5 ms·

This is a multi-layer cell. It is effectively two solar cells laid on top of one another, and connected electrically in series - one to capture UV and blue/gr

This is a multi-layer cell. It is effectively two solar cells laid on top of one another, and connected electrically in series - one to capture UV and blue/green light, and one to capture Red and IR light. Doing that lets you get more energy out of the sunlight. But critically, the mix of the two sets of colours really matters. The cell needs equal numbers of photons in each set, or efficiency drops rapidly. That means "red sky in the evening" will be a big problem for these cells. One way to work around this is to have a grid of wires between the cells, allowing you to take out or inject current between the cells. You would need a specially designed inverter to be able to do this, but then your cell would be able to handle varying colors of daylight.

Stevvo 3y ago
Existing solar panels are already not producing any significant power around sunrise/sunset. Is a big drop in efficiency an issue if only a few percent of your power would be from those hours anyway?
- londons_explore 3y ago
  Even the midday sunlight color can vary quite a bit depending on weather and the ground color (ground can reflect again off clouds). You don't notice it much, because your eyes auto white-balance what you see. But to the cell it really matters.
  - iforgotpassword 3y ago
    Isn't there much more UV then IR during winter for example? Makes me wonder why they don't just wire the panels in parallel instead, or if the voltages differ too much, have e.g. 20% of the upper layer wired in series with the lower one and then that in parallel with the remaining cells from the upper layer. [Now 10 seconds after hitting submit I realize that leads to the same problem...]
    - morphle 3y ago
      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.
- londons_explore 3y ago
  > not producing any significant power around sunrise/sunset In a future world of plentiful solar, electricity prices are almost zero at midday, and quite high at sunrise/set. That means that even though you might not make many kwh at those hours, most of your profits might come from the shoulder hours.
  - adrianmonk 3y ago
    In a future world of plentiful solar and expensive batteries. Will batteries become cheap? I don't know.
    - KennyBlanken 3y ago
      Why don't you try googling "lithium ion battery history prices" and find out? Top results: "lithium-ion battery prices hit historical low of $140/KWHr"
    - epistasis 3y ago
      Batteries are already cheap. Take these rather conservative (in the sense of being worse for cheapness) numbers that NREL collected: https://www.nrel.gov/docs/fy23osti/85332.pdf https://www.nrel.gov/docs/fy23osti/85332.pdf $482/kwh of battery capacity, installed to grid 15 year lifetime 85% round trip efficiency, And it costs $88/MWh to store electricity, and adding in charging from the average $40/MW, that's $135/MWh all in for battery costs in 2022-2023. Today will be cheaper, tomorrow cheaper yet. Mix in direct wind production at a 40% capacity factor, annd stored electricity in lithium ion batteries, and wind can become fully dispatchable baseload for less than $90/MWh, at today's prices. For comparison, the cost of Vogtle 3, the most recent nuclear power plant in the US, is $180/MWh. Edit: and the main impediment to plentiful solar is policy & regulations that slow it down. The technology is being deployed at massive rates [1] in the US, 33GW in 2023 compared to 22GW in 2022, and ever accelerating. (Capacity factor adjusted, that's roughly 7GW compared to average US electrify draw of ~500GW, for a single year). But the US is way behind China, which installed 217GW in 2023 [2] [1] https://www.canarymedia.com/articles/solar/chart-the-us-installed-more-solar-in-2023-than-ever-before https://www.canarymedia.com/articles/solar/chart-the-us-inst... [2] https://www.bloomberg.com/news/articles/2024-01-26/china-added-more-solar-panels-in-2023-than-us-did-in-its-entire-history https://www.bloomberg.com/news/articles/2024-01-26/china-add...
Aurornis 3y ago
Why do they need to be connected together at all? Medium to large installations have multiple strings anyway. Why not set up the different types of cells as their own strings on separate inverters? In dense housing situations or areas with heavy tree cover the limiting factor starts to become available roof space. Spending a little extra to squeeze out more efficiency would make sense.
- morphle 3y ago
  String inverters are very inefficient in multiple ways over micro- and nano-inverters. A single shaded solar panel will bring down the electricity yield of the entire string. You solve heavy tree cover and other sources of shade with individual MPPT (maximum power point tracker) 4 cent single chip nano-inverters per solar cell, 72-122 per solar panel. For $2.88 extra your solar panel can get 20%-30% more electricity if any part of your panel has shade part of the time. For installations with string inverters you get even more savings when you replace them with nano-inverters.

Stevvo 3y ago

Existing solar panels are already not producing any significant power around sunrise/sunset. Is a big drop in efficiency an issue if only a few percent of your power would be from those hours anyway?

londons_explore 3y ago
Even the midday sunlight color can vary quite a bit depending on weather and the ground color (ground can reflect again off clouds). You don't notice it much, because your eyes auto white-balance what you see. But to the cell it really matters.
- iforgotpassword 3y ago
  Isn't there much more UV then IR during winter for example? Makes me wonder why they don't just wire the panels in parallel instead, or if the voltages differ too much, have e.g. 20% of the upper layer wired in series with the lower one and then that in parallel with the remaining cells from the upper layer. [Now 10 seconds after hitting submit I realize that leads to the same problem...]
  - morphle 3y ago
    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.
londons_explore 3y ago
> not producing any significant power around sunrise/sunset In a future world of plentiful solar, electricity prices are almost zero at midday, and quite high at sunrise/set. That means that even though you might not make many kwh at those hours, most of your profits might come from the shoulder hours.
- adrianmonk 3y ago
  In a future world of plentiful solar and expensive batteries. Will batteries become cheap? I don't know.
  - KennyBlanken 3y ago
    Why don't you try googling "lithium ion battery history prices" and find out? Top results: "lithium-ion battery prices hit historical low of $140/KWHr"
  - epistasis 3y ago
    Batteries are already cheap. Take these rather conservative (in the sense of being worse for cheapness) numbers that NREL collected: https://www.nrel.gov/docs/fy23osti/85332.pdf https://www.nrel.gov/docs/fy23osti/85332.pdf $482/kwh of battery capacity, installed to grid 15 year lifetime 85% round trip efficiency, And it costs $88/MWh to store electricity, and adding in charging from the average $40/MW, that's $135/MWh all in for battery costs in 2022-2023. Today will be cheaper, tomorrow cheaper yet. Mix in direct wind production at a 40% capacity factor, annd stored electricity in lithium ion batteries, and wind can become fully dispatchable baseload for less than $90/MWh, at today's prices. For comparison, the cost of Vogtle 3, the most recent nuclear power plant in the US, is $180/MWh. Edit: and the main impediment to plentiful solar is policy & regulations that slow it down. The technology is being deployed at massive rates [1] in the US, 33GW in 2023 compared to 22GW in 2022, and ever accelerating. (Capacity factor adjusted, that's roughly 7GW compared to average US electrify draw of ~500GW, for a single year). But the US is way behind China, which installed 217GW in 2023 [2] [1] https://www.canarymedia.com/articles/solar/chart-the-us-installed-more-solar-in-2023-than-ever-before https://www.canarymedia.com/articles/solar/chart-the-us-inst... [2] https://www.bloomberg.com/news/articles/2024-01-26/china-added-more-solar-panels-in-2023-than-us-did-in-its-entire-history https://www.bloomberg.com/news/articles/2024-01-26/china-add...

Aurornis 3y ago

Why do they need to be connected together at all? Medium to large installations have multiple strings anyway. Why not set up the different types of cells as their own strings on separate inverters? In dense housing situations or areas with heavy tree cover the limiting factor starts to become available roof space. Spending a little extra to squeeze out more efficiency would make sense.

morphle 3y ago
String inverters are very inefficient in multiple ways over micro- and nano-inverters. A single shaded solar panel will bring down the electricity yield of the entire string. You solve heavy tree cover and other sources of shade with individual MPPT (maximum power point tracker) 4 cent single chip nano-inverters per solar cell, 72-122 per solar panel. For $2.88 extra your solar panel can get 20%-30% more electricity if any part of your panel has shade part of the time. For installations with string inverters you get even more savings when you replace them with nano-inverters.