Raghunathan Rengasamy

The conversion of nuclear energy into electricity is facilitated by chemical intermediates and molecular products formed during the radiolysis of water. In this work, we hypothesize a novel radiolytic charging approach for redox flow battery electrolytes. Radiolytically produced ionic intermediates and molecular products oxidize or reduce the metal ion solutes in the electrolytes. A qualitative study for choice of redox couples based on electrochemical principles followed by a feasibility study of radiolytic conversion of active material is presented. A framework for an empirical investigation of radioactive source, equipment and dose, and product characterization techniques is discussed. The proposed method finds application in the utilization of spent nuclear fuel (specifically gamma emissions from fission products in early activity stages) as a radiolysis radiation source for electrolyte charging. We present a perspective on future investigations that are required to harness nuclear energy for charging electrolytes and developing a self-operating RFB system.

Electrochemical energy, being a safe and clean renewable energy source, is gaining considerable attention in recent years. The electrochemical energy technologies available are numerous and the choice of technology is usually guided by heuristics. The paper presents a critical review and comparison of three competing electrochemical energy technologies (secondary batteries, fuel cells and flow batteries) based on various characterization criteria like energy & power densities, cost, weight, efficiency, controllability, reliability etc. A rational framework is proposed to characterize the technology best suited for a particular application to achieve the best energy utilization. The idea is posed as a constrained multi objective optimization of design, followed by choice based on gravimetric and volumetric cost comparison of the three systems under consideration. For various combinations of characterization criteria, optimal choice of technology for an extensive scope of power and energy is found using the proposed framework and presented as area plots for easy understanding. This framework is then used to examine the prospects and directions of improvement for emerging technologies. Discussions are presented using the example of Vanadium Redox Flow Battery (VRFB).

Solar heat collection efficiency reduces with increase in temperature of the heating media owing to heat loss. Thermal energy capture is easily carried out using heat exchangers, but there are challenges in converting this to usable power, especially at lower temperatures. An electrochemical system which has reasonable variation in free energy with temperature can be used to capture this low grade energy by charging at a higher temperature. Vanadium Redox Flow Battery (VRFB) is considered as a case study to see the feasibility of this concept. For this purpose, a lumped parameter model of the VRFB system is developed to study the high temperature operation. It is observed that high temperature operation enables charging at lower potentials and achieving higher current density. Based on this study a method for capturing low grade energy using electrochemical systems is investigated.

Increasing demand for electricity, depleting reservoirs of fossil fuels and increasing environmental concerns, call for efficient and clean utilization of available energy. Electrochemical technologies such as batteries, fuel cells and flow batteries are promising alternatives for such clean and efficient energy conversion. While extensive heuristics exist to guide the choice of technology, very little work has been done on development of systematic and rational frameworks to quantitatively benchmark the merits/demerits of potential technologies using a matrix of several factors. In this work, we describe a framework that addresses this gap with a focus on three technologies, viz, batteries, fuel cells and flow batteries. The proposed framework currently evaluates two factors: power and energy density. An algorithm that generates gravimetric and volumetric cost comparisons between secondary batteries, flow batteries and fuel cells is presented. Since the available chemistries are numerous, comparisons are made for the most promising current chemistries for each technology, namely, lithium ion battery, hydrogen PEM fuel cells and all vanadium redox flow battery. For a given application, the algorithm also identifies optimal designs for the corresponding technologies. Generalization of the framework for other factors such as reliability, lifespan, etc. and different chemistries (for each technology) will also be outlined.