# Have seen many Youtube videos related to induction heaters but never for water?

Discussion in 'Radio and Wireless' started by Benny7440, May 14, 2018.

1. ### Benny7440

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Jan 14, 2016
Is there a reason not to use this technology for heating water for taking a shower? I think someone somewhere has tried this already and I want that input before I try it myself! Thanks in advanced.

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Jan 21, 2010

3. ### kellys_eye

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Jun 25, 2010
Probably because the KISS principle applies.

Who wants a 'complicated' water heater?

4. ### Alec_t

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Jul 7, 2015
I agree with Kelly. Standard heating elements would be far more efficient than induction heaters.

5. ### Benny7440

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Jan 14, 2016

First, if you don't try it you cannot compare empirically. Until it hasn't been tried no one can compare the respective efficiecies of both methods.

The safety issue is another angle somehow difficult to assess theoretically. Being involved radio frequencies and respectable levels of power in conjuction with water it demands some analysis.

As you can see, if you put yourselves in my position (almost complete ignorance of the measurable consequences of doing this), you can estimate the pertinence of my query.

6. ### kellys_eye

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Jun 25, 2010
Of COURSE it's been tried......... but you don't even have to 'try' to know.

When it comes to generating heat (for whatever purpose) you can only get out what you put in MINUS ANY LOSSES.

Any form of electronic process is, by design, a LOSS CREATING process. You can't get 100% efficiency nor can you get 101% efficiency.

Heating water DIRECTLY (in an insulated container) is the most efficient method for heating water - the losses being entirely that of heat leakage from the 'insulated' container (and a small fraction lost in the cabling bringing the power to the heater).

If you try to heat it via induction you will also have the same sort of loss but ALSO the loss caused by converting the electrical energy into RF energy - a process as 'inefficient' as 60% in some cases.

7. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Well, actually, with heating water you CAN be more efficient.

A heat pump can deliver more heat to the water than is consumed electrically.

8. ### kellys_eye

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Jun 25, 2010
Yes, if you buy already-boiling water (in bottles) you can get 100% efficiency..........

but your example fails to take into account the energy used to create, build and install the heat pump - so, no, you can't......

9. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Ok, if one defines efficiency by comparing the change in total thermal energy of the water with the electrical energy required to operate the device to cause that change, then a heat pump is more efficient, able to add Y kW of heat energy with an expenditure of X kW of electrical energy (and where Y > X). For purely resistive heating, Y can approach X, but never exceed it.

10. ### kellys_eye

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Jun 25, 2010
....it can't be exceeded no matter what method you use - in the case of the OP's question, induction heating would be one of the worst and least efficient!

What you've done is extrapolate the OP's original question to include PRE-heating of the water to reduce the amount of energy required to increase its temperature anyway - which is why I joked about using bottled boiling water to start with!

On a straight energy-to-hot water conversion process there is nothing simpler than resistive, nothing more efficient (on a stand-alone basis) where any losses are purely thermal leakage. A heating coil in an insulated tank is the standard example - and very efficient.

We see a lot of advertising for electrical heating systems that claim they are more efficient than whatever but in fact all they are doing is adjusting the time and process of creating, storing and/or releasing the generated heat - they can't (and don't) do it any more 'efficiently' as they claim they can.

If you want 1kW of heat you use 1kW of energy (disregarding losses) and no 'method' will get you that 1kW out without the 1kW in - on a purely electrical basis anyway. The snake oil salesmen that claim their 'new, improved' heating systems can be more efficient (????) are con men, pure and simple.

You might get the heat at a time and place of your choosing but you won't get that 1kW out without putting 1kW in - end of.

11. ### duke37

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Jan 9, 2011
Where do you find a heat pump the can deliver more than 50C? I considered a ground source heat pump to heat my house using a stream at 10C. The coefficient of performance was rubbish above 50C and the installation cost was astronomic.

12. ### kellys_eye

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Jun 25, 2010
ahhh... but, but, but..... you'll be saving the WORLD man! /sarc off

13. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
https://www.energymatters.com.au/solar-hot-water/solar-heat-pumps/

When I was in NZ last (in the middle of winter) people were starting to install heat pump space heaters. They certainly work with ambient temperatures < 0C.

Of course it can. It's a heat pump. You're expending energy to move heat from one place to another -- the cool part gets cooler and the hot part gets hotter (zero net change). Heating is especially efficient because you benefit from the "waste" heat too.

14. ### kellys_eye

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Jun 25, 2010
...so Y is NEVER going to be greater than X then....... my point exactly. You can't get more out than you put in.

And 'efficiency' is a relative term - take at face value I suppose it is but taken at it's true cost I don't think so (ROI).
....making my point for me.

15. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
No, the amount of heat going into the water (Y) is much larger than the amount of electrical energy expended (X).

16. ### Benny7440

88
1
Jan 14, 2016

First, if you don't try it you cannot compare empirically. Until it hasn't been tried no one can compare the respective efficiecies of both methods.

The safety issue is another angle somehow difficult to assess theoretically. Being involved radio frequencies and respectable levels of power in conjuction with water it demands some analysis.

As you can see, if you put yourselves in my position (almost complete ignorance of the measurable consequences of doing this), you can estimate the pertinence of my query

17. ### Benny7440

88
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Jan 14, 2016
As long as we limit ourselves into looking at the electric energy usage we can estimate accurately the efficiency of this AWA other circuits. But, if we expand one's horizon of variables to be included other conclusions might arise...

I was thinking of assigning a value to 'experiment' itself. If you consider that I might have a working/repairable DC to AC converter around (~400 Watts) a 'usable' car batt. and that I'm living in Puerto Rico after been hit by 2 great hurricanes just a little over 8 months ago you might also would think of putting these things into work for the sake of lowering not only electricity bills but the demand on the system.

Many years ago I found myself at a deadend when considering the outcome of doing the following:
if you have 2 identical shower-water-heaters, what's the final water temperature in each of the following scenarios:
1) the two are physically connected in series but electrically in parallel;
2) the two are physically connected in parallel as well as electrically;
3) the two are physically connected in series as well as electrically;
4) the two are physically connected in parallel but electrically in series.

There're some conclusions that arise automatically but included above for the sake of completeness in relation to the original exposure of the problem. I tried to obtain help on this in some forums but never got to the point of been able to conclude anything. I mention it here because I hope the same doesn't happens now: I want to get convinced that there's no other logical way of doing it but considering everything exposed.

18. ### kellys_eye

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Jun 25, 2010
Not true. Where theories have been established, proven, tried and tested you can apply the results to practical examples such as the one you describe.

The first and second laws of thermodynamics are paramount here - I suggest you read up on them.

Your original proposition of using induction heating simply increase the losses of the system as the induction heating process itself is (a LOT) less than 100% efficient.

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