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A New Shade of Green

By Sherry Listgarten

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About this blog: Climate change, despite its outsized impact on the planet, is still an abstract concept to many of us. That needs to change. My hope is that readers of this blog will develop a better understanding of how our climate is evolving a...  (More)

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A Power Play

Uploaded: May 19, 2019
One of the amazing things about the power grid is that when you flip on a light switch, the power for the light is generated right then. There is no “pool” or “store” of electricity that is used to service requests. The grid doesn’t “hold” electricity in some way; it just moves it from one place to another. As it says in this primer on energy markets, “For all practical purposes, electricity use is contemporaneous with electricity generation; the power to run a light bulb is produced at the moment of illumination.” (1) Think about that. It’s hard to imagine that it actually works. You can’t have too little electricity on the grid, and you can’t have too much, yet you don’t really know what you need until it happens. On top of all that, the transmission network is subject to faults and congestion. From that same source: “Operators must plan and operate power plants and the transmission grid so that demand and supply exactly match, every moment of the day, every day of the year, in every location.” Yowza. (2)

In the “olden days” (up to about twenty years ago), a single utility would be responsible for an area, and would dial up (or down) its supply to meet demand. It owned all the power plants and transmission lines needed to do that. Now in many areas of the country, including ours, we have allowed for more competition and more resource sharing, to increase reliability, decrease prices, and spur innovation. So the job of matching supply to demand now falls to an “energy market”, which in our case is CAISO.

Similar to the monolithic utilities of old, these markets have been forecasting demand and meeting it with (flexible) supply. They do long-term demand forecasts (a year or more) to assess infrastructure needs. And they do shorter-term forecasts, including the important day-ahead forecast, which is typically within 1-3% of actual demand. Power suppliers place bids, and the lower bids are scheduled to run. These bids can be placed in the day-ahead market, or in the real-time market. That market is evaluated every five minutes throughout the day, and picks up the difference between actual demand and what was forecast a day ahead.

Here is what that looks like. In the case shown below (charts are from this market writeup), the market has ten power plants that have put in day-ahead bids, and it meets demand based on price. The cheapest four are set to run, and the price is set at the most expensive of the operating plants.


Every five minutes the market reevaluates the price. If demand is higher than forecast, then additional plants will be called on, and they will set a higher clearing price for the entire market. In a similar fashion, if there is too much supply, fewer plants will be called on to run, and the price will be lowered. (3)


Why am I telling you all this, and what does it have to do with climate?

As you hopefully remember from the last blog post, the best time to charge your EV is in the middle of the day. It’s not even close. Look at how much CO2 was generated for each MW of power throughout the day, on average, for each quarter of 2018. The average emission rate is uniformly high outside of the midday hours. For much of the year, charging your EV at night is like filling up with 70% natural gas.


Many of you were probably pretty bummed (exasperated?) by that blog post. Maybe you drive to work and can’t park your car at a charger during the day. You might be able to “fill up” during the day on a weekend, but maybe you are driving around then too. What can you do, short of getting your own rooftop solar coupled with a car-sized battery to plug into at night? There is hope.

People love to make money on markets. “Buy low, sell high” is an aphorism you may be familiar with, and it is no less true with the power market than any other market. In fact, because the power market is relatively new and quickly changing, there are arguably more opportunities to make money than in a typical market. There is considerable price variability, several markets in which to trade, and relatively little competition. Why does this matter? The beauty is that price often corresponds with emissions, and that is true even when renewables are out of the picture, due to variability in non-renewable plants. Here is a diagram showing power resources from most expensive to least expensive. You can see the correlation with emissions. (4)


So organizations trading on the power market with the goal of making money are also, as a nice side effect, lowering emissions. How does this work?

Throughout the day there is some variability in prices as different power plants come online. Events occur that result in a drop in supply, such as congestion on a portion of the grid or a power plant going offline. An auxiliary power plant will start to ramp up. The power from these responsive “peaker units” is higher priced and often fairly dirty. So we see transient price (and emission) spikes. Here is what that looks like, with real-time pricing on top, compared with the day-ahead pricing below, from May 14. (5) A “normal” price would be between $20-$50 per MWh, but you can see spikes up to $1000 per MWh on the real-time market!


Money can be made, and emissions avoided, by bypassing these expensive (and dirty) spikes as they occur with flexible demand.

What is flexible demand? It is an electric load that can be decreased or moved to another time. Have you ever heard of a program where a utility offers to control your thermostat or air conditioner in return for a lower rate? The utility is doing this so they can turn down your AC and save money when there is a spike in price. The fastest growing source of flexible demand in this area is the electric vehicle, representing an enormous load without a fixed charging schedule. A 30-amp level 2 EV charger, which would charge a typical electric car in about 4 hours (6), is like running two central-air units at the same time. A Tesla super-charging station would be like running 40 (!) of those units at the same time. Since charging schedules often have flexibility, there is money to be made (and emissions to be saved) with EV batteries!

No, I’m not suggesting you stand by your charger and plug and unplug your EV based on the grid prices. Fortunately, technology can do that for you, such as that built by a local company, eMotorWerks, based in San Carlos. Using both their own JuiceBox smart chargers and a platform they have built that can be integrated into other chargers, they are able to aggregate these EV charging loads into virtual batteries that charge less when prices are high and more when prices are low.

Val Miftakhov, CEO and founder of eMotorWerks, is enthusiastic about the simple but powerful concept of flexible demand. “This kind of optimization can effectively double renewables penetration, simply by shifting demand away from high-emission and high-cost supply.” The virtual battery earns revenue for his company by competing on the market as a flexible demand resource. Customers can specify a minimum charge and a charging window, which the optimizer respects. A typical delay might involving postponing a 7pm charge during a spike in the after-work ramp to later in the night. Some customers may receive discounted chargers or rebates by participating. And utilities that sponsor this program can also benefit financially. In a nutshell, all parties can benefit: the environment, the customers, the utilities, and the company.

eMotorWerks today is operating a 35 MW virtual battery on both the day-ahead and real-time markets in California. As an example of their operation, in a recent month they bid on 1000 hours of excess renewable power, receiving $50/MWh. Take a look at these market graphs from May 15. Prices dipped into negative territory in the afternoon, so purchasing then would result in an income(!) of around $20/MWh. So even though eMotorWerks isn’t selling power, just by being judicious about when they purchase power (“avoid high, buy low”), they can make money and lower power costs.


And remember, this not only reduces our overall costs, it reduces our emissions. Starting in November 2016, Sonoma Clean Power deployed around 2600 JuiceNet-enabled smart chargers at no cost to consumers, and has saved over 7100 metric tons of GHG emissions. That is the equivalent of the total transportation emissions of about 160 households in that area over the same time period. That is a big difference for an essentially invisible change. Other areas are looking into this as well -- eMotorWerks is running trials in Colorado, Minnesota, and Europe. They are also testing a JuiceNet integration with Honda, in which the cars themselves would implement optimized charging.

Prices are not perfectly correlated with emissions. We know that because night and day prices are similar even though emissions are much higher at night. (8) So the rule of thumb to charge midday still holds. The JuiceNet platform is flexible enough to optimize more tightly to emissions for those who choose to do so. eMotorWerks gets real-time emissions data from the energy non-profit WattTime, and can use that as well as price to schedule charging times. It costs $50 extra for this enhancement to the charger, presumably because eMotorWerks will make less money from it, but “JuiceNet Green” is a great option for those who want to prioritize emission savings.

Christy Lewis, an analyst at WattTime, says that “interest in these time-shifting technologies is skyrocketing. People in the industry are beginning to recognize that this level of granular load-shifting is a necessary component to our high-renewables future, especially as we electrify buildings and transportation. eMotorWerks is leading the charge in this field, and we expect to see many others across multiple industries follow suit.”

There is no shortage of opportunity in this area. The difficulty, Val suggests, is in the bureaucracy needed to move forward on the ideas. The grid has long been open to integrating EV batteries, but implementing the ideas has been slow going. “For example, each customer currently requires a process with over 20 steps to participate in CAISO. We have a whole section of our company devoted to energy market participation and providing grid services. This process was designed for large resources, but could have great potential for smaller distributed resources.”

There are several other ways to use EV batteries to address the needs of our power grid, which I will cover in a later post.

Notes and References

1. Yes, electric signals do travel that quickly through transmission lines. The speed for a signal to travel between San Francisco and Los Angeles would be measured in thousandths of a second.

2. There is some tolerance for error, in that very small frequency changes can absorb some imbalance. But frequency must be kept within a very narrow margin, and in fact there is a “frequency regulation market”, often powered by batteries, that acts every few seconds.

3. Some power plants cannot respond easily to changes in demand. These plants aim to keep prices low and run at a steady pace. Nuclear and geothermal are an example of this. Gas plants and some hydropower are more likely to respond to load, and are referred to as “load following” plants. So-called “peaker plants” run only at times of high demand. Because they run infrequently, they are not built to be particularly efficient. They are dirty and charge high prices. The more we can avoid them, the greener our power. Indeed, they are slowly being phased out as battery storage comes on line. Battery storage is cleaner, can be built closer to demand, and has prices that are increasingly comparable.

4. Coal is often an exception, as it is very dirty but can be inexpensive. Fortunately it is rarely available in California.

5. This screenshot and the one below were taken from the EV JuiceNet app.

6. A “typical” EV with a 100-mile or so range might have a 30 kWh battery. (Some Teslas have 100 kWh batteries, while a plug-in hybrid might have a small 8 kWh battery.) The load on the grid depends on how fast you charge it. Some cars, particularly older EVs and those with small batteries, will limit charging power to 3.3 kW. But a “typical” car today will support a 6.6 kW charge (via a level 2 30-amp charger). The largest Teslas can take up to a 150 kW charge (via the supercharging network).

7. Interested in learning more? Next10.org has a recent series of articles on the California grid, and one specifically on EVs. FERC has also written a lengthy primer on the energy market, from November 2015.

8. This writeup has excellent graphs of price vs marginal emissions for the year 2017 on pages 7 and 8.

Current Climate Data (March/April 2019)

Global impacts, US impacts, CO2 metric, Climate dashboard (updated annually)

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Comments

 +   3 people like this
Posted by Tom, a resident of Menlo Park,
on May 19, 2019 at 12:54 pm

Another excellent post explaining how the machines and markets and policies work together in the dance toward preserving our future. One clarification I might add is that for areas like Palo Alto and Silicon Valley Clean power that both already have policies they follow for annual 100% volume matching of electric load (including new load) with the same annual volume of qualified renewables and larger hydro, the decision to electrify transport is not like filling up on 70% natural gas. It's creating the annual demand for 100% renewables that is not matched second by second with renewables but is matched on an annual total basis. And yes to be a "Good Gridizen"we should move our marginal loads to the sunny duck back hours to help absorb the realtime output of new low cost solar. The communication challenge is recognizing we as consumers have two important decisions to make. First and most important is to buy electric cars and heat pumps in clean power areas like all of CA and especially hear in the Bay Area. Second is to use or program them to take most of their power from the grid in daytime hours when it helps create demand to absorb the output of our lowest cost clean power supply (solar). The first decision was on the planning margin and created annual demand for adding renewables. This second order decision is on the operational margin and allows the easy instate use of those renewables without having to trade them to other states back and forth. The meta decision is to lobby for 100% carbon free electric policies and now to lobby for the electrification of all that is worth doing for saving our future. Example, please support each city's adoption (this summer) of new construction electric reach codes for a lower cost and cleaner future.


 +  Like this comment
Posted by Resident, a resident of Another Palo Alto neighborhood,
on May 19, 2019 at 9:30 pm

I mentioned in a comment on another one of your blogs about demand surge. We hear of brown outs as possibilities on hot days in summer, we are asked on these days not to run our washers/dryers/dishwashers in the late afternoons and during the evenings. I expect that refraining from using these does help but it is not always the big appliances, but sometimes the little ones all at the same time.

Here is how the UK have to deal with everyone in the country (or almost) putting on their electric kettles at the same time, after the end of a popular soap, or at half time of the big soccer game that everyone is watching. Web Link


 +   1 person likes this
Posted by Sherry Listgarten, a Almanac Online blogger,
on May 20, 2019 at 12:46 pm

Sherry Listgarten is a registered user.

@Resident. That is hilarious -- almost 2M tea kettles in the UK causing a demand spike after popular TV shows. It must be crazy to be a grid operator. But, that was back in 2013. Speaking of the topic of this post -- flexible demand -- it turns out that TV has gotten more flexible with Netflix and other options, and so the spikes are going away. Thank you for sharing that!

FWIW, on page 5 of this writeup is a diagram showing where researchers believe we have flexible demand in California (this is forecast for 2025). I don’t see much in the way of small appliances like tea kettles and hair dryers. Looks like most of it is still HVAC, plus a handful of other big-ticket items.

@Tom. Yes. We are so lucky in California to be able to go all-out, because our electricity is already over 50% carbon-free and we have aggressive goals to make it cleaner. We can electrify more and more things while continuing to clean up our power. I have a tougher time with recommendations for my sister, for example. She lives in Minnesota. Take a look at the power mix there (the grid there is MROW). I’m not sure it makes sense for her to get an EV at this point, because there is so much coal in that mix. And an EV is a quick purchase when it does make sense. But will there be EVs available? There is value to creating demand for EVs. I guess the question is how committed MN is to cleaning up their power, and over what timeframe. And that, I think, is where the 2020 election comes into play, for the MROW grid and others like it.


 +   1 person likes this
Posted by Tom, a resident of Menlo Park,
on May 20, 2019 at 10:59 pm

@ Sherry, Regarding adding an EV in any territory, I think it makes sense not to bother looking at the current mix, but to look at the Renewable Portfolio Standard (RPS) for the territory. In MN I see several different RPS applicable, but let's approximate them as 30% renewables by 2023 (I blended Excel's 31.5% and a few other slightly lower RPS for the example) If someone buys an EV at 0.25 kWh/mile and drives 10,000 miles/yr it creates a new demand for 2,500 kWh/yr that needs to be met. The RPS policy says it will need at last 30% of old loads and new loads to be matched with annual renewable procurement. That's 750 kWh of new renewables for the new load and up to 1,750 kWh of new electricity from non-renewables. If we recognize the sunk nukes are already running at full output and that nobody has enough money to build more of them, the 1,750 kWh can be met by increasing the fossil fuel throughput of gas or coal plants which both have CO2 footprints of about 2.2 lb/kWh when you account for gas' leaky upstream contribution. So the CO2e footprint of that driving is 3,850 lb/yr (2.2 * 1750). Gasoline has a CO2e footprint of about 28 lb/gal. (19.6 lb/gal combustion emissions and 8.4 lb/gal upstream emissions [drilling shipping, refining, trucking to station]) So the equal footprint gallons are 138 gallons/year (3,850 lb/ 28lb./gal). That means the equally GHG emitting gasoline car would need to cover 10,000 miles with only 138 gallons of gasoline. That's more than 72 miles per gallon. Or if someone buys a gasoline car getting half that MPG (e.g. 36 MPG) it's got twice the GHG emissions of the electric car in the example on the 30% RPS (70% fossil allowed).


 +  Like this comment
Posted by Sherry Listgarten, a Almanac Online blogger,
on May 21, 2019 at 1:50 pm

Sherry Listgarten is a registered user.

Tom, thanks for the response. A few comments.
(a) The RPS is for 2023. The renewable mix today (largely wind) is 20%. So wait until 2023?
(b) 4 miles/kWh seems optimistic for my sister. Maybe if it's a small car that doesn't go on the highway and she only toodles around town with it.
(c) There are factors missing (e.g., lifecycle).

I also have a question about the emissions factors. The coal/gas emissions you estimate for the power coming into the EV are 2.2 lb/kWh, which (for your economical car and/or driver) is 2.2 lb per four miles, or 0.55 pounds per mile. So that equates to a 51 mpg car, based on your estimate of 28 lb/gal. So this math would recommend an EV over nearly any gas-powered car, even if the EV were powered 100% by a gas and coal mixture (ignoring car lifecycle etc for now). Is that right? That surprises me.

I know that the EV analyses are complicated. I like this recent one from CarbonBrief, which includes an analysis of a Prius Eco (mpg 55 or so) vs a Nissan Leaf in several countries.


 +   1 person likes this
Posted by Tom, a resident of Menlo Park,
on May 21, 2019 at 4:35 pm

Sherry,
Thanks for raising those questions.
a) If the RPS target date is early in the EV life, I assume it applies for the first 10 years of the EV's long life even though CA has been raising RPS targets rapidly as MN should do during your sister's car's first career.
b) I used 0.25 kWh/mi similar what I noticed for Tesla Model 3 in the article study you linked. But I'm getting about 60 miles to the kWh on my electric cargo bike because I pedal to keep warm and entertained.
c) the study appears to overstate manufacturing emissions for batteries by embedding all the manufacturing emissions in the battery and then analytically disposing of the battery after 90,000 miles via omission. The battery was not given a second life as a grid connected renewable grid helper, it was not then recycled to save (recover) the recoverable part of its manufacturing energy by not having to start with raw dirt to get materials. And again if manufacturing emissions are a concern I highly recommend bicycles and electric bikes over cars.
Yes your observation that a 100% fossil grid electric car has GHG operating emissions as low as a 51 MPG gasoline car is right. It only seems surprising because most studies don't include upstream emissions in producing the fuels we use in gas cars or power plants. And because we mentally mistakenly equate the efficiencies of gasoline engines and fossil power plants. Gas engines small and cheap enough to power a car partially optimized for 4,000 hours in-use life (100,000 miles) (~25% efficient ) and the "engines" of large, heavy, stationary 350,000 hour (40 year) life power plants are optimized for low energy cost. ( >50% efficiency). Then the EV power train is much more efficient (~90%) than the gasoline engine powertrain (25%).
Similarly, a 100% fossil fired grid electric heat pump (COP = 3) needs less gas than the best available gas furnace (COP =.95) Electrification with heat pumps and EVs is already better than using fossils. Renewables only make electrification much much better.


 +  Like this comment
Posted by Curmudgeon, a resident of Downtown North,
on May 21, 2019 at 5:23 pm

@Tom

Bravo! Super analyses.


 +   2 people like this
Posted by Arthur Keller , a resident of Adobe-Meadow,
on May 22, 2019 at 5:52 am

1. Wind power tends to be higher at night.

2. The typical electric car driver gets 3 miles per kWh.

3. eMotorWerks implements a micro version of negawatts, a term coined by Amory Lovins.

4. Early work on the idea of timing charging was the V2G (Vehicle to Grid) studies at UDel by Will Kempton. The part about controlling the rate of charging seems to be getting more traction than feeding energy back to the grid for various reasons, including the effect on battery longevity and state of charge when we are ready to drive.

5. Kempton's work focused on the value of using lots of electric vehicle batteries for regulation services. Balancing the power used again the power generated needs to occur throughout the grid and not just grid wide. Regulation services does that at a more local level. His early work showed that plugging a million cars in 22 hours a day (when they are not being driven) would provide enough capacity to provide emission-free regulation services and not only free charging but also payments to the car owner to subsidize ownership.

6. Commercial entities are subject to demand charges based on peak electric demand. So managing charging rates to fit within demand charging budget limits as well as taking into account locally available solar power generation is effective in the short run for commercial (or other large) customers installing many chargers. PoweFlex Systems supplies networked chargers for that market. (Including institutional uses like schools and houses of worship) They are also adept at getting installation incentives from the City of Palo Alto and the Bay Area Air Quality Management District.


 +  Like this comment
Posted by Sherry Listgarten, a Almanac Online blogger,
on May 22, 2019 at 8:24 am

Sherry Listgarten is a registered user.

@Tom. Thanks for spelling out how much more efficient the fuel cycle and powertrain are for the EV. I see that in the CarbonBrief analysis as well. I expected that a power plant would be more efficient at combusting fuel than a gas engine, but hadn’t realized how much. If these figures aren’t just in your head, it would be great to cite a reference.

@Tom/@Arthur. The “mileage” of an EV depends on so many things. I think the trick with Minnesota is the cold weather for half the year. It is flat, at least, which helps. I tried to look for “real-world” numbers in various EV forums, and they are all over the map, though people generally agree they get between 3 and 4 miles/kwh, depending on amount of freeway driving, temperature/hvac, etc.

@Arthur. There have been some trials with using EV batteries to donate back to the grid. Battery wear is one issue, as well as a need for inverters, and some software issues as well. I will do a post on it at some point.

Re using batteries for regulation services, yes, it’s being done. Take a look at CAISO’s supply page, and you’ll see a “Batteries trend”, which is batteries being put to use for that.

Thanks for the pointer to PowerFlex. It’s nice to see a bunch of work on this.


 +  Like this comment
Posted by Jim, a resident of another community,
on May 22, 2019 at 2:36 pm

Sherry, thanks for another great and informative post. (And to all of the commenters here for a great on-going discussion!)

It's great to hear that there are smart (and profit-motivated) folks from Silicon Valley out there working on solutions that will help us integrate more renewables on the grid.

I look forward to reading your post on V2G. I've long thought that V2G is a fairly obvious two-birds-with-one-stone solution, enabling increased penetration of both renewables and EVs by making both more affordable.


 +  Like this comment
Posted by Tom, a resident of Menlo Park,
on May 23, 2019 at 4:21 pm

@ Sherry, per your request for data sources... For automobile efficiency I like this one from DOE Web Link
where in the lower right corner of the diagram you see 16% to 20% of a gasoline car's fuel energy making it to the wheels. It gets a little better if you ignore city driving and look at the highway tab the midpoint of efficiency is about 25% of energy making it to the wheels (where it goes into air resistance and rolling resistance and a little braking).
For California gas fired power plants I like this CEC study going up to 2014 data (since surpassed by better new plants with efficiencies around 52%) Web Link
In the right hand column of Table 4, you see some other average heat rates (fuel BTUs used to produce a 3415 BTU kilowatt-hour) The average for all plants except cogeneration plants (that are run with lots of fuel to have lots of heat extracted for industrial purposes) is 7760 Btu/kWh = 44% efficient = ( 3415 / 7760 )
Comparing the central averages from the two sources is comparing 18% efficient gasoline cars to an older fleet of 44% efficient power plants. The plants are being slowly replaced by more modern >50% efficient combined cycle plants. But using the prior comparison... long-lived optimized power plants are 2.4 times more efficient than gasoline cars and getting even better. ( 2.4 = 44 / average of (16 and 20))


 +  Like this comment
Posted by Sherry Listgarten, a Almanac Online blogger,
on May 24, 2019 at 12:32 am

Sherry Listgarten is a registered user.

@Tom. Thanks for the pointers! If helpful, the newer thermal efficiency reports from the CEC are here. Looks like it was still around 44% efficient in 2017 (the latest).

I don’t really follow the argument around energy loss in the car, since it seems to me that EVs lose energy in some of the same ways as well as in different ways, though it certainly helps that they don't have the heat-generating engine!

I modified your calculation as follows. Say a typical EV driver gets around 3.5 mi/kWh. We see that in 2017 the average non-cogenerating gas plant uses 7809 BTUs of fuel to produce one kWh of energy. So the EV driver running on 100% gas-made power is getting 3.5/7809 miles per BTU. We know a gallon of gas has 120,000 BTUs (EIA), so the EV is getting about 120,000 * 3.5 / 7809 = 54 mpg.

Does that hold water?


 +  Like this comment
Posted by Curmudgeon, a resident of Downtown North,
on May 24, 2019 at 12:33 pm

"I don't really follow the argument around energy loss in the car, since it seems to me that EVs lose energy in some of the same ways as well as in different ways, though it certainly helps that they don't have the heat-generating engine!"

If you don't mind me chimimg in on this excellent discussion: EVs have the same post-motor losses as gasoline vehicles. Larger, in fact, owing to the considerable weight of their batteries. And the electrical resistance in their motor windings generates heat. Some circulate liquid coolant to get rid of it. This resistance loss is especially noticeable in hilly country, where the energy drain substantially exceeds what straightforward physics predicts, and per-charge range is consequently diminished. The 54 MPGE figure is far more realistic than EPA's wildly overstated value. Credible, in fact.


 +  Like this comment
Posted by Sherry Listgarten, a Almanac Online blogger,
on May 26, 2019 at 8:29 pm

Sherry Listgarten is a registered user.

In a future blog post, I will do a simple EV mileage calculator localized for the CAISO grid. Will be interesting to see the range. It varies depending on type of car, how/where you drive it, when you charge it, etc. I expect it goes from about 60 mpg to about 200 mpg. (The 54 mpg estimate is for a 100% gas-powered charge, which doesn't happen on our grid, given the baseload nuclear. On average the lowest we get is about 70% fossil-fuel.)


Sorry, but further commenting on this topic has been closed.

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