A solar system usually consists of solar panel, solar controller and battery, if the power output is AC 220V or 110V, it also needs an inverter. Their functions are as below:
Solar panel
Solar panel is the core component of a solar power system and have the highest value among all other components. It turns solar radiation into electric energy and transmits the power to battery for storage or drive electric load. The quality and cost of solar panel directly determine the system’s quality and cost.
Solar controller
The main function of a solar controller is to master the overall operation and is used to sense when the batteries are fully charged and to stop, or decrease, the amount of current flowing to the battery and thus protect the battery from overcharge and overdischarge. In areas with wide temperature range, qualified charge controller is equipped with temperature compensation function. Other additional functions include light control switch and timer.
A solar controller is used in conjunction with a stand alone system, or a grid connect solar power system with a battery bank for backup. For a grid connect system without a battery bank, a solar controller is not required, just a power inverter which we'll look at shortly.
A solar controller is a small box situated between the solar panel and your batteries. Its role is to control the amount of charge coming from the panel that enters into the battery bank to ensure that it doesn't overcharge the batteries. A controller can also offer a direct connection to load; i.e. you can run appliances directly from it, bypassing the battery bank; but the batteries will continue to be charged.
The solar controller of today are highly efficient. To calculate the size controller you'll need, add up the amp ratings of your solar panels - or you can calculate the size you'll need based on various component selection.
A solar controller is maintenance-free; you just need to check the connections regularly and ensure where you have it situated there's air flow and it's not placed in direct sunlight. While they are quite robust, extreme summer heat can affect a solar controller's performance and shorten the serviceable life.
Battery
Lead-acid batteries are conventionally adopted but NiMH batteries or NiCd batteries are also used in micro systems. The battery stores energy generated by the system and releases it when needed. Deep cycle batteries used in solar power systems are specifically designed to be discharged over a long period of time (e.g. 200 hours) and recharged thousands of times, as opposed to conventional car batteries which are designed to provide a large amount of current for a short amount of time.
Inverter
In most occasions, 220VAC and 110VAC are needed for power supply. Because direct output from solar energy is usually 12VDC, 24VDC, or 48VDC, it is necessary to use DC-AC solar inverter in order to be able to supply power to 220VAC electronic devices. Inverters are generally rated by the amount of AC power they can supply continuously. Manufacturers generally also provide 5 second and 1/2 hour surge figures.
the current produced by a panel is DC. While there's many appliances available that will run directly from DC; most household appliances that you plug into an ordinary wall socket require AC (Alternating Current). In order to switch the current type, you'll need a solar inverter.
The solar inverter sits between the solar panels and your mains wiring in a mains grid connect system, or between the batteries and your appliances in a stand alone power setup.
In the case of grid connect, the inverter feeds any surplus power your panel has generated directly into the power grid for use by other customers - no; the utility doesn't get it for free - you get a credit for the electricity you've contributed, and in some countries you'll even get paid extra! cheap inverters do not seem to like ac adaptors running off them, such as those used for power supplies for notebooks. The inverter gets quite warm, to the point of tripping out if it's a hot day. That heat is also just wasted energy.
The size of the solar inverter you'll need will depend upon your peak load; i.e. the total number of watts you might be using at any given point in time. For example, if you'll be wanting to watch TV while the washing machine is going, lights are on etc.; you'll need to add up the watts of all those appliances and select an inverter rated to that wattage.
It doesn't hurt to go a little larger too in case you need the extra power at some stage and also, electrical appliances can consume far more than their rating when they are first switched on.
As with a solar controller an inverter is maintenance free.
