Induction vs Gas Cooking

[s/v Jedi]

About tying to shore after a week of sailing because of garbage, water, shopping etc. : were it not for covid, we would be in our 6-month provisioning challenge which means we bring all that we need for 6 months and we return with all the garbage from those 6 months. All 100% home cooked meals, home baked bread, granola, yogurt and all drinks and so on.

All that fits 85 liter fridge capacity and 180 liter freezer capacity. Much is done by (pressure) canning, pickling and vacuum packing. I am sure itis not thathard to increase this to 12 months.

Back to induction vs propane cooking: for boats with a diesel genset this is a no-brainer. In all other cases it gets complicated and needs experimentation which is easy as a portable induction unit is cheap and fits on top of your propane stove.

You need more though: a convection oven at minimum. We also have a microwave oven (mostly used during passaging), bread maker (also used as dough maker) and since a couple of days, a small electric rice cooker. These extras save power and enable us to have only a single induction hob. After experimenting for years, we went to professional grade, portable single hob induction cooktops (Cooktek, Vollrath). One of the upcoming projects is to replace the gimbal propane range with a gimbal cabinet that has a surface for a portable induction cooktop or anything you can need (making coffee etc) on top and a shelf for a microwave underneath

[a64pilot]

Originally Posted by Dockhead

OK, that makes sense.


Generator hours are costly -- fuel is the least of it.



I would probably look at it very differently if I were off grid 365 days a year. As it is, I'm not off grid all the time, or even on the boat all the time, and so I have only 2000-odd hours on my generator after 10+ years, and as it's a heavy duty continuous rated one, I'll never wear it out even if I live to 100. So it's a sunk cost and I don't hesitate to use it. I'm using up hours I already paid for.




I see and understand that your case is different.


Solar of course is brilliant and even more brilliant for those who are off grid continuously, for the reasons you state. I would love to have it myself (had it on my last boat and loved it). Just can't deal with the windage on this boat.

You really don’t have a need for Solar either, Solar only in my opinion makes sense for those that spend a lot of time on their boat, and not in a Marina, and ideally at anchor or sailing.

However most of this you just can’t make too much of a case for economics, I will never, ever save enough fuel to pay for the likely $40,000 of Sails and rigging, chainplates etc that I have, even if I cruised for 10 more years, where all that makes sense is of course for those honest World travelers, but alas I’m not and never will be one of them.

[Dockhead]

Originally Posted by a64pilot

. . . However most of this you just can’t make too much of a case for economics, I will never, ever save enough fuel to pay for the likely $40,000 of Sails and rigging, chainplates etc that I have, even if I cruised for 10 more years, where all that makes sense is of course for those honest World travelers, but alas I’m not and never will be one of them.

Nothing about sailing is economical. The amortization of good sails per mile is much more costly than diesel fuel.


Professionally crewed sail superyachts always motor only, when the owner is not on board. In order not to wear out the sails. I was berthed next to Bristolian for a week in Tallinn last summer, after being berthed across from her in Cowes during part of the winter. I got to know the pro skipper, and heard a lot about that.

[Dockhead]

Originally Posted by s/v Jedi

. . . Back to induction vs propane cooking: for boats with a diesel genset this is a no-brainer. In all other cases it gets complicated and needs experimentation which is easy as a portable induction unit is cheap and fits on top of your propane stove.

You need more though: a convection oven at minimum. We also have a microwave oven (mostly used during passaging), bread maker (also used as dough maker) and since a couple of days, a small electric rice cooker. These extras save power and enable us to have only a single induction hob. After experimenting for years, we went to professional grade, portable single hob induction cooktops (Cooktek, Vollrath). One of the upcoming projects is to replace the gimbal propane range with a gimbal cabinet that has a surface for a portable induction cooktop or anything you can need (making coffee etc) on top and a shelf for a microwave underneath

Are you using induction exclusively? Do you have lithium batts? Do you just run the generator when using the induction cooker?

[a64pilot]

Originally Posted by noelex 77

Slow charging produces a higher battery efficiency for lead acid batteries. This is exactly what most yacht solar systems do.



It is a very common misconception that charging slowly produces long absorption times. The opposite is true charging slowly produces shorter, not longer absorption times.

Lead acid battery efficiency is excellent during the bulk phase, especially the early part of the bulk phase, is less in the absorption phase, but with solar charging the slow rate produces short absorption times. We are typically in absorption only 20-30 mins a day. On days of poor solar production where battery efficiency is more critical, the time in the absorption phase is even less. This is quite different to generator based charging where absorption times are typically a couple of hours.

I want to expand on this, the reason why often the absorption times are short is the charge rate is so low that several hours were spent attempting to get to absorption voltage but as the charge was so low you couldn’t make it, your charging of course, just not at absorption voltage, it’s why in my opinion that timers for X hours in Bulk and X hours in absorption are at best a guess, in order to be sure your fully charged the timers have to be set too long so that your often overcharging.
You can of course fully 100% recharge a battery and never get to absorption voltage, even float voltage there is some charging, not much as the “pressure” is so low, but there is charging, may take days though to get to 100%
The only way I know of to fully charge a bank without overcharging is one of two ways, either trailing charge amps at absorption voltage, or by amp counting how many amps you put back into a battery.
I know from experience my bank requires about 110% of the amps removed to be put back to achieve a full charge, lifeline says the number is between 106% and 110%, but my bank is apparently sulphated so it’s at the higher end.
So bottom line, by whatever means you use to charge, even shorepower and a BIG charger, it’s going to take about 5 to 6 hours Min to fully charge the bank, because of its charge profile, as in low output at the beginning where a bank can take its highest amps, Solar can take longer than 5 or 6 hours to fully charge, and there are times of the year and some days when you just don’t have that many Solar hours.

People who’s Solar is just coming on line by 9AM are not fully charged by noon, not with LA batteries anyway.
Dec and Jan I’m not usually getting Solar to exceed house load by much before 9AM, no real charging until 10 AM and the Solar day is over before 6PM, so there are times that a 30 min generator run guarantees a full charge, even if the afternoon ends up being cloudy as my Solar now terminates at trailing amps, I may be full just after lunch and go to float if the day ends up being a bright sunny one with no clouds and my stern facing South so the mast doesn’t shade the panels.

[noelex 77]

Originally Posted by a64pilot

trailing charge amps at absorption voltage

This is the most accurate and easiest way. Your battery monitor will show the voltage and current.

If you miss the transition between absorption and float, switch the solar charge controller back to absorption and the current should quickly drop back to the correct trailing amp (or battery return amp) reading, thereby confirming the drop to float was done at the correct time. Following the confirmation, change back to float.

The popular Victron controllers do not appear to have an easy mechanism to switch back to absorption, but there is an trick. Set the “equalisation” voltage to the same value as absorption then with a button click you can switch the absorption phase off and on. It is even easier with the new firmware, as all solar controllers on the network will make the change. A very short equalisation time can be selected so you don’t even need to change back.

If you do need to do a true equalisation charge, you need to change the voltage to the correct value, but on most battery types this only needs to be done occasionally. For my gel batteries it is not required at all.

[Auspicious]

Originally Posted by s/v Jedi

One of the upcoming projects is to replace the gimbal propane range with a gimbal cabinet that has a surface for a portable induction cooktop or anything you can need (making coffee etc) on top and a shelf for a microwave underneath

I certainly would not do that. If you're going to, look at combo microwaves. They are a convection oven and a microwave together in one box. Worth a look.

You'll have the same problem with tabletop appliances (convection ovens, microwaves) that you do with propane cookers - poor insulation. That's really what makes the boat warm when you cook. The solution is better insulation (ha!) and ventilation.

[Dsanduril]

This thread + a slow day = finding a somewhat dated (2014) and possibly not unbiased paper on the efficiency of induction cooking. Their test was simply heating a pot of water (10lb/4.5kg) from room temp (70/21) to near boiling (200/93). They found that with the right size pot (i.e. one that fully covers the burner element) resistive electric coils were the most efficient (and with the "wrong" pot size they were terrible). Induction came in a relatively close second, with the distinct advantage that pot size vs. "burner" size was immaterial. Gas was a distant third. Their bottom line was pretty favorable toward induction, you can read the paper for the details.

[Adelie]

Originally Posted by noelex 77

Solar panel efficiency can calculated from the specifications. The number does not indicate the output of the panel in different conditions, but rather the size of the panel in relation to rated wattage.

So a 100w high efficiency panel will not produce any more power (all other things being equal) than a 100w low efficiency panel under the standard test conditions. However, the high efficiency panel will be smaller in area, which is a big help with a boat installation.

As a general rule, high efficiency panels are also better quality and produce slightly more power in average conditions, but this is only a general observation rather than a firm rule.

The formula for efficiency is 0.1 x the specified maximum output of the panel divided by the area of the panel in m ².

Solar panel specifications for the reputable brands is measured under identical conditions and is quite accurate. However, this does not tell you how various panels will perform in different illumination conditions and in the real world as the panel heats up. The temperature coefficient is generally quoted and this is worth comparing, and some manufacturers list the performance at different brightness levels.

The NOCT specifications were commonly included a few years ago, and this is arguably a better way to compare real world output. However, few manufacturers seem to quote this standard anymore.

The problem is not me doing the math (4yr engineering degree solved that), the problem is trusting the numbers provided by the manufacturer/vendor.

The only way to really know it to do your own testing.

[Dsanduril]

If you don’t want to trust the manufacturer then look at the performance guarantee, and more importantly the re-insurer for that guarantee. The money guys at the reputable re-insurers invest a lot of money in third-party testing from PVEL/DNV, Intertek, and similar companies.

Also look at modules/panels that are used in large commercial/utility installations; the performance guarantees at those sites get down to 1% for decades of rated performance and carry huge dollar penalties.

All the guarantees (or nearly all) go out the window when you install on a boat, but at least they give you an idea of the quality (as long as you do a little work to evaluate the quality of the guarantee).

[Adelie]

Originally Posted by Dsanduril

If you don’t want to trust the manufacturer then look at the performance guarantee, and more importantly the re-insurer for that guarantee. The money guys at the reputable re-insurers invest a lot of money in third-party testing from PVEL/DNV, Intertek, and similar companies.

Also look at modules/panels that are used in large commercial/utility installations; the performance guarantees at those sites get down to 1% for decades of rated performance and carry huge dollar penalties.

All the guarantees (or nearly all) go out the window when you install on a boat, but at least they give you an idea of the quality (as long as you do a little work to evaluate the quality of the guarantee).

Those are all big panels which mostly won't fit on a boat.

My approach is to get a mid-priced panel.

[wingssail]

Originally Posted by Adelie

Those are all big panels which mostly won't fit on a boat.

My approach is to get a mid-priced panel.

My approach is to forego the helo landing pad on the back and go with smaller panels, ditch the electric cooking and use gas. Keep the boat light, simple, and fast.

[Auspicious]

Jeepers. I posted a long response to everyone except Seaworthy Lass which I opened by saying her post required more thought than my break from billable work allowed. I came back tonight to follow up and find that something happened to that post. Now I’ll have to reconstruct that.

Ladies first.

Originally Posted by Seaworthy Lass

There are a myriad of aspects to consider when debating the topic of “Induction vs Gas Cooking”. A few spring to mind (I am sure I have forgotten countless ):

Safety

Cost of:
Purchase
Installation
Spares

Space needed

Ease of installation

Reliability

Maintenance required (amount and cost)

Ease of sourcing spare parts or replacement

Ease of carrying spares (cost, space)

Any smell when turned on

Any byproducts of combustion

Heat generated by the appliance

Power issues:
Is an additional power source required
Cost of the power (capital and ongoing)
Reliability of the power source
Safety
Labour required to provide the power
Other drawbacks of the power source eg noise, smell
Heat generated

Equipment needed to cook (anything special required or anything that can’t be used that you wish to)

Amount and control of heat (speed, degree)

Time taken to cook

Can it produce the type of food you are content eating

Quality of food produced

Ease of cleaning

Pleasure using

How much time you enjoy spending in the galley

How much you enjoy indulging in good food on a daily basis

Cosmetics

What backups can be used

Can the backups provide you with the food you do not wish to ever need to do without

And CRITICALLY: How flexible are you and how happy are you to modify what you do?

I think we’ve talked about all those things except for cosmetics already in this thread. Aesthetics are personal. We only peripherally engaged on “live to cook” vice “cook to live.” For the others gas is arguably better across the board. I think you should scroll back and read the thread from the beginning. You might want to look up FMEA as well. Go ahead. We’ll wait. There will be a quiz. *grin*

Originally Posted by Seaworthy Lass

The importance of EACH of these considerations needs to be weighed up carefully and will vary from person to person.

This is true. It is important to differentiate between the merits of the considerations (facts) and the weighing of those considerations in the decision-making process. There are people who think riding motorcycles wearing shorts and flip-flops and without a helmet is reasonable. There are those who think the first batch of people should be institutionalized. *grin*

That was easier than I expected when I skimmed your long post.

Originally Posted by Seaworthy Lass

In our case we fitted a gas stove as we simply did not have the power to run an electric galley all year around (we wanted the option of cruise at anchor in winter at higher latitudes when the sun barely skims the horizon all day and for not much more than 6 hours in total). For a host of reasons did not wish to be generator dependent and it was a very high priority for us not to install one.

We have done everything possible to make the gas installation and use as safe as possible.

We have tried to minimise the frequency gas bottles need to be replaced/refilled by storing 3 x 12 kg bottles (with the capacity for 3 more).

That all sounds reasonable. I will point out that LPG continues to be the most common cooking fuel across the planet although losing ground in First World urban areas. You can get it anywhere there are people. In my opinion those who say otherwise are not organized enough to source it. Granted I am administratively creative and have even managed to get tanks filled for non-US cruisers here in the US despite not having OPD valves fitted.

Originally Posted by Seaworthy Lass

1. For us, replacing or refilling gas bottles is truly difficult, as we do not wish to tie up anywhere in between our two yearly haul out (again for a host of reasons) amd we enjoy more remote anchorages away from civilisation. This is a personal choice, but a high priority for us. In winter in Greece on our previous boat I would run through a 10 kg bottle in 3 weeks. As I said, I am a keen cook. It was an absolute pain replacing the bottles.

Why is a dinghy ride not sufficient? Are your tanks fixed to the boat? A full 12 kg tanks is lighter than a full Jerry jug of water. That said 10 kg of propane in three weeks is really a lot. That’s two to three times the rate of even other “keen cooks.” How do you eat that much food?

Originally Posted by Seaworthy Lass

2. In winter the moisture released as a byproduct of gas combustion is a huge issue. Any condensation is unbearable for me, particularly in winter.

With even moderately good ventilation humidity from the products of combustion does not compete with the humidity from cooking itself. Steam from boiling pasta water (sshhh – don’t tell Dockhead – he abhors the stuff), rice, soups, even stews. Let’s not forget that a huge source of humidity on board is people breathing. We’re really horrible sources of humidity. The real challenge is thermal conductivity of mountings for hatches and portlights. The metal gets cold and falls below the dew point. Condensation happens. That can be managed. First and most important is ventilation. Yes, outside air in high latitudes is cold but it is also dry. This is where forced air diesel heaters shine. You can draw domestic air from outside and heat it rather than recirculate inside air that just gets wetter and wetter. For other substantial heat sources such as diesel hydronic and your Reflex heater you have to provide the ventilation yourself. I’m not suggesting throwing open the boat. You don’t need that much make-up air. There are technical references for this in the HVAC-R community. I posted a specific reference to a lay publication above.

Originally Posted by Seaworthy Lass

By learning to recently successfully “bake” in a frypan I have been using our diesel Refleks hotplate this past winter for all cooking, and an electric kettle and an induction hotplate (very easily powered by solar, even for hours on end) the rest of the time. Our gas has been turned off at the bottle for nearly seven months now, something I would have thought impossible given I am a super keen cook and our oven was previously used at least once daily.

I could use some numbers here for how in high latitudes you can run an induction hob for hours on end off solar at low angles for only a few hours per day. How much solar do you have?

I take no issue with cooking on your Reflex although temperature control is a challenge. I can recommend the fourth edition of Joy of Cooking from the US. It’s old enough that much of the constituency cooked over wood or coal stoves.

[Adelie]

Originally Posted by Dsanduril

In some senses this topic/thread resembles the electric propulsion threads - is there enough electricity available for the described task? I think cooking, using a 95%+ solar powered boat is much closer to reality than propulsion.

The trouble I perceive is that the standard LA battery installation is not well suited to this. For induction cooking we're talking about loads very similar to the anchor windlass, for longer periods of time, frequently when the sun isn't strong. That means the batteries need to perform (if you aren't willing to fire up a generator). For windlasses, many boat manufacturer's now put an interlock between the engine and the windlass controls to attempt to make sure the user doesn't overload both the windlass and the (LA) batteries. That's because with LA pulling .05C or .1C out for long periods is just fine, but once you get to .2C or .3C or somewhere in that range voltage starts to sag, Peukert rears his ugly head, and things start to go off the rails. In the end it may still be cheaper and easier (for many people) to just put in a larger LA bank to keep the C-rate down, but to me it makes a very strong argument for a more efficient storage system so you can readily transfer energy usage away from peak generation times.

I think limiting short term draws to 0.1C is excessively conservative. Yes there is more voltage drop at 0.2 or 0.3C but not so much that the inverter drops out, unless you are already at 50% DoD, then the problem is not discharge rate.

If you are pulling 1200W and limit current to 0.25C then you will need at least a 400Ah bank. I have a 300Ah bank on my 20' boat.

Comparisons to a windlass are misleading. A windlass is going to be at the end of a long run of cable with significant voltage drop just for the distance. The inverter should be positioned as close to the battery as possible to minimize voltage drop for this reason.

[Auspicious]

If any feels I didn’t respond to anything I blame the lost post. Here is my attempt at reconstruction.

Originally Posted by Dockhead

That's only with ideal pans and only when heating with max power. The big advantage of induction is you don't heat up the air or anything around -- all the heat goes into the food.

Not really. On gas heat is generated by combustion and heats pan and air by conduction, convection, and radiation. The hot pan and food also heats air by conduction and radiation (I think convection is de minimis). Induction heats the pan and the pan heats food and surrounding air. Secondary heat reduces the efficiency differential between gas and induction.

Originally Posted by Dockhead

With real life pans and at medium temperatures I guess it's several times more efficient.

I had a long train of reasoning first time around. You’re going to need footnotes for that assertion. I simply don’t believe it. With real-life pans you’ll have many more losses and radiation.

By the way, we haven’t talked about the famous induction buzz of cookware. Bonding of disparate materials is critical and you need to buy rather expensive cookware to avoid the buzz.

I have friends who are professional chefs. They crew for me. I fill in for them when they need someone they can depend on. I ran an omelet station at a breakfast buffet with a couple of catering gas burners and an induction hob. I did not see anything like the time differential you speak of side-by-side. Catering burners by the way are cheaper than induction hobs. *grin*

Originally Posted by Dockhead

And changes in temperature are almost instantaneous because there is no thermal mass save only the bottom of the pan, to change temperature of induction is fantastic for simmering something, because it's a doddle to get the exact simmer without burning, and hold it there exactly. It's very efficient for simmering because you're not bleeding heat into the air and not maintaining temp of whole apparatus.

The thermal mass of the two is the same, absent the little metal grate on a gas cooker. Maintaining a simmer isn’t a problem for most people either way. For many the UI of induction slows things down.

Originally Posted by Dockhead

Who waved off cost? I never did. We agree on this.

I agree you did not. I’m writing for our broader audience. Not everyone will appreciate the full context we have expressed in this thread and elsewhere.

Originally Posted by Dockhead

So in that case you have really significantly improved safety -- by exactly, the entire quantum of risk you had by having gas on board.

Risk doesn’t work that way. Subsidiary risk is not additive. It increases the total risk but not by addition. I don’t remember the math but I can look it up. I do remember that the lower the subsidiary risk the smaller the portion that gets aggregated. Quantitative risk assessment is not my specialty. I’ve had such people work for me in the past.

Originally Posted by Pete7

Earlier in the thread some recommended aluminium covered in stainless steel. Surely copper covered in stainless steel will transmit the heat more effectively?

Absolutely. Copper has twice the thermal conductivity of aluminum, which in turn is much better than cast iron or mild steels. This is why Revere Ware was so popular at one time. The cost of copper has greatly increased and aluminum and clad aluminum is the current best value for money, especially in commercial cookery. If you want something really great for heat distribution you can find copper cookware with stainless steel or even silver cladding inside. If you can afford that you can hire a boat boy to keep it polished. *grin*