10 ms·

Will these “guerilla solar” units that plug into a receptacle to back-feed get approved for use? Like, I understand we have the technology to monitor if grid d

Will these “guerilla solar” units that plug into a receptacle to back-feed get approved for use? Like, I understand we have the technology to monitor if grid disappears and self-disable, and a lot of hard-wired rooftop solar does that, but unsure if any soft-wired units have been approved. My fridge is inverter drive and likely operates off DC at its core. Hopefully Samsung or somebody in the future will put a 48VDC port and anyone can plug in a solar panel and it will soak up whatever juice comes off that and use grid for the rest. That avoids batteries (because the fridge does thermal banking), electricians (because 48V is usually excluded), and inverter drive fridges tend to be continuous drive, so running slower when the sun is marginal or full-speed when full works nicely. And it puts some juice into the thing I really depend on if the power goes out (even if only during the day). And consumers can cheaply add some phase change materials for a boost in thermal banking (like really salty water bottles). Put a couple USB charging ports and 12V ports on it too that switch between solar & grid. My router and modem sit on the top of my fridge and use 12V And then we do away with the increasingly unnecessary DC->AC->DC conversion cycles. Seems like the lowest hanging fruit to inexpensive mass (mild) solarization. I always question why we choose between 0kW solar installs OR multi-kW residential installs when we could do massive 250w solar rollouts at low cost with very high efficiency.

George83728 3y ago
Is there even a proper full size DC plug standard suitable for residential use? Besides USB I mean, since USB-C is designed for dainty little gadgets, not full blown appliances.
- Scoundreller 3y ago
  I find most 12V stuff like modems and routers run off a 2.1mm or 2.5mm barrel jack. (And of course it doesn’t imply 12V). You’d need to bodge a double ended connector. Maybe screw terminals would be ideal so you can cut your wall wart cable and wire it up. Most devices will have a bridge diode inside (total waste of electricity, but not going there right now). I guess a cigarette lighter port could make sense but now we might be asking too much on the BoM.
  - George83728 3y ago
    When I say full-size, I mean a plausible NEMA 5-15 replacement exclusively for DC power; something that you could reasonably run at least a kilowatt or two through, and with a mechanically robust design. It should be able to power a toaster oven or stand mixer, and be mechanically robust enough to survive people tripping over the cable many times and being generally rough with it. Those little barrel jacks are fine for what they are, but I can't imagine powering a toaster oven with one. Cigarette lighter ports might fit the bill, at least mechanically. I haven't seen one of those in many years and forgot about them.
    - Scoundreller 3y ago
      Really depends on what kind of amperage you want to run through it. A kilowatt at 12V is going to be 85 amps and too hot for something rated for 15 amps. Not sure what’s approved for DC use in general. Standards bodies will probably disagree with using something typically used for AC with DC because of the risk of plugging the wrong thing into it.
    - 83 3y ago
      Plenty of options exist in adjacent industries. Stage rigging has a lot of nice stuff for powering lighting/effects (like Neutrik powercon) as does automotive (deutsch dtp or dthd). https://www.neutrik.com/en/products/power/powercon-20-a https://www.neutrik.com/en/products/power/powercon-20-a https://www.te.com/usa-en/products/connectors/automotive-connectors/intersection/deutsch-dthd-connectors.html?tab=pgp-story https://www.te.com/usa-en/products/connectors/automotive-con...
- bryanlarsen 3y ago
  USB-C now supports 240W @ 48V. That's enough to power a full size slow-start fridge.
_Microft 3y ago
It's not the low voltage system you are hoping to see but right now there's a push in Germany to have lots of small photovoltaics systems installed. These setups are called "Balkonkraftwerk" ("balcony power plant") and allow up to 600W (or is it 800W now?) to be feed into mains (via a special plug and receptacle, for safety reason as I assume) without any approval required (you are only required to inform your electricity provider of the fact that you installed one). People renting still need to deal with their landlord of course. Drawback: any excess power that one does not use oneself is fed into the grid without compensation. It's a step in the right direction, I guess?
- toomuchtodo 3y ago
  As long as they have rapid shutdown and the ports are built into a manner without a suicide cable, I suppose so? https://news.energysage.com/rapid-shutdown-overview/ https://news.energysage.com/rapid-shutdown-overview/ https://en.wiktionary.org/wiki/suicide_cable https://en.wiktionary.org/wiki/suicide_cable
yessql 3y ago
> Will these “guerilla solar” units that plug into a receptacle to back-feed get approved for use? They are approved at up to 600 Watts in Germany, and that will probably get increased to 800 Watts soon. You can just plug the inverter output into an outlet. This is called "balcony power plants" here, and lots of municipalties are subsidizing it currently. You can't get net metering, but you can offset some of your load with minimal cost and paperwork.
- ragebol 3y ago
  Why no net metering? Is the output too low to bother? I get net metering is not great for various reasons, but why 'discriminate' against what kind of setup it is?
  - bombcar 3y ago
    Probably too expensive to replace the meters (only very old meters actually run backwards). And 600w is probably below the average usage anyway.
    - ragebol 3y ago
      Sounds reasonable. Here in NL, everyone must get a new smart meter that has a separate counter for delivering back to the grid. IIRC, the grid company replaced it free of cost, if done before some date. The old ones (Ferraris meter?) just ran backwards, which is attractive of course. Our new meter has a P1 port which can integrate into eg. Home Assistant
drcongo 3y ago
> Like, I understand we have the technology to monitor if grid disappears and self-disable, and a lot of hard-wired rooftop solar does that, but unsure if any soft-wired units have been approved. Would you mind explaining this sentence? I know very little about these things but I'd like to, are you saying that rooftop solar switches itself off if there's no grid power? And if so, why?
- ragebol 3y ago
  Yes, typically rooftop solar doesn't output when the grid is down. If the inverter doesn't get an AC sinus at 60 or 50 Hz, it won't do anything by default. Some systems can, in a so called 'island mode'. But this is so that they don't supply power when eg an electrician flips a breaker to safely do work. Then better not have the system still energized by solar... I guess the risk with smaller, plug in systems is that they're simpler without such precautions? And you would have 2 live prongs sticking out, which would be bad of course
  - drcongo 3y ago
    Ahhh, thank you, that totally makes sense now.
    - bombcar 3y ago
      There’s a lot of intelligence in a transfer switch that allows island mode - because it has to generate a sine wave when no utility one is present and sync back up with it when one returns. The cheapest ones just cut power when the sine is lost and then make their own, and cut power when they see it return and then sync.
      - Scoundreller 3y ago
        The much cheaper and covers many/most use cases alternative would be a unit that disconnects anything on-grid, and has some in-unit/on-unit sockets you can use during grid-fail at point of device or run extension cords to.
bryanlarsen 3y ago
Not coincidentally, 240W USB-C is 48V. It'll likely become fairly ubiquitous so I can totally see it becoming the power standard for things where DC is useful, like RV's and off-grid setups. 240W is enough to power a fridge with a slow start compressor.
- Scoundreller 3y ago
  Inverter drive is effectively soft-start.
MisterTea 3y ago
> Will these “guerilla solar” units that plug into a receptacle to back-feed get approved for use? Not practical in the USA with split-phase 120/240 (or 120/208 open wye) as you need to connect to both hot legs of the system to feed everything. In 230V countries they mostly have 2 wire service with (I hear some have three phase 230/400) so its easier to evenly back-feed a 2 wire system. > I always question why we choose between 0kW solar installs OR multi-kW residential installs ... Agreed. I have a small home server setup that draws 40W idle and I toyed with the idea of replacing the UPS with a small 1-2kW battery inverter plugged into the wall. My concern with rogue solar installs is how does that interact with the utility company? Their smart meters will see reverse flow of current and if I do not have an "official" solar install, will they force me to adopt one or disconnect my system as it is not approved? So I would only build a system which draws from the utility as needed (cloudy days) and dumps excess power - never back feed.
- Scoundreller 3y ago
  > Agreed. I have a small home server setup that draws 40W idle and I toyed with the idea of replacing the UPS with a small 1-2kW battery inverter plugged into the wall. No idea if this would work in practice, but you might be able to backfeed your battery with a regulated 11.9V onto the 12V lines and backfeed at 4.9V on the 5V lines, so when the power supply shuts off and puts 0V on the 5V and 12V lines, the battery will start back feeding, but when the grids power supply puts out 5V and 12V, no current will move. (Will need blocking diodes to avoid back-feeding the battery that’s kept topped off by its mains charger) Saves you some DC->AC->DC conversions. You might need a 3.3V leg as well. And maybe negative voltages if those are used for anything anymore?
  - MisterTea 3y ago
    I have thought of using a DC-DC ATX supply and eliminate the inverter but I want 120V for other things if needed. But the cost and labor of going DC-DC is higher than DC-AC-DC so the goofy inefficient route it is :-/
- Scoundreller 3y ago
  > Not practical in the USA with split-phase 120/240 (or 120/208 open wye) as you need to connect to both hot legs of the system to feed everything. Just choose which half of your house you want to power :) But presumably these shutoff when grid mains is lost.
peoplearepeople 3y ago
> And consumers can cheaply add some phase change materials for a boost in thermal banking (like really salty water bottles). What does this do?
- _Microft 3y ago
  Phase change materials are a way to store lots of energy at a given temperature. You might have noticed how much time it takes to freeze something - that's because lots of energy need to be extracted from liquid water to turn it to ice. And that without even changing temperature - it all happens at 0°C. With other materials, you can have a similiar effect at other temperatures. This can be used to create a system that keeps a certain temperature even if energy flows into or out of it (until the phase transition is complete). Read more here: https://en.wikipedia.org/wiki/Phase-change_material https://en.wikipedia.org/wiki/Phase-change_material
  - bombcar 3y ago
    You can do it with hot water too - heat your water to near boiling, and merge it with cold to make the desired temperature. The heater won’t turn on until the temperature drops below a threshold. Using this you can avoid hearing water during high demand times.
    - _Microft 3y ago
      A phase transition can store lots of energy without the inconvenience of changing temperature. Melting water ice into liquid water at 0°C takes approximately as much energy as heating the same amount of water from 0°C (assuming that it is already/still liquid) to 80°C. With a material that has a transition temperature of e.g. 21°C, a room could be kept at a very pleasant temperature even when energy is flowing into or out of it.
- milesvp 3y ago
  fun story. I know a guy who designed a high precision refrigerator for storing vaccines. These fridges need to be able to maintain temperature to within some relatively small margin to avoid destroying the vaccines, and they needed to be able to withstand extended periods of no power since they would be stationed in places with questionable infrastructure. The main solution was to use a large water reservoir, it would "store most of the cool" while the power was out, also helped a lot with keeping the temperature stable when there was power.
hedora 3y ago
One of the main benefits of having a battery is backup power during outages. You can’t do that safely without adding a breaker between the utility and the house (to avoid backfeeding and killing linemen). In California, touching a breaker box is at least $10,000, so to amortize the cost of the paperwork, you need to put in a multi kw system. On top of that, you need to anchor it to the ground somehow, so that it doesn’t fly around in 50-100mph winds (which will happen about once during the lifetime of the panels). Portable systems exist, of course. You could get one of those. Also, a multi-kw system isn’t physically that big.
cwillu 3y ago
An issue you may not have considered: if there's enough 250w solar installations to make a regional dent, there's probably enough 250w solar installations to electrify the regional grid sufficiently that the 250w solar installations think there's still utility power and so continue to provide their 250w of solar power to the grid.
- Scoundreller 3y ago
  My idea doesn’t backfeed to the grid but instead utilizes a load that’s “ON” continuously. Inverter drive fridges can vary their power so they don’t cycle on and off like older fridges with AC motors that only operate at one speed.

George83728 3y ago

Is there even a proper full size DC plug standard suitable for residential use? Besides USB I mean, since USB-C is designed for dainty little gadgets, not full blown appliances.

Scoundreller 3y ago
I find most 12V stuff like modems and routers run off a 2.1mm or 2.5mm barrel jack. (And of course it doesn’t imply 12V). You’d need to bodge a double ended connector. Maybe screw terminals would be ideal so you can cut your wall wart cable and wire it up. Most devices will have a bridge diode inside (total waste of electricity, but not going there right now). I guess a cigarette lighter port could make sense but now we might be asking too much on the BoM.
- George83728 3y ago
  When I say full-size, I mean a plausible NEMA 5-15 replacement exclusively for DC power; something that you could reasonably run at least a kilowatt or two through, and with a mechanically robust design. It should be able to power a toaster oven or stand mixer, and be mechanically robust enough to survive people tripping over the cable many times and being generally rough with it. Those little barrel jacks are fine for what they are, but I can't imagine powering a toaster oven with one. Cigarette lighter ports might fit the bill, at least mechanically. I haven't seen one of those in many years and forgot about them.
  - Scoundreller 3y ago
    Really depends on what kind of amperage you want to run through it. A kilowatt at 12V is going to be 85 amps and too hot for something rated for 15 amps. Not sure what’s approved for DC use in general. Standards bodies will probably disagree with using something typically used for AC with DC because of the risk of plugging the wrong thing into it.
  - 83 3y ago
    Plenty of options exist in adjacent industries. Stage rigging has a lot of nice stuff for powering lighting/effects (like Neutrik powercon) as does automotive (deutsch dtp or dthd). https://www.neutrik.com/en/products/power/powercon-20-a https://www.neutrik.com/en/products/power/powercon-20-a https://www.te.com/usa-en/products/connectors/automotive-connectors/intersection/deutsch-dthd-connectors.html?tab=pgp-story https://www.te.com/usa-en/products/connectors/automotive-con...
bryanlarsen 3y ago
USB-C now supports 240W @ 48V. That's enough to power a full size slow-start fridge.

_Microft 3y ago

It's not the low voltage system you are hoping to see but right now there's a push in Germany to have lots of small photovoltaics systems installed. These setups are called "Balkonkraftwerk" ("balcony power plant") and allow up to 600W (or is it 800W now?) to be feed into mains (via a special plug and receptacle, for safety reason as I assume) without any approval required (you are only required to inform your electricity provider of the fact that you installed one). People renting still need to deal with their landlord of course. Drawback: any excess power that one does not use oneself is fed into the grid without compensation. It's a step in the right direction, I guess?

toomuchtodo 3y ago
As long as they have rapid shutdown and the ports are built into a manner without a suicide cable, I suppose so? https://news.energysage.com/rapid-shutdown-overview/ https://news.energysage.com/rapid-shutdown-overview/ https://en.wiktionary.org/wiki/suicide_cable https://en.wiktionary.org/wiki/suicide_cable

yessql 3y ago

> Will these “guerilla solar” units that plug into a receptacle to back-feed get approved for use? They are approved at up to 600 Watts in Germany, and that will probably get increased to 800 Watts soon. You can just plug the inverter output into an outlet. This is called "balcony power plants" here, and lots of municipalties are subsidizing it currently. You can't get net metering, but you can offset some of your load with minimal cost and paperwork.

ragebol 3y ago
Why no net metering? Is the output too low to bother? I get net metering is not great for various reasons, but why 'discriminate' against what kind of setup it is?
- bombcar 3y ago
  Probably too expensive to replace the meters (only very old meters actually run backwards). And 600w is probably below the average usage anyway.
  - ragebol 3y ago
    Sounds reasonable. Here in NL, everyone must get a new smart meter that has a separate counter for delivering back to the grid. IIRC, the grid company replaced it free of cost, if done before some date. The old ones (Ferraris meter?) just ran backwards, which is attractive of course. Our new meter has a P1 port which can integrate into eg. Home Assistant

drcongo 3y ago

> Like, I understand we have the technology to monitor if grid disappears and self-disable, and a lot of hard-wired rooftop solar does that, but unsure if any soft-wired units have been approved. Would you mind explaining this sentence? I know very little about these things but I'd like to, are you saying that rooftop solar switches itself off if there's no grid power? And if so, why?

ragebol 3y ago
Yes, typically rooftop solar doesn't output when the grid is down. If the inverter doesn't get an AC sinus at 60 or 50 Hz, it won't do anything by default. Some systems can, in a so called 'island mode'. But this is so that they don't supply power when eg an electrician flips a breaker to safely do work. Then better not have the system still energized by solar... I guess the risk with smaller, plug in systems is that they're simpler without such precautions? And you would have 2 live prongs sticking out, which would be bad of course
- drcongo 3y ago
  Ahhh, thank you, that totally makes sense now.
  - bombcar 3y ago
    There’s a lot of intelligence in a transfer switch that allows island mode - because it has to generate a sine wave when no utility one is present and sync back up with it when one returns. The cheapest ones just cut power when the sine is lost and then make their own, and cut power when they see it return and then sync.
    - Scoundreller 3y ago
      The much cheaper and covers many/most use cases alternative would be a unit that disconnects anything on-grid, and has some in-unit/on-unit sockets you can use during grid-fail at point of device or run extension cords to.

bryanlarsen 3y ago

Not coincidentally, 240W USB-C is 48V. It'll likely become fairly ubiquitous so I can totally see it becoming the power standard for things where DC is useful, like RV's and off-grid setups. 240W is enough to power a fridge with a slow start compressor.

Scoundreller 3y ago
Inverter drive is effectively soft-start.

MisterTea 3y ago

> Will these “guerilla solar” units that plug into a receptacle to back-feed get approved for use? Not practical in the USA with split-phase 120/240 (or 120/208 open wye) as you need to connect to both hot legs of the system to feed everything. In 230V countries they mostly have 2 wire service with (I hear some have three phase 230/400) so its easier to evenly back-feed a 2 wire system. > I always question why we choose between 0kW solar installs OR multi-kW residential installs ... Agreed. I have a small home server setup that draws 40W idle and I toyed with the idea of replacing the UPS with a small 1-2kW battery inverter plugged into the wall. My concern with rogue solar installs is how does that interact with the utility company? Their smart meters will see reverse flow of current and if I do not have an "official" solar install, will they force me to adopt one or disconnect my system as it is not approved? So I would only build a system which draws from the utility as needed (cloudy days) and dumps excess power - never back feed.

Scoundreller 3y ago
> Agreed. I have a small home server setup that draws 40W idle and I toyed with the idea of replacing the UPS with a small 1-2kW battery inverter plugged into the wall. No idea if this would work in practice, but you might be able to backfeed your battery with a regulated 11.9V onto the 12V lines and backfeed at 4.9V on the 5V lines, so when the power supply shuts off and puts 0V on the 5V and 12V lines, the battery will start back feeding, but when the grids power supply puts out 5V and 12V, no current will move. (Will need blocking diodes to avoid back-feeding the battery that’s kept topped off by its mains charger) Saves you some DC->AC->DC conversions. You might need a 3.3V leg as well. And maybe negative voltages if those are used for anything anymore?
- MisterTea 3y ago
  I have thought of using a DC-DC ATX supply and eliminate the inverter but I want 120V for other things if needed. But the cost and labor of going DC-DC is higher than DC-AC-DC so the goofy inefficient route it is :-/
Scoundreller 3y ago
> Not practical in the USA with split-phase 120/240 (or 120/208 open wye) as you need to connect to both hot legs of the system to feed everything. Just choose which half of your house you want to power :) But presumably these shutoff when grid mains is lost.

peoplearepeople 3y ago

> And consumers can cheaply add some phase change materials for a boost in thermal banking (like really salty water bottles). What does this do?

_Microft 3y ago
Phase change materials are a way to store lots of energy at a given temperature. You might have noticed how much time it takes to freeze something - that's because lots of energy need to be extracted from liquid water to turn it to ice. And that without even changing temperature - it all happens at 0°C. With other materials, you can have a similiar effect at other temperatures. This can be used to create a system that keeps a certain temperature even if energy flows into or out of it (until the phase transition is complete). Read more here: https://en.wikipedia.org/wiki/Phase-change_material https://en.wikipedia.org/wiki/Phase-change_material
- bombcar 3y ago
  You can do it with hot water too - heat your water to near boiling, and merge it with cold to make the desired temperature. The heater won’t turn on until the temperature drops below a threshold. Using this you can avoid hearing water during high demand times.
  - _Microft 3y ago
    A phase transition can store lots of energy without the inconvenience of changing temperature. Melting water ice into liquid water at 0°C takes approximately as much energy as heating the same amount of water from 0°C (assuming that it is already/still liquid) to 80°C. With a material that has a transition temperature of e.g. 21°C, a room could be kept at a very pleasant temperature even when energy is flowing into or out of it.
milesvp 3y ago
fun story. I know a guy who designed a high precision refrigerator for storing vaccines. These fridges need to be able to maintain temperature to within some relatively small margin to avoid destroying the vaccines, and they needed to be able to withstand extended periods of no power since they would be stationed in places with questionable infrastructure. The main solution was to use a large water reservoir, it would "store most of the cool" while the power was out, also helped a lot with keeping the temperature stable when there was power.

hedora 3y ago

One of the main benefits of having a battery is backup power during outages. You can’t do that safely without adding a breaker between the utility and the house (to avoid backfeeding and killing linemen). In California, touching a breaker box is at least $10,000, so to amortize the cost of the paperwork, you need to put in a multi kw system. On top of that, you need to anchor it to the ground somehow, so that it doesn’t fly around in 50-100mph winds (which will happen about once during the lifetime of the panels). Portable systems exist, of course. You could get one of those. Also, a multi-kw system isn’t physically that big.

cwillu 3y ago

An issue you may not have considered: if there's enough 250w solar installations to make a regional dent, there's probably enough 250w solar installations to electrify the regional grid sufficiently that the 250w solar installations think there's still utility power and so continue to provide their 250w of solar power to the grid.

Scoundreller 3y ago
My idea doesn’t backfeed to the grid but instead utilizes a load that’s “ON” continuously. Inverter drive fridges can vary their power so they don’t cycle on and off like older fridges with AC motors that only operate at one speed.