Heating with solar panels instead of infrared radiants...

[rin67630]

The idea may sound crazy, but I think, it is very serious: Using solar panels to occasionally heat a home / tinkering barn.
It is known, that solar cells are basically LEDs. These LEDs emit light in the infrared spectrum when provided with enough forward current.

Infrared radiants are efficent to give a warmth feeling in cold rooms used only occasionally.
I believe solar panels should emit more Infrared than just heating resistors at the same energy, since a good portion of the infrared emission is electronically generated and not inefficiently from black matter radiation.

It is already possible to de-snow panels by feeding current into the panels, so heating with panels is already done.
Now solar panels are so damn cheap that a 400W panel is actually cheaper than an infrared heater of the same size.
What about using them as home heaters?

Let us start the discussion...

 

[timselectric]

I believe that they would damage themselves. If allowed to get warm enough to provide any useful heating.

 

[rin67630]

I believe that they would damage themselves. If allowed to get warm enough to provide any useful heating.

They should not get warmer than their operation temperature. The infrared will come from the LED emission, not from the thermal radiation.

 

[timselectric]

Give it a shot. Panels are cheap.
Just keep an eye on it.

 

[hwy17]

Resistance heating is 100% efficient and dirt cheap, so is there really any basis to believe a panel could top that? Only a heat pump can go "over 100%".

 

[rin67630]

Resistance heating is 100% efficient and dirt cheap, so is there really any basis to believe a panel could top that?

I'm afraid you did not get the point.
We are not speaking about heating a whole room with all its walls and the mass of air contained. That requires a lot of energy.
We speak about infrared radiation, used to increase (temporarily) the thermal comfort in else unheated or less heated rooms.
I believe a solar panel can top a plain electric thermal IR radiant. And is even cheaper.

 

[hwy17]

But if both are 100% efficient than what does it beat a radiant heater in, infrared vs convection percentage?

 

[rin67630]

But if both are 100% efficient than what does it beat a radiant heater in, infrared vs convection percentage?

A thermal radiant IR panel is not 100% efficient, far from that !
Most of its energy is NOT infrared, but heat.
We don't want to heat the air, but make a stay in an else colder room comfortable.
An example is a bathroom, where you just don't want to freeze after a shower.
Or a barn, where you go sometimes tinkering for half an hour.

 

[Bob B]

A thermal radiant IR panel is not 100% efficient, far from that !
Most of its energy is NOT infrared, but heat.
We don't want to heat the air, but make a stay in an else colder room comfortable.
An example is a bathroom, where you just don't want to freeze after a shower.
Or a barn, where you go sometimes tinkering for half an hour.

I would be very interested to see the result of experiments .... I have been interested in the effects of radiant heat for a long time.

Most people simply underestimate the importance of radiant heat. People are schooled to think about room temperature ... It's easy to measure.
I have seen people complain of being cold when sitting in a warm room .... but at the same time, there is a cold window ... and they fail to realize that their body will radiate heat directly to that cold window even if the room temperature is 80 degrees.

The company I used to work for once did a large scale radiant heat energy savings project in a factory environment. Large radiant heaters were strategically placed 30 or more feet above the factory floor and the air temperature of the space was only controlled to keep things from freezing.
It was pretty amazing how comfortable it was in the dead of winter .... you could walk around in short sleeves with the air temperature below 50 and be perfectly comfortable .... and the energy savings ... compared to previously attempting to keep the air temperature comfortable was very significant.

The effects of radiant heat are highly under rated.

 

[rin67630]

I would be very interested to see the result of experiments .... I have been interested in the effects of radiant heat for a long time.

One would need to have a serious calibrated IR thermograph to make a correct evaluation. A bit outside my tinkering budget.

 

[yodamota]

Did this ever take form? any results? I am quite suprised how much infrared panels cost.

 

[Hedges]

Now solar panels are so damn cheap that a 400W panel is actually cheaper than an infrared heater of the same size.
What about using them as home heaters?

What do you mean by "same size"?

Have you conducted any tests on power dissipation of PV panels when supplied with an external electrical source? On IR emissions vs. conducted/convected heat?

"New panels are ... cheap", yeah, but used panels are even cheaper.
And which really is the more efficient IR radiator? An older less efficient PV panel, or a new more efficient one?

I still remember an experience half a century ago at the Exploratorium (San Francisco), where an electric heating element was reflected by a parabolic mirror. Placing your hand at the focal point, the IR it delivered was concentrated.

Rather than large format IR source radiating 180 or 360 degrees, consider a smaller source focused on the "object" you wish to heat.

 

[hogback]

Just sit in an induction coil.....

 

[KITROBASKIN]

https://www.costco.com/presto-heatdish-plus-tilt-parabolic-heater.product.100805849.html

Has a ‘thermostat’ on the upper part of the dish. Our Victron 24V 1200VA shows it using around 1200 instead of claimed 1000W.

 

[webbbn]

A thermal radiant IR panel is not 100% efficient, far from that !
Most of its energy is NOT infrared, but heat.
We don't want to heat the air, but make a stay in an else colder room comfortable.
An example is a bathroom, where you just don't want to freeze after a shower.
Or a barn, where you go sometimes tinkering for half an hour.

Heat is infrared. It's just toward the lower-end of the spectrum and doesn't project as well as the shorter wavelength that are produced by radiant heaters, which are more in the SWIR-MWIR wavelengths.

 

[rin67630]

Have you conducted any tests on power dissipation of PV panels when supplied with an external electrical source? On IR emissions vs. conducted/convected heat?

The power dissipation must be exactly the amount of power fed to the panel. Additionally a certain percentage should be IR light emission from the cells like every LED does.

 

[Hedges]

Yes, power dissipation will equal power delivered, and power emitted will equal that when it reaches steady state.

My question is, do you know what the I/V curve of a PV panel is? I mean when you apply voltage to its leads, not when you expose it to light (which is available from data sheet.)

Also, have you determined what fraction is emitted as IR vs. applied voltage? If you want IR radiators to keep yourself warm rather than heating the air, IR emission efficiency will matter, and the PV panel may be much poorer than a glowing heating element.

 

[grizzzman]

Dasian at ElectroDacus has been doing this for a long while. If you are wanting info go to his site (or for that matter) in this sites info on the ElectroDacus SBMS0 PDF.

 

[rin67630]

Yes, power dissipation will equal power delivered, and power emitted will equal that when it reaches steady state.

My question is, do you know what the I/V curve of a PV panel is? I mean when you apply voltage to its leads, not when you expose it to light (which is available from data sheet.)

Also, have you determined what fraction is emitted as IR vs. applied voltage? If you want IR radiators to keep yourself warm rather than heating the air, IR emission efficiency will matter, and the PV panel may be much poorer than a glowing heating element.

The panel should get constant current, at iMax from the spec.
And I believe the IR radiation will be better than a glowing heating element that loses a lot in heat before generating IR radiation.

 

[Hedges]

Enough with the theory, already. I did that, once upon a time.

Take one of your PV panels, push iMax (Isc?) through it. Come back and tell me how much voltage was required. And measure IR if you can.

As for the glowing element, what if that was in a vacuum? Or in a gas, but with a couple layers of glass window and gas between (narrow enough to prevent convection between the panes.)