Question about EV Value and environmental impact

[MP3Mike]

I'm wondering if there's going to be a potential destabilizing issue if the EV in every garage in a neighborhood begins drawing power at precisely Midnight. This type of behavior would result in an unusual demand curve unlike anything that exists on the grid today. The power load from all these vehicles would go from zero to maximum in a few seconds.

Good thing Tesla didn't design their charging system like that. It starts at zero and slowly ramps it up. (Probably less than a minute, but certainly not all at once causing a spike.)

Also, Tesla monitors voltage and will throttle, or stop, the charge if the voltage sags too much.

 

[SageBrush]

I currently drive a 2001 BMW 3 series and have started thinking about buying a newer car. I watched the recent Tesla Model 3 presentation and was really impressed. One sticky point for me, not specific to Tesla but any EV platform has to so with where the power comes from. Specifically, if most EV drivers plug the car into their home system for power, aren’t they using coal or nuclear from local power company? Also, I see over 3,000 Supercharger locations in the U.S. where do they source power from? What is the argument for how this helps the environment.

Two answers:

1. How does the EV solution compare to what you are doing now ?
2. Can you improve either solution ? I cannot change the environmental impact of oil, but I might be able to charge an EV with home PV

 

[neroden]

I see Snowdog beat me to posting the UCS graphics.

 

[SageBrush]

It takes about 250-350 watts/hr to drive a mile

250 - 300 Wh/mile.

Apologies for the nitpick, but getting the units of measurement correct gives some support to your argument(s).

 

[jerry33]

I'm wondering if there's going to be a potential destabilizing issue if the EV in every garage in a neighborhood begins drawing power at precisely Midnight.

Mine starts at 02:30, so I don't think "precisely midnight" is going to be a big issue. I'm not the only EV owner that sets their charge time to end about the time that they start to drive, and because there are many different amounts of "daily usage" the start time will vary.

 

[jerry33]

250 - 300 Wh/mile.

Apologies for the nitpick, but getting the units of measurement correct gives some support to your argument(s).

Take a look at the Wh/mi thread where there are plenty of lifetime averages over 300 Wh/mi. 250-350 is a more correct range than 250-300.

 

[dhrivnak]

One important item I see missing from the above comments is the need to refine gasoline. The emissions data on electricity is on the electricity delivered to your home. The gasoline numbers are for burning gasoline and they assume it is magically refined and delivered to your car. If you add the GHG for refining the GHG for gasoline jumps almost 20%. This makes an EV no worse than a Prius in coal states and much better in all others

 

[AB4EJ]

A complete understanding of efficiency (for fossil fuels) takes into consideration all the steps between a certain amount of energy stored in the ground (in the form of coal, oil, or natural gas), and the amount of motive power you end up with (in the form of your car going down the road). A lot of energy is use to extract, refine, store, and ship fossil fuels. Then, the step of converting from the fuel to motive power (electric generation in the EV case, and in the engine of an ICE) is limited by thermal efficiency plus the friction losses in the engine and transmission. There are a lot of variables so you will see many different estimates of this but generally the maximum theoretical thermal efficiency of electrical generation is around 40% (i.e., if you burn fuel to create 100 BTUs of heat, the most electrical power you can possibly get is 40% equivalent or less). The maximum motive power you can get in a car using a reciprocating (ICE) engine is something less than 30% - this is because a large, highly optimized turbine is more efficient than a piston engine - this is just thermodynamics at work. In lay terms, the problem is that the exhaust (from turbine or ICE) is still very hot, and that energy is wasted. You simply can't get around this in any real-world scenario. (Modeling of turbine efficiency is by the Carnot cycle, and ICE efficiency is by the Otto cycle.. You can look it up in Wikipedia or elsewhere).

Because of the limitations of fossil fuel power generation, Tesla has been pushing for use of renewables (solar, wind, hydro) as the future of how we make cars go. Even though solar cells also have efficiency limits, once you install a system it generates power for many years without consuming anything or producing any exhaust.

 

[ElectricTundra]

Take a look at the Wh/mi thread where there are plenty of lifetime averages over 300 Wh/mi. 250-350 is a more correct range than 250-300.

That's largely for rather heavy Model S. Presumably the Model 3 will be lighter, have a lower drag coefficient, and possibly a more efficient drivetrain.

 

[Snowdog]

I see Snowdog beat me to posting the UCS graphics.

I think the coolest thing about the UCS graphics is how fast they are improving. I just 3 years, nearly everywhere in the country has grid improvements. Some are very dramatic (adding 20mpg equivalent to EVs).

Looking at where we are today, EVs are just about untouchable East/West and South. Only in some interior locations, can you do better running on gasoline, but it pretty much has to be a hybrid.

This really shouldn't be a debate any more. EVs are better.

 

[DrPhoton]

Good thing Tesla didn't design their charging system like that. It starts at zero and slowly ramps it up. (Probably less than a minute, but certainly not all at once causing a spike.)

Also, Tesla monitors voltage and will throttle, or stop, the charge if the voltage sags too much.

You make a really good point. Also, if Tesla adds the feature that lets people program their charging schedule based on departure time, rather than start time (this is one of the commonly requested features for the Model S), it drastically reduces the likelihood that a lot of EVs will start charging at the same time.

 

[SageBrush]

Take a look at the Wh/mi thread where there are plenty of lifetime averages over 300 Wh/mi. 250-350 is a more correct range than 250-300.

I agree; I was highlighting the correct units and not the value

 

[Snowdog]

I think EVs have clear advantages in several environmental areas.

1. CO2: Look at the UCS graph posted previously, and the delta between them. EVs really are better in just about every locality and certainly overall. This is important for the long term health of our entire ecosystem.
   
2. Other Local tailpipe pollutants: Other pollutants tend to have more local, short term effects. So they aren't a long term factor for the planet, but they are causing misery, health problems and even early death for people. Things like NOx (hello VW), particulates, VOCs, etc... Big advantage just moving these out of population centers and having them at more remote power plants.
   
3. Brake Dust: Say What? It doesn't come to the surface often, but a significant portion of particulate matter near roadways is caused by brake dust. More Regen and less friction braking will reduce this significant contribution to hazardous particulate pollution.

Bottom line, is if we replaced Combustion powered cars with EVs, we would reduce CO2 emissions for the long term health of the ecosystem, and we would all be breathing cleaner air, resulting in healthier, longer lives.

EVs are pure Win on the environmental issues. We just have vested interests trying to sling mud at them, much like we have well funded AGW denier groups. Much like we had groups fighting Lead reductions in Gasoline, or the Tobacco industry denying cancer links...

 

[shrspeedblade]

The easy way to do this is to use those 'smart meters' they got us to put in, to transmit the current price to our charger. The charger then waits for the right time. And if the price gets really high, the charger sells power from the battery back to the grid for a profit...

Thank you kindly.

I really like this idea, especially as someone for whom solar is not a viable option. Just have a, "help the grid" setting that will give back up to 33% of the battery (or set %, because most the time even 50% charge is more than enough) that you can easily turn off if going on a long trip the next day. The car could text you a notification if this ever starts to happen.
This solution alone would probably eliminate all concerns of grid demand at night for years to come and even save EV owners a little $. Excellent idea!

 

[SageBrush]

The Union of Concerned Scientists produce a nice MPG equivalent map. Here are a relatively new one and and one a couple of years old (2015 v 2012?).

This shows in many places, that an EV is better than anything but a Prius, and it also shows, that the grid is cleaning up fast. So the EV you buy today, just keeps getting better with regards to emissions:

The improvement certainly seems like great news, but keep in mind it is mostly due to substitution of coal by natural gas. As the environmental costs of NG extraction are more clearly accounted for the CO2e value is going to rise -- quite a bit. Not as bad as coal, but not as good as it appears. I think the real advantage of NG is the reduction in SOx and Nox, not the CO2.

Second, these maps were calculated by using average grid emissions for each region. I consider that method flawed because the cleaner source fuels do not scale with increased demand. The studies performed by the US national labs use marginal emissions, which are almost exclusively fossil fuels. In marginal emissions terms it plays out like this:

NG is ~ 1 lb CO2/kWh (by current methods that do not do a good job of counting extraction costs.)
Coal is ~ 2 lb CO2/kWh
Petrol is ~ 24 lbs CO2/US-gallon WtW

Using a 3 mile/kWh EV, the cars are about equal in CO2 emissions at
72 MPG petrol car in a 100% NG fueled EV
36 MPG petrol car in a 100% Coal fueled car
54 MPG petrol car using the median fossil fuel mix in the US
Night-time charging: More coal
Day-time charging: More NG

Third,and perhaps most important from an unbiased environmental perspective, this map ignores opportunity cost. For example, a person who buys an inexpensive, efficient ICE car and plows the money saved into PV is way, way ahead in an environmental sense compared to a person who buys a Tesla and relies on the grid for energy.

I am as much pro-Tesla as anybody here, but I like to temper my enthusiasm with facts.

 

[Snowdog]

I am as much pro-Tesla as anybody here, but I like to temper my enthusiasm with facts.

What facts? You are making assumptions and doing simplified calculations.

UCS numbers are based of the most detailed models available today. This is done by a lot of serious scientists, checking each others working and updating annually.

That you presume you know better, is laughable.

If you seriously think you know better, contact UCS and help them correct their calculations.

Until then I will take the UCS numbers as the closest things to facts, and forum posters as hot air.

 

[mspohr]

You make a really good point. Also, if Tesla adds the feature that lets people program their charging schedule based on departure time, rather than start time (this is one of the commonly requested features for the Model S), it drastically reduces the likelihood that a lot of EVs will start charging at the same time.

Tesla has the potential to manage charging in cooperation with utilities. They could start and stop charging of large numbers of cars to help manage the grid. Owners could even get free electricity in exchange for the service.

 

[Jeff N]

I really like this idea, especially as someone for whom solar is not a viable option.

I see you live in CA from your profile but don't know what region. PG&E in Northern CA very recently introduced a new "Solar Choice" option that funds solar panels regionally to supply your power instead of you having panels on your roof which may not work well for some people for a variety of reasons. It's a little more expensive (but supposedly will get better over time and as it scales up). I'm on 100% solar now through this option.

It was negotiated and designed between the utility and various renewable energy activist groups to replace PG&E's original plan submission. It seems like a good alternative to me at the moment.

Southern CA utilities may have similar plans in the works but I have not been following other regions closely.

Second, these maps were calculated by using average grid emissions for each region. I consider that method flawed because the cleaner source fuels do not scale with increased demand. The studies performed by the US national labs use marginal emissions, which are almost exclusively fossil fuels. In marginal emissions terms it plays out like this:

NG is ~ 1 lb CO2/kWh (by current methods that do not do a good job of counting extraction costs.)
Coal is ~ 2 lb CO2/kWh
Petrol is ~ 24 lbs CO2/US-gallon WtW

Using a 3 mile/kWh EV, the cars are about equal in CO2 emissions at
72 MPG petrol car in a 100% NG fueled EV
36 MPG petrol car in a 100% Coal fueled car
54 MPG petrol car using the median fossil fuel mix in the US
Night-time charging: More coal
Day-time charging: More NG

It's all complicated and stuff. The best we can do is make gross (!) generalizations about fuel sources and then devote ourselves to making the fuel mixes cleaner.

Your estimates for NG and coal may be too low or not account adequately for upstream emissions. The gasoline estimate is probably better as a national average but it also varies between regions due to crude oil sources.

Nighttime CO2 may look better than daytime in areas with heavy coal use because coal is not usually used for load-following.

Nighttime CO2 may look worse than daytime in areas with less coal intensity because solar sources end and coal plants tend not to be ramped down at night.

As we get more plugins on the grid it makes less sense to count their usage as being on-the-margin versus all other electrical uses. Over the longer horizon with mainstreaming of EVs, I think using average fuel mix as a general guide to CO2 emissions makes more sense.

 

[liuping]

Tesla has the potential to manage charging in cooperation with utilities. They could start and stop charging of large numbers of cars to help manage the grid. Owners could even get free electricity in exchange for the service.

Several companies are looking into smart/scheduled charging solutions for the future.

All it would take is knowing how long the car needs to charge and when it needs to be done. If each car sends that info to a central location, it could schedule the best start times for each car in the neighborhood to minimize the impact on the grid and local transformers.

At our house we try to reduce the grid impact by having our Volt set to "finish charging by 5am" and the Tesla to "start charging at 12:05am". Many nights they don't even overlap and they always finish during the superoffpeak rate period.

 

[SageBrush]

UCS numbers are based of the most detailed models available today. This is done by a lot of serious scientists, checking each others working and updating annually.

That you presume you know better, is laughable.

Calm down ... reading source publications critically is not a crime.

Read the publications of the US national energy labs, get familiar with GREET, understand the underlying methodologies and their differences. Fwiw I am not impugning the scientists at UCS by disagreeing with your conclusions from their data. And since very good science disagrees with their underlying methods when the question is CO2 advantage, I'll just politely suggest that you read more and mumble less. Your advocacy will be the stronger for it.