agricultural Economics (Manhattan, KS: Kansas State University, August 2002),
Charles A.S. Hall, Robert Powers, and William Schoenberg, “Peak Oil, EROI, Investments and the Economy in an Uncertain Future,” in Biofuels, Solar and Wind as Renewable Energy Systems: Benefits and Risks, ed. David Pimentel (New York: Springer, 2008), 109-132.