Cold Climate Tomato Production Facility

Suha H. Abdullah, Omar M. El-Sherif, Abdul I. Murayyan, and Justin D. Toupin

Abstract -- In this paper, we present a method of producing passive solar heating is provided by a single wind turbine. The tomatoes for profit in an isolated Arctic community using only system is semi-autonomous but will require trained staff for renewable energy sources. A modified rockwool drip hydroponics harvesting, equipment maintenance, and limited amounts off- system was employed, which uses electrodialysis to reclaim efflu- site monitoring. ent nutrient solution. The facility proposed is a modified A-frame greenhouse with highly insulated exterior walls and a slanted roof III. DETAILED DESIGN made of transparent polycarbonate. The facility operates on pas- A. Structure & Insulation sive solar radiation that is supplemented by wind power from a 10 kW turbine. A heat exchanging ventilation system is imple- The design has a floor area of 12.5 m x 5 m. The building is mented to reduce the amount of heat lost in the winter. A control a modified A-frame design with the side profile given below. system is included to partially automate operation and to allow The building is orientated design at a 60 angle north of west to for remote system control and monitoring through the Internet. optimize incident light and minimize snow drifting at the Index Terms -- Arctic, Greenhouse, Hydroponics, Wind Tur- northern entrance. The structure is raised on steel piles to limit bine. damage to underlying permafrost. The roof of the structure is I. INTRODUCTION made of translucent, triple-pane polycarbonate to allow light transmittance while acting as a good thermal barrier. The walls ARVIAT, Nunavut is an isolated hamlet on the coast of Hud- and floor are insulated using 15 cm of polyurethane foam and a son Bay. It is difficult for the 2000 inhabitants to find reason- 10 cm air gap. The internal walls of the structure are covered ably priced produce due to limited accessibility and harsh in a layer of a reflective barrier made of aluminum composite weather conditions that do not favor traditional agricultural to stop heat absorption. It rests on top of a layer of vapor bar- practices. Off grid renewable power and water recycling are rier which prevent moisture damage to the structure. required due to the low power grid capacity and limited fresh water supply in Arviat. The operation must be completely self- contained and compatible with the northern climate. Currently 1m non-profit greenhouses operate during the summer in similar Polycarbonate Glass northern communities [1]. However, our facility will produce crops for profit. Commercial, fully automated and self-con- tained greenhouses have been implemented successfully but in very different climatic regions [2]. The design proposed is 4m unique because it aims to operate all year round in the Arctic in a manner that is both environmentally and economically 40° sound. Thermodynamic testing, energy analysis, and cost anal- ysis were performed to illustrate the feasibility of the design 0.44m solution. The main focal point of the greenhouse design is the optimization of energy efficiency. The milestone for this project is a three-dimensional model of the facility simulated in 5m AutoDesk Architectural and Viz 2007©. Figure 1: Side profile of facility.

II. CONCEPTUAL DESIGN METHODOLOGY B. Hydroponics & Water Recycling A. Overall design A three-stage rockwool hydroponics system is best for The facility is triangularly shaped and oriented to maximize growing vine plants such as tomatoes [4]. On average, rock- solar radiation through the slanted transparent roof. The facility wool hydroponics facilities produce 30 times the amount of houses 80 heirloom tomato plants through all three stages of tomatoes as compared to conventional soil greenhouses [4]. their life cycle. This variant of tomato was chosen because of Stage 1 of the production is designed to meet the needs of the its frost tolerance, high nutritional value, and exceptional fla- tomato plants in the early stages of their growth. When the first vor [3]. The plants are grown in a rockwool hydroponics sys- leaves emerge, the plants are transplanted to stage two. The tem that reclaims water using an electrodialysis filter. The approximate duration of stage one is 7 days. When the tomato facility is ventilated using a heat exchanger to minimize winter plants outgrow the cubes in stage two, the plants are trans- heat loss. Power requirements beyond what are supplied by ported to the rockwool slabs of stage 3. The length of the slabs allows us to grow roughly 4 - 5 tomato plants per slab. When

University of Guelph, Proceedings of the ENGG 3100: Design III projects, 2007 3 natural lighting becomes insufficient, additional light is pro- vided using three 1 kW high pressure sodium lights placed 3.75 m above the facility's floor. 70

In order to reduce water usage, the nutrients that are not 60 absorbed by the plant will be removed from the water stream so that the ion free water can be recycled. The nutrients are 50 removed based on charge using 42 pairs of electrodialysis cells with an estimated power consumption of 5 W. The water 40 stream entering the electrodialysis unit is continuously titrated 30 down to a pH of 3 to prevent calcification. Payback Period(years) A two tank gravity fed system is used to ensure even disper- 20 sion of nutrient to the main pipeline. The mainline diverges into separate lines that feed each tomato plant. The nutrient 10 solution passes through the plant roots, the rockwool cubes/ 0 slabs, and into a return line that takes the solution back to the 0 5 10 15 20 25 Yield (kg/plant/year) control system for filtering and re-dilution. Figure 2: Payback period as a function of plant yield. C. Ventilation The heat exchanger used is a counter-current shell in a tube This design proves that a facility like this is feasible; how- design that provides 0.75 air exchanges per hour. The hot ever it is still too costly due to its high power requirements. inside air is expelled through a 0.9 m diameter outer shell. Nine Heat loss through ventilation was the biggest factor in deter- pipes of 0.1 m diameter run inside the outer shell and bring mining heating requirements. It is suggested that future designs outside air into the facility. The total surface contact area use a heat exchanger that is more efficient like the one pro- between the cold and hot air streams is 9 m2. The heat posed by D. Rousse et al. [7]. Lighting also proved to be a large exchanger's efficiency is estimated at 40 percent when outside power cost; we propose that tests be performed to determine temperatures are below zero. During the summer months the how much light is actually needed for satisfactory plant two fans that drive air exchange can both be set to drive air out growth. The proposed idea of using remote monitoring of the of the facility to help remove excess heat and humidity. facility by centralized technicians is beneficial because it will D. Control System allow operators to globally service multiple operations simulta- neously. Some on site staff is still required because fully auto- The system contains water sensors and controls for: electri- mated systems will still require daily monitoring of the ion cal conductivity, pH, flow rate and temperature. The system concentration in the nutrients. To improve on economic feasi- also contains air sensors and controls for: humidity, CO2 lev- bility, future designs should attempt to service more than one els, light levels and temperature. All control devices can be community whenever possible. In addition, we propose to sell adjusted and logged through a central computer and sensory any excess power to the local power grid. output. Using a satellite Internet connection the system can be adjusted and monitored by centralized off-site technicians. ACKNOWLEDGMENT E. Wind Power We acknowledge support from our GTA project advisor Amanda Farquharson, our faculty advisor Professor Lubitz, The facility is off-grid and wind powered. Wind power was and Professor Runciman. chosen due to the high mean wind speeds of 7 m/s in Arviat and the lack of viable alternatives. Power requirements are met REFERENCES by a southeast facing 10 kW Bergey Excel turbine that is [1] Mahoney, Jill (2004), "Hothouse flourishes as rink turns over new leaf", mounted on a 24 m lattice style tip-up tower [5][6]. The turbine The Globe and Mail, p. A7, July. 12. can exceed the facility's total power requirements by 25 per- [2] Organitech Inc. Homepage. Retrieved February 28, 2007, from http:// www.organitech.com . cent. The excess power is used to charge a string of batteries of [3] A. Rodriguez-Burruezo, J. Prohens, S. Rosello, and F. Nuez, "Heirloom 36 kWh total capacity with a nominal voltage output of 120 V. varieties as sources of variation for the improvement of fruit quality in greenhouse-grown tomatoes," Journal of Horticultural Science and Bio- IV. DISCUSSION technology, vol. 80, no. 4, pp. 453-460, July. 2005. The cost of this facility has been estimated upon structural [4] H. M. Resh, "Hydroponic food production : A definitive guidebook of soil- materials and mechanical equipment. The total cost is $60 000, less food-growing methods : For the professional and commercial grower and the advanced home hydroponics gardener," 6th ed. Mahwah, NJ: which is a reasonable price for a facility of this size. We have Newconcept Press, 2004, pp. 313-315. estimated the payback period of the facility as a function of [5] Natural Resources Canada (2007). The Atlas of Canada. Retrieved March plant yield and selling price of the tomatoes. To establish the 15, 2007, from http://atlas.nrcan.gc.ca/site/english/index.html facility as a serious competitor in the market, tomatoes will be [6] Bergey Excel Wind Turbine Specifications. Retrieved March 3, 2007, from sold at $5.00 per kg. This is approximately 25% cheaper than http://www.bergey.com/Products/Excel.html [7] D. Rousse, D. Martin, R. Thériault, F Léveillée, and R. Boily (2000). Heat the current tomato prices in Arviat, Nunavut. At this price, the recovery in greenhouses: A practical solution. Applied Thermal Engineer- payback period is projected based on the yield of the tomato ing, vol. 20, no. 8, pp. 687-706. plants as illustrated in Fig 2.

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