Archive:000/Rooftop solar - Revision history

Elie: Elie moved page Rooftop solar to Archive:000/Rooftop solar without leaving a redirect: Huge_refactor

2024-10-26T20:30:09Z

Elie moved page Rooftop solar to Archive:000/Rooftop solar without leaving a redirect: Huge_refactor

← Older revision	Revision as of 16:30, 26 October 2024
(No difference)

Elie at 14:05, 14 January 2023

2023-01-14T14:05:48Z

@@ Line 1: / Line 1: @@
 Rooftops are a good place to put [[solar]] panels, because:
 * They are close to where the [[energy]] is typically used.
@@ Line 8: / Line 9: @@
 ** Exception: [[heating]] in cold parts of the world
 ** Exception: high-density cities
 * '''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]]
 ** [[solar panel recycling|Recycling solar panels]] at their end-of-life
 ** [[Energy storage]]
@@ Line 78: / Line 80: @@
 ==Charging electric vehicles==
-If we assume one electric car per house, we'd need to add another 543 watts per household. 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.
+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
@@ Line 115: / Line 117: @@
 ==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.
 ==Safety==
@@ Line 140: / Line 171: @@
 See also: [[Solar powered factories]]

Elie: /* Potential */

2023-01-03T06:54:09Z

Potential

← Older revision		Revision as of 02:54, 3 January 2023
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	}}		}}

	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?		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

Elie at 05:37, 3 January 2023

2023-01-03T05:37:45Z

← Older revision		Revision as of 01:37, 3 January 2023
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	Rooftops are a good place to put [[solar ~~panels~~]], because:		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.
Line 10:		Line 10:
	* '''Hard problems:'''		* '''Hard problems:'''
	** Manufacturing enough solar panels without needing too many rare [[minerals]]		** Manufacturing enough solar panels 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]]

Line 30:		Line 30:
	}}		}}

	Assume we find a way to manufacture this many solar panels [[solar ~~panel minerals~~\|without overrunning our mineral reserves]]. How much energy could we generate?		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
Line 63:		Line 63:


	In simple terms, this means we could just about meet the world's energy demand, with solar alone. {{x\|~~Note: Today's~~ energy ~~demand is subject~~ to ~~change~~. ~~Some factors that~~ could decrease it: [[~~Walkability~~]] and voluntary [[frugalism]] in the western world~~. Some factors that~~ could ''increase'' it: ~~More~~ nations becoming 'developed' in a way that copies the current western world.}}		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.

Elie: /* Challanges */

2022-12-28T06:04:24Z

Challanges

← Older revision		Revision as of 02:04, 28 December 2022
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	* Keeping snow & ice off the panels		* Keeping snow & ice off the panels
	* Making solar panels cheaper, more lightweight, less demanding of rare minerals. This is generally at odds with having more efficient solar panels.{{rn}}		* Making solar panels cheaper, more lightweight, less demanding of rare minerals. This is generally at odds with having more efficient solar panels.{{rn}}
			* Environmental tradeoffs for houses that are surrounded by tall [[trees]]

	==Combined photovoltaic and thermal panels==		==Combined photovoltaic and thermal panels==

Elie: Created page with "Rooftops are a good place to put solar panels, because: * They are close to where the energy is typically used. * They need no extra land (unlike solar farms). That's an environmental footprint avoided. '''Summary:''' * In most cases, rooftop solar ''could'' provide enough energy for '''homes''', other '''buildings''', and '''charging''' electric vehicles. Exception: heating in cold parts of the world Exception: high-density cities * '''Ha..."

2022-12-28T05:43:48Z

Created page with "Rooftops are a good place to put solar panels, because: * They are close to where the energy is typically used. * They need no extra land (unlike solar farms). That's an environmental footprint avoided. '''Summary:''' * In most cases, rooftop solar ''could'' provide enough energy for '''homes''', other '''buildings''', and '''charging''' electric vehicles. ** Exception: heating in cold parts of the world ** Exception: high-density cities * '''Ha..."

New page

Rooftops are a good place to put [[solar panels]], because:
* They are close to where the [[energy]] is typically used.
* They need no extra [[land]] (unlike [[solar farms]]). That's an environmental footprint avoided.

'''Summary:'''
* In most cases, rooftop solar ''could'' provide enough energy for '''homes''', other '''buildings''', and '''charging''' [[electric vehicles]].
** Exception: [[heating]] in cold parts of the world
** Exception: high-density cities
* '''Hard problems:'''
** Manufacturing enough solar panels without needing too many rare [[minerals]]
** [[Recycling solar panels]] at their end-of-life
** [[Energy storage]]

==Potential==
First let's estimate how much rooftop area is available globally. For lack of better data, let's just assume that rooftops {{x|more precisely: the ''surface area'' of all ''suitable'' rooftops combined}} are 1/4 of all "urban and built-up land" area. This assumption isn't perfect {{x|For one, there may be a lot of homes with rooftops that can't support the weight of solar panels - especially in the global south. Hopefully this problem could be mitigated with more [[lightweight solar panels]]. Well if the 1/4 turns out to be an overestimate, it still might be offset by the possibility of other suitable locations to install solar panels on built-up land. However, [[solar roadways]] are of questionable viability.}} but hopefully it's good enough.

{{dp
|built_up_land
|1500000 km^2
|Urban land, suburbs, industrial areas - global total
|This is home to the vast majority of people on Earth.
 Does not include most farm land. 
 https://ourworldindata.org/land-use
}}
{{calc
|(1/4) built_up_land
|km^2
|
}}

Assume we find a way to manufacture this many solar panels [[solar panel minerals|without overrunning our mineral reserves]]. How much energy could we generate?

{{dp
|<nowiki>solar_panel.efficiency</nowiki>
|<nowiki>17%</nowiki>
|<nowiki>Efficiency of an average solar panel</nowiki>
|<nowiki>Some solar panels are more efficient than this, but they tend to be expensive and contain more rare metals.</nowiki>
}}
{{dp
|<nowiki>sunlight_average</nowiki>
|<nowiki>200 watts per m^2</nowiki>
|<nowiki>Solar irradiance, averaged over a whole year INCLUDING nights, cloudy days, etc.</nowiki>
|<nowiki>Note: This varies by region.</nowiki> <nowiki>
https://www.newport.com/t/introduction-to-solar-radiation</nowiki> <nowiki>
http://www.ftexploring.com/solar-energy/insolation.htm</nowiki>
}}
{{dp
|<nowiki>energy.tfc</nowiki>
|<nowiki>9937.70 Mtoe/year</nowiki>
|<nowiki>Global energy usage - total final consumption (TFC)</nowiki>
|<nowiki>Includes: fuel (80.7%) + electricity (19.3%) AFTER it is generated.</nowiki> <nowiki>
</nowiki> <nowiki>
Does not include the fuel used in generating electricity. See [energy.tes] for that.</nowiki> <nowiki>
</nowiki> <nowiki>
Citation: "Key World Energy Statistics 2020" IEA</nowiki> <nowiki>
- Page 47 - Simplified energy balance table - World energy balance, 2018</nowiki>
}}
{{calc
|(1/4) built_up_land * solar_panel.efficiency * sunlight_average
|% energy.tfc
}}

In simple terms, this means we could just about meet the world's energy demand, with solar alone. {{x|Note: Today's energy demand is subject to change. Some factors that could decrease it: [[Walkability]] and voluntary [[frugalism]] in the western world. Some factors that could ''increase'' it: More nations becoming 'developed' in a way that copies the current western world.}}

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.

==Locality==
High-rise buildings don't have enough rooftop surface to power the whole building. But in some cases, a dense inner-city could be powered by excess energy from suburban house rooftops nearby. In what cases is this viable? ''Population density'' could be a useful measuring stick:

{{calc
|(1/4) sunlight_average * solar_panel.efficiency / (2000 watts per capita)
|people per km^2
}}

^ If your ''whole'' municipality's population density is greater than this number, you would probably need [[solar farms]]. {{x|And of course it also depends on how much energy people use; in this estimate we're assuming 2000 watts per capita, which is hopefully enough for a modern life - especially if living in a high rise.}}

==Charging electric vehicles==
If we assume one electric car per house, we'd need to add another 543 watts per household. 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.

{{dp
|<nowiki>average_us_vehicle.mileage_by_time</nowiki>
|<nowiki>32 miles/day</nowiki>
|<nowiki>Distance driven by the average American vehicle</nowiki>
|<nowiki>Top Numbers Driving America's Gasoline Demand</nowiki> <nowiki>
https://www.api.org/news-policy-and-issues/blog/2022/05/26/top-numbers-driving-americas-gasoline-demand</nowiki>
}}
{{dp
|<nowiki>electric_car.efficiency</nowiki>
|<nowiki>100 miles per 34.6 kWh</nowiki>
|<nowiki>The "gas mileage" equivalent for an average electric car.</nowiki>
|<nowiki>Average Electric Car kWh Per Mile [Results From 231 EVs]</nowiki> <nowiki>
ecocostsavings.com › average-electric-car-kwh-per-mile </nowiki>
}}
{{dp
|<nowiki>li_ion.charge_discharge_efficiency</nowiki>
|<nowiki>85%</nowiki>
|<nowiki>When you charge a lithium-ion battery, this much of the energy can be recovered. The rest is lost as heat.</nowiki>
|<nowiki>Range: 80 to 90 %</nowiki> <nowiki>
from wikipedia; haven't found original source yet</nowiki>
}}
{{calc
|<nowiki>average_us_vehicle.mileage_by_time / electric_car.efficiency / li_ion.charge_discharge_efficiency</nowiki>
|<nowiki>watts</nowiki>
}}
Would the average suburban rooftop be able to provide this?

{{calc
|1000 square(feet) * sunlight_average * solar_panel.efficiency
|watts
}}
Yes, seems doable. Obviously it depends on the size of the rooftop (in this example, we assume 1000 square feet). {{x|If we factor in all the car owners in dense cities, it might become less viable. Good thing dense areas are good candidates for [[walkability]].}}

==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.

==Safety==
* The roof needs to be able to support the weight of the solar panels.
* Installing the panels, without the proper skills and knowledge, could result in electrocution or fire hazards.
** Maybe this risk could be mitigated with enough engineering: Could rooftop solar kits be designed to be user-friendly ''and'' safe enough for non-professionals to install them?{{rn}}

==Challanges==
* Some roofs might be more suited for solar panels than others.{{rn}}
* Installation ''might'' need very specialized [[labor]].{{rn}}
* Keeping snow & ice off the panels
* Making solar panels cheaper, more lightweight, less demanding of rare minerals. This is generally at odds with having more efficient solar panels.{{rn}}

==Combined photovoltaic and thermal panels==
[[Solar thermal panels]] use the sun to directly heat water & air, without electricity as an intermediate. There are some designs that integrate with photovoltaics, to really make the most of the sun for both [[heating]] and [[electricity]]. But in which weather conditions is this viable - would it still work in colder winters?{{rn}} How does it compare to pure photovoltaics combined with [[heat pumps]]?

==Factories==
Factories make up a significant share of global [[energy demand]] - more than homes and other buildings. Factories could also mostly run only during the day to make use of peak solar energy without much need for [[energy storage]]. But could a factory's rooftop provide most of energy needed to power the factory?{{rn}}

If not, there may be other solutions:
* If the factory is near a city with many houses producing excess energy from ''their'' rooftops during the day, the factory could use that as an energy source.
* If the factory is far from cities, it might happen to be in an area where [[wind power]] is viable.
* Perhaps the factory could scale down and [[microfactories|decentralize production]]. Beware of caveat: {{x|This could easily be overall worse for the environment if existing factory equipment has to be abandoned in favor of smaller equipment to be built from scratch. But there are probably some cases where this wouldn't have to happen.}}

See also: [[Solar powered factories]]