Are we heading for an over-reliance on wind? With wind generation costs continuing to drop dramatically, Schalk Cloete takes a data-driven look at the obstacles wind will face as its contribution to the global energy mix (a little over 2% today) keeps rising. In the main, it is grid integration and public opposition to very visible turbines – and they are related. Putting turbines out of sight and offshore will increase transmission costs. And the system complexity of integrating new power sources into the grid will add costs that early-stage wind (and solar) have not yet faced. Cloete has modelled different technology mixes – including nuclear, CCS and hydrogen – and assigned a range of different possible costs to uncover what the energy mix and total system cost scenarios can look like. Depending on the fortunes of each technology, the plateau for wind may come sooner than its proponents believe. Cloete says wind’s weakness – that its remote location will increase its transmission costs – should be more acknowledged. He also urges policy makers to be tech neutral in their planning, so that the potential of nuclear and carbon capture is acknowledged too.
Levelised costs of electricity often dominate the energy and climate debate. Green advocates like to believe that if we only invest enough in wind and solar, the resulting cost reductions will soon put an end to fossil fuels. While this is already a severely oversimplified viewpoint, a single-minded focus on cost makes such simplistic analyses even less useful.
This article will elaborate on this point by example of two clean energy technologies that face very different non-economic barriers: nuclear and wind.
Similarities with the Nuclear stagnation
When a technology is new and exciting, people only see the positives. It is only when it reaches meaningful market shares that undesired impacts are felt, and public opinion turns negative.
In the case of nuclear, the global expansion was handicapped by the Chernobyl disaster in 1986, and the nascent developing world expansion was interrupted by Fukushima in 2011. As shown in Figure 1, Chernobyl happened when nuclear reached about 5% of global energy supply. Today, we are at 4.2%.
Burning carbon kills far more people than Nuclear does
Deaths from Chernobyl are estimated somewhere between 4,000 and 60,000, with 574 for Fukushima. For perspective, it is estimated that one future premature death results from every 300 to 3,000 tons of burnt carbon or 1,100 to 11,000 tons of CO2 released into the atmosphere. Hence, if we assume that the 93,000 TWh of nuclear power generated to date displaced coal at 0.8 ton-CO2/MWh, the 74 billion tons of CO2 avoided by nuclear has already saved 7-70 million lives, not counting the additional impact of avoided air pollution.
Clearly, the public backlash against nuclear was not rational from a big-picture view. But that does not matter. The effects of public resistance are real, whether it is rational or not.
A Wind stagnation?
As Figure 1 shows, wind is currently expanding at about half the pace of nuclear in the seventies and eighties. Although wind does not face risks from black swan events like nuclear, it faces its own brand of public resistance, both to the turbines themselves and the large network expansions required to integrate higher wind shares.
As our societies become more advanced, we increasingly demand an invisible energy system. Over here in Norway, the usually reserved population is reacting furiously to onshore wind expansion plans. Turbines dotting the pristine Norwegian landscape are simply unimaginable to this wealthy society, the origin of its wealth notwithstanding. In Germany, resistance to turbines and grid expansions has almost brought onshore wind expansion to a halt at levels around 7% of total energy demand.
That is wind’s greatest challenge: it is the most visible energy technology we have. As wind continues to expand and turbines grow ever larger, its visibility will only grow while society’s tolerance for highly visible energy technologies continues to decline. Advanced societies also become increasingly concerned with nature preservation, leading to additional hurdles related to bird protection.
Offshore wind can help, but it will need to be built far from shore to be sufficiently invisible, making it more costly. It also faces further economic challenges from wake effects that strongly reduce output as total installed capacity increases. In addition, offshore wind requires large grid expansions to serve inland regions. Making these expansions invisible (underground cables) is very expensive.
Like nuclear, this resistance is not rational from a big-picture viewpoint. Surely, seeing the occasional wind turbine in the wild is worth the climate benefits. But again, the rationality of this resistance does not matter. What matters is the effect it has on clean technology deployment.
The undervalued issue of System Complexity
Megaprojects that involve many interconnected technical, economic, political, and social challenges are extremely difficult to execute on time and within budget. Nuclear offers a prime example with many stories of budgets and timelines that were widely missed, increasingly stringent safety regulations being only one reason.
In comparison, the modular construction and installation of a wind turbine is child’s play. For decades, the simple and standardised construction and installation of wind and solar have been a big driver behind their impressive growth and falling costs.
But this will not last. Higher wind market shares require vast grid expansions (often into neighbouring countries) and lots of integration with other sectors that previously operated independently. In the longer-term, this includes a large hydrogen transport, storage, and end-use sector that needs to be built from scratch. Executing this enormous integrated project in a shifting policy-technology landscape with impossibly tight climate timelines and increasing public resistance can easily surpass the scale and complexity of nuclear projects.
As the nuclear example shows, sub-optimal execution is to be expected in such a large, complex, and multifaceted project, inflating overall system costs and slowing the energy transition.
These effects are quantified using a published energy systems model below.
The energy systems model discussed in a previous article is used in this study to illustrate the large effects of cost inflation caused by the range of techno-socio-economic factors discussed above. The model is loosely based on Germany and is designed to optimise investment and hourly dispatch of a range of technologies, including:
- Eleven different electricity generators: onshore wind, solar PV, nuclear, pulverised coal and natural gas combined cycle plants with and without CCS, open cycle gas turbine peaker plants, hydrogen combined and open cycle plants, and the novel gas switching reforming (GSR) concept
- Lithium-ion batteries for electricity storage
- Three clean hydrogen generators: GSR, steam methane reforming (SMR) with CCS, and polymer electrolyte membrane (PEM) electrolysis
- Two hydrogen storage technologies: cheap salt caverns with slow charge/discharge rates and locational constraints and more expensive storage tanks without such limits and constraints
- Hydrogen can also be imported in the form of green ammonia that is reconverted to hydrogen in reconversion plants included in the model
In addition, transmission costs for electricity and hydrogen are included in the model. In this assessment, the transmission costs for wind (set to €300/kW in the base case) will be increased to assess the effects of cost inflation caused by factors such as:
- The need to build turbines in more isolated sites or far offshore to satisfy local stakeholders
- Avoiding public resistance to grid expansions via expensive underground transmission lines
- Having to resort to sites with lower quality wind resources
- Paying fees to local communities to allow the construction of turbines closer to demand
- A sub-optimal buildout of the complex and highly interdependent systems required to integrate high shares of wind
In addition, the effect of cost inflation of nuclear power will be investigated by changing nuclear plant capital costs between €2,000/kW and €8,000/kW. The lower bound represents well-executed nuclear projects in more welcoming environments like China and South Korea. The upper bound accounts for the vast complexity and inefficiency of constructing nuclear plants in the West.
These variations are investigated in scenarios with and without CCS allowed into the system using a high CO2 price of €200/ton to incentivise low-carbon technologies.
In all cases, total annual electricity demand is set to an hourly fluctuating profile for Germany in 2012, requiring a total of 515 TWh of production per year. In addition, a flat demand for hydrogen of 400 TWh/year is included. This is equivalent to about a quarter of German non-power oil & gas consumption, implying that much more clean energy will be needed for net-zero emissions.
Results: Energy Mix
Electricity production and consumption from the optimal technology mixes for different cases are shown in Figure 2. Starting from the left, we see that higher wind transmission costs strongly reduce the deployment of wind power in the optimal energy mix. With the base costs (€300/kW), almost all required hydrogen is made locally using electrolysis. However, this scenario requires 250 GW of installed wind capacity – quadruple the current installed base in Germany where public resistance is already having a large negative impact on wind expansion plans.
When wind transmission costs are tripled, almost all hydrogen needs to be imported as green ammonia. Quadrupling of costs to €1,200/kW (about the same as the turbine costs) brings substantially more unabated NGCC power into the generation mix despite the high CO2 price of €200/ton. Solar power is quite cheap, but its role remains limited due to the large seasonal variation and mismatch with the seasonal electricity demand profile.
Allowance of nuclear into the system creates a 100% nuclear system when nuclear projects are perfectly executed (€2,000/kW). Even at a cost of €6,000/kW (triple the technical potential), nuclear still dominates. However, at €8,000/kW, costs become excessive, and the optimal solution is the same as the base case in the scenario without any nuclear.
When CCS is allowed into the system, the GSR technology starts playing a large role. Electricity demand is also much lower because all hydrogen is generated using natural gas reforming that only consumes a small amount of electricity using the GSR technology. When grid costs are doubled, wind is pushed out of the optimal technology mix.
In a scenario with both nuclear and CCS allowed, nuclear remains responsible for essentially all the power production up to €4,000/kW plant costs. However, GSR is still responsible for generating most of the hydrogen. When nuclear costs are inflated to €6,000/kW, nuclear is pushed out of the system, and the optimal mix reverts to the base case in the scenario without availability of nuclear power.
Results: Total System Costs
The minimised annual system cost of each case is shown in Figure 3. For the scenario without nuclear or CCS, the base case shows that direct costs of renewables account for only about 40% of total system costs, even though they supply 83% of total energy, illustrating the high system costs of integrating such high shares of variable renewables and generating a large quantity of green hydrogen. When grid costs are increased, more hydrogen is imported in the form of green ammonia (included in “Other” costs). The system-scale levelised cost of energy is high in this scenario, ranging from 120-133 €/MWh.
The ideal nuclear case (€2000/kW) reduces costs by more than half. For perspective, the difference between the cases with and without €2000/kW nuclear is about 2% of German GDP – twice the GDP growth rate since the turn of the century. However, total system costs rise steeply as nuclear plant costs increase. The system with €6,000/kW nuclear is only about 10% cheaper than the case without nuclear.
The addition of CCS reduces costs substantially when nuclear is not allowed. It also prevents any significant cost increases when wind is rendered uneconomic by rising grid costs. However, a system that is so dependent on natural gas is undesirable, and substantially higher shares of renewables and nuclear would be preferred from the perspective of energy security and long-term sustainability.
When combined with nuclear, CCS can slightly reduce system costs by taking care of hydrogen production via reforming. The benefit of this blue hydrogen becomes larger when nuclear costs increase from 2,000 to 4,000 €/kW, and CCS also takes over in the power sector when nuclear plants cost €6,000/kW.
Results: Other System Costs
More insights about the other (not energy supply) system costs are given in Figure 4. The transmission cost that is increased in the wind cases is the “VRE transmission” component. As grid costs are increased, the system limits this cost by importing more hydrogen in the form of green ammonia instead of generating it from local wind power. Clearly, the cost of these green ammonia imports grows very large in cases with high wind grid costs.
The simplified energy system facilitated by nuclear is also clearly visible. Electrolyser costs are lower due to the possibility to operate electrolysers at maximum capacity factor from the steady supply of nuclear power, and no battery storage is needed. Grid costs are also lower because nuclear plants can be constructed where energy demand is highest. Hydrogen transmission and storage costs also reduce because hydrogen is produced at steady state. The cases with CCS simplify the system further, mainly because no electrolysers are needed and the electricity grid can be smaller.
An over-reliance on wind can be just as challenging as an over-reliance on nuclear. The socio-political hurdles facing wind and nuclear are very different, but both are highly significant. As wind continues to expand to the level where nuclear peaked (it is currently about one-third of the way there), public resistance and system complexity will continue to mount, causing substantial headwinds.
Ultimately, wind will follow the same S-curve deployment pattern of all other energy technologies, but the plateau may well come earlier than proponents believe. For this reason, nuclear and CCS should be encouraged for parallel deployment, especially in regions with limited and/or seasonal solar availability. The ability to construct these technologies where energy is demanded and dispatch them according to demand results in a much simpler energy system.
An all-of-the-above approach to the energy transition guided by technology-neutral policies remains the rational choice. Each technology class has its limits and weaknesses, and we need a balanced mix to allow each technology to do what it does best. Wind and solar are great at moderate deployment levels, but other clean technologies will be needed to reach net-zero. Nuclear is one of these options, while CCS has an important role to play in system balancing and clean fuel provision.
The global energy transition is a clean energy team effort. All the players deserve our support.
Schalk Cloete is a Research Scientist at Sintef
I found the comment about well executed projects in more welcoming environments like China interesting for two reasons. It implies that the general population has been involved in deciding to build nuclear plants which is questionable. It also begs the question why China is therefore planning more coal fired power stations than the rest of the world combined.
I must admit I don’t know enough about Chinese politics, but I doubt that much of the general population needs to be involved in a decision to build nuclear plants. The absence of large-scale resistance is more important than the presence of active support.
Indeed, China may be planning most of the world’s coal plants, but they also account for about half of the planned and proposed nuclear reactor pipeline.
Peter Farley says
Well executed nuclear projects at E2,000/kW are a myth. There aren’t any. One might as well talk about solar at E350/kW or wind at E550/kW and batteries at E70/KWh. In fact all of these numbers are likely to be achieved long before nuclear falls to E2,000/kW. In the three years to the end of 2020 the most active nuclear country China commissioned 14 GW of nuclear power. Over the same time it commissioned 118 GW of wind and 124 GW of solar. Nuclear ouput increased by 118 TWh, solar by 145 TWh and wind by 163 TWh. Wind and solar costs are falling faster than nuclear, hybrid plants are becoming easier to integrate and distributed generation is becoming more and more economic vs centralised plants of any type, so the renewable/nuclear gap is widening not narrowing
Hugh Grace says
Really interesting. You might like to know of ARDAU USC technology that uses any carbon waste, places it in a reactor as a slurry, initiates an exothermic reaction; increased pressures (E.G. 300 bar) and temperatures (e.g.700 degrees) to Super critical (SC) levels; SC fluid released to turbo expander to generate electricity, water and hydrogen. Process efficiency 80% plus. No emissions as enclosed system. Process gases (CO, CO2, H2) produced in pure form for storage , sale or reuse. Up to 50 MWh can be placed in a mobile shipping container. Ramp up in minutes. 24/7 core decentralised generation.
Jon Stakes says
“As Figure 1 shows, wind is currently expanding at about half the pace of nuclear in the seventies and eighties.” – This comment seems very misleading. Energy consumption was about 2,0-2,5 times lower by comparison. It would seem more reasonable to compare TWh additions per year.
I my opinion, it is fair to compare on a relative basis, and the direct reference to the graph leaves no uncertainty regarding the meaning of the quoted statement. Energy consumption may have been 2-2.5x less during the nuclear expansion, but global productive capacity (out ability to build new infrastructure like nuclear and wind) was smaller by the same ratio. In fact, if you use PPP adjustments (probably more accurate), our productive capacity today is about 5x what it was during the nuclear expansion, making that clean energy rollout all the more impressive.
Roger Arnold says
Interesting article. Hopefully it will at least provoke some rethinking of some of the issues that tend to render debates about clean energy so contentious. I sometimes feel like Gulliver in Lilliput, witnessing the civil war between the big endian and little endian factions. Thanks, Schalk, for injecting a bit of much-needed rationality.
It’s not a criticism, but something worth noting, that your results are strongly influenced by considerations of financial ROI and the assumed cost of capital. That’s appropriate, given that it’s how things currently work in our Western economic system. But I’m not willing to concede that that’s how it has to be or should always be.
In particular, if we’re talking about infrastructure what will deliver value far into the future, then we need ways to factor in intangible benefits in our investment decisions, even if the benefits don’t translate to a direct financial return to the investors. E.g: long distance power transmission lines. Putting them underground is vastly more expensive than stringing them between transmission towers, but it can still pay off in terms of aesthetics, resilience, and duration of service.
Another example is energy transport via hydrogen gas pipelines. For reasons I won’t go into, I’m not a huge fan of the hydrogen economy. However, one of the things seldom mentioned that it has going for it is the scaling properties of energy transport via gas pipeline. Transport capacity goes roughly as the cube of pipeline diameter. With a handful of 3 or 4-meter pipelines — heavily cross-linked to route around breaks and blockages — it would be feasible to transport hundreds of gigawatts of chemical potential energy from North Africa to all of Europe. The large diameter pipelines would serve double duty as transport and storage.
Hugh Grace says
Infrastructure costs are going to be vast for both electricity and H2. The more so if we are relying on wind which is already creating management problems. If it is possible to decentralise generation of both, as we believe it is, then these costs are not required and storage isn`t so much of a problem as bot will be available locally. But first we have to overcome our “horror” of carbon (and nuclear for that matter) and review just how it can be used “safely”. We know how to do this.
I am amused by the fact that we are looking to put power lines out of sight when we will have these monstrous 300m high windmills on skylines throughout the countryside. Can we please put them underground as well?
Roger Arnold says
Storage and transmission certainly do trade off. With more of one, you need less of the other. However both become awfully expensive if you’re trying to address long periods of dunkelflaute or seasonal variations in wind and solar without resort to weather-independent power resources.
I don’t like to see giant wind turbines dominating the landscape any more than I like to see high tension power lines marching across the countryside. But power lines can be run underground with no loss of functionality — and if done properly, big gains in reliability and maintenance of right-of-way. Wind turbines, alas, don’t work so well when they’re buried.
Perhaps underground wind turbines are the next big thing! 😀
More seriously though, the idea of the underground cables is to get wind energy from some godforsaken (and windy) place that no-one wants to visit to all the places where people do want to live and visit. The problem is just that such godforsaken (and windy) places are not so easily found in most of the energy-hungry regions of the world.
Hugh Grace says
Find a windy hillside location- put a tunnel through it and place a turbine in the middle. Should work – occasionally!
Energy hungry regions are also often where we have ended up dumping our manufacturing, waste and associated CO2. So they need a technology to handle the waste and then they have electricity, water and H2 generated locally. What more could they want!
Peter Farley says
You don’t need to find godforsaken places to put wind or solar. Germany today has 30,000 land based wind turbines. With a progressive replacement policy of one new for two old it can still more than double its onshore wind output over the next 20 years. With solar on half the unshaded roof and hardstand area it could generate about 20% of its current electrical demand from behind the meter solar. Combined with 30GW of offshore wind, biomass at about the current level and continuing energy efficiency Germany will be able to generate 80% of its energy needs from renewables within 150-200 km of the load centres. Depending on the rate of improvement of energy efficiency and the rate of decline of storage costs combined with controllable loads, overall flows on the HV transmission grid may actually decline
Germany has the third worst wind and solar resources per capita of the OECD so if Germany is well on the way to energy self sufficiency why won’t most other countries do the same.
Hugh Grace says
No, you don`t need to find “godforsaken” places but it is much more preferable than having them staring you in the face in the countryside. Nearly 300 m high – almost the height of an Eifel tower – sited in the most obvious places on the skyline. These are industrial machines sitting in the countryside and are monstrous to look at. We used to complain about pylons – what a joke. And flashing red lights at night. Why should anyone care as long as we save the world? Because I strongly believe we are resolving the wrong problem in the name of “decarbonisation” . And not only is the windmill industry aggressive in getting what it wants, but I think it is “dishonest” in its claims. Does it handle the waste problem or clean water. Does it provide decentralised electricity. It is based on old technology that engineers know full well is close to its limits – that`s why we have jet planes. It is unlikely ever to provide low cost electricity even though “Green hydrogen”, a marketing concept dreamt up by Siemens, is amusingly associated with “renewable” energy and is therefore six times the price. The LCAs are highly questionable. They are not a substitute for nuclear or other more advanced ways of handling waste that can give decentralised core generation. Pouring money into batteries and advanced Grid management may work for the UK and similar elite countries but doesn’t begin to address the issues faced by the vast numbers of people across the globe who are poor and want electricity and clean water to survive. Windmills and “decarbonisation” may salve the conscience of the elite countries (in which I include myself) but I believe that it is a fig leaf and that we are doing no more than misleading ourselves.
Brief comment on Germany. By closing down nuclear and coal (lignite) they have had to move to gas from their ever friendly neighbour Russia, which they need for core generation. They have vast forests which they adore – understandably – but cannot use these for generation because they are carbon. Nor their lignite nor waste nor contaminated waters like sewage – same problem. So you could ask them to cut down their forests to put up windmills and solar panels and dig up lithium instead. Or you could find a way to use any carbon with no emissions and generate low cost electricity and hydrogen…but what does that do to the mantra of “decarbonisation”? I would not want you to think there is a “hidden” agenda here. We have the technology to do just what has been described. I also – as will have become apparent – dislike windmills!
Peter Farley says
What a lovely combination of myths we have there.
There are no land based turbines in Germany anywhere near 300m high, very few are more than 200m. Germany will not have many more than 30,000 wind turbines but it already has 160,000+ power pylons
A 1000 MW coal plant uses 17,000 ML of clean water a year enough for a German city of 380,000 people. 1,800 MW of wind farms uses none. The coal power plant requires mining of about 6 million tonnes of coal and overburden every year, the wind farm none. The coal plant emits about 5 million tonnes of CO2 and hundreds of thousand os tonnes of NOx, SOx, and PM2.5 not all of which is captured in scrubbers. Those same scrubbers and coal ash combined produce between 500,000 and 2m tonnes of noxious slurry every year. The wind turbines none.
So yes the wind turbines do contribute significantly to reducing the waste and clean water problem.
In spite of your beliefs, according to the fossil fuel lobbying organisation, the International Energy Agency says solar and wind are the cheapest energy ever provided. wind+ solar + storage plants are contracting to supply energy for US$20 – 35/ MWh. No coal or gas plant can get anywhere near that so the logical thing for poor countries is to bypass large centralised thermal generators just like they bypassed fixed line telephony.
Furthermore in India and China where massive renewable investments are underway they are helping solve pollution and water crises as well. Last year India and China combined installed more wind and solar than Germany has in 30 years.
Germany only gets about 40% of its gas from Russia. In 2008 it generated 66 TWh from gas, last year 56 TWh, 11.6% of generation so where is this reliance on Russian gas you speak of.
As for forest German forest, timber and paper industries employ 1.3 million people harvest about 50 million tonnes of timber per year while increasing the amount of standing timber by 75 million tonnes. While they don’t harvest timber for power generation, the tree waste, (more than 50% of the tree is) is often compressed into pellets and provides process energy or building heat for housing, so they do use so the forests provide energy, lock carbon up for centuries in structural timber and manage to sequester Carbon in the trees and the soils all at the same time. The wind turbines are being erected in the forests and on farms adjacent to existing access and fire roads using less than 0.1% of the forest area, so no need to cut down forest.
As for landscape the Hambach mine alone has destroyed about 8,000 hectares of land forever. while providing 30,000 wind turbines will use 750 hectares. When the wind turbines are dismantled the land will return to pasture or forest. Hambach wil be a 350 m deep hole in the ground forever. After 100 years and billions of Euros it might be a lake, but probably not one you can swim safely in
Hugh Grace says
Technology has moved on quite a lot over the past 20 years. Your description of it sounds a bit Charles Dickens and it is this that allows the “decarbonisation” story to travel so well. We will be back to the problems with horse manure next – which by the way this new technology would love to use. It is now possible to use any carbon in a reactor and produce electricity, H2 and clean water with no emissions, by using a turbo expander (not a turbine). Gases produced which can be reused, sold or stored are CO2, CO, H2, H2O and nitrogen (if using air in the reactor). These are described as technically “pure” so have real commercial value. All the NOx, Sox, etc., have gone and the likes of sulphur make their way to the bottom of the reactor to be drawn off and sold. The system is entirely enclosed so there are no emissions.
This is thermal chemistry inside the reactor. Nothing is burnt and no heat is applied externally. There are no boilers and no steam is produced. The transfer of heat to the Turbo is effectively 100% so any process efficiency loss is due to the Turbo. The Turbo plays the part for which it is well known of dropping temp and pressure in Nano seconds so allowing the separation of gases. The process can be ramped in minutes and has no moving parts so requires little maintenance in its 25 year life. Its footfall is small – we can place 50 MWh unit (Reactor plus Turbo) into a 40 foot mobile shipping container.
The fuel used is any carbon plus a liquid which can be sewage, seawater or acid runoff from mines.
I am quite happy to compare that with any technology that is presently in use just on those features alone. I could add the applications (green ports, transport, agriculture…..) and the fact that no grid is required, demand side generation is provided and isolated rural areas would be able to use their own carbon resources to generate low cost electricity and clean water. They could also fly one into a disaster area.
Does this technology really exist – yes.
Have you heard of it before – no.
The music of “decarbonisation” is amplified out by the whirring of windmills – yet we know that globally “decarbonisation” will not work – until we are drowning in the stuff. The irony is that we all know there is one aspect of carbon that we have to deal with – it is called “waste” and that is never going to go away.
Peter Farley says
I would like to know more about this technology, if it truly is zero emissions I am all for it. Is there a website explaining it
But I am confused,
1. A turbo-expander is a turbine and therefore subject to the laws of Carnaut efficiency.
2. We don’t know decarbonistaion will not work. Global energy use is about 150 MWh per square km of habital land. Germany is already generating 600 MWh/square km from renewables and if over the next 20 years it replaces wind turbines and solar panels as they reach 25-30 years old, it will be able to increase output to 1,500 MWh/ square km
Hugh Grace says
The ARDAU Technology. If you have a look at http://www.ardaucommunitywastepower.co.uk it will give you a broad idea about the technology. Unless you are an expert on thermal chemistry and super critical water etc. too much science could cause sleepless nights but we can provide sufficient information should you like it.
Turbines and Turbos work in very different ways and are not alike. Industrial turbos are best known for handling pressure drops for oil pipelines and for their ability to allow for cooling and gas separation. Their weight and size gives a very good idea of just how different they are. We would not be able to put a reactor and a turbine into a 40foot shipping container – whereas we can with a turbo. Have a quick look at the present turbos/turbines on the market. By the way steam turbines are going out of business and turbos are all the rage.
The point I am making about decarbonisation is simply this. We (ARDAU) know that the way in which energy is “removed” from carbon is old fashioned and unnecessary. The inventor said so at an international conference back in the early 1990s. We are generating carbon naturally through plants/trees or “unnaturally” through our own waste – municipal, agricultural, industrial, sewerage – whatever. We have to use this or dump it. Our mining/industrial heritage also looms over us.
Germany. From our research, they have already asked the French for nuclear and been turned down. They have infrastructure to enable a continued use of lignite (similar to the poles). We can use lignite. Infact we rather like it as it has a lot of water in it which means we don`t have to add as much with our slurry. The argument about the pipeline from Russia suggest a very real divergence – at political level at least – from your description. Having said that, the German Greens are getting more powerful and will remain so until the lights go out.
Talking of lights going out, back in November 2020 the French indicated that if we had a severe downturn in temperature in (I think) Feb, the lights would go out. The UK Grid said much the same (no surprise there – they have been living on the edge for some time as was shown not long ago by the collapse of an offshore windmill connection and an onshore power station). We are on the cusp of some interesting times and I see that undersea cables from offshore windmills are potentially in trouble as well. This will unfortunately drive more on shore. Decentralised Core generation matters and it will have to come from carbon – waste or otherwise.
Peter Farley says
Mr. Grace I am all for using waste of all sorts to either be recycled or provide energy. In your case the process of recycling seems to provide energy or vice versa which is an excellent outcome.
Waste to energy broadly defined and hydro should provide most of the backup to a wind solar system and in my view hydrogen and batteries will be less important, so we have some common ground there.
However a couple of points worry me
1. a turbo expander is similar to the back half of a gas turbine, I agree it is much smaller but it it is still a Carnaut device or heat engine and without water cooling it is very unlikely to get to more than 45% thermal efficiency, unless you have an adjacent need for process heat.
2. You talk about 5 MWh in a container, but power is as important and energy capacity. I can’t find any mention of power
Hugh Grace says
Of course we have things in common and there is a place for wind/solar, just not at the scale that everyone suggests! Carbon technology has moved very fast such that people are now talking about a “new” carbon industry, which isn`t unfunny considering how long we have been using carbon.
Turbos – we don`t make Turbos but are in very close contact with the best, mostly in the States. Giving them sufficient data on what they will get from the reactor as SC Fluid (effectively 100% heat transfer), they tell us that we (at 80% plus) have underestimated the overall process efficiency. Previously from their company data we have assumed a loss of efficiency of c15% at sub critical level – so not sure where you have got 45.
Your second point. A reactor designed to produce 5MWh will work from 3-8MWh as it can be ramped very quickly – if off-line in minutes. Not sure I understand your comment.
The original essay discussed how people might be turning away from Wind/Solar. Most of the media avoid talking about carbon as it runs counter to the normal narrative and they don`t want to be seen as “non believers”. Just yesterday a senior BBC environmental reporter started with the old story of coal being on the way out. He should have added oil and gas. These industries have done little previously to “save” themselves until now, whilst – for shareholders – showing off their new green credentials of buying into wind/solar. At some point the emperors clothes will become apparent and those that have held onto these resources will be able to use these new technologies (like ours) which require less infrastructure changes and are significantly more efficient and capture all gases produced. The political calculation and timing becomes really interesting as there is nothing quite like energy security and cost to galvanise politicians. At present wind and solar are in the ascendant only held back by NIMBYs like myself. We have been asked to present our USC technology in Wales late Summer. The reaction will be fascinating as we can generate jobs, decentralised low cost electricity and hydrogen and resolve their slipping coal tips, acid water and waste across Wales. Now whether they will see it that way is quite another matter as we are challenging decarbonisation, but perhaps for the first time they will appreciate that technology is coming to their rescue and allow them to look elsewhere for solutions. Who knows – perhaps we will see windmills on the Brecon Beacons yet!!
I really liked your discussion applying the “art of war” to the clean energy debate in a previous article you published on EC. That makes a lot of sense in this transition.
About the cost of capital, the financial returns for investors are actually not the main purpose of the discount rate used in these kinds of assessments. Instead, we’re trying to value effort spent today against the benefit at some point in the future so that we properly direct our efforts today. This valuation of future benefits has large practical implications when it comes to capital-intensive equipment with long payback times because our productive capacity in the present is limited. If we put the discount rate too low, we direct a lot of economic effort into capital-intensive endeavors that otherwise would have gone into possibly more valuable projects with compounding short-term returns for society.
The best place to see this is in 100% renewable energy scale-up plans. If you use a low discount rate, the levelized cost of such a plan looks quite attractive. But then you do the calculation of how much of global productive capacity it will take to stick to the proposed deployment schedule and it works out to something like 3-4% of global GDP (consuming all global growth). Aside from being totally impractical, this is simply unacceptable because our biggest global priority is to grow developed world economies to uplift the 5 billion people who still live on less than $10/day.
Roger Arnold says
Thanks. The article you mention is titled “The Strategic Case for CCS in a Hydrogen Economy”. Anyone interested can find it by searching on that title.
Regarding the cost of capital, you’re talking about opportunity cost as justification for a discount rate. That’s certainly valid, especially if one is using a discount rate as a tool for comparative analysis of alternative approaches to the same or similar ends. That, of course is just what you’re doing. There are still a couple of caveats, however.
One caveat is that the assumed discount rate affects the rankings of the alternatives. Your results show, for example, that at a cost of €2,000/kW, the optimum mix is 100% nuclear for both of the scenarios that allow nuclear, and that even at €6,000/kW, nuclear remains dominant. (That’s for the “nuclear | no CCS” scenario. For the “nuclear | CCS” scenario, nuclear remains strong at €4,000/kW, but disappears from the mix at €6,000/kW.) But at €8,000/kW, nuclear is priced out of the mix even in the “no CCS” case. However, with a somewhat lower discount rate, nuclear would remain a strong component even at €8,000/kW.
Another caveat is that with infrastructure projects, we’re dealing with the public good — something that’s notoriously slippery when it comes to assigning monetary values. E.g., pretty much everyone agrees that using the atmosphere as a free dump for CO2 wastes is an “uncaptured externality” from burning fossil fuels that distorts any cost / value analysis for coal and gas-fired power plants compared to zero carbon alternatives. But there’s a wide divergence of opinions as to how big a problem that is.
We deal with the uncaptured externality of carbon emissions by decree. By consensus, the consequences of carbon emissions are unacceptable, so we have to stop. But alternatives may have their own uncaptured externalities that won’t show up in a financial cost-benefit analysis. I dislike big wind turbines and wind farms partly for aesthetic reasons and for their affect on wildlife. But I also dislike their huge concrete, steel, and other material footprints they have, for the energy they deliver. Wind farms may show up well in financial cost / benefit analyses, but to me the cost of their construction doesn’t reflect significant uncaptured costs of the extractive industries required to support them.
Peter Farley says
While one can’t argue about aesthetics, 2,000 MW of modern wind farms with 500 containers worth of batteries will generate the same energy and power as a 1 GW nuclear plant and have much higher availability. In the first instance it will require about twice as much steel, copper and concrete as a 1 GW nuclear plant. However the nuclear plant requires the mining of 20-40,000 tonnes of uranium ore every year and its cooling towers use 20 million tonnes of water not to mention all the diesel used in mining, refining and transporting the ore and the energy used in enriching and fabricating fuel rods or the toxic tailings left behind. Net result is that over the life of the windfarm it causes the extraction of about half the amount of ore that the nuclear plant requires.
Further when one takes into account the fenced area of the nuclear power plant, mines, fuel fabrication plants and artificial water storages, the nuclear plant actually alienates more land than 400 wind turbines
Hugh Grace says
500 containers worth of batteries? The mind boggles. I hope they work better than my new car battery that fails after 3 days of inactivity. But the cost and LCA of batteries do not improve the situation and no-one as yet has found a way of making them more efficient. But efficiency doesn`t seem to matter when it comes to windmills. So long as their sails (made of highly engineered plastics?) are whirring round it is assumed that they are efficiently using the wind to our low cost benefit.
I am not going to comment further on nuclear as they can argue for themselves but we are destroying our natural spaces for a dogma I certainly don`t believe in. I think all “renewables” (in which we include our own technology) should justify themselves in terms of LCAs, added associated technological costs (e.g. batteries, advanced Grid management), process efficiencies and social/environmental benefits. Now that would be interesting!
Peter Farley says
500 containers of batteries stacked 4 high at 4 metre spacing would fit in a shed 30m x 60m about half the area required for a 500MW gas turbine and its ancilliaries. Alternatively you could put two containers at each wind turbine. If the wind turbines are spread over 4 or 5 widely spread farms output will never be zero, unlike the nuclear plant which shuts down completely for maintenance and refueling
I am not sure what you mean about no-one has found a way to make batteries or wind turbines more efficient. The fact that the cost of wind power has fallen by 70% in the last 12 years does suggest a gain in efficiency somewhere. Similarly batteries have fallen 88% in the last decade.
Alternatively the first 2.9 GW of wind capacity installed in Germany supplied 4.5 TWh per year. The last 3.3 GW of wind capacity added 20.3 TWh, in other words the output per MW of capacity increased by a factor of 4 while the cost per MW more than halved. That is some increase in efficiency
Forrestry and farming continue pretty much undisturbed under wind farms as the turbines alienate less than 0.1% of the land within the windfarm, usually the access tracks are dual use for farmers or forresters and the farmer gets lease payments which buffers farm income against weather or market swings.
Agri-voltaic systems where solar panels are placed higher off the ground and at slightly greater spacing have been shown to increase agricultural yield due to shading and windbreak effects both for horticulture and pastures so again the farmers gain rent, cheap energy and higher farm yield. What is not to like.
Destroying our natural spaces ??? wind and solar farms take up less than 1/3rd of the space required for a coal/gas mining transport and generation system. A specific example. The now closed Hazelwood mine and power station in Victoria occupied a fenced area of 29 square km, which is destroyed forever. A 29 square km low density wind/ solar hybrid farm with mixed used agriculture would have 1 GW of solar and about 1 GW of wind. Combined with the above shed and a substation it would generate the same amount of energy as the coal plant but save 23m tonnes of water per year and avoid the mining of 14 million tonnes of coal and overburden per year and the emissions of a similar amount of CO2 and pollutants. At the end of the plant life, within a year 99.5% of the land would be returned to its prior use
Hugh Grace says
Wind farms, even when spread out, will have many days when none of them work as there is no wind. The capacity factor for windmills is c20% (literature from a windmill supplier and recent info from France) so even if you improve the effectiveness of a windmill by 50% you are still not getting much better than a “not very good ” coal power station (30%).
Your collection of batteries concern me for a number of reasons – their instability – the lithium that needs mining and the fact that no one has yet made a significant advance in this area without spending billions. So batteries are no answer to storage at present.
Land use. My understanding is that 20 turbines require approx. 1 sq.km and that windmills require undisturbed air flows to enable even that 20% capacity to be achieved, which suggests clearing a fair amount of forest. People are arguing for more trees not less. As for putting solar on stilts – how are you going to clean them when you need to drive tractors underneath. How do you use the newest technologies for managing land using drones? And are we really comfortable about reducing land usage for food? As for compensation payments – they are known as “bribes” around here.
Natural spaces I see as being heavily diminished by these technologies. I have worked in heavy industry all my life and know a mess when I see one. Normally they are kept to specific locations not spread everywhere. The countryside has on the whole managed to avoid being infected by industrialisation. We have simply given in to panic by being mislead about the real value of “renewables”.
It can be argued – constantly is – that wind and sun are free. True enough but so is carbon. We don`t have to mine it or drill for it. Besides growth there is so much of it sitting on the top of the earth or in the sea which is – now – free because of our industrial heritage or simply through household waste. If we can use this carbon, without emissions, why aren`t we? We can use/store CO2 – the Carbon industry is beginning to grow very fast in its use of CO2. And our Technology`s capacity impact is closer to 80% than 20% – which is likely to produce low cost decentralised electricity and H2?
I think we are staring at a renewable industry that within a generation will have no future as the maintenance, replacement costs, grid and storage implications will be high and efficiencies will remain relatively low compared to other energy creating industries. I won`t be around to see that happen but the seeds of change I believe are already visible in the new technologies that are now appearing because they are being driven by the obvious – that most developing countries have to work with coal, fossil fuels and carbon waste, as those are their resources – and some developed countries will never be weaned off them – ever.
If I am right then pension funds need to start to look at ways of rebalancing their portfolios fairly soon before they find that the “fashion” they are supporting runs out of wind.
Peter Farley says
Things have moved on as you say. For example Enercon’s new 5.5 MW land based turbine is expected to produce 21,000 MWh per year a 43% capacity factor. The Halliade X offshore wind turbine is running at around 60%. 17 GW of new wind in 2020 added 42 TWh of new output (source EIA electric power monthly) that is a 28% CF even though most of the capacity was commissioned toward the end of the year
Battery prices have fallen from $1,000/kWh less than 10 years ago to around $150 now so I am very curious to how you can claim there is no progress, when manufacturers all over the world have road maps projecting a further 50% reduction over the next 3-4 years. Similar cost reductions have occured with solar panels.
That is why the obvious solution for developing countries is not more fossil fuels but wind, solar, flexible demand and storage. That is why the Philipines has banned new coal plants and Pakistan, India, Vietnam and even Indonesia are significantly scaling back coal plans
The permanent pad around a wind turbine is less than 200 square meters and the rest of the windfarm is still used for forestry, farming or whatever. A 155 m rotor on a 120m tower, quite a common configuration, has a ground clearance of 42m. Commercial forest rarely grow above 35m so the turbine whirs away beside an access track in the middle of the forest or the farmland. At 800 m spacing, that would mean a typical 5 MW turbine would use 0.03% of the land. 300 of them use 6 hectares of land. The most modern coal plant in Germany Datteln 4 use 70 hectares + a mine + 17,000 Ml of water every year.
This process you speak of using carbon without emissions, where is a commercial or even pilot scale application, I am very keen to know, although you claim that the market of carbon is not backed up by statistics, Worldwide US of CO2 is not growing
Hugh Grace says
Inevitably I am going to pick and chose what I answer – I should have been a politician!
Power stations and turbines will never get a good process efficiency rating (though 50-60% is known) but very expensive taking steam up to Super Critical. However it is core generation. I would be quite happy for you to quote me 40% CF on windmills and 60% from the turbine but you are going to have to add the cost of batteries, their maintenance and the sophisticated management of the Grid. LCAs on batteries and solar are not good and, for lithium, make your coal mine look small!
Developing countries. Let me give you an example of why they will avoid your prescription unless they are “persuaded” (bribed to buy our technology) to do otherwise. They do not have infrastructure for anything. Slight exaggeration but take RSA (South Africa) which we know well – the Inventor lived there. It probably has the most extensive Grid anywhere in Africa, yet it is on its knees and no one sells to it unless it has to. It has therefore seen the closure of mines, refineries etc. with the loss of many jobs. Windmills make this situation worse; Solar, because it can act more locally and is more constant, plays a small role. Illustrative of this is the fact that across Africa banking and commerce is done via mobile phones not by internet cables. They cannot afford the cables nor the distribution. An energy Grid is a major cost. They do have carbon, waste, sewage and contaminated water.
I have been following business “politics” all my life. So am a bit sceptical! Countries avoiding coal power stations is due to wanting to do the right thing – no other alternatives that they know about and financially pressurised by other politicians who want them to buy their technology – at a discount of course. This will work until their own people see they aren’t getting what they want – electricity – and so buy their own generators. Nigeria has a generator every few yards for each separate building as they lose power every few hours.
Political agreements mean precisely ZERO. China promise one thing externally and push forward with another. We are very far advanced with them on this technology using carbon – coal, waste etc. They want to keep their mines open and they have all of our waste which we have dumped there over the years.
So yes there is political movement but please look at their motives first before drawing the “wrong” conclusion! Climate change is important but not as important as staying in power!!
Peter Farley says
I don’t know where you get the figure of 3-4% of global GDP. In Australia for example which is quite wasteful of energy we need to install about 10 GW of renewables per year for 15 years to eliminate 95% of emmissions. That would cost about A$180 bn at current costs maybe $200bn including storage, grid upgrades and energy efficiency improvements. If we were as energy efficient as Italy it would be 40% lower. At the current rate of decline of renewable costs it will be 40% lower again, but even with no gains in energy efficiency and no reductions in cost that is 0.5% of GDP.
In Germany ongoing improvements in energy efficiency, electrification of transport and heating will mean that a 90% electrified economy will need about 900 TWh/y. Doing that over 15 years with 80 GW of replacement onshore wind, 30 GW of offshore wind 100 GW of behind the meter solar and 40 GW of new utility solar is about E330 bn over 12-15 years. Over that time cumulative German GDP will be about E50,000 bn so the transition costs 0.6% of GDP
I think you have misplaced a decimal point.
Even if it were 3-4% of GDP for many countries that don’t have their own fossil fuel reserves like Australia or the US, the annual savings in imports, health costs and land and water use for thermal power stations would have a renewable system earning a 20-30% ROI. I am really at a loss as to why your highly detailed models produce such obviously erroneous results
Hugh Grace says
Really interesting comments – thank you.
Is anyone factoring in the cost of dismantling windmills? Given their potential height (up to 300m) the strength and depth of foundations will take some digging out and around here no farmer will ever do that at his/her expense even though he/she is being paid 10,000 euros pa. for c20 years.
Peter Farley says
1. I am not sure of your claim that global wind capacity is expanding at half the rate that nuclear did. Last year the world installed around 114 GW of wind and as far as I can work out typical capacity factors of current generation wind varies between 35 and 55% so using an average of 42% that is 420 TWh per year. The best ever year for nuclear was 15 GW and even at 80% CF (slightly higher than the global average) that is 105 TWh per year so wind is expanding much faster. Further even though expansion in some markets has slowed it is increasing in others so there is no realistic belief that 120 GW is the maximum. Now that Japan, Korrea, Central Asia, Eastern Europe and Africa are getting involved it is not at all unlikely that before 2030 200-250GW of wind will be installed per year. As capacity factors are climbing all the time 900-1,000 TWh could be added globally from wind in a single year before 2030
2. While you are correct that public opposition is increasing in some countries, it is also true that wind is becoming more popular in others, Korea, Taiwan, Japan, Canada, US, Australia for example. Further even in Germany, repowering and offshore wind will allow production to keep increasing with a significant reduction in the number of turbines. If Germany ends up with only 20,000 4-6 MW class onshore turbines, i.e. 33% less units than it has now, and reached its goal of 30 GW of offshore wind that would generate about 500 TWh per year more than all existing electrical demand.
3. The figure of 2% of existing energy demand is quite misleading, because electrification of transport and low temperature heating will reduce energy demand in those areas by 70-80%. Further the whole fossil fuel cycle uses about 15% of all energy produced just to support itself. It is true that to the small extent that hydrogen will displace fossil fuels that will reduce overall energy efficiency, however in a 95% renewable world, hydrogen will probably only represent around 5% of energy supply so there will still be far less energy demand than there is now.
4. The fact that some wind will be located offshore is offset by the fact that in many countries, China, India, Australia and possibly even the US, transmission distances will fall. For example now in China, windfarms 20-50 km off the coast or even inland in the Southeast will be displacing coal and hydro power dragged halfway across the country either as large DC links or in coal trains or 4-10,000 km in coal ships or gas pipelines and LNG tankers. In South Australia transmission distances have fallen by at least 1/3rd since it abandoned coal. Offshore wind farms down the US east coast and in the Gulf of Mexico and floating offshore wind off California and Oregon will all reduce transmission distances compared to out of state coal plants. In Europe a 4 turbine locally owned windfarm will supply half the energy needs for a town of 20,000 people including electrified transport, so opposition will be partially circumvented by local co-ops or municipalities promoting local energy for local people
5. In a balanced wind/solar grid with advanced high CF wind and tracking bifacial solar, grid integration costs are far lower than you imply. Existing hydro, biomass and geothermal will be operated more flexibly, demand response for water heating, municipal water transfer and cold chains and even domestic applications will be widespread and automated. So called virtual transmission lines with storage at either end will double or even triple the annual throughput of existing lines and in turn carbon fibre cored conductors can increase peak capacity of many lines by 1/3rd. In summary, transmission lines in many countries and average transmission distances may well be reduced in an all renewable grid
1. Sorry, I thought it would be clear from the reference to the figure that I am comparing expansion rates relative to total energy demand. Please see my reply to Jon above who had a similar comment.
2. Larger turbines are both more visible and need to be constructed further apart to avoid large performance reductions from wake effects. Thus, I fail to see how they will address public resistance. Your calculation of 500 TWh of electricity from 100 GW of onshore and 30 GW of offshore wind assumes unrealistic capacity factors. As the Agora report about wake effects I linked in the article shows, 30 GW of offshore wind will have an average capacity factor of only about 40% (negligence of wake effects is a common mistake in optimistic offshore wind projections). German onshore wind will remain below 30%, especially if large grid expansions are to be avoided by constructing more turbines in the South. These more realistic numbers point to 350 TWh. For perspective, Germany will need about 1000 TWh of electricity in the long run (in addition to hundreds of TWh of hydrogen, biomass, and synfuels).
3. On the contrary. The 2% figure is quite generous given that wind (and nuclear) output is multiplied by 2.5 to convert it to primary energy for the comparison.
4. When the wind is not blowing, you still need most of the links to thermal generators for security of supply. And relatively common wind/solar lulls on the timescale of a week are too much for economic storage. Also, if you like to use your optimistic capacity factors, it inherently means that wind turbines are located in the windiest regions, requiring large transmission costs to reach demand centers (people generally prefer not to live in very windy places). Hence, grid costs will only increase. Also, total coal transport costs are about an order of magnitude lower than electricity transmission costs, so this is not a useful comparison.
5. All the demand flexibility options you list will come with a cost. And all will work more economically and practically with a predictable steady state power supply that only requires daily balancing. The fundamental temporal and spatial supply/demand mismatches in a wind/solar system will always involve additional integration costs that keep increasing as wind/solar shares increase. And then there is the complexity issue I highlight in the article. Even Germany, one of the most technically capable nations in the world, is struggling at this point with wind and solar at about 13% of primary energy demand (adjusted by the 2.5x factor mentioned earlier).
Peter Farley says
1. Even if you are comparing expansion rates compared to total energy demand, you are assuming wind has reached its peak expansion rates and that is not evident. You must also remember that nuclear was heavily subsidised by governments for strategic reasons and there was almost none of the environmental and regulatory red tape that renewables have to go through now.
2. I agree larger turbines are more visible and much be constructed further apart, but as we are replacing two with one and and the modern practice of placing turbines on different height towers within a wind farm and emphasis on low wind performance and the expected introduction of wake steering and/or contra-rotating turbines, wake effects will be less significant. As modern turbines have much better low wind performance there is a much greater area of Germany or any country where capacity factors will exceed 30-35% and the repowered double spaced turbines in good current sites will exceed 40% and in some cases reach 50%. from 2018 to 2020 German wind capacity increased by 3.6 GW and output by 22 TWh so the incremental output actually achieved a notional 70% capacity factor. Therefore the claim that German onshore wind performance will remain below 30% rests on very weak foundations. Similarly new offshore wind is well above 40% as the turbines are designed for lower cut in and rated speeds have taller towers and are spaced further apart. so while the claim that wake effects will reduce the output of offshore windfarms is correct your numbers are exagerated.
3. Last year wind supplied 130 TWh in Germany, even if we use your low figure of 350 TWh for eventual wind supply and high figure of 1,000 TWh of demand that is still 35% of primary energy. Using my figures 500 TWh of supply is 55% of expected demand, by the way I don’t expect my figure to be reached there would be too much curtailment so I will settle for about 40-45% wind.
4. It is true that when the wind is not blowing you need other sources of power but there are many cheap ways of storing energy and providing backup. For example the average EV carries a weeks worth of energy in its batteries, a 250L hot water cyclinder heated to 85-90 C and provided with a mixing valve can provide hot water for 3 days for the average house. A slightly larger cylinder would store enough energy to run hydronic heating for three days as well. About 2% of the usable racking space in a coolstore occupied with PCMs will allow the coolstore to run for 10-12 hours with virtually no refrigeration and by mitigating peak demand charges will reduce energy costs by 20-25%
By the way the wind is never zero. The lowest renewable week on the German grid is about 12% wind. With a system that supplies 3-4 times as much wind energy that means the worst week will be at least 40% wind, because most of the gains will be at the low end of the spectrum. Also the worst wind weeks correspond with good solar weeks. To have a balanced renewable grid Germany needs to increase solar generation by a factor of six. That means that in the worst renewable week last year wind and solar would still have provided 60% and in the worst wind week solar would have provided 120% of demand.
In practice a fully renewable grid will have to be designed to have annual capacity of about 140% of demand just like the old grid did. In 2004 Germany had 48.6 GW of coal, 22.5 GW of nuclear, 20 GW of gas, 8 GW of hydro, which at sensible capacity factors could have supplied 950 TWh of electricity. It actually supplied 480 TWh. In other words the conventional system actually operated at about 50% of its potential
That means that Germany will end up with about 270 GW of wind and about 450 GW of solar. It means that on most days hydro and biomass will be running at minimum output and solar and wind will be curtailed just as coal and gas were almost always curtailed below maximum capacity. In turn that means that on low wind and solar weeks existing biomas and hydro can supply at least 15% of energy demand and if wind only operates at 20% and solar 7% they would still supply energy at an annualised rate of 850 TWh which combined with above hydro and biomass takes you to your 1,000 TWh demand.
5. Demand flexibility comes at a cost but it is agnostic whether it is balancing varying demand against fixed supply or varying demand and supply. Does a hot water heater or water pump care whether it is turned on to absorb cheap wind, solar coal or nuclear, of course not, but the cheap wind and solar is far cheaper than the cheap coal or nuclear so overall costs fall.
Germany may be one of the most technically advanced states but it took from 1969 to 1988 for nuclear to reach 30% of power supply or 165 TWh. It took 10 years for renewables to grow from 19% to 51% of electricity supply. Last year public wind and solar supplied 183 TWh more than nuclear ever did so it doesn’t look like it is struggling too hard.
EVs will make it much easier to integrate wind and solar as the average vehicle is parked more than 90% of the time and if it is plugged in 20% of the time and vary draw by +/- 6 kW or even 2 kW, it can easily remain at a high state of charge and provide V2G stabilisation for 3-4 hours at a time without materially affecting driving convenience.
By the way the 2.5 X factor may be roughly true for the whole economy but it is not true for the most obvious areas of electrification. For example a lignite coal plant poweering an immersion hot water heater turns about 3 Joules of coal into 1 joule of hot water heating . A rooftop solar system running a heatpump needs to provide 0.25 Joules a 12:1 multiplier. EVs after considering fuel processing and transport have about 5:1 gain even allowing for the extra energy used in vehicle production