Solar Photovoltaic Cells: Principle and Construction

Fuel Cells

• Solid Oxide Fuel Cell (SOFC):
  • Operates at high temperatures (around 800-1,000°C)
  • Suitable for stationary power generation and certain industrial applications
• Direct Methanol Fuel Cell (DMFC):
  • Similar to PEMFC but uses liquid methanol as the fuel
  • Commonly used in portable electronic devices and small power systems
• Phosphoric Acid Fuel Cell (PAFC):
  • Uses phosphoric acid as the electrolyte
  • Commonly used in stationary power plants, offering high efficiency
• Applications of Fuel Cells:
  • Transportation: used in fuel cell vehicles (FCVs) and buses as a clean alternative to traditional internal combustion engines
  • Stationary Power Generation: used to generate electricity for homes, businesses, and industries
  • Backup Power Systems: provide reliable backup power for critical systems, such as data centers and hospitals
  • Portable Power Systems: used in portable electronic devices like laptops and mobile phones
  • Remote Power Systems: used in off-grid or remote locations to provide reliable and clean power
  • Military Applications: used in military applications for power generation in remote locations, submarines, and unmanned vehicles
  • Space Exploration: used in space missions to generate electricity on spacecraft

Geothermal Energy Resources

• Hot Dry Rock (HDR) system:
  • Also known as Enhanced Geothermal Systems (EGS)
  • Aims to harness heat from deep within the Earth's crust, particularly from areas where conventional geothermal resources are not readily available
• Principle of Operation:
  1. Drilling: deep wells are drilled into hot rock formations
  2. Hydraulic Fracturing: water is injected at high pressure into the wellbore to create fractures in the hot rocks
  3. Water Circulation and Heat Extraction: water is circulated through the created fractures, where it absorbs heat from the hot rock
• Advantages of HDR systems:
  • Geographical flexibility: not limited to specific geological settings
  • Scalability: have the potential for scalability, allowing for the development of larger and more powerful geothermal projects
  • Resource expansion: can potentially expand the reach of geothermal resources to areas where conventional geothermal reservoirs are not present

Solar Photovoltaic (PV) Cells

• Principle:
  • Convert sunlight directly into electricity
  • Based on the photovoltaic effect, which is the generation of an electric current in a material when exposed to light
• Construction:
  • Semiconductor material: typically made of silicon
  • Doping: creates regions with excess electrons (n-type) and regions with a deficiency of electrons or "holes" (p-type)
  • Metal contacts: placed on the top and bottom surfaces of the semiconductor to allow the flow of electrons
  • Anti-reflective coating: applied on the top surface to minimize the reflection of sunlight and maximize light absorption
  • Encapsulation: protects the semiconductor from environmental factors
• Working:
  • Photovoltaic effect: frees electrons from their bound state, creating an electric field
  • Electron movement: electrons move towards the n-type region, while holes created by the absorbed photons move towards the p-type region
  • Generation of electricity: creates an electric current
• Conversion efficiency: measures how effectively a solar cell converts sunlight into usable electricity
  • Influenced by various factors, including material quality, cell design, anti-reflective coating, temperature, and solar spectrum

Types of Geothermal Systems

• Vapor-Dominated Systems:
  • Found in high-temperature reservoirs where the dominant phase is steam
  • Steam is extracted directly from the reservoir and used to drive turbines for electricity generation
• Liquid-Dominated Systems:
  • Found in reservoirs where water is the dominant phase, typically at moderate temperatures
  • Water is extracted and used for its heat content rather than converting it into steam
• Flash Steam Systems:
  • Applies to both vapour-dominated and liquid-dominated reservoirs
  • Involves the extraction of high-pressure hot water from the reservoir, followed by a rapid reduction in pressure to create steam
• Binary Fluid Systems:
  • Suitable for low- to moderate-temperature resources
  • Utilizes a secondary (binary) fluid with a lower boiling point than water
• Total Flow Concept:
  • Combines direct use and electricity generation in a single system
  • Utilizes the total flow from a geothermal reservoir for various applications