5 ms·

Putting solar panels on roofs doesn't make a lot of sense to me. Per kWh, rooftop domestic PV costs can be unto 10 times more expensive on a levelized cost bas

by derriz 3y ago

Putting solar panels on roofs doesn't make a lot of sense to me. Per kWh, rooftop domestic PV costs can be unto 10 times more expensive on a levelized cost basis (https://www.lazard.com/media/2ozoovyg/lazards-lcoeplus-april-2023.pdf https://www.lazard.com/media/2ozoovyg/lazards-lcoeplus-april...) compared to a ground based utility/grid scale installation. In fact, adding any complexity to a solar panels hardly makes any sense any more because of the incredible fall in panel prices (by 90% in about 12 years). This price fall has made a lot of solar ideas defunct. For example, when panel prices were much higher, solar plants often had mechanical systems to orient panels to track the sun - but now nobody bothers - it's cheaper and simpler to just install an extra 10 or 20% more panels and have a no-moving-parts/low maintenance system. Same with this idea - the extra complexity and maintenance cost of adding active cooling to a panel to increase efficiency by 10% - I cannot see the economics stack up. For the same reason, the enthusiasm for the idea of installing solar plants in north africa and exporting power over interconnectors to Europe is gone. It's cheaper to install twice as many panels in a field in cloudy northern Europe (where capacity factors are half of what they would be in the Sahara) than deal with the costs and complexity of underwater interconnectors and transmission system upgrades.

AlanSE 3y ago
> For the same reason, the enthusiasm for the idea of installing solar plants in north africa and exporting power over interconnectors to Europe is gone. It's cheaper to install twice as many panels in a field in cloudy northern Europe (where capacity factors are half of what they would be in the Sahara) than deal with the costs and complexity of underwater interconnectors and transmission system upgrades. I don't know about that, because long-range transmission significantly reduces the intermittency, even for the same longitude. It's not just about smoothing out the curve of solar production, demand patterns (due to weather, industry, behavior) will also have variations from place-to-place and these allow opportunities for power export. Some places will have more dispatchable and expensive power plants than others, which also creates an export opportunity so that power is exported so that one country can burn less fuel. However, I admit this argument is slightly undercut by the question "can't we just build solar panels in the country with dispatchable dirty power?" True, but there's also a connection to wind power which is super local and random.
- derriz 3y ago
  In general, yes, more interconnection and better transmission can only be good. But in the specific example I gave, the finances just don't work. Underwater HDVC is just too expensive and panels are too cheap - even with the value of the uncorrelated intermittency. And even if the numbers could be made work financially, I can't see European countries lining up to become dependent on fixed infrastructure in politically unaligned and/or unstable countries like Algeria or Libya - especially given recent experience with Russia. Securitywise, Nord Stream has shown that underwater infrastructure is vulnerable to attack and difficult to protect/guard.
  - coryrc 3y ago
    Winter solar in Northern Europe, when it produces 10-15% of summer, is not displacing the winter heating load supplied by fossil fuels. North African solar could do that.
    - trompetenaccoun 3y ago
      Keep in mind the political instability in NA and geopolitical risks.
hedora 3y ago
A few years ago, solar panels dropped a lot more than 10% in efficiency when they got hot. I can see investing in water cooling them back then, but suspect that technology trends have already made this product obsolete. If they really can cool the panels at a price + reliability + installation complexity comparable to conventional panels, it might be worth it. However, our heat pump water heater is under 10% of our electricity bill, so if it's cheaper to just add 10% more panels + batteries, then this product seems like a non-starter to me. I guess it's possible this would make sense for heating swimming pools (they create an extremely large reservoir for the waste heat during the summer).
BHSPitMonkey 3y ago
For some homeowners looking at a residential installation, the added independence itself is a feature (as is the autonomy to be able to slightly accelerate the world's shift to renewables -- the average person does not get to participate in deciding when and where to build a grid-scale solar installation). Of course, reducing a home's energy consumption would be even more preferable than just offsetting it with localized generation - but reality is complicated.
- toast0 3y ago
  I think the autonomy is the big thing. Redundancy is nice, but many or possibly most residential rooftop solar installs are grid tie only; adding the ability to power locally when the grid is down adds signifigant expense. Tarriffs are a thing to. It's common for rooftop generation to offset grid usage, but if you used your construction budget to buy into a larger project, you would likely not be able to offset usage, you'd more likely earn wholesale rates on generation at the facility and pay retail rates on usage at home. Probably you get more generation capacity, and maybe that works enough, but probably not. There's also a lack of these projects to buy into.
- SoftTalker 3y ago
  As a homeowner, the last thing I want to do is own and maintain the equipment to provide electric power. I will gladly pay a utility to take care of this for me. A home solar system with battery storage and an automatic transfer switch and interconnected to feed power back to the grid is a complicated setup and I want no part of owning or maintaining that.
  - Scoundreller 3y ago
    All comes down to reliability, no? People probably said the same in the transition from simple and reliable ice boxes with ice block delivery to electric fridges.
  - idiotsecant 3y ago
    I think that's why parent post said some home owners. Some people like coconut. As a person i, however, hate coconut.
jl6 3y ago
> For the same reason, the enthusiasm for the idea of installing solar plants in north africa and exporting power over interconnectors to Europe is gone. Are you quite sure, when you factor in the cost and availability of land?
- derriz 3y ago
  Yes - all the serious proposals are dead (the xlinks guy is a grifter) because underwater HDVC costs have risen while panel prices are a tenth of what they were. Not only the finances, but (as I described in another comment), the security aspects of depending on fixed infrastructure in unaligned and relatively politically unstable countries are very unpalatable. Such infrastructure is incredibly vulnerable and difficult to protect.
1-more 3y ago
> Putting solar panels on roofs doesn't make a lot of sense to me. Per kWh, rooftop domestic PV costs can be u[p]to 10 times more expensive on a levelized cost basis Yeah an idea I've had kicking around for a bit: if my roof is a good place for solar, it should make some kind of sense to lease it out to someone else who owns the panels and their output. I've never heard of anyone making that arrangement. There are people near me who own property with no water rights who are able to lease that land out to solar utilities. I'm not against solar and I do think that we need to have every available square inch of the world making energy if we're to survive the next century. I'm just saying that the current incentives kind of don't support it.
- SoftTalker 3y ago
  A residential roof is too small to make that idea interesting to anyone who is looking to rent space for solar panels.
  - wffurr 3y ago
    Leasing a solar system on one’s roof is a thing, either fixed or as a power purchase agreement: https://www.sunrun.com/solar-lease https://www.sunrun.com/solar-lease Leasing the roof itself to the solar company less so. Though the difference isn’t clear. In theory you get a deal on your power, but it really depends on the terms of the lease compared to your local utility’s prices.
- regularfry 3y ago
  Up until 2019, exactly that type of scheme was very popular with installers in the UK.
  - 1-more 3y ago
    Interesting! What happened in 2019? And sorry I'm speaking in kind of broad strokes here; I live in the US and don't own my roof so I haven't gone as deep into this as I'd like.
    - 3y ago
PaulKeeble 3y ago
They are doing this in the UK, a high voltage DC line is being connected to Northern Africa where power where about 2.5-5GW of power will be produced. Its very viable economically but I also think we have more than enough roof space for solar panels and surround sea for offshore wind to meet our power needs for the foreseeable future. Even if a commercial installation is half the price per KWh the economics still work out personally. The reason is a combination of taxes, profits and substantial business overheads that make personal Solar substantially cheaper than the current grid power which is all tied to gas prices. I am about on average 9p a KWh over the life of a Solar system which I can export for 15p currently and buying from the grid is 45p through the day. Its a substantial saving yet wholesale prices are hovering on average around the same 9p. The overheads of the grid and businesses are most of the cost and substantial.
- derriz 3y ago
  You're talking about Xlinks? They are nowhere near doing it. They have been talking about it since 2018 and trying to get investors to give them money but despite favourable press and interest from politicians, a heavyweight board, nobody who has looked at their business plan has stepped up to the plate to back the project. Desertec is the other one which has raised nothing despite touting a similar idea since 2008. Xlinks is going nowhere - in fact the founder, Simon Morrish, seems to be mostly spending his time on other projects these days. Even their website claimed last year that the £16B project could be profitable if a CFD at £48/MWh (CDF is a type of contract electricity suppliers bid for in UK auctions to win 15 year contracts to supply electricity). Unfortunately local solar pv, on-shore and off-shore wind auction prices in the last auction round were all lower than this. Regarding local subsidies and supports for rooftop solar, of-course it can make sense for an individual. My point is that on aggregate, it does not make sense - if the government is going to spend $X to encourage the production of solar PV, then supporting rooftop solar provides a poor return on the subsidy. And the difference is more than half the price - typically the multiple is 3 or 4 times cheaper.
ZeroGravitas 3y ago
What you say in your last paragraph also applies to rooftop solar. You have to weigh up better efficiency far away against local generation and account for the extra cost of transmission. If PV costs are dropping faster than transmission, which they are, then local generation gets more desirable.
idiotsecant 3y ago
What % overbuild do I need to generate power at night?
- alvah 3y ago
  Clearly a sarcastic question, but as solar panels become vastly cheaper, the battery storage requirements to effectively guarantee power on demand become much less onerous. The kWh of backup required for a solar PV system sized to maximum demand is much more than (e.g.) a PV system sized to 2x maximum demand.
- adrianN 3y ago
  Hydrogen storage has a round trip efficiency of about 40%, so you need less than 2.5 times overbuild.
AtlasBarfed 3y ago
- the grid investment is nil, - it increases the resiliency of people in emergency situations like storms, hurricanes, tornadoes, earthquakes, mudslides - there is LOTS of real estate so the "hidden cost" of dedicating land to solar panels isn't needed. Finally, I feel residential solar is a ripoff currently, because there is some degree of price fixing. 10x more expensive for LCOE? That is a policy problem, not a real economic reality. 2x or even 3x I could see, but 10 fucking times? Some thing with batteries to consumers. The tool makers like lawnmowers / power tools / etc are simply raking consumers over the coals with vastly overpriced batteries compared to what the BEV companies are getting. Maybe the magical hand of economics will finally deliver for the end consumers, but currently it is not.
callalex 3y ago
Rooftop solar makes sense when independence is a key need. Where I live (San Francisco Bay Area, California, USA) the power utility is extremely corrupt. This makes their service the terrible combination of unreliable (sometimes being disconnected for several days at a time) and extremely expensive (they charge about half a dollar per kWh). Being as independent from them for my energy needs as possible means buying solar, and my roof is the only open space I have available.
perlgeek 3y ago
> Putting solar panels on roofs doesn't make a lot of sense to me. Per kWh, rooftop domestic PV costs can be unto 10 times more expensive on a levelized cost basis [...] compared to a ground based utility/grid scale installation. This is an odd either/or attitude. If you own a house with a roof, there are factors that decide whether putting PV on your roof is economically sustainable for you or not. If you do the analysis, and the answer is that it pays off in a sufficiently short time frame, then install PV, even if utility-scale PV somewhere else would be 100x cheaper. As long as the hypothesized utility PV installations don't bring down the electricity cost so much that your own installation becomes unsustainable, the two are basically independent.
rstuart4133 3y ago
> rooftop domestic PV costs can be unto 10 times more expensive on a levelized cost basis ... compared to a ground based utility/grid scale installation Your "can be" hides a lot of sins. Looking at the data you quote domestic PV also "can be" 1/2 the cost of of ground based utility installation. The truth is between those extremes and will vary a lot depending on situation. But here is something that doesn't vary so much: the difference between the retail cost and wholesale cost is around a factor or 3. Translation: utility solar has to be around 3 times cheaper than domestic before it makes sense to a household. I don't think it's terribly surprising there are a lot of places that factor of 3 tilts the balance in favour of domestic PV.
bogzxo 3y ago
here in south africa where we have load shedding and sometimes don’t have power 8 hours a day, so they are necessary if possible.

by derriz 3y ago

AlanSE 3y ago

> For the same reason, the enthusiasm for the idea of installing solar plants in north africa and exporting power over interconnectors to Europe is gone. It's cheaper to install twice as many panels in a field in cloudy northern Europe (where capacity factors are half of what they would be in the Sahara) than deal with the costs and complexity of underwater interconnectors and transmission system upgrades. I don't know about that, because long-range transmission significantly reduces the intermittency, even for the same longitude. It's not just about smoothing out the curve of solar production, demand patterns (due to weather, industry, behavior) will also have variations from place-to-place and these allow opportunities for power export. Some places will have more dispatchable and expensive power plants than others, which also creates an export opportunity so that power is exported so that one country can burn less fuel. However, I admit this argument is slightly undercut by the question "can't we just build solar panels in the country with dispatchable dirty power?" True, but there's also a connection to wind power which is super local and random.

derriz 3y ago
In general, yes, more interconnection and better transmission can only be good. But in the specific example I gave, the finances just don't work. Underwater HDVC is just too expensive and panels are too cheap - even with the value of the uncorrelated intermittency. And even if the numbers could be made work financially, I can't see European countries lining up to become dependent on fixed infrastructure in politically unaligned and/or unstable countries like Algeria or Libya - especially given recent experience with Russia. Securitywise, Nord Stream has shown that underwater infrastructure is vulnerable to attack and difficult to protect/guard.
- coryrc 3y ago
  Winter solar in Northern Europe, when it produces 10-15% of summer, is not displacing the winter heating load supplied by fossil fuels. North African solar could do that.
  - trompetenaccoun 3y ago
    Keep in mind the political instability in NA and geopolitical risks.

hedora 3y ago

A few years ago, solar panels dropped a lot more than 10% in efficiency when they got hot. I can see investing in water cooling them back then, but suspect that technology trends have already made this product obsolete. If they really can cool the panels at a price + reliability + installation complexity comparable to conventional panels, it might be worth it. However, our heat pump water heater is under 10% of our electricity bill, so if it's cheaper to just add 10% more panels + batteries, then this product seems like a non-starter to me. I guess it's possible this would make sense for heating swimming pools (they create an extremely large reservoir for the waste heat during the summer).

BHSPitMonkey 3y ago

For some homeowners looking at a residential installation, the added independence itself is a feature (as is the autonomy to be able to slightly accelerate the world's shift to renewables -- the average person does not get to participate in deciding when and where to build a grid-scale solar installation). Of course, reducing a home's energy consumption would be even more preferable than just offsetting it with localized generation - but reality is complicated.

toast0 3y ago
I think the autonomy is the big thing. Redundancy is nice, but many or possibly most residential rooftop solar installs are grid tie only; adding the ability to power locally when the grid is down adds signifigant expense. Tarriffs are a thing to. It's common for rooftop generation to offset grid usage, but if you used your construction budget to buy into a larger project, you would likely not be able to offset usage, you'd more likely earn wholesale rates on generation at the facility and pay retail rates on usage at home. Probably you get more generation capacity, and maybe that works enough, but probably not. There's also a lack of these projects to buy into.
SoftTalker 3y ago
As a homeowner, the last thing I want to do is own and maintain the equipment to provide electric power. I will gladly pay a utility to take care of this for me. A home solar system with battery storage and an automatic transfer switch and interconnected to feed power back to the grid is a complicated setup and I want no part of owning or maintaining that.
- Scoundreller 3y ago
  All comes down to reliability, no? People probably said the same in the transition from simple and reliable ice boxes with ice block delivery to electric fridges.
- idiotsecant 3y ago
  I think that's why parent post said some home owners. Some people like coconut. As a person i, however, hate coconut.

jl6 3y ago

> For the same reason, the enthusiasm for the idea of installing solar plants in north africa and exporting power over interconnectors to Europe is gone. Are you quite sure, when you factor in the cost and availability of land?

derriz 3y ago
Yes - all the serious proposals are dead (the xlinks guy is a grifter) because underwater HDVC costs have risen while panel prices are a tenth of what they were. Not only the finances, but (as I described in another comment), the security aspects of depending on fixed infrastructure in unaligned and relatively politically unstable countries are very unpalatable. Such infrastructure is incredibly vulnerable and difficult to protect.

1-more 3y ago

> Putting solar panels on roofs doesn't make a lot of sense to me. Per kWh, rooftop domestic PV costs can be u[p]to 10 times more expensive on a levelized cost basis Yeah an idea I've had kicking around for a bit: if my roof is a good place for solar, it should make some kind of sense to lease it out to someone else who owns the panels and their output. I've never heard of anyone making that arrangement. There are people near me who own property with no water rights who are able to lease that land out to solar utilities. I'm not against solar and I do think that we need to have every available square inch of the world making energy if we're to survive the next century. I'm just saying that the current incentives kind of don't support it.

SoftTalker 3y ago
A residential roof is too small to make that idea interesting to anyone who is looking to rent space for solar panels.
- wffurr 3y ago
  Leasing a solar system on one’s roof is a thing, either fixed or as a power purchase agreement: https://www.sunrun.com/solar-lease https://www.sunrun.com/solar-lease Leasing the roof itself to the solar company less so. Though the difference isn’t clear. In theory you get a deal on your power, but it really depends on the terms of the lease compared to your local utility’s prices.
regularfry 3y ago
Up until 2019, exactly that type of scheme was very popular with installers in the UK.
- 1-more 3y ago
  Interesting! What happened in 2019? And sorry I'm speaking in kind of broad strokes here; I live in the US and don't own my roof so I haven't gone as deep into this as I'd like.
  - 3y ago

PaulKeeble 3y ago

They are doing this in the UK, a high voltage DC line is being connected to Northern Africa where power where about 2.5-5GW of power will be produced. Its very viable economically but I also think we have more than enough roof space for solar panels and surround sea for offshore wind to meet our power needs for the foreseeable future. Even if a commercial installation is half the price per KWh the economics still work out personally. The reason is a combination of taxes, profits and substantial business overheads that make personal Solar substantially cheaper than the current grid power which is all tied to gas prices. I am about on average 9p a KWh over the life of a Solar system which I can export for 15p currently and buying from the grid is 45p through the day. Its a substantial saving yet wholesale prices are hovering on average around the same 9p. The overheads of the grid and businesses are most of the cost and substantial.

derriz 3y ago
You're talking about Xlinks? They are nowhere near doing it. They have been talking about it since 2018 and trying to get investors to give them money but despite favourable press and interest from politicians, a heavyweight board, nobody who has looked at their business plan has stepped up to the plate to back the project. Desertec is the other one which has raised nothing despite touting a similar idea since 2008. Xlinks is going nowhere - in fact the founder, Simon Morrish, seems to be mostly spending his time on other projects these days. Even their website claimed last year that the £16B project could be profitable if a CFD at £48/MWh (CDF is a type of contract electricity suppliers bid for in UK auctions to win 15 year contracts to supply electricity). Unfortunately local solar pv, on-shore and off-shore wind auction prices in the last auction round were all lower than this. Regarding local subsidies and supports for rooftop solar, of-course it can make sense for an individual. My point is that on aggregate, it does not make sense - if the government is going to spend $X to encourage the production of solar PV, then supporting rooftop solar provides a poor return on the subsidy. And the difference is more than half the price - typically the multiple is 3 or 4 times cheaper.

ZeroGravitas 3y ago

What you say in your last paragraph also applies to rooftop solar. You have to weigh up better efficiency far away against local generation and account for the extra cost of transmission. If PV costs are dropping faster than transmission, which they are, then local generation gets more desirable.

idiotsecant 3y ago

What % overbuild do I need to generate power at night?

alvah 3y ago
Clearly a sarcastic question, but as solar panels become vastly cheaper, the battery storage requirements to effectively guarantee power on demand become much less onerous. The kWh of backup required for a solar PV system sized to maximum demand is much more than (e.g.) a PV system sized to 2x maximum demand.
adrianN 3y ago
Hydrogen storage has a round trip efficiency of about 40%, so you need less than 2.5 times overbuild.

AtlasBarfed 3y ago

- the grid investment is nil, - it increases the resiliency of people in emergency situations like storms, hurricanes, tornadoes, earthquakes, mudslides - there is LOTS of real estate so the "hidden cost" of dedicating land to solar panels isn't needed. Finally, I feel residential solar is a ripoff currently, because there is some degree of price fixing. 10x more expensive for LCOE? That is a policy problem, not a real economic reality. 2x or even 3x I could see, but 10 fucking times? Some thing with batteries to consumers. The tool makers like lawnmowers / power tools / etc are simply raking consumers over the coals with vastly overpriced batteries compared to what the BEV companies are getting. Maybe the magical hand of economics will finally deliver for the end consumers, but currently it is not.

callalex 3y ago

Rooftop solar makes sense when independence is a key need. Where I live (San Francisco Bay Area, California, USA) the power utility is extremely corrupt. This makes their service the terrible combination of unreliable (sometimes being disconnected for several days at a time) and extremely expensive (they charge about half a dollar per kWh). Being as independent from them for my energy needs as possible means buying solar, and my roof is the only open space I have available.

perlgeek 3y ago

> Putting solar panels on roofs doesn't make a lot of sense to me. Per kWh, rooftop domestic PV costs can be unto 10 times more expensive on a levelized cost basis [...] compared to a ground based utility/grid scale installation. This is an odd either/or attitude. If you own a house with a roof, there are factors that decide whether putting PV on your roof is economically sustainable for you or not. If you do the analysis, and the answer is that it pays off in a sufficiently short time frame, then install PV, even if utility-scale PV somewhere else would be 100x cheaper. As long as the hypothesized utility PV installations don't bring down the electricity cost so much that your own installation becomes unsustainable, the two are basically independent.

rstuart4133 3y ago

> rooftop domestic PV costs can be unto 10 times more expensive on a levelized cost basis ... compared to a ground based utility/grid scale installation Your "can be" hides a lot of sins. Looking at the data you quote domestic PV also "can be" 1/2 the cost of of ground based utility installation. The truth is between those extremes and will vary a lot depending on situation. But here is something that doesn't vary so much: the difference between the retail cost and wholesale cost is around a factor or 3. Translation: utility solar has to be around 3 times cheaper than domestic before it makes sense to a household. I don't think it's terribly surprising there are a lot of places that factor of 3 tilts the balance in favour of domestic PV.

bogzxo 3y ago

here in south africa where we have load shedding and sometimes don’t have power 8 hours a day, so they are necessary if possible.