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I'm clueless in this area. Would a raft be viable? Presumably it would add some drag if you're underway but a small inflatable pontoon raft seems like it coul

by jcims 6y ago

I'm clueless in this area. Would a raft be viable? Presumably it would add some drag if you're underway but a small inflatable pontoon raft seems like it could run 4-6 panels and be reasonably portable when not in use.

walrus01 6y ago
I do off grid PV professionally but don't know a lot about boats. But having been on a few 42-48 ft size cruiser type sailboats, I can't think of a place you could easily pack away six 1.65x1.0 meter size (typical 60-cell) rigid, aluminum framed high efficiency PV panels, unless you basically dedicated the smaller guest bunk to storage space.
- 2Gkashmiri 6y ago
  Hey. You said you do off grid. I have a question. I own a 5 kW on grid setup for net metering. Works fine but now I want to use backups. I have two options, either lithium 100ah 48v which is expensive or 12v 200ah x 4 to make 48v. Cheaper but limited life because the home load would be on it entirely. I dont know. The calculation of kWh checks out to be 100ah x 48v = 4800wh. And for lead acid 200ah x 12v x 2= 4800wh. What do you suggest or is there something I am thinking incorrectly... space is not an issue BTW.
  - walrus01 6y ago
    google "DIY powerwall" if you're up for a bit of a technical challenge. 4 x 12V 200Ah isn't big enough for most houses, unless it's like a cabin in the woods somewhere. and you're right that the cycle life of those and cost is high. but commercial li-ion based solutions are also expensive. However, if you can keep them at 80-85% state of charge, and rarely if ever discharge them below 30%, they should have lifespans 5-6x longer than the lead acid solution. in either solution you can't really consider the full volts * Ah capacity of the battery to be usable. If you were to ever use all of the watt-hours in a 12V 200Ah battery you'd kill it, you never want to go below 20% state of charge... so to be conservative the actual capacity of a single battery is something like: 12 * 200 = 2400 Wh, then (2400 * 0.70) = 1680Wh.
  - guerby 6y ago
    Current LFP battery prices are around $120 per kWh delivered: I just ordered 14 kWh (48V 16S) for 1700 USD delivered. This is cheaper than an Apple laptop. A quarter of the price paid is shipping since it comes directly from China so source price is already under $100/kWh. A recent test by Will Prowse: https://www.youtube.com/watch?v=3U4ZfQ_IToI https://www.youtube.com/watch?v=3U4ZfQ_IToI $433 280Ah LiFePO4 Cells Tested: Cheaper than lead acid! Many people have the same good experience with these kind of cells: https://diysolarforum.com/ https://diysolarforum.com/ Added: 14 kWh will run a 20 Watt laptop for a month.
    - driverdan 6y ago
      Where are you getting new LFP batteries for that price?
      - Peretus 6y ago
        There is a fellow down in Port St. Lucie Florida that has launched a 100ah LiFePO4 with a 10-year warranty for ~ $550usd each. I saw his shop in person when I purchased some solar from him and was quite impressed with the work they've done and the research and testing that has gone into their products. I had already purchased my batteries by the time I discovered his product or I would have purchased from him: https://outlandsolar.com/ https://outlandsolar.com/ My partner and I live aboard a 41ft sailboat and both work remotely as programmers. I installed 1920w of solar on the boat and get approximately 3.5-4.5kwh per day in output, depending on which way we are oriented while at anchor. I installed 600ah of LiFePO4 batteries @ 12v and when combined with that amount of solar, we have pretty much all the power we need. We frequently cook with an air fryer and have a dishwasher on the boat that we run daily-- all off solar.
        driverdan 6y ago
        That price is really good. I'm curious what cells they used.
        Peretus 6y ago
- mkingston 6y ago
  The high efficiency panels are typically semi-flexible without the frame, are they not? Do you think it would be possible to obtain and mount them without a rigid frame? Or even to remove them from the frame? I'm asking partly because I had considered making some sort of basic, folding, portable solar panel structure- imagine a few semi-flexible panels duct-taped together. (I'd likely not _actually_ use duct tape).
  - driverdan 6y ago
    That's backwards. Flexible panels are less efficient than rigid ones.
    - walrus01 6y ago
      Correct, flexible cells are 10-14% efficient, the best rigid monocrystalline single junction Si cells are 23% plus.
      - mkingston 6y ago
        I think that's correct for thin film panels. But it appears that monocrystalline panels can be manufactured with some flexibility. Hence my usage of the term "semi-flexible". Sunpower, for example, claims to produce high efficiency semi-flexible monocrystalline panels that would flex sufficiently for use on a bimini top, for example. It further appears that my statement "high efficiency panels are typically semi-flexible without the frame" is inaccurate- they are typically not reasonably described as semi-flexible, even without the frame and coating.
        walrus01 6y ago
        Real high efficiency monocrystalline si cells are not flexible in any way, for example the typical 156mm cell that makes up a 315-400W rated 60 or 72 cell panel. In fact they're quite brittle and fragile when not encapsulated on a backing sheet and under protective glass. Monocrystalline by definition is not flexible, you're referring to thin films (cadmium telluride or amorphous silicon or other)

by jcims 6y ago

walrus01 6y ago

I do off grid PV professionally but don't know a lot about boats. But having been on a few 42-48 ft size cruiser type sailboats, I can't think of a place you could easily pack away six 1.65x1.0 meter size (typical 60-cell) rigid, aluminum framed high efficiency PV panels, unless you basically dedicated the smaller guest bunk to storage space.

2Gkashmiri 6y ago
Hey. You said you do off grid. I have a question. I own a 5 kW on grid setup for net metering. Works fine but now I want to use backups. I have two options, either lithium 100ah 48v which is expensive or 12v 200ah x 4 to make 48v. Cheaper but limited life because the home load would be on it entirely. I dont know. The calculation of kWh checks out to be 100ah x 48v = 4800wh. And for lead acid 200ah x 12v x 2= 4800wh. What do you suggest or is there something I am thinking incorrectly... space is not an issue BTW.
- walrus01 6y ago
  google "DIY powerwall" if you're up for a bit of a technical challenge. 4 x 12V 200Ah isn't big enough for most houses, unless it's like a cabin in the woods somewhere. and you're right that the cycle life of those and cost is high. but commercial li-ion based solutions are also expensive. However, if you can keep them at 80-85% state of charge, and rarely if ever discharge them below 30%, they should have lifespans 5-6x longer than the lead acid solution. in either solution you can't really consider the full volts * Ah capacity of the battery to be usable. If you were to ever use all of the watt-hours in a 12V 200Ah battery you'd kill it, you never want to go below 20% state of charge... so to be conservative the actual capacity of a single battery is something like: 12 * 200 = 2400 Wh, then (2400 * 0.70) = 1680Wh.
- guerby 6y ago
  Current LFP battery prices are around $120 per kWh delivered: I just ordered 14 kWh (48V 16S) for 1700 USD delivered. This is cheaper than an Apple laptop. A quarter of the price paid is shipping since it comes directly from China so source price is already under $100/kWh. A recent test by Will Prowse: https://www.youtube.com/watch?v=3U4ZfQ_IToI https://www.youtube.com/watch?v=3U4ZfQ_IToI $433 280Ah LiFePO4 Cells Tested: Cheaper than lead acid! Many people have the same good experience with these kind of cells: https://diysolarforum.com/ https://diysolarforum.com/ Added: 14 kWh will run a 20 Watt laptop for a month.
  - driverdan 6y ago
    Where are you getting new LFP batteries for that price?
    - Peretus 6y ago
      There is a fellow down in Port St. Lucie Florida that has launched a 100ah LiFePO4 with a 10-year warranty for ~ $550usd each. I saw his shop in person when I purchased some solar from him and was quite impressed with the work they've done and the research and testing that has gone into their products. I had already purchased my batteries by the time I discovered his product or I would have purchased from him: https://outlandsolar.com/ https://outlandsolar.com/ My partner and I live aboard a 41ft sailboat and both work remotely as programmers. I installed 1920w of solar on the boat and get approximately 3.5-4.5kwh per day in output, depending on which way we are oriented while at anchor. I installed 600ah of LiFePO4 batteries @ 12v and when combined with that amount of solar, we have pretty much all the power we need. We frequently cook with an air fryer and have a dishwasher on the boat that we run daily-- all off solar.
      - driverdan 6y ago
        That price is really good. I'm curious what cells they used.
        Peretus 6y ago
mkingston 6y ago
The high efficiency panels are typically semi-flexible without the frame, are they not? Do you think it would be possible to obtain and mount them without a rigid frame? Or even to remove them from the frame? I'm asking partly because I had considered making some sort of basic, folding, portable solar panel structure- imagine a few semi-flexible panels duct-taped together. (I'd likely not _actually_ use duct tape).
- driverdan 6y ago
  That's backwards. Flexible panels are less efficient than rigid ones.
  - walrus01 6y ago
    Correct, flexible cells are 10-14% efficient, the best rigid monocrystalline single junction Si cells are 23% plus.
    - mkingston 6y ago
      I think that's correct for thin film panels. But it appears that monocrystalline panels can be manufactured with some flexibility. Hence my usage of the term "semi-flexible". Sunpower, for example, claims to produce high efficiency semi-flexible monocrystalline panels that would flex sufficiently for use on a bimini top, for example. It further appears that my statement "high efficiency panels are typically semi-flexible without the frame" is inaccurate- they are typically not reasonably described as semi-flexible, even without the frame and coating.
      - walrus01 6y ago
        Real high efficiency monocrystalline si cells are not flexible in any way, for example the typical 156mm cell that makes up a 315-400W rated 60 or 72 cell panel. In fact they're quite brittle and fragile when not encapsulated on a backing sheet and under protective glass. Monocrystalline by definition is not flexible, you're referring to thin films (cadmium telluride or amorphous silicon or other)