13 votes

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

Distributed DC power is actually used in some new construction. It's driven less by the efficiency of the transformer than by other logistics. Here in California, at least, we have a law (known as ...
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  • 4,501
12 votes

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

Yes: Something like this has been commonly done in the U.S. for decades. Both Incandescent undercabinet lights and exterior low-voltage "landscape" lighting are often run from a single 12V ...
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  • 1,785
11 votes

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

If you can replicate what you report above under controlled conditions then you can retire for life next year. Really. The overwhelming opinion by all reputable test houses or suitably competent ...
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10 votes
Accepted

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

The fridge works by pumping heat from its interior to its exterior. The amount of work it needs to do is proportional to the amount of heat entering the interior (and also the temperature difference ...
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  • 6,719
10 votes
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How to design a house to be cooled passively?

In dry/arid areas a wind catcher tower in conjunction with a qanat is a great way to keep buildings cool. The underground water stays cool and cools the air passing over it that is drawn in through ...
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  • 5,930
9 votes

Is it true that four-wheel drive is less efficient and if so, why?

Simply put, power transmission is not free. Every time you have some energy over here, and you want to move it to over there, you are going to lose some of it in the process. In this case, if your ...
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  • 2,511
8 votes

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

Silica gel is the standard for most purposes. It's the desiccant you find inside those paper sachets packed with new electronic equipment. It consists of tiny beads of silicon dioxide that are ...
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  • 3,681
7 votes
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In a diesel engine, does more heat leave the engine through the tailpipe or the radiator?

They are very nearly equal for typical four-stroke non-turbo diesels under load. A turbo diesel under load should have slightly more radiator loss than exhaust loss. At the bottom is a link to the ...
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  • 3,381
6 votes

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

There are two aspects to this. First if your fridge is filled with anything other than air then you will save the energy associated with cold air escaping whenever you open the door. However if ...
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6 votes

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

If you have unused space in the fridge, then it's better to fill it with something than to leave it air. This is because every time you open the door, less air will be exchanged with the room, so ...
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  • 11.2k
6 votes
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Refute my assumption: Bearings Don't Improve Efficiency

Your initial assumption is a bit flawed. You can not just draw the conclusion that all friction is the same. It is like saying all birds i know of can fly thus all birds can fly. Which is obviously ...
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  • 3,360
6 votes
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How Much Efficiency is Lost in a Gear Train

Generally gear trains with lower ratios are more efficient due to reduced amount of sliding action between the gear teeth in mesh, so the compound gear train would probably be a better solution. That ...
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  • 2,402
6 votes

Three-phase versus single-phase operation of a generator

But I'm thinking it may be better (more efficient maybe? less vibration maybe?) to run it in three-phase mode, with the load balanced among the three hot terminals. Correct. Figure 1. The load is ...
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  • 7,519
5 votes

Does The W*nkBand Work?

Because this question has proven a little more derisive than I had anticipated (where's that engineering sense of fun/humour?)- I thought I'd attempt an answer as well, if only to prove it's an ...
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5 votes
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What is the theoretical maximum energy efficiency of hydro turbines?

Something can only be 100% efficient when a lot of generous assumptions are taken into account. If you assume: No friction (turbine surface, turbulence, nozzle, or bearings) Perfect cup design (100%...
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  • 7,444
4 votes
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Where to insulate Underfloor air distribution system in a temperate climate

It depends — can you run air through the plenum without simultaneously running the active heating/cooling system? If not, you'll never get the benefit of its thermal storage capacity. For ...
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  • 6,719
4 votes
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Third Rail vs Overhead Cable: which is more efficient in terms of electricity consumption?

Your "Bonus question" holds the answer here. Assuming that the two trains are perfectly identical, and that the power consumption is identical (which, if you have the same weight, motor, and size, it ...
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4 votes

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

There are many factors that make BLE low power, and I have attempted to address as many of them as possible. In order to better understand the power consumption differences between Bluetooth classic ...
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4 votes
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Can combined cycle turbines be small enough for trains?

We can try to answer this question by looking at existing equipment in terms of size and weight and make an educated guess from there if all this fits on a train. Our CC will consist of: Gas turbine ...
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  • 4,618
4 votes
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Question about flow temperature and storage temperature in a cogeneration plant

when the cogeneration plant switches of upon reaching 85°C flow and without another heat source, there's no way to reach 95°C. Are you sure the switch-off happens at 85°C flow, and not at 75°C return ...
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  • 4,618
4 votes

Practicality of energy recovery from HVAC systems?

So, if I understand correctly you are proposing to use a turbine in the exhaust vents in order to reclaim the energy from the flowing air. However, in most cases the air is flowing due to forced flow, ...
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  • 22.6k
4 votes
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Natural ways for passively cooling/heating a home?

There are many ways that one can achieve natural cooling and heating. However, the best solutions are very dependent on the situation. Also, the problem with most of these solutions is that you'd need ...
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  • 22.6k
4 votes

More efficient to use LED lighting than to open blinds for light and thereby lose heat when very cold outside?

The reason your utility company recommends to let the sunshine in is not to save on lighting energy. it is to take advantage of solar radition energy. a window can let the solar radiation in two ways, ...
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  • 20.9k
3 votes
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What theoretical efficiencies can wind / hydro turbines achieve?

The theoretical maximum efficiency of a wind turbine is the Betz Limit, which is $\frac{16}{27}$ ( ~ 59.3%). The result dates back to 1919. The Betz limit is, as you note, speed invariant. To get an ...
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  • 3,681
3 votes
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Are there any methods to work out what appliances are running in my home from an aggregate power consumption sampled 6 times a minute?

The word that will unlock your searching is disaggregation - there's quite a lot of research going on right now into energy disaggregation. These generally involve some kind of learning algorithm, ...
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  • 3,681
3 votes

Why are freezerless refrigerators more efficient?

Heat flux is directly proportional to gradient of temperature - in other words, if you have an imperfect insulation wall, it will pass the more heat the higher the temperature difference between its ...
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  • 6,113
3 votes

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

RV, camping, boating, and solar power industry might have had a significant influence in developing LED blubs powered by 12V DC. The automotive industry too might have had some influence. Some of the ...
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3 votes

How is the energy production of solar and wind compared with the prospect of nuclear fusion?

The reality of generating electricity from nuclear fusion on an industrial scale is still a very long ways off. It is speculative high cost, high risk venture, with a potential high payoff far off ...
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3 votes
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Why regenerator "wheels" in a turbine engine?

The main advantage of a rotary regenerator is that you can pack a lot more surface area into a given volume than with a shell and tube type device important for gas-gas heat exchange where heat ...
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