Abstract
The aim of this study was to determine the suitability of a rainwater harvesting system to cover the water demand for indoor hydroponic lettuce cultivation located in Wrocław (Poland). The analysis was performed on the basis of the recorded rainfall in Wrocław in 2000–2019. The analyzed cultivation is located in a hall with an area of 300 m2, where the lettuce is grown vertically by the hydroponic method. The calculations of the rainwater harvesting (RWH) system were carried out considering the selection of the tank capacity for the collected water. The operation of the water storage is simulated using a yield after spillage (YAS) algorithm. It was evident that the proposed system might be an auxiliary system that relieves the water supply network or supports other water recovery systems (e.g., the water vapor condensation in a cross-flow heat exchanger operating as an element of the air conditioning system, proposed in Part 1 of this study). The harvesting system for the selected vertical farming indoor hall covers an average of 35.9% of water needs and allows a saving of 146,510 L of water annually for the cultivation. An average water demand coverage increases up to 90.4%, which allows a saving of 340,300 L per year when the RWH system is combined with water recovery from exhaust air from the hall.
Highlights
In recent years, indoor vertical farming has become increasingly popular, as a means of sustainable development in the agricultural sector
The aim of this study is to determine if the rainwater harvesting system itself, and in combination with water recovery from the exhaust air by a cross-flow exchanger operating in the air-conditioning system is sufficient to cover the water demand for hydroponic lettuce cultivation located in Wrocław (Poland)
All simulations were repeated for four additional volumes (6, 9, 15, 18 m3) in the years 2000–2019, and 2012–2019 for the rainwater harvesting (RWH) system, and the RWH system assisted by water recovery from the exhaust air system, respectively
Summary
Indoor vertical farming has become increasingly popular, as a means of sustainable development in the agricultural sector. Many important factors need to be taken into account in order to create a truly sustainable place of food production. The lack of soil use reduces the risk of transmission of pathogens. It enables greater control over cultivation parameters and the composition of the fertilizer used. Other considerations include water supply system, ventilation, HVAC (Heating, Ventilation, Air Conditioning), indoor air circulation, nutrient sanitation, and lighting. In each of these fields, some novel design and technological approaches can be taken. Various aspects of vertical farming were extensively reviewed in Kalantari et al [3]
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