What limits the amount of renewable energy sources?

[ORF]

Hello,

I was told every country needs a constant electricity production source (like coal or nuclear powerplants), and up to some proportion, renewable sources (photovoltaics, hydro, wind turbines, etc).

So, my question is: what limits the amount of renewable sources? (the grid, storage...?)

Thank you for four time.orf

 

[russ_watters]

This is a complicated question, particularly when you include hydro, which is not intermittent like wind or solar (but is also more limited).

It also matters whether you are talking about power or energy. E.G, the maximum power of intermittent renewables that can replace dispatchable sources is zero: all of it needs a backup. However, the dispatchable backup could be storage.

It can also depend on a country's load profile.

So, I'll say, as a starting guess, that the maximum fraction of intermittent renewable annual energy generation, barring massive storage, is probably around 25%. And in terms of power, that's around 100%.

This question is the subject of ongoing research and discussion and is googlable. For example, this article uses Germany as an example, at about 20% already having issues:

https://www.wind-watch.org/documents/hidden-consequences-of-intermittent-electricity-production/

 

[CWatters]

It doesn't all need backup if you have a half decent grid. It's unlikely all sources of intermittent renewable would stop working at the same time.

You can certainly generate high average percentages of your energy from renewable sources. Scotland managed to 54% in 2016 and 70% in 2017. I can't find a figure for 2018 but one news report say it was 98% for the month of October 2018. The figure for the whole of 2018 will be lower. In addition Scotland exports some energy to the rest of the UK. It can also import and export to Norway I believe.

The UK as a whole isn't doing as well but still produces over 50% from renewables and it's growing. Lot of money being spent on offshore wind farms.

 

[CWatters]

This wiki page is a "List of countries by electricity production from renewable sources". You can sort it by % to get an idea of the wide variation. Note the data is typically from 2016 and in some countries that data is massively out of date (by perhaps as much as 20% percent).

https://en.wikipedia.org/wiki/List_of_countries_by_electricity_production_from_renewable_sources

 

[anorlunda]

Storage is the key. Today it is expensive and limited. But research progress is rapid.

Renewable enthusiasts are not wrong, but they estimate how long it can take to change major infrastructure. Some think that if we only had the resolve, we could do it in a year. Power engineers think 45 years for major changes is breakneck speed.

 

[russ_watters]

It doesn't all need backup if you have a half decent grid. It's unlikely all sources of intermittent renewable would stop working at the same time.

You can certainly generate high average percentages of your energy from renewable sources. Scotland managed to 54% in 2016 and 70% in 2017.

Scotland is not a good example because it is barely a country (much less its own grid), and as such it gets to skip the intermittency problem. Because Scotland isn't a stand-alone grid, the high percentage of renewables is measured only against the net generation and consumption, which belies the fact that most of the *actual* electricity consumed in Scotland comes from baseload nuclear and coal and most of the *actual* intermittent renewable energy produce by Scotland is consumed by England. Because of this common situation, there is also a significant risk that you can have two countries claim credit for the same renewable energy.

So using Scotland as an example contradicts your first paragraph: it isn't a stand-alone grid and only larger countries - or more specifically, contenents with large grids can have intermittent renewables not all go dark at the same times. E.G., in the link I gave, they discuss and example when Germany's intermittent renewables roughly zeroed-out for two days. But over that period it is likely that somewhere in Europe there was still sun or wind (don't know for sure).

Scotland is just not a good example and gives a very false impression of the potential for intermittent renewables for larger countries/grids.

http://euanmearns.com/scotlands-wind-exports-to-england-and-the-myth-of-a-100-renewable-scotland/
https://www2.gov.scot/Topics/Statistics/Browse/Business/TrendElectricityty

Note also that the UK gets a high fraction (40%) of its renewable energy from biofuels, which is a source I have mixed feelings about.

 

[anorlunda]

Because Scotland isn't a stand-alone grid, the high percentage of renewables is measured only against the net generation and consumption, which belies the fact that most of the *actual* electricity consumed in Scotland comes from baseload nuclear and coal and most of the *actual* intermittent renewable energy produce by Scotland is consumed by England. There is also a significant risk that you can have two countries claim credit for the same renewable energy.

All that is true. To get a truly clean example, we need to look only at island nations. Austraila, NZ, Japan, Taiwan, Canary Islands, Hawaii, Bermuda, etc. King of them all is Iceland because of its geothermal resources.

South Australia recently had a crisis caused by overly rapid adoption of renewables and abandonment of fossil power plants. It didn't make much news overseas until Elon Musk stepped into rescue them.
https://duckduckgo.com/?q=south.australia+electric+crisis&ia=web

 

[f95toli]

Scotland is not a good example because it is barely a country (much less its own grid), and as such it gets to skip the intermittency problem. Because Scotland isn't a stand-alone grid, the high percentage of renewables is measured only against the net generation and consumption, which belies the fact that most of the *actual* electricity consumed in Scotland comes from baseload nuclear and coal and most of the *actual* intermittent renewable energy produce by Scotland is consumed by England. Because of this common situation, there is also a significant risk that you can have two countries claim credit for the same renewable energy.

But that is true of virtually every country in Europe; the grids are heavily interconnected and the market for buying/selling energy is not "local" in any way (see thee.g. EEX interchange), . Most countries will of course try to have enough energy (or a surplus ) to cover their "average" usage but that does not mean that the energy actually being delivered was produced in that country. At least int the past it was true that the south-east of England (London) would for example import electricity from France around dinner time every day when the consumption peaked

 

[russ_watters]

To get a truly clean example, we need to look only at island nations. Austraila, NZ, Japan, Taiwan, Canary Islands, Hawaii, Bermuda, etc. King of them all is Iceland because of its geothermal resources.

Does North America count as a really big island? ;)

I hear you, but while small and isolated nations can provide "clean" examples for the analysis, we should also try to make them representative of what can be done in a larger scale. Icleand is the quinticential one-off example of a country with a totally unique grid that can't be duplicated anywhere else. What it is doing tells us very little about how the world can deal with global warming - which is the big picture reason for the question. That's why my framing of the issue tends to be around large continental grids;
-North America
-EU as a whole
-China
etc.

Even in the scale of North America, the required back-up for solar has to be 100%. For wind, I'm sure people have done complicated weather and load models to predict the required level of back-up. But since it has a capacity factor of only about 33%, that makes the average back-up requirement 67%, so the peak requirement would likely be a rounding error from 100%.

 

[russ_watters]

But that is true of virtually every country in Europe; the grids are heavily interconnected and the market for buying/selling energy is not "local" in any way (see thee.g. EEX interchange), .

Yes. This is why I advocate looking at the EU as a whole (per what I just posted) because that eliminates the gamesmanship that individual countries otherwise do.

...unfortunately climate change targets are country-specific, and politics is still pretty local, so it isn't easy to get a total-EU view. E.g., I used Germany as an example above, but they play the same shell game Scotland does; claiming credit for locally produced renewables while buying Polish coal power and French nuclear.

 

[CWatters]

According to this...
https://qz.com/1193603/two-countrie...tting-its-ambitious-renewable-energy-targets/

The EU as a whole generates over 30% from renewables.

 

[russ_watters]

According to this...
https://qz.com/1193603/two-countrie...tting-its-ambitious-renewable-energy-targets/

The EU as a whole generates over 30% from renewables.

Despite a clear attempt by this and similar sources to obfuscate, it's important to note that "renewables" is not in fact a single energy source. The number is not meaningful without separating it into its constituents.

 

[anorlunda]

It is a very complex issue with lots of factets, including modifying life-style.. IMO looking at just electric without considering all energy is misleading. So are other artificial partitions that limit the discussion to one facet at a time. All the facets are interlinked. I won't call that obfuscation, but those barriers do mislead. IMO, only an all-inclusive debate on all facets of energy production and consumption is fair. Informing the voters about the issues would take on the order of one year of graduate school for each voter.

I am thinking of the broader picture

Edit: source of the picture https://www.eia.gov/energyexplained/images/charts/consumption-by-source-and-sector.png

Now imagine the upheaval if we make one small tweak. We shift most of that transportation sector consumption to the electric sector because of EVs.

 

[OmCheeto]

So, my question is: what limits the amount of renewable sources? (the grid, storage...?)

Motivation, resources, and cost, would top my list.
Rather than solve everyone's problem, and have my head explode, I like to look at what I personally need, and the least cost solutions.
Since I retired, my primary energy drain is home heating.
I discovered a couple of years ago that there is an experimental community in Canada that heats their homes almost exclusively with solar energy. [ref: Drake Landing]
It's pretty simple*. You just dig a hole and pipe hot water into it during the summer, and pipe it back into your house during the winter.
The only problem I can see with this, is if my neighbors find out about this before I put my order in.
I'm guesstimating there are about 870,000 housing units in my metro area, and there are only 19 companies that dig wells.
I have no idea how long it takes to dig a 100 foot deep well, so I guessed a week.
From those numbers, it would take the drilling companies almost 900 years to complete the task!
Even if the well diggers got really good at it, and could drill a hole in a day, drilling 365 days a year, it would still take them 125 years to finish the project.

---------------------
* Ok, I exaggerated a bit. If it were pretty simple, everyone would be doing it. The maths behind the thermodynamics involved is a quite a ways over my head. But aside from digging the hole, I'm pretty sure I could put the rest of the system together myself, for under $10,000.
Possibly WAY under $10,000. It's just a bunch of plumbing, really.

 

[Tom.G]

Quoting from the California Energy Commission:
https://www.energy.ca.gov/renewables/tracking_progress/documents/renewable.pdf
dated December 2018
page 1:
... procurement of eligible renewable energy resources (solar, wind, geothermal, biomass, and small hydroelectric) to 33 percent of retail sales by 2020 and 60 percent of retail sales by 2030.
Bar graph shows that in 2018 34% was from renewables.

page 2:
...increased to require that 60 percent renewable energy serve retail electricity sales by 2030 with an electricity sector planning target for 100 percent renewable and zero carbon resources by 2045.

Rather ambitious!

Being a rather large area, the available in-state renewables are Hydro, Solar, Wind, some Geothermal, and a small amount of Biomass. Even at that, some renewable energy is imported from out of state, especially Hydro at peak usage. Base load is mainly natural gas, with both coal and nuclear being phased out. Some of the base load natural gas fired plants are being retired and replaced with peaker natural gas plants. A new peaker gas fired plant being built near me is claimed capable of coming online in minutes, versus the hours for the plant it replaces.

Cheers,
Tom

 

[russ_watters]

IMO looking at just electric without considering all energy is misleading. So are other artificial partitions that limit the discussion to one facet at a time. All the facets are interlinked. I won't call that obfuscation, but those barriers do mislead.

What annoys me in the specific source I was referring to is the "renewables" cheerleading. When it is misleading or presented with spin - and it often is - I don't believe it is accidental. And it's harmful because it gives a false impression of the ease at which the fraction can be increased further, which affects the focus of our clean energy efforts.

The specific line in the article that irked me was the section title "Renewables now produce more electricity than coal or natural gas". Since they're grouping, another way to say it with a more even presentation would be "Renewables now produce almost half has much electricity as fossil fuels." But that doesn't sound as sexy.

But as I said, "renewables" are even more problematic to group than fossil fuels because the sources are so different and worse, most people have no idea what the distributions actually are. Grouping "intermittent renewables" is about all that makes sense to me to group. So here's the actual numbers:

Wind: 11.2%
Solar: 3.7%
Biomass: 6%
Hydro: 9.1%

Most people I've talked to about the issue believe - based on the hype - that solar power is far bigger than it actually is and don't consider biomass in the equation at all (I often forget it, because I don't really like it). The numbers are far less impressive when you consider that biomass is limited and hydro is pretty much already fully exploited. So the vast majority of additional renewable energy will have to be produced by the least flexible and most expensive sources. Which makes statements like "At the current rate of growth, the European bloc can increase the proportion of its renewables in its electricity mix to 50% by 2030" oversimplified to the point of being nonsensical. The picture gets a lot less rosy when you change that to: "the EU will need to more than double its solar and wind electricity to meet its 10 year target; a growth rate it is not meeting."

IMO, only an all-inclusive debate on all facets of energy production and consumption is fair. Informing the voters about the issues would take on the order of one year of graduate school for each voter.

I am thinking of the broader picture
View attachment 239129

Edit: source of the picture https://www.eia.gov/energyexplained/images/charts/consumption-by-source-and-sector.png

Now imagine the upheaval if we make one small tweak. We shift most of that transportation sector consumption to the electric sector because of EVs.

I definitely agree as part of the broader issue. A low-carbon future will require changing how we use energy, not just how we produce it. Certain aspects of that are relatively easy (the "heating" part of HVAC, short range land transportation in cars and trucks) and other parts will be extremely difficult (planes and ships). That's part of why IMO nuclear power is so important; because converting fuel fired heat and short range transportation to electrical means we need to produce a lot more electricity. So countries that are talking about curtailing nuclear while still saying they want to be clean are just plain being stupid IMO. They are moving in the wrong direction.

 

[anorlunda]

I don't know anyone who doesn't like solar PV and wind power. Most of us are like @russ_watters; we object to the hyperbole.

Powerless people feel empowered if they think that the technological future is in their hands politically. If they can only muster enough political will, all obstacles will be overcome overnight. Facts, natural constraints, and financial constraints don't interest them.

The world needs both realists and dreamers. Edit: But don't expect them to get along with each other.

 

[russ_watters]

Meh, I need to amplify this a lot:

Which makes statements like "At the current rate of growth, the European bloc can increase the proportion of its renewables in its electricity mix to 50% by 2030" oversimplified to the point of being nonsensical. The picture gets a lot less rosy when you change that to: "the EU will need to more than double its solar and wind electricity to meet its 10 year target; a growth rate it is not meeting."

That quote in the news article is a paraphrase of the think tank article:
"If this rate continued, then it is just sufficient for total renewables to hit 50% of the EU electricity mix by 2030 (see figure 7)."

This quote is very misleading. Here's that figure 7:

Doesn't look tooooo bad, right? Well it's zoomed-out so far that you can't tell where the data ends and the trend starts at 2017. It makes it look like there was a short-lived slow-down from 2015-16 and then started back up again. But is it a reasonable current trend? Here's their own Figure 6:

Well that looks a lot different! They almost don't look like the same data even though they really are. And clearly, the trend has been consistently slowing growth since 2012. The data better supports a leveling-off a 31% than it does a growth to 50%! The issue they gloss-over is the dropping hydro share. They mention 2017 had a drop in hydro production due to low rainfall, but the changing gap in the graphs isn't just one year, it's pretty much every year. Something else must be happening. Likely what it is is an overall stagnation of hydro generation due to it being fully exploited. Then the result is that the wind+solar+biomass is at or below the total electrical generation growth rate, so the rise in share of solar+wind+biomass is only making up for the lack of growth of hydro and not further expanding its share. But regardless of what it is, that issue is something they should be putting more effort into accounting for if they are going to make such bold predictions.

I don't think the renewable growth is done yet, but I do think that come 2030, they'll still be in the low 30s unless something changes radically. This makes their growth prediction off by something like a factor of *10* vs what their own data shows them.

 

[Guineafowl]

I have no idea how long it takes to dig a 100 foot deep well, so I guessed a week.

I had a 6” wide and 100’ deep borehole put in a few years ago. It took a day - would this work with your system?

 

[OmCheeto]

I had a 6” wide and 100’ deep borehole put in a few years ago. It took a day - would this work with your system?

Yes!
I've never seen a borehole being dug, so I was clueless as to the particulars.
Thank you.

 

[Borg]

To continue on @russ_watters post above on German power issues. I've been reading a Time Series Analysis tutorial with the pandas python package that uses the Open Power System Data (OPSD) for Germany. The tutorial examines German solar and wind, production and consumption for those interested in drilling further into the data. Since it's a coding tutorial, you have to go to nearly the bottom of the page to get to the various graphs like the one below.

 

[256bits]

for under $10,000.

Think again.

$3.4 million - 52 homes - $65,384 per home.
Subsidized by public funds.
Home owner paid only for the actual cost of house and lot.
https://dlsc.ca/reports/JUL2015/Goundbreaking_Solar_Case_Study.pdf


And it not competitive with a home using natural gas as a heating source, presently, but that could change in future years.

The incremental cost for design,purchase and installation of the entire solar heating system, CAN$3.4 million, was paid for with contributions
from the Canadian Government, Alberta government and the Federation of Canadian Municipalities. As a result, the original selling price for
the homes was competitive with conventionally heated energy-efficient homes in the same market.

Note that each house still had energy expenditures for home activities such as cooking, etc...

 

[OmCheeto]

Think again.

$3.4 million - 52 homes - $65,384 per home.

Yah. I saw that.

It's just a bunch of plumbing, really.

Have you ever hired a professional plumber? I haven't. Let's see what google has to offer:

Plumbing Cost Estimator

Plumbing Estimates

The cost of a plumber ranges from $175 to $450 for a typical job with the average cost per hour ranging from $45 to $200.​

[ref]​

Wondering if they charge more for roofing plumbing?

There was also the cost of designing the system:

Building Owner/Representative: Drake Landing Company (Atco Gas, Sterling Homes, United Communities and the Town of Okotoks)
Project Leader: CanmetENERGY, Natural Resources Canada
Project Coordinator: Leidos Canada
General Contractor: Sterling Homes (Houses) and Hurst Construction (Energy Centre)
Mechanical Engineer: Enermodal Engineering
Energy Modeler: Thermal Energy Systems Specialists (TESS)
Land Developer: United Communities
Borehole Storage Design: IF Tech International
[ref: your referenced paper]​

I would REALLY like to see a detailed cost breakdown of the entire system.

Given that I don't need to hire any of those types of companies, and can do my own plumbing, I'm pretty sure I can do it for 1/10 the price: $6,538.40 per OmCheeto home.
Given that I pay ≈$1200 for heating, it looks like a payback time of about 5 years.

My collector would theoretically also be smaller, as I have less than half the "heating degree days" that they do there.

PDX: 4155 [ref]
Drake Landing: 9027 [ref: your referenced paper]​

Where's my credit card!

Subsidized by public funds.

As God and the rest of us know, that when the government is involved, there's lots of money to be made.

 

[OmCheeto]

Ah! Hahahaha!

Whilst looking at my home value, to compare it to my system cost, I noticed that Zillow still has my solar thermal collector I built in my driveway, from about 4 years ago.

[ref: Zillow's current image of my house]

From my still somewhat naive calculations, the solar collector would cost me about $700.

Plumbing and irrigation supplies, are still dirt cheap.

note to self: more than 50% of the cost was for transparent thermal insulation, which was/is not necessary.

ps.
Home value: $250,000
cost of solar heating system: $6500
system to home value ratio: 2.6%
not ever having to pay a home heating bill again?: priceless

 

[Rive]

So, my question is: what limits the amount of renewable sources? (the grid, storage...?)

After considering it for a while already I think the answer will be 'cost'.

The very nature of the so called 'renewables' is that they are not really reliable and it takes a lot to make them fit into a system which is expected to be reliable. At low penetration it is relative easy and without much extra cost since the system already built to be able to handle some uncertainties. But as the penetration grows, the additional requirements are harder and harder to met, demanding new elements to be built to support the infrastructure in case of exceptional circumstances.
However, the average load factor of these new elements are expected to be low, paired with a high peak load => high cost.

I think the Would Be Great Power Line of the North to South of Germany (I don't know how is the actual overdue of this legendary thing right now) is a good example for this. With all the wind capacity at north and the demand at south it looks like a good idea to build this line. However, the actual circumstances when it is really needed happens only a limited days in a year, making the expected average load low. However at peak load, this line is expected to be able to transfer everything to south.
At the end, despite this line being a central problem of further green development the professional investors are not lining up to support the required money to overcome the obstacles and build it fast and easy.

The situation is ~ the same for every additional element of the grid. Power plants, lines, battery stations, whatever: if they are needed only to smoothe things related to the renevables then their cost at the expected load factor pushing the actual costs unaffordably high.

 

[Svein]

"Renewable energy" equals "energy derived from the radiation from the sun". Some of the energy is readily available (light, rain, wind etc.) and some of it has lain in storage for some millions of years(oil, coal, gas).

Comments?

 

[Guineafowl]

"Renewable energy" equals "energy derived from the radiation from the sun". Some of the energy is readily available (light, rain, wind etc.) and some of it has lain in storage for some millions of years(oil, coal, gas).

Comments?

I would say renewable energy is energy whose source will not run out in the foreseeable future.

 

[Rive]

Comments

A definition should cover geothermal too, otherwise Iceland would be in trouble

I prefer a simple list instead of such a general definition.
Also, it might be just me but I have serious problems with accepting some types of energy plantations (with that low EROEI and high input of fuel) as anything renewable (within the category of biomass).

 

[anorlunda]

"Renewable energy" equals "energy derived from the radiation from the sun". Some of the energy is readily available (light, rain, wind etc.) and some of it has lain in storage for some millions of years(oil, coal, gas).

Comments?

That includes everything except nuclear. The nuclear energy of heavy elements was stored in the atoms before formation of the sun.

In actual use, renewable is a political term, not a scientific one, so don't look for precision in its definition and use.

 

[russ_watters]

"Renewable energy" equals "energy derived from the radiation from the sun". Some of the energy is readily available (light, rain, wind etc.) and some of it has lain in storage for some millions of years(oil, coal, gas).

Comments?

Generally, it is intended to mean energy that is replenished quickly. The slowest of which are geothermal and hydro, which replenish annually. The fastest or solar and wind, which are replenished continuously (or if you prefer, daily). So fossil fuels that take millions of years to replenish are not considered renewable. Nuclear can't be replenished at all, unless we find a nearby supernova to harness.

That includes everything except nuclear. The nuclear energy of heavy elements was stored in the atoms before formation of the sun.

In actual use, renewable is a political term, not a scientific one, so don't look for precision in its definition and use.

Agreed. There is an attempt made to make the political term meaningful, but unfortunately the political motivation makes the meaning misleading and irrelevant. By that I'm specifically referring to the term's exclusion of nuclear power. What is most important about "renewable" sources isn't that they are renewable, it's that they are clean. Nuclear should be included in that. Indeed, many laws that subsidize "renewable" energy specifically cite it for being carbon free, even while excluding nuclear. These categorizations are being challenged in court and nuclear is tending to win those arguments.

Also, less important, but nuclear power doesn't need to be "renewable" because it will take a very long time to deplete it.

 

[cosmik debris]

What is most important about "renewable" sources isn't that they are renewable, it's that they are clean. Nuclear should be included in that. Indeed, many laws that subsidize "renewable" energy specifically cite it for being carbon free, even while excluding nuclear. These categorizations are being challenged in court and nuclear is tending to win those arguments.

Also, less important, but nuclear power doesn't need to be "renewable" because it will take a very long time to deplete it.

How does one counter the argument about nuclear waste? Nuclear seems clean in other respects but the waste is the waste a problem?

Cheers

 

[russ_watters]

How does one counter the argument about nuclear waste? Nuclear seems clean in other respects but the waste is the waste a problem?

When have you ever heard of an *actual* and *current* problem with nuclear waste? Not a theoretical problem, an *actual* problem. Not in the future, now. Every course of action people describe is for an actual problem: we "must" do this or that. 'We must keep nuclear waste safe for 100,000 years.' But every description of why starts with a hypothetical. Might, if, maybe, could. And silly ones at that: *If* civilization collapses, whoever's left alive *might* not recognize warning signs and become exposed to the waste.

Global warming is an *actual* problem and a *now* problem. There's CO2 in the atmosphere, the levels are rising and the climate is warming. These are facts; they are things that are actually happening now.

Actual, now problems are more important than hypothetical future ones, even if their scale is the same, which it isn't.

 

[essenmein]

How does one counter the argument about nuclear waste? Nuclear seems clean in other respects but the waste is the waste a problem?

Cheers

I think the big reason here is that people are stuck in the 60's when it comes to nuclear tech. Both Fukishima and Chernobyl are/were the same reactor generation/technology (BWR). Things have come quite a long way since those once through reactors. I blame the Simpsons.

As a primer on where we could go check out the Hitachi PRISM, or MSRs in general, also hybrid fission/fusion is very interesting (Fusor as a neutron source, nuke waste as a target/fuel). Then if cost is the next question then the answer is the SMR concepts.

Its a shame nuclear is basically the N word of the energy sector because we could already be carbon free.

 

[essenmein]

Plus "renewable" is a nonsense concept, its not renewable, the sun will run out, its just the time frame is acceptable lol.

Edit: I see someone already made this comment :D

 

[essenmein]

Then if someone raises the "natural" argument against nuclear power, well, mother nature beat us to it by a few billion years!

https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

 

[anorlunda]

We are getting far afield of the OP question.

I was told every country needs a constant electricity production source (like coal or nuclear powerplants), and up to some proportion, renewable sources (photovoltaics, hydro, wind turbines, etc).

So, my question is: what limits the amount of renewable sources? (the grid, storage...?)

Since that question was adequately answered, it is time to close this thread.