2018

The Future Cost Projection of Redox Flow Battery

Redox flow battery (RFB), as an electrochemical storage technology that utilizes chemical properties of different electrolytes to reserve and release energy, has huge potential in the future energy market. This thesis compiles new lists of component cost inputs from both prior study and experts and deeply investigated the future cost projection of vanadium flow battery (VRFB) by a modified cost bottom-up model. The model is a useful tool of assessing the present and future cost in various hour systems with component cost breakdown, as well as being compatible with stochastic analysis to account for the high uncertainty of VRFB’s future cost.

 

The analysis suggested that the cost of 500kW 4-hour VRFB system would fall within a range of 200-545 €/kwh in a bimodal distribution with two maxima at 460 and 295 €/kWh which represents the median cost estimate in future conservative and optimistic scenario respectively in normal case; if both mass production of cell stacks and business model of leasing electrolyte happen in the future, that would result in a radical reduction in cost of VRFB which are 315 €/kWh and 140 €/kWh in future conservative and optimistic scenario, however, regardless of whether these drastic changes might take place, this study indicated VRFB would be the cheapest stationary electrochemical storage system compared to other competitors such as fuel cell and lithium-ion battery.

Figure – System Cost of 1,8 and 24-hour (500kW) system in future optimistic scenario

Chan, C. H. The Future Cost Projection of Redox Flow Battery. Imperial College London, 2018. MSc Thesis. (Download)

Forecasting the material and manufacturing cost of lithium-ion batteries for electric vehicles with commodity price feedback

Electric vehicles are an important tool to decarbonise transportation and are expected to grow rapidly over the next decade. This thesis studies the supply and cost of commodities that make up the functional material in lithium-ion batteries. Commercial battery cells commonly use lithium, nickel, cobalt, and graphite. If high levels of electric vehicle demand occur, the supply for elements such as lithium and cobalt will primarily be supplied for lithium-ion batteries. An experience curve model is used to inform future cost improvements in lithium-ion batteries based on previous prices and projected manufactured capacity by scenario. The experience curves are calculated by isolating the commodity cost from the value-added cost and projecting industrial learning only on the value-added cost. This way, commodity price forecasts can act as a floor on the cost of a lithium-ion battery.

 

This thesis finds that neither lithium, nickel, nor cobalt appears to be a showstopper for lithium-ion batteries, but also that a significant increase in production will need to occur over the next decade. The experience curve analysis suggests that higher commodity prices could offset any acceleration in battery cost reductions. Therefore,  an analysis of the growth of EVs should consider fluctuations in the price of commodities.

Figure – “Base Plus” scenario yearly LIB pack price calculated by the least-squares commodity floor method
compared with the share of pack price for commodities.

Murray, N. Forecasting the material and manufacturing cost of lithium-ion batteries for electric vehicles with commodity price feedback. Imperial College London, 2018. MSc Thesis. (Download)

2017

Comparative lifecycle assessment of different energy storage technologies

The great variety of energy storage technologies make it difficult for decision makers to select the most appropriate, while usually the environmental performance is not included in the selection criteria. This study is trying to address this issue and provide transparent evidence for the environmental impacts of different energy storage technologies. A comparison between the eight most promising and mature technologies was conducted (PHS, CAES, Flywheel, Fuel cell, Li-Ion, Lead-Acid, Sodium-Sulphur, Vanadium redox-flow). After a careful collection of input data, the different systems were modelled per kilowatt hour of storage capacity and then analysed based on three different characterization methods (Recipe, GWP and CED). Results indicate that CAES technology presents the best performance in all three impact methods followed by the NaS battery which shows the lowest environmental impacts among the battery systems.

Figure – Comparison of Global Warming Potential (GWP) per kWh of storage capacity among the 8 technologies. PHS has the highest contribution to global warming (312 kg CO2 eq.), followed by hydrogen/fuel cell with 301 kg of CO2 equivalent. CAES shows the best performance. For PHS cement, the electricity for construction and the gravel had the highest impacts with 173, 50 and 31 kg CO2 equivalent respectively. These three elements account for 81% of the PHS plant’s total GWP value.

Antoniadis-Gavriil, A. Comparative lifecycle assessment of different energy storage technologies. Imperial College London, 2017. MSc Thesis. (Download)

UK electrical energy storage: Quantifying the impact of policy barriers on the residential investment case

This study examines the impact of policy issues on the investment case for UK homeowners adding electrical energy storage (EES) to existing solar systems. Interviews were conducted with EES providers and energy policy experts to establish the major policy issues. A techno-economic model of a lithium-ion battery was created to evaluate the investment case and quantify the impact of policy on annual income and return on investment.


Six policy issues were identified: (1) lack of ToU tariffs, (2) VAT rate uncertainty (3) the level and eligibility for subsidy (4) “deeming” (5) the absence of a market for network savings and (6) finance costs. Analysing the impact of these issues on the investment case highlights the significant boost incremental income provides returns, suggesting that enabling storage to access multiple revenue streams (“revenue stacking”) should be the focus of current policy. Reducing the initial capital cost (either via subsidies or a lower VAT rate for example) has a much bigger benefit to the investment case as losses reduce.

Figure – The impact of policy measures on returns was compared to the base case scenario, a 4kWh battery purchased in 2020 and paired with a 4kWp solar system, where returns were discounted using a cost of capital (r) of 5%. (1) lack of ToU tariffs, (2) VAT rate uncertainty (3) the level and eligibility for subsidy (4) “deeming” (5) the absence of a market for network savings and (6) finance costs.

Gardiner, D. UK electrical energy storage: Quantifying the impact of policy barriers on the residential investment case. Imperial College London, 2017. MSc Thesis. (Download)

How do residential lithium-ion batteries perform in a cradle-to-gate life cycle assessment?

The increasing presence of the lithium-ion battery technology for residential energy storage has triggered the need for comparison in terms of the environmental impact potential of the different chemistries which are currently in use. The LFP-C, LMO-C, NMC-C and NCA-C combinations of cathodes and anodes are privileged by manufacturers as their high power output,  energy density and cyclability make them suitable for residential application. A cradle-to-gate life cycle assessment approach was used and the end of life stage was also modelled. Two functional units where used: the environmental impact potential per kilogram of manufactured battery; the environmental impact potential per lifetime energy stored. None of the batteries convincingly outperformed the others. Nevertheless, the LFP-C and NMC-C are showing a slight advantage. The findings of this study also suggest that increasing the recycling rate of the batteries would help offset the environmental footprint of their production significantly.

Figure – Ecosystem damage potential, component contribution, per kg FU

Le Varlet, T. How do residential lithium-ion batteries perform in a cradle-to-gate life cycle assessment? Imperial College London, 2017. MSc Thesis. (Download)

Electrochemical “Pipelines”: A techno-economic investigation of mobile energy storage transmission

The following report addresses deficiencies in existing electricity transmission methods and investigates the techno-economic feasibility of a novel transmission method. Mobile energy storage transmission (MEST) is a theorized electricity conveyance method that employs energy storage technology, in conjunction with freight transportation, to integrate grids that are separated by bodies of water or significant geographic features. Through development of an integrated approach and subsequent investigation of three distinct case studies, this report concludes that mobile energy storage transmission (MEST) is technologically and economically feasible for present use in niche applications, and future use in a range of macroscopically significant applications. This analysis concludes that MEST has substantial potential to become a competitive alternative to submarine cable transmission and a facilitator of both electricity market integration and grid connection for deep offshore wind projects. 

Figure – MES-Cable Comparison – Case Study 1: Monhegan Island

Macklis, A. Electrochemical “Pipelines”: A techno-economic investigation of mobile energy storage transmission. Imperial College London, 2017. MSc Thesis. (Download)

Cost-effective electricity storage: Who will be the winner?

Levelized cost of storage (LCOS) refer to the lifetime cost of electricity discharged from a storage device. It is a suitable metric to compare different electricity storage technologies application-specific. This study projects the evolution of LCOS for 9 electricity storage technologies in 13 power system applications based on possible cost and performance improvements.

 

Lithium-ion battery and flywheels are the most promising technologies for services requiring short and frequent activations such as frequency response or voltage support. Supercapacitors also have a potential for this kind of application. Pumped-hydro storage and CAES are likely to be the best suited technologies for services requiring a long duration of activation such as arbitrage or bulk storage. As long as it follows a substantial investment reduction, hydrogen electrolysis combined with fuel cell conversion can become competitive in the future for that kind of service. Vanadium redox flow and sodium sulphur batteries have the potential to become the most polyvalent technologies, able to provide storage services with moderate duration and frequency of activation.

Figure – Evolution of LCOS and most cost-competitive electricity storage technologies in 13 power system applications for 9 investigated technologies. 

Mechior, S. Cost-effective electricity storage: Who will be the winner? Imperial College London, 2017. MSc Thesis. (Download)

Oliver Schmidt

Centre for Environmental Policy (CEP)

​South Kensington Campus

Imperial College London

London SW7 2AZ, UK

tel: +44 79 345 487 36

e-mail: o.schmidt15@imperial.ac.uk

LinkedIn: www.linkedin.com/in/oliver-schmidt/