9/13/19 – Day 10 – Boise, ID – Solar Cooker

Still waiting for my replacement bike spokes to arrive from Seattle. I’m enjoying a nice cup of hot Jasmine tea that I made in my portable solar cooker. The video shows how it works.

Solar Tea Calculation

The sun gives us about 300 BTU’s per sq. ft. per hour* 

The reflective area of my cooker is about onesquare foot

So we can expect 300BTU’s per hour

One BTU (British Thermal Unit) is the amount of energy needed to raise one pound of water one degree F

Water from the tap comes out at 50 F, so to bring it to the boiling point of 212 F we will need a temperature rise of 172 degrees F. My copper tube filled with water weighs 1.5 pounds

By multiplying 1.5 x 172 = 258 BTU’sneeded to boil the water

Since my cooker will deliver 300, the water should be boiling in an hour.  

*NOTE:  300 BTU/HR. is peak sun.  Since it’s early morning and the sunlight is passing through more atmosphere, our input energy will only be about 75% of peak.  Still, in just over an hour we should be able to make tea.