Introduction to Non-Conventional Energy
Non-conventional energy resources, often called renewable energy, are sources that are naturally replenished on a human timescale. Unlike finite conventional sources like coal and petroleum, they offer a sustainable and environmentally cleaner alternative. The global shift towards these resources is driven by three main factors:
Environmental Concerns
Combustion of fossil fuels releases greenhouse gases (e.g., CO2), driving climate change. Renewables have a minimal carbon footprint.
Energy Security
Reduces dependence on foreign fossil fuel imports, enhancing national security and economic stability.
Sustainability
Fossil fuels are finite. Renewables provide a long-term energy supply for future generations.
Availability of Resources
The potential for renewable energy is immense, though it varies geographically. The sun provides more energy in one hour than humanity consumes in a year.
Indian Context
India has a rich and diverse renewable energy resource base. As of recent data, India's installed renewable capacity has crossed 180 GW.
- Solar: Excellent potential with 4-7 kWh per sq. meter per day in most regions. A cornerstone of India's energy policy.
- Wind: 4th largest installed capacity globally, with strong potential along coastlines and in states like Gujarat and Tamil Nadu.
- Hydropower: Significant potential in the Himalayan region and other major river systems.
- Biomass: High potential from agricultural residue, supporting rural economies.
Classification of Non-Conventional Energy
Renewable energy sources are classified based on their origin. Here's a visual breakdown of the primary types:
Relative Merits & Demerits
| Energy Source | Merits (Advantages) | Demerits (Disadvantages) |
|---|---|---|
| Solar | Abundant, low maintenance, scalable, no emissions. | Intermittent, high initial cost, requires large area. |
| Wind | Low operating cost, efficient land use, no emissions. | Intermittent, noisy, visual impact, remote locations. |
| Hydropower | Reliable, low operating cost, long life, high efficiency. | High upfront cost, major environmental/social impact. |
| Biomass | Uses waste, dispatchable power, carbon neutral. | Can cause deforestation, emits pollutants, land intensive. |
| Geothermal | Highly reliable, small footprint, low emissions. | Geographically limited, high drilling cost, seismic risk. |
Theory of Solar Cells
A solar cell (or photovoltaic cell) converts sunlight directly into electricity via the **photovoltaic effect**. This process relies on a semiconductor structure called a **P-N Junction** to create and separate electrical charges.
Solar Cell Cross-Section
A solar cell is made of several layers working together to convert light into electricity.
The P-N Junction: Heart of the Cell
A P-N junction creates a built-in electric field. It's formed by joining two types of doped silicon:
- N-type Silicon: Doped with an element like Phosphorus, creating an excess of free electrons (negative charge carriers).
- P-type Silicon: Doped with an element like Boron, creating an abundance of "holes" (positive charge carriers).
The Photovoltaic Effect: How it Works
Sunlight hitting the p-n junction drives the entire process:
Solar Cell Materials
1st Gen: Crystalline Silicon (c-Si)
Dominates the market. Based on silicon wafers.
- Monocrystalline (mono-Si): Highest efficiency (18-24%). Uniform black look. Most expensive.
- Polycrystalline (poly-Si): Lower efficiency (15-20%). Blue, marbled look. Cheaper to produce.
2nd Gen: Thin-Film
Use thin layers of material. Flexible and lightweight but less efficient.
- Cadmium Telluride (CdTe): Most common thin-film. Cost-effective.
- Copper Indium Gallium Selenide (CIGS): Good efficiency, complex manufacturing.
3rd Gen: Emerging Tech
Mostly in R&D. Focus on high efficiency and low cost.
- Perovskites: Rapidly improving efficiency but poor stability.
- Organic PV (OPV): Flexible and cheap, but low efficiency and short lifespan.
Solar Array & Power Plant
From Cell to Array: A Modular System
Solar power systems are built by combining smaller units into larger ones to generate usable amounts of power.
Solar Power Plant Overview
A large-scale solar farm feeds electricity into the grid. Its key components and energy flow are shown below:
Limitations of Solar Cells
Despite its benefits, solar power faces several challenges that must be considered for widespread adoption.
Intermittency
Solar panels only generate power when the sun is shining. No power at night and reduced output on cloudy days.
Energy Storage
Requires expensive battery systems to provide a consistent 24/7 power supply, increasing overall project cost.
High Initial Cost
Although prices are falling, the upfront investment for panels, inverters, and installation remains significant.
Land Use
Large-scale solar farms require vast areas of land, which can compete with agriculture or other land uses.
Efficiency Limits
Commercial panel efficiency is typically 17-22%. Much of the sun's energy is lost as heat.
Manufacturing & Disposal
Panel production is energy-intensive and can involve hazardous materials. Recycling old panels is an emerging challenge.