Future Students - What are Photovoltaic Devices
Remote Area Power Supply
A Remote Area Power Supply (RAPS) is an autonomous electricity supply system that relies on one or more energy sources usually in conjunction with a battery and power conditioning equipment. Although RAPS systems can provide a reliable and cost effective source of power in remote regions, they are not limited only to remote areas.
RAPS systems generally incorporate some of the following components:
Sources of Electricity
Photovoltaic (PV) modules
The basic component of a PV module is the solar cell, which converts sunlight directly into electricity. PV modules consist of many solar cells connected together and encapsulated under glass. Usually several modules are connected together to form an array, which has a DC (direct current) output.
Wind turbines
Although they vary greatly in size and design, nearly all wind turbines feature several blades that rotate about a horizontal or vertical axis. The turbine is connected to a generator that converts the wind energy directly into DC or AC (alternating current) electricity.
Microhydro generators
When a steady and reliably source of flowing water is available, microhydro generators can be used to produce electricity. As with a wind turbine, the device is used to drive a generator.
Diesel, LPG and petrol generators (gensets)
These use an internal combustion engine to drive a generator, usually with an AC output. Gensets are often used as a backup source of electricity for when the renewable sources are insufficient.
Remote Area Power Supply Components
Other system components
Batteries
To store excess energy generated during periods of low demand and supply electricity during periods of high demand, an energy storage mechanism is required. The most common form of energy storage in RAPS systems is a bank of electrochemical batteries. Rechargeable lead-acid batteries are the most common type of battery used.
Inverters
An inverter is required to convert the DC electricity from a battery, solar panel or other DC energy source into the AC electricity suitable for supplying standard electrical appliances. Most inverters now available are highly efficient, reliable and have a good quality output.
Regulator/controllers
A regulator/controller is used to interface the battery with the energy sources. Among other things, this prevents overcharging of the battery, which can reduce its life. Additionally, most of them can also disconnect the loads to prevent excessive discharge of the battery.
Trackers
PV modules may be mounted on a tracker, which follows the sun throughout the day and hence increases their output. This can sometimes reduce the required size and hence cost of the array, but at the expense of system reliability.
Maximum power point trackers
An MPPT electronically matches the output of a PV module to the electrical load, thus improving efficiency. This function is often incorporated into the controller.
Metering and protection equipment
Requirements for basic protection equipment such as fusing is defined in Australian Standard AS4509, while metering provides information about system performance.
System Sizing
Before determining the size of the RAPS required to satisfy a particular load, it often pays to minimise the size of the load through demand side management. A household, for example, can significantly reduce its electricity requirements by using gas for cooking and space heating, a solar hot water system for water heating, and energy efficient appliances such as fluorescent lights.
RAPS systems incorporating renewable energy sources have been used for over 20 years, and in remote areas they are often more reliable and cost effective than electricity grid extensions. In New South Wales, for example, over 75% of the electricity network is required to supply power to less than 20% of users, making maintenance of lines to remote customers prohibitively expensive. Hence many electricity distributors now offer RAPS installation and maintenance services for their remote customers. RAPS funding assistance schemes also operate in some states.