This study was conducted to test GRIDbot electric vehicle charging infrastructure for the City of Houston's growing fleet of plug-in hybrid electric vehicles (PHEVs – Prius equipped with Hymotion battery systems) and dedicated electric vehicles (EVs – Nissan LEAFs).
2. Where do the authors work, and what are their areas of expertise? Note any other publications by the authors with relevance to the 6Cities project.
The Houston Advanced Research Center (HARC) lead this study, while working with GRIDbot, Good Company Associates, and the City of Houston. HARC is a not-for-profit organization based in The Woodlands, TX, that focus on research of energy, air, and water issues. Other work that is relevant to my transportation focus in this project include their heavy duty diesel testing lab, used to evaluate and determine the best emissions control technologies, and their multi-institution research campaign in three Ship Channel communities with long histories of air pollution issues (Manchester, Milby Park and Galena Park).
David Hitchcock is the Director of Sustainable Transportation Programs at HARC. He acted as the project director. He has served on several committees dedicated to improving air quality such as the Houston Regional Air Quality Planning Committee and the Transportation Research Board's Alternative Fuels Committee.Before working at HARC, he was the Director of the Joint Center for Urban Mobility Research at Rice Center in Houston.
Jeff Williams, as the HARC Manager of Information Technology, was in charge of the IT/database management and analysis.
Zach Vernon is a GIS/RS Research Associate at HARC, and was responsible for the geospatial analysis.
3. What are the main findings or arguments presented in the article or report?
The replacement of other fleet vehicles with the Nissan Leaf would result in significant reduction of NOx emissions.
Estimates for emissions resulting from electricity production from the Texas electric power grid vary greatly.
Emissions from the production of electricity cannot be directly compared with tailpipe emissions of nonelectric cars.
4. Describe at least three ways that the argument is supported.
On average, the replacement of a vehicle currently in Houston's fleet with the Nissan Leaf would result in annual NOx emission reduction of 8.46 lbs.
Data from the EPA's Air Markets Program lead to an estimate of 0.01 grams/mile estimate of emissions for electricity used in an electric car, which is much lower than comparison vehicles. However, data from the DOE EIA Texas Electricity Profile lead to an estimate of almost 0.1 grams/mile, which is higher than many vehicle emission standards.
Although estimates can be made for emissions due to the electricity produced for electric vehicles, to be comparable with tailpipe emissions, life cycle emission analysis would be necessary. The entire life cycle of gasoline and diesel production vs electricity production is not considered, such as accounting for emissions from the refining process. Furthermore, tailpipe emissions occur within a specific geographic area, and emissions pertaining to power production are treated as point source emissions.
5. What three (or more) quotes capture the message of the article or report?
"Electric vehicle charging infrastructure is essential to meet the needs of the City of Houston’s growing PHEV/EV fleet. This infrastructure is a part of the City’s commitment to reduce fleet vehicle emissions. PHEVs/EVs cannot be successfully deployed without cost effective and consumer friendly support technologies. By facilitating the development of the GRIDbot technology, its more rapid commercialization of this clean technology can be furthered" (pg 1).
"For emission reduction considerations, vehicles and charging stations are somewhat inseparable. As with conventional fuels, one technology enables the other. In the case of EVs, fueling infrastructure ensures that vehicles can operate with zero tailpipe emissions. This is particularly true in the case of PHEVs that can operate primarily in an electric mode. Without adequate charging facilities, such vehicles will rely on conventional fuels. If vehicles cannot be recharged in a timely fashion, emission levels (and energy use) could be no different than conventional vehicles" (pg 10).
6. What were the methods, tools and/or data used to produce the claims or arguments made in the article or report?
Data was collected both from the charging station and the vehicles. The study included two 2011 Nissan LEAFs and three 2009 Toyota Prius hybrid electric vehicles (HEVs) that had been retrofitted with Hymotion battery systems so that they became plug-in hybrid electric vehicles.
GPS vehicle data loggers (specifically, the Qstarz BT-Q1000XT GPS data loggers) were used to track the location and trips of the vehicles. There loggers are battery powered, with an auto shut down feature to conserve battery life. A vibration sensor restarts up the logger when there is enough vibration to indicate possible vehicle use. The self-powered ability of the logger was desirable as it minimizes the driver's visibility and awareness of the unit. During weekly visits to the charging stations, batteries would be swapped out to ensure further ability to log in the next week. Loggers could be removed from the vehicle and plugged into a laptop using a microUSB cable. The data would be saved to the laptop through Qstarz Data Viewer software to be analyzed later.
The Prius Hymotion vehicles had data loggers put into their on board diagnostic (OBD) port. The data logger plugs in under the steering wheel, out of the driver's sight, and is powered by the car. It can be programmed to record multiple variables regarding the vehicles performance. They collected data such as number of trips, time of trips, average speed, and fuel economy. Furthermore, they had the capability to measure the vehicle’s battery system state-of-charge (SOC), including the Hymotion battery system.
Nissan LEAFs come equipped with Nissan’s CARWINGS telematics system.Data that is reported for each trip can be accessed on the internet with an account created for the vehicle. Some available record metrics are date of trip, distance, total energy used, total energy from regenerative braking, net energy used, miles per kWh of energy used, and CO2 reductions. The system also creates graphical visualizations of this data for monthly and annual reports.
GRIDbot charging stations also have an internal data collection system. HARC accessed the data through a SQL Server Linked Server connection, looking for information on event based charging activities for specific vehicles and charging stations, and fundamental measurements of electricity consumption that could be matched to the vehicles.
To account for the emissions resulting from the production of electricity for the electric vehicles, HARC compared estimates of emission rates per unit of energy generated for power generation facilities. Specifically, they looked at the estimates of EPA’s Air Markets Program, EPA’s eGRID, and the DOE’s Energy Information Administration.
7. How (if at all) are health disparities or other equity issues addressed in the article or report?
Health is not addressed, but availability of technologies is, which is related to equity.
The report claims that compared to infrastructure for gasoline or diesel fueling, "EV fueling (charging) has greater flexibility in that it can occur primarily at a private charging station (at home or at restricted facilities such as workplace charging). Public charging facilities are also essential to ensure that vehicle users can refuel (though less frequently)."
This points to the fact that communities or individuals without the resources to provide this infrastructure cannot utilize electric vehicles as a means to reduce are emissions.
8. Where has this article or report been referenced or discussed? (In some journals, you can see this in a sidebar.)
This report is referenced in another report titled GRIDbot Electric Vehicle Service Equipment Installation, which was produced by GRIDbot.
They conducted their report alongside HARC, and utilized HARC's air modeling and data.
GRIDbot acknowledges the use of this study, writing, "The HARC has identified the data sources needed and provided the preliminary findings and analysis of the emissions estimates for these electric vehicles." Source
9. Can you learn anything from the article or report’s bibliography that tells us something about how the article or report was produced?
10. What three points, details or references from the text did you follow up on to advance your understanding of how air pollution science has been produced and used in governance and education in different settings?
11. Does the article provide information or perspective on any of the thematics already identified as important for the 6Cities project?
There have been important developments in capacity to share air quality information.
2. Where do the authors work, and what are their areas of expertise? Note any other publications by the authors with relevance to the 6Cities project.
3. What are the main findings or arguments presented in the article or report?
4. Describe at least three ways that the argument is supported.
5. What three (or more) quotes capture the message of the article or report?
6. What were the methods, tools and/or data used to produce the claims or arguments made in the article or report?
7. How (if at all) are health disparities or other equity issues addressed in the article or report?
8. Where has this article or report been referenced or discussed? (In some journals, you can see this in a sidebar.)
9. Can you learn anything from the article or report’s bibliography that tells us something about how the article or report was produced?
10. What three points, details or references from the text did you follow up on to advance your understanding of how air pollution science has been produced and used in governance and education in different settings?
11. Does the article provide information or perspective on any of the thematics already identified as important for the 6Cities project?