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Inconvenient Truths of Large Scale Solar and Wind Energy

image credit: Figures courtesy of https://www.biography.com/ and https://www.forbes.com/
Alan Rozich's picture
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Providing quantitative sustainability insights using sound technical analyses with a management consulting approach to craft strategies that address the mega-trends that are occurring in the...

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Al Gore famously coined the term, "​inconvenient truth,"​ to bring attention to man-made or anthropogenic carbon dioxide emissions and other related issues regarding societal functionality, the environment, and sustainability. Meanwhile, solar and wind energy are being touted with almost unbridled, messianic fervor by the main stream media as a sustainability panacea. Clearly, these technologies will play a significant role in a renewable economy. However, in the interest of hastening the ubiquitous and unquestioned deployment of these systems, their own sustainability baggage is often overlooked. These ignored "inconvenient truths"​ are subordinated in the interest of unquestioned deployment of solar and wind systems. Alarmingly, both of these platforms have major challenges that relate to sustainable land use which will only continue to worsen with the installation of larger, centralized systems.

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The Solar and Wind Juggernaut

Solar and wind power are projected to be the dominant energy sources as touted by mainstream media outlets such as Forbes who cite declining costs for both technologies as a major factor.

Forbes'​ "declining cost revelation"​ for solar and wind is somewhat pretentious considering that almost any manufactured system experiences hefty cost reductions with increased scale of production.

Others, such as climate zealots,  dutifully reaffirm these predictions and grant carte blanche approval for solar and wind in the absence of any critical thinking or value engineering analyses. Neither Forbes nor the zealots bother to understand, acknowledge, articulate, or analyze all the cogent factors impacting economics and overall sustainability.

It seems that vested stakeholders are recklessly pressing for larger and more massive installations in order to continue to drive down economics without analyzing for the potential of unforeseen and damaging consequences.

There is an alternative discourse that definitively shows that large scale solar and wind power are inherently less sustainable and, perhaps, even unsustainable, as system sizes increase. For example, there is tangible evidence that large scale solar farms are capable of causing unwanted and disruptive climate change. This prediction is not surprising because of egregious land requirements. The reality is that solar and wind require anywhere from 10 times to 1,000 times the land area that other fossil fuel or renewable energy technologies require.

Solar and wind energy systems must be players in a renewable economy. But they must be responsible players that are held accountable to the same stringent criteria as other energy sources. That is, they do not warrant a "free pass"​ simply because they are considered "renewable energy."​

Judicious Land Use Is A Vital Component of Sustainability

The United Nations defines sustainable land use as “the use of land resources, including soils, water, animals and plants, for the production of goods to meet changing human needs, while simultaneously ensuring the long-term productive potential of these resources and the maintenance of their environmental functions.”

Consequently, technologies or other human endeavors that displace thousands of acres of ecosystems egregiously compromise the Planet's ability to assimilate carbon dioxide. In the case of solar and wind, the amount of acreage displace can be orders of magnitude higher than other technologies as shown in the graph below.

Figure references: 1 Powerlink article; 2 Strata 2017; 3,4 AD, 45% & 90% conversion, repsectively; 5 NEI Report 2015

 

The data in the graph above are clear in that solar and wind systems rank at the bottom regarding sustainable land use. Consequently, there is a significant trade-off for using these technologies for large scale, centralized energy production. This information alone suggests that other alternatives merit serious consideration.

Comparison of Solar and RNG/LNG Systems Land Requirements

It is interesting to compare solar with an energy system such as RNG/LNG which has more favorable land use metrics. The graph shows the relative land requirements for solar and RNG/LNG systems for three different energy production scenarios: 10, 25, and 50 MW-Day.

  This graph and other information makes interesting points:

  • Because of the over 30 fold disparity in land area requirements of the two energy systems (Solar average = 21 and RNG/LNG = 685 from the first figure), the graph shows that for a 10 MW-Day of energy, a solar system will require a little over 100 acres more than an RNG/LNG system.
  • With high bioconversion ADs, the disparity in land area requirements of the two energy systems (Solar average = 21 and RNG/LNG = 1,300 from the first figure) climbs to 62 fold. For this case, it means that for a 10 MW-Day of energy, a solar system will require almost 200 acres more than an RNG/LNG system.

 

Summary

The need to decarbonize the global economy is considerable. Initiatives that reduce GHG emissions, particularly with respect to carbon dioxide production caused by fossil fuel energy sources, are important. However, implementing large scale solar and wind systems that have significant environmental and economic repercussions mandates the use of proven structured project development and implementation protocols that employ FEED methodologies. The FEED effort must also consider other technological alternatives. Other technological alternatives warrant consideration if only to ensure that the chosen solution is thoroughly scrubbed and not simply prejudicially pre-selected.

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Matt Chester's picture
Matt Chester on Jun 27, 2021

What about the types of land that can be used for either? Are they equally as applicable to, say, brownfields that would otherwise be unused? 

Alan Rozich's picture
Alan Rozich on Jun 28, 2021

Matt, I think you are on target. Land assets that are not viable for other purposes are probably suitable if the thinking is putting in very large systems. Also, please have a look at a response I made to another question below.

Hans-Henning Judek's picture
Hans-Henning Judek on Jun 27, 2021

Floating Solar is an excellent alternative. With increasing temperature, evaporation will become an increasingly severe problem for dams and other man-made water bodies. California is for about 20 years in a permanent drought situation with some brief interludes. Floating solar can help to reduce the evaporation problem substantially and at the same time provide a symbiotic relation to Hydropower electricity production.

If you are interested in this topic, this is the link to my LinkedIn group "Floating Solar" https://www.linkedin.com/groups/6735272/
Evaporation due to drought can lower the water level by 3m (9ft) per annum

Michael Keller's picture
Michael Keller on Jul 5, 2021

The picture demonstrates a painful problem with floating solar panels. What happens when the reservoir water levels fluctuate, plummet? Also, paving over lakes with floating panels is not the most environmentally sound approach.

There are no doubt applications where floating solar panels will work, but I suspect practical locations are limited

Matt Chester's picture
Matt Chester on Jul 6, 2021

I think you're right in that floating solar is great for certain niche applications-- it's not supposed to be a cure all, but rather there are opportunities in isolated instances where they can be quite valuable. In reservoirs attached to hydropower facilities is one I've heard-- helps prevent undesirable evaporation of those waters and certain types of algae growth, while being close to existing transmission systems on inherently calm waters. 

Hans-Henning Judek's picture
Hans-Henning Judek on Jun 27, 2021

When it is more convenient and cheaper to use agricultural land than developing marginal and wasteland:

 

Solar Parks on Fertile Land Are New Adversary of India’s Farmers

https://www.bloomberg.com/news/articles/2015-03-17/solar-parks-on-fertil...

 

 

 

Alan Rozich's picture
Alan Rozich on Jun 28, 2021

Hans, thanks for the note. What is the energy production for these systems?

Jim Stack's picture
Jim Stack on Jun 28, 2021

Alan, I am very disappointed in the data you provide. It 's seems to ignore the large wind farms on animal and crop farms that run with no change in farming below. 

   You also seem to ignore the large Solar systems integrated into the area that provide shade while making power like the ASU Campus in Tempe Arizona. It's a large Solar PV farm integrated into the largest University in the USA.  

     You mention sustsinable fosdil fuel plants since they use less land area yet you ignore the huge mining and or Fracking areas not to mention water use and pollution. 

    Please check all the FACTS and the entire systems. You will see solar and wind are good for everyone. 

Alan Rozich's picture
Alan Rozich on Jun 28, 2021

I am sorry that you are disappointed but the data did come from sources such as DOE.

I looked at this website, https://tours.asu.edu/polytechnic/points-of-pride/sunpower-solar-farm,  on the system you noted. The site describes this system as, “On the southeast side of the Polytechnic campus sits the SunPower Solar Farm, a Salt River Project and SunPower Corp. 1-megawatt solar power plant. The solar farm can concentrate the sun’s energy up to seven times to achieve one of the lowest costs of electricity for a solar power plant. The solar panel field is also capable of producing the energy needs of 225 households, and requires minimal water.”

I do not know what your idea of “large” is but, assuming that the above is the system you reference, calling a 1 MW energy system servicing perhaps 1,000 people “large” is a bit of a stretch.

Conversely, this installation is a good example of distributed solar. All technologies benefit while using a distributed resource modus operandi. Smaller, distributed resource systems benefit because the sustainable land use issues are mitigated for all technologies.

You also said, "You mention sustsinable fosdil fuel plants since they use less land area yet you ignore the huge mining and or Fracking areas not to mention water use and pollution." One point of the article is that ALL technologies, renewable or not, need to be held accountable and subjected to ALL sustainability criteria. Just because a technology is "renewable" does not preclude that other sustainability criteria are waved.

If anything, abiding by sustainable land use maxims prompts us to strongly consider distributed resource models, not “bigger is better” highly-centralized installations.

Michael Keller's picture
Michael Keller on Jul 5, 2021

Mathematics, economics and physics do not support replacing central production plants with many small generators. The sheer magnitude of energy use favors economies of scale. That same principle is seen in green energy production facilities.

The low capacity factors and intermittent nature of green resources inherently require more land use than conventional resources.

Throwing in “all-in” land needs is a two edged sword. The very large numbers of green resources needed to match conventional energy production plants inherently require vast resources to manufacture and construct the vast numbers of green energy facilities. 

Nothing is free, there is always a cost. 

Peter Farley's picture
Peter Farley on Jul 9, 2021

Tired old talking points, which made some sense when economies of scale made sense for large thermal plants.

Just as trains are far cheaper than cars and old central landline telephone systems favoured ATT, new generating and storage technologies have made the old paradign obsolete.

To build a wind/solar/battery farm which can supply an average of 650 MW would use about 500,000 tonnes of material. 50-70% more material than to build a 1,000 MW coal plant and associated mine and waste infrastructure.  which in the past would also have averaged about 650 MW. (The current US coal fleet averages about 55% capacity factor).

However the coal mine needs about 2.5m tons of coal and 17 million tonnes of water and generates 300,000 to 800,000 tons of sludge/solid waste every year so again renewables come out on top

Michael Keller's picture
Michael Keller on Jul 9, 2021

Tired old distortions.

Energy (megawatt-hours), not power (megawatts) is what counts.

Creating a lot of power for a short time is generally not helpful. Therein lies a problem with intermittent and unreliable green energy. 

Your 650 MW example needs to be roughly tripled to meet the sustained energy output of a conventional power plant.

I am not saying the green resources are unhelpful, but there are practical limitations that needs to be considered.

Batteries too have practical limitations, as they cannot be run up and down from full output to zero and back to full power frequently because the lifetime is seriously degraded. Generally, cycling to around 50% is OK and that need to be considered if you are attempting to meet peak demands that show up routinely.

Peter Farley's picture
Peter Farley on Jul 11, 2021

I thought I was simplifying it for you. If the average annual output of both systems is 650MW, the annual output in MWh will be the same. You are correct that to generate an average of 650 MW over a year with the same availability of a coal plant, you will need about 850MW each of wind and solar and 600 MW/2,500 MWh of batteries. However at current costs that will be about $2.5bn. It will be very difficult to build a 1,000 MW coal plant and associated mine, water and waste infrastructure for US$2.5bn

As for variability In fact if you look at the distribution of combined power output from widespread renewables it varies less than the output from gas plants. It is turue that coal plants get uncomfortable with cycling more than 50% but gas and hydro plants handle that easily. Peak to minimum demand on the grid varies by more than 50% anyway so all power systems have to cycle. Nuclear systems only cycle less because they let gas and hydro do all the hard work.

I do agree that batteries have to be sized for extreme cases therefore on most days a cycle will be between 5 and 75% of capacity, just like gas peakers, which in the US have less than 5% Capacity factor. The big advantage of batteries is that they can provide frequency and voltage regulation without consuming fuel so they make money every minute of the day, whereas the gas plant can only make money when it is running. Also a 100 MW battery can offer 100 MW into some sort of fast frequency response or regulation market (< 6secs response) whereas a 100 MW gas turbine can only offer about +/- 5MW in 6 secs so the battery makes more money per hour from regulation even when the gas turbine is running. In South Australia a single 100 MW battery in a 3,400 MW system, reduced grid services costs by about 70% and captured about 80% of the market from the 3,100 MW of gas plants on the grid.

Batteries will actually reduce cycling for gas, in fact in some markets batteries are being used for exactly that purpose, allowing gas plants to operate at higher power before and after peaks to charge/recharge the battery while operating with the battery at peak time. The batteries also eliminate 30 minute run times for the gas which is inefficient and stressful

Michael Keller's picture
Michael Keller on Jul 16, 2021

A battery provides DC energy that requires inverters to produce AC energy. Using DC to cover AC frequency disruptions is not that straightforward, particularly when considering the sheer size of an electrical grid. The momentum of large rotating turbine/generators is a superior method to help maintain the stability of the grid.

Considering that grids are typically operating at 350,000 volts (typical US average) and thousands of amps, batteries are of doubtful help in dealing with grid voltage disturbances.

Green energy ( which is created as DC energy) exacerbates grid stability issues.

Michael Keller's picture
Michael Keller on Jul 5, 2021

Energy (megawatt-hours) not power (megawatts) is the most relevant consideration, followed by matching energy production with energy need.

Unclear how or who is the arbiter of accountability for sustainability. The free market is the most effective mechanism, with the government the most inefficient and most corrupt mechanism.

Peter Farley's picture
Peter Farley on Jul 9, 2021

Let's have a free market for drugs, policing, defence, roads. Works really well I am sure

Peter Farley's picture
Peter Farley on Jul 11, 2021

Your last two points are correct.

Total land use for coal in particular is higher than renewables and it can be argued that the same is true for gas and even nuclear.
The second point about distributed resources is also correct.

If the US fully utilised rooftops and disturbed lands, floating solar, offshore and and other dual use opportunities, energy infrastructure would use considerably less land than it does now. It is even arguable that depending on ultimate energy efficiency progress and excess on site generation capacity, that many existing long distance transmission lines could be dismantled

 

Matt Chester's picture
Matt Chester on Jul 12, 2021

I agree with you here-- though there is the complication of more renewables in these more distributed locations likely needing a greater build out of transmission infrastructure-- whether that would outweigh the less needed long distance lines you mention is a question that warrants deep study

Bob Meinetz's picture
Bob Meinetz on Jun 28, 2021

"By 2050, the International Renewable Energy Agency projects that up to 78 million metric tons of solar panels will have reached the end of their life, and that the world will be generating about 6 million metric tons of new solar e-waste annually. While the latter number is a small fraction of the total e-waste humanity produces each year, standard electronics recycling methods don’t cut it for solar panels."

Solar Panels are Starting to Die, Leaving Behind Their Toxic Trash

Alan Rozich's picture
Alan Rozich on Jun 29, 2021

Bob, I appreciate your very cogent point. That's a real problem that also probably applies to EVs also. Thanks for your input.

Peter Farley's picture
Peter Farley on Jul 9, 2021

1. Solar reccycling is already starting to happen.

2. Even if there was no recycling by 2050 solar will be supplying about 10,000 TWh per year. 10,000 TWh of coal production would be producing 2 billion tonnes of toxic waste. Which do you think is a bigger problem

Mark Howitt's picture
Mark Howitt on Jul 6, 2021

Wind can be put offshore (best) where it helps fisheries rather than hindering them, by providing spawning grounds and nurseries; even onshore takes little footprint as farming, roads and buildings (especially businesses) can be put in between them. Solar can and should be put on rooftops: factories, schools, hospitals, convention centers, stations, shopping malls etc. for large-scale.

The real inconvenient truth about renewables is that they require a tripling of the grid, plus procurement and connection of balancing and stability services. However this is avoided if built with large-scale long-duration electricity storage: see https://www.storelectric.com/saving-billions-on-grid-upgrades/

Matt Chester's picture
Matt Chester on Jul 6, 2021

Interesting points, Mark. Thanks for sharing.

On the need for added transmission-- isn't that going to be needed at some point anyway with ever-growing demand? Obviously renewables make that need even greater, but if the new T&D that will be needed anyway can utilize tech like HVDC might it be able to handle that renewable capacity and solve a host of other issues as well? 

Mark Howitt's picture
Mark Howitt on Jul 8, 2021

Yes, as demand grows, so the grid will have to grow. But whatever size the grid has to be to satisfy demand, it has to be at least 3x that size if large-scale renewables are NOT connected to the grid through large-scale, long-duration, inertial storage of suitable size.

Mark Howitt's picture
Mark Howitt on Jul 8, 2021

HVDC is not the answer either. Its proper role is to keep prices reasonable, not to provide back-up power. Apart from being just plain wrong (e.g. the kalte Dunkelflaute), the EU's insistence that if the wind isn't blowing in parts of the continent then it is in others, and we just need to send the surplus from the latter to the former, is just plain impractical: each corner of Europe would have to build enough capacity to power every other corner of Europe, resulting in maybe a 10x over-build, and the entire continent would have to be criss-crossed by ~300-1000 GW interconnectors in each direction, resembling a the UK flag including the flag's outline. See https://www.storelectric.com/interconnectors-and-imports/

Peter Farley's picture
Peter Farley on Jul 15, 2021

The kalte Dunkelflaute is a serious issue but its influence is vastly overstated. In Germany alone the worst renewable week last winter, (a very low wind year) was 25% of supply. Average renewable supply for the year was 50% so if Germany increases renewable capacity by 150% which is roughly what it is planning to do, the worst week will require backup/imports of 25% of demand. Inverting this calculation shows that if Germany had storage equal to 7*0.25 = 1.75 days total demand it would not need imports. However by the end of next year it will have connections of roughly 15 GW to other markets, which they already use for imports but mainly exports so even a days storage will probably be more than adequate

However even this is overstating the case, because new wind turbines, particularly offshore, can generate much more power in light breezes than typical early generation machines that currently form the bulk of the German fleet. Similarly bifacial panels in snowy fields, east west panels on roofs etc mean that the gap between winter and summer renewable output is declining. Having excess wind and solar on windy sunny days will also mean that hydro output can be reduced further on those days and increased during the Dunkelflaute. 

In summary it is highly likely that a future European grid will not transmit much more energy per year than it does currently 

Michael Keller's picture
Michael Keller on Jul 7, 2021

Not real helpful for trawlers and boats with a lot of gear over the side as you have put obstacles in their way. Navigational issues in heavy weather and at night will become a major problem. I suspect the end result will be effectively creating no commercial fishing zones.

Mark Howitt's picture
Mark Howitt on Jul 8, 2021

Creating marine parks is well recognised as the best way to increase fish stocks outside those parks, and make fishing sustainable in the long term. Therefore, by closing wind farms to trawlers, fishing is actually helped.

Michael Keller's picture
Michael Keller on Jul 9, 2021

Depends whether or not you make your living fishing. Marine sanctuaries are generally created by legislation, not dictates from the unelected bureaucracy.

Peter Farley's picture
Peter Farley on Jul 11, 2021

Marine parks have been shown around the world to increase available fish stocks by avoiding the"tragedy of the Commons", a well known talking point for libertarians.

Peter Farley's picture
Peter Farley on Jul 9, 2021

The Store-electric piece contains some very interesting information but it is also an advertisement for their technology and therefore needs to be taken with a significant grain of salt.

In Australia where long distance energy flows are publicly available, energy transfer on interstate HV lines has fallen 30% since 2015 as wind and solar have grown from 7.6% to 21%.

Most HV grids are very lightly used because they are sized for peak demand + redundancy so flexible demand and storage near the load can be just as valuable as storage near generators. Both however will increase the utilisation of transmission grids. So will there will definitely be some new lines there is no real evidence that there will be a major expansion of the grid.

In future between 30 and 50% of demand will be sourced at or near the load whether it is rooftop solar, waste to energy generators, biodigesters in farms and food processing works or wind generators adjacent to or on large industrial sites or in building fuel cells

Michael Keller's picture
Michael Keller on Jul 9, 2021

Complete nonsense. You are seriously out of touch with practical technical and economic reality. 
By any chance, do you live in California?

Peter Farley's picture
Peter Farley on Jul 11, 2021

No. I don't live in California or even the US. However I would be grateful if you can demonstrate any factual errors in my comment. Otherwise read and learn, it will be good for you

Bob Meinetz's picture
Bob Meinetz on Jul 15, 2021

"However I would be grateful if you can demonstrate any factual errors in my comment."

Peter, for some reason it's consistently necessary to remind renewables supporters of this maxim, but it's an author's job to support his opinions with facts - and references.

The idea operators of any "large industrial site" would consider making their business dependent on an intermittent, unreliable source of energy - much less a complicated combination of several of them - is one of the more outlandish fantasies of renewable supporters, among many. You might visit a factory and learn, it would be good for you (there are many reasons why no one has adopted your strategy).

Peter Farley's picture
Peter Farley on Jul 15, 2021

It is true that not all the energy for any site will be generated by internal resources, just as none of them rely exclusively on the local nuclear gas or coal plant, because those plants still need maintenance. That is why we have a grid with many thousands of generators, and a combination of technologies, hydro, gas, diesel, coal, geothermal and nuclear.

There were also switchable transmission circuits, controllable loads and storage capacity.

It will be the same in future but with millions of generators, many more controllable loads and a bit more storage. The difference is that most of the generation will be local on roofs, small waste to heat generators, bottoming cycle waste heat power generation, small wind farms in rail yards, in fields near factories, small towns and in ports.

 For your edification I have run factories for many years and more and more of my younger colleagues still running factories are getting 25-100% of their electricity from rooftop solar and/or renewable energy aggregators who combine wind, solar, hydro and landfill gas to provide 100% renewables. Even Google and Microsoft with their huge, always on data centres are moving in that direction.

You are not quite correct that no-one has adopted my strategy. It is true that very few have implemented it yet but many have a near term goal to do so including large companies like Ford, Volkswagen, Microsoft, Google etc.

There were many reasons some years ago why it was not feasible and it is not feasible today for some sectors of the economy, but there are many energy users today who can convert to 100% renewable. As costs continue to fall and the economic consequences of fossil fuel use become more internalised into their price by 2030 it will only be sunk costs and institutional inertia that keeps fossil fuels and nuclear viable in all but about 10-15% of current energy uses

Mark Howitt's picture
Mark Howitt on Jul 16, 2021

Peter, my piece was about the need for large-scale long-duration inertial electricity storage on the grid and, specifically, of suitable scale and duration between renewable generation and the grid. None of that is advertising; it's all neutral stuff that (for advertising purposes) uses the Storelectric name instead of saying generic storage because ours, unlike many technologies (e.g. flow or solid batteries) don't do the job.

There are other storage technologies that will do the job, but they are both more expensive and demonstrably inferior to ours. That's the bald fact. It also happens to advertise us. It is wrong to dismiss facts just because the facts point in a direction in which you may not wish to go.

Peter Farley's picture
Peter Farley on Jul 21, 2021

I apologise if I interpreted your comment as advertising. The question of long duration storage is an interesting one. If you look at the OpenNEM application in Australia or the DRAX Electric Insights in the UK or Fraunhoffer Energy Charts in Germany, you will find that the variation between max and min renewable days is declining as geogrphic diversity and low wind/solar performance improves. Seasonal variation is also declining.

However even if you double renewable output in Germany, triple it in the UK and quadruple it in Australia there are still hours when some sort of backup will need to supply 65-85% of the energy. There are days when half the energy would come from backup and weeks where there is one third.

So the question is how do we handle that backup. The pragmatic solution is to combine some storage, say enough to get you through the worst day, with existing CC gas. Start the gas up before a forecast lull in renewables to make sure all the storages are full and then run the gas at about the minimum forecast daily demand throughout the lull. Then use the remaining renewables and the storage as the swing producers/consumers.

I did an exercise like that for South Australia which has no hydro and no biomass or geothermal and is running on 60% wind and solar. It turned out that with storage equal to 60% of annual peak demand for 4 hours, gas would only supply 1.5% of annual demand. Now that will differ from region to region but given that SA is very unusual in having no dispatchable renewables, it is unlikely to be on the low side. 

The other option is to do what we always did and have excess generation capacity. In earlier times most regional grids could supply 50% more energy per year than they actually did. Say a 200TWh per year grid usually had capacity at high but realistic capacity factors to supply 300 TWh, That also meant that nameplate capacity was 30-50% higher than peak demand. On a renewable grid, to supply 50% more than annual demand, nameplate capacity would typically be 2.5-3.5 times peak demand. If you do that and follow through day by day in say Germany or the UK, you will find that even the worst 3 day period has almost enough to get by with about half a days storage.

There are all sorts of combinations of course but until we are in excess of 90% renewables, in most places more than the equivalent of 4 hours storage at 50% of system annual peak demand is unlikely to be utilised.      

 

Michael Palmer's picture
Michael Palmer on Jul 6, 2021

Gives pause for thought. Offshore wind farms and hydrokinetic systems (rivers and ocean currents) such as that being developed by Waterotor Energy Technologies (www.waterotor.com) do not use any arable land. Presumably, they would be an alternative to land-based wind and solar.

Alan Rozich's picture
Alan Rozich on Jul 7, 2021

Agreed.

Michael Keller's picture
Michael Keller on Jul 9, 2021

River run and tidal energy generation obviously impact the environment and marine life. From a practical standpoint, the machines are in very tough environments that are really difficult to reliably overcome. Those two items are major reasons these applications are rare.

Gene Nelson's picture
Gene Nelson on Jul 6, 2021

Thank you for your article, Alan. However, your calculations regarding a nuclear power plant's power density are orders of magnitude too small. The important factor is not nuclear power plant capacity, typically denominated in gigawatts, but power production. For a large nuclear power plant such as the 2,280 MW Diablo Canyon Power Plant, annual power production is 18 terawatt-hours.  That is  18 billion kilowatt-hours per year.  For ease of calculation, assume Diablo Canyon's footprint is one square mile. (The plant footprint is less.)  That is 2.59 E6 square meters. Diablo Canyon annual power production  is 18 E9 kWh/year.  Thus, a lower bound to Diablo Canyon's power density is 6.409 E3 kWh per square meter per year. Diablo Canyon typically has a capacity factor greater than 90%. This meaningful value for annual power production is far greater than the best-case value of 386 shown on your graph for nuclear power. 

 

One problem with solar and wind is the tremendous amount of natural-gas-fired generation required to integrate these very intermittent power sources into the grid.  In California, CGNP established the capacity factor , or percentage on time for solar or wind is only about 1/5 of the time for the half year ending on January 31, 2017. See: https://tinyurl.com/Wind-And-Solar-Scam  The natural gas fired generation is dispatched intermittently and inefficiently, calling into question the claimed environmental benefits of solar and wind  The actual solar or wind production in your "Area Power Densities for various sources" should be corrected for a capacity factor of about 1/5. 

 

There is a big push for California offshore wind even though there are less than 10 offshore wind turbines installed in the entire United States. Wind is caused by pressure gradients which are mostly related to temperature gradients. The pressure gradient can be increased by land geography such as the San Grigornio Pass or Altamont Pass.   No such funneling exists for offshore wind locations. The temperature gradient is greatest at or near the shoreline.  You can see this for yourself by observing that most National Weather Service  small craft advisories for California only extend to 10 miles out. 

 

Recall also that wind turbines are bird-killing machines. The blade tips of a large wind turbine move at over 100 miles per hour. I recall a wind turbine salesman telling me with a straight face at a BOEM hearing in Sacramento a few years ago that sea birds are more intelligent than land birds. They know to avoid the wind turbines. No. They are killed by these machines in the same way that land birds are killed. However, the bird and bat carcasses do not accumulate at the base of the wind turbine. They float away so they cannot be counted.

Alan Rozich's picture
Alan Rozich on Jul 7, 2021

My calculations are based on the data listed in cited references which are provided.

Gene Nelson's picture
Gene Nelson on Jul 8, 2021

Please see Michael Keller's comment below regarding the appropriate use of the product of power and time, also known as useful work.

Peter Farley's picture
Peter Farley on Jul 15, 2021

Your calculations are a complete misinterpretation of the data in the references. You have left out 90% of the area used by the thermal energy cycle and ommitted the dual use nature of most wind and solar generation.

Michael Keller's picture
Michael Keller on Jul 7, 2021

Power is megawatts. Energy is megawatt-hours. Energy density is typically measured in megawatt-hours divided by some form of volume. Power density would follow the same pattern.

 A useful comparison is the energy divided by the land area of the production facility. Best would typically be a combined-cycle natural gas plant occupying a few acres. Nuclear would be relatively good, with land needs of a few hundred acres but with massive output and high capacity factor. Renewable would be a dismal last place because of the large land needs and poor capacity factors. Gets even worse if the measure is an even-handed comparison based on the equivalent energy output of a large power plant.

Peter Farley's picture
Peter Farley on Jul 11, 2021

Your comment would be true if you leave out the land needed for gas wells, treatment plants sand mines for fracking, security perimiters around the power plant etc etc. 

Here is a simple example for you. A 500 MW CC gas plant operating at US average 55% capacity factor typically has a fenced area of 50 acres+. Over its life it requires between 100 and 300 gas wells each of which requires an average of half an acre of pad area, access tracks etc. Then they are waste water ponds, gas compressor stations, pipeline ROW and gas treatment plants. In total about 150-300 acres. To produce the same amount of annual energy requires 160 4 MW class wind turbines and a 500MW battery system. The turbines require the same area as the gas wells and the battery about the same area as the gas treatment plant. In other words about 30-50% less area than the gas plant and associtaed infrastructure.

Michael Keller's picture
Michael Keller on Jul 16, 2021

A natural gas power plant needs a couple of acres of land.
Gas power plants can easily operate at +90% capacity factors. As the machines can largely economically tolerate dropping load, they are used to cover dismally unreliable green energy. The price of energy from a gas plant operating at 50% capacity is about 30% higher than operating at 90% capacity (gas price around $3.5/MMBTU). That is roughly 40% cheaper than wind energy without any subsidies and maybe 15% cheaper with wind energy subsidies in play. 

To match a 1000 mW power plant operating at 90% capacity, wind turbines need about 260,000 uninhabited acres (in windy region of US Midwest) The 1000 mW gas plant needs about 15 acres, with no particular restrictions.

FYI a solar plant in the desert would need about 35,000 acres to match the 1000 mW plant operating at a 90% capacity factor.

Gas tends to be a byproduct of horizontal drilling for oil. Apples-to-apples land need comparisons with wind turbines are accordingly difficult, as the oil is the primary driver for the drilling and gathering equipment.

Source: Hybrid Nuclear Energy Systems, Academic Press.
 

Peter Farley's picture
Peter Farley on Jul 22, 2021

1. Go to Google maps and find a decent size gas plant that occupies a couple of acres, you won't find any.

2. Search the EIA database and find a gas plant that averages 90% CF. There aren't any.

Wind plants are entering long term contracts in the US at around US$24/MWh. Add back the effect of tax credits over the life of the project that is about $35-40.   A CC gas plant running at the US average 56% will have depreciation and finance of $22/MWh, operation and maintenance of $15-20/MWh and fuel of $25/MWh. I.e fully absorned costs of at least $62/MWh. So your costsings are out by a factor of two, even after ignoring the pollution from the gas plants.

As for you uninhabited acres, I didn't realise Scotland with 6,000 turbines or Germany with 30,000 or Denmark with 2,500 were uninhabited. 6,000 wind turbines in Scotland is equivalent to 600,000 in the US.

NREL found that 14% of US roofs can supply 30% of US electricity demand with on land use at all

Peter Farley's picture
Peter Farley on Jul 15, 2021

It is clear from Germany, the UK and Australia that natural gas output has not increased as renewables have increased. In fact in all three cases gas output has fallen

Andrew Blakers's picture
Andrew Blakers on Jul 6, 2021

A simple calculation shows that land is a non-issue for solar panels in the USA.

The USA produces 4 Terawatt-hours of electricity annually. Divided by its population, this amounts to 12 Megawatt-hours (MWh) per person per year.

A kilowatt-rated (1 kW) solar panel occupies an area of 5 square meters and produces about 1.5 MWh per person per year, averaged over the USA, Thus, each person needs about 8 kW of panel to provide their share of electricity, covering an area of 40 m2 (13,000 km2 for the whole country). This is far smaller than the area devoted to cities, agriculture, artificial reservoirs and many other activities. In fact, it is about 0.13% of the US land mass.

The area of rooftop is enough to accommodate all the solar panels the USA needs. Solar panels are also located in arid regions, in combination with pasture and cropping (agrivoltaics), floating, and in many other locations.

Solar panel waste is a non-issue once panel recycling reaches maturity. The lifetime of a solar panel is about 30 years. Thus, about 1.4 m2 of panel per person reaches the end of its life each year. The aluminum frame is recycled, Small amounts of conductive metals are recovered. A tiny mass of silicon is discarded (silicon is non-toxic, and is very common in the earth's crust). The largest component is the cover glass, which will add one quarter to the already-existing glass-waste stream from buildings and cars.

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