Even Greenpeace underestimated the
rise of solar. When one of the world’s largest
environmental advocacy groups released an optimistic industry analysis called the Energy
Revolution in 2010, it was far more ambitious than
any government predictions. And it still got it wrong. Greenpeace estimated that by 2020, the
world would have 335 thousand megawatts of installed
solar photovoltaic capacity. That’s enough to power
almost 64 million U.S. homes and an increase of
over 700 percent from 2010. But by the end of 2018, there
were already over 480 thousand megawatts installed globally, enough to power
about 91 million homes. Elon Musk promised the world Tesla solar
roof tiles in 2016, something the company has yet to fully deliver on. But it turns out the solar
industry may not need the upgrade. While the aesthetic of solar tiles
that look indistinguishable from normal roofing material is alluring, the
industry has been growing exponentially thanks to plain old solar panels. You can see the evidence both on
people’s rooftops and in the desert, where utility scale solar plants
are increasingly popping up. Here in the U.S., of all new power
capacity added to the grid in 2018, about 30 percent of
that was from solar. Solar in America has gone from this
sort of fringe and very expensive technology to what is effectively now
mainstream when it comes to new generation. And states like California are
leading the way with bold solar targets, incentives and regulations. Every new home built in California after
the New Year must generate as much energy as it consumes. So presumably by making the homes
very efficient and installing solar. But the picture is not all rosy. Solar power is intermittent. The sun isn’t always shining, and
the price of storage solutions like lithium-ion batteries are
still relatively high. Installing solar can be a large upfront
cost and permitting can slow the whole process down. These are real problems that the industry
needs to tackle if solar is going to reach its potential. But if the recent past is any
indication, solar power is going to help lead the transition to
a carbon-free future. And it might do it
faster than we all expected. In 2018, solar power
made up around 2.3 percent of electricity generation
here in the U.S. That number may seem small, but it’s
an impressive leap from 2008, when solar comprised a mere 0.1 percent of our electricity. Across the country and utility after
utility, what’s become fringe is the idea that you might
build another coal plant. Right. No one is
really doing that today. The surge in solar installations has been
driven by a steep decrease in the price of photovoltaics, the technology
that powers solar panels for both residential and
utility-scale use. Since the 1970s, costs
have dropped tremendously. Back then, solar on the ground
was about five dollars a watt. So 50 cents or
more per kilowatt hour. And solar is down now today, in
the best large commercial applications, at one to two cents. So a factor of 50 reduction. And on rooftop systems, if you finance
it right and you’re in a good location, your effective cost can
be under 10 cents. It does still cost a
lot to get solar. According to EnergySage, an online
solar financing marketplace, the average rooftop panel system
in the U.S. cost about $12,500 after
tax credits in 2019. But after about seven to eight
years of lower electricity bills, customers typically break even and
start seeing significant savings. And to defray the upfront cost, customers
can often get a solar loan or choose to lease the panels instead. Overall, the massive price drop for
photovoltaics is largely thanks to China’s massively subsidized solar
power manufacturing program, which created a worldwide glut in solar
panels in the late 2000s. Prices plummeted and solar companies around the
world had to find ways to slash costs to stay afloat. Lots of companies went under, but
enough innovated and survived such that in many parts of the country today,
solar can now compete on economics alone. So solar went from essentially the
most expensive form to one of the cheapest. It may be
affordable, but it’s not perfect. Solar panels don’t generate any power
during the nighttime and they’re much less effective in
cloudy or shady environments. And while the price of photovoltaic panels
has dropped, the cost of energy storage options like lithium-ion batteries
is still pretty high. For example, the newest Tesla Powerwall,
one of the few small-scale batteries meant for residential energy storage,
is priced at $7,600, not including thousands of dollars
in installation costs. So while panels often generate excess
power during the day, there’s not always an efficient way to save that
energy for later, and so customers often end up relying on
non-renewable energy sources at night. Energy storage is sort of the last
puzzle piece to come together to make solar and wind, any intermittent source, a
reality for 100 percent of our power needs. Furthermore, permitting for
rooftop solar takes time and money. And depending on where you
live, installing solar on either a residential or commercial scale can still
involve a large upfront cost, especially if your state or
bank doesn’t provide solar-friendly financing options. Solar installations require that
they have to be permitted. Whether you can do it all remotely
or whether you need a building inspector to come out to your home, all
of those add costs, add time, add delays, which all make the effective
price, if the policy environment isn’t favoring solar, often a real challenge
to get large amounts of it deployed on the residential side. You’ll also almost never see solar
on apartments or office buildings, because landlords just don’t have a
monetary incentive to install them for renters who pay their
own electricity bills. As for single-family detached homes,
about 2 percent have solar. And while this actually represents a
marked improvement, it still means residential solar is a
relatively rare sight. But experts say it won’t
stay this way for long. In California, we have a mandate to
have a million solar rooftops by the end of 2020. We’ve already met that
goal, we’re over a million rooftops now and still growing. Even if you haven’t noticed the rise
in solar roofs, visit the deserts or plains of California, North Carolina or
Arizona, and you’ll see that a large percentage of new solar
capacity comes from utility-scale plants producing hundreds of megawatts of electricity
that feed into the grid. One such plant is the California Flats
Solar Project, a 280 megawatt solar farm developed by First Solar and
located in Monterey County, California. The California Flats project
is about 2,900 acres. That’s the carbon equivalent of taking about
22,000 cars off the road and can power about
116,000 California homes. In 2018, utility scale projects like
this generated a total of 66.6 million megawatt hours of
energy in the U.S. That’s enough to power about 6.4 million homes for a year and represents
69 percent of the country’s total solar energy production. The large-scale solar projects can be
anything from a 200 kilowatt system that you might see on the edge of
a trailer park or a 400 megawatt project in the desert. However, plants on the
scale of Cal Flats are increasingly proving to be the most
cost-effective size for utility-scale operation. When you get to 200 megawatts in
size, you’re able to take advantage of scale economies so you can deliver
a really cost-effective price of solar power. But when you start getting
to larger sizes, sometimes it’s difficult to find suitable land,
to find suitable transmission capacity. So I think you’ll see probably
a larger number of midsize utility-scale installations that are more strategically located
closer to the load where the power is being used. The rise of midsize installations is
also being driven by a growing corporate commitment to
renewable energy. In 2018, corporations overall more than
doubled the amount of clean energy they bought in 2017. In 2018, Facebook alone signed
contracts for around 2.4 gigawatts of renewable energy, which is
more solar energy than the entire residential solar market in the U.S. combined. This kind of corporate buy-in
is ultimately necessary for a carbon-free future. About two thirds of power
is consumed by businesses. So even if everybody went renewable,
if all houses went renewable, you’d still only get one third
of the way there. Cal Flats has a corporate partnership
with Apple, which buys 130 megawatts of energy from the facility
to power its California operations. The other 150 megawatts are sold to
PG&E, which then combines this solar power with its other energy sources. Customers received this blended power by
default, but can opt into a program that allows them to receive more
of their power from solar or other renewable energy sources. Many people live in cities or may not
have access to a rooftop where they could install a solar system. So it’s important that we have
utility scale projects to help really create lots of opportunity for lots of
different types of customers to be able to get solar power. However, these utility-scale plants cannot
achieve their full potential without energy storage. To compete with the reliability of fossil
fuels, solar farms need to be able to generate energy on demand, not
just when the sun is shining. When I’ve got systems out in the desert
and a cloud goes overhead, we want enough of a shock absorber in the system
in the form of batteries to help cover that power
that’s missing momentarily. It could be for a minute.
It could be for four hours. Traditionally, storage has come in
the form of lithium-ion batteries. And luckily, the price for this tech
is plummeting alongside the cost of solar panels. According to Bloomberg New
Energy Finance, the average cost for lithium-ion batteries fell 85
percent from 2010 to 2018. Now, the average lithium-ion battery
costs $176 per kilowatt hour. So you can draw lines very easily in
every part of the country, part of the world, to say okay, is a
solar plus storage system today cost competitive with this
natural gas alternative? You can draw a line pretty quickly and
see where those two are going to cross for every geography. In some places, Beebe says solar
plus storage has already won out. Today in places like Hawaii and in
California, solar plus storage in most cases is more cost effective
than a natural gas contract. In other words, those developers are
winning bids, solar plus storage versus natural gas. Solar power with storage is now often
more economical than a type of power plant known as a peaker, which
operates infrequently, only firing when demand is high. In April 2019,
the utility companies Southern California Edison opted for a solar plant with
an 100 megawatt battery over a natural gas peaker plant in the
coastal city of Oxnard. If regulators approve the plans, it would
be tied with Tesla for the largest lithium-ion battery in the world
when it goes online in 2020. But unfortunately, lithium-ion may not be
able to get that much cheaper. Many experts predict that costs will bottom
out at around $70 to $100 per kilowatt hour. At this price, batteries
will continue to be an economical option for replacing peak er plants
and smoothing out hours-long gaps in solar production. But they won’t be a
good option for storing energy for weeks or months on end, as
this would massively increase electricity costs for consumers. Some people think lithium-ion
is the ultimate, and the path forward is to research heavily
for improvements to lithium-ion. Then there are others, and I count myself
in the others camp, where I say lithium-ion has done remarkable
things for technology. But let’s go to something far better. So researchers like Sadoway
are exploring new horizons. Now we’re seeing flow batteries,
which are liquid batteries. We’re seeing high temperature,
nickel metal hydride batteries. And we’re seeing other forms of
storage that are not chemical or battery-based storage ramping up
their use as well. For example, Bill Gates’ investors
fund Breakthrough Energy Ventures is backing the development of longer
duration liquid batteries that would ideally be one fifth
the price of lithium-ion. And researchers at Sandia National Labs
are experimenting with molten salt thermal energy storage. This non battery-based system uses concentrated
sunlight to heat up molten salt, which is then stored in tanks
for up to several days and later converted into steam to
power a turbine. So that power production is the exact
same as a coal-fired power plant. Except instead of burning coal, we’re
using concentrated sunlight as our heat source. As for residential solar, the
grid itself often acts as a battery. This is because most states
have net metering policies that allow customers to sell their excess energy back
to the grid in exchange for energy credits, which they can then use
to power their home when the sun isn’t shining. But whether storage comes
in the form of cheaper lithium-ion or newer experimental
technologies, Kammen says that government policies and incentives will need
to drive adoption, just like they did for solar panels themselves. Right now, the California utilities are
operating under what’s called the storage mandate. They are required by
2020 to have enough storage onboard so they can meet 2
percent of their peak demand. And we’re negotiating right now
with the state’s Public Utilities Commission to increase that number. When we get to roughly 20 percent
of our peak demand available in storage, we will be able to run a
renewable-only system because the mix of solar and wind, geothermal, biomass all backed up
with storage will be enough to carry us through even some
of these potentially long lulls. In the meantime, expect to see
solar installations continue to rise as prices fall and incentives
and regulations spur development. What we know is that utility after
utility is now sourcing wind and solar instead of sourcing coal
and natural gas. Five years from now, it will be a
little bit odd to see new homes that don’t have solar on the roof. It’ll just become part
of the landscape. At the end of the day, this is
an inexorable march toward a transition to a zero-carbon economy.