Proponents of solar power have calculated what it would take for a sizable fraction of the world’s energy to be provided by sunlight. Jacobson and Delucchi [5] esti­mated that the world will need 16.9 TW (terawatts or billions of kilowatts) of energy by 2030. If we were to use only Water, Wind, and Sun power, only 11.5 TW would be needed, since these sources can generate electricity directly, without going through a thermal cycle. This amount can be generated by WWS in the proportion shown in Fig. 3.29. Water energy (1.1 TW) is to come from hydro­electric and geothermal plants, and from tidal turbines yet to be developed. Wind power (5.8 TW) will come from 3.8 million wind turbines and from machines driven by ocean waves, which arise from wind. Solar power (4.6 TW) will require 89,000 300-MW power plants and 1.7 billion rooftop collectors. These three sources would have to work together to cover the daily and annual fluctuations. More than 99% of these numerous installations have still to be built.

Fig. 3.29 Power that must be provided by water, wind, and solar sources by 2030 to supply the entire world’s needs

The solar part of this has been evaluated in great detail by Fthenakis et al. [6]. They estimate that plants located in the Sahara, Gobi, or southwestern US deserts can produce photovoltaic electricity at $4/W and $0.16/kWh. This includes the entire plant, not just the panels themselves. Since residential electricity costs closer to $0.12/kWh than the average of $0.10/kWh, and since there are rebates, the cost of solar is already competitive with standard sources. The authors point out that electricity storage and transmission have still to be developed, and this has to be done using conventional fuels, since solar energy is still small. However, the energy payback time is of the order of two years (as will be shown here later); and once solar grows to 10% or more of total energy, further development could be done without the use of fossil fuels. These studies seem to be realistic, since the authors point out that there are many problems that still need to be treated in detail: the availability of rare materials, the sites for compressed-air storage, the transmission problem, the commercial problems in scaling up, and ecological damage to land and wildlife. If 10% solar cell efficiency is achieved and 2.5 times more land area than cell area is required, then 42,000 km2 of desert area could supply 100% of the electricity for the USA (if it can be stored and transported). This seems like a large area, but it is less than half the area of the lakes produced by dams for hydro in the USA, and solar produces 12 times the energy. Lakes like Lake Mead have drastically changed the landscape. The change may have been welcomed by boaters, but not by the fish.

At this point, it is becoming clear that WWS (water, wind, and solar) sources have some large problems to overcome: storage of intermittent energy; transmis­sion over large distances; use of large land areas; ecological damage to land and wildlife; unsightly encroachment on the landscape and seascape; and legal, politi­cal, and environmental objections to these intrusions. Overcoming these obstacles may take longer than developing compact power centers, like nuclear fusion, which avoids these problems. Replacing the power core of a coal or nuclear plant with a fusion reactor would retain the electrical gen­erators, transmission lines, and real estate already in place. There would be no noticeable difference to the public except that all CO

2

emissions and fuel costs would be eliminated. The great advantage of WWS, however, is that feasibility is already proven; and further improvements in tech­nology can be tested on a small scale, privately financed by industry. By contrast, each step in the development of fusion is so costly that the expense is best shared among nations.