It’s encouraging to see so many of the world’s nations acknowledging the urgency of climate change and agreeing to work toward deep decarbonization (i.e. aiming for net-zero emissions post 2050) under the Paris agreement. But at the same time, it’s disconcerting that, despite the enormity of the problem and the limited time we have to ward it off, many climate activists are still advocating for a “renewables-only” strategy that would exclude other useful climate tools. To explain why this is such a risky course of action, Third Way decided to create an animated video we’re calling “We Need a Mix”.
The challenges associated with a 100% renewables strategy are complex and hard to cover fully in one short video. So we thought it was important to provide any intrigued/confused/skeptical viewers with a bit more background on our main arguments, which you’ll find below. Our hope is that this project leads to a more complete and robust conversation about how we can win the fight against climate change. We look forward to hearing your thoughts on the matter. Send us an email, or Tweet us at @ThirdWayEnergy and join the conversation using #WeNeedAMix.
- Meeting our climate goals will require deep decarbonization, which means that emissions from our power sector, and the rest of the economy, should go down to zero shortly after 2050.
- Renewables will play a critical role in reducing our CO2 emissions, but it is not currently clear that they can reliably and affordably provide 100% of our energy mix.
- We need to support a mix of low-carbon technologies to increase our chances of meeting our climate change goals.
It takes a LOT of wind and solar to replace energy-dense fuels like fossil fuels and nuclear.
Every energy source has a different potential in terms of how much power it can provide from a given land area. This can be referred to as power density. Renewables have a much lower power density than conventional sources.
The diagram below illustrates a comparison of the land area needed to produce 1000 MW from wind, solar, and nuclear energy. In a country like the U.S., we actually have plenty of land. That’s not really the concern here. What we’re trying to demonstrate is the comparatively massive amount of infrastructure that wind and solar require, due to their low power density. This means that it will take a lot more turbines and solar panels to produce the equivalent amount of power of conventional sources that currently provide the majority of U.S. power.
Part of the reason why we need so much more wind and solar to produce the same amount of energy is because wind and solar are only producing power part of the time.
All electricity sources are rated by their “capacity factor”: the ratio of the actual amount of electricity generated by, say, a wind turbine or a solar facility, versus the maximum amount of electricity that the plant theoretically could generate if it ran continuously and in ideal conditions. Because wind and solar are variable — the wind sometimes doesn’t blow, and nighttime and clouds limit sunlight — the capacity factors of these two variable renewable energy sources are extremely low.
To produce the same energy output as conventional power plants, more wind and solar have to be built. In the picture above, between 1,900 MW and 2,800 MW of wind capacity would be required to produce the same amount of electricity as a 1,000-MW nuclear plant in a year.
A well-known study that proposes running the entire US economy on renewables estimated that we’d need to build 484,000 wind turbines…and a bunch of other stuff.
In recent years, some of the most prominent and effective climate advocates have taken up the message that we can decarbonize our economy using only renewable energy sources. One study that is often referenced to support this belief proposes to run the entire US economy, including the transportation sector, on hydro, wind, and solar sources by 2050. As we mentioned above, renewables are much less dense energy sources, so this effort requires an enormous amount of new renewables infrastructure to replace fossil fuels and nuclear generation.
The study proposes a long list of generation units that we’d need to add in order to meet demand:
Getting to 484,000 wind turbines isn’t all that farfetched. The U.S. currently has over 52,000 wind turbines, so this would be roughly an 8 fold increase in the number of turbines. Things get a lot more complicated, however, when you dive deeper into the details. For example, this study proposes turbines that are much larger than today’s average turbine. So it actually calls for 38 times more wind capacity than we currently have. Plus, 156,200 of the turbines required by the study (30% of the wind power that is needed) is projected to be offshore. Building offshore seems like it should be straightforward (the ocean is huge, there are no homes or businesses to disturb, etc). But it is actually more challenging to build offshore wind than onshore due to the need for specialized technology and infrastructure. This is why offshore wind is currently one of the most expensive energy sources, costing at least twice as much as land‐based turbines.
“Currently there are approximately only 40 solar thermal and solar PV units with a capacity greater than 50 MW in the US. The proposed plants would increase PV generating capacity 245 times!”
The amount of solar power proposed by the project is even more surprising: 46,480 solar PV units rated at 50 MW, and 2,273 concentrated solar units at 100 MW. Currently there are approximately only 40 solar thermal and solar PV units with a capacity greater than 50 MW in the US. The proposed plants would increase PV generating capacity 245 times!
According to this study, relying entirely on low-density renewable energy sources to meet all of our energy needs would require an astounding amount of new infrastructure.
Setting aside the cost, we’d likely have to overcome major legal and political challenges to get all of these facilities built. Just to give you an idea, developers of the Cape Wind project struggled unsuccessfully for 14 years to build just 130 turbines.
Unfortunately, renewable energy brings some political and legal challenges. Siting and constructing a wind farm, for example, requires permits from local governments and assessments of environmental impacts. Land use needs, impacts on wildlife, as well as the sound and visual impacts are common concerns that arise in this process. As a result, some proposed wind and solar projects are delayed or — worse yet — defeated. The Cape Wind Project proposed in Nantucket Sound off the coast of Massachusetts, which would’ve had a capacity of 486 MW of clean energy, was never built due to staunch opposition from local residents. Another 200 MW wind project in the Nevada desert was recently killed by the US district court due to a lawsuit filed by locals and conservationists claiming the project would have a negative impact on wildlife in the area. Unfortunately, this opposition to renewables development could end up doing more damage to the environment than good, especially if these projects would have replaced fossil fuels.
This isn’t to say that wind and solar are the only generation sources that face these challenges. We’re under no illusion that a small modular nuclear reactor or a natural gas plant with CCS would sail through the permitting process. But, going back to our conversation about energy density, we’d need far fewer of these facilities than we would if we generated the same amount of electricity from wind and solar. And the more building you have to do, the more siting and permitting hoops you have to jump through.
The most practical places to build wind and solar are windy and sunny places, and those tend to be far away from where people live. So we’d have to build transmission lines. A LOT of them.
As renewable generation increases, additional transmission infrastructure is required to deliver electricity from cost-effective remote resources to cities. Generating power in these areas tends to offer better economics and scalability than distributed options like rooftop solar, which is expanding in many areas of the country.
By connecting renewable generation in diverse geographic areas, new transmission also helps balance energy supply from intermittent technologies (i.e. it must be windy somewhere, right?).
“But when we say in the video that we’d need a lot of transmission to achieve a 100% renewables grid, we weren’t exaggerating. If anything, the video understates the enormous need for new power lines.”
But when we say in the video that we’d need a lot of transmission to achieve a 100% renewables grid, we weren’t exaggerating. If anything, the video understates the enormous need for new power lines. A National Renewable Energy Laboratory (NREL) study that modeled a scenario with 50% wind and solar estimated that it would require a doubling of current transmission (in MW-miles) to support this amount of generation. So imagine what a fully renewables grid would need.
But building new transmission is really hard. Especially when it comes to siting and permitting power lines through multiple states. It takes a lot of time, money, and public cooperation.
The NREL study discussed above states: “Significant institutional obstacles, including constraints in siting new transmission lines, cost allocation concerns with transmission projects, and coordination between multiple governing entities, currently inhibit transmission expansion.”
Clean Line Energy Partners, a transmission developer who is proposing a series of long-distance lines to bring low-cost remote wind energy to demand centers has been struggling to get approval for its projects for several years. One of these projects, the Plains and Eastern Clean Line, which would bring inexpensive wind energy from Oklahoma to the Southeast United States, was unable to obtain approval from state authorities in Arkansas in 2011. The Department of Energy recently decided to step in and use its authority under the Energy Policy Act of 2005 to move the project forward. Another similar project in Missouri was stopped by state regulators in 2015. These projects would take an important step forward in boosting the share of renewables on the grid, and we’re hopeful they find a way to advance. However, these would represent just a small fraction of the total long-distance transmission infrastructure that would be needed in a 100% renewables scenario. We need to consider these challenges as part of a realistic set of assumptions when planning our approach to decarbonization of the power sector.
Most importantly, wind and solar only work when the wind blows or the sun shines.
One of the bigger challenges for incorporating solar and wind into the energy mix is that they are variable. Solar installations don’t produce electricity at night or when it’s cloudy, and wind turbines don’t generate electricity when the air is still. This can pose challenges for grid operators. The job of an electric grid operator is to ensure that there is always enough electricity in the grid to meet the demand of energy users. This requires the operator to make changes on a minute-by-minute basis to make sure that supply meets demand. Variability in wind and solar sources makes balancing more complicated and requires much more flexibility.
“Solar installations don’t produce electricity at night or when it’s cloudy, and wind turbines don’t generate electricity when the air is still. This can pose challenges for grid operators.”
Simply adding more wind and solar resources in geographically diverse locations can help by increasing the likelihood of capturing some wind or sun when we need it.
And adding transmission will help by increasing the access to wind and solar resources. It also relieves possible bottlenecks in transmission capacity that can occur, maximizing the amount of electricity that makes it to consumers during favorable conditions for wind and solar generation.
But because we can’t guarantee that there will be enough wind and solar for all of those high demand times, and we can’t be certain of exactly when a cloud will move in, we will always need to have some flexible units (like natural gas) that can turn up or down quickly and generally operate below their capacity. At higher penetrations of wind and solar, the result is often shorter operating hours for generating units, making cost recovery more challenging. It can also result in an overproduction of energy from renewable sources resulting in curtailment (i.e. spilling excess energy) when production outstrips demand. Wasted energy from curtailment basically makes a project less profitable to developers and less cost-effective for customers.
Most importantly, if our target is a zero emissions system, continuing to rely on natural gas systems can only get us so far (unless we have carbon capture and storage technology).
We’d also need a lot of battery storage to help balance things out.
Energy storage — such as pumped water storage, thermal storage, and batteries — can help balance out the electricity supply. For example, solar often reaches peak production in mid-afternoon. If there is more than we need, the excess solar energy could be saved in storage devices and used in the evenings as the sun sets and demand rises. Pumped hydro and thermal are better for long term storage while grid-scale batteries are better for dealing with short-term responses to the grid, and therefore being the most valuable to respond to wind and solar fluctuations. Pumped hydro is the largest source of energy storage in the U.S. with 22 GW installed. However, due to the long permitting process, geographic limitation, and other concerns, new pumped hydro projects are unlikely. Meanwhile, grid-scale battery technologies available today are too expensive to make broad deployment viable.
Shifting the energy use of some consumers can make it easier to balance supply and demand too.
Demand response programs provide an opportunity for commercial, industrial, or residential users to reduce or shift their electricity usage during peak periods in exchange for financial incentives. There is certainly important potential for demand response to enable greater penetration of renewables: if grid operators can count on fast-acting customer responses to reduce demand rather than firing up fossil fuel plants to increase supply, they will have greater flexibility when the sun isn’t shining or the wind isn’t blowing and might not have to build as much backup capacity.
While demand response is inexpensive, it requires new regulations and utility-designed programs to operate (i.e. creation of market programs that incentivize demand response and install the necessary automated system to adjust demand in real time). Although demand response is a promising balancing tool, further work needs to be done to assess its potential and interventions may be needed to overcome market barriers.
Wind and solar are important pieces of the climate puzzle. Despite their challenges, we know we can get them up to at least 30% of our power mix. And we should work really hard to go even further.
We have already seen several states and even entire countries reach very high rates of renewable penetration. Wind has exceeded 20% of total generation in South Dakota and Iowa and has even exceeded 50% of penetration in Colorado for short periods of time. Countries like Denmark (33%) and Spain (20%) also generate very high percentages of their electricity from wind. But what is possible in each region will vary depending on the geography and the existing power system. And in some cases, higher penetrations are only possible as a result of a region being part of a larger grid system which allows access to back-up energy and a market for excess generation when needed.
“Even if we do eventually solve all of the technical issues and get wind and solar higher through fixes like deploying extremely large amounts of transmission and storage, each solution comes with a cost that can quickly erode the practicality of a renewables-only strategy.”
Even if we do eventually solve all of the technical issues and get wind and solar higher through fixes like deploying extremely large amounts of transmission and storage, each solution comes with a cost that can quickly erode the practicality of a renewables-only strategy. NREL concluded that while a 30% penetration of variable renewables in much of the U.S. is feasible, it would require significant changes to the grid to get much beyond that level.
One important challenge that makes the economics even more complicated is that as penetration of wind and solar grows, the price that producers earn falls. This happens because of the basic economic principles: an increase in supply means lower prices. As the grid penetration rises, the revenues earned by wind and solar for each unit of generation falls (Brad Plumer explains this concept in more detail). For this reason, wind and solar have to continue to get much cheaper over time in order to be competitive.
From the consumers’ perspective, declining electricity prices sounds like a good thing. But for a producer who needs to pay for the cost of their solar panels or turbines, and try to make a profit at the same time, this decrease in price is not sustainable. This is why experts are projecting that the cost of solar will have to go as low as $0.25/W in order to achieve a 30% penetration globally. This is a significant achievement beyond DOE’s current goal post of achieving a cost of $1.00/W by 2020.
But don’t forget that meeting our climate goal requires us to eventually get to 100%.
Even if we are able to push renewables up to 50% or even 60% of our total generation mix, we will still need low and zero carbon resources to provide the rest of our electricity. To meet our goal in time to make a difference, other solutions must be ready to fill the gap. Technologies like nuclear energy and carbon capture and storage (CCS) that produce lots of low- or zero-carbon electricity, rain-or-shine, can help.
Extending the life of our existing nuclear facilities (which currently provide 60% of our zero-carbon electricity) is the easiest and cheapest way to keep our CO2 emissions down in the short term. Advanced nuclear technologies can address the perceived economic and safety concerns about nuclear energy and can provide a new, flexible, zero-carbon power source in the future. CCS can capture CO2 emissions and either store them safely underground or use them in commercial applications. CCS offers a solution to address CO2 emitted from existing fossil-fired sources including natural gas and coal, which make up the majority of our electric generation mix and likely will continue to do so for several decades.
So let’s play it smart and develop a mix of low-carbon solutions. Because we won’t get a second chance to stop climate change.
Third Way’s Clean Energy Program develops and promotes policies that will help in the fight against climate change. They have helped lead efforts to find pragmatic, post-partisan solutions to the energy challenges in the United States and expand American innovation, particularly in nuclear energy and cleaner fossil fuels. Visit our website at www.thirdway.org to learn more.