Welcome to the Solar Collector
Brainstorming and Development Page!


 

Home

Hot Air Collector

Hot Water Project 1

Hot Water & Space Heating

Solar Electric

Solar Construction 101

FAQs

Best Collectors

Simply Solar
Sign up Latest Topics
 
 
 


Reply
  Author   Comment   Page 1 of 2      1   2   Next
Irishvoyageur

Registered:
Posts: 31
Reply with quote  #1 
The attached file shows the construction details of my 18 ft x 2.5 ft solar air heater. I have been using it for the past month and it is working well (at least when it is sunny).

Thank you for all the previous builds which I used to design and construct my heater.


 
Attached Files
pdf Solar Air Heater JFS.pdf (3.59 MB, 38 views)

gbwillson

Avatar / Picture

Super Moderator
Registered:
Posts: 2,425
Reply with quote  #2 
Thanks for posting John!

It looks really well built, with a lot of thought put into it. I split the difference on your output numbers and calculated your BTU output to be roughly 8,400BTU's! That's almost as much heat as TWO electric space heaters!! 

A couple of questions:I'm curious about the SensorPush wireless thermometer on your intake. I've had one saved in my Amazon basket for over a year and I wondered what your thoughts were on it. I'd like to get one for each end of my collector so I can track and calculate my output numbers automatically.

Another question is your fan. It's a powerful radiator fan, but it's output is only 25% of the rated. While not a big problem since you obviously wanted a fan to fit inside the wall space. But is it loud? Such powerful fans in an enclosed space from my experience can be pretty loud. 

Greg in MN

 
Irishvoyageur

Registered:
Posts: 31
Reply with quote  #3 
Thanks, Yes I've consistently been getting about 8,000-9,000 BTUs during mid-day sunshine. I can get it up to about 10,000-11,000 BTU when pushing the fan at it's maximum output. However, the noise level would be objectionable and the fan life would likely be less. The fan is normally drawing about 3-4 amps at full sun (40-50 watts) with my two 60watt panels.  The fan is not objectionably loud at those conditions. The fan noise is mainly confined to the porch. The fan is rated at 80watts (~13 volts at 6 amps). I have attached a graph showing the estimated air flow rate vs the fan's current draw FYI.

I have been very impressed with the Sensor Push Sensors. I have three of them. One of them would not work at temperatures above ~115F, but the company quickly provided a replacement unit. I have the Gateway unit as well which allows me to access the temperature sensors with my iPad or computer using a WIFI connection.  That's great since I can monitor the input and output temperatures remotely.


Attached Images
png Air flow vs current JFS.png (118.97 KB, 49 views)

Irishvoyageur

Registered:
Posts: 31
Reply with quote  #4 
Note, the airflow is measured at the outlet of the solar air heater. The output is less than its 800 cfm rating due to pressure losses within the solar air heater and air filter which is mounted just before the fan.

gbwillson

Avatar / Picture

Super Moderator
Registered:
Posts: 2,425
Reply with quote  #5 
John-

Does the software log data for each sensor individually, or can it log your DeltaT automatically? I'd love to be able to log performance data automatically since I know the CFM output through my system. 

Also, if your fan noise ever got to be too much, or you needed a bit more CFM you could use a larger diameter fan. Since your intake to the collector doesn't have a duct, there is no need to limit the intake opening to your 6.5" hole. You could have a fan as large in diameter as the spacing between the studs. The larger fan should give more CFM's at a lower noise level since it would move more air than the smaller fan at a given wattage.

Greg in MN
Irishvoyageur

Registered:
Posts: 31
Reply with quote  #6 
The Sensor Push sensors are logged individually. The data can be downloaded and calculations run in a spreadsheet. I am not aware of automatic methods of getting a temperature difference between two sensors. I am not sure how long the data is stored by the Sensor Push "cloud". I know I have data going back to January.

Right now, I am not too excited about making a larger holes in my porch walls. I can live with the existing noise levels and not worried about maximizing the BTU output.  I have 16 inch, 12 volt, 120watt fan that I plan to mount in the window between the porch and main house. That will be powered by a 160 watt panel and I have a power width modulator on it to control the fan speed. That fan sounds like a high powered drone when run at maximum speed.
Bruce

Registered:
Posts: 143
Reply with quote  #7 
Really nice project and great presentation!  I like the simplicity of the ducts...no loss efforts there!  I like the solar powered fan, too! How do you control fan speed?  Just let it run at whatever speed the sun provides power for?  I don't understand how the sensors are connected and how the fan is controlled.  I am not very versed in solar electric power controls.

Bruce
stmbtwle

Avatar / Picture

Registered:
Posts: 3,002
Reply with quote  #8 
John that's a very impressive unit. I had thought of putting a PV panel inside a collector, vut never tried it.

Bruce, can't speak for John's unit but generally you can connect it directly to the solar panel and let it run. A snap switch is a good idea to keep the fan off until the collector comes up to temperature. I built a temperature-responsive speed control and while it works, it's probably overkill.

__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Irishvoyageur

Registered:
Posts: 31
Reply with quote  #9 

Bruce - The solar panels power the fan at variable speeds directly related to solar radiation (sun light). The fan comes on at about a power of 10 watts just as the heater is heating up.  The fan reaches its maximum speed at solar noon when the fan is consuming about 50-60 watts of power and the heater is very warm. I have the option of adding a snap switch but see no need under the current operation. If I went with a constant power source (battery or other power supply) I would then add a snap of switch to power the fan when the unit was warm and allow it to run continuously until the lower temperature limit set would turn off the circuit (shot off fan).

I had to add a second solar panel due to the heater's length and shading by my neighbors trees. Also, I wanted more power to increase the air flow. The left (west) side of the heater would heat up before the solar panel inside the unit on the right side (east) was receiving adequate solar radiation to power the fan. I do loose some power having the panel inside the box since the glazing would reduce the transmission of light (about 20%).  However, the panel was a convenient means for providing the backing for an air plenum for the air intake. The panel in the window on the porch produces abit more power, even though it is the same size and make as the unit inside the heater (60 watts by Newpowa). 

The fan would run faster with more power since it is rated at 80 watts. However, the noise level is more objectional at maximum output.

 

gbwillson

Avatar / Picture

Super Moderator
Registered:
Posts: 2,425
Reply with quote  #10 
I'd love to rig up one of my collectors using a solar panel to power the fan(s). But I need 400CFM or more out the exhaust, so I would need a large panel to power a row of smaller fans. A radiator fan setup like John is either too noisy or doesn't move nearly enough air. 

I like how John's setup is somewhat automated. Slower fan speeds during early and late day sun and semi cloudy days. And max speed during very clear, middle of the day operations. I do think a snap switch might be needed otherwise the fans might run if on a bright, but cloudy day when the heater isn't getting very warm. 

Greg in MN
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

 

web statistics