The Power and Transportation Future - Hydrogen and Fuel Cells: Advances in Transportation and Power - page 277

sunlit area. However, an SPS also requires a large ground structure. The
rectenna on the ground is much larger than the area of the solar panels in
space. The ground-only solar array would have the advantages of costing
much less to construct and requires no significant technological advanc-
es.
But, such a system has its disadvantages. A terrestrial solar station
intercepts only one third of the solar energy that an array of equal size
could intercept in space, since no power is generated at night and less
light strikes the panels when the Sun is low in the sky.
Some form of energy storage is needed to provide power at night,
such as hydrogen or pumped storage hydroelectricity. Weather conditions
would also interfere with power collection, and can cause greater wear
on the solar collectors than the environment of Earth orbit. A sandstorm
could cause much damage. Beamed microwave power can send the pow-
er near to the area where it is needed. A solar generating station on Earth
may need to provide power to the other areas, where demand is relatively
high. Ground-based power can be used on-site to produce hydrogen for
transportation in a hydrogen economy.
Advanced construction techniques would make the SPS concept
more economical and could make a ground-based system more economi-
cal. Many SPS plans are based on building the framework with automated
machinery supplied with raw materials, typically aluminium. Such a sys-
tem could also be used for Earth stations.
The use of microwave beams to heat the oceans has also been stud-
ied. Some research suggests that microwave beams would be capable of
deflecting the course of hurricanes. NASDA (Japan's national space agen-
cy) has been researching this area and plans to launch an experimental sat-
ellite of 10-kW to 1-MW. Japan plans to assemble a space-based solar array
by 2040.
THE FUTURE FOR ENERGY
Shell Energy has conducted extensive future energy studies. Shell
has made major investments in renewable energy and hydrogen and has
been a leader in reducing greenhouse gas emissions. From 1975 to 2000,
the world gross domestic product (GDP) more than doubled while prima-
ry energy use grew by almost 60%. From 2025 to 2050 in one Shell future
vision, the GDP almost doubles, but primary energy use grows by only