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International Journal of Sustainable and Green Energy 2015; 4(1): 1-6

Published online January 20, 2015 (http://www.sciencepublishinggroup.com/j/ijrse)

doi: 10.11648/j.ijrse.20150401.11

Analysis of solar heating system for an aquaponics food production system

Kevin R. Anderson 1 , Maryam Shafahi

1 , Arthur Artounian

1 , Adam Chrisman

1Mechanical Engineering Department, Solar Thermal Alternative Renewable Energy Lab, College Engineering, California State Polytechnic

University, Pomona, CA, USA 2SUNEARTH Inc., Fontana, CA, USA

Email address: [email protected] (K. R. Anderson), [email protected] (M. Shafahi), [email protected] (A. Artounian),

[email protected] (A. Chrisman)

To cite this article: Kevin R. Anderson, Maryam Shafahi, Arthur Artounian, Adam Chrisman. Analysis of Solar Heating System for an Aquaponics Food

Production System. International Journal of Sustainable and Green Energy. Vol. 4, No. 1, 2015, pp. 1-11. doi: 10.11648/j.ijrse.20150401.11

Abstract: Aquaponics is a sustainable farming technology that combines aquaculture and hydroponics, growing fish and plants together in a symbiotic environment. Aquaponics sets an excellent example for an efficient multidisciplinary solution to

the real world problems such as drought, polluted environment and food contamination. In this paper we present an aquaponics

system heated by solar thermal energy in order to maintain the fish living environment at 21 °C. The paper presents an f-chart based analysis demonstrating the feasibility of the system. The results show for a collector area of 22 m

2 that an annual solar

fraction of 94% is needed to support an 833 liter aquaponics system.

Keywords: Solar Thermal Energy, Aquaponics, Sustainable, Renewable, f-Chart

1. Introduction

The State of California in the USA is facing its most

severe drought emergency in decades while more than 70%

of its water consumption is attributed to agriculture. This

state needs more low-demand and water-efficient agriculture

systems to overcome its long-term water crisis. Aquaponics,

an increasingly popular farming system, produces fish and

crops with 10% of the amount of water used in traditional

farming [1]. Additionally, crop production represents the

largest source of groundwater nitrate in the majority of

agricultural lands in California which has been raising public

health concerns [2]. Utilizing aquaponics requires 90% less

water and little fertilizers for the plant growth. It provides

faster growth rate, crop maturity and yields, and better

quality of the crops. Moreover, aquaponics is able to grow

crops in places where ordinary horticulture and aquaculture is

impossible due to poor or contaminated soil or water.

Another beneficial factor is minimizing the growing area [3-

5]. Aquaponics sets an excellent example for an efficient

multidisciplinary solution to the real world problems such as

drought, polluted environment and food contamination. It is a

rescue plan involving specialists from agriculture, science,

engineering, and business.

The aquaponics system described herein grows tilapia and

gold fish with a combination of different crops such as

romaine lettuce, celery, Swiss chard, ruby chard and lettuce

The optimum water temperature for producing tilapia is

between 70 to 75 °F [4]. In order to maintain the appropriate temperature for the fish, the fish tanks of the aquaponics

system must be equipped with efficient heat exchangers.

Additionally, the water quality should be monitored

continuously to ensure the level of pH, temperature,

Ammonia, Nitrite and Nitrite fulfills the aquaponics rather

limited ecosystem's demands. The long-term goal of this

research is to establish a local model which will predict the

performance of the systems in terms of plant yield and fish

growth accounting for the influence of weather, fish and

plant type, as well as water and energy consumption. The two

existing systems are outdoors utilizing gravel and rafting bed

for plant growing. This research is sustainable since we can

find a market for our truly organic crops and fish. The current

test set-up is shown in Figure 1.The ultimate goal of this

research is to build a solar thermal heating system for the

aquaponics system. This paper presents the results of a solar

thermal design analysis of such a system.

2 Kevin R. Anderson et al.: Analysis of Solar Heating System for an Aquaponics Food Production System

Figure 1. Aquaponics sustainable food production facility.

2. Materials and Methods

The present paper is a continuation of the work presented in

[7,8]. The solar thermal heating system aquaponics test set-up

at Cal Poly Pomona is shown schematically in Figure 2.

Figure 2. Solar thermal heating system schematic.

The solar thermal system to be integrated into the

aquaponics system is used to offset the energy cost of

powering auxiliary heaters during cold weather. This will

allow aquaponics system to be used in regions where the

weather fluctuates vastly over 24 hours. Figure 2 shows the

fish living environment and aquaponics grow beds. The

waste matter harvested from the fish tanks is diverted to the

grow beds in order to fertilize the crops. Figure 3 shows the

details of how the fish tanks are integrated to the grow beds

using the aerator, bio-filter and clarifier. The fish are housed

in the fish tanks, which is held at a desired temperature of 70

°F by the solar thermal energy system so that the fish can survive cold evening temperature variations.

Figure 3. Aquaponics sustainable food production facility.

The system shown in Figure 2 consists of the following

hardware:

� Solar Collectors: an array of 5 SUNEARTH Oasis-PP

solar thermal collectors with a gross area of 236 square

feet tilted at 34 degrees from the horizontal

� Thermal Storage Tank: an insulated 220 gallon storage

tank with an integrated drain-back unit into the closed-

loop system

� Heat Exchanger: a counter-flow heat exchanger between

the storage tank and the fish tanks isolate the solar

thermal heating loop from the fish supply water

� Data logger: a four-channel thermocouple data logger is

used to record the inlets and outlets of the heat

exchanger

� Pump: the solar collector loop flow rate is regulated by a

timer, which functions only during daylight hours

� Differential Thermostatic Controller: the pumps

directing the flow from the storage tank into the heat

exchanger are activated by a multiple-relay differential

thermostatic controller according to the following

algorithm; if a 10 °F delta between the thermal storage tank and fish tanks is detected or when the fish tank

temperature drops below 68 °F Figure 4 shows a typical temperature variation in the

aquaponics fish tanks versus time.

Figure 4. Temperature variations in fish tanks.

The data shown in Figure 4 was recorded over two weeks.

This data is for the aquaponics system utilizing 100%

auxiliary pool heaters to meet the load i.e. zero solar thermal

corresponds to 600 W per month (or 7.2 kW annually)

required by the pool heaters, which is taken from

measurement on the current system configuration.

Clearly, using pool heaters is not a

green/renewable/sustainable solution for large scale

aquaponics infrastructures. Thus, herein a design a solar

thermal heating system to offset the cost of auxiliary pool

heaters is presented. In the remaining sections of this paper

we discuss the proposed design and analysis of the solar

thermal based heating system for the aquaponics fish tanks.

3. Solar Thermal Analysis

The f-chart analysis method of [8] was used to perform a

feasibility on the solar thermal heating of the system shown

in Figure 2. The f-chart method is a correlation of the results

of many hundreds of thermal performance simulations of

solar heating systems. The resulting simulations give f, the

Grow Bed

T e

m p

e ra

tu re

( ˚F

)

Water Temperature Outdoor Temperature

International Journal of Sustainable and Green Energy 201

fraction of the monthly heating load (for

hot water) supplied by solar energy as a

dimensionless parameters, X (collector loss)

gain). X is related to the ratio of collector

loads, and Y is related to the ratio of absorbed

to the heating loads. The basic equations

method per [9] are summarized below, beginning

expressions for the collector loss, X and the

( )RR c ref a R

AF X F U T T

F L τ

′ = − ∆

( ) ( )( ) R

R Tn

R n

F Y F H N

F L

τα τα

τα ′

The f-chart equations for the fraction

space and water heating loads supplied by

liquid based systems (such as that one considered

given by

2 2 31.029 0.065 0.245 0.0018 0.0215f Y X Y X Y= − − + +

Figure 5 shows a f-chart for liquid systems.

Figure 5, solar thermal design engineers

chart by computing the X, Y values and then

corresponding f value.

Figure 5. The f-chart for liquid based solar heating

The fraction F of the annual heating load

energy is the sum of the monthly solar energy

divided by the annual load and is given as follows:

fL F

L = ∑ ∑

where the following nomenclature is used

through Eqn. (4)

2 2area of solar collector (m or ft )

fraction of the monthly heating load car

solar energy (%)

collector heat exchanger efficiency fact

collector heat removal factor (%)

fraction

= =

′ = =

= of the annual heating load supplied by solar energy (%)

International Journal of Sustainable and Green Energy 2015; 4(1): 1-6

space heating and

a function of two

loss) and Y (collector

collector losses to heating

absorbed solar radiation

equations of the f-chart

beginning with the

the collector gain, Y

F L (1)

c A

Y F H N F L

(2)

f of the monthly

by solar energy for

considered herein) is

2 2 31.029 0.065 0.245 0.0018 0.0215f Y X Y X Y= − − + + (3)

systems. As shown in

can utilize the f-

then determining the

heating systems [10].

load supplied by solar

energy contributions

follows:

(4)

used in Eqns. (1)

2 2area of solar collector (m or ft )

fraction of the monthly heating load carried by

collector heat exchanger efficiency factor (%)

collector heat removal factor (%)

of the annual heating load supplied by

collector loss coefficient (W/m -K or BTU

total number of seconds (SI) or hours (I

monthly average ambient temperature ( C o

empirically derived reference temper

ref

τ =

∆ =

2 2

monthly total heating load for hot water

monthly averaged daily insolation incide

surface per unit area (MJ/m or BTU/ft )

number of days in th

( ) ( )

e month

monthly average transmittance-absorptanc

normal transmittance-absorptance product n

τα

4. Solar Thermal Results

The solar thermal design simulation

[11] was used to generate the results

6 shows a layout of the system

Figure 6. Schematic layout of solar heating

production system.

As shown in Figure 6, the system

the following: collectors:

5 unglazed 48 ft2 of area each,

ft2 at a tilt angle of 34°. There are two commercial scale grow beds

plants, two filtration devices;

mineralizer /bio-filter. As shown

to interface the water in the fish

exchanger. This provides the

contaminated fish tank water

The boiler is specified at 1.8 kBTU/hr

35 %. The heat exchanger which

to the fish tanks is a shell/plate

resistance of R = 2×10-4 K/W. thermal loop has a flow rate of

of 28 psi and power consumption

in the fishtank is 16 gpm, 1.94

draw of 84 kBTU. Finally, the

is rated at 150 gal.

Figure 7 shows the solar energy

7 plots solar energy into the system

2 2 collector loss coefficient (W/m -K or BTU/hr-ft - F)

total number of seconds (SI) or hours (IP) per month

monthly average ambient temperature ( C or F)

empirically derived reference temper

�

� �

2 2

atuer (100 C or 212 F)

monthly total heating load for hot water (GJ or MMBTU)

monthly averaged daily insolation incident on collector

surface per unit area (MJ/m or BTU/ft )

� �

e month

monthly average transmittance-absorptance product (%)

normal transmittance-absorptance product (%)

Results

simulation software tool PolySun

results presented herein. Figure

as analyzed in PolySun.

heating system for the aquaponics food

system analyzed is composed of

each, total collector area = 236.25

are two fish tanks 220 gal each,

beds with a capacity of 250

clarifier/settling tanks, and a

shown in Figure 6, a boiler is used

fish tanks to the water in the heat

the required isolation of the

from the storage tank water.

kBTU/hr with an efficiency of

which interfaces the storage tank

plate style rated at a thermal

K/W. The main pump in the solar

of 19 gpm with a pressure drop

consumption of 4997 kBTU. The pump

psi pressure drop and a power

storage tank drainback system

energy input to the system. Figure

system (kBTUs) vs. month of the

4 Kevin R. Anderson et al.: Analysis of Solar Heating System for an Aquaponics Food Production System

year.

Figure 7. Solar energy input to the system (values in kBTUs).

Figure 8. Energy consumed by the system (values in kBTUs).

Figure 8 plots the energy consumed by the system (kBTUs)

vs. month of the year. Table 1 shows the f-chart calculations

for this solar heating system for an aquaponics food

production application of thermal energy harnessing and

storage.

Table 1. f-chart Analysis summary.

Month Avg. HT (MJ/m 2) Avg. Ta (°°°°C) L (GJ) PL Ps Solar fraction f fL (GJ)

Jan 10.1 13 1.72 28.9 2.3 0.95 1.63

Feb 13.1 13 1.89 23.9 2.4 0.84 1.59

Mar 17.3 16 2.28 21.3 2.9 0.88 2.01

Apr 21.8 17 2.55 18.1 3.2 0.90 2.30

May 23.1 19 2.35 19.7 3.8 0.97 2.28

Jun 23.7 22 2.10 20.7 4.2 1.00 2.10

Jul 25.7 24 1.80 24.2 5.5 1.00 1.80

Aug 23.5 25 1.60 26.8 5.7 1.00 1.60

Sep 19.0 25 1.65 25.4 4.3 1.00 1.65

Oct 15.0 20 1.75 26.4 3.3 1.00 1.75

Nov 11.4 16 1.80 26.1 2.4 0.88 1.58

Dec 9.3 12 1.78 28.4 2.0 0.86 1.53

Total 23.27 21.82

From Table 1 it is found that the fraction F of the annual

heating load supplied by solar energy is

F=∑fL/∑L=21.82/23.27=94%

Figure 9 shows the fraction of solar energy to the system f

per month

Figure 9. Solar energy fraction carried by the system, f ( %).

The heat exchanger penalty factor analysis was carried out

using the following expression per [10]

min

1 )(

)(

)( 1

−

 





 



 −  





 





 





 



 +=

′ =

εp cp

R HX

F F

(5)

where

=HXF heat exchanger penalty factor

cpcm )( ɺ = thermal capacitance of the collector

min)( pcmɺ =minimum thermal capacitance

ε= heat exchanger effectiveness. Application of Eqn. (5) to the current system using a

Stainless-steel plate/shell heat exchanger rated at 790

provided the data of Table 2.

500

1000

1500

2000

2500

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Solar Energy Input (kBTUs)

100

200

300

400

500

600

700

800

900

1000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Energy Consumed (kBTUs)

100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Solar Energy Fraction(%)

International Journal of Sustainable and Green Energy 201

εεεε Penalty Fhx

0.21 0.963

0.30 0.974

0.40 0.980

0.50 0.984

0.60 0.987

0.70 0.989

0.80 0.990

0.90 0.991

0.99 0.992

1.00 0.992

where NTU = number of transfer units for the

AHX = heat exchanger area (m 2), and Qu =

collected (GJ/yr). The results of ε-NTU of Table be in agreement with standard references in

design [12]. The average temperature of

shown in Figure 10.

Figure 10. Aquaponics fish tank temperature

Figure 10 illustrates that the solar thermal

designed herein will hold the fish tanks

system at an average of 70 °F as desired.

5. Conclusions

This paper has presented the analysis of

heating system proposed for an aquaponics

production system. The f-chart analysis method

suggests that 94% of annual energy is carried

thermal collectors / heat exchanger / storage

This option of using solar thermal is a viable

solution as opposed to the current baseline

pool heaters to heat the aquaponics fish tanks,

on average 7.2 kW annual to maintain the

proper temperature. This paper has also

exchanger design simulation showing that an

75% provides NTU=2. This value is in

standard results for heat exchanger design

Future work involves the procurement and

solar thermal heating system analyzed herein.

on-site data for thermal performance can

disseminated.

International Journal of Sustainable and Green Energy 2015; 4(1): 1-6

Table 2. Heat exchanger penalty factor analysis.

NTU AHX (m 2) Energy

0.25 0.12 0.10

0.40 0.19 0.15

0.58 0.28 0.23

0.82 0.40 0.32

1.13 0.55 0.44

1.55 0.76 0.61

2.22 1.08 0.87

3.42 1.67 1.35

7.83 3.83 3.09

-- -- --

the heat exchanger,

= the useful energy

Table 2 are seen to

in Heat Exchanger

of the fish tanks is

temperature transient.

thermal system as

in the aquaponics

of a solar thermal

aquaponics sustainable food

method based on [9]

carried by the solar

storage tank system.

viable green energy

line design on using

tanks, which requires

the fish tanks at the

presented a heat

an effectiveness of

in agreement with

design a found in [12].

and installation of the

herein. From whence

can be gathered and

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