The much-debated study The Limits to Growth, which was published as early as 1972 by Dennis L. Meadows et. al. on behalf of the “Club of Rome”, already predicted shortages of natural resources and especially fossil fuels (coal, oil and gas) alongside irreparable damage to the environment if nothing was done about the world population growth, industrialization, pollution, food industry and exploitation of resources of that time. Oil crises and price increases of the past have shown how nearly every state is dependent on oil. Even the seemingly eco-friendly nuclear power uses limited resources and poses severe and still unsolved problems concerning the permanent disposal of its waste.

With all these insights, the focus is on other eco-friendly and safe approaches to power generation independent of limited resources, yet sufficient in quantity. One concept is the use of renewable energies in connection with storage of excess energy. Before fossil fuels were discovered, mankind relied solely on renewable energy, and fossil fuels really only gained their importance during the course of the industrialization.

Renewable energies include:

  • Wind power
    • wind turbines
  • Hydropower
    • hydroelectric dam with turbine
    • run-of the-river hydroelectricity
    • Pumped-storage hydroelectricity
    • Tide power
  • Solar energy
    • Photovoltaics
    • Solar thermal energy
  • Biomass
    • Thermal conversion
    • Chemical conversion
    • Biochemical conversion
  • Biofuel
    • Bioethanol
    • Biodiesel
    • Biogas
  • Geothermal energy
    • Geothermal heating
    • Geothermal heat pump

One way of storing excess energy is by using electricity to generate hydrogen through electrolysis of water, which can then later be oxidized to generate electric energy from the chemical energy stored in the hydrogen.

Relevant scientific concepts:

Energy Definition The ability of a physical system to do work or transmit light or heat.
Formula E
Units one joule (1J), one watt-second (1Ws), 1J = 1Ws
Measuring instrument ---
Force Definition

Any influence that causes an object to undergo a certain change.

Formula F = ma (mechanic) or F=qE (electric)
Units one Newton (1N)
Measuring instrument spring scale
Work Definition A physical system does work, when there is movement under the action of a force.
Formula W = Fs (mechanic) or W = qU (electric) or W = ΔE
Units one newton-meter (1Nm), one joule (1J), 1Nm = 1J
Measuring instrument ---
Power Definition The rate at which energy is transferred, used or transformed.
Formula P = ΔE/t = W/t (mechanic) or P = UI (electric)
Units one watt (1W), one joule-second (1Js), 1W = 1Js
Measuring instrument ---
Electric Current Definition A flow of electric charge through a conductive medium.
Formula I = q/t or use Ohms law
Units one ampere (1A)
Measuring instrument ammeter
Voltage Definition The „force or push“ that moves electric current through a circuit.
Formula U = W/q or use Ohms law
Units one volt (1V)
Measuring instrument voltmeter, potentiometer
Electrical Resistance Definition The opposition to the passage of an electric current through an electric element.
Formula R = U/I or R = ρℓ/A
Units one ohm (1Ω)
Measuring instrument ohmmeter
Temperature Definition A measurement of how hot or cold a body is.
Formula T or ϑ
Units one kelvin (1K) or one degree celsius (1°C)
Measuring instrument thermometer
Heat Definition The amount of energy that is transferred from one system to another by thermal interaction.
Formula Q = ΔE or Q = cmΔT
Units one joule (1J)
Measuring instrument ---
Irradiance (Light intensity) Definition The power of light per unit area incident on a surface.
Formula I = P/A
Units one watt per square meter (1W/m²)
Measuring instrument light sensor

Relevant scientific concepts and phenomena

  • Energy conversion
  • Heat transfer
  • Electric generator
  • Direct and alternating current
  • Electric circuit
  • Ohms law
  • Kirchhoffs laws
  • Inner photoelectric effect
  • Electrolysis
  • Fuel cell
  • Fermantation
  • Ecosystem
    • interaction between animate and inanimate nature
  • Water cycle (hydrological cycle)