Sunday, December 13, 2009

Winter Update

It's been awhile since I've posted any updates about the greenhouse. We're now in the blistering cold of winter. This is the first year I've heated the may be a costly mistake. Here's a little scientific data to ponder:

From Misc

1) 2:30pm: Sun starts to set (yellow) and the greenhouse has no solar gain and the temperature starts to drop (Orange & green lines)

2) 3:45pm: Temperature goes below 40F (4.5C). Heater is able to turn on/off as it maintains the temp at 40F. Ceiling temp (light green) jumps a bit as the heat rises....

3) 9:15pm: Outside temperature (Red) goes below 20F (-6/7C) and the heater no longer can keep up with the demamd. Temperature slowly declines to around 38F (3.3C). The outside temp is 13.3F (-10.4C)

4) 9:15am: Heater turns off once the sun comes out the next morning. Total run time is roughly 17 hours.

There are 2 electric heaters totaling 2400 watts. After all the fees and taxes, we pay $0.20 per kilowatt:
2400watts & 17 hours = 40.8 kilowatts
40.8kW * 20 cents = $8.16 to keep it heated for the night!

Since we are getting so little sun and it's cold, the lettuce is growing very slowly. There's one tomato plant that I started in the fall still doing OK but needs a lot more light. I had a few cukes growing, but the consistent cold has killed them. I am not generating $8 worth of veggies/day. Perhaps it's time to invest in a propane heater to lessen the heating costs....or just shut it down for the winter..... Jan & Feb will be even colder!