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37 votes
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Why does it take so long to restart a nuclear power plant?

When a reactor is shut down the core produces much less heat, but they do still produce heat through a mechanism known as decay heat. The fact that the core is producing less heat means that the ...
Chuck's user avatar
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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 ...
NMech's user avatar
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20 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 ...
LShaver's user avatar
  • 449
13 votes

Why does it take so long to restart a nuclear power plant?

Xenon is a result of the nuclear reaction and a neutron poison. If you don't wait for the xenon to decay, it eats up too many neutrons and you can't go critical. They always say "there are not ...
user1683793's user avatar
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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 ...
Solar Mike's user avatar
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7 votes

Why does it take so long to restart a nuclear power plant?

The answer really boils down to two factors: safety and testing. I'm going to give a generic summary of these two things below, but the real answer is quite complicated. The crux of nuclear plant ...
grfrazee's user avatar
  • 3,587
7 votes

How much power does it take to supply a laser which delivers 100 watts?

The total electrical to optical power efficiency of a laser system is sometimes termed wall-plug efficiency. It is the ratio of $$\eta = \frac{\text{optical output power}}{\text{consumed electrical ...
NMech's user avatar
  • 24.3k
7 votes

Alcohol as a working fluid?

Yes - for certain applications. Low-energy, low-temperature, small installations, possibly 'accessory' power where providing a bit of weak rotary power to some point of machinery would be difficult ...
SF.'s user avatar
  • 6,105
6 votes
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What is the difference between shaft power and brake power?

The short answer is these terms are defined by standards organizations based on specific test methods. These methods specify the engine condition, environmental factors, fuel chemistry, inlet and ...
Phil Sweet's user avatar
  • 4,755
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 ...
manassehkatz-Moving 2 Codidact's user avatar
6 votes
Accepted

Why do kWh (smart) meters have a maximum operating altitude?

Electronic components are rated for altitude because: Air density affects convective cooling, both forced and natural, meaning the cooling is reduced at altitude. Air density affects air's dielectric ...
Tiger Guy's user avatar
  • 6,871
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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4 votes

What is the difference between Bluetooth Low Energy and Bluetooth BR/EDR in Park mode?

There are many factors that make BLE low power, and I have attempted to address as many of them as possible. In order to better understand the power consumption differences between Bluetooth classic ...
Mahendra Gunawardena's user avatar
4 votes

Why is electricity used for powering our device?

Electricity is a convenient way to generate power centrally and distribute it to where it is needed according to demand. Central power generation by technologies like steam and gas turbines means that ...
Chris Johns's user avatar
  • 15.2k
4 votes

substituting power supplies safe?

If you get lucky, the power supply will either shut down because it is overloaded, or deliver a very reduced voltage. Either way, the keyboard won't work properly, or won't work at all. If you get ...
alephzero's user avatar
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4 votes

How to calculate hydropower in kW without water head

If you have horizontal water flow (no head) you are extracting its kinetic energy (from its velocity) not its potential energy (from its head). So you need to know the velocity of that flow as well ...
user_1818839's user avatar
  • 1,620
4 votes
Accepted

Intuitive explanation for why doubling max speed is proportional to eightfold power

Think of it as the volume of water you're displacing per second - the area multiplied by the distance moved. So intuitive I hope I can get away without an equation, but there's some good stuff in the ...
ItWasLikeThatWhenIGotHere's user avatar
4 votes

Intuitive explanation for why doubling max speed is proportional to eightfold power

It's a pretty rough approximation, and only holds where skin friction is the dominant source of drag throughout the speed range considered. Skin friction increases about as speed ^2. So for double ...
Phil Sweet's user avatar
  • 4,755
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,...
Bart's user avatar
  • 1,184
4 votes
Accepted

Power systems unclear voltages

Note the problem specifies the load is "delta connected". There is no neutral connection to measure phase voltage ($V_{LN}$) against. Also note the supply frequency is 60 Hz. 208 V is a ...
Graham Nye's user avatar
4 votes
Accepted

Torque Problems vs Motor Problem?

The motors have a rated speed of 2750rpm. It doesn't look like there's much of a gear ratio, so at the moment the motors spin at the same speed as the wheels. With 16" wheels, 2750rpm is about ...
sqek's user avatar
  • 156
3 votes

Planned power outage and backup generator

Electronics can be quite sensitive to the quality of the power supply, particularly in terms of providing a stable voltage and the right sort of AC waveform. There are two obvious solutions for ...
Chris Johns's user avatar
  • 15.2k
3 votes
Accepted

Relationship between output mechanical power and max pressure for a pump?

Generally speaking, for fluid systems the mechanical power can be computed as the product of pressure and volumetric flow rate: $\dot{E} = P\dot{V}$ where $\dot{E}$ is the power, $P$ is the pressure ...
BarbalatsDilemma's user avatar
3 votes

What happens if current provided to mono phase motor is less than rated power

Torque is proportional to current. If you can't supply the full current, then the torque will be lower than it would be otherwise. The highest current draw is at startup when the motor is not ...
Olin Lathrop's user avatar
  • 11.4k
3 votes
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Are there any methods to work out what appliances are running in my home from an aggregate power consumption sampled 6 times a minute?

The word that will unlock your searching is disaggregation - there's quite a lot of research going on right now into energy disaggregation. These generally involve some kind of learning algorithm, ...
410 gone's user avatar
  • 3,751
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
Accepted

How to calculate the power/torque/force needed to move a 4 wheeled vehicle?

The force required $F_{\text{r}}$ for driving a wheeled vehicle with mass $m$ is given the following formula (I will neglect slip): $$F_{\text{r}}=F_{\text{tire}}+F_{\text{aero}}+F_{\text{acc.}}+F_{\...
MrYouMath's user avatar
  • 1,036
3 votes

What is the difference between shaft power and brake power?

You mean BRAKE horsepower. It is the same as shaft horsepower. It is called brake horsepower (abbreviated BHP) because it is measured at the output shaft of the engine while it is running on a test ...
niels nielsen's user avatar
3 votes

What's the history of the 345 kV voltage level in power transmission?

With the high voltage AC power lines, there are trade offs between losses due to resistance in the wires, where the higher voltages are better and losses due to capacitance to the air, etc. where ...
user1683793's user avatar
  • 1,000

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