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Questions tagged [energy-efficiency]

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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
74 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 ...
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1answer
28 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 ...
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1answer
48 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 ...
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2answers
42 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
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1answer
71 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" ...
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1answer
43 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
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1answer
76 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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1answer
116 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 ...
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1answer
24 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 ...
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2answers
41 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?
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1answer
57 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 ...
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1answer
40 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'...
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2answers
230 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 ...
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1answer
384 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
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1answer
41 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
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1answer
48 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. ...
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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
82 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 ...
2
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1answer
113 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%. ...
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1answer
56 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 / ...
1
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1answer
247 views

What is the difference (if any) in capacity factors and efficiency between reservoir hydropower and run-of-river power plants?

My question is about differences between reservoir-hydropower and run-of-river power plants. Are run-of-river plants less efficient? what would be an approximate guess of the differences? (assuming ...
0
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1answer
37 views

Efficiency of off road vehicles [closed]

Im working on efficienxy of heavy vehicle. Since i never had any experience with this kimd of things ( cars ) i dont have so much insight in what kind of efficiencys are important in vehicle. I have ...
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1answer
2k views

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

It is known that Bluetooth Low Energy transmits data only during short time intervals called Connection Events. Connection events occur regullary with predefined period. The rest of the time Bluetooth ...
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1answer
41 views

Power/Efficiency of expanding air-flow

Assuming, I've got a machine, that runs with pressurized air and provides the following measurements: $\dot m$ - mass-flow through the machine (same for input and output) $p_{1}$ - input pressure $...
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4answers
1k views

What is the theoretical maximum energy efficiency of hydro turbines?

From what I've read it seems that hydro turbines can theoretically achieve 100% energy conversion from kinetic to electrical energy. However, I just wanted to double check if this was true.
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1answer
100 views

Best fuel for supercar engines

To experienced supercar owners/engineers: What is the best fuel for a turbocharged 6 liter V8, 7.6 liter V10, or 9.2 liter V12 (Audi R8 or Lamborghini Aventador type cars) in terms of speed/...
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2answers
84 views

What's more energy efficient: fewer air conditioners working at max capacity or more working at part capacity?

The central heat and air in the house I'm renting is unable to keep the house below 80 °F during the hot summer here (100 °F days). We've had 3 HVAC techs out to look at it and they all say there's "...
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2answers
122 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 ...
2
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2answers
210 views

Transporting water uphill at the highest efficiency possible?

I have a passing interest in water desalination projects. One of the challenges of desalination is simply moving the water from the ocean to the desalination plant. Typically the plant is built above ...
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1answer
1k views

Relationship Between Gear Ratio and DC Motor Power Consumption

In my class, we are currently trying to understand the relationship between gear ratio and motor power consumption. Given two gears, one attached to a motor, and the other attached to a string ...
0
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1answer
47 views

Daylighting, how to improve coverage

I am doing this daylighting project for which we must bring the light far down into a bunker. I have found . I have heard and read that the quantity of light that you bring in a cable decreases, 60% ...
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5answers
2k views

Difference in energy consumption between empty fridge and fridge filled with bottles of water

I have about 12 bottles of water. If I want to minimize the energy consumption of my refrigerator, should I put these bottles in the fridge or leave them out?
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1answer
67 views

Are there any methods to work out what appliances are running in my home from an aggregate power consumption sampled 6 times a minute?

I recently got a gizmo installed at home that samples my electricity usage once every 10 seconds. I've become a little transfixed watching the graph update as various appliances in my home turn on and ...
0
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1answer
248 views

Equations relevant to gravity powered clocks and machines such as the gravity light

What equations are needed to describe the forces and properties of the kind of mechanisms used in a machine that harnesses the gravitational potential energy of a suspended weight to rotate the shaft ...
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1answer
111 views

What theoretical efficiencies can wind / hydro turbines achieve? [closed]

The high water has some energy E = mgh. In the basic school, we were told that hydropower plants extract the energy of "falling water". Now, that banned principle says that if your water falls upon ...
5
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1answer
429 views

Third Rail vs Overhead Cable: which is more efficient in terms of electricity consumption?

I'm well aware that there are many different factors to be considered, such as ease of installation/maintenance, conversion from AC to DC, environment, distance, speed, frequency of turns, and so ...
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1answer
137 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 ...
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2answers
350 views

Why are freezerless refrigerators more efficient?

Why are freezerless refrigerators more efficient and just out of curiosity, about how much energy can I save per month per cubic feet by going all-refrigerator?
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4answers
1k views

Is there a more active passive technique for removing humidity from the air besides salt blocks?

We can get really humid days sometimes. Recently I was digging around in boxes and found some old mineral specimens, and I set out a few of the salt crystal rocks. I soon found that they had pools of ...
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1answer
72 views

seperate engines working vs single engine [closed]

Assuming we have 2 identical cars. What is the total energy consumed by the two cars to start and accelerate up to a specific speed versus the total energy for one of them to accelerate up to a ...
3
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1answer
2k views

Do magnetic fields applied to a fuel line have an effect on heat output?

I am doing my final year engineering project on Magnetic Field Assisted Combustion and was curious to see what people thought about it. Companies sell rare earth magnetic arrangements to be attached ...
5
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2answers
678 views

Is the fill factor of a photo-voltaic cell constant?

An important factor in specifying the efficiency of photo-voltaic (PV) cells is called the fill factor (FF). It is defined as the ratio of the maximum power of the cell to the product of the open-...
4
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1answer
221 views

Does The W*nkBand Work?

A certain product (link: Metro, somewhat safe for work) is currently trending on social media, that allows men to convert the kinetic energy of their more vigorous personal activities into electrical ...
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2answers
733 views

What is the best insulation wall for a house? ACC wall, Cavity wall, etc

Normally, people use Autoclaved Aerated Concrete (AAC) to build a concrete house because ACC is a good thermal insulation brick that easy to buy and not expensive ...
5
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1answer
80 views

Where to insulate Underfloor air distribution system in a temperate climate

I have a proposed underfloor air distribution system (UFAD) for a one level office in a temperate climate. Typically the demand for heating and cooling in this climate is about even for offices. ...
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1answer
2k views

How to design a house to be cooled passively? [duplicate]

I live in Louisiana these days, in an area that is known for its numerous antebellum plantation homes (circa early 1800s). While touring one of these homes it was clear that almost everything about ...
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4answers
18k views

Would it make sense to have a 12V lighting circuit in a house?

Modern LED bulbs must convert the standard household supply (for example $240\text{V AC}$ in the UK) into a DC supply at a lower voltage (usually $12\text{V DC}$ I think) for the LED array. This is ...