Solar Power Advice

[Ozukus]

Would anyone out there classify themselves as a DIY solar power guru. I'd like to understand a few aspects of this with regard to charging my PHEV using Solar Power, but have no idea of what panel outputs actually relate to what the PHEV needs etc.

E.G. If I had a dual axis tracking system fitted with Solar panels of Width x Length generating nnnn Watts then this would provide n.n KW charge to the car over n.n Hours.

For this I would need

Dual axis tracking system
Power Inverter
xxx branded solar panels

Sort of after a Solar for Dummies!!

 

[PeterGalbavy]

I am about to have domestic solar PV fitted in the UK. It's a triple roof mounted system, no tracking.

The financial impact and advantages will depend on your location. In the UK we get money to generate solar electric even if we use it all and not pass any into the grid.

My system will be micro-inverter based which will "limit" me to 250W per panel, even though the panels are 285W ones - but that's fine as over the lifetime (20 years min) of a panel it will lose about 10-20% of it's capacity and the weather conditions to generate the full 285W are very rare. I chose this route as I don't want a big wall mounted inverter in my loft space that may lock up or need access for maintenance and also any shading or failure of a panel is minimised. There are DC optimisers also, but after some reading and reviews I stuck with the microinverters.

I think your choice of brands will be down to the usual combination of availability, price, efficiency and long term warranty. The last one is the hardest as so many companies have gone to the wall over the years that warranties are usually worthless over the long term.

Google may be your friend

 

[gwatpe]

PV alone will not recharge your PHEV. I would not plug anything into the bigger DC socket apart from a rapid charger plug. I recharge my PHEV from my OFF GRID solar, battery, AC inverter system. My PHEV in AUS with supplied recharger PHEV requires at least 2.2kW of AC power when recharged from the AC cord.

My house battery has sufficient storage and inverter capacity to supply what the PHEV recharger needs, day, or night. The solar recharges the house battery from DC panel sources as well as AC panel sources. When connected to the 240VAC from the inverter, energy can be supplied directly from the AC panel sources as well as from DC panel sources, through the inverter or from stored battery energy, through the inverter.

There is a certain satisfaction of recharging from OFF GRID solar power. This offsets the darkness of petrol consumption on a longer trip. The PHEV has essentially increased the productivity of my OFF grid solar system, by reducing the lost energy yields, [the difference between my solar production capacity and the house consumption]. I have extended this concept to include house heating and cooling with a reverse cycle aircon, to further extend the solar productivity. There is a six fold difference in the solar yield between the seasons and during summer there is generally a big surplus. The PHEV and aircon can be selectively used to better match the loads to the potential solar energy yield. This is obviously a seasonal and daily effect, with less benefits in deep winter, or deep cloud cover. Generally, it is only wet, heavy cloud days when the PHEV misses out on a recharge. Don't tend to drive much on those days, so can generally still match loads to potential solar yields.

BTW these days, with readily available and cheap solar panels, that trackers, with the inherent mechanical systems with servicing needs and weather restricting designs, work out more expensive. The fixed panel designs can easily be made to fit in with architecture. ONLY If space is very limited, and neighbors don't mind a moving object on your roof, or in your garden, then a tracker may be an option. I have panels on every roof aspect of my home, and have only 3 panels in about 10kW tilted to the north on a fixed frame that is not parallel to the roof.

The CSIRO in AUS, extensively tested solar panel yields at differing orientations over a year. A solar panel that is fixed vertical and is facing away from the sun, over a year still produces 25% of a fully optimized fixed panel facing the sun. A dual tracked panel can produce almost double the energy of a fixed panel over a day. A panel that is facing east, or west at approx 30deg is only about 15% lower yield than a panel facing north over the year.

A fixed solar array generally averages 4-6kWh per kW of panels per day over a year in AUS, and a tracked array may produce up to an average of 10kWh per day per kW. Remember that this is average. The range may be 1-2kWh per day in winter to 14-15kWh per day in peak summer. The shorter days and low sun angles in winter at higher latitudes are cruel. Wheras the longer days and high sun angles in summer provide an extended bonus.

I have only used GRID recharging away from home, and in over a year now is still less than 10 times. Many thought I would not be able to recharge my PHEV OFF grid.

Just seen a new posting.

My AC coupled solar has 2kW of micro inverters, and a 1kW string inverter as well as 1kW of parallel LV single panels. The DC coupled solar has 1.5kW of amorphous panels and 2kW of poly panels.

 

[Ozukus]

My PHEV in AUS with supplied recharger PHEV requires at least 2.2kW of AC power when recharged from the AC cord.

gwatpe,

can you explain what you mean by that above sentence.

Cheers

 

[gwatpe]

My PHEV in AUS with supplied recharger PHEV requires at least 2.2kW of AC power when recharged from the AC cord.

gwatpe,

can you explain what you mean by that above sentence.

Cheers

The recharging cord supplied for the PHEV by MMC. The cord with the box with a relay and some LED indicators and control ccts with a white plug on the car end.

The AC power station that you plug into has to be able to supply at least 2.2kW, the maximum power that at least my PHEV draws when AC corded recharging on the supplied MMC recharging cord. In my case, the OFF GRID power station happens to be a 240VAC inverter connected to my 24VDC lithium battery. It has to be able to supply the required 2.2kW, in addition to what ever my house needs are at the same time.

There are some aftermarket cord variants that have variable maximum current settings, but I have the MMC standard cord at about 9.1A. NB power, kW and energy, kWh are not interchangeable.

 

[TomPHEV]

Ok, the PHEV's battery has a total capacity of 12kWh, which means that it can hold enough electrical energy to provide 1kW of power for 12 hours, or provide 12kW of power for 1 hour, or provide 6kW for 2 hours etc.

However the battery in the PHEV is never completely discharged, and the residual capacity of the battery is about 2 or 3 kWh, so a full charge from "empty" requires about 9 or 10kWh of electrical energy. Let's assume that to recharge the PHEV's battery requires 10kWh of electrical energy

(Remember a figure quoted in Watts or kW represents a POWER output or input, but a figure quoted in kWh represents an AMOUNT of electrical energy, or a CAPACITY of a battery)

Most domestic solar panels measure approx 1.6m x 0.9m and have a nominal maximum output of about 250 Watts, so you'd need 4 of these panels to achieve a maximum nominal output of 1 kW. Assuming you could connect 4 such panels to your PHEV, it would take in theory about 10 hours to recharge the PHEV's battery from "empty".

In practice, its not possible to charge the PHEV's battery directly from solar panels because the PHEV is supplied with a cable that plugs into a 240V AC supply and it draws about 10 Amps, which equated to 2.4kW. The output from the panels is DC and the voltage depends on how many panels you have connected together.

In the "real world" if you install solar panels on your house, they run through an inverter and are connected into your house wiring. If your panels produce more power then your house needs, the excess is exported out onto the grid. If your panels are not producing enough power to meet your power requirements then any additional power is taken from the grid.

So, to charge your PHEV using solar panels you would need at least 10 domestic solar panels (connected via an inverter) to produce enough power when the sun shines, and it would take between 4 and 5 hours to fully recharge your PHEV.

You could possibly run the panels via an inverter and connect them directly to your PHEV (but I'm not sure what would happen when the sun goes in)

 

[gwatpe]

You could possibly run the panels via an inverter and connect them directly to your PHEV (but I'm not sure what would happen when the sun goes in)

Panels via an inverter. :?: This is so vague.

There are many regulations regarding higher voltage DC. [>100VDC]. The PHEV expects to be recharged from a "GRID" AC power source in AUS. As long as this "GRID" can supply the power, then the PHEV will be recharged. Normally the "GRID" is the utility provided one, but if you can supply your own isolated from the utility "GRID", like from a battery inverter system, and it has a high enough power capacity, then the PHEV can be recharged from this as well. I have ample recharging resources from solar and windmill, and my inverter can supply the required power, but if I attempted to fully recharge the PHEV from the battery storage at night, this would deplete the usable energy for my house. I generally only recharge my PHEV in the day, to maximize the solar harvest, and minimize the drawdown in the house battery.

When there is a high power socket supplied in the PHEV, I would not be experimenting on that cct.

 

[Regulo]

You could possibly run the panels via an inverter and connect them directly to your PHEV (but I'm not sure what would happen when the sun goes in)

I think what Tom means is simply connecting the solar panels directly to an inverter and then to the PHEV ac inlet. When the sun goes in, no power available, as there's no battery storage connected. That'd be a bit hit and miss for my liking!

 

[TomPHEV]

What I am wondering is....

Would there be any way for me to only supply power to my PHEV when the output of my solar panels is above a certain level?

My solar panels are connected to the grid and when they produce more power than I need the electrical energy is exported to the grid (for a few pence per kWh). It would be great if there was some way to "dump" the excess electrical energy the panels produce into the PHEV's battery rather than export it.

 

[Regulo]

What I am wondering is....

Would there be any way for me to only supply power to my PHEV when the output of my solar panels is above a certain level?

My solar panels are connected to the grid and when they produce more power than I need the electrical energy is exported to the grid (for a few pence per kWh). It would be great if there was some way to "dump" the excess electrical energy the panels produce into the PHEV's battery rather than export it.

Tom, if your PHEV is connected to your house grid, the full output from your panels will be available to the PHEV. i.e. if your panels are producing 3kW and your house needs 1.5kW, the other 1.5kW will go into the PHEV, not back to the grid.

 

[gwatpe]

What I am wondering is....

Would there be any way for me to only supply power to my PHEV when the output of my solar panels is above a certain level?

My solar panels are connected to the grid and when they produce more power than I need the electrical energy is exported to the grid (for a few pence per kWh). It would be great if there was some way to "dump" the excess electrical energy the panels produce into the PHEV's battery rather than export it.

Tom, if your PHEV is connected to your house grid, the full output from your panels will be available to the PHEV. i.e. if your panels are producing 3kW and your house needs 1.5kW, the other 1.5kW will go into the PHEV, not back to the grid.

The example above neglects to include the additional energy the grid will need to supply to make up the difference that the panels produce to what the PHEV recharging system needs. This will be dependent on whether the std 10A, or tethered 15A cord is used. There is no way that only the surplus from the solar, component exported only, can be used to recharge. Some power from the utility grid will be needed as well, as no matter what size array, chances are that clouds will reduce the solar output to a point where grid power will be needed to balance the PHEV recharging needs.

 

[Regulo]

The example above neglects to include the additional energy the grid will need to supply to make up the difference that the panels produce to what the PHEV recharging system needs. This will be dependent on whether the std 10A, or tethered 15A cord is used. There is no way that only the surplus from the solar, component exported only, can be used to recharge. Some power from the utility grid will be needed as well, as no matter what size array, chances are that clouds will reduce the solar output to a point where grid power will be needed to balance the PHEV recharging needs.

Yes, sorry, I didn't elaborate that the 1.5kW would need to be supplemented from the grid, in that scenario. What I was trying to get across was the fact that all the available solar power is used for whatever consumption your house system needs, before any current is drawn from the main grid. This summer I did, on one occasion, fully recharge the car from my solar installation, without drawing anything from the grid. Doesn't happen often in Essex, England!

 

[TomPHEV]

There are power diverter devices available which will divert any excess power produced by your PV panels to a specific load (usually an immersion heater) but such devices would probably not be suitable to use to charge the PHEV because their output would vary according to the level of ambient solar radiation.

 

[kentphev]

I've seen devices that claim to be divert 'spare' PV power to, for example an immersion heater - but these were pretty expensive. Also that would still be a binary on/off rather than get the car and charger to adjust their charge rate to match spare power.

I've got a 3kW solar installation and so try to charge the phev during the day. This one reason why I opted to use the plug in charger that came with the car - will take longer but cost less as would import less from the grid. This means in Spring-Autumn I get largely free charging at home.

My company has been looking in smart micro grid systems and dont think there is much out there yet. One costly answer is to have Tesla style home battery - dump all your PV into battery and charge your car overnight.

 

[PeterGalbavy]

Solar PV diverters only work on resistive loads and they tend to vary the voltage - an immersion heater doesn't really care that the voltage is not 240V or whatever but will draw a similar current. A real electrician should step in and explain as I am not getting the terminology right and I am not reposting the marketing drivel I have seen.

Either way, isn't (yet) suitable for car charging.

 

[dexb]

Is there a reason the battery needs to be charged at high current (10A or more)? I have a car I use infrequently and would like to be able to charge it from panels I store inside the car (understanding that this may not always be sufficient and I may have to plug into the mains sometimes). This would be particularly useful when I visit remote areas, as I often do.

Is there a charging cable I can buy that would allow this, or is this a limitation of the battery itself?

 

[Sunder]

Interesting thread resurrect...

Anyway, in answer to your question, you actually have to realise that the "charger" that we have, is nothing more than a relay with a semi-smart "negotiation" control box. The real charger is inside the car. The control box tells the car what the maximum charge current it is permitted to draw is. So while our cars can draw 16A, our chargers will inform that car the max they can draw is just under 10a, and it will charge at the lower rate.

So if you could meet two conditions:

1. Build your own control box that is able to signal to the car that only "X" amps is available; and
2. The car's charger supports "X",

Then yes, in theory, you could buy or build a control box that draws a much lower current.

Personally, I wouldn't bother. Unless you are frequently at a place where you are very limited in your ability to draw power, then the amount of petrol you would save is unlikely to cover the cost of the charger.

 

[Sunder]

My mistake. See below:

The charging station can use the wave signal to describe the maximum current that is available from the charging station with the help of pulse width modulation: a 16% PWM is a 10 A maximum, a 25% PWM is a 16 A maximum, a 50% PWM is a 32 A maximum and a 90% PWM flags a fast charge option.[20]

https://en.wikipedia.org/wiki/SAE_J1772#Signaling

There is no option under the signalling protocol to indicate to the car that there is less than 10A available.

There would not exist any charger that draws less than 10A.

 

[anko]

My mistake. See below:

The charging station can use the wave signal to describe the maximum current that is available from the charging station with the help of pulse width modulation: a 16% PWM is a 10 A maximum, a 25% PWM is a 16 A maximum, a 50% PWM is a 32 A maximum and a 90% PWM flags a fast charge option.[20]

https://en.wikipedia.org/wiki/SAE_J1772#Signaling

There is no option under the signalling protocol to indicate to the car that there is less than 10A available.

There would not exist any charger that draws less than 10A.

Not a mistake

For example, the Charge Amps "Spark" Mode 3 charger has a 6 amps option and this works well with the Outlander.
As another example, the ELPA EVR3 charger supports even more levels: 6, 8, 10, 13, 16, 20, 24, 28, 32A (http://www.e-station-store.com/en/portable-charging-stations/36-evr3-type-2-max-22-kw-portable-charging-station.html). Of course the higher levels don't bring any extra value to us ...

I do not know if the protocol indeed supports values < 6 (best to Google a bit) and if the car would be able handle it. The Renault Zoe seems to have issues with low(er) charge currents.

 

[Sunder]

Not a mistake

For example, the Charge Amps "Spark" Mode 3 charger has a 6 amps option and this works well with the Outlander.
As another example, the ELPA EVR3 charger supports even more levels: 6, 8, 10, 13, 16, 20, 24, 28, 32A (http://www.e-station-store.com/en/portable-charging-stations/36-evr3-type-2-max-22-kw-portable-charging-station.html). Of course the higher levels don't bring any extra value to us ...

I do not know if the protocol indeed supports values < 6 (best to Google a bit) and if the car would be able handle it. The Renault Zoe seems to have issues with low(er) charge currents.

Ah, I guess the list was examples only and not exhaustive. I did think it was a bit odd, as I thought I had seen 6amp chargers before.

Good to know.