Can Solar Power Keep My Greenhouse Warm AT NIGHT?

In this video I will explore whether a small DIY Thermal Solar collector using evacuated tubes can make an effective heater for winter gardening n a greenhouse in zone 4. This video is primarily an introduction to the concept of the solar heater as well an explanation of how I built the system. I conclude the video with my heat collection calculations after running the system throughout a sunny day in November.
Note that this solar collector is very small and not located optimally. Here are the key data points from this experiment for those who would like to use it for research or feedback. Note that the final measurement was 1.7 degrees colder than the estimated measurement from the video.
Solar Collector Surface Area: 3.3 sq. ft.
Air temp during operation: 43.5 (low) 51.1 (high)
Hours of direct sunlight (operation time): 5.5
Water volume: 32 gallons
Water starting temp: 51.6F
Water high temp: 64.9F
Net change: 13.3 F (video claims 15 F, which is incorrect)
lbs/gal conversion: 8.35
Final BTU's Harvested: 32(gallon)*8.35(lbs/gal)*13.3 = 3553.8
(Notes: 1. the water volume and weight is approximate; 2. Video claims 4008 BTU, which is incorrect.)
Estimated Solar heat available per sq. ft. at earth's surface: 450 BTU
Advertised efficiency of Evacuated tubes: ~60%
Estimated optimal collection/sq ft. 450*0.6 = 270BTU
Estimated optimal collection for system: 450(max BTU)*3.3(sq. ft)*0.6(eff) = 891 BTU
Estimated cost/kwh= 0.11
Estimated BTU/hr output for 1500watt heater: 5100.
** Tips greatly appreciated! **
DOGE: DLDzoa5qy1ohZPDwBZwe6ePCaCaSMUHJuK

[@lizstokes9091]

Very helpful! I'm planning to build a greenhouse this year.

[@chuanjie2channel978]

Very good technical sharing, like your channel very much, like and subscribe

[@modernfreedom1651]

The video estimates 4008 BTU. I've revised the estimate down to 3553.8 (646 BTU/hr). See video description for details.

[@stevenwright901]

I’d be interested to see if you’d see a pump in power if you put something reflective behind the tubes.
How do you decide when to start running the pump?

[@flamel397]

What do you mean for Air temp? Inside or outside the green house?