Solar Air Heater Performance

I added another fan to my solar air heater and took some measurements to work out how much heating it is producing. On a 16'C cloudy day it was blowing out air at 60'C at 0.01 m3/sec which corresponded to 530W of heating. The maximum temperature I've seen is 85'C which would be 830W. My air flow measurement was pretty rough, so the real values may be higher. My collector is 4.8 x 1.6m so using rough calcs I was expecting more like 4kW.

[@ilijavujicic9958]

I expected more watts from such a big heater. Is this a calculation for the entire heater?

[@agn855]

AFAIK, warm/hot air is streaming upwards by default, while air circulating at a higher speed feels colder (bc of the wind shield factor). Correct me if I'm wrong.

[@irishvoyageur]

I believe you would get substantially more heat output with a higher air flow rate. You are getting a very high delta T (out temp - in temp) but your flow rate is very low. A lot of heat is not getting out of the heating unit.

[@michaels-ideas]

Yes I agree. When I first installed this I didn't leave enough space to install large enough fans. I think my only option is an external fan but my wife would never agree to having anything hanging off the wall.

[@DMonZ1988]

really good, well done! it looks very tidy too.

[@babypower9582]

Yey!! That's a real solar heater :) Good job

[@shelley7466]

I saw how large your collector is and I think that it may be more efficient than your calculation suggested. I know that 1000 watts per square meter would be an ideal condition for input power to the collector when the collector is facing the sun directly. That is not the actual input power when the collector is at an angle to the sun. Your collector is at an angle but I still feel that its efficiency is higher. Maybe the air calculation of air being moved is not correct. Al

[@1willc]

What was the air inlet temperature, how many degrees did it raise?

[@michaelporter000]

On this day it was 60'C outlet temp and around 20'C inlet- so 40'C temperature rise. At best I've seen it do another 25'C so around 65'C temperature rise.

[@chenelson185]

what happens @ night ? nice job

[@michaelporter000]

The issue at night-time is that the cooler temperatures outside can cause the convection currents to reverse direction, i.e. hot air from the room goes into the heater at the top and cold air from the heater is returned back to the room at the bottom, even with no fan running. The fix is to install a flap that opens when the fan runs to push air in the normal direction, but closes (by gravity) to prevent that unwanted reverse air flow.

[@TheGateKeeper]

First!