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Renewable energy and trapping solar energy

Short answer

Renewable sources (solar, hydro, wind, biomass) are naturally replenished; non-renewable (coal, oil, gas, uranium) are finite. World energy ~80% fossil fuels. Solar trapping in buildings: east-west orientation with south glazing, direct gain with thermal mass, Trombe walls, sunspaces, roof collectors, PV panels, insulation, and overhangs for summer shading.

Describe briefly about renewable and non-renewable sources of energy highlighting the world scenario. Explain the different ideas to trap the solar energy in building with the concept of energy efficient design.

Renewable and non-renewable sources

Renewable energy comes from sources that are naturally replaced in a short time: solar, hydro, wind, biomass and biogas, geothermal, tidal. Non-renewable energy comes from fixed stocks formed over millions of years: coal, oil, natural gas and uranium.

World scenario: About 80 % of world energy is still from fossil fuels (oil about 30 %, coal about 27 %, natural gas about 23 %). Renewables, including hydro, supply roughly 15 to 20 % of primary energy and about 30 % of electricity, and are growing fastest in solar PV and wind. Fossil fuels are limited and cause climate change, so countries move to renewables. Nepal gets most of its electricity from hydropower, and most household energy from firewood, with petroleum fully imported.

Trapping solar energy in buildings (energy efficient design)

  1. Orientation and layout: Long axis east-west and living spaces facing south.
  2. Direct gain: Large south windows; the sun heats floors and walls of high thermal mass (concrete, stone, adobe).
  3. Trombe wall: Dark masonry wall behind a glass pane with vents; absorbs heat and sends it by convection and radiation.
  4. Sunspace (attached greenhouse): Glazed space on the south side which collects heat and shares it with the rooms.
  5. Roof collectors / solar air heaters and water heaters for hot water.
  6. Roof pond or water wall to store heat.
  7. Photovoltaic panels for electricity.
  8. Insulation and weather sealing to keep the gained heat, and overhangs to avoid summer overheating.
 winter sun ->|glass| air gap |dark mass wall| room
                   vents top & bottom: warm air loop

✓ Answer checked by Claude Opus 5.5 (high effort)

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