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Eric W.


"Tesla's claim is an obvious example of greenwashing -- and everyone seems to buy it."

They never said that electricity would be produced 100% on-site. The Gigafactory is located next to some of the best onshore wind resources in the nation, and the image posted above even includes windmills.

A company can buy renewable energy from the market.

Kris De Decker


@ Eric

Even then, aren't the solar panels on the roof a textbook example of greenwashing? The image gives the impression that a roof full of solar panels and some windmills in the distance suffice to make the factory work.

And I guess those wind resources nearby are now supplying electricity for other uses. So new windmills will have to be built.



How do these numbers compare to Nikel/Iron batteries with expected lifespans more conveniently measured in decades rather than years?

Kris De Decker


@ Charles

Unfortunately, answering that question would require a whole new calculation. Considering how much time it took to make this one, I won't be able to give you an answer anytime soon...

David F


This is a very useful article. One small correction: Tesla's "gigafactory" is in northern Nevada near Reno, not in Arizona, so the solar insolation would be less.

Another research article I didn't see in your references that looks at solar and storage from an energy cost angle (but not emissions) is Carbajales-Dale et al, 2014, at http://pubs.rsc.org/en/content/articlehtml/2014/ee/c3ee42125b It comes to a similar conclusion: At 72 hours storage, most PV systems with storage cannot pay back their energy 'debt'; wind, however, because of a more favorable EROI, can 'afford' more storage.

Kris De Decker


@ David

Thanks for the correction, I will make that calculation again. And thanks for the link, I didn't know that paper. Indeed, wind does much better than solar. It's remarkable that solar PV grows too fast to be sustainable, while wind remains far below its maximum sustainable growth rate.

And although many will read my article as a criticism of PV solar energy, for me the most surprising fact was that even an off-grid solar system can have GHG emissions below 30 gCO2e/kWh if you manufacture and install it in the right locations. It's not that renewable energy is fundamentally flawed, we just have to reconsider our priorities.

PS: I corrected your link, it didn't work.



Regarding the claims about Tesla's factory and PV.

Tesla have claimed that the factory will run on 100% renewable energy.

The calculation which claims to show green-washing includes all of the embedded energy in the materials used to assemble battery packs. For example the battery packs will contain metals, however embedded energy for these metals will be consumed at a smelter not at the gigafactory.

So I believe the calculation in this article is misleading, and that Tesla's claim may well be true.

Daron Robinson


The size is of the proposed factory is about 1000m x 400m giving a roof area of 40 hectares not 1 hectare

Martin Lindh


Great work!

A life cycle analysis of a grid connected system with only night time storage would be very interesting.



Some interesting thoughts. I certainly welcome it when people consider the emission impacts of renewable energy and you're probably right that there is a positive bias on LCAs there. However I'd assume that you can find similar positive biases on LCAs for other energy forms as well, not sure which ones are worse (e.g. there's been a lot of debate about methane emissions from natural gas in recent years that were systematically underestimated in the past).

I see the off-grid solar/battery solutions as a second best option. I don't really like them, but realistically we'll get them and they're better than staying with the status quo. The alternative - intelligent options using the grid - have one huge disadvantage: You need the grid operator to cooporate.

To put it mildly, most grid operators aren't exactly on the forefront of renewable innovation. They're often tied (or often just are) to traditional utilities that have little interest in change.

For a solution with medium and large scale storage and more intelligent grids (things like demand side management) you'd either need grid operators support (unlikely) or a very strong political regulation towards renewables (also unlikely in most countries, fossil/nuclear lobbies are strong). I live in Germany and we have relatively good political support for renewables, but even here politics is switching back and forth between supporting renewables and slowing the development down to support the old utilities. A couple of years ago there were several plans for new large scale storages (mostly pumped water, some experimental like underground pumped water or air pressure), most of them are on hold because there is little incentive right now to build them

Tim Perry


I appreciate this article but I'm skeptical of the conclusion. My background is electrical engineering and I've done some basic PV calculations in the past, but you should get feedback from a power engineer who has experience in this field.

This article on Engineering.com came up with different numbers. http://www.engineering.com/ElectronicsDesign/ElectronicsDesignArticles/ArticleID/8436/Can-Tesla-Power-Its-Gigafactory-with-Renewables-Alone.aspx

Musks companies are filled with engineers, the finest in the world, each sworn to an oath of ethics. Musks fanbase is filled with millions more engineers. If it was as unfeasible as your article suggests, I would expect an army of engineers talking about this online.

I'm not saying your wrong. It's great to be skeptical. But I'm skeptical of your conclusion about the Gigafactory.



Some points :

- nuclear can't step in for day/night variation, the ramp up of nuclear plants longer than a day, that's why nuclear is baseline in heavily nuclear countries like France
- there is a renewable that can ramp up instantly : hydroelectric
- 100% renewable without storage is theoretically possible, it will take a global grid, and then it is always sunny or windy somewhere...

Nick Nolan


20,000 GWh (20 000 000 MWh) per year is obviously incorrect estimate. It's equal to 2283 MW power consumption 24/7 (two AP1000 nuclear reactors dedicated for one factory).

Source you are using gives total energy cost of battery. The majority of the total energy usage is in material production, not battery production.

Tesla recycles all lithium in batteries, so eventually even the total energy usage will be lower. The amount of lithium they use is enormous. The whole endeavor would be financially unsound without recycling.



Great article. I wonder if it'S possible that the 400 kWh needed to produce a lithium ion battery will be reduced by scaling to mass production in the gigafactory? Or is this just the base energy required to bring the chemistry together in the battery?



Did you go from 68,000sqm to 68sqkm? If so, you are off by a thousand, and the area needed is 0.68sqkm (68ha). Also, where do you get 1ha for the roof from? Qick googling gets me in the ballbark of 1km long and 450 meters wide, which is 45ha. So half from solar on roof and rest from windmills outside doesnt seem too bad to me



Sorry my bad about the sqm calculation, made and error going from Gigawatt to Kilowatt I think.



" Because the manufacture of 1 kWh of lithium-ion battery storage requires 400 kWh of energy, the factory would require 20,000 GWh of electricity per year to manufacture all these batteries. "

Can you provide any proof of this statement ?

I suspect that your figures are a factor 100x too high (1kWh lithium storage requires only 4kWh of energy instead of 400kWh as you say).

As such your 68 square kilometers or solar PV panels required to power this factory, would be dead wrong, and Tesla would be dead right ....


See page 32-> 35kWh needed to produce one ingot of 1 kg of pure Li.

See page 33 -> Through our calculation, it means only 0.017k
Wh electricity is consumed to produce 1 Ah Li battery. It is only 3% of the energy, which is used in battery production (0.54kWh/1Ah battery). Lithium battery industry, only 4.7kg lithium metal
would be used in a 30kWh size Li-battery on average according to Argonne National Laboratory’s

Page 40 -> Lifecycle analysis of lithium iron battery by
Mats Zackrisson and Lars Avellán in 2010 claims that the total energy consumption corresponds to 11.7 kWh electricity and 8.8 kWh of thermal energy from natural gas per kg lithium-ion battery



" Remarkably, Tesla shows an illustration of the factory with solar panels on the roof. Knowing that the factory will occupy a surface of 1 ha, while 6,800 ha of solar panels is required to run it on renewable energy, Tesla's claim is an obvious example of greenwashing -- and everyone seems to buy it. "

You are wrong, the factory sits on a 980 acre site according to Tesla's weblink, that is 4 square kilometers, so plenty of space (400 hectare) available for the 68 hectares of PV solar panels that are neede to cover all the plants energy consumption. And Tesla will also build a 140MW wind turbine park, providing unknown GWh in extra power to make the plant a zero net energy facility, as they correctly stated.




Great set of articles. Made me rethink solar PV. If/when I buy it will be panels made somewhere besides Asia.

The Tesla factory is in AZ. I checked and AZ gets the majority of its power from coal (39%) followed by nuclear (28%) and renewable (10% - mostly hydro). Not sure where the rest comes from. Crazy that so little is from solar despite having the strongest sunlight in the US, Canada or Europe. Obviously there is an imbalance and opportunity.



Tesla is in Nevada (correction)

"90% of the energy Nevada consumes comes from outside the state" (http://www.eia.gov/state/?sid=NV).



You say: "the manufacture of 1 kWh of lithium-ion battery storage requires 400 kWh of energy, the factory would require 20,000 GWh of electricity per year to manufacture all these batteries."

This is wildly off. The only way you can plausibly get a figure of 400 kWh is to be looking at the total energy cost of the entire production process, from material extraction all the way through to final assembly (and even then 400 kWh seems too high, based on the sources you've cited). The final manufacturing phase - what will be done in the Tesla Gigafactory - consumes only a small portion of the total energy cost of the entire production cycle.

You may be right that the Gigafactory will not be able to meet its energy requirements from renewables, but not based on these figures. Working in your favour is the fact that the factory will in fact be in Nevada, where solar insolation is lower than in Arizona. Working against you is the fact that all the energy cost numbers available to work with are almost certainly wrong: they don't account for the somewhat uncommon battery chemistry that Tesla use, or for the new economies of scale that might be achieved by a factory of this size (although the scope for this is limited by the simple fact that 75% of the total energy cost of production is wrapped up in material extraction).

This is a really important question, one that it's really important to get right.

Spiffy Solar


Many just assume that given the right price, batteries will become a major answer to our power generation woes. That they will take over the market and perhaps the utilities as well.

Making the right decisions on when to utilize batteries sounds crucial to their usefulness.

Another important factor comes to light, upon close consideration. That is, the technology to maintain and use batteries to their full effectiveness.

Thanks for the illuminating article.



"Morgan Stanley expects a lot from electric vehicle manufacturer Tesla, who announced a home storage system for solar power a few days ago (costing $350 per kWh"

You are correct in that the home solution is priced at $350 a kWh, but you should also note that Tesla is announced to sell their 100KW commercial battery storage solution for $25,000 - which is $250 per KW. That's a pretty good deal for storage costs.

Thom the Turtle


I really enjoyed the article, but I wished it would have addressed behavioral changes that arise when power is finite, unlike the grid delivering functionally infinite amounts at all times of the day. Just as people adapt to a cell phone that drops to 20%, they will do the same in a house run on batteries powered by sunlight.

FWIW, I currently live entirely off-grid, although I do own a generator that I use about twice a month for construction projects. I helped install a small, off-grid solar system on Sunday and the issues in this article were discussed.

Kris De Decker


Sorry for the delay in publishing the comments, I had no internet access all day.

Many of the comments address the last paragraph, which accuses Tesla of greenwashing when it states that it will power its Gigafactory by renewable energy.

I should partly correct that statement. As some of you wrote, the 20,000 GWH energy use per year (the number is correct) concerns the total energy cost of all batteries produced annually in the factory, including material production. The mining of raw materials doesn't happen in the factory itself, so in that sense my claim is incorrect, and Tesla's claim might be right.

However, Tesla's claim remains greenwashing, even more so. The image and the sales talk give the impression that batteries will be produced by renewable energy, while in truth battery manufacturing in the factory itself consumes only a small share of the total energy cost of the complete production process.

Or, as one commenter on Hackernews phrased it: "Why crow over renewable energy when your use of energy is irrelevant relative to your suppliers". https://news.ycombinator.com/item?id=9484412

Tesla fits itself a green image by running its factory on solar and wind, but doesn't say a word about the much larger energy use of material production.

I have edited the paragraph to make the point clear.

Michael Dowling


What most concerns me is getting away from centralized power generation,with it's high voltage power transformers,for which there are,in many cases, no spares.I've read these things are hand built,weigh hundreds of tons,and take literally years to build and transport.If enough of them were destroyed due to a severe geomagnetic storm or a coordinated terrorist attack,grid power could be down for months or even years.Source: http://spectrum.ieee.org/energy/the-smarter-grid/a-perfect-storm-of-planetary-proportions



" I should partly correct that statement. As some of you wrote, the 20,000 GWH energy use per year (the number is correct) concerns the total energy cost of all batteries produced annually in the factory, including material production. The mining of raw materials doesn't happen in the factory itself, so in that sense my claim is incorrect, and Tesla's claim might be right."

Can you prove that statement of 20 TWh needed in energy ?

I for one does not buy it, without proof.

Critizising is very easy, when you don't have any figures at hand to state your case. That is what politicians do to sell their boondoggles to gullible voters. Your readers are often engineers, and they need facts, not baseless statements.

So where did you get this 20 TWh energy needed to make those batteries, starting from material mining ?

If you can't, then at least have the technical decency to not mention wrong figures based on zero facts, and have the intellectual decency to not launch baseless attacks on companies doing something that you aren't doing...



" However, the final manufacturing process in the factory consumes only a small portion of the total energy cost of the entire production cycle -- much more energy is used during material extraction (mining). It's stated that the GigaFactory will produce 50 GWh of battery capacity per year by 2020. Because the making of 1 kWh of lithium-ion battery storage requires 400 kWh of energy [16, 17, 18], producing 50 GWh of batteries would require 20,000 GWh of energy per year.

[16] "Towards greener and more sustainable batteries for electrical energy storage", D. Larcher and J.M. Tarascon, Nature Chemistry, November 2014

[17] "Application of Life-Cycle Assessment to Nanoscale Technology: Lithium-ion Batteries for Electric Vehicles" (PDF), Environmental Protection Agency (EPA), 2013

[18] "Energy Analysis of Batteries in Photovoltaic systems. Part one (Performance and energy requirements)" (PDF) and "Part two (Energy Return Factors and Overall Battery Efficiencies)" (PDF). Energy Conversion and Management 46, 2005. "



Kris De Decker


@ Alain

"The making of a lithium-ion battery requires between 1.4 and 1.87 MJ/wh" [16, 17, 18]

= 400 kWh energy/kWh of battery storage (based on the figure of 1.4 MJ/Wh)

x 50 GWh of batteries produced annually = 20,000 GWh of energy per year.



"The making of a lithium-ion battery requires between 1.4 and 1.87 MJ/wh" [16, 17, 18] = 400 kWh energy/kWh of battery storage (based on the figure of 1.4 MJ/Wh) x 50 GWh of batteries produced annually = 20,000 GWh of energy per year."

Thanks, this is correct, found on page 72 of your second link a similar average figure.


The TESLA factory will produce 50 GWh / year.

Knowing each battery can cycle for at least 2000 times during it's lifetime, thus storing in total around 100 000 GWh over its lifetime, for every year of production (For deep discharge use like in EV cars, if for home energy storage, it will be much higher than 2000 cycles...).

As such the TESLA factory is one gem of a plant, since it will allow on a yearly basis to add 100 000 GWh in overal energy storage capacity to our world, while only consuming 20 000 GWh in energy to get that, from cradle to grave, a return of 500 % on energy investment.

Now the big questions are :

1. is this energy needed to manufacture the batteries from cradle to grave, mostly delivered by 'clean' energy, or is it 100% fossil fuel energy ?

2. The batteries will be reloaded with 'clean' energy sourced electricity, or from fossil fuel energy sourced electricity ?

3. If for 1. and 2. most of the energy is relatively clean, then we have a big winner here, if for 1. and 2. it is mostly fossil fuel energy, then Tesla is wasting our time building it all.

I have a 4.2kW solar PV panel system on my home roof, and I am supplied by a 100% renewable energy provider utility (ecopower cvba), so for 2. it would be good for my own situation.

I however don't need home battery storage with my current setup, and do not drive yet an EV, driving range is now way too short compared to fossil fuel cars, and hybrids are still too expensive for me.

By 2020, a hybrid will be my preferred choice, probably, given that battery packs are decreasing 6% in price every year.



Musk talked about reducing fossil energy use of the US, not the world. I think he meant offshore CO2 release.

Sherwood Botsford


A possibly viable storage option: http://www.velkess.com/

offers a 15 kWh flywheel for $6K -- this is $400/kWh but it can be run to zero power, has an efficiency per cycle of 85%, and should outlast lithium batteries.

And this is an early model. If it follow the typical technology curve the price will drop fairly rapidly as more units are built.

In general the electrical companies need to see themselves in a different light, not as electricity producers, but as distributors.



I have no quarrel with your LCAs or even your conclusions.

I do think you're fundamentally incorrect to assume that off-grid systems will see any uptick at all, even a small one. I also believe the statement I've just made is completely different than saying energy storage will or will not continue to grow. The simple fact is that it makes little sense to disconnect oneself from the electricity grid. The grid in North America, and many other parts of the world that are seeing large amounts of solar being installed, is fantastically reliable. Why separate yourself from that? Even if there were some type of fee system imposed on a solar system, I doubt it would be enough to truly consider cutting that cord.

But what you're not considering, and sort of mentioned in passing in your last paragraph, is the implications of small and large storage becoming part of the grid. People smarter than me have predicted that while the financial incentives and 'free rides' of simple grid-connected solar systems might end, smarter utilities will begin to see the value of having "smarter" solar on their system, exactly for the reasons you mentioned (load shaving, frequency regulation, ramp rate adjustments, etc).

In other words, if a solar system is able to automatically respond to what the grid needs with the same level of efficiency as turning a "peaker" power plant off or on, than each kWh it produces should be worth more than the solar system a mile away that is responding to only the level of irradiance.

Examples of this future are starting to show up in island communities, where the grid is often diesel fired and electricity prices are high, though they're being installed for functionally different reasons -- namely that having 3MW of supply disappear when a cloud goes over can wreck havoc on your system.

Still, the ability to shuttle electricity to a large battery bank when supply is saturated, or pull from that bank when needed, is valuable in these situations. In certain places, it's likely that the only way large solar (in particular) would even be allowed at all is if it can meet some fairly specific ramp rate requirements, and very nearly the only way you can do that is with energy storage.

Will this be the case with smaller systems? It's hard to say, but it's I think far more likely than every house on a block being its own disconnected grid.

And regarding performing the LCAs of those type of systems, they're not really any different. While there may be different electronics, I'm not sure there are MORE electronics in a grid-connected system with batteries compared to an off-grid systems -- still charging, inversion, rectification, etc. Once you add batteries into the mix, you've already complicated the system. Does a system that talks to the grid really make it that much worse? Probably not measurably -- like having your solar factory 50 miles closer to the shipping port.

Thanks for your site -- always love the read!

Moshe Braner


The claims of 15 years (or more) float lifetime for lithium batteries seems suspicious to me. We've had lithium ion batteries in laptops and cellphones and so forth for a while now, and it's my impression that the batteries never maintain much of their initial capacity by the time they are 10 years old, or even 5. And the number of charge cycles they are subjected to is often far less than the thousands talked about in theory (although in some uses they do undergo daily cycles).

Regarding "Tesla recycles all lithium in batteries" (in a comment above), that is a promise, not a fact. If the batteries indeed last as long as claimed, they won't have to honor that promise for quite some time, and may be out of business by then.

Finally, do not assume that the batteries, unlike the PV panels, will be made in countries with cleaner grids. If off-grid storage indeed becomes a trend, what's to stop China from taking over that industry too, like they did to the many previous ones?

Mike Rossetti


Just a few thoughts:
1) I suspect, at least in the short term ('short' being 10 years or so) that we are not going to see many net-metering customers go completely off-grid. Rather, we will see them stay on-grid but drop net-metering while employing storage for buffering. Doing so will prevent net-metering customers from being treated as a special class, keeping them in the standard residential customer rate class.
Side note: The utility industry will try to discourage on-grid/buffered residential use through legislation.
Side note: Intelligent buffering reduces the most costly, peak time electricity. And by 'costly' I don't just mean most expensive in terms of dollars but also in the amount of pollutants generated.
2) The assertion in this article that residential solar customers do not pay for their use of the infrastructure is incorrect. This assumption is based on an incorrect claim that solar customers' peak load is not reduced and, thus, current rate schedules cause cost-shifting to non-solar residential customers. In Utah, the average residential solar customer consumes 5% less energy than does the overall average residential customer, implying that infrastructure usage is not being fairly compensated by those solar customers. However, the average residential solar customer in Utah has reduced their peak load by 7%—meaning they are actually paying for more infrastructure than they are actually using.
Side note: Residential customers taking advantage of high-efficiency trade-in programs also reduce their average consumption but without a demonstrable reduction in peak load.
3) One could ask what the CO2 cost has been of the utility infrastructure (mining ore, smelting, milling, transportation, installation, etc.) but that is all sunk costs so I suppose that doesn't matter much except for new residential construction.

Jim Baerg


I would like to make a few points;
You barely mentioned the problem of seasonal variation in solar availability. In a broad band the around equator seasonal variation is small & peak demand is usually in the summer so storage for solar energy is only needed to cover daily variation. Farther from the equator there is little sunlight in winter & demand is high, for solar to be much use at high latitudes the much harder problem of storing months of energy demand would have to be solved.

Where the seasonal variation in solar is small, solar electricity would complement a steady power source like nuclear, with solar covering the daytime peak in demand, especially in the panels are pointed somewhat west of equatorward so their maximum output is in the afternoon when demand peaks. This would minimize the need for storage, which is still expensive.

Re: Bruno (12) Early nuclear reactors had difficulties varying their output due to Xenon 135, but that has to a large extent been solved & the proposed molten salt reactors would not have the problem at all.

This energy storage technology might turn out to be much better than any battery for stationary applications, though it would have too low energy per liter for cars. They claim to have solved the low efficiency of compressed air storage & their method sounds like it should work. Also their compressors & air tanks should last far longer than any chemical battery.

This article (http://bravenewclimate.com/2014/08/22/catch-22-of-energy-storage/) is worth reading for anyone interested in what can be used to replace fossil fuels.

Russ Finley


I ran the numbers using Tesla's new battery for solar storage and found that it would cost me well over a million dollars to go off grid using them. But I live in Seattle. The cost will vary considerably by location:


Another engineer ran the numbers for various latitudes and found similar results:




well,... the article has a lot of information and misinformation , because a good lead acid battery has about 1500 cycles at 80% dod and about 5000 cycles at 33% dod

and on the otherhand the article starts with a tesla battery picture ..... as known , tesla gives a warranty of only 125000 miles on the 60 kwh sedan battery ...... , i would not want this poor battery in my house , to replace the 12 year old lead acid one i have

Kris De Decker


@ billi (#38)& Moshe Braner (#34):

Li-ion batteries in gadgets don't last that long because they generally have a DoD of 100%. We usually charge our gadgets only after the battery has died, which limits its durability. For home storage, portability and weight are of less concern so it's easier to add more batteries and limit the DoD, resulting in improved durability. Electric cars are somewhere in between I guess. This said, the lifespans mentioned in the article are based on a report that assumes intelligent use of batteries. Lifespans will be shorter in real life.

@ Moshe Braner (#34)

Indeed, lithium-ion battery recycling is not a fact because it's not commercially viable. It will only become so when the easiest lithium supplies are exhausted, and that means that embodied energy will go up anyways. In short, don't count on recycling to lower the embodied energy of lithium-ion batteries. http://www.waste-management-world.com/articles/print/volume-12/issue-4/features/the-lithium-battery-recycling-challenge.html

@ Jim Baerg (#36):

"You barely mentioned the problem of seasonal variation in solar availability."

Correct. See note 13. Although it might not seem this way, my article is a very optimistic take on the durability of an off-grid PV solar system. Also check the link in comment #5.

@ Mike Rossetti (#35):

That claim is made by the utilities, not by me.



Bruno - 100% renewable without storage is theoretically possible, it will take a global grid, and then it is always sunny or windy somewhere...

No: When it's night in Europe and there's a big anticyclone over the whole area, there won't be any power anywhere.

Besides, power lines also suffer from NIMBY: The German governement is having a hard time building those to connect wind turbines in the North Sea to users in the West/South of the country.

Just build nuclear plants and be done with it. Getting off oil for transportion is big enough a challenge.



This is a very high tech article for Low Tech Magazine.

jesper møller


@ Bruno

"- nuclear can't step in for day/night variation, the ramp up of nuclear plants longer than a day, that's why nuclear is baseline in heavily nuclear countries like France"

This is incorrect. It may hold true for some older designs/plants, but several nuclear plants used to day are load following.



this is precisely the awesome type of article that should be on lowtech magazine.

this is one of the best articles in a long time. a sophisticated treatment of a modern tech .

thing is, you can only write so many articles about rocketstoves and 17th century heating and kiln technology. well done lowtech mag.

on a side note, we can expect that 40 years from now revolutionary battery technology will be out. so most of what is in this article will be completely and utterly outdated.

energy storage is EVERYTHING. it practically defines the millions of years of evolutionary history of metabolism.

animals can eat whatever the hell they want as much as they want, but feast or famine defines all dynamically unstable patterns. things happen in clusters and clumps , including the acquisition and production of energy ( finding food, eating, and digesting it).


so , yes, energy storage will define the next century of technology more than any changes in energy production. the nuclear/solar/wind/ etc....all that or better coal better hydro whatever.




Why don't the lithium-ion batteries in my laptop, last for 20 years?

Lucky to get 3.



Why don't tree's count as solar batteries? ;)

Rob Halligan


I think the best "batteries" or energy stores are reservoirs. Use solar or wind power to pump water up hill to a reservoir for later electric conversion through hydro power.

There's a Canary Island that is powered by 100% wind/hydro by pumping water with excess wind energy up hill to a reservoir from a lower reservoir. They are going to all electric vehicles next.



"I live in Germany and we have relatively good political support for renewables, but even here politics is switching back and forth between supporting renewables and slowing the development down to support the old utilities."

Excuse me? Must be another Germany you live in... the one described in most official papers show that Germany spends in excess of 23 billion Euro/year for supporting renewables, and almost 11 for PV alone.
Talking about the old utilities, the implementation of the Energiewende has mean a loss of 50 billion Euros and thousands of jobs lost.
In addition to that, the GHG emissions have decreased only very marginally, pushed by reduced industrial output and milder weather conditions.



"- nuclear can't step in for day/night variation, the ramp up of nuclear plants longer than a day, that's why nuclear is baseline in heavily nuclear countries like France"

France's EDF ramps up and down its reactors every single day of the year, with amplitudes depending on day of the week, season, exceptional weather events.
You can check it out yourself here:


Sherwood Botsford


Overall, I agree with you. Off grid doesn't make sense for most people. As long as utilties have to 'net meter' being grid connected makes more sense.

One tech I expect to see fairly soon is some form of broadcast frequency standard. This can easily be piggy backed on the cell tower system, since their clocks are already based on the atomic clock time broadcast by GPS satellites. A simple receiver at each generation point not only receives a timing signal from the local tower, but also a broadcast text message telling the producers in that cell footprint, what phase to maintain relative to the time tick. (I doubt that local cell neighbourhoods would require different phasing from eachother for local production.)

In this future utilities will split into two companies (already this is true in Alberta) Production companies and wire service companies. I pay 2 electric bills a month. A fixed fee for the wires that come to my farm, and a variable fee for the electricity. Currently the latter is 8c/kWh

1. Lithium batteries recycle well. While the first round requires mining, subsequent batteries build from recycled batteries should be substantially less energy intensive.

2. Velkess has an interesting alternative to batteries, storing energy in flywheel rotating in vacuum. They are currently priced at $7500/15 kWh including inverters and transformers. (Maximum draw of 3kW) Like many technologies, I'd expect the price to drop as companies get more practice at making them. The units are too bulky for cars, but for stationary storage they are an interesting prospect.

3. For part of the off grid solution, energy can be stored thermally. About 1/3 of energy use is for building heating/cooling. This power can bypass storage and be used to run either electric heaters or a heat pump. A 4' diameter by 8 foot tank of water stores a half million BTU with a 100F cycle temperature.

4. while it won't make an immediate difference, there are other battery technologies on the horizon for stationary storage:
* Sodium sulfur is made from cheap ingrediants. Currentaly about 300/kWh, but there is only one commercial supplier. They run hot: 300C and can burn violently. Probably not something you want in your garage, but they have potential for grid connected PV environments, either at the center of the grid, or at the distribution stations. These also would make sense at wind farms so that the wind farm can guarantee better levels of service, and give longer warnings.
* Organic flow batteries. Expensive vanadium is replaced with much cheaper organic molecules. Still on the workbench so far. Flow batteries separate the idea of power and capacity. The maximum power is determined by the size of the stack -- where the reaction occurs. The capacity is determined by the solution storage tanks. Again, probably not for the home owner. Complex plumbing, pumps, wiring.
* FeSAlMg is another new tech. Energy density similar to Lion, with possible increases. Materials are cheap compared to Li, and not likely to become scarce.
* Aluminum ion batteries (carbon cathode) are coming out of Stanford U. Lots of potential.

The off-grid house isn't ready for prime time just yet -- not for most people. Tesla Power Walls may make sense for people who need some degree of backup power, but mostly those people will do better with a generator and use battery to bridge the time until the generator gets started.

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