Aug 29 2010

System Overview

Overview of Renewable Energy Production for off grid systems using batteries.

To select a renewable energy system for your home, boat or camper, you should know what the major parts are called, what each one is for, and how they work together.

The Process
Sun shining on solar PV modules, wind or water turning a generator produces electricity in AC or DC format. Wind and hydro turbines uuslay produce AC current and this needs to be converted to DC  and that is done by a rectifier sometimes built into the turbine. DC is the only kind of power stored in batteries. Often this is 12 volt, the standard used in cars. Larger systems may be designed for 24 volt or 48 volt it’s better to try and design your system for higher voltages if you can.

Charge Controllers
Sometimes called a charge regulator, is a electronic unit receiving the power from solar, wind, or micro-hydro generators, and controlling the flow of power to the battery. To prevent battery damage from overcharging, the charge control automatically stops the charge or diverts it to a dump load 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.

Batteries
This DC power is stored in deep cycle 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. 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.

Inverters
The inverter is the major electronic component that converts the DC current from the battery into 220 volt AC current, the same as utility power for standard household lights, outlets, and appliances. Most renewable energy homes use primarily 220 volt AC produced by the inverter. 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. Sometimes a small renewable energy boat, or cabin may have no inverter, and use only DC wiring and appliances. A stantby inverter/charger is an inverter that also has a battery charger and transfer relay built in. When the input terminals of a standby inverter/charger receive power from an outside source of AC (a generator or utility power) the inverter stops producing AC power from the batteries, and instead passes generator or utility AC power straight through to the house. At the same time it uses the generator or utility power to recharge the batteries. Some standby inverters even auto-start the generator when batteries need charging. A separate battery charger can be used instead of (or in addition to) a standby inverter/charger.

Fuses or Circuit Breakers
Are necessary in all DC wiring between the batteries and other power system components. This prevents fires and equipment damage in event of a malfunction.

Meters
Like the fuel and temperature gages in a car, are necessary to show everything is working. Meters show how much power is being consumed, confirming how much power is available. These battery system monitors can be located in the power room, or at a convenient spot in the home for easier checking.

Engine Generators
Producing 220 volt AC power can be part of the system. This is a second source of AC power and a backup for charging the battery when there is a shortfall in solar, hydro, or wind power.

By jimmy • Systems • 7