 |
||||||||||||||||||||||
Photovoltaic Energy Systems |
||||||||||||||||||||||
|
A photovoltaic module is solid state: there are no moving parts (excluding electrons). Their life expectancy is predicted to be over 30 years, and it could be much longer. There is nothing exhausted in the silicon cells, and theoretically, if they stay well packaged and protected from moisture they could go on producing electricity indefinitely. PV modules are used in two basic ways: (I )they can power appliances directly, like water pumps or fans, and (2)they can charge storage batteries. |
||||||||||||||||||||||
Types of Systems |
||||||||||||||||||||||
Stand Alone Battery-based Systems |
||||||||||||||||||||||
|
STAND ALONE BATTERY-BASED SYSTEMS The battery-based system is the most versatile PV system. The PV array charges
the battery during the day and the battery supplies energy use day or night.
A charge controller regulates PV current to protect batteries from over-charging.
This type of system is ideal for a weekend cabin or for an RVer whose main priority is lighting, home entertainment, or pumping water on an intermittent basis. One or two PV modules and a small to medium-sized (100 to 800 amp hours) set of batteries comprise the main components of this type of system. All loads are powered by 12-volt DC battery. The loads can be 12 volt appliances or if a small inverter is used (100 to 200 watt) 120,VAC appliances. An inverter is a device that converts low-voltage DC current into 120 AC. Self regulating type PV modules are sometimes used in this type of system to keep it simple. Cost of a system of this size may range from $600 to $1500.
This kind of system can have AC loads as well as DC loads. By wiring your house for both DC and AC appliances, you can have the option to use direct DC power for more efficient fans, refrigeration and water pumping; and AC for using commonly available household appliances such as compact fluorescent lights, vacuum cleaners, washing machines, kitchen appliances, computers, and power tools. This system is for a full--time residence and requires a considerably larger PV array (8 to 16 modules) and battery bank (800 to 2000 amp hours) than the DC only system. Costs of this system can range from around $2500 on up depending on particular household demand.
In this system all loads are 120 AC and run through an inverter. This system could require more modules and batteries than a combination AC\DC system depending on the efficiency of the AC appliances. The recent development of high efficiency AC compact fluorescent lights have made inverter powered homes more practical. There are two advantages to this system: (1)A conventionally wired house is 'inverter-ready', . whereas DC wiring requires larger gauge wire and separate circuits. (2)Wiring costs are less and simpler for 120 AC. However, without any DC alternatives, a back-up inverter may be necessary. A small inverter could be a back-up to provide essential small loads like lighting and communication while the main inverter was being repaired. System cost may range from $3000 on up.
PV-GAS GENERATOR HYBRID SYSTEM
This system consists of a PV array, batteries, a traditional generator fueled by gas, diesel or propane, a large battery charger, and an optional inverter. This system has the advantage of sizing the array for average or above average sunshine availability and letting the generator make up the difference during cloudy spells or heavy power demand situations. Automatic generator start systems that sense battery voltage can operate the generator for charging batteries and powering appliances. The size of the battery bank need not be as large as a stand-alone system of comparable size as long as the generator stays healthy and the noise is tolerable. In addition, some inverters have optional built-in battery chargers that plug into any 110 AC generating source with programmable charge rates and voltage levels. System cost could range from $1500 to $4000 with the main variable being actual generator running time vs. PV array size.
This system can be similar in components to a stand-alone system except the house is also connected to utility grid power. The PV array can provide most or a small portion of the energy demand of the household. The grid power is always available (except during outages). When the batteries' voltage reaches a preset low point, an automatic transfer switch connects the grid to the house loads. This transfer switch can be a separate component or can be a factory built-in component in the inverter. A manual transfer switch can also be used. The grid can simultaneously power a battery charger either in the inverter or as separate unit. The initial investment of the PV can be low for this system, allowing for a gradual build up of the PV array, until total energy independence is obtained. Again, system costs can be relatively small depending on how much actual grid power is used. Another option with grid intertie is selling power back to the power company using a synchronous inverter (See the Trace SW4024). As of now, most power companies are allowed to buy back at only a fraction of the cost (the exception being in California) Major policy change is needed in this situation.
This type of system does not use batteries. Energy produced by the PV array goes directly to the load. The modules can only power one load, like a water pump or a vent fan. This type of system only operates when sunshine is present and needs no regulating components. A device called a Linear Current Booster (LCB) is often used to improve the performance of the motor load. It helps start motors, and sustains their operation during varying sunlight intensities. PV-Direct systems are ideal for remote unattended locations. Protection against pumps running dry and overheating motors may be required. |
||||||||||||||||||||||
 |
||||||||||||||||||||||
| Questions? Contact Us! | ||||||||||||||||||||||
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Solar
electricity is photovoltaic energy. Photo, light, and voltaic, voltage. A
photovoltaic (PV) module is a device that produces electrical energy when
exposed to sunlight. Most PV modules are made up of crystalline silicon cells
that are linked together in a series, like a string of Christmas tree lights.
When sunlight strikes a photovoltaic module, 'free electrons' in each silicon
cell become excited creating a flow of electrons through the conductors linking
each cell--this flow of energy is electricity, to be specific, direct current
(DC) electricity. 
