36
votes
Accepted
How does turning off electric appliances save energy
Electricity production optimization is a very complex subject. It is also affected by many parameters , which I will try to outline below.
TL;DR: Demand is constantly monitored and supply is ...
- 24.2k
26
votes
Why does "potential energy" have the word "potential" in it?
Because it has the potential to produce mechanical work.
- 24.2k
19
votes
How does turning off electric appliances save energy
Timescales on the grid
Power demand fluctations can be broken into timescales from micro-seconds to decades. On the "decades" end of the scale, the power industry and utility regulators work ...
- 439
19
votes
Accepted
Why does "potential energy" have the word "potential" in it?
potential (adj.)
Capable of being but not yet in existence; latent or undeveloped.
The block is stationary and therefore not performing work. If the block never moves, the potential energy remains ...
- 6,860
14
votes
Can the Sabatier reaction power a vehicle?
According to Wikipedia:
It [Sabatier reaction ] involves the reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures in the presence of a nickel ...
- 2,160
13
votes
Accepted
Calculating torque needed to climb a graded hill
I think you're overcomplicating things. To push 85 kg up a 15% slope against gravity of 9.8 m/s2 requires a force of
$$ \sin (\arctan (0.15) ) = 0.1483 \approx 0.15 $$
$$F = 85 kg \cdot 9.8 \frac{m}...
- 6,864
11
votes
Is the main goal for wind turbines to take maximum energy for a given diameter?
The function of the wind turbine is to extract as much as possible energy from the moving mass of air. The energy of a mass $m$ of air is
$$KE = \frac{1}{2}m v^2$$
and the power is (because the mass ...
- 24.2k
10
votes
How does turning off electric appliances save energy
Yes, they monitor demand and due to differences in how different power stations are controlled they can increase or reduce output to match demand.
Some power plants like nuclear run at full output as ...
- 15.3k
9
votes
Relationship between wind velocity, turbine rotor diameter, and power output
It's not a simple relationship.
First let's deal with the kinetic energy of the wind passing through the rotor.
The mass of air passing through it in one second, $m$, is equal to the the density of ...
- 3,741
7
votes
Magnetic Entrapped Storage at 0 gravity
Flywheels are used in space, but not for storage of energy. They are used for attitude adjustment, as the spinning of a large mass has significant implications in an object which is free to move.
...
- 170
7
votes
Accepted
Why can't energy be entirely recovered from a moving car's rotating wheels?
Get a small DC motor from a cheap toy or something and put a gear or a flywheel or something on the shaft to make it easy to spin with your fingers. You should find these in the toy as well.
Ask your ...
- 638
6
votes
Turning an engine over with engine compression
There is another reason for this in multi-cylinder engines. While one cylinder is compressing the air, another is decompressing it. The net result is that the torque as a function of position gets ...
- 11.4k
6
votes
How does turning off electric appliances save energy
Peak Demand
One of the biggest issues in the electricity business is managing peak demand. This is the maximum amount of electricity needed at any one time. Typically this will be the middle of the ...
6
votes
Why does "potential energy" have the word "potential" in it?
In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, attachments, electrical charge, magnetic field, mass, etc., and ...
- 61
5
votes
Working hours of power plant generators
Nuclear power plants are always working, except circa one month/year for maintenance. It's mainly because stopping the nuclear reaction and cooling the reactor down is a very long and difficult ...
- 169
5
votes
Why can't energy be entirely recovered from a moving car's rotating wheels?
There are some people who cannot be told. They think they know everything and that they are never wrong. My advice is do not try to convince your friend that your friend is wrong. You will always lose ...
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5
votes
Accepted
What does MM prefix mean in MMtoe?
TL;DR: the MM in MMtoe is probably related to the Latin Numeral M (for 1000). In that context MM means one thousand thousands (i.e. one million)
Although this is very confusing, the bottom line is ...
- 24.2k
5
votes
Accepted
What happens to generated electricity if it is not used?
TL;DR: a small portion of the excess energy is stored in the form of rotational kinetic energy, however, generator controls make it so these amounts are not significant.
electricity generation
(Al ...
- 24.2k
4
votes
How could we possibly harness the energy from the Earth's negative charge?
I think Failmond's first post does a solid job with the analysis.
You have a voltage potential across a resistor(the air). You can not remove air from the equation as it is what is sourcing and ...
- 7,794
4
votes
Accepted
Turning an engine over with engine compression
In theory, it should perform as you say. This is how prop starting an aircraft engine works.
An internal combustion engine, unlike your bike pump, is designed for high speed, high power, and high ...
- 7,794
4
votes
4 Way Bugatti Tug of War
The force on each car is purely longitudinal because the restraining force of necessity runs thru the central point (origin). For example, the East and West forces cancel so far as the origin is ...
- 4,189
4
votes
Could Internal Ionisation Engine be a description of electric cars?
It's a very poor analogy, especially in presence of ion engines used for space travel, where the propellant is ionized inside the engine, then accelerated outwards.
Besides, the electric cars are ...
- 6,125
4
votes
Specific energy vs Specific power in batteries
Batteries can't deliver unlimited current. Internal resistance, and limitations of the chemical reaction within the battery make that it can only deliver so much current. And the more current is drawn,...
- 1,174
4
votes
Why can't energy be entirely recovered from a moving car's rotating wheels?
If it worked he would not need the engine to maintain speed
Ask your friend:
If this is "perfect" — as you say — with no friction, no losses... then why do you need the engine to maintain ...
- 211
4
votes
How to convert Joules(kinetic energy) plot chart into watts?
To convert a plot of J versus s to a plot of J/s vs s, take the derivative.
Here is my quick-and-dirty answer after digitizing the data.
- 2,878
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 ...
- 15.3k
4
votes
Accepted
Question about flow temperature and storage temperature in a cogeneration plant
when the cogeneration plant switches of upon reaching 85°C flow and without another heat source, there's no way to reach 95°C.
Are you sure the switch-off happens at 85°C flow, and not at 75°C return ...
- 4,705
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 ...
- 4,322
4
votes
Why does "potential energy" have the word "potential" in it?
The block in itself has no energy. If you build a kettle of water around it, the water will not heat up. If you attach axles to it, the axles will not suddenly start spinning.
However, since we spent ...
- 141
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