This guide will help you design and determine what components you need in a solar energy system that meets your needs.
Direct Charging or Charging Via a Battery
There are two main ways to design a solar energy system:
1) For charging small electrical devices (such as mobile phones, iPods / mp3 players, digital cameras, PSPs / gaming stations, etc), you can connect your devices directly to your solar panel via a car cigarette lighter adaptor.
Solar Panel → Car Cigarette Lighter Adaptor → Electrical Appliance
2) For charging larger appliances (such as laptops, telephone / communications systems, TV, lighting and heating / cooling systems, etc), you would use your solar panel to recharge a 12V battery (via a charge controller), and then use the battery to power or recharge your appliance (via a power inverter for AC appliances, since a battery produces only DC).
Solar Panel → Charge Limiter → Battery (→ Inverter) → Electrical Appliance
THE COMPONENTS OF A SOLAR ENERGY SYSTEM
Amorphous and crystalline are the two main types of solar panel. Crystalline panels are further divided into mono-crystalline and poly-crystalline (mono-crystalline tends to be better than poly-crystalline although the difference isn’t always very noticeable).
Amorphous panels generally perform better than crystalline panels under low light conditions and are more efficient in hot temperatures. However, for the same power output, amorphous panels tend to be larger than crystalline panels.
For use in fixed installations, aluminium-framed, glass-sealed amorphous or crystalline panels are ideal. Lightweight folding (generally amorphous) panels – such as the Sunlinq and P3 – provide perfect power solutions on the go, for travelling, on expeditions and in remote locations.
Power Rating of a Solar Panel
The output power that a solar panel can produce is measured in Watts (W). The higher the output wattage, the more powerful the panel. The power or wattage (W) can be calculated from the formula:
Power/Wattage (W) = Voltage (V) x Current (Amps or A)
Solar panels can be connected in series or parallel to create a solar-array and any required voltage-current combination.
Solar panels generate power only when the sun is out. Batteries enable systems to store solar energy so that it is available at night, or when the sky is heavily overcast. Batteries are also used to provide a stable source of power (for both day and night use) when using large wattage solar panels to operate power-hungry devices such as laptops.
You can use most 12V flooded or sealed lead-acid batteries with solar panel systems, although it is best to use a "deep cycle" battery. "Deep cycle" batteries are designed to endure sustained discharge (you solar charge the battery and then drain half its power charging or operating your appliances), compared with car batteries, for example, which are only designed to generate short bursts of energy.
A charge controller (or regulator) is used in a solar system to protect devices or batteries from overcharging, for example under intense light conditions. A charge controller can also prevent too much power from being removed from the batteries, to prevent them from being damaged by deep discharge.
As a general guide, you need a charge controller when the rated current (Amps or A) of the panel is more than 1% of the battery capacity. Charge controllers are rated for a certain solar input current (Amps or A). This input current should always be higher than the rated current (Amps or A) of the solar panel.
Without a bypass diode, if part of a solar panel falls under shadow, the output from the entire panel reduces dramatically. Bypass diodes reduce the impact of partial shading and help maintain a high and stable panel voltage.
A blocking diode prevents power from reversing back into the panel from the battery when the panel is not charging, for example at night. A blocking diode is not necessary if a charge controller is being used (which also performs this function), and is fitted as standard to most smaller solar modules.
You can only operate direct current (DC) loads directly from a battery. If you plan to operate alternating current (AC) loads, you will need to insert a power inverter between the battery and your appliance.
Ensure the input voltage of the power inverter matches your system’s DC voltage. The output AC voltage will generally be either 120V or 240V. Also note that most US appliances operate at 60Hz AC, whereas 50Hz AC is used extensively in other countries.
In sizing a suitable power inverter, you must also note that the inverter must not only run the anticipated AC loads, it might also need to be able to provide surge power, for example to start motors, such as in refrigerators and water pumps.