Know that radiation from the Sun is the main source of energy for all our energy resources except geothermal, nuclear and tidal

1.7.3 Energy Resources

Learning Objective

State that radiation from the Sun is the main source of energy for all our energy resources except geothermal, nuclear and tidal.

Why the Sun is the Primary Energy Source

  • The Sun delivers a continuous flux of electromagnetic radiation to Earth.


    Solar constant (top of atmosphere): \(S = 1361\ \text{W m}^{-2}\)

  • Only about 70 % of this radiation reaches the surface, yet it supplies more than 10 000 TW of power – enough to drive the vast majority of the world’s energy resources.

  • All renewable resources (solar, wind, hydro, biomass, fossil fuels) ultimately trace their energy back to this solar input.

Energy Resources Derived Directly or Indirectly from Solar Radiation

ResourcePrimary Energy SourceTypical UseAdvantages (renewability, emissions, etc.)Disadvantages (availability, efficiency, environmental impact)
Solar photovoltaic (PV)Solar radiation – directElectricity generation (rooftop, utility‑scale)Zero‑emission operation; abundant; modularIntermittent (day/night, clouds); conversion efficiency 15–22 %
Solar‑thermal (collectors, CSP)Solar radiation – directDomestic hot water, space heating, steam‑turbine powerLow‑emission; can incorporate thermal storageEfficiency 40–70 % (depends on temperature); performance falls in hot ambient conditions; needs storage for night use
Wind powerSolar‑driven atmospheric temperature gradients (indirect)Electricity generation (on‑shore & off‑shore turbines)Renewable; no fuel cost; relatively high capacity factor in windy sitesVariable wind speed; site‑specific; visual & noise concerns; efficiency of rotor ~30–45 %
Hydroelectric powerSolar‑driven water cycle (evaporation → precipitation) (indirect)Electricity generation (large dams, run‑of‑river)Renewable; can provide base‑load and storage (pumped‑storage)Depends on rainfall & river flow; ecological impacts on rivers; efficiency 80–90 % for turbines
Biomass / bio‑fuelsSolar radiation via photosynthesis (indirect)Heat, electricity, transport fuels (e.g., biodiesel, ethanol)Carbon‑neutral if sustainably managed; can use waste streamsLand‑use competition with food; seasonal availability; conversion efficiency 20–35 %
Fossil fuels (coal, oil, natural gas)Ancient solar‑derived biomass (indirect)Heat, electricity, transport (most of today’s energy mix)High energy density; existing infrastructureFinite reserves; high CO₂ & other pollutant emissions; efficiency of combustion plants 30–45 %

Energy Resources Not Primarily Powered by Solar Radiation

ResourcePrimary Energy SourceTypical UseAdvantagesDisadvantages
GeothermalEarth’s internal heat (radioactive decay of U, Th, K)Electricity generation (high‑temperature plants) and direct heatingLow emissions; reliable base‑load; long‑term resourceGeographically limited; high upfront drilling cost; gradient ≈ 30 °C km⁻¹
Nuclear (fission)Binding energy of atomic nucleiLarge‑scale electricity generationVery low CO₂ during operation; high energy densityRadioactive waste; high capital cost; public acceptance & safety concerns
TidalGravitational pull of the Moon (and Sun) – dominant driver is the Moon (≈ 54 % of tidal force)Electricity generation at high‑tidal‑range sitesPredictable, renewable output; long‑life turbinesLimited to suitable coastlines; ecological impact on marine habitats; relatively high capital cost

Key Points to Remember

  • Radiation from the Sun is the main source of energy for every listed resource except geothermal, nuclear and tidal.

  • Even resources that appear unrelated to sunlight (wind, hydro, biomass, fossil fuels) are powered by the Sun’s heating of the Earth’s surface, which creates temperature gradients, the water cycle, and photosynthesis.

  • When comparing resources, always consider:

    • Renewability (solar, wind, hydro, biomass → renewable; fossil fuels → non‑renewable; geothermal & nuclear → practically non‑renewable on human timescales)

    • Availability & reliability (intermittent vs base‑load)

    • Environmental impact (CO₂, land use, waste, ecosystem disturbance)

    • Efficiency of energy conversion (from solar input to final useful form)

  • Geothermal, nuclear and tidal are the three exceptions that do not depend primarily on solar radiation.

Suggested Diagram – Solar Influence Flow‑Chart

Sun

Earth

Solar radiation

Solar PV / Solar‑thermal

Wind (temperature gradients)

Water cycle → Hydro, Biomass, Fossil fuels

The flow‑chart shows how solar radiation drives all the listed energy resources. Geothermal, nuclear and tidal are omitted because they do not depend on the Sun.