24 volt underfloor heating

Zuiderzee

Hi All,
Anyone try electrical underfloor heating off battery for, say, a remote shed.

The basic premise is to have a large battery charge up off a wind turbine (as found on yachts) and/or solar panel.

If temp drops below say 5 degrees, the heater kicks in

All advice or pointers welcome

quentingargan

Zuiderzee wrote: »

Hi All,
Anyone try electrical underfloor heating off battery for, say, a remote shed.

The basic premise is to have a large battery charge up off a wind turbine (as found on yachts) and/or solar panel.

If temp drops below say 5 degrees, the heater kicks in

All advice or pointers welcome

Using turbines for heat is quite inefficient. Heat from other sources is generally quite cheap per KwHr compared to electricity for lights. So electricity is a sort of "premium" fuel and turning into heat reduces its premium value,

But the biggest problem is the cost of cycling batteries. I estimate that to be a cost of about 11c per Kw Hr. Fine for lights, radios, cattle fencers, even TVs, fridges etc., but really bad value for heating.

By all means, use a turbine (or probably a solar PV for this scale) to charge a battery and when the battery is fully charged, use the surplus energy to heat something. But I wouldn't use a battery to run a heater.

Capt'n Midnight

Have you ever heard of the Chicken Powered Nuclear Landmine ?

Use lots of insulation.

plant stuff around it to keep the wind off too

How much heat do you need ?
a one bar heater is 1000w
a light bulb (heat ball) is 100w

car battery size is 50Ah
two of them would give 1250Watt hours - 10 hours of a 100w light bulb
because you can't use car batteries , they aren't designed for deep discharge, you can get storage batteries but even then you don't want to be going below 90% on a regular basis if you want a good long life

Don't forget it's unlikely to freeze if you go down a foot or two into the ground. Perhaps some form of primitive heat pump ?


If you want instant heat then you could just hook up a windmill to an air pump with closed valves - not sure about efficiency

Zuiderzee

Chicken landmine ROFLMAO - have gone of the pure electrical idea, going for liquid heated by wind turbine system - drawings later

Capt'n Midnight

you could use phase change heat packs to store heat instead of batteries
bag of liguid and you press the clicker and it goes solid
https://en.wikipedia.org/wiki/Sodium_acetate

it depends on how much heat you need, and for how long

Zuiderzee

Ships electrician took a look at the idea I wanted to try out and came up with a plan using 24 volt 300 watt system, heat liquid in tank and circulate from there.

Will install pipes during build and take it from there - 24 volt heating elements are easily available on ebay etc.

Will scan in plan in the next few days for comments and ideas

Zuiderzee

OK - all comments welcome.
Idea includes use of a 55 gallon drum as the water tank, so if anyone has any experience in this advice appreciated.

Heres the plan so far

quentingargan

I would keep that open vented rather than pressurised. Any failure of the pump and you only have pressure relief valves between you and the moon. I wouldn't rely on pressure relief valves on their own.

You could possibly use a mild steel tank covered in layers of Kingspan, rather than an expensive stainless cylinder, provided you put corrosion inhibitor in the water.

I still feel that the power from a 300W turbine is better used for low energy applications such as lights and power rather than heat. On most sites, it will average about 500 Kw Hrs per year, or if that is converted into heat with a normal cost of 10c per Kw Hr, that's only €50 per year. The hardware called for here is quite a bit.

Capt'n Midnight

300W

you might be better using solar heating , passive circulation so no moving parts apart from expansion valve and a lot of anti freeze

Zuiderzee

Obviously passive circulation would be preferred, but I dont know if it would work well.
As for antifreeze, I'll just dump a load of raw alcohol into the system

Tank plan underway

hi5

Why bother with a tank at all?
Use a closed loop system with an expansion tank, use 2 or 3 relief valves rated higher than the expansion tank if your really worried.
The less liquid you have to heat, the quicker it will heat the room.

And don't forget an airlock valve for any high points.

Capt'n Midnight

How about a composter filled with rotting vegetation ?

Zuiderzee

Capt. Midnight / hi 5 - if you could sketch a circuit diagram / expansion tank or point me in the right direction that would be very appreciated -

As for the composter idea, thats not really an option I think - anything that the chickens dont get goes for the veg patch

Capt'n Midnight

This is where I started. Put the chickens in the shed :pac:

Composting generates heat. If you are using it for that purpose in the veg plot fine. If you aren't then you might as well compost in the shed. Yes there are problems if it gets too cold.

Just giving very low tech suggestions.

Zuiderzee

Looking more and more at passive circulation Capt Midnight, but giving the chickens a miss :pac:

- and yes, composting done in garden beside the house - shed is going to be quite remote.

Just looking at thermosyphons - my new favourite word