500 Factor

The 1000 factor is a factor calculated theoretically as the limit of possible increase of energy by humans, without suffering from ecocide.

This number is a number that allows for solar energy to power all natural processes such as weather phenomena, natural life, along with human-made processes such as the conversion of solar energy into useful power for industrial processes, indoor heating/cooling, transportation, etc.

Plants are the largest users of solar energy. Plants use only 1-2% of the incoming solar spectrum [1], and the earth's coverage with plants is about 30% [2]. Since only plants can use solar energy, and animals build ecosystems upon plant energy - the plant energy is the primary energy important to overall solar energy usage. Ie, animals do not use solar energy, outside of the heat - a component of weather. Bottom line - the amount of total energy required to sustain the ecosphere is under 1% of the total incoming radiation.

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Source: [3]]

Every 100k years, we go through ice age and hot age - where mean temperature of the earth fluctuates up to 7C [4] and ice coverage of earth increases to 25% of land mass (8% of total).

Here is the history of temperature over 500 million years - showing that global averages of temp ran anywhere from 50 to 95 F [5] - that is - fluctuating over 25C over all time.

Energy Budget of the Earth

From NASA - [6]

17% of surface energy radiates back, not part of weather (rain and wind).

Don't mess with evaporation - or you will have drought.

Thus, 17% is available for PV. This means that we could cover probably cover up to 17% of the earth with PV without changing weather.