4 - Energy

4.1 - Energy storage and transport

• 4.1.3 - Storage of electricity, batteries
• 4.1.4 - Transmission of electricity

4.2 - Energy production, transmission and conversion

• 4.2.1 - Generators, electric engines and power converters
• 4.2.5 - Turbines
• 4.2.6 - Hydrogen production
• 4.2.7 - Micro-generation and grid connection
• 4.2.9 - Smart grids

4.5 - Renewable Sources of Energy

• 4.5.1 - Geothermal energy
• 4.5.2 - Hydropower
• 4.5.3 - Photovoltaics
• 4.5.4 - Solar/Thermal energy
• 4.5.7 - Wind energy
• 4.5.8 - Waste to energy other

4.6 - Rational use of energy

• 4.6.4 - Energy management
• 4.6.5 - Process optimisation, waste heat utilisation

4.8 - Energy Efficiency

4.9 - Carbon capture and energy

4.10 - Biogas and anerobic digestion (AD)