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29 votes
Accepted

Why is hydro-electric power still scarce in some places?

Because most of the water is at the lowest point is can be, the ocean. Second issue is that you need quite a bit of vertical drop for water power to be a viable power source. There are DIY hydro ...
ratchet freak's user avatar
11 votes

Wind farms that wind up in the wind, and then unwind producing energy when the wind is still

The storage part of the RES systems is probably the biggest challenge today. There are several ways to store energy. By far the most used way today is Pumped storage hydroelecticity systems. ...
NMech's user avatar
  • 24.4k
10 votes

Why is hydro-electric power still scarce in some places?

There are two issues, harnessing and market. You need both to be viable. A market, makes most of the 70% of the land mass covered by water unusable, because even if you could harness the power, it ...
StainlessSteelRat's user avatar
8 votes

Why is hydro-electric power still scarce in some places?

Rivers in a flat landscape are often unsuitable because you need a height difference to make the turbine work. Let's say a 1 meter height difference is required. There are many areas where the river's ...
Hobbes's user avatar
  • 746
7 votes

Are abandoned nuclear smoke stacks strong enough to be filled with water (for pumped storage)?

Those aren't "smoke" stacks but cooling towers designed to let hot air rise and expand optimally. These things are typically 200 m high. Static pressure of 200 m of water is pretty high. They were ...
ratchet freak's user avatar
6 votes

Why aren't gravity batteries everywhere?

So, this battery costs US$70, weighs 406 grams, and holds around 200,000 Joules of energy. To get the same energy from that weight as a "gravity battery" you'd have to pick it up over 49 kilometers ...
TimWescott's user avatar
  • 2,682
6 votes

Wind farms that wind up in the wind, and then unwind producing energy when the wind is still

You've described energy storage, or physical batteries. You wouldn't need half of each wind farm dedicated to this; you would simply store the excess, beyond what is used at a given time. It's not ...
RC_23's user avatar
  • 781
6 votes

Wind farms that wind up in the wind, and then unwind producing energy when the wind is still

I suppose what you had in mind with your question was something like, every single turbine winches up a heavy weight to its tower while surplus energy is available, then lowers it again to recuperate ...
leftaroundabout's user avatar
5 votes

Why aren't gravity batteries everywhere?

Consider 1 kWh = 1000 W * 3600 seconds = 3,600,000 J. 1 kg lifted 1 m = ~10J. Let's use 1 metric tonne. 1000Kg. So we get 10,000 J per meter of elevation. 3,600,000 / 10,000 = 360 meters. Around ...
Sherwood Botsford's user avatar
5 votes

Generating power from fruit

You seem to be asking about using fruit juice as the electrolyte of a battery. Yes, that's possible, but you don't get a lot of power that way. The power also doesn't just come from the fruit juice. ...
Olin Lathrop's user avatar
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5 votes
Accepted

What is the theoretical maximum energy efficiency of hydro turbines?

Something can only be 100% efficient when a lot of generous assumptions are taken into account. If you assume: No friction (turbine surface, turbulence, nozzle, or bearings) Perfect cup design (100%...
ericnutsch's user avatar
  • 8,181
5 votes

Wind turbines with down tower power units. Why aren't they more common?

The math doesn't make any engineering sense. A 5MW turbine typically rotates at about 10 RPM, near enough 1 radian per second. Assuming you had reasonably big sprockets on the chain drive, say 2 ...
alephzero's user avatar
  • 12.5k
5 votes

Wind farms that wind up in the wind, and then unwind producing energy when the wind is still

You're describing a Gravity Battery. While the other answers have pointed out that water is the most common lifted weight, EnergyVault is a Swiss company that's basically lifting concrete blocks. The ...
user121330's user avatar
4 votes

Clutch role in a micro hydropower

The clutch provides an instant disconnect either for scheduled maintenance or in an emergency. If the water flow is stopped instantly, then the energy of that moving pipeful of water has to be ...
Solar Mike's user avatar
  • 15.9k
4 votes

Why don't hydroelectric plants use cascades of turbines instead of single turbines?

The reason why a hydroelectric generator is fundamentally different to a gas turbine is because water under pressure is not a gas, and does not change size significantly as energy is extracted from it....
Da bishop's user avatar
4 votes

Why is hydro-electric power still scarce in some places?

In years past I would have been a fan of hydroelectric power but I have read1 about some of the downsides over the years. These include: Major ecological problems including blocking fish migration. ...
Transistor's user avatar
  • 10.9k
4 votes

Advantages of hydrogen gas turbine over fuel cell

I've read in one of Smil's books that fuel cells are somehow limited (in what sense I'm not sure anymore but I believe it was power output) by their "active area". I'm having difficulties learning ...
baltakatei's user avatar
4 votes

Can lithium ion batteries solve the world's energy storage problem?

I would like to answer this question slightly differently. The challenge with rechargeable batteries (Lithium Ion), each charge discharge cycle causes internal resistance of the battery to increase. ...
Mahendra Gunawardena's user avatar
4 votes

How do 3 blade turbines come so close to the Betz Limit?

The Betz limit is based on an extremely crude model for an actuator disk. If you want to compare the performance of the product of a billion dollar industrial development program, let's at least use a ...
Phil Sweet's user avatar
  • 4,765
4 votes

How large would a solar panel array need to be in order to supply all the world's energy?

The U.S. National Renewable Energy Lab did a study of solar installations in the U.S. in 2013 and determined that for large-scale solar PV systems, 7.9 acres (31,970 $m^2$) of land are required on ...
LShaver's user avatar
  • 449
4 votes

Can the crest of an ocean wave be increased by directing ocean waves to a center of a curved column?

Your idea has merit, and the fundamental principle involved is called impedance matching. Here is how it works: For any power source we wish to harness, that source can be characterized by two ...
niels nielsen's user avatar
4 votes

Wind farms that wind up in the wind, and then unwind producing energy when the wind is still

As other answers have pointed out, the key to a system that utilizes renewable energy sources with an energy storage backup envisioned by the question is the ability to store large amounts of energy ...
njuffa's user avatar
  • 141
3 votes
Accepted

What is the exact definition of renewable energy

overview: Renewable energy is one for which the input energy is renewed on human timescales. Remember, energy is always conserved. It doesn't come from nowhere. Pretty much all the energy we use on ...
410 gone's user avatar
  • 3,761
3 votes

Feedback on idea for a power station

For pretty fundamental physical reasons any power generator is only a way of converting one sort of energy to another ie converting the energy you have available to the sort of energy that you want. ...
Chris Johns's user avatar
  • 15.2k
3 votes

Why aren't gravity batteries everywhere?

Are there some shortcomings that I am missing here? Yes there are a couple of things you have missed. Firstly I will deviate slightly from your question but I believe this is relevant. The need for ...
Brad's user avatar
  • 318
3 votes

How is the energy production of solar and wind compared with the prospect of nuclear fusion?

The reality of generating electricity from nuclear fusion on an industrial scale is still a very long ways off. It is speculative high cost, high risk venture, with a potential high payoff far off ...
Brian Salvatore's user avatar
3 votes
Accepted

Does a fully mechanical heat pump make sense?

Virtually every possible way of doing this is already out there. For bolt-ons, you can find propshaft pto chain drives and belt drives, hydraulic and mechanical engine pto systems, and front of block ...
Phil Sweet's user avatar
  • 4,765
3 votes

Toyota teams up with Pepco for Vehicle to Grid technology

A battery electric vehicle is charged from the grid or other sources of electricity. For example, our house is grid-tied with our solar PV system and we charge two BEVs. It is not easily determined if ...
fred_dot_u's user avatar
  • 7,227
2 votes
Accepted

How is the energy production of solar and wind compared with the prospect of nuclear fusion?

Fusion is widely extolled by advocates as being safe (but is that collective opinion justified)? I would prefer to begin my discussion comparing fusion with renewable energy systems with an ...
Robert Steinhaus's user avatar
2 votes

Can you use the kinetic energy of air to power a car?

No, you can not create energy or a force from nothing. It would break the laws of thermodynamics. Specifically addressing your question in a simplified way; the large area on the front multiplied ...
ericnutsch's user avatar
  • 8,181

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