January 2024 - 18

SGAFT
The left set of bars shows total minutes of burn time/
hour with burn time (fuel consumption) increasing as
outdoor temperature decreased from 35º F to 28º F to
12º F. Burn time increased from roughly 10 to 13 to 16
minutes/hour as outdoor temperature fell. Between the
warmest night (35º F) and coldest (12º F) the total minutes
of burn/hour increased 59% (10.3 to 16.4 minutes).
The center set of bars presents furnace cycles/hour
and shows cycles increased as outdoor temperature
18
16
14
12
10
8
6
4
2
Figure 1.
20
18
16
14
12
10
8
6
4
2
Figure 2.
6
5
4
3
2
1
Figure 3.
4
3.5
3
2.5
2
1.5
1
0.5
35
Figure 4.
18
JANUARY 2024 GPNMAG.COM
28
12
AVG BURN MIN/CYCLES CLOSED
AVG BURN MIN/CYCLES OPEN
2.9
2.7
2.7
2.8
3.4
2.9
CYCLES/HR OPEN
5
4.3
3.4
CONCLUSION
Energy curtain use in this small greenhouse study
35
28
12
reduced fuel consumption by 20-22%. Differences
were observed over both main variables; three outdoor
temperatures (35º F, 28º F, 12º F) and two curtain
positions (open versus closed).
This report continues at sgaft.com with the second
part of the study. Additional pictures and data are
discussed as well as an interpretation of the entire
study's science from my perspective as a commercial
greenhouse owner/operator.
Konjoian's Horticulture Education Services created SGAFT to
serve the unique needs of small greenhouse and farm operations.
Peter Konjoian's unapologetic mission for the project is to help
fellow small growers integrate complementary technologies,
appropriate at their operational scale, to maximize profitability.
4
CYCLES/HR CLOSED
5.4
4.9
MIN BURN/HR CLOSED
MIN BURN/HR OPEN
14.5
11.5
9.1
11.3
18.2
14.5
16.4
12.9
10.3
3.9 4.5
5.2
2.7 2.9 3.1
MIN BURN/HR
CYCLES/HR
AVG BURN/CYCLE
35
28
12
decreased. As temperature dropped from 35º to 28º F
the furnace required 0.6 of an additional cycle to
maintain temperature and another 0.7 of a cycle as
temperature dropped from 28º F to 12º F. The right
set of bars shows average cycle burn time in minutes,
which also increased as the temperature fell but less
dramatically. Allowing for rounding of numbers, within
each temperature minutes of burn time/hour = cycles/
hour x average burn time/cycle.
CURTAIN OPEN VERSUS CLOSED
Figure 2 shows total minutes of burn/hour for the
three-night temperatures with the curtain open (purple
bars) versus closed (green bars). At 35º F the curtain
open versus closed split was 11.5 versus 9.1 minutes,
a 21% reduction. At 28º F the 14.5 versus 11.3 split was
22%, and at 12º F the 18.2 versus 14.5 split was 20%.
Closing or " using " the curtain resulted in 20-22% less
fuel consumption.
Figure 3 shows the number of furnace cycles/hour for
35
28
12
the three-night temperatures with the curtain open or
closed. At 35º F and 28º F closing the curtain reduced
the number of heat cycles by about one cycle/hour. At
the lowest temperature of 12º F, the curtain reduced the
heat cycles by one half of a cycle/hour.
Figure 4 presents minutes of burn time/cycle which
was minimally affected through the warmer nights of
35º F and 28º F by curtain position. However, through
the coldest night, 12º F, cycle burn time increased by
half a minute when the curtain was open versus closed.
Reciprocally, during warmer nights closing the curtain
did not significantly reduce the furnace's burn time/cycle
but on the cold night closing the curtain resulted in a
shorter cycle time.
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January 2024

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