Hot outside but darn cold inside - PV direct to heater?

[readiescards]

My build is progressing and I'm now able to do the day job (software dev) from my insulated office garage powered by 4 of my 30 solar panels, some second hand batteries and some cheap charge controllers and inverters - magic and all good :-)

 

But the insulation and solar panels means I'm getting no thermal gain so while it is very sunny outside it is only 12.5deg C in my office!

 

Question can I connect my  currently unused 285W solar PV panels DIRECT to a heating element such as:

http://www.ebay.co.uk/itm/262902796592

 

or something else

just to get some (any!) heat into the office space without resorting to running a diesel generator?

 

[Onoff]

Similar here in our draughty old place. House is built on North /South line. Often warmer OUTSIDE.

 

You need a passive heater made from beer / pop cans. Check out here and on YouTube. Silly temperatures easily achievable.

 

http://stonehavenlife.com/7-diy-pop-can-solar-heaters/

 

Scorchio! 

 

DON'T make me make one!

 

 

[ragg987]

If your final plans include a power diverter like an immersun, why not rig that up with a cheap electric radiant heater to heat the space? I did something similar to assist with drying out our basement after screed had been poured.

[readiescards]

Sadly no plans for an immersun.

 Pop can solar thermal v interesting though ive no source for many cans. Have been thinking of a black bin bag with a length of plastic pipe running through it as my first solar gatherer

[Steptoe]

16 minutes ago, readiescards said:

Sadly no plans for an immersun.

 Pop can solar thermal v interesting though ive no source for many cans. Have been thinking of a black bin bag with a length of plastic pipe running through it as my first solar gatherer

I can do you a wheelie bin full every 10 days or so,

Postage may be an issue though,

 

[Onoff]

38 minutes ago, readiescards said:

Sadly no plans for an immersun.

 Pop can solar thermal v interesting though ive no source for many cans. Have been thinking of a black bin bag with a length of plastic pipe running through it as my first solar gatherer

 

By my rough calculations based on collected cans I could make a panel approx 400' x 200'.....half the size of @Steptoe 's mind.

 

 

As "luck" would have it I've just got a couple of lengths of 145x45mm come free from a mod in the bathroom. That'll do for the sides.

 

Do we reckon it feasible to build a "wall of cans" with the heat output at the top then duct downward and bring into the house at floor or sub floor level?

 

Wife WON'T be pleased!

[Onoff]

57 minutes ago, Steptoe said:

I can do you a wheelie bin full every 10 days or so,

Postage may be an issue though,

 

 

I didn't realise Bucky came in cans now!  

[SteamyTea]

2 hours ago, readiescards said:

Question can I connect my  currently unused 285W solar PV panels DIRECT to a heating element such as:

Ohms law will tell you what you can do.

 

[Onoff]

2 minutes ago, SteamyTea said:

Ohms law will tell you what you can do.

 

 

Got the T shirt.....seriously.

[SteamyTea]

Does it have beer and kebab stains on it

[Steptoe]

16 minutes ago, Onoff said:

 

I didn't realise Bucky came in cans now!  

 

Thinking about this,

I could do one side of my shed roof, be ideal for heating the kids pool,   , almost dead south, 12'x8' shed, so probably a usable area of 10'x 4' , i could get quite a few cans on that,

But, what would weight loading be like,? 

[Onoff]

6 hours ago, Steptoe said:

 

Thinking about this,

I could do one side of my shed roof, be ideal for heating the kids pool,   , almost dead south, 12'x8' shed, so probably a usable area of 10'x 4' , i could get quite a few cans on that,

But, what would weight loading be like,? 

 

The "wall of cans" ones in my link are just air heaters generally, a stack of cans taken to a central outlet at the top then a pc fan which is maybe powered via a small PV panel. Just ducts hot air to wherever. So many designs on the net in seemingly really cold but sunny climates. No brainer for a south facing shed heater. Guessing it might 'eff up the airtight envelope if you had one though!

 

Different kettle of fish if you want to heat water. My hybrid can with integrated copper pipe would do a small pool:

 

https://www.flickr.com/gp/122042403@N05/0QG376

 

I really must have another crack at that. I was planning on using multiple takeaway foil containers and titling the thread "Cheap Chinese Panels". 

 

 

[readiescards]

Thanks for the tin cans suggestions, which has made me think of some more ideas including ramming some black plastic pipe behind the solar PV panels and to push air through into the office space.

 

However back to the question

9 hours ago, SteamyTea said:

Ohms law will tell you what you can do.

 

 

While I understand this. I suppose my question is can I treat the solar PV panel as a simple 40V dc battery?  

i.e. I mustn't short the connections but otherwise I can pretty much do what I want

 

Or are there any additional considerations I must consider to ensure there is no damage to the panel?

 

[Nickfromwales]

9 hours ago, SteamyTea said:

Ohms law will tell you what you can do.

 

Can you give Paul some examples of how he can 'run' some numbers Nick?  

 

@readiescards, are you planning on using multiples of those little heaters? Maybe better to add some more batteries as well as panels to create a buffer, also may give you some 'sustain' for when the sun goes in, as in the heaters will still run. Prob best to fit an audible low voltage warning so you don't inadvertently over-drain the batts. Do you have an inverter for the panels to run on mains voltage? 

[ToughButterCup]

10 hours ago, SteamyTea said:

Ohms law will tell you what you can do.

 

 

Thank you very much for this post. The power (P) of a good graphic (G) writ large.

 

For the first time in my life I have realised that I can go round the graphic substituting 230 for each instance of V. 

Only took 63 years.... 

[SteamyTea]

That is the power of algebra.

 

So taking that little heater, was a 12V one that had a power of 200W.

We can work out the resistance using the 'orange' part of the chart.

R = V² / P

 

R = 12² / 200

 

R = 144 / 200

 

R = 0.72

 

Now, working out to see what would happen if the voltage was 40V

Using the 'blue' bit we can use.

P = V² / R

 

P = 40² / 0.72

 

P = 1600 / 0.72

 

P = 2222

 

That is 11 times the power, so I think you can work out what will happen.

Edited April 19, 2017 by SteamyTea

[readiescards]

7 hours ago, Nickfromwales said:

 

@readiescards, are you planning on using multiples of those little heaters? Maybe better to add some more batteries as well as panels to create a buffer, also may give you some 'sustain' for when the sun goes in, as in the heaters will still run. Prob best to fit an audible low voltage warning so you don't inadvertently over-drain the batts. Do you have an inverter for the panels to run on mains voltage? 

 

Sorry I forgot to say this is just a temporary solution and therefore I want to keep expenditure to the very minimum but will rig up something using some second hand car batteries and a cheap as chip inverter. Given it appears the little heater will blow up.

[Nickfromwales]

Good idea. A small 230v fan heater on its lower setting will work far better TBH. Try and get a <500w heater like this 200-500w one. 

[readiescards]

Sorted a £6 150W car fan heater and a few old batteries.

Nicely balanced at 12 Amp in and 13Amp out (when its sunny)

 

(Though 12A @ 12V is only 144W so long way down on the 285W the panels are supposed to generated - assuming input current measured at 12V and not the open circuit 37V)

[Nickfromwales]

Like it. Much better with a fan heater.