Once upon a time, people imagined that replacing fossil fuels with renewables like solar and wind would jeopardize the electric grid’s reliability. Then along came some major countries who showed that it didn’t, and that there really are no limits to renewable integration.
The result was explained last year in a Bloomberg Business piece aptly headlined, “Germany Proves Life With Less Fossil Fuel Getting Easier”: “Germany experiences just 15 minutes a year of outages, compared with 68 minutes in France and more than four hours in Poland.”
Germany is the most powerful economy on the planet to depend so much on renewable electricity — renewables currently deliver 28 percent of Germany’s total grid power (and up to 40 percent in some regions). The United States has a very long way to go to hit that level, by which time there will be an even wider range of cost-effective strategies to deal with much higher levels of renewables.
Part One of this series explained why the International Energy Agency now projects that, for the planet as a whole, “Driven by continued policy support, renewables account for half of additional global generation, overtaking coal around 2030 to become the largest power source.” Part Two explained why renewables are going to grow so quickly in this country over the next couple of decades, especially wind and solar power, at the expense of both coal and natural gas.
In this post I’ll discuss why it is turning out to be less challenging than expected to incorporate more and more renewables into the electric grid — and to handle periods of time when demand is high but the wind isn’t blowing and/or the sun isn’t shining. As the lead energy specialist at the World Bank, Morgan Bazilian, told Bloomberg after 20 years studying this issue, “Very high levels of variable renewable energy can be accommodated both technically and at low cost.”
One very basic strategy is an improved electricity transmission system. After all, “the sun is shining or winds are blowing somewhere across the United States all of the time,” as NOAA explained in a news release for a new analysis. Researchers concluded that “with improvements in transmission infrastructure, weather-driven renewable resources could supply most of the nation’s electricity at costs similar to today’s.” According to Alexander MacDonald, co-lead author and recently retired director of NOAA’s Earth System Research Laboratory, “Our research shows a transition to a reliable, low-carbon, electrical generation and transmission system can be accomplished with commercially available technology and within 15 years.”
Quite separate from improving transmission, there are two primary ways the intermittency challenge posed by solar and wind power is being addressed today. First, half or more of the “intermittency problem” is really a “predictability problem.” If we could predict with high accuracy wind availability and solar availability 24 to 36 hours in advance at a regional level, then electricity operators have many strategies available to them. For instance, operators could plan to bring online a backup plant that otherwise needs several hours to warm up.
An even cheaper way to fill the gap from clouds or a lull in winds is to use “demand response,” which involves paying commercial, industrial, and even residential customers to reduce electricity demand given a certain amount of advance warning. As noted in Part Two, the recent Supreme Court decision in favor of demand response puts efficiency and demand reduction on a level playing field with generation, which means we’re going to see a lot more of both in the coming years, since they are the biggest and cheapest “new” sources of electricity by far.
The Court’s 6-2 decision means “consumers will now have an opportunity to receive more value from the new energy technology they put into their homes and businesses,” as former Federal Energy Regulatory Commission Chair Jon Wellinghoff explained. It “will also mean the expansion of more clean distributed resources.” Here’s why:
This is because a smart thermostat not only will lower your bills by more precisely controlling the amount of heating or cooling energy you use; it will also provide you revenue by being able to participate in demand response programs in the wholesale energy markets. This also applies to all other controls for appliances in the home, to solar PV systems on the roof, to batteries and even plug-in electric vehicles.
Now, utilities don’t have to buy a bunch of expensive, dirty fossil-fuel fired power plants that run only a short period of time each year during peak demand (or, say, when it is unexpectedly cloudy or windless) — at a very high cost per kilowatt-hour. They can simply bid for demand response resources, which are much cheaper (and, of course, generate no pollution). Wellinghoff notes, “And it applies not only to consumers in their homes, but businesses too. Large commercial and industrial (C&I) customers with the ability to bid demand response into the wholesale market are now assured the ability to do so, which will benefit the C&I customer and the system as a whole.”
A key point, though, is that new technology is increasingly making it less and less likely for there to be an unexpectedly cloudy or windless day. As a 2014 article on “Smart Wind and Solar Power” in Technology Review put it, “Big data and artificial intelligence are producing ultra-accurate forecasts that will make it feasible to integrate much more renewable energy into the grid.”
It’s already happening: “Wind power forecasts of unprecedented accuracy are making it possible for Colorado to use far more renewable energy, at lower cost, than utilities ever thought possible.” The National Center for Atmospheric Research (NCAR) in Boulder makes these forecasts “using artificial-intelligence-based software … along with data from weather satellites, weather stations, and other wind farms in the state.” And that helped Xcel Energy, a major power producer in the state, set a remarkable record in 2013 — “during one hour, 60 percent of its electricity for Colorado was coming from the wind.”
A second way to deal with the variability of wind and solar photovoltaics is to integrate electricity storage into the grid. That way, excess electricity when it is windy or sunny can be stored for when it isn’t. The biggest source of electricity storage on the grid today is “pumped storage” at hydroelectric plants. In such plants, water can be pumped from a reservoir at a lower level to one at a higher level when there is excess electricity or when electricity can be generated at a low cost. Then, during a period of high electricity demand, which is typically a period of high electricity price, water in the upper reservoir is allowed to run through the hydroelectric plant’s turbines to produce electricity for immediate sale.
In the International Energy Agency’s 2012 Technology Roadmap: Hydropower, “Pumped storage hydropower capacities would be multiplied by a factor of 3 to 5,” by 2050. The pumped storage will likely be the most useful in China and other developing countries, which is where most of the growth in hydropower is projected to come.
The round-trip efficiency for pumped storage — the fraction of the original energy retained after the water is pumped up and comes back down — is 70 percent to 85 percent. That means 15 percent to 30 percent of the original energy is lost, which is quite good as storage systems go. Consider if you wanted to use hydrogen as the way to store power, using electrolyzers to convert the electricity to hydrogen, then storing hydrogen on-site until the electricity is needed, and finally running the hydrogen through a fuel cell to generate electricity again. Losses would likely exceed 50 percent, perhaps by a lot. That is a great deal of premium low-carbon electricity to lose, which suggests that fuel cells will only be used for storage in niche applications for quite some time. On the other hand, the round-trip efficiency storing electricity in batteries is comparable to the round-trip efficiency of pumped storage.
The problem has been that, until recently, batteries have been too expensive for them to be used on a wide scale in most storage applications. But as I’ve discussed, battery prices are coming down sharply, as huge investments are being made in various types of battery technologies by electric car companies and others, including utilities. That’s a key reason battery storage for the electric grid use has started to grow rapidly in this country and around the world.
Moreover, in the (slightly) longer term, as the stunning drop in battery prices continues to spur exponential growth in electric vehicles (EVs), it may be possible to access their batteries during the more than 90 percent of the time the EVs are parked. That would potentially allow electric cars to provide storage or other valuable grid services.
Significantly, a 2014 report from the investment bank UBS projects that “the payback time for unsubsidised investment in electric vehicles plus rooftop solar plus battery storage will be as low as 6-8 years by 2020,” so this transition may start sooner than expected.
The National Renewable Energy Laboratory in Golden, Colorado, is studying how “electric cars might store power from solar panels and use it to power neighborhoods when electricity demand peaks in the evening, and then recharge their batteries using wind power in the early morning hours,” as Technology Review reported. Straightforward modifications to electric cars allow them to send power to run a home or building — and back to the electric grid. In the near future, super-accurate wind and sunlight forecasts, combined with smart charging systems will be able to optimize when EVs should be charged to ensure the cars have the power they need while maximizing their ability to help support the electric grid.
Of course, we don’t have anywhere near the quantity or quality of EVs on the road for such a use. Then again, we aren’t anywhere near the levels of variable renewables on the grid that require such a strategy. Fortunately, the rapid growth of renewables is now occurring in tandem with the rapid emergence of EVs — and in the coming decades their synergies will benefit both industries. Indeed, as the grid incorporates more and more renewables, the net carbon emissions of EVs will drop lower and lower, a true win-win outcome.
Lastly, as the IEA and NREL have both concluded, concentrated solar thermal electric power plants can build in low-cost storage (of a heated fluid) with very low round-trip losses. There is a great potential for this type of solar power plant to become a major feature of the electricity grid, especially after the 2020s. The IEA projects solar thermal could provide 11 percent of the world’s electricity by 2050 — if the nations of the world keep their pledge to continue ramping up efforts to stabilize carbon dioxide at levels that avoid the worst dangers to humanity.
As the world gets increasingly serious about replacing fossil fuels with low carbon energy, it seems increasingly clear that a combination of the technologies and strategies discussed above will be able to incorporate very large amounts of renewable electricity into the electric grid cost-effectively. The “intermittency” problem is essentially solved. The will-power problem, however, isn’t.