Non-Conventional Energy Sources: A Deep Dive
Non-Conventional Energy Sources
Solar (heliothermal, photovoltaic), wind, geothermal, tidal, other sources (wave, ocean thermal), and biomass (including MSW) are key non-conventional energy sources.
Solar Energy
Solar energy can be utilized in two ways: heat (absorbing energy and transforming it into heat) and photovoltaic conversion (directly converting solar energy into electrical energy).
Heat from Solar Energy
A collector absorbs solar radiation and transfers it to a fluid, significantly increasing its temperature. Types include:
- Flat-plate collectors: Consist of an insulated box with transparent glass.
- Concentrating collectors: Focus solar radiation onto a small area to achieve high temperatures.
Central Heliothermal Plants
Solar radiation heats a fluid. This heated fluid passes through a steam generator, driving a steam turbine to produce electricity. The cooled fluid then returns to the collectors to repeat the process.
Types include:
- Distributed collector systems: The fluid passes through multiple collectors before reaching a concentration point, leading to high temperatures and potential thermal losses.
- Central tower systems: A heliostat field of mirrors concentrates radiation onto a receiver. Mirrors track the sun to maintain high temperatures.
Wind Power
Wind power harnesses the kinetic energy of wind. Wind maps are determined by several factors:
- Speed: The most important factor.
- Continuity: Areas with consistently high winds are most suitable.
- Stability: Sites with consistent wind speeds and minimal turbulence are ideal.
- Power density: Indicates the maximum power obtainable.
Wind Farms
Wind turbines (or windmills) are used to convert wind energy. Based on their axis:
- Vertical axis: Utilize wind from any direction and are often ground-level.
- Horizontal axis: The most common type, with a propeller, nacelle, and tower.
Wind turbine design considers the coefficient of utilization and a frequency of 50Hz.
Geothermal Energy
Types include:
- Low-energy sources: Temperatures around 100°C, used for heating, greenhouses, and spas. Cold, pressurized water is heated near heat sources and then extracted.
- High-energy sources: Temperatures reaching 1250°C, used for electricity production. Water turns to steam, driving turbines.
Tidal Energy
Sequence of operation:
- Rising tides fill a reservoir, driving turbines to generate electricity.
- Turbines act as pumps during high tide, creating a reservoir current.
- Falling tides release water, driving turbines and generating more electricity.
- Turbines again act as pumps during low tide, further emptying the reservoir.
Other Energy Sources
Wave power uses wave motion to generate energy. Ocean thermal energy exploits temperature differences between surface and deep ocean water. Both open and closed-loop cycles exist.
Biomass
Biomass is organic matter that, through photosynthesis, produces carbon hydrates. Biomass treatment involves:
- Physical processes: Compaction, drying (for heat treatment), and briquetting.
- Biochemical processes: Aerobic fermentation (producing alcohol) and anaerobic fermentation (producing methane).
- Thermal processes: Direct combustion, dry distillation (pyrolysis), and gasification.
Biofuels can be solid, liquid, or gaseous.
MSW (Municipal Solid Waste)
MSW is a heterogeneous mix of materials from domestic, commercial, and industrial activities. Waste types include:
- Inert waste: Metals, glass, etc.
- Fermented organic waste: Food scraps.
- Combustible waste: Paper, cardboard, etc.