Arguments
The little-known, massive advantage that renewables hold over coal
Posted on 7 June 2023 by Guest Author
This is a re-post from Yale Climate Connections by Karin Kirk
There are many good reasons to burn less coal: It’s polluting, expensive, damaging to human health, and emits more carbon pollution than any other form of electricity.
But an oft-overlooked factor is that burning fuel to generate electricity is astonishingly inefficient. Major energy losses are an unavoidable consequence of converting heat into motion, which is how conventional power plants generate electricity. They typically burn coal or gas to heat water, which makes steam that spins the blades of a turbine that interacts with magnets to generate electricity. More than two-thirds of the energy in coal is vented off as waste heat in the multistep process of making electricity.
By contrast, wind turbines, hydroelectric turbines, and solar panels skip the step of burning fossil fuels to heat water. Instead, a turbine powered by wind or water simply turns as the current of air or water flows by it. And solar panels convert the sun’s energy into electricity using semiconductors. No steam is required for either process.
The major differences in efficiency are best appreciated visually. The animation below sums it up.
Key takeaways
- Today’s fleet of coal-burning power plants in the U.S. has an average operating efficiency of 32%, meaning 68% of the energy in coal is lost in the process of converting it to electricity.
- Methane gas — often called “natural” gas — is a bit better, with 44% efficiency, on average.
- In this analysis, renewables are defined as the sum of electricity generated by hydropower, wind, and solar.
- With renewables, no fuel is burned, so there is no energy lost in the conversion of fuel to electricity. Renewables don’t capture 100% of the solar energy, wind, or water that moves past them, but there’s little pollution or resource use. Once a turbine or a solar panel captures energy, that entire quantity of energy is available for use.
- Selecting one example from the graph above, coal and renewables generated approximately the same amount of electricity in February 2022 — around 250,000 billion British thermal units, or BTUs.
- But the amount of coal needed to make 250,000 billion BTUs of electricity was 780,000 billion BTUs.
- In other words, 250,000 billion BTUs of renewables replaced 780,000 billion BTUs of coal. That is to say, every unit of renewable electricity that’s used to replace coal saves three times that amount of energy. That’s an impressive return on investment.
- Electricity brings a societal benefit — it’s essential for powering modern life. But for every kilowatt-hour of benefit derived from coal, the impacts are levied on three times that amount. That price tag — heat-trapping carbon pollution, particulate pollution, and coal ash — come from all of the coal that heads into the power plant, even though the majority of the energy contained in the coal never reaches our outlets.
- No form of energy is without environmental and social consequences, but they certainly are not all equal. Energy that’s cleaner and more efficient is a clear improvement in many ways.
Notes and sources
The efficiency of power plants is measured by their heat rate, which is the BTUs of energy required to generate one kWh of electricity. The Energy Information Administration lists the heat rate for different types of power plants, for each year since 2011.
Data for the amount of electricity generated by coal and renewables is from the Energy Information Administration.
Find more details and infographics on the efficiency of electric power generation in this article: Energy loss is the single-biggest component of today’s electricity system.
From Key takeaways in the article
· Selecting one example from the graph above, coal and renewables generated approximately the same amount of electricity in February 2022 — around 250,000 billion British thermal units, or BTUs.
While it is true that renewable electric generation with coal, One important point in the article which is missing is how poorly renewables did during parts of February 2022. Starting Feb 23, 2022 through Feb 28, 2022, electric generation from wind was only producing 30%-40% of the average for the month.
Similar though much worse drought of electric generation from wind occurred across the north amercian continent from February 8, 2021 through february 19, 2021 ( 11 days) with a loss of electric generation from wind averaging 60-80% over those 11 days. The month of august 2022 had nearly 3 weeks where electric generation from wind was only 20%-40% of the regular level of electric generation. ( even lower percentage of name plate capacity)
I have linked to the EIA.gov website which provides real time electric generation by source.
You can follow the link to see how frequently electric generation from wind drops percepiticely for several days at a time.
I can not over emphasize the benefits of using source data for understanding and comprehending the variability of electic generation by source
www.eia.gov/electricity/gridmonitor/expanded-view/electric_overview/US48/US48/GenerationByEnergySource-4/edit
Another advantage that renewables have over coal are the CO2 emissions of first extracting that coal from the ground, and then moving it from the mine to the power plant, which can be considerable.
True, some strip mines use electricly powered draglines to dig out the coal, and some power plants are located adjacent to the pit, but in the United States most extraction is by diesel-electric excavators and haul trucks, and then huge quantities of coal are moved very long distances by rail, powered almost exclusively by diesel-electric locomotives.
David-acct at 1:
Many peer reviewed papers like Jacobson et al 2022 find that a completely renewable system can be built at a much lower cost than using fossil fuels that provides 100% of power 24/7/365. They use past weather data to show that enough electricity can be generated so that all uses are met. They measure every 30 seconds for several years to show that all needs can be met. They also put in the various times you cherry pick to see if all needs can be met during those periods.
You claim without any analysis that the supposed low wind periods you mention will cause a problem. I note that one was during the summer when large amounts of solar will be available. Sufficient battery storage to cover low wind periods is part of the system. Hydro can cover 1-2 week periods in seasons when there is not an excess of solar power.
I disagree with using ‘thermal efficiency’ to promote Renewable Energy vs. Fossil fuel use. And I also disagree with claims that ‘reliability’ of a specific type of renewable generation justifies continued fossil fuel use.
Comparisons of the relative merit of different energy generation and use (the full cycle evaluation) should be based on Sustainability and Harmfulness.
Developing sustainable improvements requires less sustainable and more harmful activity to be corrected, even if the correction is more expensive, or less efficient, or unpopular. Coal with effective CCS will have lower ‘overall, complete system, thermal efficiency’. However, based on ‘harmfulness’, that ‘lower efficiency’ is clearly better than continuing to run the coal plant without CCS. Of course, if modifying a coal plant to add CCS is not ‘cost effective’ compared to less harmful and more renewable alternatives, then the coal plant should be shut down and replaced by the less harmful and more renewable generation. However, even more expensive replacements that are less harmful than existing developments should be implemented. And ‘more expensive’ alternatives could include needing to over-build the capacity of renewable generation with associated renewable sustainable energy storage. That will probably be required for truly sustainable energy generation system development.
The obvious resulting understanding is that reducing energy consumption to what is ‘truly needed’ and reducing the harmfulness of ‘that essential (actually needed, not desired)’ energy generation and consumption is the most important action. Reduced energy use is the most efficient way to limit the harm done while the system is corrected to end harmful unsustainable developed activity.
As is mentioned in the article: “No form of energy is without environmental and social consequences, but they certainly are not all equal. Energy that’s cleaner and more efficient is a clear improvement in many ways.” Reducing energy use is a very Efficient way to be cleaner (very effectively limiting harm done)’.
But the article makes a major error by saying that energy generation is “essential for powering modern life”. That fails to clarify that a major problem with modern life is the development of popular and profitable harmful unsustainable over-consumption. The more popular or profitable an activity and related beliefs become, the harder they are to correct. The ‘successful resistance’ to reducing, and ultimately ending, fossil fuel use is only one of many developed proofs of that understanding.
Supplementary points:
Michael
I again urge you and others to become familiar with the EIA detail, Its a great source of the real time and historical source data.
My comments are consistent with the NERC 2023 summer risk assessment. As noted on page 44 of the report, wind will produce in the range of 19% of name plate capacity during peak periods. fwiw, the NERC is run by individuals with actual experience .
www.nerc.com/pa/RAPA/ra/Reliability%20Assessments%20DL/NERC_SRA_2023.pdf
You make an excellent point about the inefficiency of burning fossil fuels to generate electricity. Not only does burning coal have detrimental effects on the environment, human health, and emit large amounts of carbon pollution, but it is also an astonishingly inefficient process.
David-acct,
So no analysis to respond to the scientific consensus that renewable energy can powe r the entire economy for about half ote cost of fossil fuels, including any storage needed. There are a great many scientific papers, written by specialists with actual experience and data to support their conclusions, that analyze this issue in great depth and you respond with "look at this website with no analysis".
Fwiw, NERC is a legacy organization run by utilities who have a vested interest in not changing the profitable status quo.
David-acct:
Think about it: what do you expect to happen in 50 years of BAU when all the cheap fossil fuels have been used up? Will everyone go back to living in caves or will they set up a completely renewable energy system? There is no need to ruin the entire ecosystem when we have the technology to make the switch now.
David-acct
Nameplate ratings and related performance can be misleading:
"Rated output, also known as Nameplate Rating, is determined by the wind turbine manufacturer, based on their chosen wind speed. The rated output can be a high number or a low number, depending on the wind regime chosen for performance calculations. In its current state, there is no unified approach to wind turbine ratings, making the process capricious."
upriseenergy.com/blog/2012/9/12/capacity-factor-and-nameplate-rating-explained#:~:text=You%20can%20start%20to%20see,turbine%20maker's%20chosen%20power%20rating.
There are of course periods where output of wind turbiness drops meaning we need gas backup. This is better than using gas 100% of the time. And storage systems are developing as an alternative to gas backup. There are other solutions as well.
No system is going to be perfect, but until you propose an alternative to renewables you arent making much of a case.
I agree with M Sweets take on the situation.
Michael that is an incorrect characterization of NERC. The oversee the various utilities to ensure reliability of the grid. See the NERC report 2023 summer reliability report I previous linked to.
I also urge everyone to examine the EIA . gov website I linked to above for the electric generation by source. As noted in your response to the loss of wind for the extended 3 week period in August 2022, your reply was that solar produced electricity during that period. However as noted in the EIA data, the solar electric generation is only effective for 8-10 even during the summer, thus leaving 12-16 hours dependent on wind (if not for the fossil fuel electric generation).
I have linked to the EIA electric generation website so that everyone can see the raw real time data.
David-acct:
So still no analysis to support your wild claim that renewable energy cannot supply all energy for the whole economy. You are like the people who said ICE cars would never be used because there were no gas stations. Only a partial renewable energy grid has been built. Obviously the partial grid cannot supply total energy since it has not been finished yet. Batteries are now cheaper than gas peaker plants for storage.
I am amazed that solar power does not provide energy at night!!! (/sarc)
I note that baseload fossil plants cannot supply peak power in the middle of every day. Somehow the grid does not collapse when the baseload plants cannot supply enough power. Perhaps a renewable system will have some way of providing stored power (batteries) when solar and wind are low.
You are wasting my time with your repetitive, unsupported claims.
All critique of specific energy generation sources taken in isolation are myoptic and flawed. The SYSTEM of solar/wind/existing-hydropower as firmed with battery, pumped hydro, demand response control DRC, and distributed energy resources DER, is far superior to the SYSTEM of fossil/nuclear as firmed by natural gas peakers and substation burn-off of overcapacity all night.
It is equally flawed to ignore the SYSTEM of blending/sharing/pooling/shifting/shaving/smoothing functions of grid interconnection, especially as HVDC and transactive smart grid features continue to incorporate DRC and DER. Grids are going transcontinental now.
Finally, the efficiency ratio of output energy from input energy sources that are perpetual, ubiquitous, and essentially infinite is a meaningless number. Comparing technology based generation to fuel based generation on that basis is a logical fallacy. All that matters is $/kWh and grams CO2/kWh. The SYSTEM handles spatial distance and temporal load matching issues.
Much of this is evident in the prior comments here (thanks all) and the specific mention of Mark Z. Jacobson's work.
For those of you following the old PNAS Jacobson/Clack debate... Clack has long since come over to the 100% renewables side.... just follow Clack's publications to confirm.
Leonard Bachman @12,
I agree in general with your points. But I have concerns about part of what you presented.
I am a civil engineer with an MBA. My initial interest in climate change was how it would impact items I design. I quickly learned that a rapid ending of the climate change impacts, a strict limit on impacts to levels to only slightly higher than 1.0 C of warming, was required to establish reasonable certainty regarding the design requirements that would adequately limit the probability of future harmful outcomes. How severe will a severe rain or wind event be? That depends on how severe the peak level of climate change impact is. How easy is it to be certain about regional climate change design requirements? The less total impact when human impacts are ended the easier it is to understand the likely design impacts.
However, my interest has expanded to become the larger scope of development of sustainable improvements (the Sustainable Development Goals and improvements of them). Climate change impacts challenge the development of sustainable improvements. Certainty regarding the limit of harm done by damaging developed activities is required to develop adaptations that will be sustainable.
From that perspective, admittedly not the developed norm, I agree in general with your points. However the statement that “Comparing technology based generation to fuel based generation on that basis is a logical fallacy. All that matters is $/kWh and grams CO2/kWh. The SYSTEM handles spatial distance and temporal load matching issues.” is itself a narrow and potentially flawed presentation.
Grams of CO2/kWh do matter. But things like grams of CH4/kWh also matter. And other unsustainable impacts of developed popular and profitable activity also matter. Most important is understanding that the amount of accumulating impact of CO2, or other harmful human impacts, need to be based on the full cycle of the system ‘From obtaining the materials used - to the end of use impacts’.
Stating $/kWh first is a more problematic part of the presentation. That could be interpreted to mean that more CO2/kWh, or other unsustainable impact, is justified if it is cheaper. That only applies if the marketplace effectively fully costs all harmful unsustainable impacts. And that price must be certain to be the cost of effectively neutralizing the impact. The marketplace marketing also needs to effectively reduce the popularity of less sustainable alternatives. And any required collective action to neutralize the impacts, because the people benefiting are not required to pay up front for the complete neutralization of impacts, should be certain to be publicly funded by the extra fees and taxes collected from those who personally benefited from the permitted damaging activities (activities that are permitted to not completely neutralize negative impacts).
Leadership (in business or politics) is understandably unethical if it permits or encourages accumulating damage to be done because of expectations of ‘temporary perceptions of benefit for their portion of humanity and it is perceived to be more beneficial if the harms done do not have to be neutralized by those who are benefiting’ (from a sustainable development perspective total humanity includes all future humans).
Without the full cost to neutralize the impact being priced by the system games get played to claim that benefits obtained excuse the harm done. Those games include trying to claim that a lower price is applicable to the harm being done (economist game playing regarding ‘Carbon Pricing’ is an example). And those games discount the consideration of damage done to others who are not considered to be important people (higher discount rates lead to a lower ‘Carbon Price’). Those games also try to attract popular support for misunderstandings that appear to justify or excuse the harmful actions. And making $/kWh a governing consideration can fuel popular support for harmful misunderstandings.
The responsible ethical order of evaluation is like the evaluations of alternative ways to engineer something. The cost comparison only applies to the alternatives that meet stringent limits on potential for harmful results. Any cheaper option that is more harmful or more likely to be harmful is excluded from consideration.