Summary of the project

Objectives

The main objectives of the network were to review and assess existing storage technologies in the context of renewable energy applications, to facilitate exchange of information between the main actors and to propose appropriate RTD actions for the future. More detailed objectives were:

1. To review all possible storage technologies the most suited to renewable energy systems
2. To compare and assess the most relevant features and then to propose the best scope of application of each storage technology.
3. To deliver the results of past and current research carried out on a national or international basis to potential users (laboratories, PV or wind systems suppliers, renewable energy project managers).
4. To facilitate collaboration and exchange among EC-supported research projects in this field.
5. To help identify research priorities and publish a 5/10 years RTD roadmap.
6. To encourage the formation of new RTD partnerships.
7. To foster cooperation between battery manufacturers and renewable energies system designers or suppliers.
   
   
   

Context

Intermittent renewable energies include mainly solar and wind energy. These two types of generators supply DC or AC electricity in an intermittent manner, which then has to be stored to match the demand. The storage function may be done through various ways : rechargeable or "secondary" batteries, but also supercapacitors, flywheels, electrolysers, hydrogen storage and fuel cell systems, and compressed air with electromechanical systems. In all cases, electricity is considered as both the input and the output of the storage. Any storage technology presents specific features which often are a compromise between many options:

the cost,
the overall efficiency,
the capacity to withstand a wide range of cycling conditions,
the self-discharge rate,
the specific power and energy,
the rechargeability,
the optimal operating temperature, etc.

Any application emphasises its own needs : the traditional car battery industry was mainly concerned about cost and high current at low temperature. All recent developments in the field of advanced batteries are driven by portable applications (laptops and computers) or electric vehicles, for which specific power and energy demand and rate of recharge are the key criteria. These requirements are almost exactly the opposite of what renewable energy systems require: The main concerns usually are the cost, the lifetime cycling conditions, the efficiency, and self-discharge for mid and long-term storage.

Work plan

This work started with a brief review of the available storage technologies. The requirements of the main types of renewable energy systems was then listed. This resulted in a list of technical criteria, which formed the basis to compare the performance of all storage technologies. The advantages and drawbacks of each technology were underlined, and the gap between the conventional lead batteries and new candidates was evaluated. Storage technologies were also assessed from an economic standpoint, and their environmental impact was considered. The project finally included the writing of a strategy document for future R&D.