ASHRAE Journal - April 2021 - 43

TECHNICAL FEATURE

than required because of the generator minimum power
TABLE 5 Comparison of Case A and Case B.
limit (0.6 kW for Case A and 1.8 kW for Case B); someAUTUMN
WINTER
SPRING
times, the electricity demand is lower than the generator
CASE
A
B
A
B
A
B
minimum power limit. There are also electricity losses
1,001
5,202
4,22
1,868
354
1,501
Electricity
in the inverter and batteries.
Consumed (kWh)
-81%
-77%
-76%
According to Table 6, in Case A, around 60% of the
Diesel-Generator
1,173
5,765
210
2,800
370
2,386
supplied heat is recovered from the exhaust air by the
Produced
-80%
-93%
-84%
Electricity (kWh)
air-to-air heat recovery device. Currently, the genera378
1809
70
985
119
860
Diesel
tor is located outside the MMEU, but it might be posConsumed (L)
-79%
-93%
-86%
sible to locate it inside with the exhaust tube and install
955
1,422
193
1,025
298
938
an exhaust gas economizer to collect waste heat and
Diesel-Generator
Work
Time
(h)
-33%
-81%
-68%
decrease the required heat from the heat pump, resulting in reduced electricity consumption.
TABLE 6 The MMEU heat supply for Case A.
According to Table 7, the maximum diesel consumpWINTER
SPRING
AUTUMN
tion for Case A is 8.17 L (2.16 gallons) per day and
Recovered Heat (kWh)
3,114
1,347
1,080
44.7 L (11.8 gallons) per week (the diesel consumpHeat From Heat Pump
tion of the generator is 0.30 L/kWh to 0.35 L/kWh
2,104
804
687
(kWh)
[0.08 gallons/kWh to 0.09 gallons/kWh]) with a mean
Waste Heat from Diesel
2,554
480
803
value of 4.20 L (1.11 gallons) per day during the winter.
Generator (kWh)
During spring and autumn, the PV
TABLE 7 Statistical Results for Case A.
mean electricity production with slope
DIESEL
PV% ELECTRICITY
DAY MEAN
0° is greater than the electricity day
DIESEL DIESEL ENGINE
ELECTRICITY DAY
CONSUMED FOR
PRODUCED VS. AIRFLOW WHEN
CONSUMED
DAY WORK
CONSUMPTION
consumption. This means that part of
7-DAY PERIOD
ELECTRICITY DAY
OCCUPIED
(L/DAY)
TIME (H)
(KWH)
(L)
CONSUMED
(KG/H)
the produced electricity is wasted, so
Min
4.23
1%
103
1.43
3.6
17.2
there is no need to increase the surface
Max
27.25
81%
352
8.17
16.9
44.7
area of PV panels.
Winter
Mean
11.12
16%
173
4.20
10.6
29.4
The airﬂow rate for one person in
SD*
4.93
17%
50
1.37
2.84
7.1
sleeping rooms in barracks (similar to
10
the investigated situation) is 4.0 L/s
Min
1.31
16%
4
0.00
0.0
0.0
or 8.0 L/s11 (63 gpm or 127 gpm per
Max
12.34
741%
168
4.16
10.9
22.2
Spring
person. According to the simulaMean
4.59
269%
75
0.76
2.1
4.8
tion results, the daily mean airﬂow
SD
2.53
203%
44
1.01
2.7
6.1
when the shelter is occupied in winMin
1.29
3%
3
0.00
0.0
0.0
ter is 4.8 L/s to 16.3 L/s (76.1 gpm to
Max
13.44
474%
171
5.07
12.8
27.9
Autumn
258.4 gpm) per person with a mean
Mean
3.89
128%
65
1.31
3.3
8.6
value of 8.0 L/s (126.8 gpm). In spring
SD
2.46
131%
40
1.40
3.7
8.4
and autumn (average values for both
*SD - standard deviation
seasons) the airﬂow is 0.2 L/s to 7.8 L/s
(3.2 gpm to 124 gpm) per person with a mean value of
turn on the diesel generator. The longest diesel genera3.2 L/s (50.7 gpm).
tor operating time during the year is 16.9 h per day with
In this case, the airﬂow rate depends on the outside
8.17 L (2.16 gallons) diesel consumption, and total electemperature. If it is required to provide a constant airtricity consumption (Jan. 15) is 27.25 kWh day. During
ﬂow rate, different control strategies should be applied,
this day, the PV panels produce only 0.74 kWh (2.7%) and
for instance, dynamic airﬂow rate by using air recircuthe average day outside temperature is -19.4°C (-2.9°F).
lation and/or supply air temperature dynamic change
According to Table 8, no need exists to have a higher
based on indoor temperature.
slope of PV panels during spring and autumn because the
In spring and autumn, days exist without the need to
relative decrease of diesel consumption and generator
APRI L 2021

ashrae.org

ASHRAE JOURNAL

http://www.ashrae.org

ASHRAE Journal - April 2021

Table of Contents for the Digital Edition of ASHRAE Journal - April 2021