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Solar photovoltaic revolution - PV's take centre stage in worlds energy economy


The world is bathed in energy beamed directly from our sun. The energy content of solar radiation is sufficient to supply all the planet's power requirements multiple times over. Unlike coal and other fossil fuels, the sun's energy will never run out. It is also entirely non-polluting, and doesn't result in carbon dioxide emissions.

But converting all that bountiful energy into usable power is a challenge, though one for which increasingly efficient solutions are being developed. The first generation of photovoltaic cells used silicon crystals to convert sunlight into electricity. When a photon of light is absorbed it excites an electron in the silicon crystal to a higher energy level where it can move around the crystal more freely, generating an electric current that we can collect.

A problem with silicon crystals is that it was difficult and expensive to scale. Much cheaper materials including polysilicon are now used, and since 2008 the price of photovoltaics has been falling rapidly. A photovoltaic now costs less than 20% of what it cost in 2008, with the world's leading manufacturer of solar panels being China.

The end of coal?

Coal has powered the world since the days of the industrial revolution. But, although it has driven economic growth, it has left behind a terrible legacy, in particular pollution and the carbon dioxide emissions that are driving climate change. The list of countries that have announced their intention to phase out coal power is growing. In the UK the government has announced that coal will be phased out by 2025. Even in China the demand for coal has fallen, with some analysts claiming it has already peaked and will continue to decline. Economics no longer favour coal; in fact renewables such as solar and wind are now competitive to coal in many parts of the world. Even so, the market for coal is unlikely to die. New technologies such as carbon sequestration and more efficient energy conversion will keep it alive, though it will lose its dominant position.

The dawn of the photovoltaic energy era

There are several potential replacements for coal. Fracking, nuclear energy, wind and solar energy are all vying for position, though of these it is solar energy that is really taking centre stage. Across the world the markets for solar generated electricity are growing apace. Prior to 2015 the photovoltaic industry was at best embryonic, but since then there has been a real movement forward. During 2015 it grew by 25% spurred on by a steep decrease in the price of solar panels. In fact the cumulative capacity of photovoltaics in terms of megawatts has grown exponentially: in 2008 it was 11,000 megawatts; today in 2017 it is close to 400,000 megawatts. The key driver of low cost photovoltaics is their efficiency, in other words the proportion of incident sunlight they convert to energy. Currently, efficiencies are around 20% though the theoretical maximum efficiency (the Shockley–Queisser limit) is around 34%; thus it is likely that future technology developments will result in new highly efficient solar cells that will further advance the photovoltaic economy.

The future of energy production

The PV era will mean cheaper cleaner energy that will be used in many areas both domestic and commercial. Solar power will heat our homes, power our factories, power our electric cars, and will be utilised in the generation of synthetic fuels. The economics is compelling: in the early days of photovoltaics the cost of electricity generated by solar panel was around £15 a watt; today it is around £1.50 a watt and falling.

According to the International Energy Agency (IEA), by 2050 solar energy systems could be generating 27% of all the world's electricity needs. Around 16% of this will be from photovoltaics and 11% from complimentary solar energy plants using related technologies.

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