Abstract
The goal of this analysis was to evaluate energy and cost requirements for different configurations of a rainwater harvesting (RWH) system in conjunction with a solar PV and energy storage system for an off-grid house. Using models in fluid mechanics, we evaluated energy and power requirements for four different system configurations: 1. An On-Demand System containing a single speed pump (OD-SS), 2. An On-Demand System containing a variable speed pump (OD-VS), 3. A Pressurized Storage System where water is pumped once during the day into a large pressurized tank for later consumption and treated on demand via UV light (PS-AOT), and 4. A Pressurized Storage System where water is treated once per day via UV light and then stored for later consumption (PS-TO). Our analysis showed that the OD-SS system model requires 2.63 kWh per day, the OD-VS system model requires a total energy of 1.65 kWh per day, and the PS-AOT requires 1.67–1.69 kWh per day depending on the pump size, and the PS-TO system requires 0.19–0.36 kWh per day depending on the pump size. When comparing estimated cost between systems, we found the OD-SS system to be the most expensive. With the OD-SS system as a base for system costs, we found the OD-VS system to be 39% less expensive, the PS-AOT system to be 21% less expensive, and the PS-TO system to be 60% less expensive than the base OD-SS system.
Highlights
Increasing water scarcity around the U.S and the world has sparked interest in alternative water supplies and auxiliary water systems, including rainwater harvesting (RWH) for both potable and non-potable use [1]
We considered four system designs: (1) an On-Demand System based on empirical data using a single speed pump (OD-SS), (2) an On-Demand System using a variable speed pump (OD-VS), (3) a Pressurized Storage System where water is treated on demand and the UV light is
For the per day then below.for later consumption (PS-TO) system, we found that the total energy requirements varied by assigned treatment time and pump size (0.19–0.36 kWh for treatment times between 0.75 and 4 h)
Summary
Increasing water scarcity around the U.S and the world has sparked interest in alternative water supplies and auxiliary water systems, including rainwater harvesting (RWH) for both potable and non-potable use [1]. Improvements in design standards of first flush diverters, ceramic filters, and pressurized storage tanks have enabled the use of RWH systems as supplemental sources for irrigation and even drinking water. Emerging technologies such as UV light treatment has made harvested rainwater a viable source for potable residential water supply [2]. For homeowners with off-grid houses, providing reliable potable water requires a reliable electricity supply to run the pump(s) and treatment system.
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