Heating a grain fan intake with solar panels.

[Neddy flanders]

If i have a 50kw solar array capturing full sun in late august and september could i connect it to an electric heater bank in a grain fan intake? anyone help me with the maths?
grain fan shifts 30,000 M3/hr
would a 50Kw array power a 25Kw heater ? (or more?)
how much would that raise temp ?

Sorry Im thinking aloud here.

 

[chickens and wheat]

Isnt solar generation powering the fan, if not electric motor makes sense
Next step would be some sort of solar trap, a green house thing to heat the air directly.
Or a dehumidifier powered by solar electric

 

[Neddy flanders]

Isnt solar generation powering the fan, if not electric motor makes sense
Next step would be some sort of solar trap, a green house thing to heat the air directly.
Or a dehumidifier powered by solar electric

25kw motor needs to be running on 3phase mains. looking to heat the incoming air. yes been looking at solar air heaters etc and solar water to a heat exchanger, but panels could be easier to install and wire some distance to the heater bank. is it viable?

 

[upnortheast]

Usual to connect solar into your mains supply to give consistent power. Can bugger motors with variations of cloud cover

 

[Doing it for the kids]

What’s your peak output likely to be?

my stores pull 2-300 kW‘s per hr of heat to make a difference.

I suspect it will not be worth it, @renewablejohn will have a good answer though

 

[renewablejohn]

Have a look at combined PV and thermal solar tubes. 50kw PV would also produce 150kw of thermal all at the same time so you could use the PV to drive the electric fans to blow the thermal heat. If your really thinking out aloud then have a look at the tin sheet drying systems.

 

[Exfarmer]

Firstly the good news
your 25 Kw heater will heat 30,000 cu meters of air by 24 degrees according to may best reckoning.
air requires 124.7 KJ of energy to rise by 1C per cubic metre.
So 30,000 X 124.7 = 3,742,320 KJ
your heater chucks out 25,000 KJ/ sec
so 3,742,320/25000 = 149.7 secs to rise one degree and this equates to 24 degree per hour.
This is obviously far more than you need or want , unless it is continuous flow.
The Solar can chuck out easily 40 Kw on a good sunny day around 11-2 however it will quickly fall off either side. 75 % of your power comes between the hours of 10 - 2.
on a good day in those months you will achieve over 200 Kwh
Now the bad news
on these good days, the sun will be giving you the low Humidity air you want for drying and you will not really need any heat. Chuck much in and you risk the air condensing in the top of the stack.
On the bad days the solar out put is low but you need the heat. last week August 2018 and again 2020 had no days chucking out 200Kwh in a day
I would certainly not dismiss PV but do use it to feed the fan as well as the heater., and export the surplus when you have it.
your fan will be shifting 30KWh every hour

 

[chickens and wheat]

Ive always wondered if adding an over roof of tin ,then drawing air in under this roof would heat the air at all, tin does get very hot on the right day, usually before sept harvest sadly

 

[Exfarmer]

Ive always wondered if adding an over roof of tin ,then drawing air in under this roof would heat the air at all, tin does get very hot on the right day, usually before sept harvest sadly

There was somebody did this about 20 years ago on a grain store. I think it followed a swedish idea. It certainly is the most efficient way of gaining the solar energy.

 

[renewablejohn]

Ive always wondered if adding an over roof of tin ,then drawing air in under this roof would heat the air at all, tin does get very hot on the right day, usually before sept harvest sadly

Do a google search I think it was an Iowa university thats done a lot of practical work on this.

 

[e3120]

Firstly the good news
your 25 Kw heater will heat 30,000 cu meters of air by 24 degrees according to may best reckoning.
air requires 124.7 KJ of energy to rise by 1C per cubic metre.
So 30,000 X 124.7 = 3,742,320 KJ
your heater chucks out 25,000 KJ/ sec
so 3,742,320/25000 = 149.7 secs to rise one degree and this equates to 24 degree per hour.
This is obviously far more than you need or want , unless it is continuous flow.
The Solar can chuck out easily 40 Kw on a good sunny day around 11-2 however it will quickly fall off either side. 75 % of your power comes between the hours of 10 - 2.
on a good day in those months you will achieve over 200 Kwh
Now the bad news
on these good days, the sun will be giving you the low Humidity air you want for drying and you will not really need any heat. Chuck much in and you risk the air condensing in the top of the stack.
On the bad days the solar out put is low but you need the heat. last week August 2018 and again 2020 had no days chucking out 200Kwh in a day
I would certainly not dismiss PV but do use it to feed the fan as well as the heater., and export the surplus when you have it.
your fan will be shifting 30KWh every hour

I suspect that there's a factor of 1000 out (in the wrong direction) here, as my instinct says this is an awful lot of warmed air. I think the bold above is where it's gone awry.

 

[Exfarmer]

I suspect that there's a factor of 1000 out (in the wrong direction) here, as my instinct says this is an awful lot of warmed air. I think the bold above is where it's gone awry.

Um I think you are right

 

[Exfarmer]

Firstly the good news
your 25 Kw heater will heat 30,000 cu meters of air by 24 degrees according to may best reckoning.
air requires 124.7 KJ of energy to rise by 1C per cubic metre.
So 30,000 X 124.7 = 3,742,320 KJ
your heater chucks out 25,000 KJ/ sec
so 3,742,320/25000 = 149.7 secs to rise one degree and this equates to 24 degree per hour.
This is obviously far more than you need or want , unless it is continuous flow.
The Solar can chuck out easily 40 Kw on a good sunny day around 11-2 however it will quickly fall off either side. 75 % of your power comes between the hours of 10 - 2.
on a good day in those months you will achieve over 200 Kwh
Now the bad news
on these good days, the sun will be giving you the low Humidity air you want for drying and you will not really need any heat. Chuck much in and you risk the air condensing in the top of the stack.
On the bad days the solar out put is low but you need the heat. last week August 2018 and again 2020 had no days chucking out 200Kwh in a day
I would certainly not dismiss PV but do use it to feed the fan as well as the heater., and export the surplus when you have it.
your fan will be shifting 30KWh every hour

Please note these figures are wrong!

 

[Exfarmer]

Sorry start again. I apologise as my figures were out by a factor of 100 ( 1,000 one way and 10 the other )
Your fan is chucking out 30,000 Cu m of air per hour
Air has a weight of 1.246Kg per Cu m.
This gives a total of 37,398 Kg to heat.
Air requires 1.006 Kj to heat 1 Kg of air
a total of 37,622 Kj
so your heater chucking out 25Kw is producing 90,000 Kj per hour divided by 37,622 gives a temperature rise of 2.4 degrees C

These figures are calculated at 10 Degree C. as air gets warmer the weight drops and requires less heat to give the same lift, ie. this heater will achieve a greater lift at 20degree C external temp.
Be also aware that the fans output is normally rates as a free flow figure. pushing air into a heap of grain will produce back pressure and reduce volume , which in turn will increase the temperature rise

thank you @e3120 for pointing out my errors

 

[Neddy flanders]

What’s your peak output likely to be?

my stores pull 2-300 kW‘s per hr of heat to make a difference.

I suspect it will not be worth it, @renewablejohn will have a good answer though

thanks, how big are the stores? are fans ok with that temperature rise going through them? bearings? seals?
what temp rise does 2-300kw get you ?

@Exfarmer thankyou for your time and pointing out ill get a measly 2.4deg rise which wont do alot.

think im on a loser here. might need to find a new idea.
How do I dry 18% grain with a drying floor without burning Gas/Electricity/Diesel ????

 

[Exfarmer]

thanks, how big are the stores? are fans ok with that temperature rise going through them? bearings? seals?
what temp rise does 2-300kw get you ?

@Exfarmer thankyou for your time and pointing out ill get a measly 2.4deg rise which wont do alot.

think im on a loser here. might need to find a new idea.
How do I dry 18% grain with a drying floor without burning Gas/Electricity/Diesel ????

Its a long time since I dried grain, but I think I am correct that 2.4 is about right, as it will not cause condensation in the top of the stack.
perhaps @grainboy knows more

 

[grainboy]

Its a long time since I dried grain, but I think I am correct that 2.4 is about right, as it will not cause condensation in the top of the stack.
perhaps @grainboy knows more

Sorry not a clue,
But I have this too take out soon, it’s a heat exchanger on fan, piped from a large wood chip boiler.

 

[Doing it for the kids]

Sorry not a clue,
But I have this too take out soon, it’s a heat exchanger on fan, piped from a large wood chip boiler.

what size is this please, and size of inlet pipes?

 

[grainboy]

Sorry don’t know exactly, coming with a dismantling project, being undertaken when I can work away,