PV for i-MiEV charging?

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Hippie403
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PV for i-MiEV charging?

Post by Hippie403 » Mon, 29 Jul 2013, 22:38

I'm thinking of putting in a PV system to charge my i-MiEV. I feel a bit silly driving a coal fired electric car! After initial investigation it seems it's not quite as simple as signing up for a little 1.5 kW system from my electricity supplier :(.

Melbourne is not exactly the solar capital of the world and my site will be difficult, not much north facing roof on the house. I will be building a carport in front of the garage soon so the i-MiEV can be under cover while charging from the 15 Amp socket on the side of the house. I will probably be putting the panels up on the garage and carport roofs because they can be oriented north there.

I'm going to have trouble with shading from trees and the next door house
though. I'm thinking it might be worthwhile to use a micro inverter system to mitigate the shading problems as much as possible, also I could bung a couple of extra panels up on the few bits of north facing house roof too.

Feed in tariffs for new installations in Victoria are very low, 8 cents kWh so not really worthwhile to have a grid connected system that supplies too much excess power. The i-MiEV can be charged during the day.

A new set of optional off peak tariffs are coming in, it would be nice if battery storage was available, charge battery from PV during the day and charge from the grid during off peak for use during the peak period. However micro inverters not really suitable for battery charging solutions I gather.

I saw a "Solar Edge" inverter system that had individual power controllers per panel that handled shading, different types of panels and orientations on the same string, but I don't think it supports battery charging either.

There are some "off the shelf" off grid systems available but most are still using lead acid batteries which don't seem to be that durable if they are going to be regularly deep cycled.

I seem to remember seeing an article where Ross Blade was talking about having a home fast charge system (CHAdeMO) using a Blade battery pack charged from PV. Does such a gadget exist yet?

Here is a "Lithium" battery system: http://www.solaraus.com.au/battery-storage/ seems to be available in 8,16,24 kWh models. Could I use something like this combined with micro inverter PV system or a "Solar Edge" PV system?

I'm a bit vague about how many panels I would need or could use. I think I could fit 8 * 250W panels on the garage and 8 * 250W panels on the proposed carport. The house has more east and west facing roof area than north. Might get another two panels facing north on the house.

From our last electricity bill our average daily usage is 4.7kWh

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PV for i-MiEV charging?

Post by Bryce » Tue, 30 Jul 2013, 00:38

Hi there - if you want to charge during the day via 240V, a grid connect system would be fine. Size it to deliver the total house plus car in deepest winter (June 21). Anything generated over that in peak summer could go towards your power supply charge.

If you are not too fussed with the (slightly dodgy) idea of using the grid to 'bank in the day & redraw overnight' - a grid connect system would still be OK. You are after all reducing the peak load generation needs, despite using brown electricity at night.

Grid connect PV & battery back-up systems are available - see Selectronics website for an Aussie made version. Li battery back-up is still expensive, but do-able. Rod Dilks (EV power) does some Li stuff that may work for these systems.

E-Day Life were talking about doing packages for EVs with a PV battery back-up as well as Ross Blade - though neither have come up with the goods yet.

Simplest approach if your site is PV unfriendly is subscribe to GreenPower and get a good time-of-use tariff to charge you EV overnight.

NB: if it helps, I did an article on PV's, EV's and GreenPower in the ATA mag ReNew last year (July/Sept 2012, issue 120. Would put up a copy here if I could work out how to do it!).

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PV for i-MiEV charging?

Post by coulomb » Tue, 30 Jul 2013, 02:41

Bryce wrote: If you are not too fussed with the (slightly dodgy) idea of using the grid to 'bank in the day & redraw overnight' ...

I was thinking about this the other day. When you are charging and exporting, you're not using coal for your electricity, and your neighbour isn't using coal for his electricity, since he's using your exported power. Then at night, sure you use some coal (unless you paid the extra for green power), but it's effectively the coal that your neighbour didn't use during the day.

So really it's no coal burned specifically for you, overall, as long as the amount that you export over a year covers all the importing that you do at night / rain / cloud / instantaneous shortages. The climate system only cares about the total amount of coal burned, not the fact that you delayed your neighbour's coal demand and used ("borrowed") it at night. The banking and withdrawal analogy is pretty good, really.

Edit: so while you are in reality using power from coal at night (though it could be from a wind farm too, even if you haven't paid for it, because they use the same wires), it's your neighbour's coal that has been banked for you. Of course these days, your neighbour quite possibly has solar too, but we have a long way to go before we have too much solar generation for all the loads.
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PV for i-MiEV charging?

Post by Simon » Tue, 30 Jul 2013, 04:25

Well you could say you are burning coal for all your power and it is your neighbor with green power that gets all the solar energy. Image

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PV for i-MiEV charging?

Post by acmotor » Tue, 30 Jul 2013, 04:28

Isn't that only when they add another storey and shade your PVs ? Image
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PV for i-MiEV charging?

Post by jonescg » Tue, 30 Jul 2013, 05:45

Sounds like all the more reason to go off the grid and send a big f**k you to the utilities. I think even a 12-16 kWh battery which is constantly topped up with solar would be perfect for charging your EV. You would try to do most of your charging while the sun shines, but even if you're out all day, 10 kWh would be enough to bring you up to a full charge most of the time.
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PV for i-MiEV charging?

Post by bladecar » Tue, 30 Jul 2013, 14:23

I lean to the idea of minimum output by operating power stations that are supplying the grid.

There would be a certain number of powerstations or units operating at various levels during the day. Under peak load, all the available units (+ some interstate) might be running to keep up with demand.

At night, sometimes, outgoing load will perfectly suit the number of powerstations running but I'm sure that often, the steam being produced is not being well used due to low demand. So, I charge the Electron later in the evening without concern (as Weber commented also) because it's likely that there is more steam than is being required . With the number of ev's on our roads all charging at the same time, they wouldn't change any settings to accomodate them.

As an aside, I have heard that the operators of powerstations can watch the voltage drop when a full 6*locomotive electric coal train opens the throttles to move away. That power has to be available :) even when coal trains are not starting off.

The only way to improve the situation is to remove as many coal-fired plants as possible (don't talk about brown coal) but if they're going to use csg-based gas to run alternatives, I'm not sure but I think I'd go for coal. Degraded atomosphere with global-warming implications, or the same to a lesser degree + very possible destruction of the acquifers and EVERYTHING that lives off them.

I currently see charging at night as using the offcuts, or what the supermarket throws out.

I'd love to see the arrival of a battery-pack that I can charge, even from the panels, if I wish, and that can fully charge the car, and that's all there is to it. If the price becomes or is reasonable, I'd even consider putting in the extra panels, maybe in funny places, to supply this battery pack. Mentioned this before, what electricals are required to make it happen?

We don't have to appear to be environmental saints (while, if we charge at night after peak time (might not apply in mid-summer with all those air-conditioners going), we actually are by using unused requirements).

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PV for i-MiEV charging?

Post by Hippie403 » Tue, 30 Jul 2013, 15:33

I'm not really happy with the idea that the power supply company would be buying my electricity at 8 cents kWh and selling it at 25 cents kWh. There have to be some tech and products on the market to allow consumption of my own power rather than selling it cheap. I think SMA has a new inverter with a small 2 kWh Li battery built in which seems to be a step in the right direction. I'm just trying to work out which bits and pieces I need to make a system that won't be crippled by some shading and still allow some battery storage.

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PV for i-MiEV charging?

Post by Bryce » Wed, 31 Jul 2013, 22:56

Hi there Hippie403 - if you've got shading issues, use amorphous panels rather than mono (or poly) crystaline ones. (Monocrystaline are the run of the mill panel that have the collection of black squares with lopped off corners, poly crystaline are similar looking, but no corners lopped off the squares. is to do with monos being actually slices of a cylinder with the edges cut off. (Oops, sorry. Probably "too much information"!). Poly's are sometimes blue too. (They were the old style before the modern mono ones became ubiquitous).
Amorphous may need twice the area to do the same job as the others, but they are very shade tolerant.

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PV for i-MiEV charging?

Post by Hippie403 » Thu, 01 Aug 2013, 01:07

Thanks for the info Bryce, that's the sort of ideas I'm after. Amorphous are the so called "thin film" panels right?

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PV for i-MiEV charging?

Post by coulomb » Thu, 01 Aug 2013, 02:50

Hippie403 wrote: I'm not really happy with the idea that the power supply company would be buying my electricity at 8 cents kWh and selling it at 25 cents kWh.

Don't forget, the power company has to distribute your electricity over poles, wires, and transformers (etc) to get it to where it needs to go. 8 c is about the cost of generating a kilowatt-hour (unit) of electricity; a big part of the rest of it is the distribution cost (the poles, wires, and transformers).

There is an argument that solar power typically doesn't travel very far from source (a solar inverter) to destination (your neighbour, or in some cases a dozen houses down the street). Whereas power that is generated in a power station typically comes from hundreds of kilometres away, and possibly from interstate.

Does this mean that some of the distribution cost should be paid back to the user exporting solar power? It's a tricky question.

As more and more electricity consumers install solar, the amount of coal that has to be burned to satisfy demand goes down. This is a good thing for the environment. But most of us still want power when the sun isn't shining, or when we turn on an electric oven. So the fixed price of power per kilowatt-hour becomes less and less useful for paying for the electricity infrastructure. I wonder what the electricity generating system will look like in 10 and 20 years as solar takeup continues to expand.

There is a display in the building I work in (S block at Queensland University of Technology) that shows the instantaneous power flows from one state to another, and the spot price of power at the time. It's pretty amazing; I wonder if it can be accessed from a web page.
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PV for i-MiEV charging?

Post by bladecar » Thu, 01 Aug 2013, 04:59

Coulomb,
They say that 3kWh of power needs to be generated for every 1kWh of electricity to the consumer. I guess that is averaged, and it may be the US that the figures come from, I'm not sure. This is due to voltage drop through the delivery system.

If this is true, then you could say that solar panels are generating 3 times their nominal output as far as effectiveness is concerned.

So, maybe they should be paying 3*times 8c to start with.

Anyway, as long as pollution is undervalued, the power companies will not list that cost and will only see the downside of panels (and ignore the advantage of minimised infrastructure to make it over the peaks (until they occur at night, for whatever reason).


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PV for i-MiEV charging?

Post by Hippie403 » Thu, 01 Aug 2013, 05:06

So how much do the distribution companies pay for "Green" power from commercial wind farms etc? Hmmmm.

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Post by coulomb » Thu, 01 Aug 2013, 13:46

bladecar wrote: Coulomb,
They say that 3kWh of power needs to be generated for every 1kWh of electricity to the consumer.

You are mixing power and energy. Use 3 kW and 1 kW for power, or 3 kWh and 1kWh for energy. When you lose x% power, you also lost x% of energy (fortunately, time isn't lossy, though perhaps some would argue Image ).

But the losses aren't 67% as you suggest. Per Wikipedia's electric power transmission page, total losses in the USA are estimated at about a tenth of that, 6.5% in 2007. So to send 1 kW to a consumer, you need to generate 1.07 kW. To send 1 kW to a consumer down the street, you might have to send 1.02 kW (total wild guess); the losses are higher at the low voltage end of the distribution system.

So the differential losses (total loss minus local loss) would affect the fair price of exported power very little.

[ Edit: 1.065 -> 1.07; actually it's 1 * (1 / (1 - 6.5/100)) = 1.0695. ]
Last edited by coulomb on Thu, 01 Aug 2013, 03:49, edited 1 time in total.
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PV for i-MiEV charging?

Post by coulomb » Thu, 01 Aug 2013, 13:54

bladecar wrote: Anyway, as long as pollution is undervalued, the power companies will not list that cost and will only see the downside of panels ...

Yes, that's right. Solar power has social benefits; how do we price the social benefits? As Hippie403 says, what is the fair price for green power; presumably the market price is still a bit higher than the market price for coal.
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Patching PIP-4048/5048 inverter-chargers.

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PV for i-MiEV charging?

Post by Hippie403 » Wed, 07 Aug 2013, 16:32

Anyone know of better thin film panels than these Solar Fromtier
SF165-S 165W 13.4% efficiency.
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