The Space-Based Solar Power study undertaken with the sponsorship of the U.S. Department of Defense’s National Security Space Office has continued to elicit significant interest. As noted in Part 1 of this series, the fundamental premise of this study was that the United States should lead the world in making use of space solar power as a primary means for achieving an energy-assured future based on renewable energy sources.
Needless to say, the validity of the study’s premise is not yet established. Significant technical, economic, and logistical issues related to beaming energy from space to the Earth still need to be addressed. Yet, the attractiveness of renewable, high-quality electrical energy delivered from space to terrestrial electrical power grids remains high.
Is strictly an economic comparison of space solar power vs. terrestrial alternatives still valid?
Some argue that while the needed technologies for building and operating space solar power systems may be resolvable, such space systems are unlikely to ever be economically competitive with terrestrial renewable and non-renewable alternatives. This argument, of course, presumes that terrestrial renewable and non-renewable energy sources will be sufficient in capacity and acceptable in terms of environmental impact to meet the world’s energy needs. If this presumption is true, then the economics of space solar power vs. terrestrial alternatives likely will become the basis of a go/no-go decision. Looking at the flip side of this argument, however, a different decision criterion emerges.
In Part 1 and Part 2 of this series, I developed the following list of the most important to least important desirable energy outcomes as part of a discussion of developing a rational U.S. energy policy.
- Energy sufficiency and energy availability
- Energy assuredness and energy affordability
- Energy acceptability
- Energy economic opportunity
If terrestrial renewable and non-renewable energy sources are sufficient to meet future energy needs, then energy policy can turn from ensuring “energy sufficiency and energy availability” to ensuring domestic “energy assuredness and energy affordability.” (See Part 1 for definitions.) However, if future needs cannot be met by terrestrial sources, then energy policy must remain focused on resolving this shortage. In this case, space solar power becomes a necessity. Comparative economic costs of space solar power vs. terrestrial energy sources, under these circumstances, are primarily useful in balancing investment in space solar power vs. terrestrial sources and for preparing the world’s economy to provide the needed economic resources.
Whether building space solar power systems is an economic decision or an essential need hinges on whether terrestrial energy sources can meet the world’s future needs. Currently, non-renewable hydrocarbon (NRH) fuels provide most of the world’s energy—about 85%. Despite escalating NRH prices and apparent production limits, many still believe that these current primary world energy resources are sufficient to sustain world needs beyond any required planning horizon. Discussions of a post-NRH world are dismissed as being irrelevant based on the assumption that new discoveries and/or recovery technology improvements will prevent these resources from being exhausted within any time period of concern. Advocacy of space solar power, therefore, must start with assessing the future of NRH supplies.
What are the known and projected world reserves of non-renewable hydrocarbon energy supplies of oil, coal, and natural gas?
Table 1: World Non-renewable Hydrocarbon Proved Recoverable Reserves
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Table 2: World Non-renewable Hydrocarbon All Recoverable Reserves
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These two tables reproduce information contained in the World Energy Council’s 2007 Survey of Energy Resources. The following notes explain how these tables were complied.
1. Proved recoverable reserves are what experts believe “can be recovered in the future under present and expected local economic conditions with existing available technology.” Table 1 shows these values for conventional oil, coal, and natural gas.
2. The reserves for the two forms of unconventional oil (natural bitumen and extra-heavy oil), included in Table 1, are not proved reserves. Rather, as discussed in the cited reference, these “reserves or probably reserves, generally with no further distinction, are quantities that are anticipated to be technically (but not necessarily commercially) recoverable from known accumulations.” As with most NRH fuels, the expected recoverable reserves of these two sources of oil are only a modest percentage of the known accumulations which, in some sources, is placed in the trillions of barrels for these two sources. (See the note below regarding oil shale in Table 2.)
3. Table 2 lists the additional recoverable reserves generally defined as the “resource additional to the proved amount in place that is of foreseeable economic interest. Speculative amounts are not included.” With the inclusion of these additional reserves, the total shown in Table 2 is an estimate of the total remaining NRH reserves that are recoverable at production levels needed to meet world needs. In this simple depletion model, when these reserves are exhausted, other energy sources will be needed.
4. Recovery of oil from oil shale is comparable to the recovery of the bitumen in that both are either mined or extracted using in situ heating to liquefy trapped hydrocarbons. The cited reference states: “Total world resources of shale oil are conservatively estimated at 2.8 trillion barrels.” However, unlike, natural bitumen or extra-heavy oil, the cited reference does not include estimates of useful reserves. The total 2.8 trillion barrels of oil from oil shale is included in Table 2, not to reflect the actual expected proved recoverable reserves, but to provide a massive additional source of NRH fuels that can be used to assess what impact this may have on world energy consumption. Essentially, the inclusion of the full amount of the oil shale covers uncertainties in the additional recoverable reserves of natural bitumen, extra-heavy oil, oil from oil shale, as well as increased production resulting from improved recovery methods for conventional oil, coal, and natural gas.
5. In their 1983 book, The Future of Oil, Odell and Rosing reach the conclusion that 5 trillion barrels is the likely amount of recoverable conventional and unconventional oil. The conventional and unconventional oil reserves, including oil shale, in the two tables total about 5 trillion barrels providing one indication that the total for oil used in this simple analysis is of the right magnitude.
What are the units of energy used?
A Q-BTU is a quadrillion (one billion million) British Thermal Units (BTU). It is used as the standard unit of measure by the U.S. government for comparing various energy sources. (See Part 4 for additional information on this topic.) The M-BTU, used later, is one million BTUs. It is a measure of per capita energy consumption. There are one billion M-BTUs in a Q-BTU. The advantage of using these two units is that they enable extremely large magnitudes of national and personal energy consumption to be described with numeric values that are easily comprehended.
Why are all of the NRH reserves combined into one total?
As a heat source and as a raw material for the chemicals industry, modern technology has made oil, coal, and natural gas interchangeable. Coal can be transformed into either a gas product to replace natural gas or a transportation fuel to replace oil. One major oil company is touting the conversion of natural gas into a liquid transportation fuel. As the reserves of oil are depleted, with a corresponding increase in price of the remaining oil, natural gas and coal production will likely increase to replace the dwindling supply. For the simple reserve depletion model used in this analysis, combining all reserves in one total and comparing this against the world’s total demand for NRH fuels was appropriate.
What will be the world’s demand for NRH fuels throughout the rest of the century?
Figure 1: U.S. and Non-U.S. Population Model Used
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The starting point for projecting the world’s demand for NRH fuels is to model the world’s population growth through the end of this century. Figure 1 shows both the U.S. and non-U.S. world population based on U.S. Census Bureau data to 2050 extrapolated to 2100. (Note: The Census Bureau projections through 2050 show a declining birth rate compared to the death rate. In the simple population model used, births equal deaths about 2080 for the non-U.S. population. In the U.S. however, the U.S. population is still growing because of the larger families and second and third generation births of the large influx of aliens in the last decade and the coming decades.)
Figure 2: U.S. and Non-U.S. Per Capita Energy Needs (M-BTU)
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The U.S. data is based on U.S. Energy Information Administration (EIA) data for 2004 and projected 2030 national energy consumption. Using the Figure 1 population model for the U.S., the per capita energy needs were computed for 2004 and 2030. These two data points then were used to extrapolate usage to 2100 using the same rate of change as projected from 2004 to 2030. (Note: A decline in per capita U.S. energy consumption through 2030 is projected by the EIA. This rate of decline was extended to 2100 where per capita consumption would be about 91% of current usage.)
The non-U.S. per capita energy consumption was based on international energy consumption data also reported by the U.S. EIA. The total world consumption was reduced by the U.S. consumption. The resulting value was divided by the non-U.S. population to arrive at an estimate of the non-U.S. per capita energy needs. As with the U.S. per capita energy needs, the trends from 2004 to 2030 were extrapolated to 2100.
In this model of non-U.S. per capita energy usage, by 2100 the non-U.S. per capita energy needs would be approximately 50% of the U.S. per capita energy needs. Currently, Japan and Western Europe per capita energy consumption is about 50% of that of the U.S. Hence, reaching a 50% value in 2100 represents a target where the per capita energy consumption and standard of living, outside of the U.S., would be comparable to that of Japan and Western Europe. The transformation of the world to a western standard of living would then be essentially complete.
Figure 3: Annual Future Energy Needs (Q-BTU)
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The U.S. and non-U.S. world per capita energy needs can be applied to the U.S. and non-U.S. populations to project the annual future U.S. and non-U.S. energy needs. Summing these two values yields the world’s total annual future energy need. This is shown in Figure 3, above. By 2100, the U.S. percentage of world energy use would fall from about 25% today to about 10%. (Note: If the rapid industrialization of China and India continues, the annual non-U.S. energy demand would be expected to increase more rapidly in the coming decades than shown in the above figure.)
In 2005, the world used about 455 Q-BTU. By 2100, this need will grow to about 1,500 Q-BTU, based on population growth and standard of living improvement. Hence, in 2100, the world will require about 3.4 X of the 2005 level of energy production.
Figure 4: World Total and Non-renewable Hydrocarbon Energy Needs (Q-BTU)
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From U.S. EIA and similar projections of future world energy use, the world is “still” expected to meet about 85% of its energy needs through 2030 with NRH fuels. Figure 4 extends this percentage through 2100 to predict that, should NRH fuels still be readily available and affordable, about 1,300 Q-BTU of NRH fuels will be needed. This is about 3.4X the NRH fuels consumed in 2005.
Figure 5: World Cumulative NRH Future Energy Needs vs. Reserves (Q-BTU)
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Using the annual world NRH fuels needs, shown in Figure 4, a simple resource utilization analysis can provide a ballpark estimate of when the NRH fuels may be exhausted. In Figure 5, the cumulative world need for NRH fuels is plotted. The projected NRH fuel reserves are then drawn down by this cumulative world need until the reserves are exhausted.
As seen in Figure 5, the current proved recoverable NRH reserves will be exhausted about 2060. This leaves an end-of-century NRH deficit of about 45,000 Q-BTU, which is equivalent to over 100 years of current NRH consumption.
For the “best case” using all proved and additional recoverable reserves—including the 3 trillion barrels of oil from oil shale—these reserves will be exhausted about 2084; slightly more than one generation after the first case. The end-of-century NRH deficit would be about 20,500 Q-BTU, which is equivalent to about 50 years of current NRH consumption.
What improved understanding does this model provide?
1. Growth in world per capita energy needs, spurred by expectations of an improving standard of living as a sign of political and economic success, will dramatically increase needed energy supplies throughout this century.
2. An energy planning horizon of 20-30 years, when non-renewable hydrocarbon fuels provide the vast majority of the world’s energy, does not adequately anticipate nor respond to the world’s energy situation this century.
3. By the end of the century, the world will need to fully replace nearly all production of non-renewable hydrocarbons with renewable or nuclear alternatives with a total world energy production capacity of 3-4 times that of today.
4. Undertaking a transformation from primarily non-renewable to primarily renewable/nuclear energy production is a necessity, if this model’s projections of NRH reserves are reasonably accurate.
5. The stage is now set to compare space solar power against terrestrial renewable and nuclear energy sources, not in terms of economics, but in terms of the magnitude of the energy needed to meet world needs.
Closing caveat:
This simple model did not look at the potential to make use of the frozen methane hydrates that are discussed as a future non-renewable hydrocarbon supply. Neither the technology needed to exploit these reserves on an industrial scale nor the environmental issues associated with such energy production are sufficiently understood to incorporate this into energy planning.
