Controlled Energy
The wild energies discussed in an earlier section
may be collected and concentrated to a more controlled state through
use of various design techniques and technologies. These include
solar power, wind power, hydro power and biomass.
Solar Power
Solar energy may be used for heating of space or water in a direct
or passive manner. In a direct application, solar collectors absorb
the sun's heat and transfer it to air or water pipes for distribution
throughout the building. Usually there are small pumps involved
in the process. Such systems may be used on existing buildings
that weren't specifically designed for use of solar energy. Passive
solar heating may be achieved by design of the structure, with
or without collector units. Essentially, the building becomes
the collector. A passive system may use such elements as solar
rooms, solar windows, solar chimneys, structural heat sinks and
movable insulation curtains. Passive solar heating is less expensive
than other heating systems, simple and maintenance free, environmentally
friendly and open to the outside world.
Solar energy may also be used to generate and store electricity
through the use of photovoltaics. A PV module is made up of many
PV cells, each one a sandwich of two very thin wafers of pure
silicon. The wafers have a surplus of electrons in one layer and
a deficit in the other. Photons in sunlight liberate electrons
to create current which may be used directly or stored in batteries.
A typical system will have PV modules, batteries, a direct current
breaker box, an inverter to change direct current to alternating
current, and an AC breaker box. A supplemental fossil fuel generator
or connection to a commercial power grid may be included. Systems
are available in many sizes.
Wind Energy
Wind energy can easily be combined with PV module energy. The
only difference in the system is the source of power running into
the batteries. A wind driven turbine is used to convert wind power
into electrical power. The turbine consists of a rotor, propeller-like
blades, and a generator. The rotor captures the energy and converts
it to motion to drive the generator. Wind generation requires
a reasonably constant wind source at a monthly average velocity
of 12-16 miles per hour. A tower rising at least 30 feet above
any obstacles within 500 feet is required for the turbine.
Hydro Power
Sites with access to flowing water or tidal action may be able
to make use of the water to generate electricity. Again, the power
would be used directly or stored in batteries so, other than source,
the requirements are similar to that of solar generation. Factors
that influence efficiency are head (drop in elevation from source
to turbine point); flow in gallons per minute; length, size and
condition of pipes; and distance from turbine to point of use.
Small pelton wheel generators can work with as little as 10 feet
of head and on 2 to 250 gallons per minute of flow.
Biomass
Biomass energy is the conversion of wood, wood particles, sawdust,
paper or herbaceous material to heat through burning. Fireplaces
are probably the most common and also the least efficient of biomass
converters. Most of the heat generated is lost up the chimney.
Iron stoves are more efficient than fireplaces but still cool
rapidly. Masonry stoves incorporate the mass of stone with special
flue designs to use wood efficiently and store heat for long periods.
Pellet stoves use reformulated wood waste as fuel and are quite
efficient when burning. They do not store heat well. Compressed
waste paper and herbaceous material is a relatively inefficient
form of fuel but if large quantities are available they can be
used.
The short-term and life-cost of alternative energy systems varies
considerably. Designing a building for passive solar use should
incur little extra cost beyond standard construction methods.
Solar panels and wind powered systems will have a long payback
time when compared to buying electricity off the commercial grid.
Hydro power is relatively inexpensive and efficient. Masonry stoves
are the best biomass converters for heat.
