Sources of Energy — 50 Q&A

Energy is the capacity to do work. It exists in many forms — kinetic, potential, thermal, chemical, electrical, nuclear — and is measured in joules (J) or kilowatt-hours (kWh) for electrical energy.

Sources are: Non-renewable (fossil fuels — coal, petroleum, natural gas; nuclear fuel) and Renewable (solar, wind, hydro, biomass, geothermal, tidal).

Fossil fuels (coal, oil, natural gas) are formed from ancient plant and animal remains that were buried and subjected to heat and pressure over millions of years, concentrating carbon-rich materials.

• Advantages: high energy density, established infrastructure, reliable supply.
• Disadvantages: emit CO₂ & pollutants, cause air & water pollution, finite & contribute to climate change.

Crude oil is a mixture of hydrocarbons extracted from underground. Fractional distillation in refineries produces petrol, diesel, kerosene, lubricating oils, and feedstock for petrochemicals.

Natural gas (primarily methane) is used for cooking, heating, electricity generation, and as feedstock in fertilizers. It burns cleaner than coal or oil but is still a fossil fuel producing CO₂.

Coals: lignite (brown coal, low grade), bituminous (used in power plants), anthracite (high carbon, used for heat). Coal is also converted to coke for steelmaking. Burning coal produces ash, SOx, NOx and particulates.

Hydroelectricity converts potential energy of stored water in dams into mechanical energy via turbines and then electricity via generators. Benefits: renewable, low emissions, grid-scale storage (pumped storage). Drawbacks: ecological disruption, displacement, siltation, changes to downstream flow.

Main types: photovoltaic (PV) panels convert sunlight directly to electricity; solar thermal (collectors or concentrated solar power) uses heat for water heating or to drive turbines. Advantages: renewable, low emissions; challenge: intermittency and need for storage.

PV cells are semiconductor (usually silicon) PN-junction devices. Photons generate electron-hole pairs; built-in electric fields separate charges creating current. Cells form modules and arrays; performance depends on irradiance and temperature.

Wind turbines extract kinetic energy from moving air via rotor blades connected to a shaft and generator (often via gearbox). Siting, wind speed distribution, and capacity factor (actual vs rated output over time) determine productivity.

Biomass includes wood, crop residues, animal dung, and organic waste. It can be used directly as solid fuel, converted to biogas (methane) via anaerobic digestion, or processed into liquid biofuels (ethanol, biodiesel).

Biogas is produced by anaerobic digestion of organic waste (dung, kitchen waste) by bacteria in an oxygen-free digester, producing methane-rich gas usable for cooking or electricity, while reducing waste and pathogens.

Geothermal energy uses Earth's internal heat (hot springs, geysers, or hot rock) for direct heating or to generate electricity. It is location-specific and can provide baseload renewable power where resource exists.

Tidal power harnesses rise and fall of sea levels (tides) using barrages or tidal turbines to drive generators. It's highly predictable but limited to suitable coastal locations and poses ecological challenges.

Nuclear power uses fission of heavy nuclei (uranium, plutonium) in a controlled chain reaction to release heat, which produces steam to drive turbines and generators. Pros: high energy density and low direct CO₂; cons: radioactive waste, safety concerns, high capital cost.

Renewable sources replenish naturally over short timescales (solar, wind, hydro). Non-renewable are finite on human timescales (coal, oil, natural gas). Transition to renewables improves sustainability and reduces emissions.

Energy conservation means using less energy by improving efficiency and changing behaviour (insulation, energy-efficient appliances, public transport). It's important to reduce emissions, save costs, and extend resource availability.

Energy density is energy content per unit mass (or volume). Liquid fuels (petrol, diesel) have high gravimetric energy density compared to batteries; coal and gas vary; batteries offer high round-trip efficiency but lower energy per kg than fossil fuels.

Storage options: pumped hydro (large-scale gravitational storage), batteries (lead-acid, lithium-ion), flow batteries, compressed air energy storage, and thermal storage. They help integrate variable renewables and provide grid services.

Capacity factor = actual energy produced over time / (rated capacity × time). It measures utilization — solar and wind have lower capacity factors (intermittent), while nuclear and fossil plants often have high capacity factors (baseload).

Carbon footprint measures greenhouse gas emissions (CO₂-equivalent) from activities. Energy production from fossil fuels is a major contributor; switching to renewables and efficiency reduces the footprint.

Life-cycle assessment (LCA) includes emissions from extraction, manufacturing, operation, and disposal. For example, solar panels and wind turbines have upfront manufacturing emissions but low operating emissions, giving low lifecycle emissions overall.

Energy security is reliable access to affordable energy. Improve it by diversifying sources, increasing domestic renewables, strategic fuel reserves, energy efficiency, and resilient grids.

Smart grids use digital monitoring and control to balance supply & demand, integrate distributed renewables and storage, enable demand response, and improve reliability and efficiency.

Peak load is the maximum electricity demand over a period. Managed by demand-side measures (timers, tariffs), peaker plants, storage, and efficiency to reduce the need for expensive infrastructure.

• LED lighting, energy-efficient motors and appliances.
• Improved building insulation and efficient HVAC systems.
• Efficient industrial processes and heat recovery.

Biofuels (ethanol, biodiesel) are produced from biomass feedstocks. They can reduce fossil fuel use, but may compete with food crops, cause land-use change, and have variable lifecycle emissions depending on production methods.

CCS captures CO₂ from power plants or industry and stores it underground (geological formations) or uses it. It can reduce emissions from fossil-based systems but is costly and requires long-term monitoring.

Cleaner options: LPG, biogas, improved cookstoves, and electric induction stoves. They reduce indoor air pollution and associated health risks compared to open-fire biomass cooking.

Depends on sun-hours. If effective sun-hours = 5 h/day: energy ≈ 1 kW × 5 h = 5 kWh/day. Actual output varies with location, tilt, shading and system losses.

Grid parity is when the cost of generating electricity from a technology (e.g., solar) equals or is less than the retail electricity price. It depends on system costs, financing, subsidies, and tariffs.

Distributed generation refers to small-scale power generation near the point of use (rooftop solar, small wind). Benefits: reduced transmission losses, local resilience, faster deployment; challenges: integration and variability management.

An energy audit assesses where energy is used and wasted in a building or process and recommends measures (insulation, efficient lighting, controls) to save energy and cost.

Peaking plants (e.g., open-cycle gas turbines) can start quickly to meet short periods of high demand. They are costly per kWh but essential for reliability when demand spikes or renewables drop.

LCOE is the average cost per unit of electricity over a plant's lifetime, accounting for capital, operation, fuel, maintenance, and discounting. It's used to compare cost-effectiveness of technologies.

Hybrid systems combine multiple generation and storage (solar + wind + battery + diesel) to provide reliable power, especially useful in off-grid or islanded microgrids and rural electrification.

DSM involves measures to reduce or shift electricity use (time-of-use tariffs, demand response, efficient appliances) to balance loads and lower costs and emissions.

Policy tools: Renewable Portfolio Standards (RPS), feed-in tariffs, auctions, subsidies, tax incentives, and carbon pricing — all help make renewables competitive and attract investment.

Energy transition is the systemic shift from fossil-fuel-dominated systems to low-carbon, renewable-based, efficient, and flexible energy systems — involving technology, policy, infrastructure and social changes.

Hydrogen can act as an energy carrier and storage medium. 'Green hydrogen' produced by electrolysis using renewable electricity can decarbonize hard-to-electrify sectors (industry, shipping) though cost and infrastructure are challenges.

Management includes energy storage, geographic diversification, demand response, flexible backup plants, improved forecasting, and grid upgrades to accept variable inputs.

Impacts include air pollution and CO₂ from fossil fuels, water use and habitat change from hydro, land & material use for solar/wind, mining impacts for battery materials, and radioactive waste for nuclear. Sustainable planning seeks to minimize impacts.

International cooperation provides climate finance, technology transfer, and capacity building to help countries adopt clean energy, meet climate goals, and ensure a just transition considering social & economic needs.

Reliable, affordable energy supports healthcare, education, clean water, industry, and livelihoods. Access reduces indoor air pollution from solid fuels and enables economic development.

A circular approach minimizes material use, increases reuse & recycling (e.g., PV panel recycling, battery second-life), and recovers energy from waste — reducing environmental footprint of energy systems.

• Use LED lighting, efficient appliances, and improve home insulation.
• Prefer public transport, carpooling, and energy-efficient travel options.
• Reduce, reuse, recycle and choose renewable energy where available.

Likely: much higher shares of renewables (solar, wind), flexible storage (batteries, pumped hydro, hydrogen), electrification of transport & heating, improved efficiency and smarter grids for resilience.

• 1 kWh = 3.6 × 10^6 J. Typical thermal plant efficiency ~33–40%; modern gas plants ~50–60%; solar PV module efficiency ~15–22% (system lower).
• Capacity factors: coal/nuclear ~60–90%, gas ~40–70%, wind ~20–50%, solar ~10–25% (location dependent).

• Know types (renewable vs non-renewable), pros/cons and environmental impacts.
• Understand basics of solar, wind, hydro, biomass, geothermal, tidal, nuclear and fossil fuels.
• Remember key concepts: energy density, capacity factor, storage options, conservation, and policy instruments.