Controlled Energy

 
 
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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.