Photovoltaic (solar cell) systems convert sunlight directly into electricity. A solar or PV cell consists of semiconducting material that absorbs the sunlight. The solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. PV cells are typically combined into modules that hold about 40 cells. About 10 of these modules are mounted in PV arrays. PV arrays can be used to generate electricity for a single building or, in large numbers, for a power plant.

A power plant can also use a concentrating solar power system, which uses the sun's heat to generate electricity. The sunlight is collected and focused with mirrors to create a high-intensity heat source. This heat source produces steam or mechanical power to run a generator that creates electricity.

Solar water heating systems for buildings have two main parts: a solar collector and a storage tank. Typically, a flat-plate collector-a thin, flat, rectangular box with a transparent cover-is mounted on the roof, facing the sun. The sun heats an absorber plate in the collector, which, in turn, heats the fluid running through tubes within the collector. To move the heated fluid between the collector and the storage tank, a system either uses a pump or gravity, as water has a tendency to naturally circulate as it is heated. Systems that use fluids other than water in the collector's tubes usually heat the water by passing it through a coil of tubing in the tank.

Many large commercial buildings can use solar collectors to provide more than just hot water. Solar process heating systems can be used to heat these buildings. A solar ventilation system can be used in cold climates to preheat air as it enters a building. And the heat from a solar collector can even be used to provide energy for cooling a building.

A solar collector is not always needed when using sunlight to heat a building. Some buildings can be designed for passive solar heating. These buildings usually have large, south-facing windows. Materials that absorb and store the sun's heat can be built into the sunlit floors and walls. The floors and walls will then heat up during the day and slowly release heat at night-a process called direct gain. Many of the passive solar heating design features also provide 'daylighting' which is simply the use of natural sunlight to brighten up a building's interior.

Solar Technoligies Photovoltaic solar cells, which directly convert sunlight into electricity, are made of semiconducting materials. The simplest cells power watches and calculators and the like, while more complex systems can light houses and provide power to the electric grid.

Solar Thermal-Beyond Sun Tempering Thermal mass materials have the ability to conduct and store energy, both heat and cold, and to release that energy back into the living space when it's needed.

Heat always moves to colder surfaces. In the solar home, the free solar energy first heats up the air. Since the mass floors and walls are cooler, the heat is absorbed and conducted into these materials. Later, when the sun has set and the room air temperature falls, it will reach a point where the mass materials are warmer than the room air temperature. Since heat seeks out cold, the stored energy will now return to the room. The more mass in the home, the more energy that can be stored.

The amount of south facing glass to be installed is related to the amount of thermal mass in the home, and the reverse is also true. In the sun tempered design, the home does not have the mass needed to absorb the amount of solar energy delivered when glass amounts exceed 7%. With slab construction, the mass is built in, but when carpeted, it can't work for you. When you tile your slab, you have added thermal mass and you can increase the amount of south glass accordingly.

The most cost effective and simplest way to use solar energy is by the direct gain system. The structure itself is the solar system. The south windows are the collectors. The walls and floor are the storage. (mass). Orientate the structure and windows as close to true south as possible.

Use light colors on low mass construction. (ceilings, and partition walls) The ideal thickness for mass materials is 4 to 5 inches.

Use mass materials in the construction, for floors and walls. (adobe, concrete, brick, rock)

Water is the best mass, storing far more energy than other materials, BUT it's not structural.

A masonry fireplace adds thermal mass but should be located on an interior wall.

An interior mass wall performs better than an exterior wall. Insulate the exterior of your walls, keeping the masonry inside, protected from outside temperature extremes.

Solar Wtaer Heating
Almost everyone has experience with passive solar water heating. Can you recollect the number of times by turning on the hose to wash the car or water the plants, the hot water burnt your skin? Our life giving sun with it's Solar Energy was steadily working to give you hot water, though you didn't want it. Well if it's that easy, imagine what you can do if you're actually trying to make hot water.

Passive solar hot water systems are probably the oldest commercially available solar systems. At the beginning of the century a large number of solar water heating systems were used on roof tops. Very little has changed from the original concept. Put a water holding tank in a box, with glass on the side facing south and fill it with water. No moving parts, nothing to break down, free fuel and no pollution.

The passive solar water heater is known today by many names; PSWH, Batch Heater and Bread Box are the most common and then there is the very technical; Integrated Collector and Storage System (ICS).

The PSWH of today usually starts with a 40 gallon, glass lined tank. These tanks come disguised as ordinary electric water heaters, which are stripped of their appliance shell and insulation. Painted flat black, with high temperature engine or barbecue paint and they're ready for solar.

The box should be well insulated to prevent energy loss and the amount of insulation should reflect your local climate. The typical box is constructed with 2X4s or 2X6s, using fiberglass batt insulation. The exterior siding may match that of your home, or some other material suitable for your area. The interior sheathing is often ridged insulation, preferably with a foil face facing in which works to reflect more energy onto the tank. Ridged insulation comes in various thicknesses which can help increase your insulation R-value.

The size of the box must be big enough for the tank, but also large enough to allow adequate solar gain. Typical glass sizing is 1 sq. ft. of glass for every 2 to 2 1/2 gallons of water. A standard size, double glazed, patio door replacement glass (34"X76") is ideal for a 40 gal. water heater. Of course if you already have a piece of glass.......

. A water heater has an inlet and outlet and how you attach your plumbing does make a difference. The cold water inlet has a dip tube which extends down nearly to the bottom of the tank, to deliver the cold water to the right place. The hot water outlet takes the hottest water from the top of the tank. If your design calls for the tank to lie on its side be sure that the cold inlet is at the bottom.

If the collector will be installed on a frame roof it's best to attach in such a way as to spread the weight over a few rafters, and if possible, provide additional support with braces extending up to the rafters from interior walls. The ideal location is as close to the existing water heater as possible.

Shorter plumbing runs are not only more efficient, they decrease the winter freezing potential. The chances of freezing 40 gallons of water are minimal but frozen pipes are a reality. With the tank installed close to the water heater the freezing potential is minimized but not eliminated. All plumbing between the existing water heater and the PSWH is insulated, with more insulation on any pipes exposed to the outside. Also be sure to carefully insulate all plumbing in attic areas.

Plumb the system by first supplying cold water to the solar tank. From there, the hot water outlet is plumbed to the cold water inlet on your existing water heater. As long as the solar water entering your water heater is above the thermostat setting, your water heater does nothing. When the temperature of the solar water entering the water heater is less than the thermostat setting, your water heater makes up the difference.