How Solar Works

Solar Electric PV (Photovoltaics):

Solar Electric Systems utilize the sun’s energy and intensity to generate electricity using several “photovoltaic” cells (PVs) connected together into a panel. The most common technology (mono and crystalline silicon) and manufacturing methodology has been in use for over 25 years. The general manufacturing methods have improved with automation and controls to provide long life however the general fabrication process is largely unchanged. Solar systems have been in service for over 30 years.

During installation, several panels are connected together into an “arrays”. The Array is typically installed on the roof with a racking system anchored by the roof itself (rafter penetration). The array may also be installed “off roof” in mounting or tracking system configuration. The Array is then connected by high quality wiring and conduits to an “inverter” that converts the electricity from direct current (DC) to alternating current (AC) for use in the home. The electricity in then routed through the Utility’s distribution box to ensure delivery to the home. Specific safety, roofing, materials and electric codes must be followed and verified to ensure the highest quality installation: NEC, OSHA, Uniform Building Codes, UL and NABCEP.

When the sun strikes these PVs the energy is converted into electricity and delivered to you home or business from the roof top or other locations on the property. This solar electricity flows into the house typically through the utility company’s power distribution box (Grid Tied). When the electricity generated by the sun exceeds the demand in the home, the extra energy (electricity) is sent back to the utility’s “grid” for use where needed (your neighbors) and your meter actually spins backwards. The extra energy sent to the grid will be credited back to the homeowner/business and is known as “net metering”. With net metering the utility will apply an energy credit to your monthly bill for the energy not used; at the end of the year this credit is usually zeroed out providing no benefit to the homeowner. This prevent sizing a solar system that delivers more then is needed. Some utilities, state and countries apply the lowest rate to compensate you for negative balance. In California, recent legislation has led to a law that requires the utilities to pay the homeowner “fair market value” for this extra energy. This is known as ‘feed-in tariffs”. In California feed in tariffs will go into effect in 2010. Feed in tariffs with net metering enables the homeowner/business to become a true energy producer and provides additional financial incentive to go Solar.

Solar Hot Water Heating (SHW – Solar Thermal)

Also known as “Solar Thermal”, SWH provides a means to cut water heating costs significantly with technologies proven in commercial and residential applications. Typical SWH system pays back within 7-15 years depending on the fuel used (natural gas or electric) and current utility rates.

Current Incentives include:

Federal Tax Incentive: 30% of Cost
Increased Property Values – 20x the annual saving from a Solar system installation.
Protection against future rate increases from electric utility.

Typical SWH Applications:

Residential Solar Assist or Solar Pre-heat. Use existing heater as backup
Commercial: Hotels and common use applications.

Types of Solar Water Heaters:

Passive – No Pumps used in system.
Active – Use Pumps to circulate water through collectors

Passive System

Passive SHW system relies on the natural movement of solar heated water from the collector to the storage tank located above the collector. This flow of less dense, lighter water upward and the downward flow of colder water are referred to as “Thermosyphon”. This principle provides the circulation needed. Passive SHW systems are used in warmer climates where freezing does not occur.

Active SHW

Active Systems

Active SHW systems utilize pumps to circulate hot water (open loop) or heating fluid (close Loop) if a heat exchanger design is used (cold climates).

Active Systems Closed Loop