Greener Greenhouse Design by Université De Sherbrooke

Team Blog: Greener Greenhouse Design
April 9, 2021 – CCDP 2100X Team 1 – Maisha, Mais, Nishi, Tao

The Greener Greenhouse reported here is based on a greenhouse design by a team of engineering students from the Université De Sherbrooke (https://www.cbc.ca/news/canada/montreal/universit%C3%A9-de-sherbrooke-students-create-greener-greenhouse-1.5851731), that is fully self-sufficient and off-grid, that also provides food security. One of the main goals of this design is to develop sustainable cities and communities by focusing on the four topics shown in Figure 1.

Figure 1: A greenhouse with the emphasis of the four key areas of research indicated [Team 1]

The Greener Greenhouse is a self-sufficient and off grid greenhouse that promotes food sovereignty among communities [1]. The greenhouse enables locally produced food, which is more sustainable and gives people the chance to see how and where the food they eat is grown. The transportation of food across thousands of kilometers which is a large contributor to gas emissions, will no longer be necessary as the vegetables and fruits are going to be grown in the greenhouse. It also allows individuals to be self-sufficient and not have to rely on external energy and power sources for running buildings. It will allow for the reduction of energy bills and the provision of a  year-long nutritious food supply. Overall, it will contribute to producing sustainable cities and communities.

[1] Open Access Government. “How you can create a self-sufficient home”. Openaccessgovernment.com.https://www.openaccessgovernment.org/self-sufficient-home/59276/  (accessed February 2, 2021).

Image Source: Video Presentation

Heat Distribution: Maisha Abdullah

Heat distribution is an important aspect of a greenhouse, as it maintains ideal temperature for plants to grow in. To understand the heat distribution in the greenhouse, scientific theories concerning heat transfer should be examined. A method of heat transfer is convection. Convection is a theory that describes the molecular changes in the air when met with a source of heat [1]. In the greenhouse, the source of heat is the sun. As demonstrated in Figure 2 below, When the air molecules in the greenhouse meet the heat, they will expand and rise, forcing colder and denser molecules to sink. This reaction will cause a circular motion called the convection current that will transfer heat in the room. The Second Law of Thermodynamics states that processes can either be reversible or irreversible [2]. Considering that heat transfers from warmer places to cooler places [2], some heat will transfer out of the greenhouse when the sun sets. Therefore, insulation is needed to keep the heat inside.

Figure 2: Convection in the greenhouse [Maisha A.]

[1]   Machine Design. “What’s the Difference Between Conduction, Convection, and Radiation?”. Machine Design. https://www.machinedesign.com/learning-resources/whats-the-difference-between/document/21834474/whats-the-difference-between-conduction-convection-and-radiation (Accessed January 24, 2021).

[2]   Learn Engineering. “Understanding Second Law of Thermodynamics !”, Youtube, June 29, 2018. [Video file]. Available: https://www.youtube.com/watch?v=WTtxlaeC9PY&ab_channel=LearnEngineering.

Image Source: Captured from group presentation video

Insulated Walls: Mais Karaki

The greenhouse’s insulated walls, as shown in Figure 3 below, will contribute to reducing heat costs, increasing energy efficiency and providing the plants a controlled environment to grow in [1]. Fourier’s Law of Heat Conduction can explain how insulation will keep the heat inside the greenhouse. Fourier’s Law states that the time it takes for heat to transfer through a material is directly proportional to the change in temperature from one side of the material to the other, the total area, and the thermal conductivity of the material [2]. As illustrated in Figure 3, during seasonal temperature changes, the insulation will protect the greenhouse and prevent heat loss. In the winter, when the heater is on inside the greenhouse, the insulation will prevent the heat from escaping and the cool air to enter.  The insulation’s addition to the layers of the wall will increase the area and thermal conductivity of the material. As a result, it will be harder for heat to transfer into and out of the greenhouse.

Figure 3: Insulation’s effect on the greenhouse in the winter [Mais Karaki]

[1]  Government of Canada. “Keeping the Heat In - Chapter 2: How your house

works”. Government of Canada. https://www.nrcan.gc.ca/energy-efficiency/energy-efficiency-homes/how-can-i-make-my-home-more-ener/keeping-heat/keeping-heat-chapter-2-how-your-house-works/15630  (accessed January 25, 2021).

[2]    N. Connor. “What is Fourier’s Law of Thermal Conduction - Definition”.

Thermal Engineering. https://www.thermal-engineering.org/what-is-fouriers-law-of-thermal-conduction-definition/  (accessed January 25, 2021).

Automated Lighting: Tao Lufula

 Light is a requirement for plants to grow [1], and the lighting system makes it possible to provide plants with the required amounts of light and helps save the energy stored in the battery. A computer system that keeps track of the amount of sunlight and controls the artificial lights is integrated into the greenhouse as shown in Figure 4 below. The system helps optimize the electricity use within the greenhouse, which is crucial as the greenhouse is off grid. A light sensor detects the natural light intensity inside the greenhouse and generates a signal to determine if the artificial lights should be on or off. Combinational logic helps the computer in the greenhouse decide whether the lights should be on or off. Combinational logic combines logic gates to process input signals and generates an output signal; it is a type of digital logic implemented by logic circuits [2]. Logic circuits are circuits that execute processing functions in a computer. To process the greenhouse data, these circuits implement logical operations [3].

Figure 4: Automated lights inside a greenhouse [Mais Karaki, Maisha Abdullah, Tao Lufula]

[1] C. D. Rogers, "Why Is Photosynthesis Important to Humans?," Sciencing, 18-Nov-2019. [Online]. https://sciencing.com/why-is-photosynthesis-important-to-humans-12000249.html [Accessed:05-Feb-2021].

[2] Bishop G.D. (1977) Logic Elements and Circuits. In: Electronics II. Macmillan Technician Series. Palgrave, London. https://doi.org/10.1007/978-1-349-03178-8_6. [Accessed: 15-Feb-2021].

[3] “Logic Circuits: Definition, What & Types: Computer Science,” Teach Computer Science, 09-Feb-2021. [Online]. Available: https://teachcomputerscience.com/logic-circuits/. [Accessed: 08-Apr-2021].

Battery System: Nishi Prajapati

As shown in Figure 5 below, the battery system, which consists of a solar panel, solar charge controller, battery and load, works to provide heat and electricity to the greenhouse. Within the battery, an electrochemical reaction occurs between two different chemical compounds which allows it to generate power [1]. This electrochemical reaction - otherwise known as a redox reaction - includes the exchange of electrons between one chemical species to the other, in order to discharge energy [1]. The solar charge controller regulates the flow of current and voltage between the three other elements in the system [2]. Therefore, it is able to monitor when the battery is running low or not. When the battery needs to be recharged, the controller allows power from the solar panel to pass through it. This forces the redox reaction in the opposite direction, which regenerates the chemical compounds and recharges the battery.

Figure 5: The elements of a battery system in a greenhouse and how they are wired together [2]

[1] Libretexts, “Oxidation-Reduction Reactions,” Chemistry LibreTexts, 15-Aug-2020. https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry)/Electrochemistry/Redox_Chemistry/Oxidation-Reduction_Reactions#:~:text=Redox%20reactions%20are%20comprised%20of,and%20th e%20oxidation%20number%20increases. [Accessed: 28-March-2021]

[2] “Solar Panel Charge Controller Wiring Diagram - Best Guide,” ZHCSolar, 19-Jul-2020. [Online]. https://zhcsolar.com/solar-panel-charge-controller-wiring-diagram/. [Accessed: 28-March-2021]