3 ms·

Isn't it cheaper to just buy more panels, enough to meet your winter needs? Then who cares if they sit mostly idle for most of summer; energy not used is harmle

Isn't it cheaper to just buy more panels, enough to meet your winter needs? Then who cares if they sit mostly idle for most of summer; energy not used is harmless. Then your storage model becomes "a cloudy week" rather than "a whole season", and the storage scale changes significantly.

hvb2 1y ago
In almost all cases you lack the area for doing that. And that's not even considering exposure, as in winter most north facing panels on a roof won't get any direct sun because it's lower on the horizon
buckle8017 1y ago
The panels themselves are cheap and getting cheaper. However the mounting systems, solar charger controllers, and inverters are mostly not. The bulk of the cost of panels now isn't the panels themselves, but all the supporting infrastructure. The seasonal variation can be as high as seven to one, so the total install has to be very very cheap to support a 700-1000% over build.
- dv_dt 1y ago
  The last time this was discussed, someone mentioned you only needed as much inverter capacity that you wanted to process. So in winter all panels were hooked up but in summer some were disconnected or bypassed somehow? Though if you are on a grid that allows it, you might want to send summer power back into the grid for credits
  - buckle8017 1y ago
    There's basically two kinds of systems. Micro inverters or mppt with inverters. With micro inverters you cannot over provision the panels in a useful way, each panel or pair of panels has a micro inverter. The mppt plus inverter system you absolutely can do that... but it scales poorly. Shading of a single panel effects the entire string, so the more panels you add to over provision the worse that effect gets. So yes but actually no.
    - dv_dt 1y ago
      It seems like there should be some intermediary per panel smart bypass circuit for pairing up with mptt architecture for this to keep system cost down in these seasonal areas. Edit: turns out there are products for mptt strings called power optimizers that seem to help with this very thing I hypothesized.. at least one company offering them is SolarEdge
      - buckle8017 1y ago
        They're almost as expensive as per panel micro inverters. There's no free lunch here.
jacquesm 1y ago
No, (1) you need too much space and I'm pretty much maxed out already (50 panels), during the wintermonths (2) the angle is really bad, (3) the days are shorter and (4) you're overcast a lot of the time. So that simply will not work. But in the summer I have so much excess I get penalized for it, which is ridiculous.
- Gys 1y ago
  > the angle is really bad Optimize the angle for the Winter. The Summer will do well enough anyways.
  - aydyn 1y ago
    Assuming rooftop, there are too many cons with angled installations so it may not be realistic to change the angle. Flat mounted is the way to go (IMO).
    - rootusrootus 1y ago
      Indeed, at this point I'd plan on going for maximum coverage, the efficiency loss from a non-optimal alignment is completely overwhelmed by being able to put half again or twice as many panels in the same area.
    - jacquesm 1y ago
      Flat mounted has some issues with drainage though leading to a messy surface on the low edge of the panel. You can clean that but it doesn't take much before it is really dirty again.
- toomuchtodo 1y ago
  Once homeowners have done everything they can (as you have, in your example), the remaining optimization is to drive down storage costs (LFP is ~$52/kWh in China at utility scale) until seasonal storage is solved for (which is likely a combination of electrical transmission [to be able to shift low carbon energy from areas that are constantly plentiful] and longer term storage like ammonia or similar fuels created and transported [pumped around] with low carbon energy). Of course, if you have the space, keep putting solar PV up until it's no longer an issue when paired with heat pumps.
PaulKeeble 1y ago
This is certainly the solution in somewhere like Australia where the winter production is about half of the summer production. It gets more problematic in places further north/south where its 5x or worse and then you need quite a bit of land to produce enough power and battery storage than can go multiple days at least. The difference between net zero across the year and 95% unlikely to need the grid on solar and batteries is a staggering difference, about 10x the panels and battery storage. But the equation changes drastically depending on local weather patterns and the solar irradiance difference from summer to winter.
- nine_k 1y ago
  How about keeping an ICE-powered generator for those several days in a year when the sky is stubbornly cloudy and dark? Could make sense for remote houses. BTW keeping your house connected to the mains costs $10-20 / mo, even if you consume nothing. Connection cost is one-time, but likely several thousand.
  - rootusrootus 1y ago
    > How about keeping an ICE-powered generator Or an EV. I only need enough instant battery capacity to last a couple hours. That would handle the vast majority of outages I ever experience, all by itself. If it looks like it is going to be longer, I grab the cable from the transfer switch and plug it into my Lightning. That would get me through a hypothetical week long outage.
XorNot 1y ago
Panels are surface area limited. The maximum my house and land can support is the 10kW I already have. Honestly I'm pretty skeptical of residential rooftop solar - it's not even close to the solution, it's just a cost optimization we shouldn't actually need.

hvb2 1y ago

In almost all cases you lack the area for doing that. And that's not even considering exposure, as in winter most north facing panels on a roof won't get any direct sun because it's lower on the horizon

buckle8017 1y ago

The panels themselves are cheap and getting cheaper. However the mounting systems, solar charger controllers, and inverters are mostly not. The bulk of the cost of panels now isn't the panels themselves, but all the supporting infrastructure. The seasonal variation can be as high as seven to one, so the total install has to be very very cheap to support a 700-1000% over build.

dv_dt 1y ago
The last time this was discussed, someone mentioned you only needed as much inverter capacity that you wanted to process. So in winter all panels were hooked up but in summer some were disconnected or bypassed somehow? Though if you are on a grid that allows it, you might want to send summer power back into the grid for credits
- buckle8017 1y ago
  There's basically two kinds of systems. Micro inverters or mppt with inverters. With micro inverters you cannot over provision the panels in a useful way, each panel or pair of panels has a micro inverter. The mppt plus inverter system you absolutely can do that... but it scales poorly. Shading of a single panel effects the entire string, so the more panels you add to over provision the worse that effect gets. So yes but actually no.
  - dv_dt 1y ago
    It seems like there should be some intermediary per panel smart bypass circuit for pairing up with mptt architecture for this to keep system cost down in these seasonal areas. Edit: turns out there are products for mptt strings called power optimizers that seem to help with this very thing I hypothesized.. at least one company offering them is SolarEdge
    - buckle8017 1y ago
      They're almost as expensive as per panel micro inverters. There's no free lunch here.

jacquesm 1y ago

No, (1) you need too much space and I'm pretty much maxed out already (50 panels), during the wintermonths (2) the angle is really bad, (3) the days are shorter and (4) you're overcast a lot of the time. So that simply will not work. But in the summer I have so much excess I get penalized for it, which is ridiculous.

Gys 1y ago
> the angle is really bad Optimize the angle for the Winter. The Summer will do well enough anyways.
- aydyn 1y ago
  Assuming rooftop, there are too many cons with angled installations so it may not be realistic to change the angle. Flat mounted is the way to go (IMO).
  - rootusrootus 1y ago
    Indeed, at this point I'd plan on going for maximum coverage, the efficiency loss from a non-optimal alignment is completely overwhelmed by being able to put half again or twice as many panels in the same area.
  - jacquesm 1y ago
    Flat mounted has some issues with drainage though leading to a messy surface on the low edge of the panel. You can clean that but it doesn't take much before it is really dirty again.
toomuchtodo 1y ago
Once homeowners have done everything they can (as you have, in your example), the remaining optimization is to drive down storage costs (LFP is ~$52/kWh in China at utility scale) until seasonal storage is solved for (which is likely a combination of electrical transmission [to be able to shift low carbon energy from areas that are constantly plentiful] and longer term storage like ammonia or similar fuels created and transported [pumped around] with low carbon energy). Of course, if you have the space, keep putting solar PV up until it's no longer an issue when paired with heat pumps.

PaulKeeble 1y ago

This is certainly the solution in somewhere like Australia where the winter production is about half of the summer production. It gets more problematic in places further north/south where its 5x or worse and then you need quite a bit of land to produce enough power and battery storage than can go multiple days at least. The difference between net zero across the year and 95% unlikely to need the grid on solar and batteries is a staggering difference, about 10x the panels and battery storage. But the equation changes drastically depending on local weather patterns and the solar irradiance difference from summer to winter.

nine_k 1y ago
How about keeping an ICE-powered generator for those several days in a year when the sky is stubbornly cloudy and dark? Could make sense for remote houses. BTW keeping your house connected to the mains costs $10-20 / mo, even if you consume nothing. Connection cost is one-time, but likely several thousand.
- rootusrootus 1y ago
  > How about keeping an ICE-powered generator Or an EV. I only need enough instant battery capacity to last a couple hours. That would handle the vast majority of outages I ever experience, all by itself. If it looks like it is going to be longer, I grab the cable from the transfer switch and plug it into my Lightning. That would get me through a hypothetical week long outage.

XorNot 1y ago

Panels are surface area limited. The maximum my house and land can support is the 10kW I already have. Honestly I'm pretty skeptical of residential rooftop solar - it's not even close to the solution, it's just a cost optimization we shouldn't actually need.