Energy Types, Storage, Transmission, and Renewable Energy Systems Study Guide

Course Overview and General Principles

  • Course Content Structure:
    • Part 1: Focuses on energy types, storage, transmission, and conservation.
    • Part 2: Focuses on energy mixes within engineering, economic, and social contexts.
  • Extant Features of the Course:
    • The course is primarily a "read-up" course, requiring independent study.
    • Students are expected to consult external materials including online resources and textbooks.
    • Assessments (tests and exams) are not based on simple, direct questions but rather on the application of knowledge.
    • Students must master fundamental principles and be able to apply them to various scenarios.

Introduction to Energy and Classification

  • Definition of Energy:
    • Energy is the primary and most universal measure of work done by human beings and nature.
    • Every process in the world involves the flow of energy from one form to another.
    • Technically, energy conversion takes place between three different stages.
  • Classification Based on Usability:
    • Commercial Sources: These are capital-intensive energy sources such as petroleum products (diesel, petrol, kerosene oil) and electricity. Most are non-renewable.
    • Non-commercial Sources: These are available at comparatively low costs. Examples include human labor, bullocks (bulls), and cows. While every source has economic value, these are categorized by their relative cheapness.
  • Classification Based on Traditional Use:
    • Conventional: Energy sources used traditionally for many decades, including fossil fuels, nuclear energy, and large-scale hydro.
    • Non-conventional: Sources considered for large-scale use following the 1973 oil crisis, such as solar, wind, and biomass.
  • Classification Based on Long-term Availability:
    • Renewable Resources: Resources renewed by nature repeatedly; their supply is not affected by the rate of consumption.
    • Non-renewable/Exhaustible: Resources that are finite and do not replenish after consumption, such as fossil fuels, nuclear, and natural gas.
  • Classification Based on Origin:
    1. Fossil fuel
    2. Wind energy
    3. Solar energy
    4. Biomass energy
    5. Nuclear energy
    6. Geothermal energy
    7. Tidal energy
    8. Hydro energy

Renewable Energy Technologies and Applications

  • Core Characteristics:
    • Occur naturally and repeatedly in the environment.
    • Inexhaustible within the time horizon of humanity.
    • Can be harnessed for human benefit from sources like trees, plants, rivers, and garbage.
    • Driven by the increase in fossil fuel prices and environmental concerns regarding conventional fuels.
    • Defined as clean, inexhaustible, and capable of decentralized use.
  • Technology Applications by Source:
    • Solar: Photovoltaic (PV) cells for electricity; Solar thermal systems for heating water or air.
    • Wind: Wind turbines for water pumping, electricity production, or mechanical use.
    • Water: Hydro-electric, wave, and tidal systems for electricity generation.
    • Biomass: Direct combustion of gas produced from biomass or biogas for electricity/heat (e.g., wood stoves, commercial operations).
    • Geothermal: Utilizing the Earth's internal temperature for electricity or heat.
    • Ocean Energy: Operating heat engines to produce work and electricity via waves and tides.

Analysis of Renewable Energy: Pros and Cons

  • Advantages:
    • Inexhaustibility: No danger of depletion as sources reoccur in nature.
    • Low Running Costs: Plants based on these sources have no fuel costs.
    • Decentralization: Site-specific use allows for local processing, reducing the need for extensive transmission and distribution networks.
    • Ecological Balance: Low energy density typically correlates with minimal pollution.
    • Simplicity: Equipment is often simple in design and can be constructed using local skills and materials.
    • Rural Development: Ideally suited for serving remote villages with local resources.
  • Disadvantages:
    • Intermittency: Lack of dependability due to weather or cyclic patterns.
    • Low Energy Density: Leads to lower operating temperatures and lower efficiencies; necessitates larger plant sizes which increases capital cost.
    • Material Intensity: Construction materials for renewable devices are often energy-intensive themselves.
    • Thermal Pollution: Low efficiency can result in large heat rejections.
    • Land Use: Often requires significant land masses for installations.

Global Renewable Energy Statistics and Capacities

  • Regional Capacity and Energy (GWh):
    • Asia: Solar capacity 485,948 MW485,948\,MW; Wind energy 555,824 GWh555,824\,GWh; Hydropower capacity 594,267 MW594,267\,MW.
    • Africa: Solar capacity 11,393 MW11,393\,MW; Wind capacity 7,334 MW7,334\,MW; Hydropower energy 141,437 GWh141,437\,GWh.
    • Europe: Solar capacity 187,360 MW187,360\,MW; Wind energy 488,412 GWh488,412\,GWh; Hydropower capacity 224,393 MW224,393\,MW.
    • North America: Solar energy 137,703 GWh137,703\,GWh; Wind capacity 154,733 MW154,733\,MW; Hydropower energy 722,078 GWh722,078\,GWh.
    • South America: Bioenergy capacity 18,484 MW18,484\,MW; Hydropower energy 672,569 GWh672,569\,GWh.
    • Oceania: Solar capacity 23,242 MW23,242\,MW; Wind capacity 9,827 MW9,827\,MW.
    • World Totals: Solar (854,795 MW854,795\,MW), Wind (823,484 MW823,484\,MW), Bioenergy (143,195 MW143,195\,MW), Hydropower (1,360,502 MW1,360,502\,MW).
  • Top Contributing Countries (Capacity/Energy):
    • United States: Solar (95,209 MW95,209\,MW), Wind (132,738 MW132,738\,MW), Hydropower (101,894 MW101,894\,MW).
    • China: Solar (306,973 MW306,973\,MW), Wind (328,973 MW328,973\,MW), Hydropower (390,920 MW390,920\,MW).
    • India: Solar (49,684 MW49,684\,MW), Hydropower (51,565 MW51,565\,MW).
    • Germany: Solar (58,728 MW58,728\,MW), Wind (63,865 MW63,865\,MW).
    • Japan: Solar (74,191 MW74,191\,MW), Hydropower (50,019 MW50,019\,MW).

Electrical Energy Storage (EES)

  • Definition and Goals:
    • EES involves capturing and holding electrical energy for later use via technologies like batteries, pumped hydro, and flywheels.
    • Its primary goal is providing consistent power, especially for intermittent sources like solar and wind.
    • It facilitates meeting high-demand periods without increasing instantaneous production.
  • Market Status:
    • Global storage capacity is less than 2%2\% of total production capacity.
    • As of September 2017, global capacity was 176 GW176\,GW (USA held 24 GW24\,GW or 2.2%2.2\% of its production capacity).
  • Functional Applications:
    • Short-term/Power Quality: Smoothing output hour-to-hour or minute-to-minute to protect sensitive equipment (e.g., computers).
    • Long-term/Energy Arbitrage: Methods like peak-shaving and load-leveling where energy is stored during low demand (e.g., night-time wind) and released during high demand.

Storage Technology Options

  • Classification by Energy Type:
    • Potential Energy: Pumped hydro, compressed air, springs.
    • Kinetic Energy: Mechanical flywheels.
    • Thermal Energy: Passive (adobe), active (water), or phase-change (ice, molten salts).
    • Chemical/Electrochemical: Hydrogen, methane, gasoline, batteries, flow cells.
    • Electrostatic/Electromagnetic: Capacitors, superconducting magnets (SMES).
  • High-Scale Storage Technologies:
    • Pumped Hydro: Uses low-cost off-peak electricity to pump water to a higher reservoir. Most prominent in the US (22 GW22\,GW or >90%>90\% of storage). Capacity: 100−1,000 MW100 - 1,000\,MW with discharge times of 7−137 - 13 hours. Limited by geography.
    • Flow Batteries (e.g., VRFB): Liquid-based rechargeable systems. Capacity (40 kWh40\,kWh to hundreds of MWhMWh) is proportional to electrolyte tank volume. Offers high cycle stability and efficiency of 70−85%70 - 85\%.
    • Lithium-ion Batteries: Highest installed capacity worldwide (verified 950 MW950\,MW DOE projects). Moved between cathode and anode. Renowned for high energy density and lightweight profile.
    • Compressed Air Energy Storage (CAES): Uses electricity to inject high-pressure air (1500 psi1500\,psi) into underground geologic formations. Releasing the air powers turbines with less natural gas consumption. Suitable for load leveling at capacities of a few hundred MWMW.

Storage Economics and Performance

  • Capital Cost Ranges (per Lazard 2016):
    • Natural Gas Power Plant (Reference point): $1,000−$1,350/kW\$1,000 - \$1,350/kW.
    • Compressed Air: $116−$140/kWh\$116 - \$140/kWh.
    • Pumped Hydro: $152−$198/kWh\$152 - \$198/kWh.
    • Lithium-Ion Battery: $267−$561/kWh\$267 - \$561/kWh (experienced a 24%24\% cost decrease from 2015 to 2016).
    • Flow Battery (Vanadium): $314−$690/kWh\$314 - \$690/kWh.
    • Sodium Battery: $301−$784/kWh\$301 - \$784/kWh.
  • Performance Comparison (Ragone Plot):
    • Compares Specific Power (W/kgW/kg) against Specific Energy (Wh/kgWh/kg).
    • High Power: Supercapacitors and flywheels.
    • High Energy: Gasoline, Methanol, and H2 Fuel Cells.
    • Mid-range: Lithium-ion, Ni/Zn, and Lead-Acid batteries.

Energy Transmission and Grid Infrastructure

  • Types of Infrastructure:
    • Overhead Transmission Lines: High-voltage towers supporting lines for long-distance transport.
    • Underground Cables: Used in urban areas or environmentally sensitive sites to minimize visual impact.
  • Planning and Integration:
    • Scaling up renewables requires connecting new sources to the grid, often necessitating significant infrastructure upgrades.
    • Grid-enhancing technologies improve efficiency and stability.
  • Transmission Voltage Levels and Flow:
    • Generation: Power plants generate electricity.
    • Step-up Transformer: Increases voltage for long-distance transmission (765,500,345,230,138 kV765, 500, 345, 230, 138\,kV).
    • Subtransmission: Customer access at 138 kV138\,kV or 230 kV230\,kV.
    • Secondary Distribution: Steps down through neighborhood substations and pole transformers to 120 V120\,V or 240 V240\,V for residential use.

Energy Mix and the Energy Matrix

  • Definition: The combination of various energy sources (fossil fuels, nuclear, renewables) used to meet a region's total demand (electricity, transport, industry).
  • Factors Influencing the Mix:
    • Availability of indigenous resources.
    • Possibility of resource importation.
    • Level of energy demand (Economic growth, industrialization, urbanization).
    • Policies: Historical, social, demographic, economic, and geopolitical features.
  • Comparative Examples:
    • Nuclear: Brazil has 2 reactors; the USA has 98.
    • France: Renewables grew from <10%<10\% (2015) to nearly 12%12\% (2018).
    • Global Context: Fossil fuels currently represent over 80%80\% of the global mix. Rapid adjustment toward renewables (hydro, solar, wind, bio-energy, geothermal) is required to reduce CO2CO_2 emissions.

Socio-Economic Context of Energy

  • Relationship with GDP:
    • Energy consumption is closely linked to economic activity.
    • Notable positive correlations are observed in the history of Nigeria (1980−20111980 - 2011), Malaysia (1980−20091980 - 2009), China, and India.
  • Sectoral Demand Profiles:
    • Saudi Arabia (2007): Residential (50%50\%), Industrial (23%23\%), Governmental (16%16\%), Commercial (9%9\%), Agricultural (2%2\%).
    • Nigeria: Primary demand sectors include Residential, Industry, and Transport.
    • China (2015): Manufacturing is a dominant consumer in the energy demand structure.
  • Technological Growth Trends:
    • Renewable electricity capacity growth is being led globally by Solar PV and Wind technology.
    • In the U.S. (AEO2022 projections), solar is expected to account for 51%51\% of renewable generation by 2050.
    • China has shown significant progress in diversifying its primary supply with wind, solar, and biofuels entering the mix alongside traditional coal and oil.
  • Other Consideration Factors:
    • Energy Intensity: Consumption per unit of GDP.
    • Energy Efficiency: Reducing overall consumption and emissions through improved technology and practices.