Solar System Components
Some of the components associated with solar systems are not required for grid-tie systems and to get the most from the Feed In Tariff scheme. However, they are still mentioned here so you can be sure what is andisn’t needed for the time when you come to speak to an installer.
There are many types of solar panels to choose from, as listed below. They are described in more detail in the chapter on Choosing Your Panel
Types and Makes
Monocrystalline panels are the most effective solar panels available today with efficiency levels of between 15-24%. They are also the most expensive as they are costly to produce.
Polycrystalline or Multicrystalline
Polycrystalline or multicrystalline panels are less effective than monocrystalline panels but much better than amorphous or thin film versions with an efficiency of between 13-18%. As you would
expect, they are less expensive than Monocrystalline but more expensive than Amorphous or thin film.
Amorphous or Thin Film
Amorphous or thin film panels are the cheapest and least efficient of the systems converting a maximum of around 8% of sunlight to electricity. However, they work well in overcast conditions and can even generate small amounts of power on brightly moonlit nights. Their thinness and flexibility do make them more suitable for someapplications.
Solar Shingles are a product designed to mimic and replace the roof tile but generate solar energy as well. Shingles are produced in a similar way to amorphous or thin film panels and have similar efficiency. An advantage is they blend in better with existing roof tiles and some prefer them for aesthetic reasons.
Solar Panel Mounting System
This is the hardware to fix the solar panels to the roof, a pole or the ground. It’s usually made of aluminium and allows for adjustment in order to get the best positioning for the array and to ensure airflow around the modules, as a solar panel’s efficiency can be affected by overheating.
This is simply an electrical enclosure. They are usually positioned next to the array and are designed for outdoor use. Individual solar panels are linked in one of two ways, a ‘series’ or a ‘parallel’ array. A series increases the wattage and voltage that is generated and a parallel takes
the average voltage of all the solar panels and adds the wattage for the maximum amount of power than can be generated. The combiner box allows multiple panels to be combined in parallel and also houses series string fuses or circuit breakers.
A solar panel system generates low voltage Direct Current (DC). Grid or mains electricity has to be high voltage Alternating Current (AC). The inverter converts Direct Current to Alternating Current so you are getting the same voltage you would be getting from the grid. Without the
inverter the power source would be too variable for most electrical equipment to cope with and you wouldn’t be able to export to the grid. A grid-tie inverter samples the grid or mains voltage and synchronises its sine wave output to be at the peak voltage point at the same time as
the mains supply. This type of inverter is used to export spare electricity generated by your system into the grid. It is also able to sense when there is a power cut and disconnect itself from the grid so as not to attempt powering neighbours’ houses and cause an electrocution risk to anyone working on power lines that had been turned off.
Traditionally, a solar power system which is made up of a number of panels or modules is connected to a single centralised inverter which then converts the Direct Current to Alternating Current, as described above. Micro inverters are designed to match to a single panel or module. The total cost tends to be higher than using a single inverter and not all manufacturers are offering this option, but it’s worth considering. This permits greater reliability as each panel will have its own inverter so if one inverter goes down the only loss will be power output from a single panel. Sometimes modules can perform differently, due to shade, temperature or cleanliness. In this case each inverter is responding to the output of the individual module
giving better overall efficiency and enabling the condition of each module to be monitored, so if one is performing lower than expected due to a build up of grime or other reason you will be
able to pinpoint the problem panel easier.
With a grid-tie photovoltaic solar system there is no need to worry about all the technicalities relating to batteries. The grid acts like a battery ensuring nothing goes to waste. Whenever the panels produce more than the household requires, the surplus energy is exported to the grid to
become available for other consumers and you will be reimbursed for this contribution.
Whenever the output is less than needed by the household the grid supplies the difference.
Although a grid-tied solar panel system doesn’t require batteries to operate, some might want to consider the possible benefits from having a back-up bank of batteries to store energy until needed. If the grid-supplied power stopped due to severe weather conditions, damage to power lines or other utility malfunction and demand began to outstrip supply, batteries could be a useful back-up system. Batteries for this purpose are lead acid batteries that look a little
like car batteries on the outside but are designed differently internally. They can be heavily discharged and recharged hundreds of times over. Most are 6 or 12 volt and like the panels themselves can be linked together to form a battery bank.
Solar Charge Controllers
A grid-tie system doesn’t require a solar charge controller, but any system using batteries should have one. It regulates the amount of current the solar system feeds into a battery bank. The main function is to prevent the batteries from overcharging but they also block battery bank current from leaking back into the array at night or cloudy days and draining the
MPPT Solar Charge Controllers
Maximum Power Point Tracking (MPPT) solar charge controllers are useful for off-grid solar power systems such as stand-alone and water pump systems. It’s embedded with an algorithm to maximise the amount of current going into the battery from a solar system. It’s not a mechanical tracking system that physically moves the modules but varies the electrical operating point of the modules for maximising available power.
Ground Fault Protector
A ground fault protector averts the risk of damage to the controller or solar array by cutting off the flow of current immediately, in the event of a short occurring. Ground fault protection is usually included within the controller or inverter but, even so, many experts advise the installation of a separate ground fault protector. For systems mounted to a building, a separate Residual Current Device (RCD) needs to be included and that also applies to any solar panel system that exceeds 100 watt.
Total Generation Meter
This is a meter which is installed with the PV system and measures the amount of energy generated by the system chosen.
Export Meter or Feed-in, Feed-out Meter
This is a meter that can be installed by your energy provider that will tell you how much is being fed back to the electricity grid. If an export meter is not available, for whatever reason. The amount will be estimated at 50% of the total generation measurement.
Frequently Asked Questions About Solar Panel Components
Q: Do all solar PV systems need batteries to operate?
A: Not for solar systems linked to the grid. At night when the cells
are not generating energy, electricity will be imported from the
grid in the normal way and any excess electricity generated
during the day is exported and sold to your electricity supplier.
Batteries are only necessary for off-grid systems so that power
generated during the day can be stored for use in the evening.
Q: How long can I expect my system to last and will I have to
replace any of the components?
A: A PV Solar system that has no moving parts should last well in
excess of the manufacturers 20 year warranty. Usual life
expectancy is at least 40 years, so it’s unlikely that any of the
components will require replacing in the foreseeable future.