Questions tagged [energy-efficiency]
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77
questions
2
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0answers
29 views
Optimization: Most efficient way for multiple people to move boxes
We are moving house in a few weeks and have a couple of people helping moving the boxes. My previous experience from moving is of queues building up in small hallways and people getting tired from ...
2
votes
0answers
39 views
PMDC Motor Characteristic Graph
I am trying create a graph similar to as shown below. However, I am confused as to how the torque is related to the characteristics.
The graph that is to be replicated for certain parameters:
The ...
0
votes
3answers
58 views
Practicality of energy recovery from HVAC systems?
I've been thinking about ways to maximize efficiency in large buildings, and one thing I thought of was to place some sort of turbine in the exhuast vents or smokestacks of factories, power plants, ...
0
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0answers
22 views
at what point is increasing pressure ratio diminishing in returns?
piston engines of ww2 planes had pressure ratio of at least 10, while jet engines were still vastly superior with a pressure ratio of only 3.
Certainly pressure ratio of 1 would bring 0% fuel ...
-1
votes
1answer
37 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 ...
0
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0answers
81 views
Energy Wasted in Electromagnetic Motor Actuator Vs Human Muscle Actuation
I would like to know if the energy utilized by a robotic arm is greater compared to the energy utilized by human arm. Robotic arm is essentially servo motors that use electromagnetic field to create ...
-1
votes
1answer
30 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
vote
3answers
78 views
Why are some submarines using liquid oxygen for combustion?
I think som submarines like Kockums use liquid oxygen instead of compressed air for driving their combustions engines. Is it more energy efficient to oxygen enrich the air before burning it compared ...
2
votes
0answers
19 views
One dimensional U-Factor Calculation - How to determine indoor / outdoor film resistances
Can someone clarify the ASHRAE Fundamental 2017 (SI Units) (See Below) Indoor and Outdoor film resistances. The manual states that it comes from Table 3 and in the description of table 3 it states &...
1
vote
1answer
54 views
Laser Power vs Efficiency
Is there some kind of graph or relation between laser power and efficiency. What I'm trying to find out is whether the efficiency of a laser decreases with increase in power or is it that there is no ...
5
votes
1answer
115 views
In a diesel engine, does more heat leave the engine through the tailpipe or the radiator?
Diesel exhaust is hot, and there's a lot of it.
Diesel radiators also get pretty hot.
In a typical diesel engine, which one is dissipating more heat?
EDIT: In response to a request for specificity ...
-1
votes
2answers
25 views
Relation between engine size and its power to weight ratio
Is there a relation between engine size and its power to weight ratio? For example if you shrink the engine to half the size will it have exactly half the power?
6
votes
3answers
557 views
Three-phase versus single-phase operation of a generator
My generator (a Fermont MEP-803A, 4 cyl diesel, 10kW rated) can run in three distinct modes:
Single-phase 120V, in which one terminal is hot, and another is neutral
Single-phase 120V/240V, in which ...
1
vote
2answers
49 views
How much weight has weight in fuel efficiency?
Comparing the official fuel efficiency figures for several cars, I was surprised to discover that the Smart Fortwo has a weight between 750 to 800 kg and needs 4.3 L/100 km, but the VW Polo with a ...
3
votes
1answer
31 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
votes
1answer
71 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 ...
2
votes
0answers
22 views
Energy/Efficiency Calculations for Large Multi-stage Package HVAC
I frequently use the Equivalent Full Load Hour (EFLH) estimation method to calculate the expected energy usage for commercial HVAC equipment. While not ideal, it works well enough to given an order ...
6
votes
3answers
828 views
How Much Efficiency is Lost in a Gear Train
I want to get a rough estimate for the transmission efficiency of two different gear trains. One is a one-stage gear train with 11.67:1 ratio (140/12 teeth) and the other is a compound two-stage gear ...
0
votes
0answers
54 views
Most efficient turbine for harnessing energy from bidirectional air flow?
I am currently working on designing an oscillating water column as part of a project. In summary:
OWC are devices with a semi-submerged chamber or hollow open to the
sea below, keeping a trapped ...
2
votes
1answer
42 views
Effect of Pressure on Combustion efficiency (of hydrogen) in excess air
Can somebody explain relation between combustion efficiency and pressure in lean mixtures using any kind of chart or mathematical equations?
At first glance I thought, combustion efficiency increases ...
-1
votes
2answers
35 views
Does utilizing exhaust energy to supercharge (“turbocharging”) increase the thermal efficiency of a gasoline internal combustion engine?
The work done by a turbocharger increases the inlet charge without much of a burden to the exhaust flow. This increases the amount of air (and fuel) that flows into the engine. How does this affect ...
4
votes
2answers
128 views
Do 3 blade wind turbines generate more power than a 9 blade, all else being equal?
After doing some research, I have come to the realization that 3 blade design horizontal turbines have the greatest maximum coefficient of performance. Most sources seem to agree a Cp of ~0.45 at TSR=...
1
vote
3answers
32 views
Efficiency of an engine
What is meant by thermodynamic efficiency of an engine?
and what are the factors that affect the thermodynamic efficiency of a diesel engine?
0
votes
2answers
119 views
Refute my assumption: Bearings Don't Improve Efficiency
If two surfaces rub together with a normal force between them, friction is generated. You could add lubrication between those two surfaces and reduce that friction.
Bearings essentially consist of ...
5
votes
3answers
991 views
Is it true that four-wheel drive is less efficient and if so, why?
I have heard many times that four-wheel drive is less efficient than two-wheel drive. Many car producers have a normal drive mode where only two wheels are powered, and turn the four-wheel drive on ...
0
votes
1answer
559 views
calculating the efficiency of a microwave oven
If I want to calculate the efficiency of a microwave oven, I have the input Energy (= power (watts) x time (s)) and the output which I measured using temperature difference (q=mct).
So do I divide ...
0
votes
2answers
38 views
Would some manufacturing processes be more efficient if driven differentially by a single motor, up to ~150 kW, than multiple lower-rated motors?
I'm writing a discussion paper on the potential energy efficiency benefits of integrating different manufacturing processes by co-location on the same site. One possible field for integration is in ...
3
votes
1answer
87 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
vote
1answer
54 views
Calculate Efficiency Loss of a Leak in a Hydraulic Cylinder
I am trying to figure out what the efficiency loss of a leaking hydraulic cylinder is. This master's thesis found that a controllable pitch propeller (essentially a hydraulic cylinder inside a ...
2
votes
1answer
64 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?
1
vote
1answer
82 views
how would one calculate the % of heat not absorbed by a heat sink?
I'm planning on building a plant growth chamber inside a sealed/insulated 55 g rain barrel, and I'm trying to figure out how much of the heat from my lights will enter the chamber, and how much ...
-2
votes
1answer
32 views
How is the Ampyx Power plain generating energy? [closed]
This is what I'm talking about:
Wikipedia
Youtube video 1
Youtube video 2
Official site
Can you please explain me on how this plane is generating energy? Reeling back the aircraft should consume the ...
0
votes
1answer
284 views
How to calculate actual efficiency of a steam turbine
What are the parameters required to calculate the overall efficiency of a steam turbine and how to calculate. Is there are certain assumptions to be made while calculating the overall efficiency of a ...
0
votes
2answers
49 views
Should I run 2-wheeler at constant speed?
I have been recommended not to run the two-wheeler (Suzuki Access) at a constant speed (I give a constant throttle in a way that I run essentially at a constant speed of about 40-45 kmph). In fact, I ...
3
votes
1answer
320 views
Efficiency and NOx emission of lean burn gas engines
I have a question regarding the efficiency of lean burn gas engines. Maybe it is just a confusion concerning the terminology of "thermal efficiency", "brake mean pressure", "brake thermal efficiency" ...
0
votes
1answer
179 views
Why regenerator “wheels” in a turbine engine?
Back in the early 60s, Chrysler built a turbine car powered by a turbine engine it had under development.
An interesting feature of the engine was a regenerator system to recover heat from the gases ...
2
votes
1answer
582 views
What are the limiting factors on diesel engine compression ratios?
Higher compression ratios in internal combustion engines generally improve the engine's fuel efficiency. But diesel engines don't seem to go above a ratio of 25 or so. What is the limiting factor for ...
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vote
1answer
265 views
Energy consumption of a boiler
I have a question that maybe will be very easy for you.
I am working on a district heating model using Dymola, and now I have to incorporate a boiler into my model, such as this one.
I was asked to ...
0
votes
1answer
27 views
What is the fraction of power transmitted to the generator in full-hybrid cars?
In full-hybrid cars like the Toyota Prius, usually both internal combustion engine (ICE) and electric motor produces mechanical power to the wheels at cruise. But some of the mechanical power produced ...
0
votes
2answers
56 views
Thermal efficiency affected by hertz (Gas turbine)
Take the LMS100 gas turbine for example. Why does the efficiency change when generating power in 50 or 60hz waveform?
0
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1answer
74 views
What is the explanation why Pulse and Glide is more energy-efficient for trains [closed]
I read that trains in pratice instead of acceleration to a certain speed level and holding the speed, they accelerate and then cost, accelerate again, und keep this pattern. This was shown by ...
0
votes
1answer
72 views
Natural gas boiler Vs. Electric Heater efficiency
If a facility buys natural gas at 8 dollars/Mcf to provide heating from an 85% efficient natural gas boiler, what is the equivalent cost of electricity ($/kWh) for a 95% efficient electric heater?
I'...
0
votes
2answers
475 views
How is the energy production of solar and wind compared with the prospect of nuclear fusion? [closed]
I am trying to find reliable information and comparisons about the energy production of renewable energy technologies, specifically, how solar and wind alternatives compare to nuclear fusion.
Why is ...
0
votes
1answer
549 views
What is the maximum efficiency of a mechanical electric generator?
If we apply a simple push to rotate a system of gears to generate electricity, what is the maximum practical and theoretical power efficiency of the system, assuming the push as the only source of ...
0
votes
1answer
53 views
Has anyone achieved significant energy savings by increasing the cooling setpoints in retrofit office buildings, in practice?
I have a simulation based research vs. practical experience type question:
There are a number of academic research papers available which claim 20% to 40% cooling energy savings by increasing the ...
0
votes
1answer
56 views
How the COP differs for a Vapor Compression Chiller without the U*A values of Evaporator/Condenser?
I am trying to find the COP of a VCR system. I can reach the COP with using the EES(Engineering Equation Solver), without dealing with the UA values, i.e. just with the energy balances for the cycle. ...
1
vote
3answers
85 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 ...
0
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2answers
109 views
Can you use the kinetic energy of air to power a car?
In my fluid mechanics class, I've learned that a fluid traveling in a pipe will generate a force when the exit area is smaller then the entrance area. Suppose a pipe is attached to a car that will use ...
3
votes
1answer
189 views
Can combined cycle turbines be small enough for trains?
Combined Cycle Turbines are a gas turbine whose exhaust heat powers a second turbine running on steam. These can get thermal efficiencies greater than 50%, whereas a plain turbine would get 30 to 35%. ...
0
votes
1answer
74 views
cycle efficiency for (otto -diesel -dual) at constant Pr & Temp
It's written that at constant pressure & temperature for Otto & Diesel cycles
the efficiency of diesel is more than efficiency of Otto.
Efficiency = Work / Heat added = 1- (Heat rejected / ...
