COLLABORATION FOR AQUAPONICS SUSTAINABLEENERGY
Design and Modeling of Combined Heat and Power Systems for
Sustainable Urban Agriculture and Aquaculture
Team Members: Ben Steffes Dan Neumann Brandon Jackson Nate Weber Chris Chapman
Faculty Advisor:Dr. Chris Damm
Milwaukee School of Engineering
AQUAPONICS OVERVIEW
Borrowed from: http://www.photosbysc.com/Aquaponics/Saras_Aquaponic_Blog/Entries/2008/4/13_What_is_Aquaponics_files/droppedImage_1.png
CHP OVERVIEW
CHP Combined Heat and Power One fuel source for multiple types of output
power Electricity Thermal Energy
High overall efficiency
Fuel
Electrical
Thermal
CHP System
OUR GOALS…
Develop models to guide in the development of an advanced energy system for aquaponics
System level design of an environmentally responsible and economical system capable of reducing carbon emissions through higher efficiency
Create a simulation tool to aid in the designing and selection of aquaponics energy systems
DESIGN CONSTRAINTS: AQUAPONICS
Greenhouse Environment between 45-60%
relative humidity and 55°F-85°F
Rearing Tank sizes ranging from 1,000-20,000
gallons
Maintain Tank Temperature Between 75°F-85°F
Consider both natural and artificial lighting
DESIGN CONSTRAINTS: POWER PRODUCTION
Provide power to aerate, heat, and pump tank water
Provide power for artificial lighting
Operate on Natural Gas
Continuous Operation With Exception for Maintenance
Less CO2 emissions than Milwaukee Emission Statistic
Lowest Cost/Least Environmental Impact
INITIAL PLANS
Mechanical Natural Gas Engine with Heat Exchangers
Supply mechanical demand for: Pumps Blowers
Heat exchangers to Provide heat for aquaponics tank(s)
Electrical Commercial CHP generator set
Supply electricity for: Pumps Lighting
Provide heat for aquaponics tank(s)
ELECTRICAL VS. MECHANICAL Engine Trouble
Introducing lubrication (2-stroke) Maintenance cycle
Space requirements Efficiency of Heat Exchangers
MOVING FORWARD WITH ELECTRICAL SYSTEM
Took system level approach to pairing CHP and aquaponics using commercially available CHP generators
Selected Marathon ecopower
Borrowed from: mathonengine.com
MARATHON ECOPOWER Estimated installed system cost approximately
$35,000 4000 hour maintenance intervalSpecificationsElectrical Power 2.0 – 4.7 kWThermal Power with max. flow temp. 167 °F [75 °C]
6.0 – 12.5 kW
Overall Efficiency >90% (approx. 25% electrical + approx 65% thermal)Engine Single-Cylinder, 270 cm3, 1,700 – 3,600 rpmExhaust Gas Figures [at 5% O2] NOx < 1.98 mg/ft3 CO < 11.33 mg/ft3 Temp < 194 °F [90 °C]Grid Feed [Single Phase] 250 VAC, 50/60 Hz, Power Factor = 1Sound Level < 56 dB [A]Dimensions/ Weight 54 in. L x 30 in D x 43 H 858 lbApprovals CE – Certificate, ETL - Approved
THERMAL MODELING
CHP system sized for thermal load Point of most efficient operation
Model used to approximate thermal loading Surface convection and evaporation, wall convection, base
conduction, and hydroponic tank losses
, ,w w wT h p
Water Level
, ,a aT p P,evap surfq ,conv surfq
,conv wallq
,cond baseqGround
Atmosphere
gT
Evaporation (Two Models) (R.V. Dunkle 1961) Based on model of distillation pond
evaporation
(W.S. Carrier 1918) Empirical model based on indoor swimming pools
Surface Convection Related to surface evaporation (I.S. Bowen 1926)
0.00494314.7
c w a
e w a
q T T P
q p p
1 3
0.0254 46039w a
e w a a w a wa
p pq T T T p p h
p
98.7 0.430.491 w a
fg
VG p p
h
Wall Convection Based on non-dimensionalized analysis of flat plate
convection
Hydroponics Tank Losses
1/3
L LNu 0.13 Gr Pr 2 3 2LGr g L T
LNu hL k Pr pC k
, tangrowbed growbed p water k returnq m c T T & &
PSYCHROMETRIC CHAMBER TESTING
Trial 1 Trial 2Tank water temperature (F) ~72 70Atmospheric temperature (F) 50 60Relative humidity (%) 50 31Total run time (min) 100 210
0 0.5 1 1.5 2 2.5 3 3.540
60
80System Temperatures
Tem
per
atu
re [
F]
WaterAtmospheric
0 0.5 1 1.5 2 2.5 3 3.50.25
0.3
0.35System Relative Humidity
Hu
mid
ity
[%]
0 0.5 1 1.5 2 2.5 3 3.50
200
400System Input Power
Time [hr]
Hea
ter
Po
wer
[B
TU
/hr]
Raw Power InputAveraged Power Input
0 0.5 1 1.5 2 2.5 3 3.50
0.02
0.04
0.06
0.08
0.1
0.12
Time [hr]
Eva
po
rati
on
[lb
m/h
r]
Evaporation Rate Over Time
R.V. DunkleW.H. CarrierActual Mass Loss
0 0.5 1 1.5 2 2.5 3 3.5-200
-150
-100
-50
0
50
100
150
200
Time [hr]
En
erg
y [B
TU
/hr]
System Energy
Surface Evaporation (Predicted)Surface Evaporation (Actual)Heater Power (Actual)Surface Convection (Actual)Surface Convection (Predicted)Water TransientTank Wall Convection (Predicted)
, , ,water
conv surf in evap conv wall p water
dTq q q q mc
dt & & & &
THERMAL LOAD PROFILE
Property Value UnitsTank Temperature 80 FGreenhouse temperature
70 F
Relative Humidity 50 FFlow Rate 67 GPM
Return Temperature 78 FTank Size 7 width
3.5 height 30 length
Ft
Number of Tanks 2Rubber Liner 0.25 InchLumber 1.5 InchR7 Foam Insulation 1.5 Inch
16% 2%
1%
81%
0%
Thermal Losses For Aquaponics System
Surface Evaporation Surface ConvectionTank Wall Convection Gardening Losses
AQUAPONIC SYSTEM PROPORTIONING University of Virgin Islands (UVI)
Raft Style Commercial System
Proportioning Hydroponic Tank to Rearing Tank Hydraulic Loading Rate Retention Time Feed Rate
POWER REQUIREMENTS Pumping
Centrifugal Pump 45% Efficiency (elec.-water)
Rearing Tank Aeration Greater Stocking Density Regenerative Blower
64% Efficiency (elec.-water)
Artificial Lighting Implemented in few cases 18 Hr daylight grow period Faster Plant Growth
Volumetric Flow*Pressure Difference
Electrical Power
POWER CALCULATION METHODS
SYSTEM HEAT & POWER REQUIREMENTSSIZED SYSTEM FOR MARATHON ECOPOWER(11000 GALLON)
UNIVERSITY OF VIRGIN ISLANDS SYSTEMUSING DEVELOPED PROCEDURE (8240 GALLON)
System Calculated Power:Pumping: 0.64 Hp (460 W)Aeration: 1.44 Hp (1.06 kW)Lighting: 43.8 Hp (32.7 kW)Thermal: 39000 Btu/hr
(11.43 kW)
Calculated Power:Pumping: 0.50 Hp (370
W)Aeration: 1.1 Hp (800 W)Lighting: NoneThermal: None
UVI System:Pumping: 0.50 HpFish Tank Aeration: 1.5
Hp
RESULTS OF ECONOMIC ANALYSIS
Conditions: $35,000 installed
system cost Analysis uses current
utility pricing CHP system run using
thermal load following Net metering 1:1 Replaces 75%
efficient natural gas water heater
Results: 31,000 kWh Electricity
Generated Annually 83,000 kWh Water
Heating Using 462,000 cu.ft
natural gas ($4,300) $3,000 Annual Benefit 12 year simple payback 10 year payback with
3% inflation No incentives applied
RESULTS OF ENVIRONMENTAL ANALYSIS
Results: 16.4 tCO2 avoided annually based on
Milwaukee emissions profile
14.5 tCO2 avoided annually based on National emissions profile
Equivalent to approximately 2.8 cars and light trucks not used 20.4 MPG 11,720 Miles
FUTURE PLANS
To provide a selection tool to farmers to assist in incorporating CHP into efficient aquaponics operations
QUESTIONS