30-65%Forecasted energy savings compared to a traditional dehumidification system.
ENERGY savings
WESTERN COOLING EFFICIENCY CENTER-UC DAVIS : CASE STUDY
WESTERN COOLING EFFICIENCY CENTER » wcec.ucdavis.edu
LABORATORY TESTING OF AN ENERGY EFFICIENT DEHUMIDIFIER FOR INDOOR FARMS
Laboratory test at the Western Cooling Efficiency Center-UC Davis
100%Amount of water removed from the air that can be re-used to water plants.
Water re-use
WESTERN COOLING EFFICIENCY CENTER
PROBLEMIn order to remove moisture and heat generated by plant transpiration and
lighting, indoor farming operations require dehumidification and sensible cool-
ing. However, the ratio of dehumidification to sensible cooling needed exceeds
typical requirements for residential or commercial buildings. Energy intensive
dehumidification systems are often necessary to maintain the indoor condi-
tions required for indoor farming.
SOLUTIONTraditional dehumidification systems provide dehumidification and increase the
air temperature, as opposed to the desired dehumidification and reduction of
air temperature. An alternative is MSP Technology’s dehumidification system
that uses a plate air-to-air heat exchanger and a cooling coil that is part of a split
compressor-based refrigeration system.
This process results in a ratio of sensible to latent cooling that is well suited
for indoor farming applications. Experimental laboratory testing and numeri-
cal modeling were performed to estimate the annual projected energy savings
from using MSP Technology’s dehumidification system over a traditional dehu-
midification system. The results of this project forecast that implementation of
MSP Technology’s system has potential to save 30% or more of the energy used
for dehumidification and cooling in indoor farming applications.
Assistant Engineer Derrick Ross instrumenting the MSP Dehumidifier in WCEC’s environmental chamber.
2 | WCEC | CASE STUDY DEHUMIDIFICATION TECHNOLOGY PERFORMANCE TESTING
A. STANDARD DEHUMIDIFIER B. AIR CONDITIONER
ADD WATERADD WATER ADD HEATADD HEAT
AA BB REMOVE HEATREMOVE HEAT
C. MSP DEHUMIDIFIER B. AIR CONDITIONER
ADD MOISTUREADD MOISTURE ADD HEATADD HEAT
CC BBADD HEATADD HEAT REMOVE HEATREMOVE HEATREMOVE HEATREMOVE HEAT
RECYCLE WATER
(IF PLUMBED)RECYCLE WATER
RECYCLE WATER
(IF PLUMBED)
RECYCLE WATER
A. STANDARD DEHUMIDIFIER B. AIR CONDITIONER
ADD WATERADD WATER ADD HEATADD HEAT
AA BB REMOVE HEATREMOVE HEAT
C. MSP DEHUMIDIFIER B. AIR CONDITIONER
ADD MOISTUREADD MOISTURE ADD HEATADD HEAT
CC BBADD HEATADD HEAT REMOVE HEATREMOVE HEATREMOVE HEATREMOVE HEAT
RECYCLE WATER
(IF PLUMBED)RECYCLE WATER
RECYCLE WATER
(IF PLUMBED)
RECYCLE WATER
MOIST RETURN AIR
DRY SUPPLY AIR
EVAPORATOR
PLATE HEAT EXCHANGER
1
2
3
4
MSP DIAGRAM
ABOUT THE TECHNOLOGY TEST METHODOLOGY
15.6 21.1 26.7 32.2 37.8 43.3 48.9 54.4Ambient Temperature (°C)
15.6 21.1 26.7 32.2 37.8 43.3 48.9 54.4Ambient Temperature (°C)
1
2
3
4
5
6
7
10,000
20,000
30,000
40,000
50,000
60,000
70,000
Tota
l Pow
er (k
W)
Capa
city
(BTU
/hr)
Capacity DR-55
Capacity R-410A Total Power R-410A
Total Power DR-55
60 70 80 90 100 110 120 130Ambient Temperature (°F)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.060 70 80 90 100 110 120 130
15.6 21.1 26.7 32.2 37.8 43.3 48.9 54.4
COP
DR-55 R-410A
Ambient Temperature (°F)
Ambient Temperature (°C)
0%
20%
40%
60%
80%
100%
120%
0
1
2
3
4
5
6
7
60 70 80 90 100 110 120 130Ambient Temperature (°F)
COP
Ratio
DR-
55 /
R-4
10A
COP
R-410A COPDR-55 COP COP Ratio
Traditional dehumidifiers (Figure 1) remove moisture by
cooling the air below the dewpoint using an evaporator coil,
resulting in cold, dry air. The cold, dry air is then re-heated as
it passes over the condenser coil, supplying warm, dry air to
the space. The net result is an addition of heat into the condi-
tioned space. This requires another air conditioning unit to be
installed to remove both the heat from the lights and the heat
from the dehumidifier.
The MSP dehumidifier (Figure 2) combines a plate heat
exchanger, evaporator coil and a small, outdoor condensing
unit. This technology (Figure 3) brings in (1) moist return air
through a (2) plate heat exchanger to initially cool the return
air. This allows the (3) evaporator coil to focus most of its
energy on dehumidification, instead of both cooling and de-
humidification like a traditional dehumidifier. The cool dry air
then passes back through the plate heat exchanger to reduce
the temperature of the incoming moist return air and pick up
some of the heat as it is then (4) reintroduced into the condi-
tioned space. The heat absorbed by the evaporator coil and
from the compressor is rejected outside. The net result is dry
air delivered to the space with a small reduction in tempera-
ture, which counteracts the heat from the lights. A building
conditioning system for heating and cooling is then used to
make minor adjustments to space temperature as needed.
Characterizing MSP’s Performance
The unit was instrumented and tested in WCEC’s environmental
chambers to determine system power, capacity, and efficiency for
each of 29 steady-state tests conducted at controlled outdoor air
temperatures, indoor conditions, and indoor airflows.
Comparison to Traditional Dehumidification Systems
In order to estimate the difference in energy expenditures of MSP
Technology’s dehumidification system compared to a traditional de-
humidification system as applied to an indoor farm, WCEC created
two numerical models based on:
• Indoor building loads from plant transpiration and lighting
• Hourly weather forecast data
• Equipment performance data
The models calculated the annual energy expenditures of each
dehumidification system required to meet the humidity set point for
the greenhouse, as well as any additional energy expenditures nec-
essary to recondition the air to the desired indoor air temperature
after dehumidification loads were met. The difference in the energy
expenditures per square foot as well as the percent difference in
energy expenditure per square foot were calculated.
Figure 1: Traditional Dehumidification and Conditioning Strategy/Loads Figure 2: MSP Dehumidification and Condtioing Strategy/Loads Figure 3: MSP Diagram of Operation
WESTERN COOLING EFFICIENCY CENTER » wcec.ucdavis.edu
The Western Cooling Efficiency Center was established
along side the UC Davis Energy Efficiency Center
in 2007 through a grant from the California Clean
Energy Fund and in partnership with California Energy
Commission Public Interest Energy Research Program.
The Center partners with industry stakeholders to
advance cooling-technology innovation by applying
technologies and programs that reduce energy, water
consumption and peak electricity demand associated
with cooling in the Western United States.
ABOUT WCEC
Theresa PistochiniEngineering Manager
Robert McMurryAssistant Engineer
Derrick RossAssistant Engineer
Paul FortunatoOutreach Manager
Western Cooling Efficiency Center
University of California, Davis
215 Sage Street #100
Davis, CA 95616
0
200
400
600
800
1000
1200
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25
Ener
gy E
xpen
ded,
Tot
al (k
Wh/
ft2 )
Ener
gy E
xpen
ded,
Tot
al (k
Wh/
ft2 )
Latent Cooling Load, Watering and Transpiration (gal/ft2/day)Traditional Dehumidification System MSP Technology's Dehumidification System Traditional Dehumidification System MSP Technology's Dehumidification System
0
20
40
60
80
100
120
140
160
180
200
1.7 1.9 2.1 2.3 2.5 2.7 2.9
Energy Factor of Traditional Dehumidification System (L/kWh)
Climate: DenverTraditional dehumidification system e�ciency: 2.3 L/kWh
Climate: DenverLatent cooling load: 0.25 gal/ft2/day
RESULTS
Figure 4: Latent load from watering and transpiration versus annual energy expended for dehumidification and reconditioning of air
The results for the city of Denver, Colorado have been summa-
rized and presented to demonstrate the relationships studied.
• Energy expended per square foot as a function of latent
cooling load, which is affected by plant type, spacing, water-
ing and lighting schedules (Figure 4). Increasing latent load
increased the total energy expended for both systems and
decreased the percent energy savings attainable from MSP
Technology’s Dehumidification system, although in all cases
the projected energy savings was greater than 30%.
• Energy expended per square foot as a function of the energy
factor of the traditional dehumidification system. The expect-
ed savings from MSP Technology’s Dehumidification System
decreased as the efficiency of the traditional dehumidifica-
tion system efficiency increased, however, the savings in all
three scenarios was more than 50%.
RECOMMENDATIONSWCEC recommends conducting field testing of the technolo-
gy to further assess and quantify the energy savings that can
be achieved with the new MSP Technology’s dehumidification
system. Due to the recent legalization of recreational cannabis in
California, there is a pressing need to address energy efficiency in
indoor farming operations.
Figure 5: Traditional dehumidification system energy factor versus annual energy expended for dehumidification and reconditioning
of air
PREPARED BY