efficient solar stovetop compared to induction cooktop

[Mike90250]

Crock pots only have minimal insulation, and generally, no thermostat. If trying to run one on DC, you have to set the heat range first, then plug it in. It's internal switch will burn out very quickly if you try to use it on DC.

[Mike90250]

Just found a review of some heating efficiencies. Was run as a comparison for gas ranges (how has the best burner) but they also included electrics and induction. Induction was by far, the most efficient of everything.

http://applianceadvisor.com/content/peoples-cooktop-test

For years, we've been told that:
- sealed burners improve your sex lives
- that glass electric tops are the closest thing to Godliness
- that real cooking performance only comes at high-cost, clad in a stainless steel box
- and to shun and/or ridicule our neighbors with open burners or using propane.
Are these truisms true? Have we ridiculed our neighbors in error? Can we handle the truth?

[steveg]

Induction Cooking - OffGrid

Hi Plateauhops,

As another data point for you - I have an Asko induction cooktop we run in our off-grid home - use it most days that and the oven (less often).

Works really well - only hiccup is when we turn on another inductive load once we are using it - other than that no problem.

We have a Latronics 7kW pure sine inverter.

[Sunking]

Works really well - only hiccup is when we turn on another inductive load once we are using it - other than that no problem.

We have a Latronics 7kW pure sine inverter.

What size are the induction transformers in watts? That sounds like a basic design problem. In particular the batteries are undersized and/or too small of wiring. Resulting in you are taking too large of a voltage drop between the batteries and inverter.

[steveg]

Hi,

No the switched mode supplies in the cooker are susectable to voltage variations in mains power supply from inverter - I talked to latronics and they said to put a 20uf cap on it - which I havent done yet, but I have the cap.

No design flaw there - this is a 3kW inductive load ... one-two elements on full.

We have run all 4 elements with pots simmering - and the oven on.

Inverter has a 20kW surge rating - batteries are very close to inverter and are LiFePO4 so can deliver more power faster than Pb acid in any case as internal resistance is very low and no peukert effects.

[Sunking]

Hi,

No the switched mode supplies in the cooker are susectable to voltage variations in mains power supply from inverter - I talked to latronics and they said to put a 20uf cap on it - which I havent done yet, but I have the cap.

OK that makes sense as inverters are SOFT SOURCES that do not play well with inductive loads with low Power Factors, unlike the utility with Brute Hard Source.

[steveg]

OK that makes sense as inverters are SOFT SOURCES that do not play well with inductive loads with low Power Factors, unlike the utility with Brute Hard Source.

Correct!

[ionized]

I must be missing something. You can't be saying that a installing a stupid 20uf capacitor on your inverter fixes all of your poor power-factor loads? If so, why did not the inverter manufacturer do that in the original design?

How on earth did you get the inverter manufacturer to talk to you about modifying their equipment? Jeez, when I asked a stupid dishwasher manufacturer what water temp was the max that their input could be, the only answer they would provide is that the plumbing code for domestic hot water temp is 120 F

[ionized]

Getting back to the original post subject. A rice cooker might be a very efficient way to cook vegetables and, of course, rice. It might be more efficient than the microwave. Anyone know what the power factor is for a microwave oven?

Heating up a pot of relatively cool water is a measure of efficiency, but might not be the best indicator of cooking efficiency of all manners of cooking. At a stable cooking temperature, and lower hob power settings heat loss from the whole assembly becomes significant and heat transfer rates into the whole assembly are much lower. I think that would tend to make heat transfer rates trend toward more favorable for resistive electric and gas hobs.

The results at Applianceadvisor are interesting. I will probably look them over some more. It is not surprising that higher power hobs are less efficient in their tests. There has to be a sweet spot in the efficiency curve, however. Heating too slow will allow the heat transfer out of the pot to be more dominant. There is also the load on the HVAC system to consider in hot weather. That would favor the hotter, faster, burners. Again, since I recently became aware of power factor considerations, I wonder how badly that would affect the comparison of induction cooking.

[Sunking]

I must be missing something. You can't be saying that a installing a stupid 20uf capacitor on your inverter fixes all of your poor power-factor loads? If so, why did not the inverter manufacturer do that in the original design?

I think he was talking to the Induction Cook Top manufacture, not the inverter manufacture.

[steveg]

I must be missing something. You can't be saying that a installing a stupid 20uf capacitor on your inverter fixes all of your poor power-factor loads? If so, why did not the inverter manufacturer do that in the original design?

How on earth did you get the inverter manufacturer to talk to you about modifying their equipment? Jeez, when I asked a stupid dishwasher manufacturer what water temp was the max that their input could be, the only answer they would provide is that the plumbing code for domestic hot water temp is 120 F

Hi,

The *Inverter* manufacturer said I put the cap at the cooktop end of supply to help with the variations with the inductive load. And it's not an insubstantial cap - is 20uF bipolar AC capacitor at 600V

[billvon]

I must be missing something. You can't be saying that a installing a stupid 20uf capacitor on your inverter fixes all of your poor power-factor loads?

It is common to balance inductive loads with capacitors. It's the cheap and easy way to reduce power factor distortion due to inductive loads.

If so, why did not the inverter manufacturer do that in the original design?

Because then it wouldn't work with more capacitive loads.

[Sunking]

It is common to balance inductive loads with capacitors. It's the cheap and easy way to reduce power factor distortion due to inductive loads.
Because then it wouldn't work with more capacitive loads.

Well there is the crux of a possible problem. Being hard wired in at the stove the Caps are always in the circuit. Being located a distance away helps, but in residential that distance is not meaningful. So there maybe problems with non-linear loads when the stove top is not in operation. Easy fix if a problem is noticed is a switch.

Problems if they occur will be in non-linear electronic items with switch mode power supplies. Things like TV's, Stereo's, and Computers.

[solorone]

Just curious, why not use propane?

[solorone]

Just found a review of some heating efficiencies. Was run as a comparison for gas ranges (how has the best burner) but they also included electrics and induction. Induction was by far, the most efficient of everything.

http://applianceadvisor.com/content/peoples-cooktop-test

For years, we've been told that:
- sealed burners improve your sex lives
- that glass electric tops are the closest thing to Godliness
- that real cooking performance only comes at high-cost, clad in a stainless steel box
- and to shun and/or ridicule our neighbors with open burners or using propane.
Are these truisms true? Have we ridiculed our neighbors in error? Can we handle the truth?

Thanks for posting the link, might have to try the test.

I was a bit surprised at the LP efficiency's, but not at all surprised at how well the cheaper stoves performed,, sort like a car, cheap 4 wheels and a motor will get you there, just as well as 70K worth of of wheels and motor will. Of course the there is the exception, the Lamborghini induction model, gets your fast and in style... LOL