We just remodelled our kitchen here at Base Camp. (Don’t worry, I’m not going off topic, I will explain how this is relevant to boats in a moment.)
Being a cook who firmly believes that if some heat is good, more and faster heat must be better, I always liked cooking on gas, but because our kitchen is so tiny there was no way to get the clearances required for that fuel, so we went with a Bosch induction cooktop.
And now I’m a induction convert. Instant off-on like gas, but way easier to precisely control (think simmer), and one hell of a lot easier to clean than a gas cooktop—you would know how fantastic this last benefit is if you had ever cleaned up after I cooked a meal.
So now that I’m an induction fan-boy, I started wondering whether it’s practical on a boat, and, if so, what modifications to the electrical system would be required to support it.
And, yes, I have seen a couple of videos by yachties extolling the virtues of induction. But the glaring problem, in common with most videos, is the lack of consumption numbers, never mind boring old math, or even simple arithmetic.
Yup, our job here at AAC is to bore you with detailed analysis…that will help you go into a project with an overall understanding of what’s required for success, or even just save you from doing something ill-advised and expensive.
This analysis was made possible because we also bought a single-burner induction cooker (to supplement the four-burner cooktop when cooking big meals like Christmas dinner) so we have a practical test rig.
So go get a Red Bull, don’t want you nodding off, and let’s dig in:
I once wrote an article on the practicality of running AC off batteries. In fact, my AC was set up so that I could do just that. It consumed about 480 Ah overnight (small unit, good insulation), which was more than my small bank could actually manage, but I did use it to get out of steamy marinas and into the breeze in the morning. Recharging with solar would also be a real stretch.
An easy way to convert heating requirements to watts is (pounds of water)x(1BTU/pound-F)x(change in temperature in F)x(0.29 watt-hr/BTU). Thus, heating a cup (8 ounces) to boiling (212-70=142F) takes 22 watt-hr, or about 2 Ah. Add for heating the metal and the air. Boiling water away, such as reducing a sauce, takes about 1000 BTU/pound (less, but this is easy to remember), so boiling a cup of water away takes 145 watt-hrs plus losses.
Yeah, unless you have a catamaran with a LOT of roof space and sail south, claiming all-solar is a stretch. My PDQ, for example, could do very well in the summer (gas cooking, no AC), but when the sun got lower in the winter I struggled to fill the batteries. I saved amps on refrigeration in the winter, but they were offset by running the heat (gas). And that is with a lot of roof space.
Hi Drew,
That’s some useful stuff to know, thank you. And yes I remember your piece on running air from the batteries and I have even referred a couple of people to it.
Thanks for a fascinating article. I would love to get rid of the gas system. Heavier than air explosive gases in a watertight container is not a good idea though it seems that, for now, it isn’t there yet. Have you ever looked at fuel cells as an alternative means of putting AH into a battery?
Fuel cells may be appealing from a high-tech engineering standpoint, but – at least for the moment – they don’t work out economically for a cruiser. The main commercially available one of note, for yachts, is the EFOY direct methanol fuel cell. At $6,000 plus installation to make 8.8 amps @ 12 V (210 Ah/day), it’s a big up-front expense. Vendor-supplied methanol is another $25 per gallon. At 0.24 gal/kWh, that’s $6/kWh or $15.20 a day for ultrapure wood alcohol (yeah, the super toxic stuff). Are you willing to pay $18.50 every day for 5 years for those 210Ah?
I wrote an article for Cruising World about fuel cells, practical, every-day use models are just around the corner. I said that 20 years ago…;-)
Induction cooktops are veritably standard on all of the new power vessel builds I’m working on, in that application it makes sense from a safety perspective alone. On the under 65 foot models most are designed to operate off inverters, primarily so you don’t have to start a gen while underway, as the alternators can carry the load.
Very informative article, thanks.
Hi Steve,
Yes, no question in my mind that if I were doing a motorboat over say 45 feet I would be looking at Induction all the way. More in Part 2.
Hi Roger,
Yes, Colin took a look at fuel cells some years ago. https://www.morganscloud.com/2013/09/28/whats-new-in-alternative-energy/
Currently the problem with them is the very expensive and hard to source fuel. Also one commenter to the post, who seems well informed, suggested it may be dangerous.
My partner simply will not cook with gas. And when it’s embedded into the boat it comes with a bunch of practical, safety, and regulatory issues. Plus we we’re already using induction at home with a lot of success, so it was inevitable that it was going to be part of the mix for us.
In the end I’ve gone with a composite gas bottle mounted externally on the transom and a small de-mountable gas barbecue for grilling and baking (this is Australia after all). And then inside we’ve gotten rid of the oven and simplified down to an induction cooktop for regular use. These guys have some smart choices adapted to RV and Marine applications:
https://www.safiery.com/induction
Back up is a portable alcohol stove that we can also take onto the beach or travelling.
I agree totally with your numbers, and that fully relying on induction for all your cooking needs comes with real design issues that need working through. Looking forward to Part 2.
Hi Philip,
Thanks for the link. Now all we need is for Safiery to come up with one in gimbals with rails.
Hi Philip,
I have never personally known a boat where propane has caused a problem (though I know they exist and have seen the boat carcass of one).
I have personally known 2 boats where fires have started caused by using alcohol stoves. I believe a properly set up propane system with one or 2 sniffers/alarms (depending on the size of the boat) and a solenoid in the locker activated near the stove is very safe, perhaps safer than working with an alcohol stove, especially a portable one.
My best, Dick Stevenson, s/v Alchemy
Fair call Dick. I accept that gas detectors can change the game, but looking back on my industrial experience with them, I’m aware of just how hard it is to really achieve a system that has an availability level commensurate with the hazard here, and at a reasonable cost. And especially in a marine environment.
Having said that, gas stoves are not the only potential source of CO on a boat and detectors probably should be mandatory anyway. I have several horror stories about what I found in my wet exhaust shortly after purchase.
Hi Philip,
For almost any problem, early warning is well more than ½ the battle. And there are a handful of detectors I would make mandatory prior to a boat leaving the factory (high water, CO, smoke, and gas to name a few). (My guess is safety features do not sell boats.)
On my 40-foot boat I run 2 gas sniffers (2 separate bilges) with alarms 24/7 (minimal power usage) and test them regularly by shooting into the sniffer, gas from an unlit cigarette lighter/long match. I have never had a sniffer fail the test in 15+ years (not sure what your industrial experience has been). (Carry a spare sniffer as they die after 4-6 years or so: plug and play). The sniffers also get irregular testing when I am clumsy with volatiles of some sort which unfortunately has been known to happen.
Another safety feature is a solenoid cut-off in the propane locker activated near the stove with a bright red light indicating the gas is on line. This system has also never failed although I re-built the system a few years back and put the still working parts in storage.
I also have a gauge in line which after charging the system and turning off the valve at the tank will tell me whether there are leaks in the system.
The ante for errors in propane use is high so having redundancy in sniffing, regular testing, and some discipline in using is key.
The real pain is that there exists no standard fixtures for gas. I have been to 40-50 countries and more than a few times have resorted to a Stevenson tradition: work really hard at solving the problem, but at some point “throwing money at it” usually works.
My best, Dick Stevenson, s/v Alchemy
Hi Dick,
Great comment, I loved the “Stevenson tradition”.
Hi Dick,
Generally, I would agree with that. That said, Phyllis and I have had two very scary propane equipment failures (see further reading) that could easily have resulted in a big bang, so I do sympathize with those that won’t have propane. Also, I agree on alcohol, particularly the old pressurized ones, which were a menace.
John, your math looks “close enough” given that we’re working with first-level approximations and field measurements here. Sure, we could drill down into obsessive levels of detail with a 700-cell spreadsheet, but that wouldn’t really change the numbers by much, nor would it affect the overall conclusion.
Using propane as the baseline, it’s going to be very hard to beat that for overall cost and end-to-end efficiency with anything electric, if you need to create the electricity yourself. Keep in mind that moving energy around in one form is easy and cheap: you move propane with a tank and a hose, you move mechanical energy with a spinning shaft or a tensioned rope, you move electrical energy with a wire. Changing energy from one form to another is what’s expensive. Going from diesel fuel, to heat, to reciprocating motion, to rotary motion, to alternating current, to direct current, to a battery, back to direct current, to alternating current, to the induction cooker, to heat….. that is many more steps, requiring many more machines and costing much more money, than going straight from propane to heat.
Where induction cooking (and the requisite electric convection oven, if you want to bake as well) is a little easier to justify is if you engineer the entire boat, up front, around an all-electric design philosophy with a lot of renewable energy sources. This is the “high house load” scenario in which a large lithium battery bank and hybrid electric propulsion start to be worth considering. If you can afford that, and you want all the other comforts of home – the washing machine, the 55″ TV – then yes, it’s quite feasible to engineer a system that lets you get by with no propane, powering all the house electrical loads from that big battery and charging mainly from renewables, and then running a diesel generator for a brief spell every few days. It’ll be expensive, but if you’re rich enough, you don’t care.
Induction cooking makes even more sense if you spend a lot of time docked with shorepower. For a “floating cottage” boat or a day-sailing boat that’s at the marina 80% of the time, I’d absolutely recommend electric cooking, versus screwing around with propane.
Grafting it on to a long-range cruising boat that was never engineered with this level of electrical demand in mind is not something I’d be inclined to recommend, at least unless you’re an electrical engineer and make a hobby out of messing around with that sort of thing.
Hi Matt,
Thanks for the confirmation on the numbers.
One thing I find hard to get comfortable with is “then yes, it’s quite feasible to engineer a system that lets you get by with no propane, powering all the house electrical loads from that big battery and charging mainly from renewables”
Any time I do the numbers for most any real world usage profile, like I did above, I always end up with an impractical area of solar panels, and that’s just with induction, never mind electric drive, or even a washing machine etc. Some years ago an all solar boat with electric drive came through Halifax and it was indeed a very odd looking thing, and not really practical, even though it had been engineered from scratch for the job.
Done right, it looks something like a Dashew FPB 78. They carry 3.4 kW of solar panels; that’s about 15 kWh/day in the tropics.
Being a huge powerboat with few crew, relatively light electrical demand (for its size), and a near-unlimited budget makes the task relatively easy. There’s no good way to find space for a 16 square metre solar array on a more typically-sized cruising sailboat.
Hi Matt,
I agree, Steve’s system is great, he even manages to get some AC out of it. Of course a lot of what makes it work is that any time he is moving he is generating a ton of power off his main engine through two huge ElecTrodyne alternators to recharge his massive battery bank, so even in his case it’s not really true to say that he is powering off renewables that much, particularly since he and Linda are pretty restless when cruising, with a move every day or so.
Hi Matt,
you mentioned the scenario of being docked with shorepower a lot. Fits my situation, and I bought a portable induction plate very similar to John’s test setup a few years ago. Only use it when shore powered. I would not be without it!
Bringing water to boil with it is around 5 times faster than with propane.
Just saying that no need to make this an either/or choice. Just add a portable induction plate to complement the propane stove and get the best of both worlds 🙂
What might be a perfect cook stove for us, as country hopping sailors without a genset?
A diesel (it’s hard to beat the energy density of diesel) cook stove that uses glow plug ignition and fan induced draft technology. (One manufacturer is Wallis.) As opposed to a heavy cast iron diesel drip type stove popular with commercial fishermen – who wants to heat up hundreds of pounds of metal (and the cabin in the process) and wait an hour for the first cup of tea water? Not to mention vulnerability to back draft issues.
Sailing in Denmark and Germany the year before last we saw some of these fan blower type diesel cookers aboard neighbor boats. They were very fast cooking and odorless and we admired their clean design. They can be used in stormy conditions without back draft problems. If they had been a bit more affordable we might have converted on the spot!
We cook with propane, and it has been quite a problem to refill tanks internationally. Considering new bottles we’ve been forced to buy (only to discard soon after) and adapter fittings of various types (not to mention hours of taxi rides) it has been much more expensive and time consuming than we would have guessed.
Hi Pnl,
Unfortunately there really isn’t a “perfect cook stove”. Liquid fuel stoves, while sounding great in theory, at least in my experience, are a pain in the neck: https://www.morganscloud.com/2009/12/18/kerosene-paraffin-cooker/
That said, I have not tried the Wallis. One thing I would say is that the owners of diesel fuel stoves tend to see them through, shall we say, rose coloured glasses, so it will be important for you to really check them out before spending the money and taking on the complexities of a change.
For those interested, here is a link to one of Wallas’ cooking tops.
https://wallas.fi/index.php?id=54
I have owned one. For me, the Wallas system is decent for the occasional weekend use, but for extended cruising, I by a huge margin prefer cooking with propane.
Hi Petter,
That’s great to have an assessment from someone who has tried both, thanks.
We converted to Induction 5 years ago and haven’t regretted it for a second. Other advantages: more bench space, no condensation from the gas burning, and you don’t need a different gas bottle for every country you go to. But the best thing is we haven’t had that tired old conversation after rowing ashore: I can’t remember if I turned the gas bottles off…….. And as for going green, next time we fill up it will be with biodiesel.
We don’t go offshore, but I know a chap who’s preferred cruising is the arctic in his steel ketch. He swears by induction cooking also.
Hi Mark,
That’s interesting. I assume you have a generator given that you mention biodiesel?
That said, the debate on whether or not biodiesel is really green is a complex one. My guess is that given the efficiency differences detailed above, propane as a base fuel for cooking would still be less damaging than biodiesel simply because we will use less of it and it burns a lot cleaner.
I’m referring to the 100% vegie oil type bio-diesel. Also remember, induction is incredibly efficient. I would guess comparable with propane overall from go-to-whoa. It would be interesting to see a study on that. Incidentally our induction is a two hob plug-in type, flush mounted so you can put 4 pots on it if need be, which we never need to do. Also it only consumes a maximum of 1800w so cannot be overloaded. We have a portable propane barby, and can switch to ‘eat-to-live’ mode (referencing your “Cooking Options For Live-aboard Voyagers—Part 1, Electric” article) if needed. (Actually, our eat-to-live mode is pretty gourmet, just very simple, quick and delicious.)
Hi Mark,
See the post above for an analysis of just that. Bottom line, propane is about twice as efficient as as induction being supplied by a generator. And those numbers were checked and confirmed by two professional engineers with relevant knowledge. And even if burning bio diesel, there will be about twice as much carbon produced with induction/diesel. And finally, bio diesel is, I think, hard to get in most ports so most cruisers will end up burning crude derived diesel most of the time.
John, another way of looking at this is that a 6kg bottle of gas (not a big one) contains around 84kWh of energy, which translates to 7,000ah from a 12v battery system. That is almost 20 50% discharges of your battery bank.
Re the generator efficiency, the overall number of around 25% is reasonable, but most of the loss is in the combustion process. As I understand things, electricity generators are more than 90% efficient in turning power from a rotating shaft into electricity. Basic thermodynamics limits the the efficiency of the motor to circa 30%.
Hi Colin,
That’s interesting. The research I did came up with a lower efficiency for the generator and a higher one for the engine, but I think you may easily be right. Anyway, the good news is we come out at about the same overall number for the generator as a whole.
John, as someone who doesn’t have a generator, nor is willing to install one, I made similar, but way simpler calculations some time ago.
Assuming a single induction burner (~2kW) running for, say, 1 hour a day, means 2kWh of energy as the crudest approximation. No way I’m ever going to generate that with a reasonably sized solar array. End of consideration.
Hi Alex,
Smart move. Shows how vital it is to do the numbers!
You mentioned discussing the Voltage drop to 11.0 V… is that to come yet?
Somewhat off-topic but related since the high current draw of this and other AC cooking appliances is an issue:
I try very hard to not let my house voltage drop below 12.1 V. Is that an unnecessarily high threshold? I heard that some instruments and our Wallas heater do not tolerate voltages below 12.0 very well.
-evan
Hi Evan,
Good question and valid concern. I dig into it in Part 2.
Once you’re off the grid “belt and suspenders “ comes into your thinking. For cooking that means having two different ways to do it. Now commonly it means propane and diesel. Propane for the stove/oven and diesel for a Refleks, Dickerson, or similar and/or diesel to run a genset to achieve some form of electric cooking. We’ve carried a Q, a traditional propane stove/oven and a cheapo hot plate. If our electrical sources all fail (no refrigeration, no electricity for cooking) we’d do just fine. Like most carry two sets of food stores. One not dependent on refrigeration. My concern is if you go with electrical cooking in any form if you intend to be off the grid you still need a fall back. A barbecue is not functional in this service. Alcohol is a major PIA and has safety issues. Can see the practicality of induction on large power like Steve D is referring to as those vessels have two gensets or other systems to maintain electricity given they are dependent on it to function but for the mom and pop cruiser it’s just not practical. As you elegantly stated due to draw but also due to the practicalities of having redundancy that will serve for a long period of time.
Great article. I am a fanboy of induction as well for all the reasons you mention. I never seriously considered it for my boat because I have 1/2 the battery capacity that you do. Speaking of capacity (energy stored) I notice you wrote kW/h and W/hour in a couple places. Perhaps that was a typo, but the correct unit for energy is KWH ; watts = energy/time, so watts x time =energy. As a former physics teacher who railed against his students for this very frequent confusion, I couldn’t resist.
Hi Robert,
I just did a search on the post and could not find any use of “W/hour” also, as far as whether KWH or kW/h is correct I went off Wikipedia which is our editorial standard source here at AAC. Does not necessarily make it definitively right, but when running an operation like ours you have to go with an easily accessed standard.
The unit of energy, “watt-hour” or “kilowatt-hour”, is Wh or kWh.
Lowercase k, lowercase h.
Uppercase K is reserved for kelvin, i.e. temperature.
Uppercase H is for henry, i.e. electrical inductance.
kW/h would be a power ramp rate, i.e. change in power output as a function of time. A very useful quantity when dealing with a large power source, eg. a power plant or nuclear core.
KWH would be kelvin-watt-henrys which, as far as I can tell, reduces to kelvin/(seconds * amps^2), which usually points to “Don’t Drink And Derive”.
(/annoying-pedantic-physicist)
Matt,
“Don’t Drink And Derive”.
Made my day! 🙂
Hi Robert,
Woops, you are right. When fixing the other screw up I made, see the new update note in the article, I found the offending watt/hours and got rid of it.
Hi John,
My partner and I have been using induction at home for 10 years and on our sailboat for 6 years – albeit only when connected to shore power. We’ve kept the propane gimballed stove/oven and rail BBQ for “away meals” but have been debating getting rid of propane on our sailboat, much as you and others have been contemplating. I’ve been reluctant to do so, however, because of my gut instinct that it would cost us our battery bank due to constant deep discharges. Thanks for doing the numbers and I’ll be showing these to my partner shortly.
Another device that has made its way onto our sailboat is an “Instant Pot”, a great Canadian invention that is essentially a pressure cooker with its own heating source (110VAC). Unlike a traditional pressure cooker that sits on a stove top and must be monitored and adjusted, the Instant Pot has lots of smarts inside which allows for safe, unmonitored cooking at a fraction of the power consumption of stove top cooking. It’s extremely versatile and allows one to cook meals in minutes that would take hours on a stove top or in an oven. Besides regular cooking (stews, soups, roasts) it can be used to make rice, yoghurt, bake bread and – for those that like to make preserves or perform on-board surgeries – sterilize utensils! what we really like about the Instant Pot is that it allows cooking in areas other than the galley and because it is sealed when in use (other than the steam vent), it can’t spill its contents in rough weather. With an extension cord we could easily secure it in the cockpit while sailing and serve up a meal without running back and forth to the galley to check on things.
Once again, the problem is with the electrical consumption from our battery bank. Again, gut instincts and preliminary observations tell me it’s only going to work if you’ve got a sizeable Amp-hr capacity and batteries that can withstand constant deep drawdowns. That we don’t have. I’m suspecting, however, it will do a bit better than an induction cooktop and is safer and more versatile IMHO.
If you or any other readers use Instant Pots on board using your battery banks and have done the math, it would be great to share your findings with us too!
In the meantime I’ve got lots of other projects under way right now. Recently we purchased a 36′ steel, swing keel expedition sailboat at a great price but of course it needs lots of attention. I’ve got a busy 2 years ahead of me before we cast off for some long excursions.
Thanks
Rob Hellier
Hi Rob,
Funny you should mention Instant Pot, Phyllis just bought one for our cottage. Maybe at some point I will run it on our meter and see what the practicalities of using it on the boat are.
We have gone even more simple (although we have an electric grill and a Force 10). We cook a few meals with something called a Wonderbag, essentially a passive, insulated, fabric Crock Pot. It looks vaguely like a turban: bring the food to a prescribed degree of cooked on a stove or hot plate and put the pot in the bag, which is more or less a pumpkin-sized sleeping bag. Four or five hours later, the residual heat added at the front end has fully cooked the food. We do soups, stews and lasagna this way and avoid heating up the cabin and it is, as one would expect, quite easy on the propane usage. https://www.wonderbagworld.com/
The bonus? The warm Wonderbag is wonderful for sore backs!
We started using a small Insta Pot early this year, which we liked so much, we bought a larger air fryer model. At the same time, we bought a very nice electric hot water kettle.
I bought a couple Kill A Watt meters to see how much power is used by the Insta Pots and the electric kettle.
Oatmeal takes around .08 to .11 KWH. I make the oatmeal in the morning but I might not eat it for anywhere from 15 to 209 minutes after it is ready. The danged thing use very little power just sitting there staying warm.
Making rice in the small Insta Pot is around .07 KWH.
Quinoa in the small Insta Pot was .10 KHW.
The Insta Pot Air Fryer uses around .25 KHW for air frying, i.e., convection heating, at 400 degrees F for 10 minutes. Frying for 5 minutes at the same temperature is .15 KWH.
The hot water kettle very consistently uses .08 KWH to heat water to 95C.
We do have a small induction plate that I will measure the output some day. It is supposed to be a good unit but it heats unevenly. Though It did come in handy when our range died. Now it is used to roast coffee outside so as to not smoke up the house.
The Wonderbag sounds great!
I forgot to mention that we gave a 3 litre Instant Pot – 3 years ago – to our full time cruising friends when we helped them with a voyage to Martinique. At first they were a bit skeptical but when they had issues getting propane in the Caribbean, due to non matching fittings, they had no choice but to use their battery banks/inverter to power the Instant Pot. They have since reported that they now use it almost exclusively to make meals, with very little drawdown on the batteries. The propane gimballed stove is only used regularly to make the morning coffee. The 40′ Jeaneau does not have a particularly large house battery bank and they don’t have a genset. It does have about 350W of solar. So this real-life account does suggest that it is an efficient way to keep a crew happy and healthy!
Hi Robert,
That’s interesting, but given Dan’s numbers above I think it may also be that thy are not cooking a lot or are running the engine sometimes to charge.
Hi Dan,
Thanks for the numbers. A cursory view seems to indicate that there’s not a big power savings over induction from these things for anything like frying, which is as one would expect given that induction is about 90% efficient at heating food. That said, the savings seem to be good when doing low heat long duration stuff like rice which makes sense since there will be much less loss to the surrounding air.
I Pulled out the propane a few years back and installed a Wallis stovetop. It has performed flawlessly. Uses very small amount of diesel which comes from the main tank and provides some nice heat in the galley as well. It is a bit noisy though at start up. Installation very simple. We also explored induction at the time but could not imagine having to go with a gen set as well.
Regards
Hi Ed,
Thanks for that real world report, always the best kind. Can you share what the start up time is until it’s ready to boil a kettle, say? That’s always been a big problem with liquid fuel.
Also, what is the practicality of diesel for an oven. The kerro oven I have used was a horror and pretty much unusable.
John, am I missing something here? It looks to me as if the column ‘times a day’ has propagated ‘3 times’ all down the list of usages although it says ‘1’ in all but the ‘Tea’ line.
Hi Paul.
Yikes, you are right. That changes a lot. Thanks for catching it. Let me dig in and find out what else that changes. Will take a couple of hours.
I should also have said thanks for a well thought out piece. I am sourcing a standalone induction hob (like the one you pictured) for use when on shore power or for use with a pressure cooker which I think will reduce power consumption somewhat.
I should also have said thanks for a well thought out piece. I am sourcing a standalone induction hob (like the one you pictured) for use when on shore power or for use with a pressure cooker which I think will reduce power consumption somewhat / some of the time.
So maybe your daily usage is 124.81 amp/hours/day before applying Peukert Constant.
Still not realistic for most of us.
I just did a quick test with a small Breville countertop oven that use for 99% of our baking and a Kill-A-Watts that I had laying around.
To get to 350F, a bit less than 4 minutes at 1450W, (80Wh on the KAW display)
to keep it at 350 for 10 minutes, the oven cycles on and off but that was also 80Wh according to the KAW.
For 3 hours, 18×80+80 to warm up, 1520Wh, at 11V, 138 Amp hour. Your 155 estimate is pretty good.
Hi Mathieu,
Thanks for the confirmation. Will be useful for part 2.
We have come about this from the opposite direction, based on different numbers.
We started with the numbers and science around Climate Change. The evidence is overwhelming that we have to find ways to live that are sustainable. Among other things that means no more burning fossil fuels, none and starting now. If you start from the big picture then you look at it all differently.
So for me the wrong question is to ask how can I cook fossil fuel free and live the way I always have, with the cooking and diet habits that I have followed for many years. Instead, we need to adapt what we eat and how we cook it to fit what we can generate/store using renewable supplies.
In the long term this does include shore power as in most counties that is quite rapidly decarbonising driven by the economics (solar is now much the cheapest power source for electrical grids and there are multiple grid sized energy stores coming to market).
In the short term, and when cruising (both offshore and at anchor) it means cooking using what we can generate from solar, wind and water. Fortunately, there is a useful co-incidence. namely that we are being urged to make another significant cut in our carbon footprints by eating a lot less meat. Diets with less meat can also fit well with less cooking.
So on Vida we are only having electric cooking with two individual induction hobs, multi-cooker (electric pressure cooker) and microwave combi oven (when we head for warmer climates we will add a solar oven).
Over the last few years we have already been cutting our meat down, probably now less than two meals a month – and it is great for taste, health, cost and our carbon footprint.
This way cooking energy becomes like anything else you budget for. X is the Ampere Hours I have available, therefore we will eat Y. Exactly the same as I have x gallons of fuel therefore my range is X. If you are worried about running out of cooking energy then make sure you have plenty of supplies that don’t need to be cooked (such as Huel).
We can of course increase the budget and here I think you miss a key element which I think of as Active Renewable Energy. I believe that on cruising boats we need to move away from thinking about fixed solar panels. As you point out we can’t have enough on monohulls. But why do they all have to be fixed? At anchor I can have solar panels sticking out from the guardrails all the way round the boat. I can put them on top of the boom and I can tilt them all towards the sun for major efficiency gains. When we go sailing we “reef” them and stack them in the dinghy or in the guest cabin.
When we sail we will generate power through the regen of the electric motor (or for those still with diesel engines with a Watt and Sea generator).
When anchored in high winds we put up a wind generator.
If I do want to cook a roast chicken (we haven’t done so for a couple of years and don’t miss it at all) then plan ahead so that the battery bank is fully charged for that special event (of course to do this you do need a big lithium bank so you can use 90% of the capacity and have a fast draw without any problems).
It feels like you can’t see how fossil fuel free cooking can work because you are looking through the wrong end of the telescope 😉
Hi Dave,
There aren’t a lot of numbers and calculations in your comment to follow along, so I’ve tried to list at least major components necessary for your proposal.
A big lithium bank, large inverter, lots of easy-to-install solar panels with swiveling mounts, corresponding amount of solar chargers, wind generator, electric motor. One would need to actually run the numbers to see whether it’s even possible to generate enough energy with such set-up, but the component list alone sounds to my ears like money for A LOT of fossil-free denatured alcohol. If I had to guess, that’s decades worth of alcohol.
I’m left unconvinced that what you’re proposing is practical.
Hi Alex,
The beauty of approaching from this direction is that the calculations are not the deciding factor 🙂 Which isn’t to say we haven’t done them just that they start from intending to live with the available capacity.
Also we need to remember that the location makes all the difference. We are not kidding ourselves that we will be able to do this in Norway in the winter 🙂
Yes we have the basics in place. But we also have a few more years of refitting and weekend/holiday cruising before I retire in which to get the balances right based on real world use. We are confident that even now we have enough capacity for recharging to happen on the mooring between weekends.
We would have just about made it to launch this year but for being locked down with no access to the boat. Depending on how long the current lockdown continues we still hope to be in the water testing next year.
In terms of capacities we are starting with
– 860 watts of rigid solar panels
– 1680 AH of Lithium battery banks (a motor bank and a house bank with either able to charge the other)
– two 2,000 watt inverters connected to run together
– electric motor which should provide good regen when sailing
Financially, it helps if you start with a boat value that is reduced by the entire gas system being condemned, a diesel fuel system that needs replacing and a working diesel engine to sell.
Plus it helps if you are not planning AC, a freezer and will be using a hydrovane for steering.
Dave
Hi Dave,
I have to disagree that calculations aren’t the deciding factor. If you don’t do the calculations upfront, you may end up eating a lot of granola bars and peanut butter sandwiches 🙂
Now that you have clarified what you’re starting with, I understand that you can get to approximately right numbers by going overboard on the size and then adjusting on the go. That’s almost the same as doing the calculations, but empirically, instead of theoretically.
To be able to afford the kind of system you describe, I’d need to sell the working Perkins 4.236 and a kidney, probably 🙂 And then I’d end up without a reliable backup propulsion option or backup kidney.
As I say we have been doing our own calculations both theoretically and with a digital electrical socket consumption use. Just not had the time to write them up, and for the moment we are stuck in the boatyard using their shorepower anyway.
The economics are easier when either doing a new build or when you can only afford a fixer upper boat where
– the gas bottle, valves, pipes and cooker are all condemned in the survey
– you will have to remove the working engine in order to replace the entire fuel supply system, the califorier, and the cuttlas bearing, and either the stuffing box or the propeller shaft.
– none of the lead acid batteries will hold any charge
– the shorepower system, the paraffin heating and the fridge are all also condemned.
So at the moment I’d agree that we are not at the point where everyone should be ripping out working systems. But we are where it makes sense for new builds and for major refits – define major as you wish 😉
Dave
Hi Alex,
I agree, calculations are always a deciding factor if we want good outcomes, rather than nasty surprises.
Hi Dave,
I need to point out that you have not yet got out there live aboard long term voyaging and would be fairly sure that many things will change when you do that. For example the power generated by your 860 watts of solar over a full day of bright sunshine would will be used up in about 10 minutes by your electric drive, assuming 20 hp, or 20 minutes assuming 10hp.
Of course regen will help, but the actual amounts are far less than many assume and the drag is substantial too.
You maybe able to live with that reality, but it’s not a good idea to be unaware of it, or promote your solution without making others aware.
John,
I’ve consistently made it clear that we are still at the refitting stage. I’ve not hidden any of the challenges.
Our batteries should give us between 60 and 90 minutes of full throttle. Around 40 nm at slow speeds. Obviously we can’t do that everyday but we want to sail not motor.
As for regen drag, yes but we are hoping to upgrade to a Bruntons new ecostar autoprop to give the most options.
Hi Dave,
That’s a laudable way to look at it, but unfortunatly I fear that few people will follow your example. Also note that I wrote:
So I would say that I did cover off that option.
It’s also important to note that capital costs of your approach are high enough to be out of reach for many cruisers. More on that in the Part 2.
John,
We prefer to see it as realistic or responsible rather than laudable 😉
As for the festooning, it is a rather negative word 🙂 Having a setup that varies according to where you are and the weather seems seamanlike to us. We won’t have a huge solar arch when caught in an Atlantic gale. But we will be able to protect the mainsail stackpack from the sun while at anchor.
The economics are moving fast in this direction. Solar panel and Lithium battery prices have plumeted in recent years. By going 100% fossil fuel free we gain flexibility in being able to choose whether we prepare to motor or cook with the power we capture and store. Key to the equations is an investment now for big reductions in running costs.
We hadn’t originally planned to go 100% fossil fuel free, but when we started pricing the time and money we would have needed to spend on the diesel engine it made sense for us. The biggest gains are when it isn’t just cooking but getting rid of the engine as well (all the batteries, imverters and motor fit in the old engine compartment creating lots of space where the fuel tanks were). The you also get the beauty of no diesel maintenance, no diesel fumes and smell. As we were removing the headlining (helping it fall off would be more accurate) it was shocking how far away from the engine room a black sticky exhaust residue went (including the galley, chart table and aft cabin). That can’t have been good for people’s health or comfort!
I agree that this does require a significant cost outlay. Yet on a new boat the difference is getting very small as a purchase % with significant reductions in running costs. With older boats it only works for bigger refits. However, there are a lot of boats out there with fuel systems that are unsuitable for reliable use in the age of diesel bug (just look at how many hours of engine maintenance there are in youtube videos). On our Rival 38 we had long lengths of inaccessible, corroded copper pipe and broken valves. Also tanks with no way to inspect or clean.
When it comes to costs it is important to consider not just the capital cost of switching but also
– the cost to the planet of not switching
– the true costs of staying with fossil fuels (in money, safety and comfort)
– the running cost savings (time and money)
Dave
Hi Dave,
That’s all true, but we must not lose sight of the fact that it only works for very limited usage profiles: https://www.morganscloud.com/2013/04/23/electric-or-diesel-electric-drives-for-voyaging-boats/
Those interested can use this calculator to determine whether or not their usage profile, or one they are willing to adopt, will work: https://www.morganscloud.com/2014/04/13/real-numbers-for-electric-and-diesel-electric-drives/
Also, given the costs of an all electric boat, and ongoing maintenance I very much doubt that there will ever be a payback, or even close, in saved diesel and maintenance on diesel engines.
Don’t get me wrong, I’m not trying to discourage anyone, but on the other hand the green industry and a move away from fossil fuels, which I’m a huge believer in, is not served by only putting forward the positives without looking at costs and required usage profile that must be adopted.
We have run these numbers and they don’t work for our 40 foot steel cutter. We have a motorsailer; the reality is in the name. However, knowing we wanted to do a circ and being mindful of ecological considerations, we have extensive renewables capacity (wind generator and fixed panels) and a large (1,200 Ah) lead-acid house bank. However, our strategy was to “pay it forward”; despite having the income to afford a car, we and my wife have declined to buy on for the entirety of our adult lives. I literally cannot burn even a significant fraction of the diesel I would use on this boat compared to that which I would have burned owning a car and commuting a typical distance. This decision to not own a car has influenced many decisions: where to live (within biking distance of a yacht club!); how to obtain materials for house and boat (bike trailers or paid deliveries); and our present situation, a 30 minute cycle to our boatyard and a (new record!) one hour, five minute cycle to the nearest grocery store in Chester, Nova Scotia.
And yet we are content, and, I dare say, a great deal fitter than had we had a car during the 40 years of adulthood prior to our attempt at Attainable Adventure Cruising. In fact, I credit the decision to not own a car to enable people of our means to afford our boat in the first place, my sore legs notwithstanding.
The above is not a critique, but more an observation that there are more than one way to lower one’s carbon footprint, some of which may be not following the expected path in the first place.
Marc,
I agree we all face different challenges.
One of the reasons why we are focused on retirement is that we don’t get to choose where we live and we live in a house provided by work. So we don’t get much control over a lot of factors relating to our carbon footprint at the moment. Which is one reason why it is more important in our future plans.
I’ve managed to mostly get around for work by bike in most places we have been, in part with a Bullitt Cargobike. Sadly this year I’ve found the lockdowns here have caused more dangerous driving which has made me feel less safe which has pretty much stopped my riding for pleasure.
Hi Dave,
I sympathize on the bike issue. I stopped riding mine and went to sliding seat rowing after a local deliberately drove me off the road into a ditch because I was slowing him down on a corner.
Hi Marc,
I totally agree. The bottom line is that how green we are is a lot more about how much we do and don’t drive and fly than anything we can do on our boats. It just drives me up the wall when cruisers fit a few solar panels to their boats and claim to be green, and then turn up at the marina in a half ton truck, or fly back and forth from their boat five times a year.
I have been meaning to write a piece about this…must get around to it.
Dave, very much understood. My last “office” job was in 1999 and not everyone is cut out for freelance. But my skills are portable and I can work from the boat. What I gave up in a steady paycheque and pension I gained in time, but that’s not possible for many people in many professions/jobs. Where we would appear to agree is in how, once you start looking critically at the Western “energy spend” is that there are a lot of ways to either reduce it or direct it toward renewables and away from fossil fuels, which, due to cost of manufacture, may or may not make sense. Boats are good “test beds” in this regard, because so many of the inputs are owner-controllable and selectable, and are more directly measured than in a typical home, in which half the appliances may be drawing amps even when “off”.
So I applaud your goals here, but agree with others that the numbers tell the full story as to the reality of the convenience vs. purity equation! By the way, we have a Bogart Engineering Pentametric device to measure amps in/out/created/spent in several different combos. It’s allowed us for the first time to create an actual energy budget, including what can stay on for weeks vs. what draws heavily. Don’t let the engineer-written manual deter you.
John, aside from flights to RYA courses in 2013 and 2014, I hadn’t been on a commercial jet since 1995 and a cycling trip across Ireland. There are times I wish I had a car, absolutely, especially this deep in Nova Scotia with winter coming on, but we chose the car-free life with the goal of having the boat life sooner. I also agree with the observation that seeing the crew cab pickups pull up to the solar panel covered sailboats demonstrates a touch of cognitive dissonance, but so does most human behaviour when considered objectively. This may include the whiz-bang ways we can make tea in the mornings.
As for biking, while I have had every driver to date locally give me a wide berth, I also run into the gravel if I am approaching a hilltop curve and the driver behind me can’t veer out (or shouldn’t) over the double line. A good deterrent to this is to mount either a fake or a real GoPro or equivalent camera facing backward on one’s helmet and placing a small placard on the rear fender that says “SMILE FOR MY CAMERA!”. Only a truly crazy driver would attempt to clip you seeing that. But I digress.
Hi All,
The subject of how to make things better for the environment is obviously important but it can be trickier to figure out than it sounds. Like figuring out whether induction cooking works on a boat from a power source standpoint, you need to run the numbers to see the actual impact. By this, I mean doing a full life-cycle analysis which means looking at the total carbon (it is worthwhile to look at other pollutants, deforestations, water, etc but I am sticking to greenhouse gases for this one) footprint of the solution chosen for a specific amount of time and making sure that you correct for replacement intervals and such.
As an example, making solar panels is surprisingly energy intensive. I have not kept up with where it stands right now but the rule of thumb a decade or two ago was that it took around 4 years to generate the equivalent amount of energy as it took to make them in the first place when used in the average climate of the US. Given that they have an expected life on the order of 20 years, this makes sense provided that you use the output. However, if you have an off-grid house and size the system for the absolute worst conditions, you can end up with quite a significant carbon footprint due to overcapacity (unless you know everything about the energy sources in manufacturing). Strangely enough, your lifecycle analysis can improve in certain situations if you scale back on the panels and include a small generator that runs very occasionally (this ignores all the issues with having a generator that doesn’t start except a few times a year). For this same reason of the embodied energy in the panels, grid tied systems are preferred over off-grid solar installations as panels are not used at full potential for a lot of their life in an off-grid application. From a purely life cycle analysis standpoint, short of full time cruisers most boats would do better to recharge in marinas and not have solar. Of course, many of us don’t sail to visit marinas and solar can be so great for quality of life that we choose it anyways.
You can make a few generalizations and one is that in general, electrification tends to be better. Even using electricity produced by dirtier fuels, powerplants are much more efficient and as they are point sources, they are easier to put emissions controls technologies on. However, where you really need to watch it is when you have something where the embodied energy is high relative to the energy in the operational portion of the life and also you have to watch end of life issues. The other important thing is that we should of course put our efforts to where we can get more return as we live in a time and money constrained world.
Eric
Good points but one of the problems is that the current norms are often taken for granted. No point in doing a full lifecyle costing for the solar panels if you don’t do it for the propane systems or for the diesel engines and gensets.
Oh and at least in the UK and with boats in the size range we have (38foot) I don’t think gensets are very common, so actually we see lots of charging batteries from the main diesel engine with the original weak alternator running at very inefficient loads.
For ourselves we are expecting that in a few circumstances we may well need a small generator so that we can go to more northern latitudes; through the European Canals (it is the stretches where due to our draft we would need to go up a main rivers, like the Rhone, against the current that we couldn’t do without a generator); possibly the Panama canal. But we are hanging out for the next versions of models that put out 48 volts DC.
What I do think is that we will see a lot more hybrid systems in yachts in the future so that you can always run a diesel at maximum efficiency. Also as battery tech continues to improve we will see more and more yachts that are not used for ocean crossings/long term live aboard use as all electric with charging in their marinas. Even seeing it already with safety boat RIBs from RS Sailing.
Hi Dave,
I agree completely that to do a lifecycle analysis, you have to look at all the different options just like doing an opportunity cost so you need to do one of propane and the other alternative too. And you are also right that this is unfortunately not done enough. But the importance of the analysis is still there in that you learn what is in fact best but also you often learn how to do optimization. For example, you may learn how many panels are really appropriate or that if you change your sailing schedule slightly to better align with sun or to sail in the windless areas in the winter if you are diesel powered or whatever, you can end up with surprisingly big gains in whatever metric you are using.
I am not going to engage on the different propulsion alternatives on this post but would be happy to discuss them more on one of the posts specifically for them. In working on the model of propulsion alternatives, I tried to make sure that I gave as much of an apples to apples comparison as possible by having the inputs be speed and distance for the boat. As I don’t see many use cases where a straight electric is feasible and very few where a hybrid burns less fuel, I never got to the point of including lifecycle analysis but it would be interesting to add. I recognize that unfortunately I don’t live anywhere near a perfect lifestyle from an environmental standpoint but as I see more proper analysis, I try to improve while also still enjoying myself (the example of meat that you gave somewhere in the comments is a great one, once I saw the numbers on that, I significantly changed some behaviors around it so that I get to enjoy it sometimes but don’t just eat it as I need to eat something).
Eric
I wasn’t sure whether it was helpful to start commenting on the spreadsheet post that John linked to as it is 6 years old and the last comment 3 years ago.
It seems that the assumptions are pretty hard wired in and don’t fit with our expectations (eg Uma would be most like our expectations for motoring rather than expecting to motor for hundreds of miles on a passage or arrive at shore power with fully depleted batteries).
For the panels and overall capacity balancing we have the advantage of time. We are building up towards live aboard cruising in 3 or 4 years time. So we have started small with what we know we can easily fit (and realisitically leave up most of the time). As we get better, real numbers, we can scale it up.
One of the challenges for us is that the most common solar panel location (aft solar arch) is tricky on our Rival 38 Centre Cockpit with ketch rig due to the narrow stern and mizzen boom. So as far as aft space is concerned we are prioritising the hydrovane at the moment but even that needs to wait until we have the rig back up (got delayed by COIVID) we are wary of going too much by measurements from the original plans (especially as they as definitely wrong in some places).
Hi Dave,
The running the diesel at max efficiency so hybrid is better than diesel argument has been proven to be wrong in most usage scenarios on yachts. In fact Nigel Calder trashed several million euros of the EU’s money to prove that a properly sized diesel engine will always use less fuel than a hybrid for any scenario that has all but very short periods of continues operation. You can experiment with real numbers to see where the break points are on the spreadsheet, which Eric built: https://www.morganscloud.com/2014/04/13/real-numbers-for-electric-and-diesel-electric-drives/
Understand, I’m are not against any of this technology, and in fact am all for anything that will help slow climate change, but I do want to see real analysis backed up by real engineering, not unsubstantiated claims with no numbers postulated in YouTube videos.
John,
Yeah I was assuming being at the minimal end of the hybrid where you have lots of solar, a big battery bank, slow down and only need to run the generator a short time after you have failed to recharge enough with solar.
My understanding was that running a diesel engine to charge batteries with the standard alternator was where the biggest inefficiency was. I agree adding extra, better alternators makes a big difference.
John,
I’m careful to make it clear we are not yet voyaging and of course that needs to be taken account of. However, we do have a son who is an electrical engineer who has been through everything with us and my wife used to be a civil engineer so is used to calculations. I preferred to write software rather than work things out myself ?
I don’t believe I’m only putting forward positives and I’m making clear that there are implications on the whole of life.
Dave
As for costs. Everything depends on what you see as normal. We’ve seen some who have itemised their costs where diesel related expenses come to about 1/3 of their annual budget, others who spend very little.
Personally our first priority is to live as sustainably as possible. If that means that once we are living aboard we can’t go as far or as fast then that is no problem. We wouldn’t be considering live aboard cruising if we couldn’t meet at least the recommended 60% reduction in our carbon footprint this decade (and we intend to be there by halfway through). That is despite starting at a relatively low level.
This is at the root of our approach. We are trying to start with the aim of as low as possible carbon footprint rather than with particular lifestyle that we want to achieve. We think that the evidence is overwhelming, Jimmy Cornels recent writing about changes in round the world sailing support that as does everything about ice levels.
We shall see about the maintenance. At least I don’t have to learn about stinky diesel or blocked toilets.
Hi Dave,
That’s fine, as I said before I admire your commitment. However, it’s also my job to make sure our readers are as well informed about consequences and cost, and the tools we have to investigate that.
Hi John,
Just out of interest, you got me thinking how efficient or not it is to boil water with induction cooking. Assuming you are going from 20-100C (80C delta), 4 cups of water (946g), 1 calorie to raise 1g of water 1C, and 1 calorie = 4.184J, then you find that the energy required is 946*80*4.184 = 316645 J. Converting this to Wh, you get 88 Wh. If we then use your numbers, we get 129 Wh. This means that the thermal efficiency of induction cooking (ignoring batteries, charging, energy generation, etc) is not quite 70% which isn’t terrible. Of course, heating things is one of the easiest things to do in an efficient way but still, this is encouraging overall while also meaning that there won’t be a game changing efficiency improvement in cooking technology.
Regarding the rest of your numbers, like Matt said they should be good enough for this exercise. Most diesels in gensets are going to be closer to 30% overall efficiency but the generators that they spin should also hopefully be better than a basic alternator and yield 80% or maybe even better efficiency. The net efficiency is basically unchanged from your numbers.
This post really illustrates how critical these basic calcs can be. It seems that every forum about wanting to convert to electric propulsion or something like that starts with the assumption that slapping a few solar panels on will handle all loads. I had never run the numbers for cooking but now I know that is one more than I can ignore until there is at least an order of magnitude change in some technology (and it won’t be solar output per unit area as that would require more than 100% efficiency).
Eric
Eric,
I hope that I have been very clear in what I have written here that I do not believe that “slapping a few solar panels on will handle all loads”. Also there are a number of long term live aboard cruisers with solar charged electric motors (and seem to be adding more electric cooking appliances over time) who have been doing Atlantic crossings. Sailing Uma are in Norway with their video timelag at the moment. Rigging Doctor heading back to the US from the Med. Beau and Brandy have been around the Bahamas and Carribean for a few years.
I think fair to say all of these are low budget, choosing electric motors and then making it work within the limitations of what they can generate and store.
Oh and if you want game changing energy efficiency and live in a warm part of the world cherckout solar ovens such as the ones from GoSun 🙂
Dave,
As we’re discussing induction cooking here, it should be noted that both Sailing Uma and Rigging Doctor use alcohol cookers/stoves.
They also use electric kettles and microwaves.
Delos use induction hobs.
Uma only has 480 watts of solar. Rigging Doctor even less (and still lead acid batteries).
True, but that’s beside the point that they don’t use induction hobs for cooking, powered by batteries.
Delos very much has a diesel engine and a genset, so it’s not exactly the greenest boat around, as much as I admire them.
Alex,
Yes Delos has both diesel and genset. However, they did a detailed video after a year with the Lithium batteries and induction cooking. Their generator usage had plummeted. Of course now that they have reduced their solar capacity to fit the internet dome it may have changed a bit. They also run multiple fridges and freezers.
Hi Dave,
I’m aware of their claims and have watched the videos, but would like to see real hard and credible numbers including generator and main engine hours. Point being that all of these people are making unsubstantiated claims with no numbers.
Dave,
I just want give a fair consideration to practicalities of induction cooking on a boat. I’ve just reviewed that video and I don’t think they’ve mentioned their generator usage plummeting. It’s not even relevant to our discussion, IMO. Delos is a very energy-intensive boat and they just run the generator when they need to charge. You cannot use them as a practical example of the kind of system you’re installing on your boat.
John and Alex,
As soon as we launch I’ll be very happy to share any and all hard numbers that you want so that together we can get to a realistic view of what it looks like when you scale your use for cooking, domestic, navigation and motoring around what you can generate renewably in the UK.
I’ve looked at the spreadsheet John linked to. The numbers and assumptions are so different from where we have started from that I’m not sure if I can make much use of it. Plus Imperial measurements do my head in 🙂 Also prices etc have changed so much since 2014, can you imagine buying 300AH 12volt Lithium batteries then?
> and it won’t be solar output per unit area
Hi Eric,
just to underscore your point, I think it’s worth mentioning, that single-layer solar panels are already ~75% efficient, relatively to the theoretical maximum (https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limit). I had some friends get all disappointed at me when I mentioned that they shouldn’t expect game-changing efficiency breakthroughs in solar technology. As far as I understand, there’s no breakthrough to be expected from battery technologies with regards to energy density either.
Hi Alex,
I did not know that we were so close to best efficiency on solar. That’s disappointing in that I hoped we could raise efficiency from the current best of ~24% to something much better. That said, the linked article did seem to hold out some hope that we could do better with different technology, although I have to admit it was a long way above my pay grade.
I recently read some progress on several different technologies towards multi-layer solar but a while from the market yet.
Solar PV at η=25-35% is more a question of cost than of technical feasibility. Solar PV at η=35%-45% is a question of both cost and time-to-market. Triple junction cells based on the InGaP / InGaAs / Ge structure are available today…. just be prepared to pay 100 times more per watt than you do for cheap polycrystalline silicon. It’s pretty hard to justify unless you’re paying $10,000 a kilogram to fly them into orbit.
Alex is right; we now have a pretty good idea how to get within a stone’s throw of theoretical limits, and the absolute best we’ll ever get is about 2x the power per square metre of what you buy off-the-shelf for a cruising boat today. Also, the incentives to bump efficiency incrementally higher are not nearly as strong as the incentives to bump $/watt lower, so that’s where most of the commercial focus is.
At least we have a great timeline of reducing costs which shows no sign of ending ?
Hi Matt,
Thanks for the fill on that, and a good point on where the incentives will lead us, I had not thought of that.
Hi Eric,
That will be really useful for part 2, thanks. The googling I did indicated 90%, but that was sites selling induction, so I tend to like your number a lot more since I’m guessing that the 90% was a perfect world number missing things like radiation and conduction losses.
Hi John,
I suspect that the discrepancy is related to a few items. Some of this might be stuff like special induction cookware, insulating what is being heated, etc and then there is of course the marketing round up that sometimes defies mathematical rules. I also suspect that some of the difference could be due to measurement method. You went to a boil which means you have put in some energy that turns some of the liquid to gas without actually changing the temperature and it may be that they are measuring something more like 20-90C. I was curious so quickly looked at the numbers. The latent heat of water is 2260 kJ/kg which converts to .628 Wh/g. With 946g of water, that means it takes 590Wh of energy to change phase making all of the liquid into gas as compared to 88Wh of energy to get to 100C. As you rightly point out, this phase change takes far more energy than just heating water to a higher temp does.
From a real world standpoint, most people go until the water is boiling and hold it there so what you measured is a realistic energy consumption. If we were to compare efficiencies across technologies, then we would need to make sure we compare apples to apples. It is also interesting to think about whether it makes any sense to try to not spend too much energy holding a rolling boil but that doesn’t affect the overall conclusion of the article because I would think at best you might get 10 or 20% back (and not being a good cook, I have no idea what other things this would affect).
Eric
Hi Eric,
A great analysis, and good to hear that this does not materially change things.
On the cooking side, as an enthusiastic and good cook I can provide the fill that trying to cook with low temperatures, while doable, does not yield the good results that high heat does. For example pasta not cooked in a LOT of water and at a rolling boil is sticky and gross. And meat cooked too slowly is dry and grey—yuck. So in fact a good cook would use a great deal more power than I postulated in my spreadsheet. Those that doubt this should visit a good professional kitchen and watch the cooks on the line and the high temps they use. Alternatively, read anything the late Anthony Bourdain or Heat by Bill Buford.
This even applies for vegetarians. For example, stir fry at low temperature produces soggy under done vegetables that are inedible. And tofu needs a lot of heat to get the water out of it so it’s not gross. (We eat vegetarian at least once a week.)
So, yes, if you want to live on soggy veg and white rice (black rice takes a long time so a lot more power) you can reduce the numbers, but that’s the trade off that anyone who likes good food will not make, or not for long.
Before dismissing diesel as a fuel source look at this site https://wallas.fi/#
We started with a Taylors Paraffin stove but because of the flare ups moved onto to a Wallas hob which has become more reliable. Both Paraffin and diesel are safer than Gas. With Wallas one can have a separate fuel tank rather than run off the main tank. The website gives details of consumption of both fuel and electricity of the various hobs and ovens. Yes one needs electricity.
Fumes are not an issue as they go out the chimney and what surplus heat there is, is a dry heat..no water vapour to condense and an ungimballed hob can also turn into a heater with the correct lid.
How long to boil a kettle? There is an expression that “a watched pot never boils” but if one is preparing say porridge (oatmeal) laying out the cutlery and plates for breakfast it will soon come to the boil and the porridge on the slow side will not burn in the pan. For a quick boil then use an inverter powered, if at sea and not on shore power, camping kettle of no more than say 0.5/0.85l and one can boil less.
Oh yes the hob is just like an induction one..clean flat ceramic.
We do not have the oven.
Fair winds to all
Hi Albert,
Thanks for the link, I will check it out, and for the real world experience.
In part 2 I’d like to request using Watts (and kWh) rather than Amps (and AH) as then no conversions are needed for battery banks that are not 12 volt, it also works for the AC
By the way we have found the two free books from Victron really useful (Wiring Unlimited and Power Unlimited). Also of course Nigel Calder’s tome.
Hi Dave,
On a personal basis I would agree with you, but as a technical writer trying to make complex stuff as clear as possible I need to take into account the background of the majority of my audience, which is 12 volts and amp hours. For example, if I write “I have a 800 amp hour battery bank at 12 volts” most yachties have a good feel for the size and capacity of the bank and can relate that to loads and charging devices they are familiar with. But if I write “I have a 9.6 kW/h battery bank” most people will have no idea what that translates into in the real world and few will know how to convert back to amp hours.
And yes, I agree Victron’s stuff is great, I’m a huge fan and often refer to it.
Hi all,
Speaking of Victron… and green…
And, perhaps, another reason to buy Victron beyond its quality is (I have been told recently) that they are totally renewable/solar which, for a large manufacturing concern, is very impressive (using their own products/design).
I hope this gets verified, and if verified, gets passed around as an inspiration to other manufacturers and as further incentive to use their products.
My best, Dick Stevenson, s/v Alchemy
John,
Can you give a measured volume for the water you heated. That seems slow compared to what we find with our induction hob.
Thanks
Hi Dave,
I give the volume in the article.
Ah, I hadn’t realised “cup” was a specific measurement. So I looked to converting it to Millilitres. Turns out there are 3 different cup measurements: US Cup, US Legal Cup and Imperial Cup and they are quite different.
So which did you use?
Hi Dave,
Another part of good technical writing for the non technical is not being too pedantic. Note that I freely admitted that I might be 20% out either way.
But even if I am, don’t worry about it. Three professional engineers, two of them with specialized knowledge of the area of discussion, have confirmed that my numbers are close enough for sensible decision making. That said, it was a standard liquid cup measure that you will find in any north American kitchen, or boat galley.
I had been investigating the use of induction cooking aboard and did some testing using the $20 kwh/hr meters. I don’t have the numbers handy, but noticed a significant reduction in energy use by:
1. Using insulating layers (towels) around the cookware, which only induction allows, and
2. Realizing I don’t need boiling water for many cooking activities. 190-200 F water for soups or pasta works just as well as boiling water. Works for teas, also, though I expect many purists will disagree. (The induction plate I was using had settings for maintaining sub-boiling temps.)
I’m not aware of any induction specific, insulated cookware, has anyone seen any?
Hi Steven,
That makes sense. As I say in the article, it’s changing the state of water to steam (boiling) that’s so energy intensive.
I know it does not cover a boats entire cooking needs – but have you considered an InstaPot. These are electric pressure cookers – and use relatively little power because the element is mostly turned off when brought up to power.
I use one at home but plan on adding the smallest sized instapot to my boat, which uses 700W @ 220v. I like redundancy and more ways of doing things so I have a Taylors parafin cooker and will then have an instapot as well. One way or another, I get to eat – and no gas..
https://www.youtube.com/results?search_query=rv+instapot+power+consumption
Hi Richard,
See further up the thread, but the key point is that if it does not cover all cooking needs then it’s really not relevant (although maybe a good idea) since it does not replace propane. Probably good in your case, particularly because slow cooking on paraffin is near impossible, although I have not done any numbers.
Pff I am inspired and exhausted when reading this thread. Thank you all. I want only to add that on our Outremer 45 with the usual specs we have since the start of this year a EcoFlow Delta (https://www.nytimes.com/wirecutter/reviews/best-portable-power-stations/) which gives extra flexibility on energy choices. We use our Crockpot, inductionplate and Panasonic bread baker preferably on the Delta and charge it when possible with – excess energy from – solar, hydrogen and alternators when motoring. The Delta is also now the main source for charging computers and iPads, as an extra outlet in the cockpit or where ever.The exact measurement of energy used makes painfully clear what the demand is from induction.
The crockpot is far better than a standard pressurecooker on induction or gas, its handling is top. We have never used the standard pressure cooker since.
Hi Robert,
The EcoFlow is indeed a cool product—I own one like it to power our portable fridge in the car on road trips, overnight when the engine is not running. That said, it’s not really relevant to the discussion here since it does not solve the problem of where the required power is generated. Or to look at it another way, adding the ecoflow has just increased you battery bank size. A good thing, but a different issue that needs to be measured on a cost per amp/hr basis, where I’m guessing it will fall down against increasing the boat’s bank size.
Hi Robert,
I got interested so did some simple calculations: The EcoFlow Delta 1300 is has a 1.26 kW/h capacity, which converts to 105 amp hours at 12 volts and costs $1900.
A good quality AGM battery of 210 amps hours (correcting for reduced usable power from a lead acid battery) costs about $600 and therefore on a cost per amp hour basis the Delta is 3 times more. Of course the Delta is a lot smaller and lighter, so that’s a benefit.
Loads of interesting comments here. We have converted our galley to electric in spring, we live on board permanently, on anchor when we can but marina rats in winter in northern Europe. We have considered a Wallas but did not want any more holes in the boat so went for a Kenyon induction top and a Steba electric oven. We have a 440Ah battery bank at 24V (Victron Gel batteries) and ~900W of solar plus a 350W wind gen. In summer (up to around end of September) we did not need the GenSet at all for daily cooking, baking bread and so on. We even ran the hot water cylinder most days off the power we generated. We will replace the Gel batteries with Lithium and add two more solar panels now that we are docked for a while. For us it works very well, one less thing to worry about, no downsides in terms of usability or reliability. We will also upgrade our second alternator to reduce the hours of the Genset even further for the time where we don’t have enough sun.
Hi Lenz,
Thanks for sharing. Your account seems to confirm John’s estimations spot-on.
Can you share the size of your boat and where did you place the solar panels?
The install is on a 52ft Amel Super Maramu. Most panels are flex panels on the bimini we made that covers the cockpit and one larger panel on an aft arch. That means most panels are not ideally angled and a typical wattage we get on a sunny day is around 500-600W at 24V
Hi Lenz,
That’s interesting. The Amels are amenable to larger solar arrays because all the sail handling is automated so obstruction of rig handling is less of an issue. That said, I would want a Bimini top holding that many panels to be massively built since the presence of the panels is going to make it difficult (impossible?) to strike with really heavy weather coming. This can be a particularly scary problem at sea.
Hi Lenz,
That’s interesting, but that’s a size of solar array that I would not be comfortable with even on my 56 foot boat, and also I’m a wind generator hater (windage and noise) so it would not work for me and not something I would recommend, except those with very large boats, or maybe motorboats where the problem of large solar arrays getting in the way of efficiently handling the sails goes away.
The Bimini on an Amel is a direct extension of the fixed dodger, very sturdy and we never take it down, it has been in 50kt+ winds with no issues. Having said that, everything can be taken apart if needed, about half an hours job last time we did. If i don’t have that half hour I have serious other issues 🙂
On the wind gen, we have a Superwind on the mizzen mast above the radar dome. No noise, just power … but i know, once made up ones mind on wind gens it is impossible to change 🙂
Hi Lenz,
That sounds good. I see some awful flimsy Bimini tops covered in solar panels.
Hi John,
There has been some cool innovation in lightweight flexible solar panels in the last 5 years. We now have four of these new rectangular 145W panels mounted on our new three bow (2 panel Bimini):
https://www.enertecmarinesystems.com/product-category/marine-solar-wind-power/flexible-solar/
These solar panels have each been edge sewn with double vinyl along their long sides. The vinyl then has stainless grommet holes, four per side, and the Bimini canvass has new screw in “stayput” fasteners like these ones:
https://www.sailrite.com/Stayput-Canvas-to-Canvas-Fastener-Black
These self-seal against water ingress and are mainly concealed from below in the canvass bow pockets. These fasteners stay in place and the solar panels clip onto the Bimini top, two per panel. The solar panels have quick release waterproof electrical connections.
All this means I can now isolate the solar supply side from the solar controller, then unclip each panel (about 30 seconds for each) and fold/stow the Bimini away in its canvas cover for storm/winter mode. The series connector cables stay in canvas channels sewn onto the Bimini.
Like Lenz experience I have just come back from the boat, as Auckland has just been blasted with a frontal passage with 50 knot gusts and heavy rain. So I went to check on the new Bimini. The vinyl edging seems to seal the edges aerodynamically and there is no hint of the panels trying to lift or flap, in fact the opposite. The Bimini itself with strong 30mm bows stayed remarkably steady, and no leaks evident.
All this remembering Colin’s (I think) catch-phrase on seamanship – “if it’s easy to do (in this case stow), you will”.
Br. Rob
Hi Rob,
Yes, as long as you can strike it all down in a reasonable period I think it’s fine. That said, I’m seeing a lot of very flimsy set ups without this ability so it’s worth pointing out regularly, particularly to those who are refitting boats but have not spent much time at sea.
John,
Great article and perfect timing as I was looking for another alternative to our propane stove. During my research, I found a product by Wallas, built in Finland that solves two problems – convection stove top and heater. You can find this unit here: https://scanmarineusa.com/products/stoves/wallas-nordic-dt-diesel-stove-heater/
This seems to be a good solve for boats smaller than 40′ and would provide nice dry heat when needed and a hot stove top but would require another five minutes to heat up.
Downsides – I found two. 1) heat up time would seem to be slower than electric 2) Cost. At $2,800. it’s tough decision to remove my old but working propane stove and oven.
Take a look and let me know your thoughts.
Hi Dan,
I will touch on that in a future article in a couple of weeks.
We moved to an electric kettle first and then an electric hob and then induction. With 450w of solar aboard we can perhaps do 70% of cooking / tea on electric. I haven’t worked it out in detail but one 4.5kg gas bottled used to last about 21 days full time aboard for two people and not it lasts double that. Of course we’re still using gas for the oven but being a Yorkshireman, there are a disproportionately high number of cups of tea in any 24hr period.
Either way, it is nice to be using more renewable energy and not having to refill gas so often. For anyone considering it then I’d certainly recommend at least an electric kettle and to be particularly vigilant about only boiling the exact amount of water you require each time.
Hi Tim,
That’s interesting and makes sense to me, but of course such a system would not satisfy those who really hate propane to the point they won’t have it on the boat (not me).
Well we’re all on a journey and this is no different. We’ll be adding another 150w to our solar soon and perhaps lithium batteries in the coming years. Perhaps then we’ll have sufficient to be 100% and even consider an induction oven.
The other important aspect is the use of induction while on shore power. It still saves gas and it doesn’t require lots of solar or wind. I still see most people cooking on gas even when hooked up which I find odd personally.
Hi Tim,
As to the “odd-ness” of using propane to cook when attached to shore power…
When in Europe, we were attached to shore power/marinas far more than usual. The use of an electric tea kettle made a huge difference as we are tea drinkers throughout the day: 4-5 cups times 2 people adds up to a lot of water heating. That said, it is the only electric cooker we chose to use.
We had one season (in 11 in Europe/Med) where we were worried about propane access and bought a hotplate. We used it and it helped, but was a pain in a small boat with limited storage for gear like that and counter space that doubles as access to frig/freezer.
So, we cooked with propane (kettle excepted) when on shore power. It was just so convenient, so like “home”, cooks far better and (well set up) so safe that we never considered cooking any other way.
My best, Dick Stevenson, s/v Alchemy
Hi Tim,
I don’t think there is such a thing as an induction oven? Do you know of one?
I was speaking with Brain from SV Delos and I thought he said they had an induction too and oven…. but on checking they have an induction top and electric oven, albeit an efficient one. However I believe Whirlpool make an induction oven. I’ve no idea on the efficiencies of one compared to an electric.
Hi Tim,
I looked but I think Whirlpool confuses things by saying “Induction Range” but if we look at the specification it’s clear that only the cook top is induction. (Same with our Boche)
The more I think about it the harder I find it to come up with any way to have an induction oven. I guess they could use induction to heat an element but I can’t see how that would be any more efficient given that the food is separated from the element, unlike a cook top.
Consumer reports: https://www.consumerreports.org/electric-induction-ranges/pros-and-cons-of-induction-cooktops-and-ranges/
Relavant quote:
Hi Tim,
our setup is very similar to the Delos setup (same type of boat even) and the oven is a convection oven. We went with the Steba DG 30 and it is extremely efficient. Many of the smaller convection ovens are surprisingly good.
Hi John,
I’ve done a little searching and have found Bauknecht BIVMS 8100 KOMFORT, which is an oven with a pluggable induction pan and an electric “grill” element on top. The oven supposedly automatically switches between heating from the bottom and from the top. Marketing materials claim that it can save up to 50% of energy, compared to standard electric oven.
Hi John,
As the heading asked the question?
I think after reading the commentators responses the answer is Yes…If you have a generator, then whilst it’s running it would make sense to use induction for example.
Same if you had a watt and sea travelling with excess power. Or any other example were you are in energy surplus. Then I think that the savings on gas and the pain it can be to obtain, could make the addition of a portable induction cooktop worthy. I know if I could save 10 or 20 percent of gas I would be happy
Damian
Hi Damian,
Good points, that said there is more coming on the modifications required for full on electric cooking and actually getting rid of gas.
Hi John,
A friend just sent me a link to this recent piece by Jimmy Cornell on the failure of his quest to have a purely electric boat. He doesn’t give numbers as to where the energy went but I get the impression that cooking is not a small portion of it. I wish it were not true but it is good that he is being honest with people so that others don’t have to learn the hard way.
https://cornellsailing.com/2020/12/electric-shock/?fbclid=IwAR3-umppGxXfSKPSJloVt6XEn86NVFgLZGhQlefsG_MtJpE6OaJ6aUO3ZqQ
Eric
Hi Eric,
Thanks for the link. An interesting read. As you say, I too wish it were not true, but Jimmy’s experience is pretty convincing. On the bright side I hope this will go at least some way to ameliorating the damage being done by the snake oil salesmen who have gravitated to electric power. I listened to one giving his pitch at the Annapolis boat show and he was both seductively convincing and full of it. The only other salesman that came close on both counts were those selling “drop in” lithium batteries.