Now in the houses with a south
aspect, the Sun's rays penetrate into the porticoes in the winter, but in
summer the path of the Sun is right over our heads and above the roof so that
there is shade If, then, this is the best arrangement we should build the south
side loftier to get the winter sun and the north side lower to keep out the cold
-Socrates as quoted by Xenophonin in
Geomancy- the power of the Earth
Geomancy is the power that resides in the earth
itself. Many ancient cultures had beliefs that adhere to this and their
architecture reflected it.
Buildings are improved when their design defers
to an order of the earth greater than the building itself. Solar energy is
not a new concept , but an ancient one whose time is now. Our planet has
limited resources that are being misused on an ongoing basis. Before Man
harnessed the many forms of fossil fuels to heat and cool, design and location
was a greater concern. Today the concern is how many houses can be squeezed
onto a plot of land with no consideration of the natural resource that is
available to all...
By using a passive solar design a home owner can save
on average 60% of their energy costs with no additional
cost in construction. Add an active photovoltaic system and the energy cost
goes almost to zero. There is no meter attached to the sun.....it is FREE power for the people!
American Sun Symbol
people of the Earth have a reliance on fossil fuels, natural gas, coal and oil, that are
harmful to the environment. Conventional energy sources - oil, coal, natural
gas, and nuclear power - are accompanied by problems of air and water pollution,
resource depletion, and the greenhouse effect, all of which are becoming
increasingly unacceptable and unaffordable. We have a tremendous opportunity in harnessing
the power for the people
How Does Solar Power Work?
We have always used the energy of
the sun as far back as humans have existed on this planet. As far back as 5,000
years ago, people "worshipped" the sun. Ra, the sun-god, who was
considered the first king of Egypt. In Mesopotamia, the sun-god Shamash was a
major deity and was equated with justice. In Greece there were two sun deities,
Apollo and Helios. The influence of the sun also appears in other religions -
Zoroastrianism, Mithraism, Roman religion, Hinduism, Buddhism, the Druids of
England, the Aztecs of Mexico, the Incas of Peru, and many Native American
Solar energy technologies harness
the sun's energy for practical ends. These technologies date from the time of
the early Greeks, Native Americans and Chinese, who warmed their buildings by
orienting them toward the sun.
Spruce Tree House cliff dwelling at Mesa Verde
most of history people considered the power of the sun when designing
buildings. After the industrial revolution the practice of utilizing the
sun was abandoned.
societies such as the Greek, Roman, Native American, Celtic all revered the sun
and put its thermal - or heat - energy to work. Ancient cities were
positioned to use the sun for it's warmth in the winter, and to be shaded
from the heat in the summer.
Americans developed and refined many building forms and construction
methods that we can learn from today.
Spruce Tree House cliff dwelling
at Mesa Verde
The Anasazi of the southwest created
houses that through their design stayed warm in the winter and yet cool in
their hot desert summers. At the ancient Indian sites of Mesa Verde and
Pueblo Bonito,"pretty village" in Spanish, the ruins reveal houses ingeniously laid out to maximize
their solar energy gain by following the cycles and angles of the sun.
Ancient Romans and Greeks both had their own "energy crisis" in
the b.c. time period.
They used all of the wood surrounding their cities and
did not plan ahead by planting more trees. They had to get wood from far
away sources. The ancient Greeks planned whole cities in Greece and Asia
Minor such as Priene, to allow every homeowner access to sunlight
during winter to warm their homes. By running the streets in a
checkerboard pattern running east-west and north-south pattern every home
could face south, permitting the winter sun to flow into the house
throughout the day.
bath houses in the first to fourth centuries A.D. had large south-facing windows
to let in the sun's warmth.
Baths of Caracalla
Roman Empire had solar access laws, and the Doctrine of Ancient Lights protected
landowners' rights to light in nineteenth-century Britain. Several dozen U.S.
communities adopted solar access regulations in the 1970s and early 1980s in
response to the energy crisis.
Solar energy-power from the sun-is
free and inexhaustible. This vast, clean energy resource represents a viable
alternative to the fossil fuels that currently pollute our air and water,
threaten our public health, and contribute to global warming.
Energy is a clean
environmentally friendly source of power. Now is the time to take advantage of
this abundant resource.
Power on Earth
the energy stored in Earth's reserves of coal, oil, and natural gas is
matched by the energy from just 20 days of sunshine.
In 40 minutes of daylight The
SUN releases upon The Earth the amount of energy
that is consumed by the entire population of the planet in ONE YEAR
day more solar energy falls to the Earth than the total amount of energy the
planet's 6 billion inhabitants would consume in 27
we harness about 1%
of this energy
Photovoltaic energy is the
conversion of sunlight into electricity through a photovoltaic (PVs) cell,
commonly called a solar cell. A photovoltaic cell is a nonmechanical
device usually made from silicon alloys.
Sunlight is composed
of photons, or particles of solar energy. These photons contain various
amounts of energy corresponding to the different wavelengths of the solar
spectrum. When photons strike a photovoltaic cell, they may be reflected,
pass right through, or be absorbed. Only the absorbed photons provide
energy to generate electricity. When enough sunlight (energy) is absorbed
by the material (a semiconductor), electrons are dislodged from the material's
atoms. Special treatment of the material surface during manufacturing
makes the front surface of the cell more receptive to free electrons, so the
electrons naturally migrate to the surface.
When the electrons leave their
position, holes are formed. When many electrons, each carrying a negative
charge, travel toward the front surface of the cell, the resulting imbalance of
charge between the cell's front and back surfaces creates a voltage potential
like the negative and positive terminals of a battery. When the two surfaces are
connected through an external load, electricity flows.
The photovoltaic cell is the
basic building block of a PV system. Individual cells can vary in size from
about 1 cm (1/2 inch) to about 10 cm (4 inches) across. However, one cell only
produces 1 or 2 watts, which isn't enough power for most applications. To
increase power output, cells are electrically connected into a packaged
weather-tight module. Modules can be further connected to form an array. The
term array refers to the entire generating plant, whether it is made up of one
or several thousand modules. As many modules as needed can be connected to form
the array size (power output) needed.
The performance of a photovoltaic
array is dependent upon sunlight. Climate conditions (e.g., clouds, fog) have a
significant effect on the amount of solar energy received by a PV array and, in
turn, its performance. Most current technology photovoltaic modules are about 10
percent efficient in converting sunlight with further research being conducted
to raise this efficiency to 20 percent.
Power 101Video - how does sunlight turn into electricity
The pv cell was discovered in
1954 by Bell Telephone researchers examining the sensitivity of a properly
prepared silicon wafer to sunlight. Beginning in the late 1950s, pvs were used
to power U.S. space satellites. The success of PVs in space generated commercial
applications for pv technology. The simplest photovoltaic systems power many of
the small calculators and wrist watches used everyday. More complicated systems
provide electricity to pump water, power communications equipment, and even
provide electricity to our homes.
Photovoltaic conversion is useful
for several reasons. Conversion from sunlight to electricity is direct, so that
bulky mechanical generator systems are unnecessary. The modular characteristic
of photovoltaic energy allows arrays to be installed quickly and in any size
required or allowed.
Also, the environmental impact of
a photovoltaic system is minimal, requiring no water for system cooling and
generating no by-products. Photovoltaic cells, like batteries, generate direct
current (DC) which is generally used for small loads (electronic equipment).
When DC from photovoltaic cells is used for commercial applications or sold to
electric utilities using the electric grid, it must be converted to alternating
current (AC) using inverters, solid state devices that convert DC power to AC.
Historically, pvs have been used at remote sites to provide electricity.
However, a market for distributed generation from PVs may be developing with the
unbundling of transmission and distribution costs due to electric deregulation.
The siting of numerous small-scale generators in electric distribution feeders
could improve the economics and reliability of the distribution system.
Photovoltaic (or PV) systems
convert light energy into electricity. The term "photo" is a stem from
the Greek "phos," which means "light." "Volt" is
named for Alessandro Volta (1745-1827), a pioneer in the study of electricity.
"Photo-voltaics," then, could literally mean
"light-electricity." Most commonly known as "solar cells,"
PV systems are already an important part of our lives. The simplest systems
power many of the small calculators and wrist watches we use every day.
are one of the fastest growing solar energy technologies. Photovoltaic
devices, commonly called solar cells or modules, use semiconductor
material to directly convert sunlight into electricity. Solar cells have
no moving parts-power is produced when sunlight strikes the
semiconductor material and creates an electric current.
Photovoltaic (PV) cells are made primarily of silicon,
the second most abundant
element in the earth's crust, and the same semiconductor
material used for computers. When the silicon is combined with one or more other
materials, it exhibits unique electrical properties in the presence of sunlight.
Electrons are excited by the light and move through the silicon. This is known as the photovoltaic
effect and results in direct current (DC) electricity. PV modules have no moving
parts, are virtually maintenance-free, and have a working life of 20 - 30
PV cells were originally developed
for use in space, where repair is extremely expensive, if not impossible. PV
still powers nearly every satellite circling the earth because it operates
reliably for long periods of time with virtually no maintenance.
Low Operating Costs
PV cells use the energy from
sunlight to produce electricity-the fuel is free. With no moving parts, the
cells require little upkeep. These low-maintenance, cost-effective PV systems
are ideal for supplying power to communications stations on mountain tops,
navigational buoys at sea, or homes far from utility power lines.
Because they burn no fuel and have
no moving parts, PV systems are clean and silent. This is especially important
where the main alternatives for obtaining power and light are from diesel
generators and kerosene lanterns. As we become more aware of "greenhouse
gases" and their detrimental effects on our planet, clean energy
alternatives like PV become more important than ever.
The three basic types of solar
cells made from silicon are single-crystal, polycrystalline, and amorphous.
cells are made in long cylinders and sliced into round or hexagonal wafers.
While this process is energy-intensive and wasteful of materials, it
produces the highest-efficiency cells-as high as 25 percent in some
laboratory tests. Because these high-efficiency cells are more expensive,
they are sometimes used in combination with concentrators such as mirrors or
lenses. Concentrating systems can boost efficiency to almost 30 percent.
Single-crystal accounts for 29 percent of the global market for PV.
cells are made of molten silicon cast into ingots or drawn into sheets, then
sliced into squares. While production costs are lower, the efficiency of the
cells is lower too-around 15 percent. Because the cells are square, they
can be packed more closely together. Polycrystalline cells make up 62
percent of the global PV market.
silicon (a-Si) is a radically different approach. Silicon is
essentially sprayed onto a glass or metal surface in thin films, making the
whole module in one step. This approach is by far the least expensive, but
it results in very low efficiencies-only about five percent.
How Small Solar
Electric Systems Work
Solar electric systems, also
known as photovoltaic (PV) systems, convert sunlight into electricity.
Solar cells-the basic building
blocks of a PV system-consist of semiconductor materials. When sunlight is
absorbed by these materials, the solar energy knocks electrons loose from their
atoms. This phenomenon is called the "photoelectric effect." These
free electrons then travel into a circuit built into the solar cell to form
electrical current. Only sunlight of certain wavelengths will work efficiently to
create electricity. PV systems can still produce electricity on cloudy days, but
not as much as on a sunny day.
The basic PV or solar cell
typically produces only a small amount of power. To produce more power, solar
cells (about 40) can be interconnected to form panels or modules. PV modules
range in output from 10 to 300 watts. If more power is needed, several modules
can be installed on a building or at ground-level in a rack to form a PV array.
About 10-20 PV arrays can provide enough power for a household.
PV arrays can be mounted at a
fixed angle facing south, or they can be mounted on a tracking device that
follows the sun, allowing them to capture the most sunlight over the course of a
Because of their modularity, PV
systems can be designed to meet any electrical requirement, no matter how large
or how small. You also can connect them to an electric distribution system
(grid-connected), or they can stand alone (off-grid).
Edmund Becquerel, a French physicist observed the photovoltaic effect.
Selenium PV cells were built that converted light in the visible spectrum into
electricity and were 1% to 2% efficient. Light sensors for cameras are still
made from selenium today.
In the early 1950's the
Czochralski meter was developed for producing highly pure crystalline silicon.
In 1954 Bell Telephone Laboratories produced
a silicon PV cell with a 4% efficiency and later achieved 11%
In 1958 the US Vanguard space satellite used
a small (less than one watt) array to power its radio. The space program
has played an important role in the development of PV's ever
During the 1973-74 oil embargo the US Department
of Energy funded the Federal Photovoltaic Utilization Program, resulting
in the installation and testing of over 3,100 PV systems, many of which are
in operation today.
The 1970s through the 1990s have seen a relative
disinterest in solar power with majority ownership of many United States
PV manufacturers transferring to German and Japanese interests
Passive Solar Energy
Passive solar energy
systems require no energy to operate and are an intrinsic part of the home
design. Passive systems add little additional cost, operate with almost no
supervision and require little or no maintenance. The basic elements of all
passive systems are south-facing windows and internal thermal mass. Solar
heating is simply sunlight entering the house that is absorbed and converted
into heat energy which is later released inside the house as it cools. A passive
solar home is one where the design and construction of the home itself is made
to keep the house naturally warm in the winter using the sun's energy. The
design should also keep the house naturally cool during the summer
The sun is a very
intense source of energy. When designed properly, a passive solar home can
experience heating costs that are 80% to 95% lower than for the average home.
Air conditioning costs can also be reduced to a minimal level.
The basic idea of
passive solar home design is to invite sunlight into the house during the
winter, and once it is inside the home, to hold it in and store it until
nighttime. Conversely, the sun needs to be kept out during the summer.
The Solar Resource
Solar Power Capacity
In kWh/square foot per year
The solar irradiance figures indicate the average
annual energy available per square metre
When sunlight reaches the Earth,
it is distributed unevenly in different regions. Not surprisingly, the areas
near the equator receive more solar radiation than anywhere else on Earth.
on the map are average isolation in units of kilowatt-hours per square meters
per day (sun-hours) for a surface of latitude tilt for December. These values
typically represent the "worst case" solar resource month.
Source: Sandia National Laboratories
varies with the seasons, as the rotational axis of the Earth shifts
to lengthen and shorten
days with the changing seasons. For example, the amount of solar energy falling per square
meter on Yuma, Arizona, in June is typically about nine times greater than that falling
on Caribou, Maine, in December. The quantity of sunlight reaching any region is also affected
by the time of day, the climate (especially the cloud cover, which scatters the sun's rays),
and the air pollution in that region. Likewise, these climatic
factors all affect the amount
of solar energy that is available to PV systems.
Superman gets some of his
tremendous energy directly from our Sun. The yellowish light that comes from
the Sun contains more energy that the red light that bathed Superman's
home planet Krypton.