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Archive:000/Rooftop solar: Difference between revisions
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Rooftops are a good place to put [[solar | [[File:RooftopSolar1.jpg|thumb]] | ||
Rooftops are a good place to put [[solar]] panels, because: | |||
* They are close to where the [[energy]] is typically used. | * They are close to where the [[energy]] is typically used. | ||
* They need no extra [[land]] (unlike [[solar farms]]). That's an environmental footprint avoided. | * They need no extra [[land]] (unlike [[solar farms]]). That's an environmental footprint avoided. | ||
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** Exception: [[heating]] in cold parts of the world | ** Exception: [[heating]] in cold parts of the world | ||
** Exception: high-density cities | ** Exception: high-density cities | ||
** Note: People would have to charge their electric vehicles during the day. | |||
* '''Hard problems:''' | * '''Hard problems:''' | ||
** Manufacturing enough solar panels without needing too many rare [[minerals]] | ** Manufacturing enough solar panels [[solar/challenge 1|without]] needing too many rare [[minerals]] | ||
** [[Recycling solar panels]] at their end-of-life | ** [[solar panel recycling|Recycling solar panels]] at their end-of-life | ||
** [[Energy storage]] | ** [[Energy storage]] | ||
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}} | }} | ||
Assume we find a way to manufacture this many solar panels [[solar | Assume we find a way to manufacture this many solar panels [[solar/challenge 1|without overrunning our mineral reserves]]. How much energy could we generate? | ||
{{dp | {{dp | ||
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In simple terms, this means we could just about meet the world's energy demand, with solar alone. {{ | In simple terms, this means we could just about meet the world's energy demand, with solar alone. {{p|Less energy would be available if the solar panels were less efficient due to using fewer minerals.<br /><br />Energy ''demand'' could also decrease, given certain factors:<br />- [[walkability]] and [[public transit]]<br />- voluntary [[frugalism]] in the western world especially<br />- [[electric vehicles]] as long as they don't take too much energy to manufacture<br /><br />Energy demand could also ''increase'', given other factors:<br />- more nations becoming 'developed' in a way that copies the current western world<br /><br />For all intents and purposes, let's assume that all these factors would balance each other out, roughly.}} | ||
However, some of the energy might be generated in the wrong places. Low-density cities/towns may generate too much; high-density cities may not generate enough. | However, some of the energy might be generated in the wrong places. Low-density cities/towns may generate too much; high-density cities may not generate enough. | ||
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==Charging electric vehicles== | ==Charging electric vehicles== | ||
If we assume one electric car per house, we'd need to add another 543 watts | If we assume one electric car per house, we'd need to add another 543 watts {{x|Note: This is ''power averaged over time''. Peak power would be significantly higher, but that's not a big deal as vehicles could be charged during peak sunlight.}} per household: | ||
{{dp | {{dp | ||
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==Energy storage== | ==Energy storage== | ||
So far we've looked at ''watts averaged over time'', but actual raw watts are much higher during the day, and almost zero at night. We need [[energy storage]] to smooth things out. | So far we've looked at ''watts averaged over time'', but actual raw watts are much higher during the day, and almost zero at night. We need [[energy storage]] to smooth things out. | ||
As a bare minimum, a house should at least have nighttime electricity for lights, appliances, cooking, computers, entertainment, etc. Assume we need to store about 12 hours of ''average-case power consumption'' {{x|obviously this also depends on a lot of factors, such as time-of-year and consumption patterns. Let's do a generous estimate that assumes that heating doesn't need to be done at night, as heat can be stored in other ways much cheaper than batteries.}} for that: | |||
{{dp | |||
|<nowiki>usa.residential_essential_baseload</nowiki> | |||
|<nowiki>641 billion kWh/year</nowiki> | |||
|<nowiki>Bare minimum residential electricity that must be available 24/7, in the USA</nowiki> | |||
|<nowiki>Does not include heating/cooling, because there are ways to store warmth/cold more cheaply than storing electricity.</nowiki><br /><nowiki> | |||
</nowiki><br /><nowiki> | |||
Source: https://www.eia.gov/tools/faqs/faq.php?id=96&t=3</nowiki><br /><nowiki> | |||
</nowiki><br /><nowiki> | |||
Using rows in table: "Total consumption", minus "Space cooling", minus "Space heating", minus "Water heating", minus exactly 1/2 of "Other uses". | |||
</nowiki><br /><nowiki> | |||
Note: This can be understood as ''average power''. The required ''peak power'' may be higher, as this consumption may be concentrated into afternoon/evening hours.</nowiki> | |||
}} | |||
{{dp | |||
|<nowiki>usa.homes</nowiki> | |||
|<nowiki>142153010</nowiki> | |||
|<nowiki>Number of households in the USA</nowiki> | |||
|<nowiki>Includes houses, apartments, condos and more.</nowiki><br /><nowiki> | |||
</nowiki><br /><nowiki> | |||
Housing units - U.S. Census Bureau QuickFacts: United States</nowiki><br /><nowiki> | |||
[https://www.census.gov/quickfacts/fact/table/US/VET605221]</nowiki> | |||
}} | |||
{{calc | |||
|12 hours usa.residential_essential_baseload / usa.homes | |||
|kWh | |||
}} | |||
Electric vehicles already contain energy storage. Best-case scenario, people charge them during the day. {{x|People would be motivated by the massive price difference between daytime electricity (incredibly cheap) and nighttime electricity. Daytime charging comes with a few other logistical challenges,<!--TODO: make a new section or page on this--> but it still has the potential to become a social norm.}} | |||
==Safety== | ==Safety== | ||
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See also: [[Solar powered factories]] | See also: [[Solar powered factories]] | ||
==External links== | |||
* [https://www.energy.gov/eere/solar/solar-rooftop-potential Solar Rooftop Potential] - U.S. Department of Energy | |||