Field Validation of Electrochemical Water Filtration System on an Open Loop Cooling Tower at Toyota Motor Manufacturing Plant in Blue Springs, Mississippi
Abstract
The U.S. Department of Energy Industrial Efficiency and Decarbonization Office’s Industrial Technology Validation (ITV) program aims to identify and demonstrate the performance of new, emerging, and underutilized technologies in the industrial sector to help inform decisions towards accelerating commercialization and deployment. One such ITV project is to demonstrate the performance of an electrochemical water treatment technology on a cooling tower at an automotive plant. Cooling towers are vital equipment for dissipating heat from industrial processes. However, they face challenges related to scaling, corrosion, and the growth of biological contaminants. Effective cooling tower water filtration and treatment is essential to reduce these contaminants, along with other total suspended solids (TSS) and total dissolved solids (TDS) in the system. Various treatment systems, such as sand-based filters, centrifugal separators, and disc filters, offer distinct advantages and limitations. ElectroCell Systems offers a skid-mounted, electrochemical based, side-stream filtration system. Facility and Technology Description and Scope This study evaluated the performance of an ElectroCell water treatment system at Toyota Motor Manufacturing Mississippi compared to an existing centrifugal-based filtration system from Lakos. The incumbent technology uses centrifugal principles to eliminate TSS from cooling tower water. In contrast, the ElectroCell system employs a multistage electrochemical process using low-voltage and high-voltage ionizers to generate an electrostatic field to treat the water. The scope of the evaluation included six chillers, each rated at 2,000 tons, three cooling tower cells, three air compressors (one screw at 702 horsepower and two centrifugal at 1,860 horsepower), and the relevant water treatment systems. Study Design and Objectives The evaluation’s goal was to assess the impact of the ElectroCell filtration system on energy, water, and chemical usage in the chilled water and compressed air systems with a cooling tower loop. The following are some of ElectroCell Systems’ claims and reasonings that were stated in their application and used as the basis for ITV evaluation: • Water usage reduction. The electrochemical-based system removes particulate down to 1 micron, which is an improvement from most filtration systems. In theory, less particulate in the loop should reduce the need for blowdown and in turn makeup water. • Energy reduction. The system minimizes scaling, resulting in less fouling and improved heat transfer within the system, leading to reduced energy U.S. Department of Energy | Office of Energy Efficiency & Renewable Energy vii Field Validation of Electrochemical Water Filtration System on an Open Loop Cooling Tower at Toyota Motor Manufacturing Plant in Blue Springs, Mississippi consumption at chillers, air compressors, and cooling towers. It also collapses laminar boundaries of the water, leading to better heat transfer. • Chemical usage reduction. The system decreases the reliance on chemicals for water treatment by removing finer particulate compared to traditional filtration systems, thereby reducing the required chemical treatment to maintain water quality. Additionally, with less blowdown, and in turn less makeup water, less water needs to be chemically treated. Methodology The evaluation methodology followed a measurement and verification strategy based on the International Performance Measurement and Verification Protocol Option B— utilizing a retrofit isolation method with all parameter measurements—through comprehensive measurements and analyses of the affected systems. The objective was to compare energy, water, and chemical treatment use with the ElectroCell System compared to the incumbent centrifugal filtration system. Our analysis relied on field data to construct predictive models for energy, water, and chemical treatment use to assess the impact of the proposed technology. Data was collected from February 2022 to February 2023, when the centrifugal system operated, and from February 2021 to February 2022, when the ElectroCell System ran.1 The methodology involved the development of mathematical models for various systems to study the impact from different aspects: • Energy Model. This model predicted electricity consumption based on chilled water load and condenser water entering temperature for each of the chillers. It predicted cooling tower fan energy based on the cooling tower heat of rejection and approach temperature. The electricity consumed by the compressed air system was modeled based on compressed air flow and pressure. The electricity consumed by the respective filtration systems was also considered based on metered data throughout the entire evaluation period. • Water Model. The water model predicted makeup water use based on cooling tower heat of rejection, ash house recovery volume, and makeup water total dissolved solids. • Chemical Treatment Model. This model calculated the chemical treatment costs per kilogallon of blowdown rate for each of the inhibitors and biocides. Each model’s goodness-of-fit characteristics were evaluated to ensure they met International Performance Measurement and Verification Protocol criteria. The energy, 1 The ElectroCell system was installed in August 2018. Data was collected about its operation from February 2021 to February 2022, at which point the incumbent centrifugal system was operated and data collected about its performance for a year, from February 2022 to February 2023. Toyota Motor Manufacturing Mississippi then switched back to the ElectroCell system after the evaluation. U.S. Department of Energy | Office of Energy Efficiency & Renewable Energy viii Field Validation of Electrochemical Water Filtration System on an Open Loop Cooling Tower at Toyota Motor Manufacturing Plant in Blue Springs, Mississippi water, and chemical impacts were determined by comparing actual use with the centrifugal system to modeled use with the ElectroCell system. Project Results/Findings Based on our analysis, the energy consumption associated with the chillers showed a reduction ranging from 1.1%–1.4%, while the energy impact associated with the air compressors showed an improved efficiency of 2.9%–3.3% compared to baseline. The water analysis showed 8%–15% less makeup water usage and 45% less chemical treatment use. It should be noted that while the evaluation was normalized to all pertinent available factors using rigorous measurement and verification approaches and sound statistical techniques, there may have been other unknown factors outside of the evaluation boundary that could have influenced the results. These findings are based on the evaluation of this technology at the selected site and its specific configuration and set of operating conditions. The performance of filtration systems depends on site-specific factors like existing equipment conditions, ambient air quality, particulate matter presence, and seasonal variations. It is influenced by wet bulb temperature and the quality of makeup water, including hardness, pH, and TDS levels, all of which play a significant role in water and chemical usage and require careful consideration for implementation.