For the Latest Solar related Articles:
Inverters:
Q1: What is a Hybrid Inverter
A1: A Hybrid inverter commonly refers to an Inverter that is Grid-Linked and can bring in Mains whenever the battery bank gets too low, or when the load exceeds the rating of the Inverter for a given length of time. It has a high voltage MPPT regulator built into it, some bigger models will have two in order to handle to separate PV arrays, that are orientated in different directions from each other.
A2: Can I use my UPS in a solar system
A2: It has been done, but is a problem when the system is still linked to Mains, as the UPS will employ the Mains, when available, to charge up the battery bank – which reduces the role of the PV array acting as a charger. This can be obviated by the use of a timer but is far from ideal. Also the battery bank voltege of bigger UPS's will be too high for a solar regulator to charge.
Q3: Do I really need a solar inverter with a built in charger
A3: It is not essential, but advisable. The charger is useful when the battery bank is low and the PV array is limited by a bout of inclement weather. You can then use the charger to boost the bank – particularly if you are worried about a pending Power-out and need your battery bank to be at optimum.
Q4: Can grid tie inverters charge up battery banks as well
A4: A Grid-tie inverter either creates 230V AC or 400V AC on a single and three phase system respectively. One would need an inverter charger or a conventional battery charger in order to charge up a seperate battery bank. Hybrid inverters that have high voltage MPPT's built in, will be able to charge a battery bank as well as supply AC to loads wired on the output of the inverter, plus feed excess power back to the mains utility.
Q5: Why do I require a Sinewave Inverter for solar use
A5: Most medium and larger solar systems are required to operate Motors, Pumps and compressors, which all require AC power. However, small rural solar systems which might only be required to operate a few lights, TV and chargers, and thus are often installed with a modified sinewave inverter.
Q6: How is Inverter sizing influenced by In-Rush current
A6: Most good quality inverters have a built-in allowance for In-Rush currents (or ‘start-up’ current, as it is sometimes called). This allows a certain margin from several seconds to several minutes, of peak loads representing some 50-100% of the rated capacity of the Inverter.
Q7: At what DOD (depth of discharge) should an inverter shut-off to protect the batteries
A7: Modern solar Inverters usually have 2 setting: Normal for daily solar use, and Emergency for instances where there might be power outs and where there is no Genset back-up is available. Normal daily solar DoD is set at anything between 20-50% and for emergencies, ar around 75-80% but still not allowing complete discharging in the case of lead acid batteries. However, the latest Li-Ion batteries will allow you to discharge them to 100% without damage.
Q8: Can Inverters be’ stacked’; if so, how many at a time
A8: Modern solar Inverters can be replicated or ‘stacked’ and programmed on a Master-Slave principle. How many times this can be done, varies per manufacturer. However, as most Inverter s between 2-10Kw would only need to be replicated 3-5 times, at most; the majority of the leading manufacturers tend to exceed these benchmarks.
Q9: If my Inverter fails, will I be without power for those linked appliances
A9: This depends on how your system is set up. It should automatically switch to Mains in the event of system failure, or have a manual Bi-Pass switch installed which enables users to bring in Mains or a back-up Genset.
Q10: Can an Inverter switch of appliances sequentially, in order of criticality
A10: This depends upon the make and model of Inverter. If the Inverter has several AC outlets, then usually these can be connected to various appliances in order of criticality, and be programmed to switch off sequentially in order of client-selected importance.
Q11: Can I run a single phase inverter off a 3 phase system
A11: yes, and this is not an uncommon practice with one or more Inverters running of single phases., However it is best to employ a 3 phase Inverter. In either event, make sure you balance loads equally between the various phases you wish to operate.
Q12: Does a solar Inverter switch to Mains when overloaded
A12: Yes, it should, or bring in a Genset, if Mains, is not your first choice of back-up power. It might not do this immediately (often depends upon programming) as the load may only be a short term power ‘spike’ and could be absorbed by the system without damage.
Q13: Does a solar inverter integrate with a Genset
A13: Most solar inverters have the ability to automatically integrate with a genset. However, this requires the Genset to have an auto-start facility. It should kick in whenever the battery bank gets too low, or when the load on the inverter exceeds its rated capacity for any length of time.
Q14: Does a solar Inverter integrate with a wind turbine
A14: Most larger solar Inverters have 2 and sometimes 3 power input connections (e.g. Mains; Genset; Wind Turbine). Many wind turbines with their own built-in charger will be connected only to the battery bank, but some which produce AC, without a charger, could be linked to the Inverter to boost battery bank charging via the Inverter
Q15: What is the usual amount of panels (in a string) fed into a Grid-Tie MPPT
A15: This depends upon whether it is a single, or 3 phase, system. Most single phase Grid Tie systems allow quite a large voltage margin to operate (150-800V). 3 Phase inverters can take up to 800V and start operating at around 450V. So, if your panels put out say 35V, then you would require a minimum of around 5 but preferable between 10-15 for single phase systems and 12-20 for 3 phase systems).
Q16: How good are the built-in chargers for solar inverters
A16: this varies greatly per manufacturer and one should be careful when selecting to charge via the Inverter to ensure that the charger is of a sufficient specification - so as to not cancel the battery manufacturer’s warranty.
Q17: What is the advantage of Micro Inverters located on panels
A17: This is a relatively new technology and has certain advantages, and disadvantages. Because there is now an inverter for every panel, it is possible to monitor each panel individually and this has certain benefits in being able to pick up failing, or under-performing, panels. However you now have many more Inverters to go down of course and have to work with high voltages during installations when installing each panel. It is also more costly than the normal solar inverter systems but has its followers nevertheless.
Q18: How much power does a solar inverter draw when ‘idling’ (in Stand-By)
A18: This also varies greatly per manufacturer. Always check to see how much your inverter draws when at idle – and remember that this is power that will be wasted prior to going to your appliances.
Q19: What happens if my inverter attempts to feed back into the grid when I have no permission to do so.
A19: If you are a user of the latest quadrant meters then the municipality can end up double-billing you for this !!! If you do have surplus power that could attempt to feed back into the grid then you would be strongly advised to install a power meter which acts like a one-way electrical valve and will prevent this happening. Some users with the old analogue meters are able to rverse this meter and thus build-up ‘credits’ but you should have permission to do this (although many don’t have this!!).
Q20: What varying voltages can the modern solar pumping inverter handle
A20: Latest pumping inverters have a technology that is able to handle varying voltages (like grid Tie MPPTs). This ensures that even when you have low voltage (say 100V) available, they will still operate – albeit at a slower rate of flow. This extends the potential hours of use, as well as the performance on low-sun days.
Q21: Should a Genset be connected to the Inverter or to the general DB board
A21: this depends upon the size of the Genset and the load on your Inverter as a percentage of total load. If your Genset is much bigger in capacity than the Inverter laod, it makes sense to connect it to the general DB board. However, if it is less than the potential load of the inverter, then it can be connected directly to the Inverter. However, remember if you have an Inverter failure, then you could be without power!! Best to install a Bi-Pass switch for this occurrence that could then enable the Genset to feed the general DB board.