Questions tagged [energy]
The energy tag has no usage guidance.
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0answers
16 views
My Question is how to build a bird feeder and water access for winter birds, that can be self powered to keep water from freeze [closed]
I will like to build a bird feeder and water access for winter birds. The challenge being using a combination of wind and solar power to keep water from freezing.
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1answer
57 views
Calculating the Braking Energy of a vehicle
you might find my question stupid. I am unfortunately not an engineer and didn't find the answer on google.
I want to calculate the braking energy of a vehicle decelerating from v2 to v1 (km/h). ...
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1answer
45 views
Deriving the equations of motion for free-floating spacecraft with a single link robot arm
Note: I had previously posted this question on the Space and Robotics SE sites, but received little/no response. So I've deleted the previous posts and repasted my question here in the hope of ...
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1answer
35 views
Conductive Heat Transfer calculation over time
I am trying to heat the oil in a 1/2 inch thick rectangular steel box by using an Insulated heated blanket covered on all 6 faces of the box, the working conditions of the operation are at -50 Celsius,...
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1answer
20 views
What are the necessary qualitative criteria for the existence of limit cycles
The literature on the existence of limit cycles is replete with complex and abstract mathematical analysis. Or for specific systems of specific structure, specific mathematical criteria that determine ...
2
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1answer
77 views
How to convert Joules(kinetic energy) plot chart into watts?
How to convert Joules(kinetic energy) plot chart into watts?
Anyone know how?
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1answer
37 views
Converting grams of fuel per kWh of energy
Is there a database showing how many grams of a particular fuel generates how many Kilowatt hours of electricity?
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1answer
53 views
Trying to understand how much it costs to run my clothes dryer
I am trying to calculate the running cost of my clothes dryer and have bought myself an energy meter to check its usage.
I plugged the meter in, reset it, and then turned it over to the aggregate kWh ...
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1answer
40 views
Modeling the stiffness of a membrane
I'm trying to model, in MATLAB, a membrane in 2D which has an initial triangle-like shape.
This membrane has pressure acting on it from the inside. There are also some pulling forces in random ...
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2answers
36 views
Theoretical maximum generated power for a given torque
Being an electrical engineer, I'm hoping someone will help me double-check my math. I have a small circuit that I want to power for years that consumes an average 10uA at 3V.
I'd like to power this ...
2
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1answer
157 views
What are the differences between compressor stations, pump stations, and booster stations?
I am doing some research on impacts related to natural gas compressor stations. In some states, I've received data for compressor stations alongside other facilities in the oil and gas world. These ...
1
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1answer
41 views
What are the conditions for a signal to be an energy signal and a power signal?
I know how to find the power and the energy of a signal. What I have a problem with is knowing whether a signal is an energy signal or a power signal.
According to my teacher, a signal is a power ...
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2answers
47 views
How do I solve for the mole and mass flow rates in a system?
I've been trying to solve this problem for a while with no success. I think I figured out that $m_1$ is $420 kg/hr$ and that $n_{3,A} = 3 kmol/h$ using the mass balance equation:
$input-output+...
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4answers
132 views
Why can't energy be entirely recovered from a moving car's rotating wheels?
I have a friend who isn't properly visualizing energy loss in a moving car.
His idea: Cars that can run forever without being recharged - - > while the engine rotates the front wheels the move the ...
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1answer
74 views
Determine the strain energy of a bar
I have a Structures question about determining strain energy that I am unable to solve. I have attempted it and I have the answer, I would appreciate if if someone can just tell me where I am going ...
2
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1answer
79 views
How do generators in space transmit/ deposit energy back to Earth? [closed]
I've read about the idea of putting solar panels in space, or the already used electrodynamic tethers which gain energy as they move through Earth's magnetic field.
The question I have is:
How do ...
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1answer
524 views
Specific energy vs Specific power in batteries
When looking at the Wikipedia page for Lithium-ion batteries, one can see that there are some technical details such as Specific Energy and Specific Power, but I don't know how to connect them.
For ...
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2answers
70 views
How much braking force do cars generate?
I've been trying to find actual figures for the braking power of cars (in order to determine things like stopping time). As I understand it this comes in two parts: the maximum force that the brakes ...
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2answers
76 views
Momentum of a free-floating body being hit by a projectile
The Problem
I'm proposing a 2D problem in the x-y plane. Say there is a free-floating disk of radius R and mass Md (no velocity), at which a projectile is shot. The projectile (velocity Vp, mass Mp) ...
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2answers
68 views
Magnetic Entrapped Storage at 0 gravity
I understand this is a multifaceted question and I apologize . All of it is relevant to be understood.
On Earth Fly wheel storage devices are used as an alternative to batteries. Even with magnetic ...
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1answer
28 views
Why do pumped storage hydroelectric facilities use bent pipes? [closed]
When a reservoir is used to store water for electricity, it's pipes are usually laid in several segments on the ground to reach its source, such as a lake. It seems that if the pipes went directly to ...
3
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2answers
75 views
Compressed air energy storage?
I'm wondering, if you put an air compressor pipe into a micro turbine, lets say something like that attached to a motor, does air that get out of the turbine have the same energy as when it gets in ?
...
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1answer
39 views
Could Internal Ionisation Engine be a description of electric cars?
Petrol powered cars are sometimes described as having an "Internal Combustion Engine" (ICE). This describes the chemical processes happening inside the engine: mainly the combustion of petrol.
Could ...
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1answer
58 views
Elevator standby + moving passanger , electricity consumption changes
I'm interested specific on electricity consumption changes on 2 different situations inside an elevator.
When the elevator is stopped and people enters the elevator, does it change in any way the ...
3
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1answer
83 views
How do you calculate the Enthalpy of a geothermal resource?
Enthalpy seems to be commonly used to characterize geothermal reservoirs, but how is it calculated? I have an example here where the enthalpy is cited as 800 $kJ kg^{-1}$ for a reservoir with a ...
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1answer
22 views
Power from piezo material
Suppose there is a given piezoelectric material and under a given force it produces voltage $V$. If an external electric circuit is attached with load $R$, the current will be $I= V/R$. Also power ...
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1answer
118 views
Derivation: Entropy of Vaporisation using Redlich-Kwong EoS
The part I'm stuck on is the last part. Basically, the question is to obtain the following equation for the entropy of vaporisation using the Redlich-Kwong equation:
$$
\Delta S = R\Bigg[ \ln \frac{...
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3answers
121 views
4 Way Bugatti Tug of War
The reasoning for this question comes out of pure curiosity.
say if there were, for example 4 bugatti veyron's ( represented by the rectangles on the diagram) all starting from the middle and all ...
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3answers
76 views
Radioactive Materials to Energy AT HOME
Is there a way to use a radioactive elements (Americium in my case, but for demo, any radioactive material) to create a usable amount of energy (Power small LED?) AT HOME! Using materials that can be ...
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2answers
110 views
Light bulbs with highest energy efficiency [closed]
Most specs for light bulbs list luminous efficiency (or, more accurately sometimes, luminous efficacy) but not energy efficiency. Luminous efficacy tells you how bright the light is as observed by a ...
2
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2answers
84 views
Can we make significant energy from human waste? [closed]
I am trying to find if making energy from human waste (excrement, sewage) is profitable? Lets say I live in a city of 16 million people which does not put waste into use. What could be the ...
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0answers
27 views
Exergy and Gibbs Energy
I'm wondering if there is any difference between Gibbs Free Energy and Exergy because their definition seems to me the same $\Delta H - Tenv*\Delta S $
Exergy represents the maximum amount of work ...
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2answers
123 views
Calculate efficiency of water heating
I have a heating system with which I heat up 10 liters of water by 24.2°C in 610 seconds.
My system consumed 0.5 KW of electric energy in this time.
Now I used this formula:
Specific heat ...
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1answer
332 views
How does pressure energy convert to thermal in incompressible flow?
I am thinking of a straight thermally isolated pipe, and incompressible flow through it.
Due to friction, pressure energy drop of fluid, (increase of internal energy), can be calculated via the Darcy–...
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6answers
1k views
Working hours of power plant generators
My question might seem a simple one, but it has been troubling me for a while.
How many hours in a day do conventional electrical generators work (the ones in large power plants)?
Do they by any ...
4
votes
1answer
440 views
Getting high RPM out of a low RPM motor
I'm trying to use a 1500 RPM-rated electric motor to accelerate a (light, 25kg) shaft up to 50 000 RPM. At these speeds I figure using a belt system or roller chains is out of the question due to wear ...
3
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1answer
804 views
Why use different specific heat capacities in the energy equations for incompressible and compressible fluid flow?
Background:
I notice that there is quite a bit of similarity between the standard heat equation and the energy equation (from the navier stokes equations). The heat equation is given as
$$\frac{\...
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1answer
246 views
Energy of a 3D Timoshenko beam
I am interested in the kinetic energy T and the potential energy U of a three dimensional Timoshenko beam.
For a 2D Timoshenko beam the energies read:
$$ T = \dfrac{1}{2} \int\limits_o^l \left( \rho ...
2
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1answer
393 views
How do I calculate the additional energy required to pump fluid through a restriction?
Let's say I have a pump pushing fluid through a 250 ft pipe, 1.5'' diameter, at a rate of 20 gallons per minute. I would like to calculate the delta in energy required to pump this fluid with and ...
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1answer
495 views
Need advice answering this kinetics of particles energy method dynamics problem
Problem 3/155 The light rod is pivoted at O and carries the 2kg and 4kg particles. If the rod is released from rest at $\theta=60°$ and swings in the vertical plane, calculate (a) the velocity $v$ of ...
3
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1answer
4k views
Calculating torque needed to climb a graded hill
I've been designing an electric skateboard which is driven by only one of the rear wheels (for the moment). As I was picking out motors for the board, I soon realized I would need to find a balance ...
4
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2answers
358 views
Turning an engine over with engine compression
When you compress a bicycle pump and seal the opening, the pump will automatically return to it's initial position when you release it. I suppose this is how air suspension works as well?
if you have ...
2
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1answer
89 views
Short power outage, deliberate?
The power went out in my block just now, so I got in my car and drove around and found a utility truck next to a pole that is at the junction between the block circuit and an adjoining circuit (which ...
4
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2answers
3k views
Relationship between wind velocity, turbine rotor diameter, and power output
I'm trying to understand and identify the equations to use in defining the relationship between wind velocity, turbine rotor diameter, and power output for a wind turbine.
To simplify my question, ...
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1answer
66 views
Required mass of wood to produce 20 Watts/Hour
Requirements:
I need to produce $20\ \mathrm{W}\,\mathrm{hr}^{-1}$ by burning wood.
The specific energy of wood is $21\ \mathrm{MJ}\,\mathrm{kg}$
Find the required mass of wood to produce $20\ \...
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1answer
139 views
Why isn't trash ground into dust and used as fuel? [closed]
Combustible dust is known as an explosion hazard, especially in large factories etc. They can create powerful explosions and bring down entire buildings if it is disturbed by a large enough vibration ...
5
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1answer
330 views
How could we possibly harness the energy from the Earth's negative charge?
I've been reading the Feynman lectures, and in this lecture about lightning, he describes how the Earth is negatively charged, and how there is thus an electric field of about $100\ \tfrac{\text{V}}{\...
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1answer
1k views
What kind of signal is the signum function? A power signal or an energy signal?
I'm studying "signals and systems". We can indentify two kinds of signals: power signal and energy signal.
The definitions are:
Energy of a time-continous signal
$$ E_x = \int_{-\infty}^{+\infty}{|x(...
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2answers
202 views
How to automatically process energy meter data considering outliers and meter reset?
I want to algorithmically process energy meter data. The energy meter measures a heat or power producer or a heat or power consumer (but not both, so the measured energy will always have a positive ...
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2answers
863 views
Can the Sabatier reaction power a vehicle?
The Sabatier reaction converts CO2 to methane. Can a vehicle that burns methane recover it (at least some part) from the exhaust gases via the Sabatier reaction? I am interested to know how this would ...
