6 Introduction to Energy Storage Systems ................................................................................... 4 6.1 Background ............................................................................................................................. 4 6.2 Focus of this Study and Exclusions ......................................................................................... 6 6.3 Definition of Energy Storage Systems and Regulated Energy Storage Systems .............. 7 6.4 Relevance of Regulated Energy Storage Systems in Namibia's Electricity Industry ....... 9 6.5 Regulated Energy Storage Systems .................................................................................... 10 6.6 Electricity-related Services from Energy Storage Systems ................................................ 12 6.7 Integrating Energy Storage Systems into the Electricity Grid ........................................... 13 6.8 Applications and Services of Energy Storage Systems in the Electricity Industry .......... 14 6.9 Charging, Discharging and Scheduling Strategies ........................................................... 19 6.10 Environmental Aspects of Energy Storage Systems .......................................................... 21 6.11 International Lessons Learnt and Best Practices using Energy Storage Systems ........... 21 6.12 Intermittent Renewable Sources and Energy Storage Systems ....................................... 21 6.13 Key Take-Away Messages on Energy Storage Systems in Namibia ........................................................................ 22