Question on long term low wattage vs short term high wattage

[SheketEchad]

I haven't posted in eons because my nomadic life plans got derailed by those pesky real life plans.  But I'm back on track now.  

I drink a lot of coffee and tea.  The lowest watt electric kettle I have is 1000W and it's as old as the hills.  However, I have a tiny 25 watt crock pot mini for sauces and such, and I have found that if I leave it plugged in all day (currently landlocked on grid) it gets plenty hot to make both coffee and tea.  I have found collapsible kettles for 820 watts or 12v cig lighter kettles at 100/240 watts but they take 40 minutes to boil water.  And I'd have to buy it. 

Yes, I have a camping stove but I'm not keen on using those to boil water either as they use imo far too much fuel for such a repetitive need.

Which is least impacting on a solar set up (which I don't have yet)?   A five minute burst of 1000W kettle each time I make a cup, or leaving the little 25W dealio plugged in all day? (I estimate I'll have 700 watts of solar and 200Ah of batter initially - I have a lot of electronics for work)

Thanks in advance, and one of these days I'll get the hang of this stuff!!

~SE

 

[highdesertranger]

I am assuming both of those is 120v. if so you will have to run though an inverter so you will need to add 10-30% of loss due to the inverter. heating anything with electricity is inefficient, you don't notice when on the grid because electricity is so cheap.

keep this in mind,

it is always cheaper and easier to conserve energy then it is to make energy.

if it were me I would use propane.

highdesertranger

 

[SheketEchad]

Thank you. More things to ponder then, yes.

And yes, both are 110 appliances.

Maybe just a BIG thermos and boil water twice a day on the propane stove would be the actual most efficient way, hmmm.

 

[bullfrog]

Where I am at now just putting tea bags makes sweet tea in a clear gallon jar in about an hour and a half in full sun. I am on full hookups with an insulated inlet water hose but it still gets well over 100 degrees so since my motorhome is air conditioned and the water heater insulation has a removable cover we let the air conditioner cool the water heater tank water with the heater turned off and use it to cool the cold water that the hose has super heated so we don't have to run the water ten minutes to get it down below scalding. Full sun 102 degrees here today. I bet you could design a container in a solar oven type area of your windshield or set it on your hood of your vehicle and avoid overheating bitter tasting beverages. In winter I have heated water with my kerosine heater simply by putting a pan on top while warming up the space. Heating water with electricity is very inefficient.

 

[tx2sturgis]

When it comes to heating with electricity, the heating elements themselves are (effectively) 100% efficient, but the efficiency loss is always in the production, storage, and delivery of the electricity to the heating unit. Efficiency does not matter as much if you have plenty of cheap or free electricity...but that is the catch...and it's a big one when it comes to solar.

If you use 1000 watts for 10 minutes, that is about 166 watt-hours of energy pulled from your batteries and panels.

It will take about 6 1/2 hours for the 25 watt unit to pull the same amount of energy...but standby-losses will be much greater with the smaller unit...meaning the heating effectiveness will likely be less than the numbers would indicate.

But you also need to figure in 'opportunity'...can you blast that 1000 watt kettle around 11AM when you have full sun? Or wait till 3 PM when the sun comes out for a half hour between clouds?

Or will you have to be operating that little 25 watt kettle from noon till 6:30 pm and HOPE the sun stays out for the duration.

The fact is, propane (or other liquid or gaseous fuel) is much better at heating when used for cooking and for boiling water. 

But it does have to be replaced now and then....whereas if you have plenty of solar power, you can use that for 'almost free' and endlessly after the initial investment.

But overall (calculating ALL costs) the most bang for the buck for heating water or cooking food when off grid, is propane.

 

[maki2]

If you are in a campsite and there is no burn ban on you could use one of the little "rocket" stoves that can heat water with a pile of twigs or pine cones. There are quite a few commercial versions of them as well as DIY instructions for making them. Not too difficult to find fuel materials for them and a small bin box of fuel would keep the kettle going for a week or more depending on the quality of fuel and how long you run the stove for. If you are not in an area where there are twigs to be picked up small scrap pieces of wood from a construction site, lumber yard, etc will do. As will splitting up some of the bundles of kindling sold to campers.

When you heat water make more than you need for that morning or evening hot beverage and the put the extra hot water into a high quality thermos to have later.

 

[WalkaboutTed]

I have one of those collapsible silicone kettles (800w) and one of those baby crockpot warmers. I use the crockpot for cooking oatmeal (long cooking pinhead). I put the oatmeal, salt and water in when I go to bed at midnight and it's ready in the morning. When we're traveling in Hubby's van, we use the kettle filled up (twice) to make coffee. Then we use the 700w microwave to make it piping hot again after adding milk. I don't like to have open flame in the van. I'm a major klutz and I'm petrified of fire. Be aware that the kettle doesn't auto-shutoff at elevation over 8000' because of the lower boiling temperature. It is very fast, less than 3 minutes to get to a boil when full.

We have 450ah of battery and 540 watts of solar (360w on top and 180w on the side). The thing that makes it easily possible is the solar on the side. It'll outproduce the top solar from 8:1 (when the sun first comes up-pointing panel directly at rising sun) watt for watt and generally output will equalize with the top solar panels at about 1030. But that's when the batteries are the hungriest. Usually the batteries are taking in way less than an amp per 100ah by 1300.

On the second or third cloudy days, we only boil the kettle once and I have to micromanage my solar with the charge controller to force feed the batteries. Fortunately, we hang out in the Mountain West with great sun almost all the time.

At least the batteries tolerate that load in the summer. I won't know in the winter as I'm traveling in the trailer and the battery/solar system is not as robust. And there I have a propane range to do the heavy lifting.
Happy travels,
Ted

Edit: I also run a 4.6cuft 12v fridge, LED lighting and running a ton of USB(micro and UsbC) devices on this system.

 

[maki2]

Maybe this information will help you calculate the actual fuel cost of heating water with propane.

A BTU (British Thermal Unit) describes the amount of energy to raise 1 lb of water 1 degree Fahrenheit in one hour. Water equals 8.3 lbs per gallon. To boil one gallon of water starting 70°F in 1 hour you will need 8.3 x (212-70) = 1,178.6 BTUs.

Of course now you have some math to do with those numbers, the amount of water you want to heat and how quickly can you bring it to a boil.

You do need to know the maximum BTU output of your camp stove. You also need to how many BTU of fuel are in a full container of fuel. There there is an online burn time calculator for figuring out how long of a burn time your stove will have at maximum power. Or you can make a guess-ti-mate of how many BTUs you will use with a low or medium flame setting.

I only make one cup of coffee at a time so it does not take me very much time to heat water for coffee and I don't do it on the highest flame. I would have to do that rough estimate of BTUs. But fortunately I am not going to go broke heating water for coffee on my little Gas One Mini stove as I only make one or two small cups a day using an Aero Press pot. In the winter time I can heat water with my diesel fueled cooktop/heater unit and it cost me nothing extra to make hot water or cook meals as I am already using the unit to produce the heat to keep me warm. Some people put a wire grid on top of their Mr. Buddy heater for heating up water for coffee so they too have no fuel cost for heating water for coffee when they are heating their RV.

 

[SheketEchad]

Thank you all for taking the time and fleshing out what perspective I need to look at when considering what to use for the most efficiency. Several of you gave me more information to go dig up to help me understand how to look at it.

I appreciate any input, as the world of solar (other than cool lights for enduring hurricanes) is very new to me and your experience is valuable inputs to my analytic brain I have a lot to learn!

 

[highdesertranger]

also there is approximately 91,600 BTU in a gallon of propane. so in a standard BBQ bottle there is appox 439,600 BTU's that is a lot of boiled water.

highdesertranger

 

[SheketEchad]

I currently only use the little green ones.  Did I mention I drink a LOT of coffee and tea  
But seriously, the use of different strategies is something I need to wrap my head around, so all feedback is good (even if I don't understand some of it yet!)
If you try to think this life through BEFORE you go, sometimes it feels daunting.  Other times I think, "You know, you MIGHT be overthinking this"... (terribly bad habit of mine)

 

[WalkaboutTed]

Hey Quietone,
I knew nothing about solar when I started looking into vandwelling three years ago (I'm a sixty year old RN). I started reading and reading and reading. I did use YouTube for a couple of questions, but I do better with the written word.

I knew what I wanted to use in the vans and trailer and built my systems around it. Primarily electric coffee making and and fridge. Figure out what you want and start from there.
Ted

 

[SheketEchad]

Thanks, Ted.

Yes, I'm reading and watching, and reading some more. It's pricey stuff and I want to do it right. It's the mix of watts, volts, conversion, transmission loss, don't let the batteries get below xyz, sealed or not, 6v vs 12v, and the wiring and fuses that just make me walk away and watch kitten or music videos for a while. I don't know anyone around me that ever has used anything solar other than garden lights or emergency flashlights.

The only thing I truly understand so far is that batteries store the power, the inverter converts from one to the other type of juice, and appliances munch on it depending on how they are made; that some things eat a big bite at start up then cycle to maintain, and others eat small bites over time and some appliances you just need to put in the garage sale! Mostly I feel like I should just cook over propane and let the solar run my work electronics and to heck with it, lol! I haven't figured out the job of the charge controller yet at all - or what running in parallel or series means.

I'll get there. Thankfully I'm not having to jump quickly at this point so I have time to learn well and avoid money falling on the ground and disappearing!

Everyone is very helpful, and I appreciate that so much.

 

[Skyman6529]

My wife lives in coffe. I'm the guy who provides the utilities. So I've figured ways to make it quick and efficient as possible. Here's my solution(s)

This is her quick need coffee now burner.

A very cheap small propane burner that screws  directly on top of the bottle. Perks quick  on high,  saves fuel on medium going slow.
Tin foil around the bottom of the coffee pot in a cone collecting all the heat from the burner almost doubles the speed.
Room temp water takes less than half the fuel of cold water as well.

We now use a  coleman peak 1 or 500a  fastest perk time so far.
A very small tank will last for at least three days doing coffee and cooking meals for two. Minimal storage space and very reliable. We also use ours for tent heat.

As for fuel consumption I bought a one gallon plastic gas can (they work great on gasoline just fine). I have never used the entire gallon on any trip. I always end up pouring the extra in the gas tank. The fuel truly lasts that long. They average 20-$25 in excellent shape with a case. They are completely rebuildable on the cheap as well.

They're used for backpacking, and i've used them for 25 yrs with no safety issues. Didn't mean to write a book,  but they're an awesome small burner, and the fuel has multiple uses. I actually carry them under the seats in both cars.

 

[SheketEchad]

Thank you, Skyman6529. I think I need to rethink many things in regards to propane/butane. Just like most everything else when considering this vs S&B living.

I think my test will be to set up some sort of alternate (propane/butane/gasoline) stove and keep good records. Because my camp stove used solid fuel which is expensive, I thought it was more expensive. But several people's responses have made me reconsider that frame of reference.

For the first time, I'm also able to track what a devices consumption of battery life is, which has been quite the eye-opener(yes, I am nerdy and track things in a spreadsheet, lol) Things you think are 'okay' when grid powered start to look very different when your aim is conservation. I love learning new stuff!