Advanced Wayside Energy Storage Systems for Rail Transit

Document Type


Publication Date


Subject Area

economics - appraisal/evaluation, economics - benefits, mode - rail, place - north america, technology - alternative fuels


Benefit cost analysis, Case studies, Economic benefits, Energy storage systems, Innovation, Rail transit, Rail transit facilities, Simulation, Transit authorities


This Innovations Deserving Exploratory Analysis (IDEA) project explored the use of wayside energy storage systems (WESS) in rail transit systems. The analysis monetized economic and technical benefits for transit agencies but also considered other stakeholders. The costs and benefits of various applications were modeled through hypothetical simulations as well as case studies using real data from participating transit agencies: Greater Cleveland Regional Transit Authority and Denver Regional Transportation District. Six different WESS technologies were modeled including: flywheels, ultracapacitors, and lead acid, sodium sulfur, lithium ion, and zinc bromide batteries. The cost, benefit, and net present value (NPV) were calculated for seven simulations for a hypothetical transit system and for two case studies. Several key findings are summarized. First, combining applications provides benefits that result in the most attractive NPV. Second, applications that solve a technical problem, such as to address a power quality or reliability issue, may be attractive to a transit agency even if the NPV is not positive. The important consideration is whether WESS is less expensive than the alternative technology. Third, the results for each of the applications could be improved with a reduction in WESS capital cost, which is expected for most technologies over the next few years as they become commercially available and are produced in larger quantities. Fourth, the financial value proposition for WESS would be improved by federal capital grants or other incentives. This project analyzed the value of WESS as an investment made solely by the transit agency without capital funds from other sources. Fifth, this analysis considered the business case for a transit agency and therefore monetized on the benefits that accrue to the transit agency. However, if a societal perspective had been modeled and other benefits were monetized, WESS would likely be much more attractive in these applications.


Permission to publish the abstract has been given by Transportation Research Board, Copyright remains with them.