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ScienceNostalgia101

Alternative power sources megathread?

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number of my past posts relate to hypothetical alternative sources of electrical power. I'm wondering if it'd be more efficient (pun intended) to coalesce them all into one megathread, such that people could compare and contrast these hypothetical proposals. I'd like to reiterate all these proposals, and a few new ones:

 

A. One common criticism of household solar panel rooftops is that they're vulnerable to hail damage. I'm not sure if there's some way to mitigate this vulnerability that the fossil fuel industry doesn't want us to know or whatever, but in the meantime, since thermal solar isn't as vulnerable to hail damage, would a better approach be to have some rooftop concave mirror and/or rooftop convex/fresnel lens, to boil water? (This might also be more efficient twofold in having a direct source of heat, instead of having to convert heat into electricity and then electricity into heat.) If fire safety's the issue, would it be worthwhile to have the water supply BE the convex lens; namely, a watertight (apart from some outlet/intake tubes at the top) roof filled with water, such that the point of convergence is some dark surface within this roof that happens to be surrounded by water?

 

B: So lightning is a form of direct current, is it not? If so, does that mean that some device designed to attract lightning, and run it through some electrolysis device, would be able to convert its electrical energy into chemical energy?

Edited by ScienceNostalgia101

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8 hours ago, ScienceNostalgia101 said:

 A. One common criticism of household solar panel rooftops is that they're vulnerable to hail damage. I'm not sure if there's some way to mitigate this vulnerability that the fossil fuel industry doesn't want us to know or whatever, but in the meantime, since thermal solar isn't as vulnerable to hail damage, would a better approach be to have some rooftop concave mirror and/or rooftop convex/fresnel lens, to boil water? (This might also be more efficient twofold in having a direct source of heat, instead of having to convert heat into electricity and then electricity into heat.) If fire safety's the issue, would it be worthwhile to have the water supply BE the convex lens; namely, a watertight (apart from some outlet/intake tubes at the top) roof filled with water, such that the point of convergence is some dark surface within this roof that happens to be surrounded by water?

Thermal benefits from scaling (bigger is better) — you need a certain number of mirrors to efficiently heat your material, and then you need a way to produce electricity, which also benefits from scaling. This is why it's done at the utility scale, not the home scale.

Having direct heat is only useful when it's cold. So only a few months of the year in some places.

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Most solar panels are made to cope with some hail - ours have survived numerous storms with hail, occasionally large enough to damage vehicles. Very large hail can still damage them - but we need to put that in perspective; very large hail damages all manner of things and replacing a few solar panels is not so common or such a big deal as to require a rethink of how solar power is done.

My understanding is that solar installers did a lot of removal of panels after serious hailstorms in Brisbane Australia in order that roofers could fix damaged roofs - only to put the same panels back. Very few were damaged.

Interesting to note that heat pump hot water systems are now similar in cost to passive solar hot water systems, have very low power usage and are reliable. Homes with solar electricity would probably not need extra solar power if they are used; our home already sends several times more power back to the grid than we consume and hot water systems are well suited to scheduled operation during the middle of each day or whenever solar electricity supply is exceeding usage.

Edited by Ken Fabian

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Posted (edited)
On 12/30/2019 at 8:36 AM, swansont said:

Thermal benefits from scaling (bigger is better) — you need a certain number of mirrors to efficiently heat your material, and then you need a way to produce electricity, which also benefits from scaling. This is why it's done at the utility scale, not the home scale.

Having direct heat is only useful when it's cold. So only a few months of the year in some places.

What about enough heat to boil water for cooking food? That's useful even when it's warm. Also, if every household had a concave mirror for a rooftop, more sunlight would be absorbed by the boilers and less would be absorbed by anything else. Wouldn't that reduce the urban heat island effect? Could it also reduce the city's albedo to below what that of the pre-existing natural environment would have been?

 

As for hail being not a big deal to solar panel rooftops, how come it's such a popular anti-solar talking point? Engineering angle aside, would replacing solar panels with concave mirrors do more good to the pro-solar movement or more harm from a PR standpoint?

 

EDIT: And in light of Australia's wildfires, should I bump the "harnessing the energy of forest fires" thread or continue that discussion here?

Edited by ScienceNostalgia101

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2 hours ago, ScienceNostalgia101 said:

What about enough heat to boil water for cooking food? That's useful even when it's warm.

How much water do you use each day for cooking?

 

Quote

Also, if every household had a concave mirror for a rooftop, more sunlight would be absorbed by the boilers and less would be absorbed by anything else. Wouldn't that reduce the urban heat island effect? Could it also reduce the city's albedo to below what that of the pre-existing natural environment would have been?

The energy is being absorbed here on the planet, so I don’t see how the heat island effect would be reduced. To reduce albedo the light has to be reflected out to space. Solar thermal would tend to increase absorption.

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Posted (edited)
28 minutes ago, swansont said:

How much water do you use each day for cooking?

 

The energy is being absorbed here on the planet, so I don’t see how the heat island effect would be reduced. To reduce albedo the light has to be reflected out to space. Solar thermal would tend to increase absorption.

Hmm... what about the fact that some of the thermal energy that would otherwise go toward increasing surface temperature instead goes toward boiling water? Would that decrease temperature while simultaneously increasing humidity? (Assuming some of the water vapour above each pot of food/coffee escaped into outdoor air before condensing?)

 

As for me, I don't cook. I work in places that have food available and/or eat canned fish/frozen dinners/peanut butter sandwiches for protein. Perhaps not the healthiest approach, but it's what I'm used to.

Edited by ScienceNostalgia101

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Posted (edited)

How about different approach: instead of searching for a way to increase power production, search for a way to reduce current power usage?

Households in hotter regions of the Earth significant amount of electrical energy use on air conditioning and refrigeration of food.

Households in the colder regions of the Earth use significant amounts of energy to heat homes during the winter.

 

Decrease of power usage for TV and computers has been already done by migration to LCD/LED/OLED and to laptops (from power consuming CRT and plasma).

So, limit energy used for air conditioning and refrigeration, and you will get the same effect as increased power production, with increased demand for power.

 

See an example of some e-books smart displays. Instead of using power for continuous sustaining display, energy is used only for switching different pixels between one page and another page.

https://en.wikipedia.org/wiki/Electronic_paper

 

Personally, I am for turning streets to one large solar panels new generation with built-in electromagnets. They could produce energy and immediately transport it to vehicles flying slightly above them due to magnetic repulsion between streets and vehicles. Mass of cars would be minimal without full size tank nor full size accumulators. Without friction with road, energy spend on acceleration would be much smaller than now. To decelerate/brake there could be used KERS or similar system converting kinetic energy to electrical energy.

 

Edited by Sensei

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45 minutes ago, ScienceNostalgia101 said:

Hmm... what about the fact that some of the thermal energy that would otherwise go toward increasing surface temperature instead goes toward boiling water? Would that decrease temperature while simultaneously increasing humidity? (Assuming some of the water vapour above each pot of food/coffee escaped into outdoor air before condensing?)

Why would it? The thermal energy is still around.

 

 

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I mean the latent heat of vaporization; as in, yes, it's still around, but more of it as potential energy and less as kinetic?

15 minutes ago, Sensei said:

How about different approach: instead of searching for a way to increase power production, search for a way to reduce current power usage?

Households in hotter regions of the Earth significant amount of electrical energy use on air conditioning and refrigeration of food.

Households in the colder regions of the Earth use significant amounts of energy to heat homes during the winter.

 

Decrease of power usage for TV and computers has been already done by migration to LCD/LED/OLED and to laptops (from power consuming CRT and plasma).

So, limit energy used for air conditioning and refrigeration, and you will get the same effect as increased power production, with increased demand for power.

 

See an example of some e-books smart displays. Instead of using power for continuous sustaining display, energy is used only for switching different pixels between one page and another page.

https://en.wikipedia.org/wiki/Electronic_paper

 

Personally, I am for turning streets to one large solar panels new generation with built-in electromagnets. They could produce energy and immediately transport it to vehicles flying slightly above them due to magnetic repulsion between streets and vehicles. Mass of cars would be minimal without full size tank nor full size accumulators. Without friction with road, energy spend on acceleration would be much smaller than now. To decelerate/brake there could be used KERS or similar system converting kinetic energy to electrical energy.

 

Sounds good, but sounds like it'd take a while to make such drastic changes to infrastructure, whereas climate change needs to be dealt with more urgently. Maybe something to think of after the climate crisis is resolved?

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41 minutes ago, ScienceNostalgia101 said:

I mean the latent heat of vaporization; as in, yes, it's still around, but more of it as potential energy and less as kinetic?

 You’re assuming the vapor never condenses. Is that resonable?

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Not quite, just that all that excess water vapour pumped into the air would shift the equilibrium somewhat, sort of like how a weight hanging from a spring shifts its equilibrium.

 

Still an unreasonable assumption?

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9 hours ago, ScienceNostalgia101 said:

Not quite, just that all that excess water vapour pumped into the air would shift the equilibrium somewhat, sort of like how a weight hanging from a spring shifts its equilibrium.

 

Still an unreasonable assumption?

Once the air condenses, it releases the energy. If you shift the equilibrium, you are only storing the energy of that amount of water. Plus, you've made the atmosphere more efficient at trapping heat. It's a feedback term.

Can you estimate how much energy would be stored for a 1% shift in humidity? I'll bet it's not a lot, comparatively.

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Depends on the temperature, I think. At higher temperatures a 1% shift in humidity counts for more than that of lower temperatures.

 

In any case, thanks for the clarification.

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On 1/4/2020 at 5:01 PM, Sensei said:

How about different approach: instead of searching for a way to increase power production, search for a way to reduce current power usage?

I forgot to reply to this earlier. I'd like to take this opportunity to ask; should this be the same thread or a separate one?

 

Because I can think of some things that blur the distinction between "increasing power production" and "reducing current power usage."

 

For instance, suppose that instead of throwing paper waste away, one were to burn it for heat. There are two ways I can think of for this heat to be used:

 

A) Put a metal tube above the fire that does not allow smoke to enter, but allows the heat energy to conduct through, so that enclosed air molecules can warm up from contact with this surface and enter any household to which this tube is connected, or...

 

B) Just directly boil water above it and use it to cook food or brew coffee.

 

Would either of these be more efficient; or less; than transporting everyone's paper waste to an incinerator that uses higher temperatures to generate electricity? (Efficiency of an engine; if I recall correctly, is a strictly monotonic function of difference in temperature between the hot reservoir and cold reservoir, correct?)

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Can't edit prior post. Have a new energy-saver inquiry.

 

Is it more energy-efficient, in the wintertime, to have an outdoor refrigerator/freezer, such that the temperature difference between the outdoor air and refrigerator/freezer is less than that between the indoor air and refrigerator/freezer, or less efficient because an indoor refrigerator/freezer releases heat into its surroundings anyway?

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4 hours ago, ScienceNostalgia101 said:

Is it more energy-efficient, in the wintertime, to have an outdoor refrigerator/freezer, such that the temperature difference between the outdoor air and refrigerator/freezer is less than that between the indoor air and refrigerator/freezer, or less efficient because an indoor refrigerator/freezer releases heat into its surroundings anyway?

I am using my balcony as refrigerator during true winter (hard to get one these days).. After shopping e.g. beers and meat land on my balcony (there is -5 C at the moment).

Before refrigerator has been created people used ice houses

https://en.m.wikipedia.org/wiki/Ice_house_(building)

which costed nothing to operate except a while of work to gather ice.

ps. Typical house electronic and electric devices are not designed to operate in cold and/or humid environment..

Edited by Sensei

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