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