Andrew Curtis Elmore

A Field Validated Model of a Vanadium Redox Flow Battery for Microgrids

The vanadium redox flow battery (VRB) is well-suited for applications with renewable energy devices. This paper presents a practical analysis of the VRB for use in a microgrid system. The first part of the paper develops a reduced order circuit model of the VRB and analyzes its experimental performance efficiency during deployment. The model parameters of the various VRB system components were estimated from experimental field data. The parasitic losses of the circulation pumps power consumption were predicted during different operating situations. The second part of the paper addresses the implementation issues of the VRB application in a photovoltaic-based microgrid system. Commercially available chargers designed for lead-acid battery systems were shown to be non-optimal for VRB systems and a new dc-dc converter control was proposed to provide improved charging performance. The system model was validated with field-obtained experimental data.

Optimal Sizing of a Vanadium Redox Battery System for Microgrid Systems

The vanadium redox battery (VRB) has proven to be a reliable and highly efficient energy storage system (ESS) for microgrid applications. However, one challenge in designing a microgrid system is specifying the size of the ESS. This selection is made more complex due to the independent power and energy ratings inherent in VRB systems. Sizing a VRB for both required power output and energy storage capacity requires an in-depth analysis to produce both optimal scheduling capabilities and minimum capital costs. This paper presents an analytical method to determine the optimal ratings of VRB energy storage based on an optimal scheduling analysis and cost-benefit analysis for microgrid applications. A dynamic programming (DP) algorithm is used to solve the optimal scheduling problem considering the efficiency and operating characteristics of the VRBs. The proposed method has been applied to determine the optimal VRB power and energy ratings for both isolated and grid-connected microgrids, which contain PV arrays and fossil-fuel-based generation. We first consider the case in which a grid-tie is not available and diesel generation is the backup source of power. The method is then extended to consider the case in which a utility grid tie is available.

Performance Prediction of a Vanadium Redox Battery for Use in Portable, Scalable Microgrids

Vanadium redox batteries (VRBs) have proven to be a viable energy storage technology for portable microgrids due to their rechargeability and high energy density. VRBs exhibit parasitic load loss during operation due to pumping of electrolyte across the membrane during charging and discharging cycles, as well as required temperature control in the form of heating, ventilation and air conditioning. This paper focuses on empirically characterizing VRB efficiency based on known climatic operating conditions and load requirements. A model is created to determine system performance based on known climatic and load data collected and analyzed over an extended time period. A case study is performed using known data for a week time period to characterize system performance, which was compared to actual system performance observed during this same time period. This model allows for appropriate sizing of the PV array and discretionary loads based on required energy density of the system.

Performance Characterization for Photovoltaic-Vanadium Redox Battery Microgrid Systems

The integration of photovoltatics (PV) and vanadium redox batteries (VRB) in microgrid systems has proven to be a valuable, environmentally friendly solution for reducing the dependency on conventional fossil fuel and decreasing emissions. The integrated microgrid system must be characterized to develop appropriate charging strategies specifically for VRBs, sizing microgrid systems to meet a given load, or comparing the VRB to other energy storage technologies in different applications. This paper provides a performance characterization analysis in a PV-VRB microgrid system for military installations under different conditions of load and weather. This microgrid system is currently deployed at the Fort Leonard Wood army base in Missouri, USA.

Microgrid application with computer models and power management integrated using PSCAD/EMTDC

This paper presents a PSCAD/EMTDC simulation of a microgrid system based on component modeling of a PV array, Wind Turbine, VRB, Fuel Cell, Diesel Generator and a Bi-directional Inverter. Power management for the microgrid is proposed and discussed.

A Balance-of-Plant Vanadium Redox Battery System Model

The vanadium redox flow battery (VRB) is well suited for renewable energy applications. It has many attributes, which make it an excellent choice for bulk power applications. However, as with all energy storage systems, the energy storage device must consider the balance of plant in computing performance efficiencies. This paper studies VRB use within a microgrid system from a practical perspective. A reduced order circuit model of the VRB is introduced that includes the losses from the balance of system including system and environmental controls. Experimental field data are collected to estimate the key parameters of the VRB system. The proposed models include the circulation pumps and the heating, ventilation, and air conditioning system that regulates the environment of the VRB enclosure. In this paper, the VRB model is extended to include the energy storage system environmental controls to provide a model that provides a more realistic efficiency profile.

Monte Carlo Simulations of Wind Speed Data

A new Monte Carlo simulation procedure and nearby regional weather station data are used to predict wind speed and turbine energy. The evaluation of the predication values used cumulative distribution function (CDF) graphs. The predication process employed Weibull shape and scale values developed from 1, 12, 20 and 24 years of record for each weather station. Simulation using one year of wind speed data of a weather station located downwind of the wind turbine site resulted in the greatest match of simulation results to the measured values[ED1]. Most simulations of energy values were a closer match to the measured values than those of wind speed. A closer match was defined as simulated values in the CDF central range of 10 to 75 percent which is also a 25 to 75 percent probability factor.

Capture Zone Comparison for Photovoltaic Microgrid-Powered Pump and Treat Remediation

AbstractPump and treat groundwater remediation systems typically rely on utility power to continuously pump contaminated groundwater to an above-ground treatment unit. The use of renewable energy for a pump and treat remediation system reduces the output of harmful greenhouse gases and the need for coal-based utility power. This paper describes a hypothetical renewable energy-powered pump and treat remediation system that uses an off-grid photovoltaic array to power a submersible solar water pump. The pump operates on an intermittent schedule predicted by available solar irradiance. The intermittently operated pump generates an effective capture zone defined by multiple transient capture zones. Effective capture zones are modeled using Visual MODFLOW and MODPATH and compared against a continuously pumped steady-state capture zone. The comparison showed that a renewable energy-powered intermittently pumped remediation system performs 90% as effectively as a utility-powered continuously pumped remediation s...

Computer models for microgrid applications

This paper provides the development and field validation of the following microgrid components: a 1 kW wind turbine generator, 2.5 kW solar panel, 5 kW vanadium redox battery (VRB), and a 2 kW fuel cell with hydrogen storage.

Development of a Mobile Water Disinfection Unit Powered by Renewable Energy

Following such natural disasters as Hurricanes Katrina and Ike and the 2010 Haiti earthquake, supplying a reliable source of clean drinking water has apparently become essential. Providing a water supply and the associated transportation of potable water is a considerable burden on recovery efforts following a natural disaster. To reduce this burden and meet the water requirements of a community, a low-maintenance, low-cost trailer-mounted water disinfection system has been developed that has the capability to provide potable water from local surface water bodies until the infrastructure is repaired. To achieve disinfection of contaminated surface water, the system uses a series of prefilters and an ultraviolet (UV) disinfection unit. The system is powered using a hybrid photovoltaic array and wind turbine system. To increase the storage capability and decrease the maintenance required by the system, traditional, relatively high-maintenance batteries have been replaced with an ultracapacitor to store the ...