55 Gallon Metal (Not
cleaned)$10^2 32 $320 Would need to be cut
open for access. Need
to be cleaned.
1:http://www.graystonecreations.com
2:http://craigslist.org
Table 21. Estimated Cost of Water Tank Options
4.3.3.1 Water Tank Result/Recommendation
The 275 Liter plastic totes were chosen because they can be sourced cheaply and easily (see table), are
modular, and reliable. Wooden tanks are attractive because of the price, but plastic totes are in a similar
price range and are far easier to source. Large plastic tanks, while more robust, are much more
expensive (especially in smaller sizes), and cannot easily be sourced. 55 Gallon drums are another cheap
solution, however we would need a very large number of individual tanks for our system, which would
create rather complex piping setups. As well, they do not have flat bottoms (if turned on side) and
would need special mounting. Metal drums have the additional issue of needing to cut them, creating
potentially dangerous edges.
The more individual tanks there are, the more individual pumps would need to be purchased. The totes
provide a balance between number of systems and price. Having 10 individual systems also provides
resistance to disease, while not being unmanageable.
4.3.4 Water Heating
Since our target temperature for the greenhouse will be 60 F, the temperature in the water tank will be
the same as the greenhouse consequently. In this condition we will have a water temperature at 60 F all
the time. Many fish species can survive in this conditions and that includes tilapia .Since we want the
maximum yield from the fish we need to create optimum environmental factors. In order for tilapia to
thrive the optimal temperature is 75 F, and to achieve this we will need to install additional heaters to
warm the water.
We have concluded that we will use around 1500 gallons of water to properly provide enough nutrients
for the area of seedlings we are going to grow. From the calculations (Appendix C) we will need a water
heater with the power rating of 1.8 Kwh to compensate for the heat loss during the circulation of water
and from the surface of tank .The monthly cost except the summer months when the temperature
during the day goes around 75 F is calculated as below:
1.8 kWh x 24 hours x 30 month x 0.17 $/kWh = $220/monthly
We also have to note that the amount of energy lost from the water will heat the greenhouse itself so it
will help the structure heaters lowering their consumption.
The recommended heater for the tank is the one shown in the Figure 41 and will cost $296.We will need
two of them to fulfill our power requirement.