The sun could be meeting a quarter of the world's electricity needs by 2050, the International Energy Agency says.
Overnight it published two solar technology roadmaps: one for solar thermal electricity where heat from the sun is used to heat liquid and drive a turbine; and another for the more familiar solar photovoltaic cells.
The IEA says that by 2050, solar PV could be providing 16 per cent of the world's electricity. Solar thermal could account for another 11 per cent, it thinks.
The march of solar PV
Solar panels have been spreading across rooftops around the world like a rash. Installed solar PV capacity has increased by half again each year for the past decade, as the chart below shows.
Much of that growth has been in Europe, particularly in Germany, Italy and Spain where generous subsidies had driven deployment.
Those subsidies have been cut, leading to reduced installation rates. But other countries have started to pick up the slack.
Worldwide solar PV capacity reached 135 gigawatts in 2013, the IEA says, up by 37 GW on the previous year. Last year was also the first since 2004 in which more capacity was added in Asia than in Europe. China, with 11 GW, installed more solar PV in 2013 than all of Europe put together.
In total the IEA sees the current 135 GW of solar PV capacity growing to 1721 GW in 2030 and a massive 4674 GW in 2050. That would be able to generate around 16 per cent of global electricity needs.
To get a sense of how much solar that actually is, total installed global capacity for all forms of generation was 5331 GW in 2011.
Recent regional trends are expected to continue, the IEA says, with China adding the most new solar PV capacity out to 2050 (lilac area, below).
The cost of solar modules in 2013 had fallen by 80 per cent over five years, the IEA points out, though costs have since stabilised. Even so, system costs have continued to decline as industry experience grows.
Solar PV systems can already produce power at costs similar to gas or even coal in the right locations, the IEA says, though the cost of financing investment in solar may be higher than for traditional energy sources.
Grid parity, where solar power costs as much to produce as average electricity, was reached in 2013 in Germany, Italy, California and Australia, it says. The IEA notes that increased rates of solar deployment bring other issues, such as the need to strengthen power grids, and these problems may carry additional costs.
It acknowledges these challenges and says options including electricity interconnectors, energy storage and efforts to manage electricity demand will all be needed.
It's also important to note that as with all predictions of the future, the IEA scenarios depend heavily on how the relative costs of power generation evolve and the way in which any barriers that arise are overcome.
All the same it's encouraging to note that at least in some parts of the world solar PV is getting to the point of being cost-competitive.
The slower rise of solar thermal
The story of rapid solar deployment is continued for solar thermal plants. Their capacity grew from 600 megawatts in 2009 to 3.6 GW in 2013 worldwide (chart, below). That's not much compared to solar PV for now, but capacity has been growing fast – at 30 to 60 per cent per year since 2009.
Currently worldwide capacity for solar thermal is about the same as the planned nuclear plant at Hinkley Point in the UK's Somerset. However solar plants don't produce power round the clock and through the seasons in quite the same way as nuclear.
One big advantage of solar thermal plants is that they are able to store heated liquid to smooth out power production once the sun sets. In effect they can have in-built energy storage capability. Solar PV plants can't manage this trick.
You'll notice from the chart above that so far almost all solar thermal capacity has been installed in the US (orange area) and Spain (blue). These countries have one thing in common – lots of sun and plentiful empty space.
You can see how important sunshine is in the IEA's expectation for the growth of solar thermal out to 2050. Almost all the growth in output is expected to come from parts of the world that are close to the equator, as the chart below shows.
If the IEA scenario turns into reality, solar thermal capacity around the world would increase from today's 4 GW to 261 GW in 2030 and 982 GW in 2050.
Almost all of this would be in the US, China, India, Africa and the Middle East. The EU would have just 28 GW, compared to 118 in China and 229 in the US.
This new roadmap is less optimistic than the projections the IEA made in 2009-10, however. It had expected 147 GW of capacity by 2020. It now says an extra seven to 10 years will be needed to pass that milestone.
What is means for the climate
The IEA's solar technology roadmaps emphasise an argument it has made several times before: that tackling climate change need not cost the earth.
The IEA says that decarbonising the energy system by 2050 would produce net savings of $US71 trillion. The marginal cost of renewing energy infrastructure with low-carbon supplies instead of carbon-intensive sources would be $US44 trillion, it thinks. But this would be more than offset by savings in avoided fossil fuels of $US115 trillion.
The IEA specifically addresses concerns that the emissions produced during manufacture of solar panels and the variable nature of the electricity they produce reduces the emissions savings expected.
"Modelling by the IEA and others shows that the penalties incurred due to the manufacturing process and the variability of PV are minor compared with the emission reductions arising from fossil fuel displacement."
These kind of forward looking exercises have to be interpreted carefully, as projecting 35 years into the future is a challenging task.
But if the IEA's 2050 vision for solar is achieved, then 6 gigatonnes of carbon dioxide emissions would be avoided each year – 4 gigatonnes from solar PV and the rest from solar thermal.
That would be a significant chunk of the effort needed to cut current annual emissions from close to 40 gigatonnes to perhaps 50 per cent lower by 2050. If the world is to avoid dangerous climate change, this is probably part of what success looks like.
Originally published by Carbon Brief. Reproduced with permission.