Photovoltaic Systems

Photovoltaic systems come in many configurations but they share common components and characteristics. Photovoltaic modules, charge controllers, batteries and inverters are the most common elements of a photovoltaic system. Some main advantages of photovoltaic systems are:

• RELIABILITY – Photovoltaic modules are designed for lifetimes of 30 years or more. They are solid state devices with no moving parts and low failure rates.
• LOW MAINTENANCE – Photovoltaic systems operate with minimum servicing and no refuelling, making them a popular power source for isolated locations, such as mountaintops or islands.
• ENVIRONMENTALLY BENIGN – Photovoltaics produce no emissions and offer an alternative to fossil and nuclear sources of energy. Photovoltaic technology is silent and generate power locally, eliminating the need for visually unattractive electrical transmission wires.
• FREE, ABUNDANT FUEL – Sunshine is free, widely available, and virtually inexhaustible. Photovoltaic systems have no monthly fuel bills.
• LOCALLY GENERATED POWER – Photovoltaics use a local resource – sunlight. This provides greater energy security and control of access to energy.
• FLEXIBLE SIZE – Photovoltaics systems range in size from pocket calculators to multi-megawatt power plants. The modular design facilitates easy expansion of systems as finances allow or electrical loads increase.
• TRANSPORTABILITY – As photovoltaic systems are modular in nature, they can be transported in pieces. In addition to simplifying the logistics of transport to remote areas, this feature allows for relatively easy relocation.

There are also some limitations of photovoltaic systems such as:

• SUN-DEPENDENT – Sunlight is an intermittent resource. Electricity is not produced at night, and cloudy weather reduces power.
• INITIAL COST – The cost of photovoltaic modules has continually decreased from about $30 US/Watt fifteen years ago, to about $4 US/Watt today. Most of the expense of a photovoltaic system is the capital cost since operation and maintenance costs are low. Photovoltaic systems are often designed for a life of 20-30 years, and the cost per kilowatt-hour of electricity generated over such a time span is relatively low.

Two main types of PV systems are stand-alone and grid-connected.