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The solar revolution is only starting…

This article first appeared in the Energy and Carbon blog

In theory, solar power has always been the perfect solution to our energy needs. Not only do our lifes and the lifes of nearly all living organisms on our planet depend on the light from the sun for energy needs, but our fossil fuels all came about because of the sun. And the renewable energy advocates are right with their mantra that “If we cover a small part of the Sahara Desert with solar panels, we can power the world”. If the sun’s energy was effectively harnessed, which it can be with modern solar technologies, all of our global energy needs could be met with solar installations. This begs the question, why aren’t we doing it then. We are not using solar for our energy needs because it is still very cheap to take fossil fuels from the ground and in addition we have a huge global infrastructure which has been built up over the last 100 years to excavate, transport and harness those fuels. However this is changing as electricity becomes the most important energy source powering our homes, businesses and entire economic systems and as solar costs plummet.

There are two ways to capture the sun’s energy to produce electricity: Concentrated Solar Power (CSP) and Solar Photovoltaic (PV). As the name suggests, CSP plants produce electricity by concentrating the sun’s rays, usually to boil water. Yet, despite the fact that CSP off the shelf components have been around for many years now, the technology has never really gained much traction. Part of the reason is that it has not been able to push its costs down particularly in comparison to solar PV. Plus, clear skies for direct sunlight are needed (ruling out most of Europe and a lot of Asia for deployment), and the systems need to be large in scale making them unsuitable for rooftops or decentralised installations.

Photovoltaic systems don’t need direct sunlight and are able to convert the sun’s energy directly into electricity. This is thanks to the Photoelectric Effect for which Albert Einstein won the Nobel Prize for Physics in 1921. The Photoelectric Effect is basically the phenomenon that when light strikes certain conducting materials, electrons absorb enough energy to escape the binding atoms. When two complementary photosensitive semiconductor materials are used together, the liberated electrons can be induced to flow from one material to the other and create an electric current. This is the basis of how a solar cell works.

The first practical photovoltaic solar cells were the product of Bell Laboratories in the U.S. in 1954 and were able to convert 6% of the sunlight hitting them into electricity. Four years later when the U.S. satellite Vanguard 1 was launched, it was powered by six solar cells. Now, over 50 years later, modern satellites are still powered by photovoltaic cells, some of which have a lifespan of over 40 years. And the commonly used material for making solar cells is still silicon; the material first used all those years back in Bell Laboratories. And just like the costs of semiconductors (which also use silicon) have tumbled, so have solar panel prices.

In 2004, a typical 200 watt solar module sold for about $1,300. That same module now sells for around $130 today! And there are further cost reductions to come as technology improvements push conversion efficiencies above the 18% level found in today’s standard solar modules towards the rates of a modern satellite (40%). And the good news is that the core material used for manufacturing solar panels, silicon is cheap to produce and there are lots of it due to the abundance of sand it is produced from.

One of the major advantages of photovoltaic solar is that it can be used in both small and large-scale installations. PV can be used to power calculators, they can be mounted onto our roofs or façades, or they can be configured in large-scale plants. Plus, installation is simple and quick. Whereas a nuclear power station with a GW of power capacity could take ten years from inception to commission and generate its first megawatts of power, solar can be deployed at breathtaking speeds. China, for instance, installed just under 11GW of new solar capacity in 2014. And nearly all of these systems required less than six months to plan, construct, and connect to the grid to start delivering power to the public. Solar’s steep cost curve has fueled its viral expansion. In 2000, the global market for solar was a mere 277 MW. In 2014 the market was over 40 GW, and it could well be that this year solar will overtake both coal and gas to become the number one power generation technology.

That’s not all. Solar has become so cheap that the technology can already compete without subsidies in large parts of the word. In fact, in countries, such as Chile, solar is already the least expensive form of power production. Even in California, solar power is being sold at similar levels to electricity from gas-fired plants. Its flexibility has also made solar ideal for off-grid solutions, such as powering remote telecommunications towers. And in many developing countries solar is already the cheapest way to bring power to rural communities and homes. Even in Europe and the North America not to mention Japan or Australia the cost of generating power from solar on the household roof (without any form of subsidy) is oftentimes cheaper than buying power from the utility.

Of course there is still the issue of what to do when there is no sun: either at night-time or during the day when heavy cloud cover impairs solar generation. Such intermittency issues can be overcome by doing a better job of matching demand to supply and by using a power grid to move the solar from where it is produced to where it is needed. One other possibility is to use fossil fuel power stations such as gas peakers, which have been used for decades to supply rapid and flexible power if and when it is needed. But the most logical and attractive solution to the intermittency problem would be to store the electricity. We are already seeing this happening in countries like Tanzania where a combination of solar and batteries is already the cheapest and most effective way to bring power to the people. And as storage costs and battery costs come down the mix will have huge ramifications not just for those of use who don’t have power but for the whole global energy industry. And the solar market will keep growing despite low oil prices.

This article first appeared in the Energy and Carbon blog