10 August 2019 | New Scientist | 35solar energy that struck it into usable electricity.
By 1959, a rival firm had achieved 10 per cent. A
quarter of a century later, in 1985, an Australian
team reached 20 per cent efficiency. And in
2016, a group at the University of New South
Wales achieved almost 35 per cent, the current
world record. Most commercially available
solar cells peak at about 20 per cent efficiency.Power up
But silicon, although widely available, is hard
to work with. “Silicon cells are made by taking
sand, heating it up to thousands of degrees,
and reducing it from silicon oxide to pure
silicon,” says Lance Wheeler, a materials
scientist at the National Renewable Energy
Laboratory (NREL) in Colorado. “It’s energy-
intensive and a very sensitive process – you have
to do it in perfect conditions.” That means it is
prohibitively expensive to produce in the West.
Most photovoltaic cells are built in China,
backed by large amounts of government
subsidy and where lower-wage skilled labour
also helps the economics. Manufacturing costs
have fallen as the industry has grown, but there
is a limit to the energy savings possible.
In recent years, however, a new form of
photovoltaic cell has become increasingly
attractive. Instead of silicon, this type uses
various kinds of minerals called perovskites.
The first perovskite cell was developed in 2009.
It had an unpromising efficiency of 3.8 per
cent, lower than that of the first silicon cell
in 1954. But whereas it took silicon cells 30
years to get to 20 per cent efficiency even in
the lab, perovskite-based photovoltaic cells
took less than 10, reaching over 23 per cent
last year. “They’re still something like 2 to
4 per cent less efficient than [regular] solar,”
says Wheeler. “But it’s gone from mediocre
to fantastic in a decade.” >“ Solar power
will overtake
fossil fuels as
the world’s
preferred form
of electricity”
“
W
HEN I was a student in the mid-
1980s,” says Harry Atwater, “there
were only a few megawatts of
solar deployed worldwide. Enough to power
a supermarket or something. Now, solar
technology has a global output of about
500 gigawatts.” That is enough to provide
Manhattan with all the electricity it needs
about 50 times over. And solar power is
only just getting going.
Atwater, who is director of the Joint Center
for Artificial Photosynthesis at the California
Institute of Technology, has been working on
photovoltaic technology for his entire career.
He has seen it grow from a novelty found in only
a few labs into a giant industry bigger than the
flat-screen TV market. Some $131 billion was
invested in solar in 2018 alone. But Atwater
reckons the advances set to arrive in the next
few years could leave that progress in the shade.
Solar power has become so cheap that before
long, it will overtake fossil fuels as the world’s
preferred source of electricity. And a lot of low-
cost solar power will be crucial if we are to have
any chance of limiting global warming to 1.5°C.
“It’s an incredibly exciting time,” says Jenny
Chase, an analyst with Bloomberg NEF, which
looks at the costs of clean energy. “I’ve been
astonished by the progress solar has made.”
Financial company Lazard releases an annual
report into the “levelised” cost of different
energy sources – that is, the cost once you take
into account the whole life cycle of a power
plant, including manufacture and disposal,
and disregard government subsidies. Its 2018
report showed that large-scale solar power and
onshore wind were, on average, the cheapest
forms of energy. Sometimes, gas could becheaper, but more often it wasn’t. Lazard found
that between 2017 and 2018, the cost of solar
energy fell from around $50 per megawatt-
hour to around $43, a drop of 14 per cent in a
single year. Since 1976, its cost has plummeted
by about 99.9 per cent.
This has led to remarkable growth in its use.
“I’ve been an analyst for 13 years,” says Chase.
“When I started, I thought that solar could only
ever be at most 1 per cent of global electricity
generation. In 2018, it was around 2.3 per cent.
In China, it’s 2.5 per cent, which doesn’t sound
like a lot, but China uses a lot of electricity. And
in places like California, they already have 8 per
cent from solar.” Last year, a Bloomberg NEF
report estimated that the cost of photovoltaic
cells will fall by a further two-thirds by 2050,
at which time photovoltaic solar will make
up 24 per cent of global energy generation.
It is astonishing progress – and it can’t
come too fast, with soaring carbon emissions
heating the world to temperatures not seen
for 125,000 years. Solar energy, through the
venerable but reliable technology of silicon
photovoltaic cells, will be a major part of
efforts to avoid the worst of climate change.
So too will new technologies that we
can expect in coming years and decades.
First will be improvements to photovoltaic
technologies, followed by changes in the
storage of solar energy that could start to
have an impact within the next decade or two.
Finally, we may see much more speculative,
long-term ideas, such as harvesting sunlight
from space and beaming it down to Earth,
come to fruition. These latter developments
could revolutionise the energy economy.
The near-term technologies rely on new
forms of solar panel. At the moment, most
photovoltaic cells are built from silicon.
The first practical photovoltaic cell, made by
Bell Labs in 1954, turned just 6 per cent of theIvanpah in California
is one of the world’s
largest solar sites