Solar Cell Electricity: the AC / DC InverterThe power inverter unit is an essential component of a solar cell electricity installation, and purchasing a good quality inverter will mean greater efficiency from you panels. The reason a inverter is needed is to adapt the direct current produced by a solar panel array to the alternating mains current. WHAT IS A DIRECT CURRENT? A Direct Current (or DC) power supply moves electrons through the wire in ONE DIRECTION ONLY. For an electron to deliver its energy to the device being operated (the light globe in the example below) it must travel the full length of the circuit.
Solar cell electricity arrays produce DIRECT CURRENT. They must do so, since the basic principle behind the cells is a directed flow of electrons facilitated by the energy in sunlight. WHAT IS ALTERNATING CURRENT? ALTERNATING CURRENT (AC) means that the flow of electrons is not in the one direction, but is constantly reversed. This can be likened to a boat being propelled by the rower continually pushing the paddle backwards and forwards.
The AC power is produced in the form of a pure sine wave. This means the electricity flows backwards and forwards like a wave on the ocean. It does this very quickly, many thousands of times each minute.
All mains electricity is AC. The reason for this is that the electrons in AC current do not need to travel as far to deliver their energy to the device being operated. They stay in the same area of the device, and once they are expended they obtain energy from bumping into their neighbouring electrons. It is this continual passing of energy from one electron to its neighbour that allows the energy from the power station to reach our homes, even though the electrons are not made to travel the full distance from the power stations to our homes. As the electrons do not need to travel great distances, the energy supplied by the power station to the mains grid experiences for lower rates of loss than would be the case with DC power. There are several pieces of equipment that adapt the mains power supply to a current suitable for your home appliances. You can see some diagrams of that process here. The DC / AC inverter of a solar panel array needs to convert the direct line of electricity flow into the alternating current of the mains supply. To get the best productivity in terms of converting DC power to mains supply, it needs to convert its electricity to a clean sine wave. For this reason, obtaining a pure sine wave inverter is a solid long term investment. Most cheap systems employ a square or slightly rounded waveform, often called a "modified" sine wave, inverter which produces an alternating current, but one that looks like this: 
This misses a lot of conversion area on the curve and therefore loses energy. While a pure sine wave inverter will be a greater initial cost, it will ensure that your household solar power system will be far more productive over its life than with a cheaper unit. It is important to ask your potential solar cell electricity installer about the kind of sine wave inverter they provide with the system. If it's a rock-bottom price you can be assured that the inverter is the square ("modified") wave version. In this case it is best to ask what the price of the system would be with the pure sine wave inverter included rather than the cheaper variety. Failing this you can obtain good pure sine wave inverters from a variety of providers. While you will need a qualified electrician to install this unit, the added cost will be worth it in terms of efficiency of your solar cell electricity array. One more aspect to be aware of is the warranty on your solar system. Adding a pure sine wave inverter from a company other that that which installed the solar array may affect your warranty. Given the large number of competing installers of household solar systems now available and the continued rise in prominence of solar power, you may be able to haggle for a pure sine wave inverter to be included in your system for no extra cost to you. Commercial prices are not fixed, and it is good to remember that while you are choosing solar power, the installer is relying on your business for their livelihood. |
