A Long-Term Analysis of the Possibility of Water Recovery for Hydroponic Lettuce Irrigation in an Indoor Vertical Farm. Part 2: Rainwater Harvesting

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.

The impact of the regularization on the economic analysis of rooftop rainwater harvesting system

“…Various discount rates of 5, 7, and 10% considering inflation rates of 3, 4, and 5% was used for economic analysis of rainwater harvesting systems in Melbourne, Australia (Khastagir & Jayasuriya 2011). A DR of 5% and the inflation rate of 4.5% are considered by Jurga et al (2020) for the economic analysis of rainwater harvesting in Poland. In Jordan, a 5% DR without considering the inflation rate is used for rainwater harvesting economic analysis (Abdulla 2020).…”

Economic attractiveness of domestic rainwater harvesting in Brazilian cities

“…A study in Nigeria [ 17 ] focused on optimizing storage in different types of dwellings in the city of Enugu. A study from Poland explores the possibility of using RWH for the hydroponic production of lettuces [ 18 ] and reports payback periods of about 8 years. However, also in Poland, a recent study concludes that the economic sustainability of RWH systems for domestic use is questionable [ 19 ].…”

Observation Experiment of Wind-Driven Rain Harvesting from a Building Wall

“…In the case of tall buildings, the amount of rainwater to be harvested from the wall could be more than that from the roof. To date, a building wall has only been considered for urban greening [41][42][43][44][45][46]. Samzadeh et al [47] estimated the level of rainwater harvested from the building wall by applying an empirical equation, but a direct observation of the rainwater from the wall has not been conducted yet.…”