4 ms·

You want to wire all the solar cells (72-122 solar cells per solar panel) in parallel, even the different layers of a cell you should wire in parallel. The same

You want to wire all the solar cells (72-122 solar cells per solar panel) in parallel, even the different layers of a cell you should wire in parallel. The same goes for batteries. The reason everyone wires solar panels and batteries in series was that no micro- and nanoinvertors where available or too expensive. That has changed recently, so we now should wire everything in parallel and get 20-50% improvement.

londons_explore 3y ago
Within one panel, there are typically many cells in series (eg. a typical house might have 8 panels, each with 60 cells in series, giving an open circuit voltage of about 30 volts per panel). This discussion is about cells within the panel, not panels within the system. So far, nobody has designed inverters that can work on the 0.5 volt output of an individual cell - although I agree that if such a thing existed, it would indeed help to boost efficiency when cells are mismatched or panels are part shaded. The challenge with 0.5 volt inverters is that currents are large and voltages are small for a given amount of energy, meaning all the parts of the inverter need to be very low resistance, thick wires, and expensive (due to more copper).
- morphle 3y ago
  We designed and built these inverters that can work on the 0.5 volt output of an individual cell. I built discreet component prototypes and then designed the chips. With 0.5 volt currents and voltages are small so you need only thin cheap wires. Our MPPT nano-inverters than aggregate the 6V output of one cell with the 60 cells to any multiple of 6V and thereby lowering the current even more than standard panels with cells in a string. See my other descriptions of the nano-inverters in this HN discussion.
the_third_wave 3y ago
What voltage do these µ/n-inverters produce? If everything is wired in parallel I assume it has to be fairly high to keep total current - and with that wire dimensions - down. This is an advantage of wiring panels in serial strings as that makes it possible to keep (copper) cable dimensions down to 4mm² or 6mm² for a 15kW installation like I installed on the barn roof a few years ago. The 18-panel strings can run at up to ~820V DC on a cold (-20°C) bright day which keeps the current down to a manageable ~9 A. In practice the string current tends to be higher and the voltage lower, normally somewhere around 12 A. What would this look like using those cell-level inverters? [edit] I see you partly answered this question in this thread already. Partly because that answer does not fit with the 'wire everything in parallel' mantra since that would necessitate all panels to produce exactly the same voltage to avoid power loss.
- morphle 3y ago
  We wire the solar cells in parallel to the MPPT nano-inverter chip (0.625 square milimeter). The 6V output of the inverters we can wire in series (we aggregate the voltage and current). 60 cells per panel gives 360V DC and 1.68 A output per panel. Normal panels where the cells are wired in series have around 36V DC and 15A per panel. So the thick 4mm² copper wires of a standard panel must be 8-10 times the wire thinkness of our panels. You can program the MPPT nano-inverter to output 6V AC and then aggregate to 360V AC. In this situation its better to output 110-120V AC in the US or 240V AC in most other parts of the world and feed this directly into the grid. The tricky part is the aggregation of the inverter outputs. The inverters each have different input voltage and current but must all output the exact same voltage to be agregated. The microcontroller have a network between all 60 inverters (122 in larger panels) so they can coordinate/balance their outputs. This is done at 100Kbps to 10 Mbps. The mosfet power transisters in the chip will switch at 100KHz to 1 Mhz to achieve the same ouput voltage.

londons_explore 3y ago

Within one panel, there are typically many cells in series (eg. a typical house might have 8 panels, each with 60 cells in series, giving an open circuit voltage of about 30 volts per panel). This discussion is about cells within the panel, not panels within the system. So far, nobody has designed inverters that can work on the 0.5 volt output of an individual cell - although I agree that if such a thing existed, it would indeed help to boost efficiency when cells are mismatched or panels are part shaded. The challenge with 0.5 volt inverters is that currents are large and voltages are small for a given amount of energy, meaning all the parts of the inverter need to be very low resistance, thick wires, and expensive (due to more copper).

morphle 3y ago
We designed and built these inverters that can work on the 0.5 volt output of an individual cell. I built discreet component prototypes and then designed the chips. With 0.5 volt currents and voltages are small so you need only thin cheap wires. Our MPPT nano-inverters than aggregate the 6V output of one cell with the 60 cells to any multiple of 6V and thereby lowering the current even more than standard panels with cells in a string. See my other descriptions of the nano-inverters in this HN discussion.

the_third_wave 3y ago

What voltage do these µ/n-inverters produce? If everything is wired in parallel I assume it has to be fairly high to keep total current - and with that wire dimensions - down. This is an advantage of wiring panels in serial strings as that makes it possible to keep (copper) cable dimensions down to 4mm² or 6mm² for a 15kW installation like I installed on the barn roof a few years ago. The 18-panel strings can run at up to ~820V DC on a cold (-20°C) bright day which keeps the current down to a manageable ~9 A. In practice the string current tends to be higher and the voltage lower, normally somewhere around 12 A. What would this look like using those cell-level inverters? [edit] I see you partly answered this question in this thread already. Partly because that answer does not fit with the 'wire everything in parallel' mantra since that would necessitate all panels to produce exactly the same voltage to avoid power loss.

morphle 3y ago
We wire the solar cells in parallel to the MPPT nano-inverter chip (0.625 square milimeter). The 6V output of the inverters we can wire in series (we aggregate the voltage and current). 60 cells per panel gives 360V DC and 1.68 A output per panel. Normal panels where the cells are wired in series have around 36V DC and 15A per panel. So the thick 4mm² copper wires of a standard panel must be 8-10 times the wire thinkness of our panels. You can program the MPPT nano-inverter to output 6V AC and then aggregate to 360V AC. In this situation its better to output 110-120V AC in the US or 240V AC in most other parts of the world and feed this directly into the grid. The tricky part is the aggregation of the inverter outputs. The inverters each have different input voltage and current but must all output the exact same voltage to be agregated. The microcontroller have a network between all 60 inverters (122 in larger panels) so they can coordinate/balance their outputs. This is done at 100Kbps to 10 Mbps. The mosfet power transisters in the chip will switch at 100KHz to 1 Mhz to achieve the same ouput voltage.