Solar Energy

Sun shining on solar modules produces DIRECT CURRENT electricity, or DC, the only kind of power stored in batteries. Often this is 12 volt DC, the standard used in cars and RVs. Larger systems may be designed for 24 volt DC, or sometimes 48 volt DC. This just means combining the same solar modules in pairs for 24 volt, or groups of four to get 48 volt.

This DC power is stored in DEEP CYCLE LEAD-ACID BATTERIES, which give back the electricity as needed, even when no power is being produced. Like a bank account, power put into batteries over a period of time can be taken out more quickly if a lot is needed. Like a bank account you cannot take out more than you put in, or the account will be depleted. Moreover, lead-acid batteries need to be frequently 100% fully charged to remain in good condition. They should never be drawn completely down to empty.

Try to charge things DC to DC. If you have an AC to DC convertor then you are losing more energy. It is more efficent to go from DC batteries straight to your item without the inverter.

Parts of the System:

INVERTER

The INVERTER is a major component that converts the 12, 24, or 48 volt DC current from the battery into 120 volt AC current, the same as utility power for standard household lights, outlets, and appliances. Most solar homes use primarily 120 volt AC produced by the inverter. A few DC circuits are usually added where using DC can save a lot of energy. Sometimes a small solar electric RV, boat, or cabin may have no inverter, and use only DC wiring and appliances.

If there are a number of consecutive days without sunshine, the owner, being aware of the weather, checks his batteries. If the charge level is low, an engine driven generator may be started to recharge the batteries in order to keep the whole system working. A battery charger plugs into 120 volt AC from the generator producing low voltage DC to charge the battery. The generator is shut down after the batteries have been recharged. (Battery chargers in Recreational Vehicles are called converters).

SOLAR MODULES

SOLAR MODULES are installed in groups of 1 to 12 modules on a solar mount, which in turn attaches to a building, to the roof of an RV, or atop a metal post in the yard. Together this is called a solar array. Each solar module is wired to the other modules in that array by sunlight tolerant solar interconnect wiring. Several arrays may be wired to a solar combiner box where they are all connected to heavier underground wires taking the power to the battery and equipment room. Always price the solar panels by price per watt. Depending on size, expect to pay between $4.00 and $5.00 per watt. A typical 100 watt solar panel will cost about $400 to $450. The good new is they are quite durable & you can expect 25 years or more of service.

CHARGE CONTROLLER

A CHARGE CONTROLLER, sometimes called a charge regulator, is a small wall mounted unit receiving the power from the solar modules and controlling the flow of power to the battery. To prevent battery damage from overcharging, the charge control automatically cuts back or stops the charge when batteries become full. A charge control may have manual control switches and may have meters or lights to show the status of the charging process. I recently priced a controller for 200 watts and it was 105.00 dollars. It was just a small electronic device, fit in the palm of my hand, and nothing fancy.

BATTERIES

BATTERIES receive and store DC electrical energy, and can instantly supply large surges of stored electricity as needed to start or run heavy power appliances that the solar panels alone could not power. This large power capability can be a fire hazard just like utility company power, so fuses and circuit breakers on every circuit connected to a battery are essential. Battery size is chosen for both surge power requirements and for the amount of reserve power needed. Typically, 2 to 12 square feet of batteries weighing 200 to 1000 pounds are enclosed in a battery box with a vent pipe to outside. This component contains both acid and a great deal of stored energy, therefore requires care and knowledge to safely install. Batteries are expensive. But you pay for what you get. I priced batteries today for 299.00 for my system that would allow me to keep a 800 watt day fully charged. Two batteries would be 600 dollars for my needs.

INVERTER

The INVERTER is the major electronic component of a power system. It converts DC power stored in batteries to 120 volt AC, standard household power. Short, heavy cables with a large fuse or circuit breaker carry battery power to the inverter. After conversion to AC, power from the inverter connects into the circuit breaker box of the house in place of utility lines. The house breaker box routes power to lights, appliances, and outlets of the house. Inverters for home power come in ratings from 50 to 5500 watts.