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Solar Panel Inverters      

An inverter is an important component of any power system. Inverters convert Direct Current (DC) to Alternating Current (AC).

Direct Current can be used directly and flows in a single direction; a common form of Direct Current is batteries. When energy is created it is most often stored as Direct Current energy.

Alternating Current is the standard form of electricity available when you plug anything into a socket in a wall.


Most inverters are equipped with some important features such as "Standby", Battery charging and Surge Capacity.

The inverter actually requires power to run itself. If you leave your inverter on, you may drain its battery bank. Most inverters are equipped with an automatic shut off feature (called "sleep mode," "load demand," "standby," "power saver" and other names). If you are using energy in the home (or business), the inverter senses this and turns itself on, and when there is low or no energy usage, the inverter will shut itself off.
Since the inverter is powered by its own battery bank, you may want to ensure that it has a self charging feature. Thus, when the inverter is in use, it will direct a small fraction of its energy to recharging itself.
Surge Capacity is also an consideration, some appliances (washing machines) or large machines (power tools) require more power than others. To operate any of these items properly, you must have an inverter that is capable of "powering up" to provide the short surge of energy required. Surge Power is provided in a rating that is much higher than the output power rating-usually two, up to six times.      
Output Power is rated in wattage. You will need to be certain of the maximum wattage output of your solar panel or panel array, then match this wattage.      
Efficiency should exceed 90%. The inverter's function is to convert Direct Current (DC) to Alternating Current (AC), and this process naturally loses some power.      
Types of Solar Panel Inverters      
Solar Panel inverters are used primarily to change direct current to alternating current via an electrical switching process. You can think of inverters used with solar panels as electronically synthesized alternators.      

There are three types of solar panel inverters:

Stand-Alone Solar Panel Inverters      
  A solar energy system independent of " the grid" (the larger electrical system that regularly supplies power to you and your neighbors) will use a stand alone inverter.      
Synchronous Solar Panel Inverters      
  A solar energy system connected to the grid will require a synchronous grid tie inverter.      
Multi-function Solar Panel Inverters      
Stand-Alone Solar Panel Inverters      
Stand Alone solar panel inverters function to change direct current (DC) from a battery to Alternating Current (AC). Stand alone inverters, which range from around 100 watts to as much as 8000 watts, are used to power a vast variety of personal or small business projects. Lower watt stand-alone inverters are often used to power laptop computers, whereas high-watt stand-alone inverters could be used to help power an entire household or a building. In order to calculate what class of inverter you need for use with your solar panel system, you will first have to determine the maximum sum of all of the Alternating Current loads in your project. For example, You can usually find the wattage rating on your home appliances by checking the power cable. The sum of these wattage ratings is what you need to determine the wattage you need from your solar panel stand-alone inverter.      
It is important to purchase a quality stand-alone inverter that has a built-in ability to surge if you are using heavy equipment, power tools, or automatic washers, dryers, and dishwashers. These appliances and equipment require a surge on startup, which your stand-alone inverter must be able to supply if you are planning to use these appliances.      
Synchronous Solar Panel Inverters( Grid-Tie Inverters)      

Grid-tie inverters are used in solar energy systems that are integrated with the grid. Like all inverters, it converts DC power to AC, the kind you use to power everything from electric shavers to televisions.

A synchronous inverter takes the solar electricity collected by your solar panel array and applies it to the distribution panel in your home. The power may then be used by loads within your home or it may flow out to the utility grid. When there is no solar energy available (eg. at night, or during cloudy periods) the utility seamlessly provides power to supply the loads in your home. The inverter has to be matched with the wattage output of your solar panels.

  Synchronous inverters are also designed to be used with net metering. This process (if available in your area) allows you to sell energy to your local energy supplier to alleviate your energy costs.      
The term Synchronous Solar Panel Inverters arises from the synchronous dynamic that such a system creates between the utility company and a personal solar-panel installation. Synchronous Solar Panel Inverters allow power generated by your solar panels to be stored in battery. If there is an excess (meaning you did not use as much power as you produced), the power is sold back to the utility company at the same rate at which you are charged!
On the other hand, if your solar panels are unable to provide you with the power you need, your Synchronous Solar Panel Inverter will allow the utility company to supply power to make up the difference. The advantages of a Synchronous Solar Panel Inverter are many, as you can see. This Synchronous Solar Panel Inverter system is quite useful - your batteries will provide you with energy during the utility company's power outages, and on bleak, rainy days, you won't have to worry about your solar panels performance, because any power you need will be supplied by the utility company via your Synchronous Solar Panel Inverter.      
A final advantage of Synchronous Solar Panel Inverters is that you will not have to precisely calculate your Alternating Current load in order to set up the system. It is only necessary if you want to have complete reliance on solar panel in most scenarios, but if you are comfortable with buying a steady but small portion of power from the utility company, a rough estimation of wattage from your solar panel system should suffice with the Synchronous Inverter.      
Multifunction Solar Panel Inverters (hybrid-power inverters)      
Multifunction Solar Panel Inverters combine the best of both worlds, and they are usually the best choice for your solar panel system. While more expensive, multifunction inverters may be your best choice.      

A multi-function inverter is additionally connected to a battery bank and a standby generator. The battery bank allows you to store power to rely even less on conventional grid power sources.

If there is no solar energy available, the multi-function inverter may draw your needed electricity from your solar batteries. If the battery bank is drained, the inverter will draw power from the conventional grid (utility lines).      
True and Modified Sine Wave Inverters      
An inverter converts a direct current to an alternating current through a delicate electrical switching process. This process makes an inverter function as a synthesized alternator, which are typically used to produce AC current by creating a smooth alternation, similar to a pendulum gently swinging. This alternation takes the form of a sine wave, which is the ideal wave pattern for transmitting AC power.      

Modified Sine Wave inverters are better in typical solar applications when electric motors are not involved. They are not quite as efficient as true sine wave inverters, but you'll find that they are much more affordable. Unlike true sine wave inverters, modified sine wave inverters produce a stepped waveform, which isn't really a sine wave at all.

Because the current is not alternating perfectly, the stepped waveform of the modified sine wave inverter causes the inverter to generate an irritating buzz. Take this into careful consideration when purchasing an inverter.

True sine wave inverters are very efficient and have a very accurate waveform to the true sine wave. True sine wave inverters are a little more pricey than modified sine wave inverters because of the reduced noise and their strong compatibility with certain devices, such as electric motors. This is the better option if you value silence, or want optimal performance from electric motors, such as those found in an electric water pump.      
Charge Controlers      
A charge controller is used in combination with a battery, and it does just what its name implies: it controls the charge your battery is receiving. The charge controller is placed between your solar module and the battery.      
When the battery has received enough charge, the charge controller will withhold further charging. This is also called "voltage regulating" within the solar industry.      
Without a charge controller, your battery will over-charge. This can damage your battery and it may be dangerous in other ways-it can even cause fires.      

Most charge-controllers also include a feature called low-voltage disconnect (LVD).

This feature prevents the battery from over-discharging. As with any other battery, draining causes damage. Almost all modern inverters, even cheap pocket-sized ones, have this feature built in.      
And finally, charge controllers offer battery temperature compensation (BTC). With this feature, the charge controller adjusts the charge rate based on the basis of the temperature of the battery. Batteries are sensitive to temperature variations above or below 75 F.      
Batteries for Solar Energy Systems      

Like other renewable energy systems, solar energy systems use a lead-acid deep cycle battery. This type of battery is different from a conventional car battery, as it is designed to be more tolerant of the kind of ongoing charging and discharging you would expect when you have variable sunshine from one day to the next.

Lead-acid deep cycle batteries last longer but they also cost more than a conventional battery. The major difference between lead acid batteries and other batteries is that they have solid lead plates; in conventional car batteries, the plate is made of a sponge-like material. You may not be able to tell this difference simply by looking at the battery, and some batteries are labeled "deep cycle" when they are not. If you are looking at a battery that is rated for cranking amps, this will likely mean that it is not a deep cycle battery.
You would use a battery in an independent solar energy system, and it is also used in some grid inter tied with battery backup systems.

Battery Size to your System

Be sure that you have a battery properly sized to your system. If you size your batteries too small, they may discharge too often (even for lead-acid deep cycle batteries) so you would have to replace them more often. When you size your battery to your system and maintain it well, it will last 10 to 15 years. This will make it well worth the investment in money and time.

Depth of discharge

Depth of discharge is a measure of how much energy has been taken from a battery. With the lead-acid deep cycle battery used in a solar electric system, there is more tolerance for discharging. You can discharge the battery of a solar energy system 50% to 80% with no damage to the battery. This makes it very different from a car battery, (also called a start battery).

Like all large batteries, the batteries for your solar system can be dangerous. According to Prevent Blindness in America there are over 6,000 serious accidents every year involving car batteries. Be very aware of the dangers of any battery you use: lead-acid batteries contain a diluted sulfuric acid electrolyte. It is highly corrosive in both liquid and gas form. Use protective glasses any time you are working with your battery.

Solar Energy Battery Maintenance

Your deep cycle battery can last long if you take good care of it. You need to have a solar service representative check over your battery as part of an annual maintenance routine to check all aspects of your system.

On the other hand, you may want to adopt the alternative energy ethic of taking care of your own energy system. In this case, you would do your own battery maintenance. Some basic steps to ensure the good working condition of your battery would be:

Fully charge your battery before use.

Be sure to fully tighten the connectors and properly wire all the cables.

Fasten vent caps tightly and checked from time to time.

Water the batteries after extended charging. If the plates have been exposed before charging, cover them with a thin layer of water.

Check the acid level after charging. Your acid level should be kept " below the bottom of the fill well in the cell cover.

Never fill or overfill the cells. When the battery charges, the electrolyte can overflow, causing corrosion and other damage.

Use distilled or treated water. There is a rating for distilled water, counted in total dissolved solids (TDS). Water used should not be higher than 100 TDS.

A deep cycle battery is designed to withstand a depth of discharge of 80 percent, but if this can be avoided, do so. The best way to avoid this is to keep discharges to a minimum. Properly sizing your battery is one way to do this. Another is to build a battery bank.
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