I feel like this is the most noobish question ever. Anyway, imagine an asteroid hits Earth and the atmosphere is now full of particles, successfully blocking the Sun from Earth. There are people still alive on the planet.

Assuming the sun isn't 100% blocked, enough for people to see their hands in front of their faces in "daylight" at least, does this affect electricity and how?

*Further Clarification: I'm referring to the electricity we use on our day to day lives from light bulbs to televisions and so on. So if the sun is blocked, will our homes still be running on electricity - that's the electricity I'm referring to.

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    $\begingroup$ With the Sun blocked out, electricity is really the least of your problems. I feel like this question is indicative of our "generation"'s problem. $\endgroup$ Nov 12, 2014 at 13:30
  • $\begingroup$ Can you specify? It appears your question is referring to the fundamental concept of electricity, not power generation but it would be best to clarify as answers have gone down both routes and it is hard to choose the best answer without clarification from you. $\endgroup$
    – James
    Nov 12, 2014 at 14:56
  • $\begingroup$ I definitely mean electricity as in the power we use day to day in lightbulbs, heating, and whatever conveniences we're used to. If the sun is blocked, will buildings still have power? I'll edit the question above. $\endgroup$
    – KaguraRap
    Nov 12, 2014 at 15:01

6 Answers 6


Atmospheric dust by itself shouldn't have any major impact on generation or distribution of electricity. The two are unrelated.

However, a fraction of the Earth's electricity production is based on current solar input, either directly or indirectly. There is the obvious: photovoltaic electricity production, which globally amounted to a total of 41.4 TWh in 2012. While this is a tiny sliver compared to global electricity production (also here), the global photovoltaic electricity producting sitting at almost exactly 1% of the US electricity production of 4,310 TWh, some countries have significantly higher proportions photovoltaic electricity production than others.

You will also face indirect effects due to changing weather patterns. I would expect wind patterns to change, which may or may not have an impact on wind turbines, and you may very well see changes in other energy generation techniques as well. Blocking out such a large amount of the sunlight as you describe is going to cause global temperatures to plummet, which in human societies would lead to an increased need to provide heating in buildings (wild animals would also suffer, obviously).

In summary, electricity supply from photovoltaic generation will obviously be directly impacted by sunlight being blocked (at this scale probably to the point of providing only negligible amounts of power, if indeed any at all), and other power sources may be affected as well as exemplified above. There is of course also the risk that the power grid has been damaged, but I would expect such damage to be primarily local or possibly regional in nature following an asteroid strike; the power grid is normally designed to be able to deal with failures without triggering cascade failures, but whole areas may be cut off from the larger grid to protect the rest of the grid. You may also see secondary effects from the strike itself, but that won't be about electricity per se.

The combined effect of all the above may be to force power rationing techniques in areas where affected power sources make up a noticable fraction of the total power mix. Rolling blackouts is a power rationing technique that has been used in practice, and likely would be employed in such a scenario, assuming enough people surviving the immediate effects for society to continue to function at all. Rolling blackouts were done in Japan after the 2011 Fukushima Daiichi disaster and more-or-less immediate shutdown of almost a quarter of Japan's nuclear reactors which led to a severe short-term power shortage. Venezuela is doing something similar in 2016 in response to drought.

Generally speaking, if you can't service everybody all the time, then it might be better to simply tell people that until further notice and for defined periods of time during the days they will simply have to make do without electricity service; the alternative may very well be grid overload, which at best is going to lead to a total shutdown and automatic reset, and at worst may very well cause severe equipment damage. Backbone electricity grid transformers, isolators and so on is not something you can just walk into a store and buy; such parts often need to be manufactured to order, and delivery times of months is far from unheard of even at the best of times. Even if things are otherwise good, this is a scenario the grid operator is going to want to avoid at (almost) all costs. With modern, "smart" metering, it might even be possible to reprogram the meters such that power (watts, not watt-hours) draw above a certain threshold for a given period of time shuts down service for that user for a period of time, to reduce the peak load on the grid. Even if such provisions aren't normally allowed for, I'm sure in such a situation someone would very seriously consider the possibility.

It's also worth remembering that even though electricity can be transmitted relatively easily over short to medium distances, moving electricity over large distances is a non-trivial problem, and one mostly avoided by having reasonably local power production. So for example, having enough electricity production in South America doesn't do much to help Canada cope, and the same goes with transmission across Eurasia.



The dust in the air may generate a static charge, which in turn may increase lightning (even in the absence of storms), and blocking the sun will of course limit the effectiveness of photovoltaic cells (solar panels), if not render them outright useless.

However sunlight has no bearing whatsoever on the movement of electrons through conductors, most of which are shielded from sunlight anyway (not because the sunlight has any effect on them, but because we tend to do silly things like wrap conductors in insulators to prevent people being electrocuted or circuits being shorted). This can also be seen in the fact that you can turn on your lights when the sun sets below the horizon, and up north here we can still turn on our lights, even when the sun sets and doesn't rise again for 3 months!

Now, with such a catastrophic event, the power grid is very likely to have been disrupted if not outright destroyed. So while the physics of electricity remain unchanged, it's not merely plausible but almost a downright given that most people won't have power in their homes after this (if their homes even survived); even those far enough away from the impact to not have any direct impact on them likely suffered massive earthquakes that damaged or destroyed critical infrastructure, though those furthest from the impact are more likely to still have power or more easily repair their power grids.

  • $\begingroup$ +1 for the friction comment (the rest of the answer is good too) $\endgroup$
    – James
    Nov 12, 2014 at 14:53

A complete answer to this question needs to consider both electricity supply and demand. As far as I can see the existing questions only cover supply.

In terms of supply, the main kinds of generation which will be affected are those which depend on weather but no form of generation will be unaffected.

Electricity Supply

  • Solar Power is obviously going to be directly impacted. Photovoltaic deals quite well with diffuse/scattered light, if the intensity of light is halved, then it generates about half the power. However solar thermal, which involves concentrating sunlight, requires bright direct sunlight and won't generate at all with a badly hazed atmosphere. Fortunately nearly all solar is photovoltaic.
  • Wind Power is likely not going to be impacted much at all. Wind has multiple causes, but as a rule wind is caused more by the rotation of the planet than by the sun. The cold outer planets have very high wind speeds. Wind turbines could still be damaged by dust or freezing temperatures (in locations where these weren't expected environmental hazards).
  • Hydro Power is ultimately dependent on patterns of rainfall, snowfall and snow melt. Reduced temperatures will reduce evaporation, reducing rainfall and snowfall. Snow melt will also be reduced. Some hydro dams can store sufficient water for several years of power generation and such large lakes will also resist freezing so if they are full when the asteroid strikes their output will not be immediately impacted. Hydro power plants without enormous reservoirs could be more quickly impacted, and might stop producing altogether if their river completely freezes.
  • Thermal and Nuclear Power may be badly affected where the lake or river which they rely on for cooling completely freezes, although it may be possible to use the hot water from the power station to maintain an artificial lake of tepid water. In the cases where the river dries up from lack of rain/snowmelt power generation will be halted. Distribution of fuel may also be disrupted by storms snowing in railways and roads, and ports freezing over.
  • Electricity distribution will also suffer badly. In cold climates blizzards can down power lines, sometimes leaving houses without power for weeks at a time. Areas which previously were not subject to snow or icing, suddenly will be, and the power grid will suffer extensive damage during blizzards and storms.

Electricity Demand

The impact on demand is going to depend a great deal on the climate and the proximity to the asteroid strike. In some areas nearly everyone will be killed, which will dramatically reduce demand for power. Of course in those areas the power stations will also be be badly damaged or destroyed.

In areas where most people and infrastructure survived demand might be either increased or reduced.

  • In hot climates the electricity required for air conditioning will be reduced which will reduce power demand during the middle of the day. If the temperature drops sufficiently that actual heating becomes necessary then the demand is likely to be severely increased. Reverse-cycle air conditioning can be used for heating too which is quite efficient. However in hot climates buildings tend to be poorly insulated and poorly sealed, and many people will suddenly require heating just to stay alive, and electric heaters are the quickest and simplest way of heating rooms - unfortunately they are also the least efficient. Furthermore, when air conditioning drives demand the peak demand is during the middle of the day, but the peak demand will shift to the evening/night. In some locations this wont matter a great deal, but in desert climates where extensive solar power is used to cover daytime demand there may not be adequate supply for night time heating. Also in sunny climates solar water heating is used extensively, with the sun blocked these units will fallback to electricity.
  • In cold climates the impact is also likely to be severe. In cold climates buildings will be better insulated and rely less on electrical heating, instead using heat pumps, gas, oil or wood. Electricity demand will still be increased however, as temperatures plummet far below the normal minimums. In locations where it is already difficult to supply peak winter demand, it will become impossible to satisfy demand, resulting in brownouts or blackouts. With disruptions to the grid caused by storms it will be a good time to have home heating which does not depend on electricity. Fortunately, more people in cold climates will have such heating options, but those who rely exclusively on electricity might be badly affected.
  • $\begingroup$ Upvote for the supply breakdown and focus on cold climates - I assumed blackouts/brownouts would be the next logical step from Michael Kjörling's answer. Good to see that others agree. $\endgroup$
    – KaguraRap
    Nov 12, 2014 at 14:59
  • $\begingroup$ If this situation persists, everywhere will be a cold climate. $\endgroup$
    – Oldcat
    Nov 13, 2014 at 17:29
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    $\begingroup$ @Oldcat remember that oceans have tremendous thermal mass, it would take many years for tropical oceans to cool down enough for tropical coastal regions to start to freeze. In already cold places there will be feedback as ice and snow reflect sunlight, prolonging the freeze even after most the dust has settled. $\endgroup$ Nov 13, 2014 at 20:29

The only electricity it affects directly is solar power generation because it takes sunlight and converts it to electricity.

Now there are plenty of secondary affects that could cause issues with electricity generation and distribution. Difficult to burn coal, or get coal to the power plants, same with oil etc. Power lines might fail or start sparking and grounding with all the 'stuff' in the air.

But if the power plants (coal, nuclear) can run and the transmission lines are still operational then it would not affect electric power.

  • $\begingroup$ Apart from damaged infrastructure, why should it be difficult to burn coal? $\endgroup$ Nov 11, 2014 at 20:21
  • $\begingroup$ @JanDvorak Only if there is so much crap in the air it affects combustion, either smothering it or a flash burn like coal dust going up in flame and exploding. Both unlikely $\endgroup$
    – bowlturner
    Nov 11, 2014 at 20:24

"We don't know who struck first, us or them, but we know that it was us that scorched the sky."

-- Morpheus, The Matrix

Electric power generation works by converting other forms of energy into electric power. Depending on how long sunlight is blocked, many of these other forms of input energy will likely run out.

  • Reduce insolation for minutes, and photovoltaic and solar thermal plants produce no useful power.
  • Reduce insolation for weeks, and weather patterns change, interfering with wind and hydroelectric power.
  • Reduce insolation for months, and you block plant growth, interrupting the supply of corn for ethanol and soy and algae for biodiesel. At this scale, you start to get human starvation too, as the supply of food is likewise interrupted. Without humans to monitor generators, they start to fail within a week to six years, as illustrated in the speculative TV series Life After People. (See Life After People Wikia for more info.)
  • Reduce insolation for thousands of years, and you block plant growth enough that decaying plants and algae cannot renew fossil fuels. Coal is essentially compressed peat, and petroleum and natural gas are algae that have been buried and pressure-cooked in anoxic conditions.
  • In theory, tidal and nuclear power would be less affected, so long as humans remain around to staff the generators.

Well, it might. But only a little, for now.

As others have pointed out, we only get a small portion of our energy from solar power. However, the Sun is indirectly related to other methods of producing electricity:

  • Wind power: The Sun heats air, which can produce currents that cause wind. We can capture some of this energy using wind turbines.
  • Hydropower: The Sun also heats water, causing some to evaporate. It's responsible for the water cycle. Without the water cycle, places filled with water that aren't filled by water from springs won't receive as much water. This can be troublesome for rivers, which means that hydropower will be less effective.

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