Questions tagged [energy]

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2
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2answers
111 views

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

I have seen many diagrams (see attached) that indicate that modern 3 blade turbines are nearly 50% efficient, which is about 80% of the Betz limit. Betz calculated his limit based on a theoretical ...
1
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0answers
28 views

Equations of motion in matrix form and energy consumption

I am working on Lagrangian derived high-dimensional motion equations for a robot in matrix form. The structure of such an equation is known: $M(q)\ddot{q}+C(q,\dot{q})\dot{q}+G(q)=0$ In here, $M(q)$, $...
3
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2answers
64 views

What are some technical problems with generating electricity using a gas turbine or combustible engine at a gas flaring site?

Numerous oil and gas exploration sites practice flaring for safety and disposal of unwanted low calorific gases. However, instead of just standalone burning the gas, why can't a gas turbine or ...
4
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1answer
168 views

What does MM prefix mean in MMtoe?

I was reading documents about energy importation and came across the following: The import was of 5,915.87 MMtoe I wonder if MMtoe = $10^6*10^6$ toe = $10^{12}$ toe. First time coming across a ...
4
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1answer
76 views

Why do monocrystalline solar cells have rounded/cropped edges?

What is the meaning of this croped part? Why do they crop it, rather than let it be full square?
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0answers
47 views

Why do solar cells need to be square-shaped?

There were circular solar cells 30 years ago. Why do we have square-shaped solar cells now? Why square? Furthermore, Why do monocrystalline solar cells have rounded/cropped edges?
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0answers
49 views

Why does a system with zero resultant moment turn after temporarily force-tilted?

Say a beam, 3m long from end to end, has a pivot placed at its centre of mass, at half its length i.e. 1.5m. Objects with weight 200N each are placed on both ends of the beam. The system is in ...
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0answers
20 views

Why doesn't the Stress Power in the theorem of the expended mechanical power contribute to the kinetic energy?

The following is the formula of the expended mechanical power: $P(t)$ $=$ $\frac{d}{dt}$ $\int \frac{1}{2} \rho\ v^2 dV$ $+$ $\int \sigma \colon d\ dV$ where $P(t)$ is the mechanical power entering ...
0
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1answer
34 views

Half-life Unit Notations

I was looking for some element's half-life, on the following website: http://nucleardata.nuclear.lu.se/toi/listnuc.asp?sql=&A1=214&A2=214&Z=88 For 214,88-Ra, the half-life is shown to be: ...
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2answers
41 views

How to determine energy dissipated from work applied on a load cell

I am using a load cell to see how much force people can apply on it, to help determine their health. I am integrating the force applied on the bracket in Newtons in relationship to time, giving me the ...
1
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1answer
27 views

Weibull distribution Units - ENGIEQSOL

I am using Engineering Equation Solver, and it has been telling me the units of my distribution are inconsistent. According to a the book I am reading, I think it should be unitless (as it is a ...
1
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2answers
65 views

Bernoulli equation on moving cart

Let’s say I have moving cart with velocity U . And water from pipe flows at velocity V with respect to ground The question asks to use Bernoulli equation , pressure is atmospheric in the top If I use ...
0
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1answer
50 views

Why am I getting wrong value here?

A man threw a ball with force 10 N to two displacement of 5 m and 10 m. F = ma, so let mass be 2 kg. a = 5 m/s2. Work done = 10 × 5 and 10 × 10 = 50 Nm and 100 Nm. Now, since a = 5, I assumed that ...
1
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1answer
38 views

Can we say kinetic energy is tangential K.E?

I saw this in my textbook that $\dfrac{\text{d}K}{\text{d}t} = \dfrac{\text{d}(1/2mv^2)}{\text{d}t}= F_t v$ where $F_t$ is the resultant tangential force on the body. Now, let $F_t= F\cos\theta$ $$\...
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1answer
37 views

What does the author mean? Turbomachinery - Reaction

I am reading a book of Fundamental Energy Systems. The author describes the rate of change in head for a turbomachine as: $$ \frac{1}{2}[(V_1^2-V_2^2)+(U_1^2-U_2^2)+(V_{R2}^2-V_{R1}^2)] = H =U_1V_{u1} ...
1
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1answer
28 views

Statistics on energy mix in Europe [closed]

Does anybody know where to find statistics on the energy mix in Europe (preferred by country)? I can only find the share of renewables. I'd like to see the whole mix with a split into energy sources (...
1
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2answers
42 views

Hydraulic energy recovery for high-pressure, low flow (non-steady state) conditions

What would be the best way to implement hydraulic energy recovery while de-pressurizing a pressurized volume of silicone oil initially at 1500 bar. Can a piston pump be concievably repurposed as a ...
0
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1answer
55 views

Is oil collapsing [closed]

Oil industry in permain basin is collapsing. Also, no new technology or anything to save it this time. Is this the beginning of the end for oil?
20
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4answers
4k views

How does turning off electric appliances save energy

We all know if we use less electricity we save energy. But the energy we're getting is result of burning (not necessarily the literal meaning) the fuel. Even if we don't use that energy that fuel is ...
0
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0answers
30 views

How energy intensive is creating artificial islands in the IJsselmeer?

The City of Amsterdam is building a series of artificial islands for new housing. One of them is Centrumeiland. Its size is 13 ha. (130,000 m2). Its creation requires 800,000 m3 of sand (Source), i.e. ...
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2answers
57 views

Why do some metals with bcc structure show ductile-brittle transition in charpy impact test?

I was learning about the charpy impact test and came across the graph on this webiste that shows the impact energy for bcc and fcc structures as a function of temperature. I tried searching for an ...
3
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2answers
136 views

How high will a flywheel catapult launch a payload?

First off, this is not a homework question or anything like that. I'm trying to build a catapult to launch a payload using a flywheel as an energy device! It goes like this: The flywheel spins up to ...
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0answers
28 views

Determine Heating costs in $/kWh for a specific location

Suppose I wanted to find the average heating price for a specific location in the US, where: heating_price: The price of equivalent unit energy intensity of heating energy source (e.g. natural gas), ...
-1
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1answer
71 views

Capacity credit vs capacity factor

What is the difference between capacity factor and capacity credit? I know that capacity factor = annual generation / (installed capacity * 8760) but I don't understand how capacity credit is ...
-1
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1answer
52 views

Fluid Mechanics Question

I am preparing for GATE(Chemical). I need the answer of this question part 2 (question 54) as I am not able to find the mistake in my logic. I have applied the logic here as: Initial energy stored in ...
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1answer
65 views

How much time to melt marshmallow under heat lamp?

Using the Specific Heat Formula, I found that I need to apply 612J of heat to melt 18g of marshmallow. Marshmallow has a specific heat of 2 J/(g*C), melting point of 98.6°F, and a starting room ...
-1
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1answer
32 views

Why Do Airborne Wind Energy Systems Use Kites And Not Balloons?

Title says it all, Why are AWE-companies like Makani spending years and millions of dollars developing drones, rather than simply using a balloon-based design? Wouldn't it be easier and faster to get ...
-1
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2answers
55 views

Kinetic energy of a rigid body

A homogeneous disk with radius $R$ and mass $m$ rolls without sliding on a horizontal fixed plane. Peripheral point $A$ has velocity $v$. Determine the kinetic force of the disk. In my textbook they ...
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1answer
30 views

Clothoid Curve / Euler Spiral Energy Transfer

I've seen in an advertisement that Clothoid curves–also known as Euler Spirals–"transfer maximum energy" to a ball bearing that is rolled down it. Firstly, I was wondering if that might be ...
-1
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1answer
58 views

calculating energy usage with measuring the temperature

I am an electrical engineer working on a project. My goal of this project is to make an IoT solution where I continuously measure the temperature of room in a building. I want to calculate the amount ...
0
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0answers
32 views

Why is the functional of an elastic system equal to it's total potential energy and why is it stationary at it's minimum?

Okay this was even quite difficult to formulate but let's start with some statement's in my FEM book: Elastic continuum has a functional which is equal to it's total potential energy Elastic system ...
2
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1answer
60 views

Understanding the total energy in a AA battery

AA batteries have about 4 watt-hours (14400 joules, 10620.9 pound-feet). Ignoring losses, does that mean a AA battery could theoretically lift 10,620.9 pounds, 1 foot high? You'd need an electric ...
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0answers
21 views

How do I correctly model this system of torsion springs?

I am currently designing a symmetric parallel mechanism that can be modeled as follows: Here, $\tau^j$ denotes actuator moments and $k_i$ are torsion springs constants. For a specific point in the ...
2
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1answer
46 views

What are the key technical challenges to development of traveling wave reactors?

I recently learned about traveling wave reactors (TWRs) on the Netflix Bill Gates special, as an example of a cutting-edge technology Gates is funding which has the potential solve several ...
7
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2answers
548 views

Calculation of the stored energy for a heat storage tank

There is a heat storage tank that is directly loaded from the top and the heat is also taken from the top. The colder water from the heating circuit return flow enters the heat storage tank at the ...
3
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1answer
32 views

Question about flow temperature and storage temperature in a cogeneration plant

Let's assume I have a cogeneration plant that produces heat with a nominal output. The heat is given into a heat storage tank, which is filled from above. The maximum flow temperature of the ...
5
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1answer
114 views

Calculation of the specific CO2 emission of a cogeneration plant for the produced electricity

Suppose I have a cogeneration plant that runs on natural gas and produces heat and electricity. The heat effeicieny is $\eta_{th} = 0.4$ and the electricity efficiency is $\eta_{el} = 0.4$. The ...
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2answers
30 views

Uses of orifice in Water Jet Cutting?

I wonder whats the usage of orifice/orifice plate in Water Jet Cutting Machines. To increase pressure(due to a smaller diameter with respect to the entrance cross-sectional area) or to convert to ...
1
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1answer
45 views

How to estimate wind generation using power curve?

I am trying to verify windfarmer generation estimates manually. To do so I am trying to manually calculate the estimated energy production (kWh) of a wind turbine. The information I have available is ...
3
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1answer
49 views

Clutch role in a micro hydropower

I've recently visited an old (about 60 years old) micro hydroelectric standalone installation. Total electric power is about 3 kW A/C. A local told me between generator + fly-wheel and turbine there ...
2
votes
3answers
175 views

Gasturbine energy balance

I have a question regarding gasturbine energy balance, the total energy that flows into the gasturbine is given 12 MW and the power needed for the compressor is 4.4 MW and the turbine power is 9.3 MW....
1
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0answers
52 views

Enthalpy vs Heat

If we have a closed cylinder filled with a gas and we heat it, by $1^{st}$ law we have: $\Delta q=\Delta U$ (?) since $\Delta V$ = 0. But $\Delta H= \Delta U+ V. \Delta P$. What does that difference ...
3
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1answer
109 views

What is the difference between a diffuser and a duct in turbines?

I have been reading this paper, which addresses the advantages of diffusers in cross flow turbines. The abstract says (emphasis is mine): A CP’s extraordinary improving resulted when yaw increased ...
1
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1answer
456 views

Force and Kinetic Energy on a Speed Bump

I have done a basic calculation of the force at an angle on the speed bump when the car makes a contact on it (please check the attached image), now I wanted to calculate the kinetic energy that I can ...
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0answers
73 views

Ideas on optimization of DRA and energy consumption of a pipeline

I have a 200 mile pipeline with a few pump stations in between. I am trying to find ways to optimize the electricity and DRA consumption, and was wondering if anyone has ever done something similar ...
1
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1answer
779 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). ...
0
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1answer
623 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 ...
0
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1answer
62 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,...
2
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1answer
24 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
190 views

How to convert Joules(kinetic energy) plot chart into watts?

How to convert Joules(kinetic energy) plot chart into watts? Anyone know how?