The Sun is the main source of energy, heat and light in the solar system, which means that our star has the highest potential to produce carbon-free energy that can power the entire planet.
The Sun is also behind several sources of renewable energy used on the planet to generate clean electricity such as solar, wind, wave, biomass and tidal power.
The sunlight is used to generate clean electricity using solar cells installed on solar panels, the Sun is also the source of the wind power (the Sun heats the different layers of the atmosphere in an uneven way, which makes the air move and generate the wind on our planet).
Waves are produced by wind, and biomass stores solar energy during the lifetime of plants and trees, which is then turned into heat and electricity in power plants.
The tides on planet Earth are produced by the combined gravitational forces of the Sun, Moon and our planet, which means that in some degree, the Sun is also the source of the tidal power.
What is the Potential for Solar Energy on Planet Earth? (theoretical)
The Sun is sending a tremendous amount of energy towards our planet every hour, but a large part of this energy is lost in the space (about 30%) or is absorbed by the atmosphere and clouds (about 19%).
However, the Earth’s surface receives a solar flux of 174.7 W/m2, which means that the theoretical potential of solar power on the planet is 89,300 TW (terrawatt) that equals 89,300,000,000 MW (megawatt).
The theoretical potential of solar energy shows that the Sun is sending towards the Earth (in only 1 hour), more energy than we consume today using all the power sources (fossil fuels and renewables combined).
However, the sunlight does not strike the surface of the Earth the same way in all the areas of the planet and this is happening due to the inclination of Earth’s axis.
This way the hot area between the Tropics of Cancer and Capricorn receives about 225 W/m2, while the surface of the planet located in the “temperate zone” between the Tropic of Capricorn and the Arctic Circle and between the Tropic of Cancer and the Antarctic Circle receives 150 W/m2.
Other areas of the planet receive even less sunlight, so they are not very suited for solar power production.
The solar flux of 174.7 W/m2 received by the Earth’s surface from the Sun is only an average of the combined values of all the areas of the planet.
How Much Power Can We Extract From Sunlight Using the Current Technology?
Today, the sunlight is turned into clean electricity using three different technologies.
For solar electricity, which is a carbon-free energy source, we are using solar cells installed on solar panels that are transforming the sunlight into clean electricity.
The thermodynamic limit to the efficiency of the conversion to electricity is roughly 87% of the solar energy potential, which means that we can convert about 58,300 TW into clean electricity using the solar cell technology (this value is not related to the limitations of the technology used).
For solar fuels, we need to convert the sunlight into chemical energy that is then used to produce solar fuels.
Solar energy is not a constant source of power, which means that by creating solar fuels we can use the power of the Sun every time we need, not only when the Sun is shining.
The thermodynamic limit to the efficiency of conversion to solar fuel (chemical fuel) is around 68%.
Using the theoretical potential of 89,300 TW, the extractable potential in “equivalent solar fuel” is around 60,700 TW.
The sunlight can be turned into clean electricity using the solar thermal technology.
Hundreds or thousands of large mirrors are concentrating the sunlight into a central point mounted on the top of a tall tower where molten salt or another agent is heated to produce steam that will spin a turbine to generate clean electricity.
The solar thermal technology uses the sunlight as heating source for an agent that produces steam to rotate a turbine and the mechanical energy of the turbine is transformed into clean electricity using a generator.
The thermodynamic limit to the efficiency of conversion to mechanical power is about 87%.
The “equivalent solar fuel” power for solar thermal heat would be around 19,400 TW.
What is the Current Capacity for Solar Power Generation?
At the end of 2018, solar power represented 510 GW in terms of generation capacity, which is a share of 2.58% from the total electricity consumption on the planet.
Wind power accounted for 550 GW, which represents 24% of the global capacity.
Hydro accounted for the highest share (1,152 GW), which represents more than half (53%) of the global capacity for renewable energy generation.
Other renewables such as biomass energy (109 GW), geothermal energy (13 GW) and 500 MW in marine energy (wave, tidal and ocean energy) represent only 6% of the global capacity for renewable energy generation (source).
At the end of 2017, renewable energy accounted for 2,179 GW in terms of generation capacity, which represents only 10% share (renewables and hydroelectric) in the global energy mix.
However, fossil fuels such as coal and oil are losing ground in front of the expand of natural gas and renewables.
How Much Solar Potential Is Used Today?
One of the major issues with solar is represented by the fact that this clean energy source is not a constant source of power, which means that we need to store the energy produced for later use.
The technology used today for energy storage (especially from intermittent sources of power, such as solar and wind) is pretty old and not very efficient.
Actually, we can store only a limited amount of power because the battery technology used today is limited and very expensive.
The fact that solar and wind power are intermittent sources of energy is also the reason why solar and wind power are usually combined with fossil sources of energy such as natural gas to provide a continuous and steady supply of energy in the grid.
Solar technology also needs to improve its efficiency because a large part of the solar energy sent by the Sun towards the Earth is lost due to the fact that solar cells cannot turn into clean power more than 21% of the sunlight.
However, the technology used today to store solar power evolves along with the technology used to harvest solar and also due to the fact that we need to reduce the use of dirty fossil fuels and increase the use of free-carbon energy sources such as solar and other renewables for a cleaner environment.
Solar power also needs to become more affordable because the high prices of the technology used to harvest solar today (even if there are incentives available) is still a major barrier in front of the massive development of the solar energy generation capacity.
The Future of Solar Power in the U.S.
For the moment, solar power represents a very tiny share in the global energy mix, but the today’s research in the field (research from MIT), wants to create very small organic photovoltaic solar cells (microscopic solar cells) that can be used to power our gadgets (something like a battery that is always full of energy and never needs to be recharged).
The nanostructure of organic photovoltaic solar cells is transparent and can be used on all the windows available on buildings.
There are millions of square meters of glass on all the buildings on the planet, and by placing the nanostructure of organic photovoltaic solar cells on all the windows of a building, we can produce enough solar power to power the entire building.
However, for a massive development of the solar power generation capacity we need to fundamentally change the energy storage technology and also the power grid.
