In a years time, the Earth intercepts solar energy in an amount that far exceeds (by many
thousands of times) the quantity of energy that people consume at the global scale. Solar energy
is, in fact, the ultimate origin for most of the other resources people use to generate energy, such
as fossil fuels, biomass (non-fossil organic materials), and all water- and windpower. All of these
resources are essentially storehouses of solar energy, in one form or another. While these
resources are very important to current and future energy generation, the direct capture and use
of solar energy is thought by some to be the best candidate to satisfy people's future energy needs
while minimizing our impact on the global environment.
Sunlight can be captured in many different ways and the solar energy it provides can be used to
meet a variety of energy needs. In short, solar energy can be used to generate electricity, heat
water, and heat, cool, and light buildings.
In general, solar energy can be used directly or indirectly, but the technologies involved in
capturing or harnessing sunlight and its energy are many and complex. I will, therefore, only
introduce the most common technologies: photovoltaics, passive solar, concentrating solar
power, and solar heating and cooling.
Photovoltaics (PV; also called "solar cells")
. PV systems are used to convert sunlight (solar
energy) directly into electricity. A PV cell acts as a solar collector and is made of
semiconducting material that absorbs sunlight. As the sunlight is absorbed, it disturbs electrons
and knocks them loose from atoms. Once loose, the electrons flow through the PV material and
produce electricity. PV arrays (groups PV cells) can be set-up to produce electricity for
individual homes, buildings, or entire power plants. A large quantity of PV arrays are required,
however, to produce electricity at the power plant scale.
A photovoltaic system co-located with nuclear power operation in Sacramento, CA. As the cost of
photovoltaics continues to decrease, the technology becomes increasingly competitive for utilities. This 2-
megawatt plant produces enough power to serve 660 Sacramento-area homes. The 1600 modules are spread
across an 8094 square meter field in this very sunny region of California. Cost-competitive, utility-scale PV
systems for intermediate peaking applications is one ultimate goal of stakeholder collaborations.
. Solar energy doesn't always need to be collected and converted to some other
form to be used in a home/building. It is possible to design homes and buildings to exploit solar
energy by passive means for heating, cooling, or daylighting. Passive solar technologies often
involve large, south-facing windows, flooring or wall materials that absorb solar energy during