Design of a prototype building panel for rainwater storage and energy generation

Abstract

The functionality of buildings, such as walls carrying loads and transferring such loads to the foundation, needs to be modernized by adding value, where walls can, through load-bearing or non-load-bearing walls, harvest and store rainwater and generate energy as an alternative to conventional electricity. The need for alternative water supply for secondary use and alternative energy is gradually gaining momentum in South Africa (SA). SA encounters a challenge in addressing the demand for essential energy and water services in rural communities. The imperative for decentralised, sustainable, cost-effective clean energy and water solutions is important in rural areas. This research aims to design a prototype building panel for rainwater storage and renewable energy generation. The objective is to determine the rainwater volume in cubic meters (m3) to be harvested on a 10-Watt peak (Wp) panel, which forms a building panel with dimensions of 345mm × 60mm × 200mm referred to as mBP and a rainwater harvesting (RWH) tank with dimensions of 314mm × 50mm × 195 referred to as iBP, embedded in the building panel, the power output of a 10Wp polycrystalline flexible solar cell (FSC) on a vertical surface, and technology-related costs. Existing experimental rainfall data was used to analyse rainfall intensities. Theoretical research strategies are applied, consisting of mathematical calculations for the design of; a non-load-bearing (NLB) building panel, bolt, rainwater storage (RWS) and photovoltaic (PV) systems, using Computer-Aided Drawings and modelling a building panel incorporating RWS and PV and simulating rainwater. Modelling of the RWS tank included using polylactic acid (PLA) as a construction material, moulded into an mBP and iBP for a RWH tank. PLA is a filament used in 3D printing, a low-density polyethylene (LDPE) chosen as construction material derived from corn-starch or sugarcane. All electrical components were connected. The building panel was assembled using a Sika 219i marine adhesive sealant to join the FSC to one side of the building panel (345mm × 200mm), and placed on pegboards (800mm × 200mm × 2) which acted as a vertical wall. All testing components were placed on this vertical panel, including the prototype, the MPPT, the battery, and a 5mm perforated recycled polyethylene terephthalate (rPET) 2ℓ bottle. The tests were conducted on both the RWH and the PV systems. For the RWH system, the collected data was the depth of the rain every 15-minute intervals. For PV, the collected data was Wattage(W), Voltage(V) and Amperes(A). While PVsyst was used as a simulation tool for grid-tied and standalone systems. Mathematical computations were employed to assess the structural integrity of the proto-type building panel and bolt design, evaluating their capacity to withstand the Rainwater (RW) harvesting system when the associated tank reaches 100% capacity. Results indicated that the building panel, coupled with the bolt design, demonstrated resilience against the weight imposed by the RW harvesting system at full capacity. The accumulated rainwater ranged from 37mm to 126mm, while the generated energy varied between 7W and 15W. Furthermore, the prototype underwent evaluation under 0% and 100% full capacity scenarios, yielding cumulative energy outputs of 7W and 15W, respectively. In a simulated standalone system, the performance ratio (PR) exhibited a modest rate of 0.56, while the solar fraction (SF) demonstrated a high rate of 0.956. Conversely, the grid-tied system achieved a PR of 80.2% under normal Standard Test Conditions (STC) efficiency. The prototype's total cost, including value-added tax (VAT), amounted to R11203. Estimated financial figures included revenue of R77935, expenses totalling R38700, and a resultant profit of R50438.