I've got access to 12 flexible Solar Panels – 320VDC each
Main voltage is 220VAC (here in the UK) and also might buy an electric engine running at 48VDC.
Would a 220VAC Uninterruptable Power Supply (UPS) be able to step down the 320VDC to either 220VAC or 48VDC for use on a boat?
I'm thinking of connecting 12 panels in parallel and use either:
- Double-conversion UPS to deliver 48V by bypassing the conversion from the battery back to 220V
- Line-interactive UPS to deliver 220V directly from the 320VDC.
The question is would the UPS's surge protection be able to deal with the high voltages? (Keeping in mind the sun isn't real bright in the UK).
Also with regard efficiency will there be a lot of power loss in the system?
I don't really know how surge protection from overvoltage works in UPS's and assume it uses some kind of buck conversion…is it true?
I'm guessing that the surge protection circuits might struggle with continued voltage overload. Does anyone know if this would be the case?
The question is: Will the UPS's be able to reliably deliver either 220VAC or 48VDC?
Here are the specs for each individual panel:
Open circuit voltage(Voc): 429V
Optimum power voltage(VMP):319 V
Short circuit current(Isc): 0.39A
Max operating current(IMP): 0.288A
torrence:+_5%
Maximum system voltage: 1000V
THERMAL CHARACTERISTICS: (-25 ° C to +90 ° C)
Temperature coefficient ɑIsc +0.08%/ ° C
Temperature coefficient ɑVoc -0.35%/ ° C.
Temperature coefficient ɑPmax -0.15% / ° C.
Over-current Protection 30mA
Best Answer
Solar energy from solar panels, when not being able to be consumed at the rate at which it's being produced (almost always the case), has to be either of the following: - stored (usually in a battery) or - fed back to the grid (e.g. a grid-tied system), or - dumped into a dummy load (usually just beefy resistor packs) to convert the energy to heat the energy has to go somewhere.
So it sounds like what you're interested in using the UPS as the battery bank, but your UPS system probably is designed internally to only charge its batteries from A/C power, where as your solar panels will give you D/C.
You could theoretically (but maybe not very practically) use an inverter to convert your D/C to A/C (if one such inverter existed with such voltage levels input/output specs, wouldn't really surprise me though), and then feed that A/C into the UPS (since the inverter would essentially just give you a normal wall outlet to use), but that would probably just be rather wasteful (e.g. not efficient due to the D/C->A/C in the inverter and then the A/C back to D/C within the UPS (and eventually you might want to go back to A/C for your appliances running off the UPS).
What you might try instead (although this is hardly trivial) is to disassemble (carefully) and try to tap into the battery banks of the UPS directly and figure out what voltage it works at (likely 12, 24, or maybe 48 volts DC). You could then theoretically step down your solar panel's output using some kind of custom (or off the shelf, it anyone knows of one) DC-DC converter, then you can feed that into a battery charger, preferably an MPPT type one. Those kinds would adapt the incoming power to what would be most suitable to charge the UPS batteries to do maximum power point tracking (what MPPT stands for) and reach upper-90% efficiency.
Or if possible (and i don't know if it is) re-arrange the solar panels such that they don't give you 320 volts (are you sure you don't mean watts?) but give you a lower voltage at a higher current rating. Otherwise you'll likely be hard-pressed to find a battery charger that accepts 320vdc to charge the batteries of your UPS.