Solar for my shed

[Deleted member 90956]

I have recently been given 2 150w panels 4 130Ah marine batteries and a controller which I will set up on a garden shed
I have a few questions
I would like to know if I could heat up and boil 6 galls of water for 90 mins using a 2 kw kettle element? (getting to boil takes 25/30 mins) so in all around 2 hours
Secondly would a 2500w inverter be ok to use or should I go bigger due to the length of run time or possible over heating of the inverter?
Third question when buying an inverter what should I look for obviously price comes in to play but it will not be used for TVs or lap tops maybe a radio and charging power tool batteries
Last question What would be the most suitable way of wiring up the batteries?

This process need to be done once a month so the batteries should have plenty of charging time

I really am a complete moron when it comes to all things electric so any help would be appreciated

 

[Spoon]

I really hate it when people just put "Get an electrician in to look at it." as it seems like the OP is just getting fobbed off, but in your case (with your name being Village Idiot & being a 'complete moron when it comes to all things electric') this is the only thing I would recommend. Messing with electricity can be dangerous. Not only can it kill you, it will hurt the whole time you are dying. Sorry mate.

 

[solarfred]

I have recently been given 2 150w panels 4 130Ah marine batteries and a controller which I will set up on a garden shed
I have a few questions
I would like to know if I could heat up and boil 6 galls of water for 90 mins using a 2 kw kettle element? (getting to boil takes 25/30 mins) so in all around 2 hours A: Why? Use a gas ring. You will knacker your batteries doing this. The total load is 400ah+ and you have 520ah total capacity.
Secondly would a 2500w inverter be ok to use or should I go bigger due to the length of run time or possible over heating of the inverter? A: The inverter needs to be the best possible quality. Cheap inverters catch fire as they are not made from quality materials. For a kettle you can use sufficient to cover the load. For battery chargers you need a decent sine wave inverter as most modified sine wave will not work.
Third question when buying an inverter what should I look for obviously price comes in to play but it will not be used for TVs or lap tops maybe a radio and charging power tool batteries A: See above
Last question What would be the most suitable way of wiring up the batteries? A: What is the controller? If 24v then go 24v system as cables/losses are much smaller. If the controller is MPPT then panels must be at least 30voc and in series.

This process need to be done once a month so the batteries should have plenty of charging time


I really am a complete moron when it comes to all things electric so any help would be appreciated

I cannot see any advantage to boiling water by solar. A few minutes to boil a kettle for tea uses a huge inverter when a gas ring will do it for a fraction of the cost. I understand this is a processing project but gas is a better way if cost is an issue.
It is not your best option in my view.

To clarify my answers are in the quote above.... also I would use the solar for lighting the shed and running all your other devices including security etc. but not water heating...

 

[R G]

You can get one of those mini gas cartridge units from Halfords for £15 . can take a kettle or small saucepan..

 

[Deleted member 90956]

I really hate it when people just put "Get an electrician in to look at it." as it seems like the OP is just getting fobbed off, but in your case (with your name being Village Idiot & being a 'complete moron when it comes to all things electric') this is the only thing I would recommend. Messing with electricity can be dangerous. Not only can it kill you, it will hurt the whole time you are dying. Sorry mate.

Sorry if I offended you at the moment we use a 19 kg propane cylinder, burner and 50 ltr stock pot to heat the water but as of 1st January we are losing vehicle access to the site and to walk in takes 20 mins through woodland so carrying in gas and other gear would be a problem
And yes you are right "Messing with electricity CAN be dangerous" and we would get a professional sparks in to do the wiring up but as I volunteer for a small charity funds are tight so I would so the donkey work (First fix so to speak) then have an expert to do the important stuff
Clearly the idea isnt feasible so another solution must be found
Once again it was not my intention to offend

 

[Spoon]

Sorry if I offended you at the moment we use a 19 kg propane cylinder, burner and 50 ltr stock pot to heat the water but as of 1st January we are losing vehicle access to the site and to walk in takes 20 mins through woodland so carrying in gas and other gear would be a problem
And yes you are right "Messing with electricity CAN be dangerous" and we would get a professional sparks in to do the wiring up but as I volunteer for a small charity funds are tight so I would so the donkey work (First fix so to speak) then have an expert to do the important stuff
Clearly the idea isnt feasible so another solution must be found
Once again it was not my intention to offend

Your post was not offensive in any way mate. I just had concerns about you hurting yourself. If your name was in jest then I took it the wrong way.
Have you thought of making a zip-line to site and transporting your equipment via this? (Yes, this is a joke, as I'm sure all the health and safety people would not be happy with the wonderful idea and spoil all our fun.)

 

[HandySparks]

I have recently been given 2 150w panels 4 130Ah marine batteries and a controller which I will set up on a garden shed
I have a few questions
I would like to know if I could heat up and boil 6 galls of water for 90 mins using a 2 kw kettle element? (getting to boil takes 25/30 mins) so in all around 2 hours
Secondly would a 2500w inverter be ok to use or should I go bigger due to the length of run time or possible over heating of the inverter?
Third question when buying an inverter what should I look for obviously price comes in to play but it will not be used for TVs or lap tops maybe a radio and charging power tool batteries
Last question What would be the most suitable way of wiring up the batteries?

This process need to be done once a month so the batteries should have plenty of charging time

I really am a complete moron when it comes to all things electric so any help would be appreciated

Looking at the physics of the problem:

I assume that your figure of 2kW is a guess, based on your experience of using a gas burner.

You want to heat 6 gallons, which is about 27.3 litres. Let's assume that the temperature rise required is from 10C to 100C, ie 90C.

Water has a specific heat capacity of 4.2kJ/kg.K

So, ignoring heat losses, the energy required to bring the water up to boiling point would be
27.3 x 4.2 x 90 = 10320kJ

1J = 1Ws so, at a heating rate of 2kW, the time taken would be 5160s = 86 min

In practice there will be significant heat loss unless the vessel is well insulated.

So, it appears that, for a 25/30 min heat-up time, your gas burner is putting much more than 2kW into your water. At least 6kW, maybe as much as 10kW.


Looking at the batteries. Based on the nominal capacity of the batteries, the energy stored is:
130Ah x 12V x 4off = 6240Wh = 22464000Ws = 22464kWs = 22464kJ

However, batteries degrade with time and use. There will also be conversion losses in the invertor and some cable loss.

So, you might just get the water up to boiling point, or you might not.


You need to find out how much energy it really takes to bring the water up to temperature and keep it there. Perhaps best done by heating the water in the container you propose to use by mains electricity for the time required and measuring the power consumed. You could also get an assessment by heating the container and measured quantity of water to 100C and then turning off the heat and accurately measuring the temperature drop with time.

 

[solarfred]

But you are forgetting that the batteries cannot be depleted 100% and 50% is a standard but arguable rule of thumb.Then you need to keep the pot boiling.....
The recharge rate is determined by the solar irradiation available and the quality of the controller and batteries themselves. The panels will give you maybe up to 6 amps on a good day and a good day in summer may be 6 hours so 6*6=36ah * 7 days = up to 252ah
If you get 4 weeks of perfect summer weather you will recharge the batteries (but never fully). The chances of brilliant weather for sufficient time each month is 100% not going to happen for a planned approach.
I would consider building/buying an electric cart to transport the kit and use the batteries to run that and that can be charged from the solar.

 

[Gavin A]

maybe but not advisable to all your questions.

Depends if the lifespan of the batteries, and efficiency of the system matters. If it's only being used once a week or so then I guess it could work ok for a few years.

 

[ruston]

If the site is secure buy a genny while you still have vehicular access.

 

[ian.settle1]

This is nothing to do with an illegal still is it?

 

[Worcester]

Try a solar kettle, forget the PV it's inefficient. I think navitron used to offer one, else search google
try here for starters https://www.navitron.org.uk/forum/index.php?board=27.0
or here Solar kettle-The Best Solar Cooking Technology Out There?SolarCooking

 

[solarfred]

But you have to wait for the sun to shine before starting the "process" and if it goes in halfway through the "process" you are knackered! Big flaw in that plan....
Using batteries you are storing solar power when it is/was available. In this case it will just stress everything when a gas cylinder is the easy most efficient answer. There may be a security problem also. Get just enough propane for each process or is 19kg just for one burn?
http://www.boconline.co.uk/internet.lg.lg.gbr/en/images/Cylinder-propane-factsheet410_168592.pdf