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Do androids dream of electric cars?

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crissdee
1327386.  Wed Jul 24, 2019 4:15 pm Reply with quote

dr.bob wrote:
Although an EV could certainly do 650 miles in four days (163 miles per day is well within the range of most modern EVs)


It wasn't so much the range I was pleased with, more that after twelve years and 212,000 miles, it was still working perfectly well.

 
Jenny
1327734.  Wed Jul 31, 2019 10:59 am Reply with quote

And here's an interesting thing - a solar-powered car!

https://www.quora.com/q/like-wow/The-first-long-range-solar-powered-car?ch=99&share=c9ca441f

 
Alexander Howard
1327738.  Wed Jul 31, 2019 11:26 am Reply with quote

Jenny wrote:
And here's an interesting thing - a solar-powered car!

https://www.quora.com/q/like-wow/The-first-long-range-solar-powered-car?ch=99&share=c9ca441f


Slick! Just the thing to be seen in when I take my skiing holiday in the Cairngorms this winter. Ah.

 
Alexander Howard
1327941.  Sun Aug 04, 2019 11:37 am Reply with quote

Apparently there are not enough new engineers in Britain to keep the modern world running. Are there any engineers out there who can contradict this?

 
PDR
1327942.  Sun Aug 04, 2019 12:04 pm Reply with quote

It's a glib simplification of a complex issue, but I wouldn't necessarily dispute the core message that we need to encourage more youngsters to look at STEM-based careers.

Most companies (even engineering companies) offer higher pay, grade and advancement prospects to their project managers, commercial staff and finance staff than they do to their engineers, and I can't help thinking this is part of the problem.

PDR

 
cornixt
1327977.  Mon Aug 05, 2019 10:15 am Reply with quote

They don't pay them enough in Britain. I got a 40% pay rise when I moved to the US and I'm now earning far more than I could dream of getting in the UK for the equivalent job.

I think a lot of people are put off by the difficulty of the school work to graduate though, but the job itself is far easier for the most part.

 
dr.bob
1337302.  Tue Nov 26, 2019 6:56 am Reply with quote

In the latest EV news, that famously sunny city of Dundee has just opened an electric vehicle charging hub:
https://www.bbc.co.uk/news/uk-scotland-tayside-central-49796127

The hub uses solar canopies and a battery storage system to charge up 20 vehicles at a time. This is designed to tackle the problem that more than half the population of Dundee doesn't have a driveway or off-street parking. This could prove a significant obstacle to the uptake of EVs.

The plan is that people who work in the city can park their cars at the hub and charge them up during the day, while nearby residents can charge their cars during the night.

This increase in infrastructure has coincided with the city starting to charge a fee for EV charging for the first time. Until now charging has been free to encourage the uptake of EVs but now that honeymoon period has ended. Even with that, the cost of charging EVs works out at less than 2p a mile, according to Elinor Chalmers from the Electric Vehicle Association Scotland, which still makes it cheaper to run than a petrol or diesel car.

 
suze
1337375.  Tue Nov 26, 2019 12:48 pm Reply with quote

That 2p per mile looks a bit optimistic to me. Let us use a Renault Zoe as an example. It has a 52 kWh battery, and the makers claim that a full charge is good for 245 miles.

The "fast" chargers in Dundee run at 22 kW, which means that they can charge an RZ in 2 hours 22 minutes. That's fine, because you are allowed three hours at a "fast" charger. (You're only allowed thirty minutes at a "rapid" (50 kW) charger, which wouldn't be enough.)

So to "fill up" that 52 kWh battery will cost £8.08, on the basis of 15p per kWh + 38p. (According to Drive Dundee Electric.) That's about 3.3p per mile - which is 65% more than the claim.

Now, question. Does the charger "know" when your battery is full, and stop? Or do you have to be there at the right time to ensure that i) you don't draw - and pay for - more charge than you need, and ii) your car doesn't explode?

Also, you do only get three hours at the charger. After that you're liable to get a ticket, so it means going back to your car during the working day to move it. Some would consider this tedious.

Now, we are told that there are twenty stances at the charging station. If people do move their cars around in a timely fashion, each stance can charge three cars during a working day - so sixty cars. Or put another way, one busload. Buses in Dundee are run by National Express, so would the city do better just to buy National Express a shiney new bus?


Still, Dundee is trying a bit harder than Medway where I live. The council doesn't maintain any electric car charging points. The supposedly definitive map lists fourteen run by other parties - but it turns out that six of these are private (employees or students only), and four are reported as broken, in one case for more than a year. So that's just four available to the public in a conurbation of 290,000.

 
PDR
1337380.  Tue Nov 26, 2019 1:14 pm Reply with quote

suze wrote:

Now, question. Does the charger "know" when your battery is full, and stop? Or do you have to be there at the right time to ensure that i) you don't draw - and pay for - more charge than you need, and ii) your car doesn't explode?


Yes, especially when charged in the faster modes. But even in basic (slow) mode the last part of the charge floats to a voltage and lets the current decay - once the current drops below a defined value they shut down. In the faster modes the batteries have various bits of instrumentation (temperature, mostly) which control the charge rate and automatically shut down the charger when any of several threshold values are exceeded.

Quote:

Also, you do only get three hours at the charger. After that you're liable to get a ticket, so it means going back to your car during the working day to move it. Some would consider this tedious.

Now, we are told that there are twenty stances at the charging station. If people do move their cars around in a timely fashion, each stance can charge three cars during a working day - so sixty cars.


This is the limitation I have raised before, but I just get jeered at so I've stopped bothering.

PDR

 
PDR
1337399.  Tue Nov 26, 2019 6:48 pm Reply with quote

Looking at the Dundee building on Google Maps it approximates to a right-angled triangle roughly 100m on each side, so a ballpark number for its roof area would be 5,000m^2.

If we assume a "smart" array (one that is actively tilted to make the panel normal to the sunlight) was installed over the whole roof area we can expect an average daily energy input of 4.26kWh/m^2 in Dundee [source], so that's 5000x4.26=21,300kWh per day energy input. Current [sic] solar cells are under 25% efficient, so the available output (ballpark number) will be around 5,200kWh per day.

The article suggest there are 20 charging ports, so assuming they are all equally and fully utilised the available energy to each port per day will be 260kWh.

Lets assume 100% charging efficiency because I'm not getting into that debate again, and so that suggests that the available energy will run a 22kW charger for under 12 hours per day (or a 50kW one for just over 5 hours per day).

Now these are very much "ballpark" numbers, but probably erring on the generous side IMHO. They suggest that the idea of the rooftop array capturing sufficient energy during the day to both charge cars and charge huge batteries so that charging can continue overnight doesn't seem to stack up even with only 20 charging ports.

Unless I'm missing something?

PDR

 
suze
1337402.  Tue Nov 26, 2019 7:00 pm Reply with quote

In fact, even the numbers you give there are probably over estimates.

The Dundee given in your source is actually Dundee, Oregon. It lies 11° south of Dundee, Scotland, and gets about half as much sunshine again as its Scottish namesake. (Climate data for Portland OR, which is the nearest big city to Dundee OR; climate data for Dundee, Scotland)

I'll defer to someone else on just what difference that makes, but I'd have to agree that something looks not quite right.

 
PDR
1337419.  Wed Nov 27, 2019 3:02 am Reply with quote

The dangers of late night fag-packet calcs! Apols for the error.

It's an "incident angle" thing, so the correction factor is a cosine relationship.

The Latitude for Dundee (real) is 56deg, where the latitude for Dundee (colonial copycat) is 45deg. The correction factor is therefore:

k = (cos 56) / (cos 45) = 79%

So the numbers become around nine and a half hours of 22kW charging per day or four hours of 50kW charging per charging port. So the ability to charge all day and all night would depend on an additional external electrical supply.

Incidentally - the carpark in question has 550 parking spaces, so the charging is only being offered for 3.6% of them. That's hardly going to be a massive inducement for the masses to switch to EVs in the city - I suggest it's just window dressing.

PDR

EDIT: got my lattitude correction calculation wrong - now corrected (was 66%


Last edited by PDR on Mon Dec 02, 2019 8:28 am; edited 1 time in total

 
dr.bob
1337478.  Wed Nov 27, 2019 9:12 am Reply with quote

suze wrote:
That 2p per mile looks a bit optimistic to me.
<snip>
That's about 3.3p per mile


Two things:

1) That's still cheaper than petrol or diesel, right?

2) The DriveDundeeElectric website is a bit shit and vague, but they do mention that, if you're a Dundee resident and the vehicle is used for personal use ONLY you can join the resident discount scheme. It doesn't say how much of a discount you get :(

suze wrote:
Also, you do only get three hours at the charger. After that you're liable to get a ticket, so it means going back to your car during the working day to move it. Some would consider this tedious.


This is an area where the aforementioned website is particularly shit, as I can't find any detailed information about it on there.

However, I did find this article which talks about trickle-style chargers being installed on the roof of three multi-storey car parks. It says:

Quote:
The slower chargers [...] are better-suited to those parking their cars all day.

Faster chargers located on the ground floor of three of the city’s four multi-storeys can only be used by one vehicle for up to three hours.


So it seems to me (from the limited info I can find) that the new chargers are not subject to the 3 hour limit.

PDR wrote:
They suggest that the idea of the rooftop array capturing sufficient energy during the day to both charge cars and charge huge batteries so that charging can continue overnight doesn't seem to stack up even with only 20 charging ports.

Unless I'm missing something?


I think that's also cleared up by the article I just found, as it states that the new chargers are "powered by a ground-level supply and supplemented with solar panels."

PDR wrote:
Incidentally - the carpark in question has 550 parking spaces, so the charging is only being offered for 3.6% of them. That's hardly going to be a massive inducement for the masses to switch to EVs in the city - I suggest it's just window dressing.


The original article I linked to quoted Fraser Crichton from Dundee City Council as saying "as there's an increase in EVs we can start increasing the numbers here."

It's clearly not going to solve all EV charging problems overnight, but it's a start. It seems that Dundee have plans to expand capacity as demand increases. And, as suze points out, it's way better than the situation in Medway. Dismissing it as windows dressing is doing it a disservice IMNSHO.

 
tetsabb
1337580.  Thu Nov 28, 2019 3:16 am Reply with quote

PDR wrote:
The dangers of late night fag-packet calcs! Apols for the error.

PDR


I thought you had given up.
Or do you keep an old packet for calculations?

 
PDR
1337584.  Thu Nov 28, 2019 3:43 am Reply with quote

One never gives up, one merely choses to be tobaccus interruptus. As a confirmed Remained I gave remained an interruptum for nearly 4 years, and I have no intention of changing unless/until I'm told I have a year to live due to some incurable condition.

But the fag packet in question, like the long term contribution of the Dundee car park's solar panels, is largely conceptual and metaphorical.

PDR

 

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