T2.1

• The Sun formed 4.6 billion years ago and is estimated to last 5 billion more
• The Sun is the main source of energy for all processes in the Earth-atmosphere system, constituting more than 99.9% of this system
• The Sun is a luminous gaseous star with a mass of 1.989 x10^30 kg and a diameter of 1.39 x10^6 km
• The Sun's chemical composition is approximately 91.20% hydrogen, 8.70% helium, and less than 2% other elements
• The Sun emits energy in the form of electromagnetic radiation (photons) that travels at the speed of light in a vacuum
• The Sun's energy is generated within the core by nuclear reactions, converting hydrogen into helium
• The Sun's temperature is about 14 x10^6 K in the core and 5760 K in the surface
• Solar energy is an important, clean, cheap, and abundantly available renewable energy
• Solar energy received on Earth is affected by atmospheric clarity, degree of latitude, etc.
• Solar power is expressed in terms of W/m^2 or kW/m^2.
• Solar energy advantages include low impact of installation, minimal maintenance, and direct use in various applications
• Solar energy's main drawback is its current lack of competitiveness due to performance issues and large initial investments
• Irradiance is the incident power per unit area of all types of electromagnetic radiation
• Insolation is the accumulation of average energy over a period of time
• Albedo is a fraction of incoming solar radiation reflected back into space
• Solar energy arriving at Earth is distributed with 47% reaching the Earth's surface
• Essential subsystems in a solar energy plant include solar collectors, energy transport mediums, and energy storage
• Solar thermal energy (STE) is a form of energy and technology for harnessing solar energy to generate thermal energy or electrical energy for use in industry, residential, and commercial sectors
• The first installation of solar thermal energy equipment occurred in the Sahara Desert around 1910, where a steam engine was run on steam produced by sunlight
• Solar thermal collectors are classified as low-, medium-, or high-temperature collectors
• Low-temperature collectors are flat plates used for heating swimming pools
• Medium-temperature collectors are flat plates used for heating water or air for residential and commercial use
• High-temperature collectors concentrate sunlight using mirrors or lenses and are used for heat requirements up to 300 degrees Celsius and 20 bar pressure in industries and for electric power production
• Concentrated Solar Thermal (CST) is used for heat requirements in industries, while Concentrated Solar Power (CSP) is used when the heat collected is for power generation
• Solar thermal collector systems gather heat from solar radiation and transfer it to a heat transport fluid, which then delivers it to thermal storage tanks, boiler steam generators, or heat exchangers
• Thermal storage systems store heat for a few hours and release it during cloudy hours and at night
• Thermal-electric conversion systems receive thermal energy and drive steam turbine generators or gas turbine generators to supply electrical energy to loads or the AC grid
• Non-concentrating collectors have a concentration ratio of 1 and are suitable for heating to temperatures below 100 degrees Celsius
• Flat Plate Collectors (Glaze Type) are simple in design and absorb both direct and diffuse radiations for heating
• Advantages of flat plate collectors include utilizing beam and diffuse radiation for heating and requiring less maintenance
• Disadvantages of flat plate collectors include large heat losses, no sun tracking, and achieving low water temperatures
• Concentrating collectors collect solar energy with high intensity using reflectors or refractors for medium and high-temperature applications such as steam production for electricity generation
• Concentrating collectors require tracking to follow the sun and have an efficiency between 50-70%
• FPC with Reflectors use mirrors to concentrate more radiation on the absorber, achieving higher fluid temperatures than flat plate collectors
• Lens Focusing Type uses fresnel lenses to concentrate radiation at a focus line
• Compound Parabolic Collectors have high concentration ratios and require tracking to follow the sun
• Parabolic Dish Collectors have mirror-like reflectors and can reach temperatures up to 2000 degrees Celsius, with higher efficiency for converting solar energy to electricity
• Center Receiver Type (Solar Power Tower) uses flat tracking mirrors to reflect solar energy to a central receiver mounted on a tower, achieving high concentration of energy
• Advantages of concentrating collectors over flat collectors include reduced absorber size, lower thermal losses, and increased efficiency at high temperatures
• Reflectors can cost less per unit area in concentrating collectors, and they can be used for electric power generation