Monday, November 4, 2013

Journal of Cleaner Production publication: Simulation of e-bike systems.

Journal of Cleaner ProductionWe just published another article on simulation of e-bike sharing station, focusing on simulating demand parameters and optimizing station design (e.g., number of bikes, batteries etc). Our TRR paper is still in press too and can be downloaded here

Electric bike sharing: simulation of user demand and system availability  

Shuguang Ji, Christopher R. Cherry, Lee D. Han, David A. Jordan

Suggested Citation:
Ji, S., Cherry, C.R., Han, L.D., Jordan, D.A. (2013) Electric bike sharing: simulation of user demand and system availability. Journal of Cleaner Production. DOI:10.1016/j.jclepro.2013.09.024 (In Press).
This paper describes the operational concepts and system requirements of a fully automated electric bike (e-bike) sharing system demonstrated through a pilot project at the University of Tennessee, Knoxville (UTK) campus (deployed in September 2011). This project is part of a movement to develop a sustainable transportation system, and is one of the green initiatives on UTK campus. E-bikes are more energy efficient and produce fewer greenhouse gas (GHG) emissions per person compared to other transport modes such as car, bus, and motorcycle. Without empirical demand information for an e-bike sharing system, we simulated the operations of such a system to gain insights during the design process before field deployment.  The simulation exercise focused on three critical demand parameters – distributions of trip rates, trip lengths, and trip durations – and coupled them with supply parameters – number of e-bikes, number of swappable batteries, and battery recharging profiles. The primary purpose of these simulations is to evaluate the efficiency of an off-board battery recharging system, where the depleted battery is removed from an e-bike upon its return and inserted into one of the charging slots at the kiosk. We tested various scenarios with different number of batteries always maintaining an initial condition with the battery to e-bike ratio greater or equal to 1.0 to ensure battery availability. We applied empirical battery recharging rates and system operations rules to determine the number of e-bikes and batteries available under different potential demand situations, with a focus on optimizing the number of batteries to meet user demands. By adjusting input parameters, numerous scenarios were simulated for sensitivity analysis. Based on the results of the simulation, this paper presents a cost constrained e-bike sharing system design that can maintain a high level of system reliability (e-bike and battery availability) through optimal battery charging and distribution management. We found that high demand scenarios require multiple swappable batteries per e-bike to reasonably meet the maximum demand. Trip duration has the most influence on e-bike and battery availability, followed by trip rate, and then trip length.

Thursday, September 12, 2013

Report: Findings from first year

There has been a flurry of interest in our program from around the world over the past several weeks. It seems that e-bike sharing is getting more mainstream. Many have asked for data or information on our system use. We have one published paper that describes some of our main findings from our first year, to be published in the Transportation Research Record soon. Instead of waiting, below is a link to the peer-reviewed preprint. We will update the file when the final paper is ultimately published. We have a couple of other interesting papers coming out of this system so stay tuned.

 North America’s first e-bike share: A year of experience

Friday, August 30, 2013

cycleUshare is back...sort of

Greetings. We've been getting some queries related to the e-bikeshare on UTK campus along the lines of "what's going on with the system?". Those around campus might have noticed we shut down the system over the summer to reduce our maintenance requirements (when most of our registered users are gone) and to give us time to reflect on next steps. This project was conceived to meet a few objectives -- research, education, service, and technology creation. We were given a limited timeline to do this by the campus administration, a pilot test with a sunset date (last spring). We've met many of those objectives. We have a couple of journal articles in press, Casey Langford finished his dissertation using the e-bikeshare system as a platform that will create a couple of more journal articles, we've presented the research at (inter)national conferences, we've presented the technology to the public at many venues, we've worked to disseminate the technology to others who can replicate it. However, without approval from administrators and a clearly sustainable direction, we could not move forward aggressively on next steps, thus we've been quiet until now. We can officially say now that the UT administration has given us approval (last week) to continue operating the system for the sake of the research and all the other benefits that come from that. We are now in the process of assessing the relaunch strategy, working through new technology development and generating a sustainable funding stream for the system operation and research endeavors. As we move forward, we will give more information, but we intend to get the system back up and running this semester, hopefully while the weather is nice. If you are interested in using the system, click on the volunteer form and give us your information and we will contact you when we get the system back online. Thanks to the UT community and administration for supporting this endeavor.