ELECTRICAL ENERGY FROM SUNLIGHT
Units of sunlight energy - photons - travelling through space at 186,000 mi/sec. collide with electrons in a PhotoVoltaic (PV) solar cell, which in essence is a semi-conductor wafer with a p-n (positive-negative) junction similar to those found in solid-state devices such as transistors, diodes, integrated circuits (chips). Due to the semi-conductor properties of the crystalline material, the electrons are easily dislodged from their atomic orbit, which then traverse (crossover) the junction and accumulate in the ‘n’ (negative) region (electrons are negatively charge). In a complete circuit, the dislodged electrons travel from the negative side of the solar cell, through a work-load to the “positive” side of the solar cell, which now has an electron deficit. The work-load is energized and can now perform “work” such as heat up the element in a light bulb to produce heat-energy while emitting visible light. This electrical energy voltage potential must be consumed the very moment it is produced, or stored in a battery.
In a utility grid, energy production and supply is constant in order to guarantee electrical power (called voltage potential) is available to energize your household circuit; the only variable is the amount of energy available at any given moment in time. The California ISO (Independent System Operator) is responsible for ensuring the constant availability of power on California’s electrical grid. Highly trained, highly skilled humans conduct a virtual symphony in real time - balancing the Supply vs. Demand as they maintain a tight overage margin. WHY? Market Economics! Power production is very expensive, and putting too much power on the grid at any given time is simply wasteful and cost-prohibitive.
A PV solar panel is made up of enough cells connected in series to achieve the desired dc voltage, typically 24Vdc to 48Vdc. PV panels are then arranged and connected in series and parallel fashion to achieve the desired voltage and current. A terminal connection is then made at an “inverter” to produce alternating current (ac) for household use. The excess produced can be used to charge an array of battery to store electric energy.
(See the Compact PV Solar System© section).
In a “Grid-Tied” PV Solar System, unused power is fed into the utility grid to be credited for use when sunlight is not available. In Germany and Spain, the utility companies actually pay cash for power produced. This is not the case in the United States, where a “credit” is applied towards your electric bill. Any excess is further credited towards your future demand and use of electricity (aka net-metering). The utility imposes a transmission fee for the use of its grid, so it’s not entirely a great deal. Right-sizing the system to your consumption is preferable. There is no appreciable economic benefit to supply your neighborhood with the electric power you produce.
UNLIKELY ALTERNATIVES AND WHY
Windpower - Generally prohibited within city-limits and county residential zones because they are noisy and unsightly. Wind power generators require costly maintenance from mechanical wear-and-tear. Small wind turbine generators are quite inexpensive; if you live in a windy rural area with no funny code restrictions, small wind turbine generators can be an attractive and affordable option.
DC Generators - Mostly used as backup power during Power Utility Company blackouts. Permanently installed or portable generators run on natural gas, propane, gasoline or diesel. The fuel-cost to operate back-up generators are much higher than electricity purchased from the Utility Company, rendering generators economically impractical for normal use.