determined by the GDP. In 1950, 0.35 toe was required for each $1,000 GDP (1990 U.S. dollars). By 2000 this had fallen to 0.31, and extrapolation suggests that by 2050 it could be in the range of 0.12 - 0.18. This quantity is called the “energy intensity,” and for several years it has been decreasing at a rate of 1% per annum. EPRI's roadmap proposes a target of 2% per year.
The next issue is global population. This last year, the world's population exceeded 6 billion. By 2050, extrapolations suggest that this might rise as high as 10 billion, although earlier chapters have suggested that the most recent estimates may be somewhat less than this.
When these numbers are combined and the retirement of most of the world's current generating capacity by 2050 is considered, this goal is equivalent to adding 10,000 GW of generating capacity. This means building 200,000 MW of capacity per year, which at current costs represents investing something like $100 billion to $150 billion per year. While this is undoubtedly a large sum, it is less than 0.3% of the world GDP, and as EPRI's president, Kurt Yeager, says, “It is less than the world currently spends on cigarettes!”
The global efficiency of the production of electricity from the current fuel mix averages about 32%, which the EPRI roadmap proposes should be increased to 50% by 2050. Another important consideration is the “capacity factor” of a generating plant—that is, the fraction of the time that a given plant is in fact generating electricity. The overall global average is 50% for central station generation. The EPRI roadmap proposes that this be increased to 70% by 2050. However, further careful evaluation needs to be done to ensure that the manufacturing capabilities exist to meet these demands.
This gives an idea of the magnitude of the problem facing us over the next 50 years. In this chapter, I talk only about generation of electricity. I do not discuss the problem of delivery from the point of generation to the final user, although this too is a major issue.
Now, from the point of view of the workshop, the question is, How do we generate this electricity, and how does this contribute to the present and future production of anthropogenic greenhouse gases, specifically CO2?
Let us review the situation in the United States. In the United States, the carbon emissions in 1995 were 524 MtC (million tonnes of carbon equivalent) for buildings (heating, lighting, and so forth), 630 MtC for industry, and 473 MtC for transportation. Essentially all of the transportation emissions came from petroleum, while 123 MtC of the buildings' emissions came from natural gas, 42 MtC from petroleum, and 355 MtC from electricity. For the industry total, 177 MtC came from electricity and the remainder from a variety of sources. In terms of primary fuels, the numbers were 628 MtC from petroleum, 319 MtC from natural gas, and 533 MtC from coal. As a first approximation, therefore, the three major categories made equal contributions to carbon emissions.
For transportation, the sources of CO2 are many small, widely dispersed, and mobile entities. They need a storable, high-energy-density fuel. Petroleum-derived fuels fit these requirements very well. Removal of the CO2 emissions from internal combustion engine exhausts will present a significant problem, and the costs are likely to be socially and economically unacceptable. In the longer range, hybrid automobiles, which are now being introduced, may help. Electric vehicles might have the effect of transferring CO2 production from the vehicle to an electric utility generator. Fuel cells, particularly with hydrogen fuel, are the ultimate goal, but they are a few years away.
The most easily addressable source of CO2 is from the generation of electric power, since there are a much smaller number of very large stationary sources. That is the primary topic of this chapter. As pointed out above, one factor of importance here is the increasing “electrification” of primary energy sources with time, and this pattern is reflected in the rest of the world. For example, in much of the world, mass transportation systems are increasingly powered by electricity, and (as indicated above) recent research has been addressing the electrification of personal transportation, although there are still significant barriers to achieving systems that are acceptable to the public.