Yves here. While this analysis is helpful and I assume directionally correct, it appears to omit a key source of energy loss of renewables: that of storage costs, as in moving energy in and out of batteries. That isn’t always necessary (think using solar panels for home power during the time of day when the sun is shining) but it should be included to make an apples to apples comparison. The article does mention battery conversion costs, but uses the most efficient type of batteries, large scale used at utilities, and does not mention the presumably less efficient ones used in residential and smaller industrial settings. Do readers have any data on those types?
By Karin Kirk, a geologist and freelance writer with a background in climate education. Originally published at Yale Climate Connections
Traditional electricity generation has a thermodynamics problem: Burning fuel to generate electricity creates waste heat that siphons off most of the energy. By the time electricity reaches your outlet, around two-thirds of the original energy has been lost in the process.
This is true only for “thermal generation” of electricity, which includes coal, natural gas, and nuclear power. Renewables like wind, solar, and hydroelectricity don’t need to convert heat into motion, so they don’t lose energy.
The problem of major energy losses also bedevils internal combustion engines. In a gasoline-powered vehicle, around 80% of the energy in the gas tank never reaches the wheels. (For details, see an earlier post comparing the efficiency of electric vehicles and internal combustion engines.)
Fossil-fueled power plants are more efficient than a car’s engine, but they still grapple with the same obstacle. In both cases, converting energy from one form to another leaves only a fraction of the original energy left over to accomplish the intended task.
Traditional Thermal Power Plants Lose Most of the Energy Going into Them
Through the ages, the most common way to make electricity has been through thermal generation, with the process beginning by generating heat. That heat is then used to boil water and make steam, which spins a turbine that generates an electric current. The fuel source can be coal, natural gas, or nuclear fission, but the process is similar – and very inefficient. The majority of the energy that goes into a thermal power plant is vented off as waste heat. Additional minor losses come from the energy used to operate the power plant itself.
In contemporary thermal power plants, 56% to 67% of the energy that goes into them is lost in conversion. But the impacts of mining, processing, greenhouse gas emissions, particulates, and other forms of pollution are levied on the full amount of fuel consumed at the upstream end of the process, not just on the minority that eventually reaches your outlets. The same is true for the price tag, of course, which is all the more noticeable as the cost of natural gas is increasing.
How Do Sources Stack Up?
The efficiency of power plants is measured by their heat rate, which is the BTUs of energy required to generate one kWh of electricity. This simple math compares the total amount of energy entering the power plant with the amount of electricity that leaves the plant and heads out onto the grid.
The Energy Information Administration lists the heat rate for different types of power plants, and the average operating efficiencies of thermal power plants in the U.S. in 2020 were:
- Natural gas: 44% efficient, meaning 56% of the energy in the gas was lost, with 44% of the energy turned into electricity.
- Coal: 32% efficient
- Nuclear: 33% efficient
Efficiency of Renewables
What about the efficiency of renewables? A wind turbine is around 35 to 47% efficient. But wait, isn’t that the same low efficiency as coal and gas power plants? Well, yes…and no.
Comparing renewable energy with fossil fuels isn’t an apples-to-apples comparison, because renewables don’t use fuel.
A coal plant with 32% efficiency still burns 100% of its coal. The impact of burning coal is based on how much coal is burned, not how much electricity is generated at the end of the process. But a wind turbine that converts 32% of the passing breeze into electricity isn’t consuming anything.
Although wind turbines capture only part of the air moving past them, that’s not as problematic as the inefficiencies of fossil fuel plants, because the wind itself is free, nonpolluting, and is regularly supplied by the atmosphere. The same can’t be said for coal or gas.
Nevertheless, the more efficient a given wind turbine, the fewer of them that are needed. So efficiency does matter, albeit in a different way.
Solar panels range from around 18% to 25% efficiency, with steady gains in efficiencies in recent years. As with wind, the inefficiency of a solar panel doesn’t mean the Sun has to emit more energy to power the panel. But more efficient solar panels generate more electricity from each panel, which saves materials and land area.
Hydropower is the champion of efficiency, coming in at around 90% efficient at converting moving water into electrical current. Part of hydroelectricity’s impressive efficiency is that dams funnel water directly through turbines, whereas wind turbines simply sit in the midst of moving air and convert some of it to electricity.
Replacing Thermal Electricity Generation Cuts Overall Energy Consumption
Electricity generation accounts for 24% percent of U.S. greenhouse gas emissions. An unsung benefit of replacing fossil-fueled thermal electric generation with wind, solar, or hydropower is that all of the fuel that ends up as waste heat simply doesn’t need to be replaced at all. More efficient methods of generating electricity renders the whole problem obsolete.
Consider a coal plant that consumes 1,000 megawatts of coal per hour and produces 320 megawatts of electricity per hour. It’s only the smaller number that needs to be replaced with a different source of energy. But that replacement would save 1,000 megawatts worth of pollution and fuel costs. Furthermore, switching to inherently efficient forms of energy means that less energy, overall, is needed.
Energy Losses Exceed Energy Uses
The figure below shows how energy flows through today’s U.S. electricity grid. This information is more commonly illustrated from the downstream end of the power plants, but by including all of the fuel that goes into the power plants, it’s easier to appreciate the magnitude of energy used throughout the entire process – and the massive amounts of energy that will be saved as coal and natural gas are replaced with renewables.
Using the above numbers from 2021, and considering the entire fleet of energy sources, more energy was lost in conversion than was turned into electricity. The largest component of today’s electricity system is energy loss.
Energy Transmission and Storage Cause Smaller Losses of Energy
Regardless of the source of electricity, it needs to be moved from the power plant to the end users. Transmission and distribution cause a small loss of electricity, around 5% on average in the U.S., according to the EIA. The longer the distance traveled, the more the loss of electricity from transmission lines, and this energy loss is the same no matter what type of energy feeds into the grid.
Energy storage is an increasingly common part of the electricity supply, and storage is an essential element of decarbonizing the electricity grid. How much energy do batteries lose? The round-trip efficiency of large-scale, lithium-ion batteries used by utilities was around 82% in 2019, meaning 18% of the original energy was lost in the process of storing and releasing it. Batteries are getting more efficient over time, and the Department of Energy’s grid storage research uses a battery efficiency of 86% in its estimates.
A Better Way
Because fossil fuels have been the norm for most of the world’s energy for over a century, the thermodynamic challenges of burning fuel have long been accepted as an inevitable side effect.
The Energy Information Administration euphemistically describes these energy losses as “a thermodynamically necessary feature” of thermal electricity generation.
But as the world looks to re-shape the energy supply, major losses of energy are neither necessary nor a feature of modern electricity. A cleaner, and leaner grid could lower overall energy consumption, produce less pollution overall, and emit far less climate pollution. One might consider these improvements to be the critically “necessary features” of tomorrow’s energy system.
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This is somewhat disingenuous. I’m a strong proponent of renewable energy sources, but being loose with the truth is not helpful. 100% energy conversion into electricity is thermodynamically impossible.
Wind, solar, and hydro ALL have conversion losses. Whether this matters when you are otherwise getting the energy almost for ‘free’ is arguable. But to say that the don’t have conversion losses is wrong.
-Typical solar cells are 20% efficient. Thus have 80% of their energy lost to heat. This is pretty clear cut.
-Hydropower has notable losses in the turbine and the generator but are very good and up around 90% or more. They rest is lost to waste heat.
-Wind power I couldn’t readily get figures on but you can guarantee that a non insignificant amount of energy is lose to waste heat.
In all these renewables there has been strong drives to improve efficiency and thus reduce waste heat. We wouldn’t be doing that if as this article claims “there are no conversion” losses.
What is also missing in the analysis is the energy that is used to produce the equipment and mine resources. E.g. How much energy is required to purify silicon and produce solar panels? How much to mine lithium? How much to mine coal, uranium, and produce all the heavy mining equipment that is required, etc. Transport costs? etc. I know it’s complicated, but eventually for climate change it is the overall footprint that counts.
Did you read the article? It covers this.
You need to read the article more carefully and the associated links. Each of these explains what it means by conversion efficiency. It is the conversion of the useable energy into electricity. Pretty much every point you have raised is addressed in the article.
Nowhere does the piece make the claim 100% efficiency is possible, or that renewables don’t have conversion losses. It doesn’t make any technically incorrect claims but does suffer from oversimplification and omissions.
And you’re also being disingenuous. Regarding solar efficiency, 20% is the percentage of available energy the cell is able to capture and convert to electricity. There is no “heat loss” or “waste heat” because the solar energy is hitting the same patch of earth if there’s a panel there or not. If there’s a panel there the electromagnetic radiation hitting the panel is converted into electricity (20%) and thermal energy (80%, which is converted and then released to the environment by the material in the panel). If it hits bare ground, it’s also converted to thermal energy released to the environment, and 100% is “lost”.
I didn’t see anything in the main article about solar panel “energy payback”, how long does it take pay the carbon costs of manufacturing the solar panels. This Nature article (2016) has some good information:
Re-assessment of net energy production and greenhouse gas emissions avoidance after 40 years of photovoltaics development
https://www.nature.com/articles/ncomms13728
Energy pay-back times drop from around 5 years in 1992 to around just under 1 year for poly-Si and just over 1 year for mono-Si PV systems currently. Greenhouse gas emissions from photovoltaics, expressed in grams of CO2-equivalent per kilowatt-hour (gCO2-eq kWh−1), show large variations, even for studies analysing PV systems from the same year.
a less technical article (2017)
Do Solar Modules Ever Repay Their Energy Debt?
https://artisanelectricinc.com/solar-modules-ever-repay-energy-debt/
None of this talks about the backside of solar panel story. What happens when you need to recycle 10s of Gigawatts per year of solar panels 10 to 20 years from now. Some wind farms are starting to see the wind turbine recycle problems.
You seem to have missed an important feature of renewable energy sources. While it is true that solar, wind, and hydro are not 100% efficient, it is also true that these renewable energy sources do not waste any polluting energy in the process of generating electricity. Sunshine is not polluting. Nor is wind and flowing water. Coal and natural gas are very polluting, so inefficiencies in their use in generating electricity produces wasteful pollution. This is the basic point of the article. Nitpicking on how efficient renewables are is not at all productive. It is clear that renewables are far more efficient, and far less polluting than are carbon based fuels, along with nuclear.
It’s not “nitpicking” to consider conversion efficiency, as solar and wind require a surface area proportional to desired output. While dedicating surface area may not be polluting, per se, it’s not without consequences either.
I believe you are lost on the heat loss issue. Since solar, wind and hydro are not using heat to generate steam, the heat loss is not applicable. The primary factor is that solar, wind and hydro have a zero dollar cost of mining, transporting or purchasing fuel for energy production. Zero. Yes, there are infrastructure costs and solar cells are not yet that efficient. But the cost of these fuels is FREE, before conversion into energy. You cannot say that for any fossil fuel or the energy costs of their production. Also, My region has a couple hundred miles of transmission lines and they do indeed lose a significant amount of power over these lines.
For whatever it might be worth, one might note it is also disingenuous to treat just the act of conversion into energy in the form of electricity as the only thing that happens in a large, complex society that embodies “Today’s Energy System.” For example, the batteries (typically lithium based) used to store solar power (cloudy days and night time, etc.) are reasonably (although not perfectly) efficient in charge and discharge cycles, but they are impressively inefficient (and kinda poisonous) to make, and they are entirely “inefficient” to try to get rid of / do something with at the end of their (relatively short) useful life…
That may well be true, but compare that problem to de-commissioning a nuclear power plant. Or taking down a coal or natural gas fired power plant.
They need to develop systems that reuse the heat energy. I suspect most of it is released into the atmosphere.
Energy can’t be reused, only converted.
Just a quick two points on energy storage:
1. It is a mistake to focus on lithium batteries as the main focus for energy storage. Nobody – literally nobody – who works in that sector thinks that lithium batteries are, or will be the main source of storage going forward. Their early dominance is simply due to cost and availability, or put another way, China was churning out lots of them cheap, so they were available for lots more uses than previously anticipated. Other battery designs plus various forms of thermal or pressure storage are likely to become much cheaper and easier to scale. Lithium batteries can provide one element of storage (put simply – medium term – 2-24 hour storage), but there are already much better options for longer term storage and short term peaking requirements.
2. I’m tired of saying this btl, but the need for storage is not unique to renewables. The first wave of investment in energy storage (mostly pumped storage) was in the 1970’s and related to the difficulty in managing demand/supply curves from thermal heavy grids. It was the easy and relatively cheap availability of ccgt gas turbines plus cheap oil (meaning distillates provided good short term bridging power for peaks) plus investments in larger more robust grids that meant it was not needed so much from the early 1990’s for about 2 decades. Any grid which loses its cheap peaking power supply either needs to massively overbuild its thermal supply to compensate, hugely increase its interconnectivity to other grids, and/or invest heavily in storage. The particular characteristics of solar/wind alters the dynamic, but does not fundamentally change the problem. If you have a nuclear heavy grid you have the exact same problem as the French have been finding out.
Supposedly there’s a new generation of nuclear power generators which can be started/stopped quickly. Though personally I tend to put claims from the nuclear power industry in the same category as claims from the AI industry.
The other solution is to find ways to use that energy. For example a lot of people used to heat their water at night (in a well insulated water tank), some companies were quite effective at using energy at night for energy intensive operations.
With solar heavy grids, power companies already price the electricity to shift power use to day time.
So people are incentivized to charge their electric cars, run their laundry and dish washers, run their electric ovens, etc. during the day. However, the peak prices now fall in the late afternoon and early evening, as people turn on the home air conditioning, cook dinner, and run their home entertainment systems.
I may be misreading your comment but peak prices go up in Southern Ca in late afternoon and early evening because electricity use soars for the reasons you mention. Air conditioning is the big one and for an average house like mine I think it is like 3500 Watts per hour and probably higher during the last heat wave. And I am all for renewables but would it not be more efficient to be subsidizing better construction? If one could knock that 3500 watts per hour down to 1500 and consider doing that for 10,000 tract houses in Southern Ca it seems like that would make a big difference. There are design elements and construction techniques that can do this and considering the 15,000 cost of a new A/C unit these are very cost effective. For example a light colored roof, attic fans, swamp coolers when it is dry heat, better insulation etc. Anyway even though I am a victim of the variable power rates I am all for them. Raise the price enough late in the afternoon and people will figure it out. Problem is that our politicians refuse to push that because the voters just want cheap power when they want it and do not really care about saving energy.
Particularly talking about grid scale long term and flexible energy storage is when hydrogen might do a good service though sometimes i think that the approaches being taken are incorrect. It is true, for instance that energy losses during H2 electrolysis are large but such losses are better than, let’s say, simply wasted energy. I believe that grid integrated hydrogen facilities (rather than utility integrated) might be used to reduce losses due to congestion in grids. In such case you do not distinguish between black, grey or green hydrogen, it is obtained from whatever stream causing grid congestion. I believe that losses due to grid congestion are quite large and these are not discussed in the article above. Another advantage is that the cost of stored kWh with hydrogen at that scale is, or will be, way lower than the equivalent with batteries.
Some more comments:
– it is disingenuous to cite efficiencies, as the article does, for renewable sources, without adjusting for their fundamental intermittency. The capacity factor on wind is low and, whereas a thermal power station of a given wattage can produce that all year (less maintenance days), the same wattage of wind turbines will only produce for on average 20-40% of the time (dummy value from memory, actually capacity factor may be higher). Similarly, solar farms have a levelised capacity but actual production will vary c. 6-fold between winter low and summer peak.
– TANSTAAFL. Thermodynamics will not permit the creation of high grade energy like electricity without some low grade waste heat/vibration/friction losses. The article is pitched in a very weird, anti-physics way. It is as if the author had written about the energy losses of powered flight and how gliders don’t have this problem, by ignoring the entire concept of gravitational potential energy.
– Related to TANSTAAFL, there is more to electricity production than efficiency losses. Maintaining an electrical grid requires *dispatchable* “spinning reserve” to maintain grid frequency. Wind turbines cannot deliver this, even though they spin, because they are not dispatchable. Solar cannot do this because it is fundamentally DC. We will always need a significant component of thermal power or hydroelectric (possibly tidal but it depends on the system design, there are slack periods) in order to manage grid frequency.
– As well as reducing losses in the electrical grid, we should be promoting local generation, to avoid transmissions losses, and co-generation of heat. Creating electricity with its losses, by any method, transmitting is over the grid, with further losses, and then using it to heat houses is stupidity of the first water! Burn logs (in a conventional fireplace or a fancy biomass boiler), use solar thermal, use factory process heat in a district heating system, use a composting heat plant, etc. We need to learn to prize electricity for electrical power, not for heat or motive power.
I think on your point on TANSTAFL, the problem is that its very difficult to compare ‘efficiency’ for finite fossil fuels and wind/sun. We want to maximise the total amount of useable energy from every kg of coal or oil or gas, but we don’t want to use (well, its impossible) the maximum amount of energy from wind or solar. In the latter case ‘efficiency’ means a balance of costs and other variables. We aren’t short of space for solar panels so one with 15% efficiency may be far more appropriate than one with 25% efficiency if other variables (cost, reliability, flexibility, etc) come into play. With wind, much the same applies. There are available designs that are around 40% more efficient at using the wind hitting the turbine than current standard turbines (i.e. using contra rotating blades), but they aren’t used yet, mostly because of aesthetics and possible reliability issues.
I’m not sure I understand yours second point – there is a technical issue with wind and grid frequency, but my understanding is that its separate from the dispatchability issue. On that subject, only distillate turbines, CCGT and hydro provide anything close to true ‘dispatchable’ energy.
On your point about using electricity to heat homes – as someone with an electricity dependent apartment, I’m not sure I’d agree. Apart from anything else, using thermal and space storage within houses is a potentially very valuable means of flattening out demand curves in electricity uses. As an obvious example, using nighttime cheap electricity to heat your daily water needs and to heat up convection heaters is a very useful means of ensuring the entire grid is more efficient, especially with more advanced thermostats.
PK, you are right. Thermal storage is a better use of electricity than it going to waste. But it is irrecoverable as electricity so another form of storage (pumped hydro; EV batteries) or a rebalancing of generation and demand would be a better solution. Excess power generation at night is either inadequate for winter heating or excessive for summer. Domestic hot water is a tiny part of domestic heat demand.
On a related note, I am suffering from utility bill shock. Project £7k p.a. for 5 bed house with 1 bed granny annexe.
£2.5k is electricity (lighting, power only, no heat and no aircon, it is UK!). Electricity is 33p/kWh. Split tariff electricity would be 44p peak, 14p off-peak. I can save £1.5k by buying a power wall and time shifting my electricity load to off-peak! I would only be able to save an extra £300 if I bought 6sq.m. of solar panels because the winter production would be negkible and summer would be dumping excess beat into domestic hot water.
The real prize is installing a biomass log boiler to replace the £4.5k cost of gas for central heating. Commercial logs are 4p/kWHh versus 10p for gas. We are lucky to have a farm with woodland so our wood is (almost) free (my labour, diesel to haul it, chainsaw it etc.).
Oh, that sounds a very painful bill. I’m grateful for living in a small apartment with south facing windows – my energy bills are pretty small, even with the near doubling here of per unit costs (I confess to not following the bills too closely, as I am very sparing with energy use so its rarely been an issue).
Our utility bill has been a rollercoaster. When we bought the house, it had belonged to the local University two owners ago – the owners who sold it to us said that when they viewed it, there were 26 students in it “everywhere, like mice!”. We bought the house with my in-laws, to future-proof their old age (if one of them dies first, the survivor will move into the granny flat).
As a result the house had a vastly overspecced(*) heating and hot water system – but from before the 1970’s oil crisis! Two boilers (Uni required redundant operations) and a separate house-sized instant water heater (fantastic piece of kit, really – American, it turns out). By the time we arrived, the 1970’s boiler were long discontinued and one had been cannibalised for parts to keep the other alive. \
They simply ate gas. Replacing them with a fancy thermal store (large 500l water tank to act as a heat battery and buffer variable heat demand and a highly efficient small boiler always working at maximum efficiency) has cut the annual utility bill from £5k to £3k. We never heat the house above 18degC and wear a lot of jumpers to keep the bill that low – and at a price of £12k for system upgrade. :-(
Now declaring war on Russia has punted it back up the field to £7k. Ah, The Price Of Freedom! I love the smell of methane in the morning! Etc. etc. Luckily the thermal store was bought to anticipate a potential move to solar thermal and to biomass, so it has all the right tappings and coils and sensors.
Biomass boilers do require an even larger heat accumulator tank because the boiler is batch-fuelled and run in successive burns and you want to store as much heat from a burn as long as possible. I had assumed I might need a second 500l tank but I was slightly horrified this week to learn it would require a 3000l baby! That’s 1.7m diameter and 2.2m tall, including insulation. It won’t fit in the boiler room (in the space left by the previous boilers) so there goes the conservatory. On the plus side, it will be warm all year and maybe we can breed orchids and poison frogs to pay for the heating? :-)
(*) one amusing feature: the remarkable Heath Robinson gas trip device that would shut off the gas main if there was a fire in the boiler room. It consisted of metal wire led horizontally around the room through eye-bolts and over a pulley, to support a huge red-painted counterweighted valve on the gas main. Halfway along the wire was a British Standard’s Institute fusible metal strip proudly rated 475degF! In the event of fire, the strip would melt, the wire would let go, the counterweight would fall and the gas supply would be cut. At the other end of the wire from the weight, there was an emergency release button that could be slammed, to release the wire manually by a worker in an emergency. It took a while to realise what this was – we thought it was a clothes-drying line! Once we realised, we gave it a wide berth because we had no idea how to replace its ancient parts.
When we upgraded the system, I finally got the chance to hit the emergency release button and… nothing happened. The wire has stretched at each eye-bolt and deformed into rigid right-angles, holding the counterweight up as nothing had happened. Absolutely useless….
Yes! This is very important, IMHO. Electrical power is very concentrated, high-value energy. It makes absolutely no thermodynamic sense to use electricity for generating heat, under most circumstances. Using heating systems to level demand in grid systems is not a thermodynamic question, but a system stability question. Implementing energy storage would remove this need and permit better use of the excess electrical energy.
Use of electricity for traction/motive power is somewhat a mixed bag, IMO. Electric motors can be very efficient (much more efficient than heat engines). Large 3-phase induction motors exceed 90-95% conversion of electrical power to shaft power. There may be some circumstances where electric motive power makes sense – especially in large industrial settings where a large generating plant could be exploited as well. In this situation, it would make less sense to use lots of smaller heat engines to provide mechanical energy, since overall energy efficiency often scales with plant size.
Right. The issue is not some theoretical “efficiency” but practicality. While there is a political angle with fossil fuel companies promoting their own interests, if wind and solar were more practical we’d already be widely employing them without government encouragement or subsidies. As for “free,” oil is also free once you pay the money to get it out of the ground. Ultimately all our energy comes from the sun whether millions of years ago (oil) or now.
And for the talk about lithium battery storage being temporary we are waiting on the practical alternative. Ultimately the only short term solution if we choose to go that way is conservation. The Europeans will be getting the forced version this winter but here in the US huge savings could be achieved simply through smaller cars, fewer flights, smaller houses. So the problem is not just practicality and efficiency but also people and their heedless desire to conspicuously consume.
” . . . using (electricity) to heat houses is stupidity of the first water!”
Certainly correct with respect to resistance heating, but how do heat pumps perform?
Thanks . . . and congratulations on your wood lot!
Heat pumps work very well and are better/cheaper than fossil fuels!
Last year we bought 5 acres with a 2,200 sq ft house that is all electric and also has a separate one bedroom unit.
The original heat pump (15 years old) died and we replaced it with a Daikin pump that has 800 SEER and doesn’t use flourocarbon working fluid.
Our usage was 1100 kWh/per month for both houses, 2 water heaters, and 2 refrigerators during the 5 weeks the temperature was between 100-110F. At PG&E’s rates, the bill was around $350/month. Now that temperatures have dropped to the 80’s, usage is around 800 kWh and costing $250/month but usage may go back up when we hit the freezing weather. We keep the house at a constant 74F.
For those that live in the US, the IRA has tax credits of about 30% that make heat pumps affordable. Plan to make your conversion next year because heat pumps are the answer to most situations.
Even though we have dead trees in the orchard, I’m not going to get out my axe to make firewood although I may use a chipper to make groundcover/compost. What I plan to do is put 3 dual-axis solar trackers and 10 small (5 kWh) wind turbines on the hill above our house so I can tell the devil (PG&E) to go back to hell.
I am very wary of heat pumps because they require electricity and, the way things are going, I am doubtful about the social capacity of Western countries to maintain national grids and reliability. I suspect the post-war cathedrals of energy that were power stations (Bankside, Battersea Power etc.) are only the reification of a post-war belief system and, literally, hierarchy that could build and maintain such cathedrals. Now the cathedrals are speculative apartments: brace for impact….
There is no way that a rooftop solar panel array can generate 7,000 kWh per month in January: I would need c. 600 sq.m. of panel rather than 6 and also the batteries in which to store the power. Even with a COP of 5 (open circuit ground source heat pump; air source will be closer to 3), one would need 120 sq.m. (200 sq.m.).
The attraction of biomass is that I only need enough solar power and battery capacity to power the system pump and I can have heat…..
From a thermodynamic nerd…..
Thank you for publishing this article. It is the most concise review of the overall problem I have seen published,
One cost that is not mentioned in this (somewhat odd) article is that there are replacement costs for solar/wind power, and these can be quite high. Solar cells become less efficient over time, and have a 15-20 year lifecycle. Wind turbines have moving parts, and so obviously have quite high maintenance costs.
I’m sorry, but this simply is not true. There are plenty of assessments of O&M comparison costs out there, nuclear is almost always the highest, CCGT plants the lowest, with solar and wind somewhere in between.
Solar panels require minimal maintenance and most modern domestic and commercial scale panels have 25 year warrantees. A minimum of 25 years is the industry norm when it comes assessing PV cell costs, and CSP set ups are even simpler and more robust.
Modern wind turbines have greatly reduced their moving parts and again, 25 year lifetime assumptions is standard in budgeting exercises. Many of the first generation of larger turbines built in the late 1990’s and early 2000’s have had their regulator lives extended, as they still operate efficiently and profitably. The skill level required (in contrast to, say, CCGT turbines) is far lower.
Wind and solar has also proven much more resilient to natural disasters, as Japan found out in the tsunami last year.
Twenty years ago we signed a purchase power contract for 10MW of wind from a project in Solano, CA. The turbines are 1.2MW each and the developer was so “worried about maintenance” that they gave us a 23 year flat price for the MWh’s of electricity. The price was less than coal and comparable to gas fired generation.
The only thing that they got wrong was that the annual capacity factor was projected to be 33% but turned out to be 28%.
Current wind prices are half of our contract because the new turbines are 14MW rather than the 1.2MW.
I had no idea that the rate inefficiency was so shockingly bad here. Is this what is contributing to the planet warming? All this lost energy? I have to say though that I am not a fan of the line of reasoning in this article. So the author says-
‘Although wind turbines capture only part of the air moving past them, that’s not as problematic as the inefficiencies of fossil fuel plants, because the wind itself is free, nonpolluting, and is regularly supplied by the atmosphere. The same can’t be said for coal or gas.’
To be blunt, I want to see ALL the inputs and ALL the outputs to see how efficient a system is. So for me that goes way back to the project proposal, the drawing up of plans, construction, running & maintenance costs and eventual disposal of that system. Precisely the sort of stuff that we never do. Ask a power plant owner about all the smoke they put out and they say they pump it into the air as it is free. Yeah, right.
And I don’t care what system you are talking about – gas, coal, nuclear, wind, hydro, solar, etc. They all have inputs and outputs. Here is a brief video showing the construction of a wind turbine from start to finish. If you watch it, reflect on all the sources going into it as well as those off screen that you do not see like road construction, technical support, etc. And then remember that this is just one very brief slice of the lifetime of that wind farm-
https://www.youtube.com/watch?v=0vE6QkvcV-s (8:14 mins)
The maximum Theoretical possible efficiency from energy from any source is 50 %
Then there are losses. Friction, Heat, waste, etc.
That includes you as an individual, your car and your house and your lawn, even if you don’t cut your lawn.
In practice: 20 to 30% as useful work.
Which brings in another parameter or definition, “useful work, which is defined in numerous ways, some quite scatological,
Combined cycled gas turbines are almost always over 60% efficient on a 1st Law basis.
This is really comparing apples and oranges. Conversion efficiency is bull, the only two metrics that matter are energy per unit CO2, for example kWhr per ton of CO2, and cost per unit energy, so $ per kWhr. For example, a solar panel with a 40% nominal conversion efficiency may use much more material and cost much more per kW than a solar panel with a 5% conversion efficiency.
Similarly for storage, if cost per kWhr is low, then lower efficiency is fine. For example pumped hydro, is inefficient, much less than 90% claimed here for hydro, closer to 50% due to pumping inefficiencies and evaporative loss. But that’s fine because it’s cheap and electricity is from a low CO2 source.
Zinc-bromine batteries, which are popular area of grid-scale storage development, have efficiency between 75% for flow and 85% for gel batteries, lower than lithium-ion, but they have lower cost, better scalability and longer lifetime. Also, production of these can be scaled up quickly.
The trap that the author falls into is trying to find a novel angle to support her thesis (renewables good :), so she she up with the whole energy efficiency. Nobody talks about energy efficiency because it’s irrelevant, cost and deployment speed are the key factors for the climate change. The question should be how fast and how much of it can we build, not should we build technology A or technology B.
Conversion efficiency isn’t bull since conversion efficiency is rarely a linear relationship. Wind speed variations, for example, would change the aerodynamic behavior of a particular airfoil in a nonlinear way. In your model the efficiencies are fixed, but this is generally not true for these systems. Averages can hide all kinds of important tipping points.
Unsaid in this article is that we are ‘always’ trying to match our Power Generation to support current lifestyles in place, rather than matching new lifestyles to most appropriate means of Power Generation.
That thinking—because it IS the system we have and know—is keeping us on this dead-ended hamster wheel.
Radical Conservation, Grid, and Local Generation need to—and can be—matched to use. We need it all now to make it into a tomorrow.
Economies based on Consumption need to be overturned as there is way more at stake.
Appreciation of the Work that electricity, and all Energy, enables is almost forgotten—until an Ian or stalled Polar Vortex show up.
Maybe that should be our guiding light first.
This focus on efficiency makes no sense and is not a useful framework for comparing conventional sources of power to renewables. The author wants to make the point that renewable energy is better for the environment. This is settled and no one needs to be convinced.
Efficiency is useful for comparing two similar machines. For example, if engine A is 20% efficient and engine B is 21%, that means that B will produce 5% more useful work using the same amount of fuel. This is a useful data point and will inform my choice of machine.
If my machine that burns coal is 20% efficient and your machine that burns antimatter is 99% efficient, that doesn’t help me decide which machine to use. Furthermore, if I have a big pile of coal and no antimatter, I won’t be thinking too hard about the efficiency of antimatter machines.
Efficiency is also a perfectly arbitrary measure. For example, the article claims that hydro power is “90% efficient” at converting water energy to electricity; but presumably they’re only counting the water already in the dam. Considering rain can fall from over 25 000 feet and the head of the hoover dam is about 600 ft, that’s a 600 / 25000 * 90 %= 2.2% efficiency at converting available hydraulic head to electricity. Which number is less of a lie, 90% or 2.2%? Are either numbers useful in analyzing hydro power vs. fossil fuels? Should we start building 20 000 ft high dams?
Conversely, the 20%-30% efficiency figures for reciprocating engines in cars is [Potential chemical energy]/[Mechanical work at the wheels]. You’ll find that the ratio of [Piston kinetic energy]/[Mechanical work at the wheels] is a lot closer to 90%. Again, which figure is the lie? When comparing hydro power to a reciprocating engine, which two figures should you compare?
So again, the article doesn’t really inform. Just say that renewables pollute less, it’s simple and clear.
The more I think about this article, the crosser I get.
“Energy Loss Is Single Biggest Component of Today’s Electricity System” is an absurd statement:
– conservation of energy means no energy is lost (we ignore nuclear reactions and E=mc^2 here)
– useful energy is lost, depending on perspective of useful
– what really happens is that EVERYTHING IN THE UNIVERSE proceeds with an increase in entropy.
Everybody needs thermodynamics 101. Life is by definition a lossy process. Every metabolic reaction results in losses to entropy, that’s what drives them. Even photosynthesis.
Worrying about energy loss in this high concept theoretical sense is tilting at windmills. If you care about CO2, then W/unit of CO2 counts (plus other pollutants).
“Groaf” is almost one for one correlated with energy use. Every energy use results in waste heat. Under reasonable assumptions of thermodynamic conversion efficiency, and 2% yearly increase in energy use (about the historical average) , the surface of the earth approaches the temperature of the sun in a couple of centuries.
“Groaf” will end. We need to deal with *that* problem. Discovering a perfect low cost energy source only makes the problem worse (Jevons, and all that).
The challenge in electricity is not energy conversion losses — engineers have known of these and calculated them for decades.
The issue is that the grid requires (not optional) a zero-CO2, baseload power source. Like it or not, coal, CCNG, nuclear, hydro are baseload. They have at, or near, 100% availability. Solar and wind are intermittent and storage solutions are very expensive and limited.
To my mind this is article is a distraction.
“Solar and wind are intermittent and storage solutions are very expensive and limited.”
Completely agree. I find it striking that the author gives us figures for how efficient wind turbines and solar panels are, when we know very well that over time they only produce a fraction of their maximum energy output. When the wind doesn’t blow, or clouds cover the sun (or it’s nighttime), wind and solar output can be drastically reduced. This is why any respectable grid system must have conventionally fueled generators capable of backing up 100 percent of what wind and solar can produce, because there will be times when the latter give you no useable output. Then consider that wind turbines and solar panels require energy to produce, and that energy will probably be from fossil fuels, and that wind turbines and solar panels have finite lives and will eventually have to be disposed of and replaced. Same for storage batteries. And this is supposed to be a “green” energy system?
Speaking of lithium batteries, I found the following article interesting:
Hurricane Ian flood damage to EVs creating ticking time bombs in Florida
Something not often discussed is who will control renewables electricity generation? Fossil fuels require huge plants with tall smokestacks, so they are ideal for being controlled by major corporations. Rooftop solar panels can be controlled at the user level. In California the privately owned utilities are doing their level best to discourage rooftop solar because it cuts into their business. Instead, they are promoting massive solar farms covering thousands of acres of formerly pristine lands. These farms they will control. Government talks out of both sides of its mouth (don’t they always) as they encourage rooftop solar to some degree, while also kowtowing to the big privately owned utilities (witness Governor Newsom in California greenlighting massive solar farms in the Mojave desert).
I recently priced solar for a 2000 sf house in SoCal. perfectly situated for solar. Newsome et al have now made it soundly uneconomic at current utility rates and I anticipate rooftop solar will be phased out other than the mandate to put it on new houses.
There are ways of smoothing out wind and solar electricity generations. With wind power you spread out the area with windmills. There is wind blowing some where in the USA all the time. You just need to build enough and have a comprehensive interconnecting grid. Solar is more difficult but you can put them in space and beam the power down to earth using microwaves or connect all the continents with under sea power cables. Note this would also smooth out the power requirements and reduce the storage requirements.
I do not have data for the USA but this is not true of wind in the EU. There have repeated examples of multi-day Continental high pressure calms in winter, with zero wind generation.
There are some safety problems with directed energy weapons / solar power beams from space.
There are some losses in intercontinental transmission, which have to date prohibited cables like you suggest (cross-Bosphorous and cross-Straits of Hercules do not count, these are shorter than undersea cables within the the EU or even within the UK). It would be feasible to power Alaska from Kamchatka though, at least technically! Australia will have to wait a while….
I considered ‘going solar’ at one point, but as I dug down into it I discovered some downsides that eventually dissuaded me from proceeding, including:-
1. the loss converting 12v DC from the battery into the 240V AC the house expects. This is variable depending on inverter efficiency, load, etc. but can significant. This can be mitigated using DC appliances, but these are expensive and with nothing like the range available, and requires wiring/rewiring the house for DC.
2. Battery capacity degrades over time. The ones we looked at only guaranteed 80% of the ‘advertised’ capacity at 10 years and 50% at 20.
3. Solar Panel output also degrades over time. Sure they’ll keep producing for years but we we’re told they’d be down to 75% after 25-years.
Thus to power our house completely and reliably by solar we’d either have to spend on significant over-capacity initially or spend on adding capacity to panels and batteries at regular intervals to sustain even the original requirement let alone additional demands.
The above considerations may – probably will – improve as the technology does, but with regret we forewent it at this time.
“Consider a coal plant that consumes 1,000 megawatts of coal per hour and produces 320 megawatts of electricity per hour. It’s only the smaller number that needs to be replaced with a different source of energy. But that replacement would save 1,000 megawatts worth of pollution and fuel costs. Furthermore, switching to inherently efficient forms of energy means that less energy, overall, is needed.”
This article is complete nonsense technically. A Watt is a unit of power, not energy. Saying “1000 megawatts of coal per hour” refers to a non-existent “thing” — it’s exactly the same error as saying “x horsepower of gasoline per hour”. Ever seen that written down? No, because it’s not a measure of anything physical but signifies mental confusion. It means bugger all to me as an engineer who retired from an electrical utility, other than I’m being presented with a non-technical type rabbiting on about something they fundamentally do not understand. At all.
Energy is watts times time as in watt x hour or watt x second. There is no “per time” divisor attached, because it’s not a time dependent quantity. A gallon of gasoline has no time included in its potential calorific energy.
Once I read that paragraph I quoted above, I gave up on the rest of the article. Nor do I think it’s possible to deliver a tutorial on fundamentals in a mere article, or I’d try. I have before many times with laymen and got absolutely nowhere. The general state of science understanding approximates zero in our society. People jump to conclusions and don’t really listen, Oh no, they know it all already, just like politicians. That’s the level of this article, I’m afraid.
Notes:
A coal thermal station is only 32% efficient? Have to be an awful one, badly run.
A commenter says maximum efficiency is limited to 50%! Complete rubbish. Not a clue. Back to ThermoD 101.
There are often high losses in local electrical distribution lines, the low level 12 and 25 kV ones around your subdivision or block. A typical feeder, as they’re called, is rated at 300 amperes of current for continuous service per phase. That’s when it’s maxed out. At that level compared to a lightly loaded feeder at five times less current, the losses are 5 squared or 25 times higher., radiated away as heat from resistance heating of the wire conductor itself. So plugging in ever more loads onto a given. feeder causes higher losses. Fact of physical life. Not even mentioned, this variable loss.
As an engineer, I’d no more set out to write an article on economic theory to feature on NC than I’d jump off a cliff. My level is understanding what Michael Hudson says in his broader strokes, not the nitty gritty details for which I have no understanding nor expertise. At least I understand my limitations on a particular subject, but most people haven’t even got the basic message == first, you have to understand and acknowledge what you don’t understand. Most people do not accept that limitation or acknowledge their knowledge horizon is limited and think they know it all. Politicians are the epitome of that syndrome. Gaily marching forward with a Grade 9 understanding of “science” is what produces all over the place hogwash like this article, which is essentially useless as a basis for the way forward.
Totally agree, the article is so poor from a technical standpoint it devalues the point trying to be made. Please use internationally recognized units of energy either Joules(J) or Watt-hours(Wh) and Watts(W) for units of power.
1000 MW in units of (coal per hour) is 17 tons or so of coal per hour, there are around 6MWH in a ton of coal.
Agreed that is a horrible way to put it …
sidd