Pushing the limits of electric cooking

[Adelie]

Originally Posted by jordanbigel

Though I have not tried one, it seems a dubious proposition to assume that it can make rice as well as a proper rice cooker. Dubious may be an understatement. Microwave cooking does weird things to texture. Some may not have an issue with this.

Well, got mine thru Amazon from a vendor in Japan where they take their rice way more seriously than I do. I tried it a couple times, results seemed pretty normal to me.

[Adelie]

Originally Posted by MicHughV

correct me if I'm wrong....

I thought most all electric stoves, ovens, etc are 220 v...??

In the US there a bunch of 120v countertop appliances. I intend to buy those since there’re fewer issues with accidentally overloading the inverter.

[Na Mara]

I just had a moment there where I thought that the plan was caput, then I realised I am still good to go. I am prepared to keep cooking simple and within the limits of my inverter underway and on the hook, but I do want to be able to push the boat out when on shore power. What I realised was that most of the shore power hookups around europe are 16A 230V. Indeed, the AC wiring and fusing on my boat is sized for the same if I remember correctly. Thats 3,5kW that I have at my disposal when plugged in without tripping any breakers on shore or on the boat. Running both hobs and my oven at the same time I could well exceed that, add various mobile chargers and the water heater and I will definitely exceed that.

One solution to that problem is to just have two shore power circuits, or upgrade my wiring and fusing, and use two plugs ashore, but — as Dockhead will attest — that's a bit rude where we sail. There are never enough shorepower sockets and occupying two of them is just, well, inconsiderate to put it mildly. It seemed that even on shore power I would be restricted in how I cook.

So I thought I had hit a snag here but then I remembered that my new inverter/charger has a power assist feature. Problem solved! I set the current limit on the incoming AC to 16A and whenever I need more than 3.5kW the inverter kicks in and adds another 2.4kW. Even running both hobs full (3.5kW), the oven full (1.3kW), and the microwave full (0.6kW), I should still have 0.5kW going spare for chargers (I will have to remember to turn off the immersion heater though if I want to use the microwave at the same time).

I'm not sure that the power assist feature is common to all inverter brands, but even if it isn't, those Victron guys are very clever!

[Dockhead]

Yep, that's exactly what Power Assist is for!


But here's another trick you can use --


Your boat, if it's like mine, has a 32A shore power system, excluding only the 16A blue plug at the end of the shore power cable, right?


Many shore power connections for yachts in the Baltic are made by splitting a 380V three phase connection like fishing boats use, into three 230v 16A connections. Sometimes it's even done with an adapter with a red three phase plug and leads to three blue sockets. If the other boats connected are not drawing their full 16A from the other two 16A connections, then you can often take more than 16A. Commonly 18A, even 20A. In my experience the blue plugs and sockets are good for it.


That can help a lot. 20A x 230v is already 4.6kW.


Just put a temperature gun on the sockets periodically (you should do that even if you're only taking 16A) and don't do it overnight (you shouldn't be drawing 16A overnight either).

[Na Mara]

Sadly Dockhead, I think my boat is wired for 16A. I'll have to current limit to 16A and live within the 6kW limit that imposes when on shore power. But 6kW is more than I need so no bigee.

[Dockhead]

Originally Posted by Na Mara

Sadly Dockhead, I think my boat is wired for 16A. I'll have to current limit to 16A and live within the 6kW limit that imposes when on shore power. But 6kW is more than I need so no bigee.

You mean 3.6kW, right?

Of course it's possible to live on that. Power Boost helps a lot, and you have to manage the loads. I use electric heat in the winter so that requires a lot of load juggling, switching the heat off when doing electric cooking, etc.

I have one electric heater connected to the load shedding circuit in my Multiplus and that makes it MUCH easier to deal with.

Also, with lithium batteries you can be a lot more aggressive with using Power Boost since there's no absorption phase and you have so much greater cycle life. With lead batteries like mine you have to be judicious with Power Boost, as a lot of cycling really wears them out fast.

My ace in the hole however is my heavy duty generator. If I need a bunch of power for some reason I just crank that up, and I have 6.5kW on tap.

[Na Mara]

3,6kW from the shore, 2,4kW from the power assist off the inverter = 6kW on the boat when on shore power.

Yeap I intend thrashing every krone out of these batteries ;-)

[s/v Jedi]

Originally Posted by Dockhead

You mean 3.6kW, right?

Of course it's possible to live on that. Power Boost helps a lot, and you have to manage the loads. I use electric heat in the winter so that requires a lot of load juggling, switching the heat off when doing electric cooking, etc.

I have one electric heater connected to the load shedding circuit in my Multiplus and that makes it MUCH easier to deal with.

Also, with lithium batteries you can be a lot more aggressive with using Power Boost since there's no absorption phase and you have so much greater cycle life. With lead batteries like mine you have to be judicious with Power Boost, as a lot of cycling really wears them out fast.

My ace in the hole however is my heavy duty generator. If I need a bunch of power for some reason I just crank that up, and I have 6.5kW on tap.

He can use 6kW: 3.6kW from shore and the rest from PowerAssist.

In reality this isn’t needed when you plan energy consumption in the galley a bit. Normally when you have one induction plate going full power, the other doesn’t have to be full on. Modern ovens only use full power during preheat etc.

This is why I like that rice cooker so much, it doesn’t use so much power that it needs consideration.

[jipcho]

Using electricity to create heat (stove top cooking, or baking) is very inefficient, and a huge draw on power. In my opinion, you would need either a diesel generator, or need to pump up your batteries by running your main engine, to even consider this as an alternative to LP gas while cruising offshore. I had very few issues refilling LP gas bottles during my 15 years circumnavigating. Finding a gas fill station was never an issue, even in very remote ports of call. The issues were usually, the valve fitting not matching, or refusal to fill the tank because it wasn't inspected. These hurdles were frustrating, but always overcome without too much drama. As far as space goes, mine took up one corner of one lazarette in my cockpit, nothing that really bothered me. I never met anyone that had a fire on board involving an LPG tank.

[Na Mara]

Hi jipcho,

Let's look at this scientifically. A typical meal takes about 30 minutes to cook on an induction hob; sometimes less, sometimes more, but it's about 30min on average. It will usually involve two hobs and I wont be able to do that so instead I'll be cooking in series (starches first, store in thermos, followed by main course). So let us be pessimistic and say that it will take me an hour. I cook one hot meal a day and boil a kettle twice. My kettle is 1 kW and takes 10 min to boil 1 liter of water. So boiling the kettle will use 0.33kWh of energy. The induction hob will probably be run at about 0.8kW on average so that is 0.8kWh of energy. So in total, and being pessimistic, cooking will require 1.1kWh of energy per day.

My batteries stow around 6kWh of useable energy (allowing for an 83% DoD). My panels will deliver around 2.5kWh of energy everyday on average using the standard calculation of 4 x wattage. I have calculated my stationary consumption to be 1.8kWh. That is a pessimistic calculation based on max wattage of appliances and a pessimistic view of runtime. With cooking and kettle that is no 3kWh (being pessimistic). So my daily deficit when stationary will be about 0.5kWh on average. If I arrive at an anchorage with full batteries, I can stay there for 12 days before having to run my engine for additional power.

I don't see the need for a diesel generator. Maybe a higher power alternator, or (pair of) hydro generators, or perhaps a suitcase generator, as my panels wont keep up with loads when stationary or underway.

In general I agree that one can live with gas on board. I have done so for 40 years of sailing. Its even quite pleasant to cook with. Its just that with modern tech we don't need to live with gas anymore and I for one wont be sorry to see it go from my boat.

[Ballsnall]

Originally Posted by Na Mara

It will usually involve two hobs and I wont be able to do that so instead I'll be cooking in series,

Sounds like a major downgrade to me. If you are spending the majority of your time on shore power then you can probably accept the compromises otherwise you are just fooling yourself.

Your options as I see it are,
1. Keep the propane and use additional electrical appliances as appropriate.
2. Upgrade your electrical system (including charging) to match your requirements.

[noelex 77]

Originally Posted by Na Mara

My panels will deliver around 2.5kWh of energy everyday on average using the standard calculation of 4 x wattage.

The problem is this “rule” only applies in areas and times of the year when there is good to excellent solar insolation.

Energy production from solar drops significantly even moving to areas of moderate solar insolation.

Thus without a propane backup or alternative means of generating significant power, with only 600w of solar you will be confined to only cruising areas and times of year where there is good to excellent solar insolation unless you are prepared to frequently use marinas and rely on shore power.

Make sure you are happy with these restrictions, before ripping out the propane.

[Na Mara]

Ballsnall. I am upgrading the electrical system and hence why I am considering this. And it is not just a "keep the propane" situation. My propane system is from 1996 and is downright dangerous. It will cost me about 1200 euro to bring it up to code. Id rather spend that money making electric work for me. As for fooling myself about my cooking requirements, I think I know those better than you. I don't cook fancy meals, spaghetti bolognese is about as fancy as I get. Maybe the odd curry. I'm also a convert to thermal cooking https://en.wikipedia.org/wiki/Thermal_cooking which uses less energy and frees hobs that would otherwise be used for simmering. I also semi-regularly go camping and there I make do with one burner. One hob cooking I can definitely live with.

Noelex. 77. Thisis why I am probably going to have to upgrade my alternator or fit hydro but with 6 kWh of energy in the battery, even if I am only getting 1.5kWh out of the panels, I still have 4 days of reserve between having to charge. Then I can use my engine, or a suitcase generator, or I can move on and use the hydrogenerators. I have options, which I take will depend on how well I do with just the solar, but solar is good where I sail so we will see.

[Dockhead]

Originally Posted by noelex 77

The problem is this “rule” only applies in areas and times of the year when there is good to excellent solar insolation.

Energy production from solar drops significantly even moving to areas of moderate solar insolation.

Thus without a propane backup or alternative means of generating significant power, with only 600w of solar you will be confined to only cruising areas and times of year where there is good to excellent solar insolation unless you are prepared to frequently use marinas and rely on shore power.

Make sure you are happy with these restrictions, before ripping out the propane.

A school bus alternator on his main will neatly and economically solve that problem. It's certainly right to point it out, however.

[Ballsnall]

Originally Posted by Na Mara

I am upgrading the electrical system and hence why I am considering this.

Your upgrade was never designed to include an adequate cooking solution which you now want to "tack on".

You will have less capacity and functionality and will need to make serious comprises. You seem to be looking for affirmation that all will be fine but you system is seriously undersized.

Spend an additional 1200 euro on sizing your system correctly or replacing your propane system.