Pushing the limits of electric cooking

[noelex 77]

Originally Posted by s/v Jedi

We have 1,875W of solar. We do 100% electric cooking except for the cockpit grill which is still propane, using the little 1lb tanks. Looking into making that electric too

Thanks for the data point, especially as you are one of the few that has responded to the thread and manages all electric cooking (with no propane) without a generator or needing some engine run time.

[s/v Jedi]

Originally Posted by noelex 77

Thanks for the data point, especially as you are one of the few that has responded to the thread and manages all electric cooking (with no propane) without a generator or needing some engine run time.

I think it’s important to know how much output the solar array actually generates, because I hear often that they never get rated output. There’s also big differences between solar panels, with some that have fantasy specs My avg. daily production is between 6 and 7 kWh

[fxykty]

Originally Posted by s/v Jedi

I think it’s important to know how much output the solar array actually generates, because I hear often that they never get rated output. There’s also big differences between solar panels, with some that have fantasy specs My avg. daily production is between 6 and 7 kWh

And it’s important to know how much output you can rely on for the areas and seasons that you plan to cruise.

For example, your statement that you have average production of 6-7 kWh from 1.85kW of panels is fine, but it’s only useful if you also tell us what time of year and what location.

Otherwise it’s no better than saying “count on 3-4 times your panel size in daily output”.

[s/v Jedi]

Originally Posted by fxykty

And it’s important to know how much output you can rely on for the areas and seasons that you plan to cruise.

For example, your statement that you have average production of 6-7 kWh from 1.85kW of panels is fine, but it’s only useful if you also tell us what time of year and what location.

Otherwise it’s no better than saying “count on 3-4 times your panel size in daily output”.

It’s 6kWh in the winter and 7kWh in the summer, sorry, I thought it was clear. Both numbers are averages, i.e. I have days of 10kWh but also of 2kWh.

[Na Mara]

Originally Posted by s/v Jedi

It’s 6kWh in the winter and 7kWh in the summer, sorry, I thought it was clear. Both numbers are averages, i.e. I have days of 10kWh but also of 2kWh.

I reckon I can fit 900W of permanent solar (300W semi-rigid in a somewhat shaded location, 600W rigid in a basically completely unshaded location.). This is about half of what you have Jedi so hopefully I will be able to harvest about half the energy you do. Say 2.5-3.5kWh a day on average. That will be enough for my needs at rest and may just be enough underway as well. Add running a 100A alternator maybe 5-7h a week on average when arriving, departing, and heating water and I should not require the backup petrol generator much. Maybe in and around mid winter in the med and definitely winter cruising off plug in the baltic the petrol genny will see use, but use should be rare given what Jedi has said and my daily stationary consumption of 2.5kWh including cooking.

[noelex 77]

Originally Posted by Na Mara

I reckon I can fit 900W of permanent solar (300W semi-rigid in a somewhat shaded location, 600W rigid in a basically completely unshaded location.). This is about half of what you have Jedi so hopefully I will be able to harvest about half the energy you do. Say 2.5-3.5kWh a day on average. That will be enough for my needs at rest and may just be enough underway as well. Add running a 100A alternator maybe 5-7h a week on average when arriving, departing, and heating water and I should not require the backup petrol generator much. Maybe in and around mid winter in the med and definitely winter cruising off plug in the baltic the petrol genny will see use, but use should be rare given what Jedi has said and my daily stationary consumption of 2.5kWh including cooking.

It is great to hear you are planning on continuing to cruise in winter in the Med. We did this for many years, and had a great time. Surprisingly very, very few boats do this. 99.9% go into a marina for the whole of the winter period. Why so few boats continued to cruise is a mystery. Air temperatures are not very low and with modern anchoring gear the winter storms are not the problem at anchor they would have been (in fact I you may be safer at anchor than in a marina).

I am very familiar with the solar conditions. The solar insolation in summer is excellent, but in winter it is poor and you will be running your petrol generator every day for several months if you want to support electric cooking.

We have not cruised the Baltic, but have cruised Norway, Scotland and Ireland which encompass similar latitudes. Once again in summer the solar insolation is excellent, particularly in the northern latitudes that have very long solar days. However, in winter solar insolation is very poor. In our most northern cruising area the peak sun angle at solar noon was around 10° above the horizon. In anchorages with reasonably high hills you never achieve any direct sunlight even at solar noon. With 1000w of solar and a very electrically efficient boat we managed to harvest almost enough energy to continue to power the boat on solar alone, but there is no hope of considering any electric cooking. You will be running the petrol generator every day for long periods.

Electric cooking is fantastic, but you need to have realistic expectations about the energy involved and the amount of electricity that will be produced.

[Na Mara]

Thanks for the words of encouragement noelex. I think you are probably correct that we will need the petrol generator when you say we will need it, but I don't think we will need it with the frequency you claim. With close to 6kWh of dispatchable energy in the battery and a daily usage of about 2.5kWh including 0.8kWh for cooking when stationary, I should be able to bridge about 3 days between charges even with really poor insolation in mid winter in the med. More if you add the estimated 5-7kWh a week I will get from the alternator in normal operation. So running the petrol generator should be less frequent than you state but when it runs we will be running it at near full power for 3-4 hours a time to recharge everything so the fuel usage will be roughly what you indicate (about 6-8l a week by my reckoning), but the annoying noise will only have to be endured every third or fourth day on average.

I'm also going to try every trick in the book to reduce consumption, from thermal cooking, to dimming plotter screens, to installing LED lights every where, to not running radar most of the time, to hand steering a fair proportion of the time (I quite enjoy it), to manually winching most of the lines most of the time, etc. Hopefully, I can come quite a bit lower in consumption than my worst case consumption calculation (sum of products of stated wattages of appliances and worst case estimates of run times) and thereby be even less reliant on the petrol generator. But that I will have to use it a fair bit in the winter am I fully convinced of.

[Pete7]

Originally Posted by Na Mara

I'm also going to try every trick in the book to reduce consumption, from thermal cooking, to dimming plotter screens, to installing LED lights every where, to not running radar most of the time, to hand steering a fair proportion of the time (I quite enjoy it), to manually winching most of the lines most of the time, etc.

Curious were you are up to with the modifications?

Pete

[Na Mara]

I have purchased the techimpex horizon 2 micro compact electric stove with combination microwave convection oven. It’s silly money and not induction but if is THE only unit that fits the boat and electrical system. Delivery is due in a month and it’s plug and play now that I have run the cabling.

The batteries and inverter are fitted but I’ve had a hitch configuring the inverter charger. It’s a programming issue and should be fixed soon.

I have reconsidered the whole solar-wind thing. A wind turbine on average generates about the same as 200W of solar. Including all the accessories a wind turbine comes in at 3500euro whereas 200W of good quality solar bolted to the push pit is 1000euro. It’s hard to argue with those numbers.

I can fit 640W without too much of problem, and am presently ordering the materials for this. Working on the standard 5 x wattage daily input from solar the 640W will deliver 3.2kWh which will meet the 2.5kWh stationary needs but not with a huge margin. Underway I need something else as the autopilot burns 1.5kWh a day and the instruments eat another 0.5kWh. That looks like being a hydro generator as I need lots of reliable power underway. I’ll just have to put up with the active management aspects of that system. Between parasitic charging off the engine, shore power, the solar and the hydro, the petrol generator should not be needed very much.

[s/v Jedi]

Originally Posted by Na Mara

I have purchased the techimpex horizon 2 micro compact electric stove with combination microwave convection oven. It’s silly money and not induction but if is THE only unit that fits the boat and electrical system. Delivery is due in a month and it’s plug and play now that I have run the cabling.

The batteries and inverter are fitted but I’ve had a hitch configuring the inverter charger. It’s a programming issue and should be fixed soon.

I have reconsidered the whole solar-wind thing. A wind turbine on average generates about the same as 200W of solar. Including all the accessories a wind turbine comes in at 3500euro whereas 200W of good quality solar bolted to the push pit is 1000euro. It’s hard to argue with those numbers.

I can fit 640W without too much of problem, and am presently ordering the materials for this. Working on the standard 5 x wattage daily input from solar the 640W will deliver 3.2kWh which will meet the 2.5kWh stationary needs but not with a huge margin. Underway I need something else as the autopilot burns 1.5kWh a day and the instruments eat another 0.5kWh. That looks like being a hydro generator as I need lots of reliable power underway. I’ll just have to put up with the active management aspects of that system. Between parasitic charging off the engine, shore power, the solar and the hydro, the petrol generator should not be needed very much.

Those are old tech ceramic hobs. They will use twice the power from your batteries compared to induction… if not more. Hope you have the electrics to support that…

[Na Mara]

The actual efficiency gain of induction over resistance glass ceramic is about 30%. That is a lot and I have budgeted for it, but then I will have a gimbaling microwave, kettle, etc and I will use thermal cooking. Thanks for the concern but I can cope with the extra load.

[Kd9truck]

I crewed a vessel for 22 days, 2300nm off shore with induction cooktop and oven, bread maker micro wave and back up single burner portable hob. I will add, I was a chef in a past carrier so I put it to the test. I was tripping breakers when I had it all in play. It’s not that limiting to stage what you do so that you don’t overload the system in the kitchen, most can only do one thing well at a time anyway, sea state makes a great scape goat for the unskilled.
The power side was fed by wattsea, wind and a generator off shore every 3 days for watermaker and topping off of the lithium bank.

[Na Mara]

Thanks for the real life info KD9. I had already figured that when not hooked up to a petrol generator or shore power I’ll only be able to use 1 or 2 out of the 3 facilities in the cooker. The inverter is 2.4kW, the two hobs on half power are 1.5kW. Without the power boost function and 230V coming in through the shore power socket, I won’t be able to use all 3.75kW of the cooker. I can live with that.

[s/v Jedi]

Originally Posted by Na Mara

The actual efficiency gain of induction over resistance glass ceramic is about 30%. That is a lot and I have budgeted for it, but then I will have a gimbaling microwave, kettle, etc and I will use thermal cooking. Thanks for the concern but I can cope with the extra load.

The 30% difference is the difference in power transfer from electric energy to heat inside the pot.

But there is more: with a ceramic electric cooktop, you have to heat the cooktop itself before you can heat the food. This is like a pre-heat which is skipped by induction.
Also, at the end of cooking, the ceramic plate keeps radiating heat for a long time, which is all wasted energy and which does not happen with induction.
These start and stop events don’t matter much for hours long simmering sessions, but for most average cooking, like frying or boiling eggs, frying some bacon etc., they make a lot of difference.

The ceramic stove tops target boats that run gensets rather than have solar arrays.

[rslifkin]

Originally Posted by s/v Jedi

The 30% difference is the difference in power transfer from electric energy to heat inside the pot.

But there is more: with a ceramic electric cooktop, you have to heat the cooktop itself before you can heat the food. This is like a pre-heat which is skipped by induction.
Also, at the end of cooking, the ceramic plate keeps radiating heat for a long time, which is all wasted energy and which does not happen with induction.
These start and stop events don’t matter much for hours long simmering sessions, but for most average cooking, like frying or boiling eggs, frying some bacon etc., they make a lot of difference.

The ceramic stove tops target boats that run gensets rather than have solar arrays.

The heat soak in the cooktop problem is definitely significant with glass top stoves. It's less of an issue for an open coil stove (where there's nothing between the heating element and the pan).