​ Storing our energy: Summary document of a Royal Society of Chemistry Steering Group

ECB Bulletin July 2010

Introduction

Developing viable means to store energy is becoming an ever-increasing priority. Innovations for generating renewable energy for the national grid will require improved ways to store the electricity that is produced. Alongside this, reducing the emissions of greenhouse gases from transport will also rely on methods to store alternative energy sources. In light of these challenges, the Royal Society of Chemistry has formed a European-wide steering group on electrochemical energy storage chaired by Professor Peter Bruce, from the University of St Andrews. The group has cross-European members from both academia and industry who have been reviewing the best practice to support research and development into electrochemical energy storage devices. The steering group has produced a document to communicate their discussions, and they are now planning activities towards implementing their recommendations.

Ambitious targets

Governments across the world are setting targets to reduce anthropogenic greenhouse gas emissions, especially carbon dioxide (CO₂), by increasing the use of electricity generated by renewable technologies. The EU is aiming to cut CO₂ emissions by 20% from 1990 levels by 2020 [reference1] and to generate 20% of overall energy by renewable resources [reference 2]. The UK has now ratified the EU renewable target goals, which equates to a seven-fold increase in UK renewable energy production from 2008 levels. In addition the UK’s own Climate Change Act requires a reduction of greenhouse gas emissions in the UK, of at least 80% by 2050, and reductions in CO₂ of 26% by 2020 against a 1990 baseline [reference 3]

Renewable electricity generation

Around 25% of all CO₂ emissions in the UK and EU come from electricity generation, and predominantly coal- and gas-fired power stations [reference 4]. The demand for electricity varies widely depending on the season, day of the week and time of day. Countries like the UK, which have a fully interconnected national grid, usually have a base-load of available electricity, with flexible generating facilities able to come on line at short notice. The UK Renewable Energy Strategy aims to derive 30-40% of the UK’s electricity from renewable sources (mainly onshore and offshore wind) by 2020. This is problematic for the national grid because wind energy is intermittent and solar energy is subject to the regular diurnal patterns of supply. To sustain a continuous supply of electricity, there will either need to be sufficient back-up in the form of a flexible power plant (such as coal or gas) or energy will need to be stored at times of high generation for release at times of high demand.

Transport

CO₂ emissions from all transport makes up roughly one third of all global greenhouse gas emissions. The King Review [reference 5] has identified energy storage as one of the enabling technologies for low emission electric and hybrid vehicles, with the aim to reduce CO₂ emissions per kilometre by 30% by 2030 and 90% by 2050. A low-emission vehicle which runs on hydrogen from sustainable resources, and has a 200+ mile range, is also one of the definitive aims identified by the 2007 RSC report, Fuelling the Future [reference 6]. However, there are still significant technological challenges in battery, hydrogen storage and fuel cell development, which need to be addressed. In addition to decarbonising private transport, it is important that other transport sectors are also included, such as the electrification of the entire rail network, along with a move to electric or hydrogen buses and heavy-goods vehicles.

Consumer electronics

The manufacture of energy storage devices for consumer electronics is a growth industry. It is driven by the huge increase in sales of portable electronic devices that require battery power (such as laptops, mobile telephones and digital cameras) and of mains-connected devices that require and use batteries for memory back-up. The development of ever more sophisticated and powerful electronic equipment will require greater amounts of stored energy, most probably at levels that are well beyond the capabilities of conventional batteries. Fuel cells, advanced batteries and other storage technologies have huge potential, however, more research will be required to solve power output and recharge challenges.

Types of energy storage

Batteries

A battery is a device for the chemical storage of electrical energy for subsequent use as direct-current electricity [reference 7]. Conventional batteries are cheap to produce, have a commercially proven technology and are likely to continue to be used for energy storage, despite the following intrinsic limitations:

• They contain toxic lead and cadmium components and therefore cannot be safely scaled up.
• The amount of energy that may be stored or transported, in a given amount of mass, is low.
• They have high self-discharge, meaning that internal chemical reactions reduce the charge stored in the battery over time, thereby decreasing their lifetime.

The following alternatives have potential applications in large-scale static electricity storage:

• sodium-sulphur;
• zebra batteries: already used in transportation;
• redox flow-cell batteries.

However, further research and development is required to resolve problems relating to lifetime, reliability and cost.
Lithium-ion batteries are the dominant energy storage technology for portable electronic devices and have potential to be a key energy source in a number of applications, including electric vehicles.
The voltage, capacity, life-time, and safety of a lithium-ion battery could be improved dramatically depending on the material for the electrodes and electrolyte. Funding for materials research is therefore vital. Up-scaling is required for lithium-ion batteries to be used in vehicles and considerable investments of both time and money are therefore required.
Future research and development into batteries is extremely important:

• Methods of recycling raw materials or replacing rare and expensive metals will have to be found.
• Improved battery performance may be achieved by developing new materials (including nanomaterials) and methods of their synthesis.
• Improved safety could be realised by using novel electrodes and electrolytes.

Supercapacitors

Supercapacitors differ from conventional electrostatic capacitors in that they store electrostatic charge in the form of ions on the surface of materials with very high surface area. Supercapacitors are predominantly used in consumer electronics. They can be charged and discharged quickly and are thus used when a large amount of power is required quickly. Examples of uses include:

• a camera flash;
• an emergency door on an aircraft;
• use in hybrid vehicles for start-up and regenerative breaking systems.

Carbon-hybrid supercapacitors have huge potential because they have higher energy storage capacity than carbon-only supercapacitors, however the lifetime is shorter. More research is needed to realise their full potential. Future research and development into supercapacitors is extremely important to address the challenges in improving cycle life and increasing the voltage of the capacitors. Surface chemistry and materials, such as nanoporous electrode materials, will be key to their development. To successfully introduce supercapacitors to the hybrid vehicle market, production costs also need to be reduced.

Fuel cells

A fuel cell is a means of converting a fuel (e.g. hydrogen and methanol) into electricity. Fuel cells are already used in niche markets and have good potential for further use in:

• vehicles;
• portable electronics;
• static applications.

However, fundamental problems remain in the development of commercially viable fuel cells, such as their lifetime, reliability and production costs. In particular, improvements need to be made in:

• water-free membranes which promote proton transfer to improve their efficiency;
• increasing the porosity of electrode materials;
• the efficiency, life-time and durability of catalysts and finding cheaper alternatives;
• hydrogen infrastructure, including hydrogen storage;
• the purity of the fuels used.

Funding mechanisms

Basic research

Research into new and improved electrochemical energy storage technologies requires an understanding of the basic science relating to the materials used. This calls for knowledge in a diverse range of disciplines – from electrochemistry, to chemical catalysis and corrosion processes, to fundamental electron transfer processes. It is essential that fundamental, as well as applied research, continues to be funded to promote the expansion of relevant scientific knowledge. Training the next generation of chemists must also remain a priority.

Cross-European R&D

Electrochemical energy storage poses long-term challenges that require a sustained investment. European coordination will therefore be essential, especially if we are to remain competitive in the face of the large funding actions seen today in Japan and America. It would be appropriate to have a European-wide agency or institution for energy storage, in the same way as the nuclear fusion or airbus collaboration is organised. A joint institution would also ensure that research is not duplicated and serve as a platform for technology transfer. It could be based mainly on publicly funded research activities to maintain independence; however, it should also allow “buy-in” from industry to help tackle specific problems and enable knowledge transfer.
The independence of the funding process supporting the development of a variety of energy storage solutions must be key. It is vital not to pick early winners in the future funding process for this type of research. Experience has shown that market pull should decide which technology is the most practicable and economically viable.

Knowledge and technology transfer

Encouraging innovation requires the transfer of knowledge and skills from academia into industry. Initiatives set up by the Technology Strategy Board, such as the Knowledge Transfer Networks (KTNs), are intended to facilitate this transfer, and it is essential that this work continues to be supported. The RSC is working with the nano-KTN, who are working on nano-enabled energy storage, with the aim of bridging networks and educating government on the issues. Small and spin-off companies often play a vital role in bringing new emerging technologies from research into development. In the UK, they play a vital role in employing a large proportion of skilled workers and contributing to regional economies. It is essential that these small companies are supported as they are much more vulnerable to market fluctuations, and that they are given access to available European funding.

A vision for the future

European Centres of Excellence

There is a need to focus and strengthen efforts in European research in the development of energy storage devices. As part of this effort, it is necessary to establish (virtual) European Centres of Excellence for energy storage technologies, including batteries, fuel cells and supercapacitors. These would bring together the best people in Europe, and should have an independent testing facility for each energy storage technology. Such a centre would focus on medium- to long-term challenges, and would receive sustained long-term funding. The centre would also serve to promote technology transfer, ensure that research is not duplicated, and allow independent and comparative quality assessment of energy storage devices. It is key that the centre is independent, truly European (with no particular country overpowering the institution) and that bureaucracy is kept to a minimum. CERN or ILL Grenoble could be taken as examples of good joint European scientific ventures.

Collaboration through SusChem

It is essential to gain the support of the European Union in setting up a Centre of Excellence for energy storage technologies. SusChem [http://www.suschem.org/] promotes sustainable chemistry research in Europe and is well placed to take these proposals forward to the European Commission, and to influence the direction of European funding calls. A network for energy storage, leading to a Centre of Excellence, would help strengthen the research base in Europe. Currently, the USA and Japan are the unchallenged leaders in this arena. If Europe wishes to stay independent and be competitive in the future, it is vital that a European research base is fostered now.

References

1. Meeting the Energy Challenge: A White Paper on Energy. DBERR, 2007
2. Directive of the European Parliament and of the Council on the promotion of the use of energy from renewable sources, COM, 2008
3. Climate Change Act 2008, Office of Public Sector Information
4. UK Climate Change Sustainable Development Indicator: 2007 Greenhouse Gas Emissions, Department of Energy and Climate Change
5. The King Review of low-carbon cars, HM Treasury, 2007
6. Fuelling the future, Royal Society of Chemistry, 2007
7. Understanding Batteries, RM Dell and DAJ Rand, RSC Paperbacks, 2001, pg viii
This article is reproduced with the permission of the Royal Society of Chemistry and was originally published in RSC News – Policy Bulletin, March 2010.