Feasibility of Vertical Rainwater Harvesting via In-situ Measurement of Wind-driven Rain Loads on Building Facades in a Tropical Climate

Abstract

Rainwater is an alternative water resource to fulfill sustainable management of freshwater particularly in the regions receive abundant annual amounts of precipitation such as tropical Malaysia. To collect and store rainwater, rainwater harvesting system has been practiced since ancient from horizontal surfaces mostly rooftop of buildings in urban areas. Nowadays, this method in modern urban areas with tall buildings is considered inadequate and uneconomical because the ratio of facade surface areas is much higher than the ratio of roof surface areas. On the other hand, all rain has a horizontal velocity due to wind acting upon rain droplets which is called wind-driven rain (WDR). Growing tall buildings and the presence of WDR phenomenon make building façade surfaces the available promising surfaces to harvest substantial rainwater vertically and more efficiently. This article presents a one-year field measurement results that aims at quantifying the WDR loads impinged on the vertical facade areas of a pilot building located at the main campus of the University Malaya in Kuala Lumpur, Malaysia. Detailed descriptions of the gauge design, building, the measurements of on-site WDR, rainfall duration time, and weather data are presented. Records show that monsoon winds characteristics have significant influence on the WDR loads on the building facades compare to horizontal rainfall intensity. Finally, the collected in-situ data are exploited to validate data and determine WDR coefficient (γ) to estimate the amount of WDR on a building façade via an empirical WDR relationship. Results show the feasibility of each square meter of vertical façade area to supply 12% of non-potable or 4.9% of potable water-usage per capita per day.

Potentials of hydroactive lightweight façades for urban climate resilience

“…Vertical RWH of wind-driven rain (WDR) that strikes the façade of the growing number of high-rise buildings due to the horizontal wind velocity component can be seen as a more effective and economic approach than the traditional horizontal RWH. 17 The multi-dimensional advantages of decentralized rainwater management integrated into the façade consist not only of relieving the load on urban sewage infrastructure but also of reducing global water and energy consumption. 18 The use of absorbed rainwater in a F I G U R E 5 Increase in wind velocity with rising building height for different initial wind velocities at a reference height of 18 m above ground (A) and trajectory angle in relation to wind velocity as a function of droplet diameter, steady-state condition (B) building can lead to a reduction of the total building-internal water consumption by up to 45%.…”

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

“…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. In this study, three WDR-harvesting gauges of different heights were prepared to directly observe the rainwater from a building wall.…”