Non-Conventional Energy Sources

Non-conventional energy sources are renewable or alternative forms of energy that are not as widely used as traditional fossil fuels such as coal, oil, and natural gas. As the world faces the challenges of climate change and the depletion of fossil fuels, these sources, including tidal, wave, and solar energy, are becoming increasingly important for a sustainable future.

1. Energy From Tides

Tidal energy is a form of hydropower that converts the energy obtained from the rise and fall of ocean tides into electricity.

Cause: The gravitational pull of the Moon and to a lesser extent, the Sun causes the sea level to rise and fall, creating high and low tides, typically twice a day.

Method of Harnessing: A dam or barrage is built across an estuary or a bay with a large tidal range.

1. High Tide: As the tide comes in, the water level rises. Sluice gates in the dam are opened, allowing the basin behind the dam to fill up.
2. Low Tide: Once the tide has gone out, there is a significant height difference between the water in the basin and the sea. The gates are then opened, and the water flows out, spinning turbines connected to generators to produce electricity.

Some modern systems can also generate electricity from the incoming tide, making them more efficient.

Significance: Tidal power is predictable and reliable but is limited to coastal areas with a significant difference between high and low tides.

2. Energy From Waves

Wave energy is derived from the motion of ocean surface waves, which are primarily caused by wind blowing over the water.

Method of Harnessing: There are many designs for wave energy converters. One notable invention is Salter's Duck.

Salter's Duck: This device consists of a teardrop-shaped float (the "duck") and a connected, more stable balance float. As waves pass, they cause the duck to rock up and down relative to the balance float. This relative motion is used to power a pump or a generator to produce electricity.

Significance: The oceans contain a vast amount of energy in the form of waves. While the technology is still developing, wave power has the potential to be a significant source of renewable energy for coastal communities.

3. Solar Energy

Solar energy is the radiant light and heat from the Sun that is harnessed using a range of technologies. It is the most abundant renewable energy source available on Earth.

Solar Constant: The amount of solar energy that reaches the top of the Earth's atmosphere is about 1.4 kilowatts per square meter (kW/m²).

Surface Intensity: After passing through the atmosphere, which reflects and absorbs some of the energy, the intensity at the Earth's surface on a clear day is about 1 kW/m².

Solar energy can be utilized in two main ways:

a) Solar Thermal Energy

This technology uses sunlight to create heat.

• Flat-Plate Collectors: These are common for domestic hot water systems. A blackened plate under a glass cover absorbs sunlight, and the heat is transferred to water circulating in pipes underneath. Water can be heated up to about 70°C.
• Concentrated Solar Power (CSP): Large mirrors or lenses are used to concentrate sunlight from a large area onto a small receiver. This can generate very high temperatures, producing steam to drive turbines for large-scale electricity generation.

b) Solar Cells (Photovoltaic Cells)

Photovoltaic (PV) cells convert sunlight directly into electricity.

Mechanism: Solar cells are made of semiconductor materials, usually silicon. When sunlight (photons) strikes the cell, it energizes electrons, allowing them to flow and create an electric current.

Solar Panels: A single solar cell produces a very small voltage. To generate a useful amount of power, many cells are connected together in series and parallel to form a solar panel (or module).

Energy Storage: Since solar panels only work during the day, the electricity they generate can be used immediately or stored for later use (for example, at night or on cloudy days). Nickel-Cadmium (Ni-Cd) batteries are one type of rechargeable battery used for this purpose.

Applications: Although historically expensive, the cost of solar cells has dropped significantly. They are used to power everything from small devices like calculators to large-scale power plants. They are also essential for powering satellites and remote installations where a connection to the power grid is not possible.

4. Geothermal Energy

Energy from the heat stored within the Earth is known as geothermal energy. This includes energy from hot springs, geysers, and hot rocks.

5. Energy from Biomass

Biomass is organic material that comes from plants and animals. It contains stored energy from the sun.

Possible Questions and Answers

• Q: What is the "solar constant"?
  A: The solar constant is the amount of solar energy received per unit area per second at the top of the Earth's atmosphere. Its value is approximately 1.4 kW/m².
• Q: What is the difference between solar thermal and photovoltaic (PV) systems?
  A: Solar thermal systems use sunlight to generate heat, which can be used for heating water or creating steam to generate electricity. Photovoltaic (PV) systems use solar cells to convert sunlight directly into electricity.
• Q: Why are solar cells connected together to form a solar panel?
  A: A single solar cell produces a very low voltage (typically about 0.5 V). Many cells are connected in series to increase the voltage and in parallel to increase the current, allowing the panel to produce a useful amount of electrical power.