Solar electrical systems components & parts

Solar power systems vary from large scale utility plants spread over several acres to individual rooftop solar systems designed for captive consumption.  With this post we want to educate our readers about the main components of solar PV system.

Solar panels:

Solar panels or solar modules are installed together in what is known as a solar array. Modern solar panels are made up of many solar cells or photovoltaic (PV) cells which generate direct current (DC) electricity from sunlight or energy from the sun. Note: It is light energy or irradiance, not heat, which produces electricity in photovoltaic cells.

Panels Mounting structures

These are fixtures that hold the solar panel in place. Their appropriate design is essential to as to make sure, the panels get maximum sunlight. The mounting structures are usually made of Galvanised Iron or Aluminium. They have to designed for wind loads applicable in the region. There are two types of mounting structures-

Triangular Mount: for flat roofs and,
Flush Mount: for inclined roof

The mounting structures are long lasting and require no maintenance.

Solar MPPT charge controller

An MPPT, or maximum power point tracker is an electronic DC to DC converter that optimizes the match between the solar array (PV panels), and the battery bank or utility grid. To put it simply, they convert a higher voltage DC output from solar panels (and a few wind generators) down to the lower voltage needed to charge batteries.

Maximum Power Point Tracking is electronic tracking – usually digital. The charge controller looks at the output of the panels and compares it to the battery voltage. It then figures out what is the best power that the panel can put out to charge the battery. It takes this and converts it to best voltage to get maximum AMPS into the battery. (Remember, it is Amps into the battery that counts). Most modern MPPT’s are around 93-97% efficient in the conversion. You typically get a 20 to 45% power gain in winter and 10-15% in summer. Actual gain can vary widely depending weather, temperature, battery state of charge, and other factors.

Solar inverter:

Solar panels generate DC electricity which needs to be converted to alternating current (AC) electricity for use in our homes and businesses. This is the role of the solar inverter. In a string inverter system, solar panels are linked together in series and the DC electricity is brought to a single inverter which converts the DC to AC. In a micro inverter system, each panel, or every two panels, has it’s own micro inverter attached to the back side of the panel. The panel still produces DC, but is converted to AC on the roof, and is fed straight to the electrical switchboard.

Switchboard:

AC electricity is sent to the switchboard where it is directed to the various circuits and appliances in your house that are using electricity at the time. Any excess electricity is sent to either a battery storage system if you have a off-grid or hybrid system, or to the electricity grid if you have an on-grid system.

Electrical & Safety equipment

The different parts of PV system are connected by cables on DC and AC side. It is also important to install safety equipments since PV systems are designed for long life use. Electrical surges or short circuit can damage the equipment. Proper earthing and equipments like RCBB, Surge protectors, lightening arrestors, etc. are required.

RCBB (Residual Current Circuit Breaker) will protect the system against current leaks, which may lead to shock or fire. And SPD (Surge Protection Device) protects the equipment from surge voltages created during lightening and grid fluctuations.

These components are same anywhere in the world. However, based on the region of your residence, the type of these components used may vary. Solar power systems have a long life. Therefore, it is important to emphasize on quality and safety for durable performance.

The battery bank

In hybrid system once solar power is used by the appliances in your property, any excess power will be sent to your battery bank. Once the battery bank is full, it will stop receiving power from the solar system.

Wires for Solar Panels DC & AC high voltage output

Choosing the right wire for your solar energy system is critical to it’s functioning properly and remaining undamaged. If you get this wrong and choose a pv wire too small for your pv system, your battery bank may not charge fully and as a result your appliances might not work as well or at full power.

Thicker pv wire costs more than thinner pv wire because it can handle more amps. When choosing the thickness of your wire, you can go one of two ways. A little thicker for safety or just thick enough but vulnerable to sudden power surge.

A great way to go about choosing the wire thickness for your solar system is to buy solar panel wire big enough to cope with the biggest current (amp) drawing appliance you have and using that wire for all the other runs to the AC breaker panel. Use a wire sizing calculator for solar arrays that will figure out the size of wire you need.

Aluminum or Copper: The two common conductor materials used in residential and commercial solar installations are copper and aluminum. Copper has a greater conductivity than aluminum, thus it carries more current than aluminum at the same size.

Aluminum may be weakened during installation especially during bending, however it is less expensive than copper wires. It is not used (not permitted) for interior home wiring, as they are used in larger gauges for underground or overhead service entrances and for commercial operations.

Solid or Stranded: The cable could be solid or stranded, where stranded wires consist of many small wires that allow wire to be flexible. This type is recommended for larger sizes. The current tends to flow on the outside of the wire, thus stranded wires have slightly better conductivity as there is more wire surface.

Insulation: The insulation covering wire can protect the cable from heat, moisture, ultraviolet light or chemicals.

THHN is commonly used in dry, indoor locations.
THW, THWN and TW can be used indoors or for wet outdoor applications in conduit.
UF and USE are good for moist or underground applications.
PV Wire, USE-2 and RHW-2 cables can be used in outdoor and wet conditions where their outer cabling is UV and moisture resistant. They must be sunlight resistant.

Color: Electrical wire insulation is color coded to designate its function and use. For troubleshooting and repair, understanding the coding is essential. The wiring label differs according to AC or DC current.

The meter and electricity grid

Depending on how your hybrid system is set up and whether your utility allows it, once your batteries are fully charged excess solar power not required by your appliances can be exported to the grid via your meter. When your solar system is not in use, and if you have drained the usable power in your batteries your appliances will then start drawing power from the grid.

Conclusion

Gaining the knowledge needed to design and install a safe, efficient system not only ensures that your system will meet your needs effectively but also keeps you and your home safe and helps to promote the acceptance of renewable energy as a mainstream energy source.
We are thrilled that you are pursuing a PV system. Whether you choose to install the system on your own or whether you hire a professional installer, please contact the PWM company for solar systems components or for installation .

Simplified layout of a hybrid solar system