SOLAR ENERGY { COMPONENTS OF SOLAR ELECTRIC SYSTEM}

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Components of a Solar Electric System   

      

Solar panels

The heart of a solar electric system is the solar panel itself. There are various types of solar panels and I will describe them all in detail later on. Solar panels or, more accurately, photovoltaic solar panels, generate electricity from the sun. The more powerful the sun’s energy, the more power you get, although solar panels continue to generate small amounts of electricity in the shade.

Most solar panels are made up of individual solar cells, connected together. A typical solar cell will only produce around half a volt, so by connecting them together in series inside the panel, a more useful voltage is achieved. Most solar panels are rated as 12-volt solar panels, although higher-voltage panels are also available. A 12-volt solar panel produces around 14–18 volts when put under load. This allows a single solar panel to charge up a 12-volt battery.

Incidentally, if you connect a voltmeter up to a solar panel when it is not under load, you may well see voltage readings of up to 26 volts. This is normal in an ‘open circuit’ on a solar panel. As soon as you connect the solar panel into a circuit, this voltage level will drop to around 14–18 volts.

Connecting the panels in series allows a solar array to run at a higher voltage. Typically, 24 volts or 48 volts in a stand-alone system, or up to several hundred volts in a grid-tie system.

Connecting the panels in parallel allows a solar array to produce more power while maintaining the same voltage as the individual panel.

Batteries

Except in a grid-tie system, where the solar array connects directly to an inverter, solar panels rarely power electrical equipment directly. This is because the amount of power the solar panel collects varies depending on the strength of sunlight. This makes the power source too variable for most electrical equipment to cope. In a grid-tie system, the inverter handles this variability: if demand outstrips supply, you will get power from both the grid and your solar system. For a stand-alone or a grid fallback system, batteries store the energy and provide a constant power source for your electrical equipment.

Most lead-acid batteries are 6-volt or 12-volt batteries and, like solar panels, these can be connected together to form a larger battery bank. Like solar panels, multiple batteries used in series increase the capacity and the voltage of a battery bank. Multiple batteries connected in parallel increase the capacity whilst keeping the voltage the same.

ControlleR

If you are using batteries, your solar electric system is going to require a controller in order to manage the flow of electricity (the current) into and out of the battery. If your system overcharges the batteries, this will damage and eventually destroy them. Likewise, if your system completely discharges the batteries, this will quite rapidly destroy them. A solar controller prevents this from happening. There are a few instances where a small solar electric system does not require a controller. An example of this is a small ‘battery top-up’ solar panel that is used to keep a car battery in peak condition when the car is not being used. These solar panels are too small to damage the battery when the battery is fully charged.

Inverter

The electricity generated by a solar electric system is direct current (DC). Electricity from the grid is high-voltage alternating current (AC). Traditionally, there is usually one central inverter in a solar system, either connecting directly to the solar array in a grid-tie system, or to the battery pack in an off-grid system. A more recent invention has been the microinverter. Micro-inverters are connected to individual solar panels so that each individual panel provides a high-voltage alternating current.

Solar panels with micro-inverters are typically only used with grid-tie systems and are not suitable for systems with battery backup. For grid-tie systems, they do offer some significant benefits over the more traditional ‘big box’ inverter, although the up-front cost is currently higher.

Electrical devices

The final element of your solar electric system is the devices you plan to power.

Low-voltage device

Most off-grid solar systems run at low voltages. Unless you are planning a pure grid-tie installation, you may wish to consider running at least some of your devices directly from your DC supply rather than running everything through an inverter. This has the benefit of greater efficiency.

You can also charge up most portable items such as MP3 players and mobile phones from a 12-volt supply.

High-voltage devices

If running everything at low voltage is not an option, or if you are using a grid[1]tie the system, you use an inverter to run your electrical devices