|A 5 year moving average of the global temperature anomaly. Source: NOAA|
Fossil fuels are very convenient. They are excellent stores of energy, conveniently transportable, and not variable like renewable energy sources (though fossil fuel power stations do have a nasty habit of breaking down in hot weather--Australia has experienced 6 major coal power stations tripping over the last few weeks). But they produce CO2, which might be invisible and only a small part of our atmosphere, but traps outgoing infra-red radiation, causing the world to heat up. And that process appears to be accelerating. Fossil fuels also produce plenty of visible pollution, and burning fossil fuels leads to the deaths of 6 million a year around the world. In the past, we put up with fossil fuels because they were cheaper than the alternative.
However, now fossil fuels have a second disadvantage, one which increases every year. They are more expensive than renewables. This is how coal dies — super cheap renewables plus battery storage shows how the costs of new wind farms with battery storage in Colorado are below the costs of running old coal power stations:
Solar, wind, and battery prices are dropping so fast that, in Colorado, building new renewable power plus battery storage is now cheaper than running old coal plants. This increasingly renders existing coal plants obsolete.
Two weeks ago, Xcel Energy quietly reported dozens of shockingly low bids it had received for building new solar and wind farms, many with battery storage (see table below).
The median bid price in 2017 for wind plus battery storage was $21 per megawatt-hour, which is 2.1 cents per kilowatt-hour. As Carbon Tracker noted, this “appears to be lower than the operating cost of all coal plants currently in Colorado.”
The median bid price for solar plus battery storage was $36/MWh (3.6 cents/kwh), which may be lower than about three-fourths of operating coal capacity.
In India, nearly two-thirds of existing coal power generation is no longer price competitive with new solar and wind projects. In fact replacing high-cost coal power stations would save Indians US$8 billion per year.
Over the last couple of years, in many countries new wind and solar farm have got cheaper than new coal power stations. Now, renewables are becoming cheaper than existing coal power stations, even though existing coal power stations are cheap to run because they have been fully depreciated. In other words, building brand new wind and solar farms would actually be cheaper than continuing to run older coal power stations, cheaper even after interest is paid and depreciation costs deducted. Why would we continue to dig up, transport and burn coal, with all its attendant filth and impacts on a climate which is already heating too fast, when we can save money by building out wind and solar farms?
The answer, from increasingly desperate denialists and coal and oil interests is that renewables are too variable. We need, they say, the stability of fossil fuels. No we don't.
This article from PV Magazine, Seasonal patterns show a need for more solar in the U.S. electricity mix, discusses the seasonal mix of wind and solar in the USA. Solar is (obviously) stronger in summer, and wind complements this by being stronger in other seasons. There isn't just a seasonal complementarity: wind in the mid-west "wind corridor" is stronger at night, when the sun doesn't shine, and dies down during the day when it does. Using both wind and solar produces a much more stable total output than using either individually. The PV Magazine article also talks about geographical differences in generation and demand:
For all of this to provide benefits on a wider geographical basis it will be necessary to have the infrastructure and market design to rapidly move and trade electricity across regions. The Federal Energy Regulatory Commission is tracking more than 4,600 miles of new transmission projects that it gives a high probability of being completed over the next two years. This is nearly 20-times the length completed in the first 11 months of 2017.
So, a mixture of wind and solar combined with long-distance power lines to bring power from windy or sunny regions to places where the demand is.
But storage will still be needed, which might come from two sources. The first is concentrated solar power (CSP):
An hour away from Area 51 in the Nevada desert, a beacon shines inexhaustibly day after day. And while its proximity to the famous classified zone makes some travelers believe they have seen something alien, the artifact is far from being extraterrestrial.
The beacon is part of a revolutionary solar generating and storage technology that may finally make solar power an undeniable competitor to coal and nuclear. With the first utility-scale facility already operating in Crescent Dunes, Nevada (and several more under development around the world), we are hopefully seeing the beginning of a new era in energy production.
The technology is called concentrated solar power (CSP) and uses a system of mirrors to concentrate solar energy and turn it into thermal by heating up a medium. The Crescent Dunes Power Plant, developed by the company SolarReserve, uses salts to capture and store the energy from the sun. The result is solar power available 24 hours a day, that can meet utility demands just like a conventional fossil fuels, except without any emissions or hazardous waste.
[Read more here--it has a nice explanation of CSP]
CSP has fallen in cost by 2/3rds over the last 4 years, from 15 cents to less than 5 cents per kWh ($150/MWh down to $50/MWh) It's still more expensive than wind and solar, but they can't provide power 24/7 like CSP can. To smooth out a blended output from wind and solar (PV) farms, CSP will be very useful.
And of course, there are batteries. The "Big Battery" in South Australia has already proved itself again and again over the last six weeks since it was opened, by helping to stabilise the grid when coal power stations repeatedly tripped. But it's not big enough to provide substantial time shifting, not yet. Battery costs will halve over the next 3 years, and probably halve again over the subsequent 3 too. At that point, batteries will become ubiquitous, both behind the meter and at wind and solar farms and on the grid.
The intrinsic variability of renewables is manageable. Using different sources of green electricity--wind, solar PV, and CSP--from geographically separated weather zones connected by HVDC lines, and stabilising the grid with batteries will reduce overall variability of supply, and at a lower cost than continuing to use fossil fuels*.
Converting electricity generation to renewables is key. If we can do that, almost all other industrial processes can be electrified using green electricity. For example, we can switch land transport (cars and lorries and trains) to run off batteries. We can convert all heating to electricity. Even where it seems impossible, for example in air transport, we can in principle produce methane from CO2 and hydrogen using green electricity via the Sabatier process, or we can produce a whole range of hydrocarbons via the Fischer-Tropf process from seawater. It's energy inefficient but it doesn't matter if green energy is cheap enough--and it's getting cheaper every year.
Even 5 years ago, wind and solar were more expensive than coal and gas. Now they're as cheap as or cheaper than fossil fuels, and their costs will go on falling. Electric cars are within a couple of years of matching the buying cost of petrol/diesel cars. Green electricity and green transport are or soon will be cheaper than fossil fuels. Weaning ourselves off fossil fuels will prove surprisingly easy.
* We might keep existing gas peaking power plants going for emergencies, but instead of using natural gas (methane) to run them, we could instead use synthetic natural gas produced by the Sabatier process produced with green electricity.