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
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 ...
- 449
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 ...
- 15.9k
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 ...
- 24.2k
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 ...
- 6,115
6
votes
Accepted
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 ...
- 4,900
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
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 ...
- 7,023
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. ...
- 11.4k
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 ...
- 1,630
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 ...
- 7,135
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 ...
- 12.6k
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 ...
- 4,900
4
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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 ...
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,...
- 1,194
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 ...
- 361
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 ...
- 156
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_{\...
- 1,036
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. ...
- 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 ...
- 1,210
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 ...
- 11.4k
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 ...
- 15.2k
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 ...
- 15.1k
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 ...
- 1,147
3
votes
Accepted
Do 3 blade wind turbines generate more power than a 9 blade, all else being equal?
Because in the real world, all else is never equal, but let's start there analytically.
What does "all else being equal" actually mean?
With respect to a flat swept disk perpendicular to an ideal ...
- 4,900
3
votes
Accepted
Attaching Gear onto Motor
Here you go: https://uk.rs-online.com/web/p/spur-gears/8787907/
The trouble is that a 1MOD 12 Tooth gear has a pitch diameter of 12mm, i.e.the bottom of the teeth is less than 12mm, so once you drill ...
- 7,761
3
votes
Does more downforce affect the acceleration and top speed?
You do not want to overcome the force of static friction when accelerating because that's when the dynamic friction takes over and your wheels slip. That means that the force applied on the edge of ...
- 5,621
3
votes
Why do kWh (smart) meters have a maximum operating altitude?
Expanding item 2 in Tiger Guy's good answer I'd say it's definitely about dielectric strength.
Electronic devices manufacturing standards (e.g. IEC62368-1) define creepage and clearance distances ...
- 295
2
votes
Planned power outage and backup generator
The most practical and simplest is to review the breaker box. Below is an example breaker box for a typical US single family house. Note: US base houses are power using 120 VAC.
Add up total current ...
- 7,135
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