How does it work?
Below is our infographic using a Sunsynk inverter and its capabilities as an example of an installation. Each hotspot gives you an explanation of the component of the solution and key elements to consider and keep in mind when considering your own solar solution. The same principles apply to your business premises solution, just a bit bigger.
Get in touch with us for a free consultation, solution design, and proposal to make sure you have peace of mind in your investment.
**This is not in any way a diagram illustrating how a solution should be installed to comply with regulations and is only for informative purposes**
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Photo Voltaic Modules:
More commonly known as solar panels.
Output is generally defined and stated in watts.(volt x amps = watts). It is important to take note of the voltage and amperage specifications of the chosen product to ensure you stay within the capabilities and input range of the MPPT and Inverter being used.
Modules are typically connected in series within a string. Connections in series increase the voltage output. Connecting strings in parallel will increase the amperage output. This is a crucial consideration during solution design vs the capabilities of the MPPT and Inverter.
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DC Combiner box:
This box contains the safety devices to protect not only the rest of the equipment but also isolators to break the flow of energy from the modules to the rest of the system when maintenance needs to be done.
All components that typically form part of this box is DC rated an are usually:
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DC Breakers
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DC Fuses
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DC Surge Arrestors
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Maximum Power Point Trackers(MPPT):
The MPPT is the connection interface and controller for the solar modules. It regulates the flow of energy from the modules to the inverter. Fully hybrid inverters have their MPPT’s built in whereas others use external MPPT’s. Depending on your requirements and physical infrastructure like your available roof space you might need more MPPT’s than the normal residential hybrid inverter has built in.
The basic rule is that you cannot have modules facing in different directions or at different angles on the same MPPT as the MPPT will limit the performance of the other modules to match that of the weakest performing module.
Typical residential inverters have 1-3 MPPT’s. MPPT’s also have minimum and maximum voltage and amperage range. Exceeding either would damage the MPPT or Inverter. You also have a minimum start-up voltage which is required. Having too few modules in a string will not generate enough energy for your MPPT and Inverter to start up.
An important consideration is the effect of ambient temperature when calculating minimum and maximum string lengths as modules perform better in cold weather and worse in hot weather.
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Charge Controller:
Most inverters have a built-in charge controller which manages the battery charging and discharging by communicating with the batteries Battery Management System(BMS) through a data connection.
Typical residential hybrid systems use a 48-52v battery system. Newer commercial and industrial inverters are High Voltage solutions where the batteries typically have a nominal voltage between 400-800v. The same energy math applies as with the modules where (watts=volts x amps). For example, a 52v battery of 100ah(amp hours) has a total capacity of 5200w (5.2kwh).
Using 4 x 12v 100ah batteries in series would then for example give you 4.8kwh. You would connect the batteries in series if the inverter is a 48-52v inverter, but you have 12v batteries.
If you would need to increase your total storage capacity you would connect the batteries in parallel. 2 x 52v 100ah batteries in parallel will keep the voltage at 52v, but increase your available amp hours(ah). Thus 52v x 200ah = 10.4kWh.
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Battery Disconnect:
Your battery disconnect which contains your DC fuses is a critical safety component of your solution. Given the potentially high current that would be flowing through the cables to the inverter charge controller, it is critical to have your cables adequately sized and paired with the correct size of din-blade fuses to protect the cabling in the case of over-current which could lead to overheating and combustion.
Another important factor in these connections is ensuring a firm clean contact surface on connections with the relevant torque settings/tightening of bolts to prevent loose connections and arcing.
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Batteries:
Traditional lead acid and gel batteries do not have the capabilities of new Lithium Ion Phosphate (LifePO4) as they have a low charge and discharge rate and are much more dangerous in terms of heat build-up and chemical discharges. Traditional lead acid and gel batteries can also only be depleted to 50% of their capacity after which the battery cells are damaged whereas most LifePO4 batteries can be 100% discharged without causing damage.
Battery sizing is also an important aspect to consider. Your typical residential home uses less than 1000w(1kw) of power per hour. If you are allowed by warranty to use 80% of your 5.2kWh LifePO4 battery you effectively have just over 4kwh available which will keep your lights and plugs on for around 4 hours(4kWh/1kw=4hours). If you want to keep your house energized for 8 hours you will need 2 batteries with a total capacity of 10.4kWh.
Each client and household is however different and it is important to discuss the requirements in detail with your installer and if possible measure your kWh usage for a period of 7 days to ensure expectations and needs are met. Measuring your usage will also indicate your usage profile of daytime vs nighttime consumption.
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AC Changeover Box:
This box is the interface between your property and the inverter. Power flow to and from the inverter is managed and isolated at this point using a changeover switch with supporting breakers to turn power to and from the inverter on and off. Additional protection devices like surge arrestors should also be located within this enclosure.
All switchgear in the enclosure is AC-rated and sized to give adequate protection to the inverter components as well as the gauge of the electrical conductor used to prevent over-current which will lead to temperature build-up and potential combustion.
Typical components are:
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AC Changeover switch
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AC Circuit Breakers
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AC Surge Arrestors
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Grid-Connection:
The grid connection with the inverter is bi-directional in this example using a Sunsynk Inverter. It is the source of power from the grid to the inverter, but the inverter also has the capability to supply excess solar PV energy to the grid only connected equipment needing power.
Examples of this would be your geyser, oven, pool pumps etc.
The downside of having items connected on the grid-only side of the inverter is that should your grid connection be off due to load-shedding or an issue at a substation these items will not be powered by the inverter at all leaving you with cold water for example until grid power is restored.
Your typical grid connection in a residential property is 60-63amps which equates to about 16kw. Should you exceed that load your mains breaker in your home would trip.
An 8.8kw Inverter can supply about 38amps and a 5.5kw inverter around 24amps.
Again, the correct cable sizing paired with adequate breakers is crucial.
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Load or UPS Port:
This AC connection to your house is a one-way output powering what we see as your “essentials” and typically included your lights and plugs. This port uses battery power when needed to supply power to the items that need it at that time so you can be sure your lights, internet, security systems, fridges, and freezers are on.
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Auxiliary or Generator Port:
This AC port is also a bi-directional port but can either supply power or receive power depending on the software configuration on the inverter. Its original design was for a generator to feed power to the inverter if needed to charge batteries if the grid connection is not present and you do not have sufficient solar energy being generated from you solar panels.
The additional software setting allows us to use it as a secondary AC output for “non-essential” items on the larger inverters like your geyser, oven, water pumps, and air conditioners. Any excess solar PV power not needed by the essential load is directed to this aux port as the first priority and only if needed grid power is consumed to power the shortfall resulting in increased savings and comfort knowing that you will have hot water flowing even with extended grid power outages when you have PV modules as part of your solution.
Setting on the Sunsynk inverter range also allows us to power these “non-essentials” when the battery level is above a certain state of charge(SOC).
Should you need to use the aux port for non-essentials, but also have a generator we will typically integrate your generator with an additional changeover switch to act as an alternate grid supply giving you a full hybrid and potentially complete off-grid solution.
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CT Coil:
This device which is directly connected to the inverter and supplies some of the most critical data needed. It monitors the grid connection to verify if it is present, but also the quality of the frequency of the supply along with the voltage being supplied. The inverter has relevant safety parameters which can be set to reject grid power should the power be outside of an acceptable range. For example, if the voltage drops too low the amperage of the supply increases which could cause damage to the inverter and hour equipment.
The inverter thus acts as a protection device, not only for itself but also for the rest of your property which it supplies. Data is also gathered in terms of consumption which is fed through to your mobile device app giving you insight into the current and past performance and usage of your solution.
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