# Questions tagged [energy-efficiency]

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### How does the efficiency curve of a well pump shift with speed?

Well pump manufacturers publish "efficiency curves" for well pumps, such as this one (the curve that is most sharply convex down, whose Y axis is read from the "% EFF" scale on the ...
0 votes
1 answer
116 views

### Which power plant will generate more electricity in the below discussed scenario?

There are two identical power plants(i.e same turbine dimension and same generator configuration). Both have a hot reservoir. Coal is burnt on both power plant to make the temperature of the hot ...
0 votes
0 answers
20 views

### What is the lowest energy solution for emptying a drip irrigation water collector : a mono-stable solenoid valve or a bistable coupled to a pump?

I have a water collector I want to empty everyday for drip irrigation. It is controlled by a micro-controller. I have identified three solutions: Use a bi-stable electro-valve and a pump: advantage ...
0 votes
1 answer
53 views

### Understanding "total primary energy supply"

I am trying to wrap my head around the diagram and explanation here but can not understand completely how it is computed. https://energyeducation.ca/encyclopedia/Total_primary_energy_supply For ...
0 votes
1 answer
37 views

### Heating pump/refrigerator - calculate efficiency

I'm wondering how I can calculate the overall thermal efficiency of my heating/refrigerator pump. Actually I have this AC/heating pump unit from Samsung (P/N: AR09TXFYBWKNEE). I've placed a power ...
0 votes
0 answers
30 views

### Understanding small DC motor curves (torque, efficiency etc)

I have a small DC motor/gearbox unit and the spec sheets is shown below. All* the units are measured at the gear box output, so 100 RPM would be 3,000 at the motor. I'm using it as a generator so am ...
0 votes
4 answers
97 views

### Is it better to charge my electric car on windy days?

There are various dashboards (for example, here) that show the current energy generation mix and the overall CO2 emissions (gCO2/kWh). In the UK renewables can make up a large proportion of the total, ...
1 vote
0 answers
21 views

### How to calculate the actual COP of a compression for a given outdoor temperature?

Given a chiller having a nominal COP value, how can we compute the actual COP for a given outdoor temperature. In this regard, is there any difference between compression chillers and absorption ...
2 votes
4 answers
415 views

### How turbo engines increase efficiency if have lower compression ratio than naturally aspirated engines?

I know that efficiency depends on compression ratio(CR), NA engines always has higher CR than turbos,so how turbo engine can have better efficiency?
-1 votes
1 answer
49 views

### Minimizing home heating costs [closed]

I live in an old rental house with 12 foot ceilings and zero ceiling fans. I am trying to conserve as much energy as possible as heating costs are expensive. I have placed plastic on all of my windows ...
0 votes
2 answers
107 views

### What would be a reasonable estimate for the amount of petroleum needed to find, produce and deliver one barrel of petroleum?

A basic "balance sheet" might allocate fuel needed for exploration, well development, production, crude oil transportation, refining, further product transportation and delivery to a ...
2 votes
1 answer
80 views

### Converting between MMBTU and MWh

a quick question: I want to convert between MMBTU and MWh to get at emission factors from energy. I have the following information: I use the data given in 40 CFR 98 (see EPA source here) by the EPA ...
2 votes
1 answer
192 views

### Dehumidification calculations

I'm looking at options for DIY dehumidification and am hoping to get a sanity check on some calculations, and verification that I'm using the right factors in the right way. As a reference point, I ...
1 vote
0 answers
56 views

### How are NASA's mars rovers able to operate with such little energy?

The latest Mars rover being, NASA's Perseverance, uses the Multi-mission radioisotope thermoelectric generator, which has a maximum power output at the beginning of it's operational life of 125 watts, ...
1 vote
1 answer
58 views

### What is the efficiency of direct electric heating versus water heated via electricity?

I am attempting to keep plants warm in a greenhouse. Therefore, I assume that heating the soil should be most efficient, as that's what plants seem to care about the most (i.e. the temperature of the ...
1 vote
0 answers
31 views

2 votes
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### 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
3 answers
1k 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
1 answer
1k 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 ...
3 votes
1 answer
131 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 ...
9 votes
1 answer
4k 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 ...
0 votes
0 answers
81 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 ...
0 votes
2 answers
40 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 ...
-2 votes
2 answers
44 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 ...