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EPP














Environmental Purchasing Bulletin


The Monthly News Bulletin for Purchasing Staff





Volume 6, 2001

Table of Contents

Buying Green Power

a.

What is Green Power
b.

How do I buy Green Power
c.

Why buy Green Power


What is Green Power?
Green Power refers to electricity supplied from more readily renewable
energy sources than traditional electrical power sources. These Green
Power sources can include energy from the wind, sun, earth, plants and
water.

Wind

energy converts the power available in moving air into electricity.
Wind power does not produce air emissions, generate solid waste, or use
water. Wind turbines (windmills) use strong, steady wind to create
electricity.

How is the energy in the wind captured? Wind turbines turn in the
moving air and power an electric generator. The generator then supplies
the electric current. Modern wind turbines fall into two basic groups; the
horizontal-axis variety, like the traditional farm windmills used for pumping
water; and the vertical-axis design, like the eggbeater-style Darrieus model,
named after its French inventor. Modern wind technology takes advantage
of advances in materials, engineering, electronics, and aerodynamics.
Wind turbines are often grouped together into a single wind power plant,
also known as a wind farm, to generate bulk electrical power. Electricity
from these turbines is fed into the local utility grid and distributed to
customers just as it is with conventional power plants.



Fast wind facts: Uneven heating of the Earths surface by the sun causes the wind.
The warmer air rises and the resulting low pressure area draws in
cooler air.
Wind patterns are affected by the spin of the planet, weather
patterns, and terrain.
Wind energy potential increases very rapidly with increasing wind
speed. In fact, if wind speed doubles the energy content goes up by
a factor of eight.
Large wind turbines require a firm consistent wind because they must
compete with conventional generation (coal, natural gas, oil, and
nuclear) at the wholesale level. Large wind turbines are generally not
used in off-grid applications
Small wind systems are used primarily for individual homes,
businesses, or facilities; on-grid or off-grid. Though they cost
relatively more than large turbines, small wind turbines can be used
in areas with modest wind speeds because they compete at the retail
level.
Large wind turbines have gotten much bigger and much less
expensive in the last 15 years. They can already produce electricity
at a comparable cost with power from coal or nuclear power plants.
Some experts expect large wind turbines to be the least expensive
way to produce electricity within ten years.

World wind power use has multiplied nearly fourfold over last five
years and the American Wind Energy Association projects a 60
percent growth in wind-generating capacity this year.


Solar

Photovoltaic (or PV) systems convert light energy into 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. More complicated
systems provide electricity for; pumping water, powering communications
equipment, and even lighting our homes and running our appliances. In a
surprising number of cases, PV power is the cheapest form of electricity for
performing these tasks.
The solar cells that you see on calculators and satellites are photovoltaic
cells or modules (modules are simply a group of cells electrically
connected and packaged in one frame).
Photovoltaic (PV) cells are made of special materials called
semiconductors such as silicon, which is currently the most commonly
used. When light strikes the cell, a certain portion of it is absorbed within
the semiconductor material. This means that the energy of the absorbed
light is transferred to the semiconductor. The energy knocks electrons
loose, allowing them to flow freely. PV cells also all have one or more
electric fields which act to force electrons freed by light absorption to flow in
a certain direction. This flow of electrons is a current. Placing metal
contacts on the top and bottom of the PV cell allows current to be drawn off
to use externally. For example, the current can power a calculator. This
current, together with the cell's voltage (which is a result of its built-in
electric field or fields), defines the power that the solar cell can produce.
THE WIND, HYDROGEN, FUEL CELL CONNECTION
Wind or solar generated electricity can be used to electrolyze water,
producing hydrogen. Hydrogen can be stored and used in fuel cells. Fuel
cells are a promising non polluting, technology for use as a source of
heat and electricity for buildings, and as an electrical power source for
electric vehicles. Hydrogen can also be an energy carrier that stores,
moves, and delivers energy in a usable form to consumers. This is
important because most renewable energy sources cant produce energy
all the time.
Some experts think that hydrogen will form the basic energy
infrastructure that will power future societies, replacing todays natural
gas, oil, coal, and electricity infrastructures.
The price of PV cells has dropped steadily over the last 25 years. As the
economics of PV continue to improve the number installed will increase
dramatically. Solar has vast potential and could provide more power in
California, for example, than any other source, including natural gas, coal,
and nuclear.

Photovoltaic Solar Panel



Large-scale photovoltaic power plants, consisting of many PV arrays
installed together, can prove useful to utilities. Utilities can build PV plants
much more quickly than they can build conventional power plants because
the arrays themselves are easy to install and connect together electrically.
Utilities can locate PV plants where they are most needed in the grid
because siting PV arrays is much easier than siting a conventional power
plant. And, unlike conventional power plants, PV plants can be expanded
incrementally as demand increases. Finally, PV power plants consume no
fuel and produce no air or water pollution while they silently generate
electricity.
Geothermal

energy is generated by converting the hot water or steam
from deep beneath the Earths surface into electricity. Geothermal plants
emit very little air pollution and have minimal impacts on the environment.
They are very economical, competing favorably with fossil fuel generation.


Currently, geothermal plants in the U.S. provide enough electricity to supply
the homes of 3.5 million people. Known geothermal reserves could supply
the entire country with electricity for 30 years, using present-day
technology. Geothermal hot water near the Earths surface can be used directly
for heating buildings and as a heat supply for a variety of commercial
and industrial uses. Underground reservoirs of hot water or steam, heated by an
upwelling of magma, can be tapped for electrical power production. Geothermal heat pumps, or ground-source heat pumps, use the
relatively constant temperature of soil or surface water as a heat
source and sink for a heat pump, which provides heating and cooling
for buildings.
Geothermal energy provides more than 2700 megawatts (MW) of
electric power to U.S. residents comparable to 60 million barrels of
oil per year, enough for 3.5 million homes. This is only a small
fraction of the potential value of geothermal energy in the U.S.
Geothermal electricity is clean no fossil fuels are burned.
Geothermal electricity produced in the U.S. displaces the emission of
22 million tons of carbon dioxide a year!
Geothermal electricity is cost-effective today's cost of geothermal
electricity ranges from $0.05 to $0.08 per kilowatt-hour, and
technology improvements are steadily lowering that range. Also, the
average geothermal power plant requires only 400 square meters of
land to produce a gigawatt of power over 30 years. Compare that with
the enormous amount of land needed for coal and nuclear plants and
all the open-pit and other mining required to fuel