Questions tagged [renewable-energy]

Energy sources that do not rely on the consumption of an exhaustible fuel. Tidal, geothermal, and the direct and indirect solar energies (direct: photovoltaics, CSP, solar thermal; indirect: wind, wave, biomass) are renewable energy.

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1 answer
34 views

Ground source cooling -- why do you need the heat pump? [closed]

This answer says that the water from a ground source is always 50F. (I think this varies by location, but the concept is valid, anyway.) Why do we even need a heat pump? Why not just run that cold ...
13 votes
4 answers
3k views

Why is the ground warm during winter and vice-versa?

I was just looking at the geothermal house heating in Iceland, and came to know that in the winter the water is warm, hence cools the house, but how is it hot, not about us feeling it.. My question is ...
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Is it possible to boost solar panel output using wavelength shifting materials?

Solar panels only produce energy from a small section of the total wavelength spectrum of light. I believe some panels have a mirrored back to pass light through the solar panel a second time. Much of ...
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1 answer
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If water vapour is a green house gas , then how is using hydrogen fuel cell stopping global warming?

Hydrogen fuel cells produce water vapour then aren't they also contributing towards global warming ?
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High altitude Concentrated Solar Power (CSP)

Are there any advantages in terms of energy output and efficiency in installing a high altitude concentrated solar power facility? Hypothetically speaking, what if we could build a facility similar to ...
2 votes
2 answers
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Energy lost to hydrogen fuel cell

So I have a question about an experiment we did in class. We used a fan to blow air at a little wind turbine to generate electricity, we connected the turbine to a reversible PEM fuel cell to ...
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1 answer
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Can you use the water flow exiting a hydroelectric generator to generate more energy?

In videos of hydroelectric generators I often see that the water that exits a turbine is still moving with significant velocity. Example of a turbine that has exit water flow with significant velocity:...
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1 answer
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Is Gravity Storage a pipe dream? [closed]

Background Energy Vault has a new Gravity Storage system its spruiking (Link here). They are getting a lot of attention and funding. However I am skeptical on the technology and I don't understand why ...
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1 answer
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How does the combination of freeze distillation and osmotic power respect the conservation of energy?

So imagine the following system. You're in a cold part of the world. Sea water isn't isn't frozen over due to the ocean moderating temperature, but smaller lakes definitely have by now. Sea water ...
1 vote
1 answer
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Unusual temperature shape in gravel heat storage

I’m currently doing undergrad research on using a gravel (basalt 2-5mm grain size) bed as an heat storage. In order to heat up the gravel inside, hot (~100°C) and dry (RF<4%) air with a pressure of ...
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Tesla patented a device he believes gathered energy from light. (US 685,957 - Apparatus for the Utilization of Radiant Energy): [duplicate]

The invention is a sheet metal (top) place high above the ground. The sheet of metal is connected to a capacitor (the ⊔⊓ shapes) connected to the Earth. (The other stuff on the right of the image is a ...
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1 answer
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Creating a Bouyancy Force Generator

How much energy is needed to maintain boiling water? (I'm assuming $1400~\rm W$). With that said, when air is added to an object to decrease its density, does the strength of its buoyant force ...
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1 answer
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Why does pumped hydro require reservoirs for efficient energy storage?

The problems with using pumped hydro as a long term battery are: Hard to find locations physically suited for an extreme height gradient for two massive reservoirs (main issue). Water evaporates, so ...
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4 votes
2 answers
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To grow one $\rm m^2$ of crop plants, how many $\rm m^2$ of solar panels do you need?

In vertical farms you need to use LEDs to make plants grow, which in turn have to be powered e.g. by solar panels. If solar panels had the same efficiency as plants, then you would need the same ...
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Producing Pressurized Hydrogen Underwater Then Using it To Do Work

This is a bit of a weird one but I didn't know where else to ask this. I was recently talking to my brother and he told me about an idea he had talked with his boss about how to create compressed ...
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12 votes
11 answers
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Does the second law of thermodynamics imply that renewable energy also leads to global warming/climate change?

So I have this (possibly dumb) question about the implications of the second law of thermodynamics to the use of renewable energy for the world, so please bear with me. Here goes: Apart from the ...
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Wind turbines or tidal power stations incorporating elements of origami or reconfigurable materials: is innovation possible from physics?

If I refer well (I'm not a physicist) one of the oldest uses/applications of renewable energy is to try to exploit the wind and tides by means of designs of machines: windmills and water wheels. Today ...
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Can a positive ion generator ionizing water create electricity with a net gain of electricity?

Traditional ion generators work by sending electricity through air to ionize air with a negative charge. This is said to benefit human health. But, it should be possible to extract ions from atoms and ...
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Why is the Weibull distribution used to describe wind speeds?

Frequently, it is stated that the distribution of wind speed at a certain location can be described by the so-called Weibull distribution: $$ W(x;\lambda,k):=\frac{k}{\lambda}\left(\frac{x}{\lambda}\...
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1 answer
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What is and how do you calculate design wind speed, on wind turbines?

I am finding hard to get a consense on the definition of design wind speed, on eolic turbine matter. I thought it was he velocity that correspondes to the maximum power output, but I have already ...
3 votes
3 answers
574 views

Why aren't gravity batteries everywhere? [closed]

The problem of energy storage, especially with regard to renewables, remains unsolved. Or at least there do not seem to be any popular solutions. Why not gravity batteries? I love the idea, and ...
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1 answer
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Why/when is an indirect AC - DC - AC frequency converter superior to a direct AC-AC frequency converter? [closed]

I am currently studying wind power and the power electronics used for it. In wind power a generator is driven by wind, thus the resulting power is of widely varying frequency and amplitude. The power ...
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2 answers
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Water tower power generation

I understand that one of the concerns with generating power from a water tower, allowing the falling water to turn a generator, is that if the water wasn't coming from a natural source, thus having to ...
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1 vote
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Power grid stability in an only inverter grid

I think i there is little misconception in my head regarding the cause and effect of changing grid frequency and therefore I am confused about the transition from fossil fuels to regeneragtive energy ...
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Textbook recommendation renewable energy

I am supposed to teach a lecture on the broad field of renewable energy for the first time. I wanted to check how other people cover the field, but there is a plethora of books on the subject and even ...
1 vote
2 answers
237 views

Why can't a low solidity wind turbine be used in high torque applications through gearing? [closed]

From my understanding, low solidity wind turbines (such as the three blade type) are more efficient due to a higher tip speed ratio, giving a higher coefficient of performance. However, they are not ...
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38 votes
4 answers
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Why are solar panels kept tilted?

I have noticed that, in my country India, most of the solar panels are tilted southward at an angle of ${45}^{\circ} .$ Even on buildings with inverted V-shaped roofs, solar panels are still oriented ...
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17 votes
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Theoretical physics for better batteries?

It is Earth day, so I started thinking about the theoretical physics problems that could help reduce greenhouse-gas emissions and fight climate change. We actually have a reasonable range of ways to ...
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2 answers
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Can we use the power of ice to float to make free electricity?

ice and water have a volume to weight ratio of 12/11 so 11 tons of ice will support 1 ton of weight 1 ton of ice takes 1000 watts or 12000 b.t.u. of energy to be produced question is, at what depth ...
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Where does the energy from tidal power plants come from? [duplicate]

Tidal power plants taps into the energy in the motion of the oceans due to the gravitational interaction between the earth and the moon, so much is clear to me. This question is about where would this ...
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1 answer
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Can Bhaskara's Wheel increase the efficiency of wind mills?

Bhaskara's wheel is an ancient attempt at perpetual motion. The idea is that gravity will pull the water toward the center for the bottles at the top and toward the ends for the bottles falling to ...
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1 answer
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Potential effect of another "year without a summer" on solar-powered society? [closed]

In the "year without a summer", a volcanic eruptions caused enough sunlight to be blocked for average global temperatures to drop by 0.4–0.7 °C. What would be the effect of this sort of event on a ...
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1 answer
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how could more rotor speed mean less energy in wind turbine?

there's a question that has been annoying me for a while ,consider the follwoing (power,rotor speed) diagram for different wind speeds at some wind speed(6m/s for example)how could a turbine running ...
14 votes
6 answers
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Is nuclear power desireable in the long term, given the fact that it's an unnatural heat input to our planet? [closed]

I've been reflecting on whether we want nuclear at all in the long term (compared to renewables like wind, solar, and hydro). There's a certain amount of heat (energy) entering our planet and leaving ...
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1 answer
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On what planet within the Asteroid Belt would solar panels work the best?

I was researching for a project and came across this question. Maybe this is a bit too broad? How might solar energy work on Mars? Would it be sufficient to sustain a colony?
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2 votes
1 answer
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Hydrogen as energy storage

How viable is hydrogen as an energy storage medium? It would be extremely easy to split water into hydrogen and oxygen . It also has high energy content so relatively a large amount of energy can be ...
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1 answer
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Is there common ground between wind and solar technologies/methods for harnessing energy? And how does this compare to nonrenewable methods?

To clarify: not asking similarities between solar and wind energy as a whole but only its technologies/methods of harnessing energy [example: ?turbine blades? in solar towers and wind turbines] Is ...
2 votes
1 answer
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Can solar panels cool the atmosphere? [duplicate]

I am just curious if solar panels, because they absorb radiation, cool the atmosphere. If there were enough of them, would the temperature be different? I'm not a physicist or student.
3 votes
1 answer
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Effect of wind power on the global climate by decreasing kinetic energy of air

Assume the hypothetical situation that all global energy is produced by wind power and instead of fossil fuel power etc. Since every wind turbine decreases the kinetic energy of the air a bit, I am ...
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1 answer
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Could it be practical to harvest energy from sinking objects into deep water? [closed]

I'm imagining a canister for storing compressed gas connected to a fully inflated balloon. This is sea-level. The valve is open so air can move freely between the bag and the tank. Some heavy objects,...
2 votes
0 answers
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Why are spin coated polymer solar cells more efficient?

Reading papers on polymer solar cells (PSC from now on), it is seen that many different coating techniques are used in order to coat polymer films on substrates. It is also seen that spin coated ...
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4 votes
1 answer
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Can water differential be used to store renewable energy?

Excuse me if the question is poorly worded or there already is a similar question, I searched but as a physics layman I do not know the proper terminology. I was watching a Nova story just now and ...
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1 answer
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Losses occurring in solar cells [closed]

If a solar cell is subjected to a light of intensity $1000$ $\text{W/m^2}$, the output at the cell is much less than ideal case scenario. What are all the factors causing energy losses in a solar cell?...
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1 answer
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Why is Alternative energy most commonly stored in metal acid batteries? [closed]

Why is alternative energy most commonly stored in relatively expensive metal acid batteries, which have a short life, rather than hydrogen gas accumulated through electrolysis? Hydrogen is a ...
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3 answers
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Can aurorae/northern lights be used as an energy source?

Their temperature is high, they have high velocity. Can they be used as an source of energy? If not why? If yes how?
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2 answers
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How do solar panels and wind turbines prove the law of conservation of energy?

The law of conservation of energy makes sense to me in certain systems but in others I can't seem to comprehend it. For example, a car moves because the stored chemical energy within its fuel is ...
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1 vote
3 answers
435 views

Water turbine power generation for large and small turbines

If you have a small water turbine and a larger water turbine in a river, would the larger turbine produce more power or would they produce the same because of the equal speed of the river?
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Changing number of wind turbine blades

I have read (and to some degree understood) that if one were to increase the number of blades for a wind turbine, it would be reasonable to reduce its rotational speed. In my mind I'd associate this ...
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Solar power with parabolic mirrors/lenses + peltier elements?

Peltier elements are used to use electricity create temperature gradients for example for the purpose of cooling electronics (and then in a secondary step remove the heat from the hot side). However ...
-6 votes
1 answer
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I think I may have found a renewable energy source [closed]

Hello guys so I have this idea of mine which I can't get my head around and I need someone to tell me why it won't work, so let's say you have a fully pressurised tank of air and you blow that ...