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Satellite powered estimation of global solar potential

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Re: Satellite powered estimation of global solar potential

#151
post #123
post #12

This is a very impressive refinement of their existing tool, but is this type of advanced calculation of roof-pitch (etc.) still relevant? Haven't we more or less concluded that a million piecemeal rooftop installations of solar are about the worst way to do it? More complicated and expensive to permit and install, less efficient operation, difficult to repair, difficult to insure, difficult to upgrade, inefficient t…

Australia manages to install rooftop solar at well under half the cost the USA does (most of that is soft costs) and integrate large amounts of it into the grid. As of lunchtime today, nearly 50% of all electrical generation on the national grid was rooftop solar (and another ~10% was utility-scale solar). Rooftop solar works just fine if utilities don’t actively try and obstruct its use.

    > As of lunchtime today, nearly 50% of all electrical generation on the national grid was rooftop solar
Wow, this is incredible. Can you share your source? I would like to learn more!

Re: Satellite powered estimation of global solar potential

#152
post #73
post #68

Earlier quoted context omitted.

Yeah, don’t over look the fact that the thermal demand from space conditioning homes is way higher on a per capita basis in a suburban context compared to an urban context with multi-family housing/apartments etc. There’s just way more air volume to condition per person, generally more inefficient systems, etc.

Even for the same amount of living space, apartments are way more efficient. A typical apartment unit is surrounded by other units up/down/left/right, so only two sides are exposed to outside air. A single house is exposed on five sides.

Yeah we refer to this as the heat loss form factor of the building, which is determined largely by the surface area to volume ratio (so you have a square-cube relationship at work) as well as the the number of floors in conjunction with the roof area. With more floors, the heat transfer through the roof (which can be substantial, as mentioned by a sibling comment) is less significant for the same roof area (after normalizing for the gross floor area).

Same goes for the slab/foundations (which can also have substantial thermal transfer in many contexts).

Re: Satellite powered estimation of global solar potential

#153
post #30

Earlier quoted context omitted.

There’s not always a lot of freedom to control roof angles like that - it might eg be directly determined by the orientation of the street - and even if there is, it might come into conflict with other thermal considerations. For instance, perhaps orienting the building such that the roof midline is E/W and the surface is due south results in more windows pointed due south, which in turn drives much more solar gain o…

> more windows pointed due south, which in turn drives much more solar gain on the interior and greater cooling loads as a result C'mon ... people figured this out in 70s ... and centuries before that in various parts of the world. You put a shade above the window the excludes direct summer sun, but allows direct winter sun to enter the window. The angle and extent of the shade depends on where you are in the world.…

Oh I’m totally with you! There is a long and storied history of passive design strategies, and exterior shading is one of the oldest ones out there!

But what I stated is plainly true, and many people simply don’t want exterior shades (or just don’t think about it).

The point I was trying to make was just that there are thermal implications to the orientation, and you should think those through (using thermal simulations can help detect these issues) and come up with appropriate strategies (thermal simulations can help validate them). Maybe you don’t want shades, but you would be okay with emissivity coatings for your windows. Or maybe you just want to position windows on both sides of the home with continuous air volumes connecting them to promote natural ventilation. Maybe you can take advantage of thermal mass. The list goes on…

Re: Satellite powered estimation of global solar potential

#154
post #12

This is a very impressive refinement of their existing tool, but is this type of advanced calculation of roof-pitch (etc.) still relevant? Haven't we more or less concluded that a million piecemeal rooftop installations of solar are about the worst way to do it? More complicated and expensive to permit and install, less efficient operation, difficult to repair, difficult to insure, difficult to upgrade, inefficient t…

At a certain point shouldn't things get good enough you don't really need a traditional power grid?

Grids are pretty much the best solution available because any kind of good/service that can be transported at close to light-speed benefits tremendously from ubiquitous connectivity.

Smarter grids are an even better solution; batteries backing local high-variance demand combined with rapidly negotiated requests for transmission power to meet expected future demand (and then stored in the batteries) reduces (electrical) inefficiency to a minimum.

Re: Satellite powered estimation of global solar potential

#155

Earlier quoted context omitted.

There's the perception that it's an "either" question. When in reality its both. Home solar is a big win, and if nothing else allows capital to be sourced from a million home owners. Centralized solar is a big win, generating grid power Erich is obviously important. It's not a question of either, it's a question of both.

I should have made it clear: I’m referring to people who are adamantly opposed to large solar installations, apparently because it’s a threat to agriculture? It’s very odd, but I see yard signs and bumper stickers everywhere in rural Indiana.

Do you think some farms in rural Indiana will make more money by converting to a solar power park? I could imagine it, and I could imagine that some people would feel threatened by this change.

Re: Satellite powered estimation of global solar potential

#156
post #136

Earlier quoted context omitted.

Ahh, ok the tool sucks it doesn’t seem to calculate based on your current cost per kWh or the local cost per kWh. It’s ignoring inflation on those calculations, acting like your electric bill will be the same in 20 years. It’s also ignoring residual value in the system after 20 years they typically last 25-30, and you don’t pay taxes on savings. There install estimates where also really high for my area, but I don’t…

Your electric bill 20 years from now is just as likely to go down as it is to go up. In two decades, we could see advancements like mobile generators offering free power, ultra-affordable battery packs delivered to homes to meet energy needs, or even the widespread adoption of low-cost fusion energy. The key takeaway is that predicting the future cost of electricity is as challenging as it was to predict today’s sola…

    > mobile generators offering free power
Wow, where is this magical place? I want to move there. :)

Re: Satellite powered estimation of global solar potential

#157
post #60

Earlier quoted context omitted.

i've heard of some business models that install these and have you pay what would be the difference to your electric bill to the company until they pay themselves off, not sure if the panels last long enough to make that work though

Yes. In Germany they are selling a lot of models, but none, I mean, really, none asked about the rentability. So I went to a neighbour who just installed his 25kW and was very proud and happy, and asked him, in how many years is the return of investment. Siderated, he could not answer and then a few days later, with a very stern face: 25 years or more because if more people install these, the price that the city is p…

25kW? That is crazy huge! How many panels? What does this guys house (mansion!?) look like? Google tells me that average installation size is about 7-8kW.

Re: Satellite powered estimation of global solar potential

#158
post #28

Earlier quoted context omitted.

With rooftop solar there's a path towards mass deployment that other alternative electricity generation solutions currently lack. Rooftop solar for residential houses doesn't require permits or planning, and can be done by individuals within a reasonable budget, unlike solar farms or rooftop nuclear.

> Rooftop solar for residential houses doesn't require permits or planning Either you're assuming residential battery storage systems replacing the grid, or your ignoring the connecting rooftop solar to the grid requires permits and planning (the grid may not be able to handle it).

Depends on your jurisdiction. UK home solar under 4kW doesn't require permission.

Re: Satellite powered estimation of global solar potential

#159

Earlier quoted context omitted.

i've heard of some business models that install these and have you pay what would be the difference to your electric bill to the company until they pay themselves off, not sure if the panels last long enough to make that work though

One of these wouldn't sign me up as they couldn't offer any savings (92% of my use is off peak, around 16ct NZD (9 USD) / kWh). A lot of the time such companies pray on people on stupid plans (or those paying thru the nose for "exclusively renewable") power.

Woah, your electricity is so cheap! Is it mostly hydro?

Re: Satellite powered estimation of global solar potential

#160

This is a very neat exercise but I don’t think it’s going to create change. These models already exist and I’ve never met anyone who said their reason for not investing in solar is because they felt the accuracy of existing models is not good enough. I say this as someone who lives on a part of the world where a large % of the inhabitants could have solar but do not - and I find it sad, frustrating and puzzling. Bigg…

This chart on the progress of PV cell efficiencies always blows me away: https://en.wikipedia.org/wiki/Photovoltaics#/media/File:NREL...
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