In 2012 world population reached 7 billion; by 2050, 9.6 billion people will live on planet Earth according to UN estimates . As nations grow and develop, both energy consumption per capita and overall world energy consumption will increase dramatically.
So, where does all this energy come from? In the global energy mix, 82% comes from fossil fuels (coal, oil and natural gas) and 5% from nuclear . All these sources are non-renewable, which means that sooner or later these reserves will be depleted. For instance, BP estimates that world oil and gas reserves are to last 53 and 55 years respectively at current production rates . The World Coal Association has projected 109 more years of coal production . In turn, current uranium resources are to last 90 years with present technology as per the World Nuclear Association . On top of that, the Earth is experiencing global warming, the effects of which range from increased sea levels, higher occurrence of extreme weather events, loss of biodiversity and social consequences, such as diminished food production.
This makes indispensable to promote energy alternatives, based on renewable resources, as well as to develop more efficient ways to use energy. Solar, in combination with other renewables such as wind, hydropower and biomass, to name a few, are renewable and cleaner substitutes that are potentially capable of supplying today’s energy global demand.
The potential of solar energy
In the case of solar energy, it has been calculated that the total solar radiation received on Earth’s surface during the course of one year, adds up to 23000 TW-year, which is more than 1400 times the world’s annual primary energy consumption, or 95 times the energy potential of current oil’s reserves . In the picture below, the potential of several energy sources is represented with circles (in Terawatt, left side) together with the world's energy consumption (middle), and the estimated world's reserves of primary energy in form of fossil fuels and uranium (in Terawatt - year, right side).
The Photovoltaics market
In terms of market activity, the following are some key figures of the solar energy sector. According to a report from IEA-PVPS, by the end of 2014, the cumulative (overall) photovoltaic (PV) installed capacity reached 177 GW  worldwide (the equivalent to 177 nuclear reactors). Of those, 40 GW (22%) were installed only in 2014 , which illustrates the momentum that this market is experiencing.
Asia leads the PV global market with around 60 % of the total capacity installed, with China, Japan, Korea, India, Thailand and Taiwan as the most dynamic Asian countries in 2014. In Europe, UK lead the market during the same year, but Germany broke the record of reaching 50% of its electricity needs on the 9th June 2014 . Other countries around the globe have also installed considerable PV capacities during last year: for instance Chile did so with 400 MW, Israel installed 250 MW and Canada did its part with another 500 MW. Several African countries are embarking in a number of PV projects of considerable size, including South Africa, Ghana, Senegal, Ivory Coast, Mali or Kenya . PV off-grid systems have also been a very common solution to rural electrification in Africa, Asia and Latin America.
|Annual PV installed (2014)||Cumulative PV installed (2014)||Theoretical PV contribution to electricity demand (2014)|
|China||10,6 GW||Germany||38,2 GW||Italy||7,9 %|
|Japan||9,7 GW||China||28,1 GW||Greece||7,6 %|
|USA||6,2 GW||Japan||23,3 GW||Germany||7,1 %|
|UK||2,3 GW||Italy||18,5 GW||Bulgaria||3,9 %|
|Germany||1,9 GW||USA||18,3 GW||Czech Republic||3,8 %|
|France||0,9 GW||France||5,7 GW||Belgium||3,6 %|
|Australia||0,9 GW||Spain||5,4 GW||Spain||3,5 %|
|Korea||0,9 GW||UK||5,1 GW||Romania||2,7 %|
|South Africa||0,8 GW||Australia||4,1 GW||Japan||2,5 %|
|India||0,6 GW||Belgium||3,1 GW||Australia||2,3 %|
Elaborated with data from IEA, 2015.
The Solar Thermal market
The market of solar thermal is also very dynamic worldwide. According to the IEA , by the end of 2013 the total installed capacity was 375 GWth (535 million m2). The table below illustrates the shares distributed among continents and countries.
Division of the world's solar thermal market cumulative installed capacity (values are in GWth).
Of those 375 GWth, 55 GWth alone (15%) were installed in 2013 (78,6 million m2). It is calculated that, in 2013, the energy savings of all water-based solar thermal systems accounted for 33.7 million tons of oil, contributing to an equivalent of 109 million tons of CO2 mitigation.
Concentrating Solar Power
In regards Concentrating Solar Power (CSP), it is worth mentioning that several power stations have gone online in recent years, with a constant increase in size and power output. Spain, a pioneer country in this field, has more than 30 CSP plants already built or under development. In turn, the USA has showed clear interest in this technology and already built several of the biggest CSP stations worldwide, being Ivanpah, in California, the most powerful so far with 392 MW (solar tower). South Africa, United Arab Emirates and India have also built CSP plants, using parabolic trough technology. Algeria, Egypt, Morocco and Iran are currently using ISCC plants (Integrated Solar Combined Cycle).
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