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Photovoltaics: Difference between revisions
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'''Solution:''' Find some other photovoltaic tech based on more abundant minerals. Sacrificing some efficiency is okay, for the sake of making cheaper, more scalable solar panels. <br />{{more|solar/challenge 1}} | '''Solution:''' Find some other photovoltaic tech based on more abundant minerals. Sacrificing some efficiency is okay, for the sake of making cheaper, more scalable solar panels. <br />{{more|solar/challenge 1}} | ||
== | ==Land usage== | ||
{{sum| | {{sum|Reasonable}} | ||
{{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. | |||
<br />Does not include most farm land.<br /> | |||
<br />https://ourworldindata.org/land-use | |||
}} | |||
{{dp | |||
|rooftops_area | |||
|(1/4) built_up_land | |||
|Surface area of all rooftops in the world | |||
|Quick estimate based on the assumption that about a quarter of all "urban and build-up land" consists of rooftops or something else suitable for solar panels. | |||
}} | |||
{{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><br /><nowiki> | |||
https://www.newport.com/t/introduction-to-solar-radiation</nowiki><br /><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><br /><nowiki> | |||
</nowiki><br /><nowiki> | |||
Does not include the fuel used in generating electricity. See [energy.tes] for that.</nowiki><br /><nowiki> | |||
</nowiki><br /><nowiki> | |||
Citation: "Key World Energy Statistics 2020" IEA</nowiki><br /><nowiki> | |||
- Page 47 - Simplified energy balance table - World energy balance, 2018</nowiki> | |||
}} | |||
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[[ | --> | ||
In the simplest average case, [[solar rooftops]] are all that would be needed. | |||
[[Solar farms]] | <center><tab name="quick maths"> | ||
{{calc | |||
|rooftops_area * solar_panel.efficiency * sunlight_average | |||
|% energy.tfc | |||
|||If all rooftops in the world were covered with solar panels, the energy produced is just about equal to today's global energy demand. | |||
}} | |||
</tab></center> | |||
But of course life is more complicated: | |||
* '''Geography:''' Some regions may need more energy than the ''local'' rooftops can provide, while other regions may be the opposite. Power lines can only reach so far.<small> | |||
** Countries with extreme temperatures need more energy for [[heating and cooling]]. | |||
** Local ''industry'' is a major part of energy demand, but it doesn't correlate neatly with local rooftop area. | |||
** Very high-density cities may not have enough rooftop space per capita. Sides of buildings have limited sun when they're obscured by other buildings. | |||
*** This isn't a problem for ''most'' North-American cities, as the surrounding suburbs (low density) could produce enough surplus power for the inner city (high-density). <sup>[CASE STUDIES needed]</sup></small> | |||
* '''Inequality:''' Most of the world today is in poverty. If every nation was ''developed'', the demand for energy would be a lot higher than the status quo used in the calculation above. | |||
* '''Lower efficiency:''' Since conventional solar panels are too mineral-intensive to scale up, we need some alternative which will probably be less efficient at converting sunlight into electricity. | |||
But there is at least one factor that makes this easier: | |||
* [[Electric vehicles]] are more energy-efficient than gasoline or diesel vehicles. | |||
In general, [[rooftop solar]] can almost always provide enough ''electricity'' for a house (and even charge an [[EV]] in many cases), but not always enough [[heating]]. | |||
{{minor|Burning [[hydrogen gas]] (generated from [[wind]] power) could probably make up the difference.}} | |||
[[Solar farms]] may be needed in cases where solar rooftops aren't enough. The amount of [[land]] required would be far less than what's used for agriculture. {{qn}} Solar panels should best be placed in areas with no fertile soil. They don't play well with agriculture, because (unlike wind power) solar panels block the sun that plants need to grow. | |||
{{minor|And although there are some crops that like the shade, they could have just as well been grown in the shade of full-sun crops instead. See: [[polyculture]].}} | |||
Compared to [[wind power]], solar is far less land-intensive {{x|about 50x less, based on the fact that the atmosphere converts about 2% of the sun's energy (that hits the Earth) into winds}} but far more invasive to the land it ''does'' use. | |||
==Energy in production== | ==Energy in production== | ||