Let's start with two basic claims.
Claim 1. If CO2 emissions due to fossil fuel consumption by the human society can be basically stopped within a few decades, say, before 2030, the global warming trend may be stopped before it reaches an irreversible point.
Claim 2. If a renewable energy source is found to be substantially cheaper than fossil fuels, stopping fossil fuel consumption within a few decades is realistic.
It appears that nobody has seriously studied the senario of Claim 1, because nobody was expecting Claim 2. But according to existing studies, Claim 1 should be pretty safe to assume. For example, see this.
Claim 2 needs much more explanation.
The energy consumption is roughly divided, almost in equal parts, into 3 sectors: transportation, industrial, residential/commercial.
The latter 2 categories are for fixed consumption of energy. The total accounts for 70% of the energy consumption, for which local solar energy production can now satisfy a big part of the need with competitive cost. For an average of industrialised countries, this part represents 40000kWh/year per capita, or 40m2 of collectors, of which 25m2 are preferably in local residential areas, the rest being industrial.
For the availability of local spaces, note that besides residential rooftops, solar collector arrays can be installed above parking lots, roofs of public buildings (shopping centers, factories, schools, stadiums), or portions of roads. Esthetically, while installing solar collectors on the roof of an architectural masterpiece will rather disfigure it, there is no reason to think that solar collectors are less esthetic than a bare parking lot or a flat roof.
In a city of a developed country, each inhabitant enjoys at least 30m2 of parking space, corresponding to one parking place plus its access roads. If 50% of this is covered by suspended solar collectors, with a space usage rate of 50%, we will have 7.5m2 of collector surface per capita, or about 30% of the need. Adding rooftops and other available spaces, there will be enough space to install solar collectors for local solar energy supply.
Due to the huge economic advantage, promoting this solar energy solution should not be very difficult.
It is however not economically interesting to install too much thermal storage capacity for a 100% coverage of the local energy need. Hence we can only expect a general local supply rate of 60%.
Solar grid electricity could supply 20% of the remaining residential/commercial use, as well as 70% of the industrial need of electricity.
Part of the transportation energy can also be supplied by residential or local solar power, with hybrid cars to be recharged at home during the night.
Therefore we can expect the following table in the long run.
This adds up to about 60% of the total energy consumption. The remaining
part can be supplied by renewable fuel.
Type Weight Direct solar rate
Residential/commercial 40% 80%
Industrial 30% 70%
Transportation 30% 25%
This adds up to about 60% of the total energy consumption. The remaining part can be supplied by renewable fuel.
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