Designing an Aquaponic Greenhouse for an Urban Food

2.3.2.8 Lighting of Plant Beds
Plants need a very good lightening system to grow appropriately .The type of lighting we have to choose
is dependent on the location of the aquaponics, the average amount of sun hitting the green house and
type of material used to cover the greenhouse .For example the material used to cover the green house
will limit the natural light that will enter inside. Consequently we will need to have a lamp that powerful
that will compensate this limitation. We have to take some factors in consideration like the power of the
lamp, lifespan, and cost per 100 lumen. The lamp power is the power dissipated by the lamp when
connected to the electrical circuit. The life span is the average lifetime of the lamp and the lumen output
is the amount of brightness emitted by the lamp. The cost per lumen is the amount in dollars per 1
lumen brightness. Lumen is the unit of light intensity flux.

The main types of artificial lights used are shown in the table below:

Lamp

Power

Lifespan Lumen(L)

Output

Cost per 100
lumen
Incandescent 100w 1,200 h 1435 $3.99
Fluorescent 100w 8,000 h 5945 $0.96
LED 100w 50,000 h 3780 $0.95
HPS 100 w 22000 h 6935 $0.83

• Per year power costs are based on 4000 hours operation (approximately all night every night) and $0.10/kWh energy cost.
  Sources:
  E Lamp Products Catalog 2001- 2002
  Osram/Sylvania Lamp & Ballast Catalog, 1998; 2004; 2010
  Philips Lighting Company Lamp Specification and Application Guide, 2001/2002
  J. Lienhard IV and J. Lienhard V, A Heat Transfer Textbook, Philogiston Press, Cambridge, MA, Web Edition 2008,
  http://web.mit.edu/lienhard/www/ahtt.html.
  http://www.gardenandgreenhouse.net/index.php/past-issues-mainmenu-18/36- 2009 - gg/january-february-2009/359-artificial-light-for-the-
  greenhouse

Table 11. Types of Lights

Based on the

Table 11 we can see clearly that the LED light are the best choice for our system in short and long term.
The lifespan is very high compared with the others. The LED technology is evolving and is noted as the
future of lighting. It has very good lumen out and also comes in different colors and wavelength.

2.3.3 Composition of Fish and Crops in Aquaponics

Plants that generally do well in aquaponic systems are leafy crops such a lettuce and herbs. There is a
direct correlation between the amount of fish present and the yield and quality of the plants being
produced. Plants that fruit, as well as legumes require more nitrogen content for a per square unit yield
than plants that do not fruit. The tomatoes is a widely studied fruit, it requires 51.6 kilograms per
hectare of Nitrogen to flourish and develop properly. (Timothy, 2009) Non-fruiting plants such as lettuce
require only less than 35 kg per hectare of nitrogen (Metabolization rates of Biological Filters). Fruiting
plants therefore require approximately fifty percent more nitrogen than their counterparts and this
poses a problem in aquaponic systems.

The correlation between nitrogen productions in the form of waste from the fish is not a linear one,
doubling the amount of fish will not double the nitrogen content. Most fish will excrete up to one third
of their body weight in waste per day, with average levels of 3.97% dry weight of Nitrogen but this