Energy Fundamentals: Principles, Systems, and Technologies

1. Energy: Basic Concepts

• Energy: The ability to do work; it can be transferred and converted, but not created or destroyed.
• Units: Joule (SI) and kWh are commonly used in energy systems.
• Forms of Energy:
  • Macroscopic: Kinetic, potential.
  • Microscopic: Internal energy (chemical, nuclear, sensible, latent).
• Energy Conservation (1st Law of Thermodynamics):
  • Energy balance of a system: ΔE = Q − L + ΣHi

2. Forms of Energy

• Kinetic energy: Motion-related.
• Potential energy: Gravitational, elastic.
• Internal energy:
  • Sensible (temperature-related).
  • Latent (phase change).
• Mechanical energy: Kinetic + potential + flow energy.
• Electrical & magnetic energy.

3. Energy Transfer Mechanisms

• Heat (Q): Transferred due to temperature differences (conduction, convection, radiation).
• Work (L): Energy transfer not caused by temperature differences.
• Mass flow: Carries internal, kinetic, and potential energy.
• Power: Energy change per unit time.

4. Energy Demand

• Electrical: Lighting, electronics.
• Mechanical: Transport, machinery.
• Internal (thermal): Heating and cooling.
• The building sector is one of the largest energy consumers.

5. Energy Resources

• Renewable: Solar, wind, water, geothermal, biomass.
• Non-renewable: Coal, oil, natural gas, nuclear fuels.
• Key differences: Availability, efficiency consequences, and environmental impact.

6. Renewable Energy Sources (RES)

• Definition: Naturally replenished, practically unlimited.
• Main RES technologies: Solar (thermal & photovoltaic), wind (onshore, offshore), water (hydro, tidal, wave), and geothermal.
• Challenges: Intermittency, need for storage, grid integration, and recycling of materials.

7. Solar Energy

• Solar radiation depends on: Latitude, season, clouds, and time of day.
• Key terms: Irradiance (W/m²) and insolation (kWh/m²).
• Solar thermal: Flat plate, evacuated tube, and concentrated systems.
• Photovoltaics (PV):
  • PV effect vs. photoelectric effect.
  • Cell → module → panel → system.
  • Types: Mono-crystalline, polycrystalline, thin-film, perovskite, multi-junction.

8. Wind Energy

• Origin of wind: Uneven solar heating.
• Wind turbine classification: Horizontal/vertical axis, lift vs. drag-based, onshore vs. offshore.
• Betz limit: Theoretical maximum efficiency of wind turbines.

9. Power-to-Heat (P2H)

• Concept: Using renewable electricity to produce heat.
• Technologies: Electrical heaters and heat pumps.
• Heat pump basics: Transfers heat from a cold to a warm source using work; COP > 1; performance depends on temperature levels.
• Heat storage: Sensible, latent (PCM), and thermochemical.

10. Power-to-Fuel (P2F)

• Purpose: Energy storage and decarbonization of transport and industry.
• Fuels: Hydrogen, methane, methanol, ammonia.
• Hydrogen production methods: Electrolysis, reforming, and thermochemical processes.
• Key challenges: Efficiency, cost, and technology maturity.