- THE MAGAZINE
The ‘Energy Problem’
Currently proposed solutions to perceived energy problems of today’s global community too often focus on specific technologies and address only a small portion of the overall problem. The tendency to “silo-ize” these issues tends to produce revolutionary solutions to minor problems and to foster neglect of larger issues. The approach below attempts to deconstruct the “energy problem” into component parts to facilitate evaluation of proposed solutions and technologies in the larger context.
The “energy problem” is not a single problem but is an interconnected web of problems that have significant impact on the global environment and on the global economy. It actually can be seen as various disconnects between societal needs and the current energy infrastructure for meeting those needs.
In general, society does not need energy. It needs a greater number of actions performed and conditions met, the achievement of which requires energy. Each of these end uses requires conversion of local energy to some final form to enable their implementation. The energy problem can be seen as a set of problems, issues and challenges that span from the original source of energy along a path that transports, stores and converts energy, ultimately, to meet these end-use needs. Technical and policy solutions must be evaluated in light of this chain of supply, so that they address the whole problem and do not solve a problem related to one phase of the chain while creating greater difficulties for the rest of the chain or solve a local problem that ultimately is irrelevant to the overall problem.
Any examination of energy issues should recognize that human beings don’t need coal, oil, electricity or ethanol, but they need light at night, warmth in the winter, cool in the summer, the ability to move goods to market, elevators to go up and down, data to be processed, information to be transmitted, etc. Viewed in the context of actual human needs, conservation takes on a new meaning encompassing the traditional idea of efficiency improvement and reduction of losses, but also the new idea of “systemic conservation”—changing the means of meeting human needs to reduce or eliminate end-use energy consumption.
A common example of the former, “functional conservation,” would be the substitution of old-fashioned gas-guzzlers for more fuel-efficient hybrid automobiles. Systemic conservation, on the other hand, involves more fundamental changes in the way we meet human needs—not to diminish quality of life, but rather to reduce the inherent energy intensity of how we provide that quality of life. A good example of this latter process is community planning to enhance pedestrian access to amenities, such as shops, workplaces, schools and recreational facilities. This reduces or eliminates the need for automobiles for daily transportation, which is a more effective strategy than merely increasing automobile efficiency. Another example is the growing use of tele-presence for commercial interactions. This reduces travel requirements without reducing the effectiveness of the process, and arguably increases quality of life for those avoiding travel.
Systemic conservation should not be confused with “curtailment,” which implies a reduction in quality of life in pursuit of reduced energy consumption. Systemic conservation means re-envisioning the process by which human needs are met, either eliminating the end-use energy requirement to meet a human need or changing the process to minimize the need to provide that end-use. The analysis of how energy end-use requirements are determined by social organization and patterns of land use is an investigation that should precede the analysis of the infrastructure. Evaluation of any single infrastructure or component improvement should be made in the context of the entire energy supply chain.
Four basic characteristics of our energy supply system should be considered in the evaluation of proposed technical solutions or improvements:
- Conversion efficiency
- Sourcing overhead
- Energy transport
- Energy storage
This final conversion of energy to end use is likely only one in a chain of energy conversions that occur along the path from energy source to end use. Some conversion chains are simple, such as nuclear energy to heat to electricity and then to streetlights. Others are more complicated, such as solar electric to hydrogen to electric again through a fuel cell and then to the kinetic energy of a moving car. Some conversions facilitate storage, others facilitate transport, and final conversions are needed for the end use. The term “conversion efficiency” means not only the first law efficiency of the conversion, but also the environmental overhead of that conversion and its infrastructure and capitalization requirements. Evaluation of any technological “advance” related to a particular form of energy should recognize the relationship of that form to ultimate end uses, as well as the pathway and required conversions necessary to achieve that end use.
Perhaps the most significant conversion in the sequence is the conversion to the final end use. This conversion will have significant repercussions back up the supply chain. A consideration for this final conversion is the flexibility of the final energy form for conversion to multiple end uses. For example, we see very few No. 6-fuel-oil-fired flat screen televisions on the market. Improvements to a conversion process for a specific end use may have limited benefit if that conversion cannot also be applied to other end uses.
One final issue for energy conversion is the entropy change of the conversion. Many conversion processes have an enormous increase in entropy, as exemplified by the burning of natural gas to heat bathwater to 100 F. Heat at this low temperature can be had for free in any of a number of conversion processes that involve a much lower rise in entropy than simply converting a highly ordered energy form to low-grade heat. Given the large appetite of residential occupancies for low-grade heat, whether space heating or domestic hot water, a relatively large portion of U.S. energy consumption accrues from end uses that should be served by recovery of waste heat, with no use of source energy at all. A new method of evaluating energy conversion efficiency is called “exergy.” This method analyzes any conversion efficiency not only for the percentage of output energy to the percentage of input energy, but also for the quality of the output compared with the quality of the input. Examples of heat recovery sources that might have widespread potential include domestic refrigerators and air conditioners.
“Energy source” is a much-misused term in the discussion of society’s current energy problems. If one defines energy source as the introduction of “new” energy into the biosphere, we have very few energy sources. These may be defined as follows:
- Solar (including solar thermal, solar electric, bio-fuel, wind, wave and hydroelectric)
- Fossil (reintroduction of biofuel from outside the biosphere)
- Geothermal (true geothermal sourcing, not ground-coupled energy storage)
- Astronomical (tidal)
Hydrogen, however, is not a fuel source because it has to be extracted, isolated or purified before it can be converted to another form, such as electricity. The most common form of geothermal energy—boreholes used with heat pumps—isn’t a fuel source, but is a form of annual energy storage using the ground as a thermal battery. Most fuel sources, furthermore, require significant overhead to convert them to a form that is even initially usable. Crude oil is typically refined into different fractions, each of which is tailored to a specific initial conversion technology. Some of the raw source energy is consumed in the refining process, and some amount of air pollution is created. Coal, as an energy source, typically has significant environmental overhead for its acquisition, for concentration and transport, in addition to environmental overhead for its initial conversion to heat and then to electricity.
In addition, the energy form of most sources is typically not immediately usable for anything, but must be subjected to an initial conversion. Fossil fuels must oxidize, uranium must fission and solar must be concentrated for thermal supply or processed through the photoelectric effect to make electricity. Similarly, wind and tidal power must be converted from fluid flow to rotational kinetic energy. This initial conversion is usually the greater preponderance of capital expense necessary to exploit the source. It also typically represents much of the environmental impact of exploiting the resource.
An important characteristic of energy sources is control or dispatch of usable output. Typically, combustion processes with liquid or gaseous fossil fuels are very controllable, either with heat (boilers) or motive energy (engines) as the output. Solid fossil fuel conversion devices are less controllable, as are nuclear devices. Certain types of fuel cells are highly controllable, while others are not. Most renewable sources are controllable only insofar as their output can be dialed down from the peak available at any point in time. If the sun isn’t shining, or the wind isn’t blowing, these can’t be dialed up. These dispatch characteristics tend to group energy sources into one of three types:
- Base load source, which runs constantly at a fixed output
- Peaking source, which is modulated constantly to conform to the difference between the base load and the demand curve
- Expediential source, which provides energy whenever it is available
The tradeoffs among the sources are clear. Base load sources should be very efficient with low sourcing overhead, trading these characteristics for their lack of controllability. They may be expected to meet the preponderance of the load over time. Peaking sources trade efficiency for controllability. They are used only as needed to meet peaks and for load following. Expediential sources would have the lowest sourcing overhead, justifying the inconvenience of adapting to their availability and the expense for providing backup when they are unavailable.
While there has been much emphasis placed on the environmental impacts of the initial conversion process of some energy sources, especially fossil fuels, there has been little public discussion of the environmental impacts of procurement. Coal has had the most exposure here, with respect to the impact of mountaintop removal and the impacts of the initial conversion (acid rain, heavy metal pollution, particulates, etc.).
However, other sources should receive the same level of scrutiny in a scientific, agenda-free context. Significant research is needed to analyze the source overhead of newly proposed or available energy sources. The sourcing overhead differences between food-sugar-sourced ethanol and cellulosic ethanol should be understood. The differences between biological (fermentation related) and thermal (pyrolytic) processes for rendering hydrocarbon waste into bio-fuel should be examined. These should be compared to the sourcing overhead for “fracking” natural gas from shale, and all should be compared to the real overhead of fossil fuel extraction from virgin land.
The most publicized environmental impact of the world’s most utilized energy source is the production of greenhouse gases from the combustion of fossil fuels. Climate scientists are almost unanimous in their determination that increased human utilization of this energy source causes the rising atmospheric carbon dioxide concentrations that are driving climate change. Realistic reforms to the global energy consumption picture must address reduction in fossil fuel combustion while permitting a global elevation of human quality of life. Basically, reform strategies must address getting more “bang” for the fossil fuel “buck.” Achieving this end means addressing all aspects of the energy supply-consumption chain, not just the efficiency of the initial source energy conversion.
Check back in the February issue of EDC for Part II of the article, “A discussion of energy storage and energy Transport.”