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Renewable Energy: Solar PV and cars

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    • CommentAuthorrevor
    • CommentTimeMay 14th 2019
     
    Having failed to get an EPC in time to gain from FIT, pressure now off, so in position to do a DIY installation. Don't really want to give the grid the benefit of my investment (Claire Perry seems to be dragging feet on this one) so thinking of a battery back up off grid system. Am also in the market for an electric vehicle and wondered whether I could use the battery on the car to serve both purposes. Guess possible but expect the specifying will be critical bit.

    Anyone got any thoughts.
    • CommentAuthorbhommels
    • CommentTimeMay 14th 2019
     
    Recently somebody told me the Mitsubishi i-MiEV has an emergency mode that allows it to power devices from its battery. The gizmo is available in Japan, where they have 100V mains voltage.
    The Wiki page on V2G has a few references to Nissans and Mitsubishis being capable of it. Nothing off the shelf (outside Japan) though. Electricnation.org.uk has some information on their 2018 trial.
  3.  
    A subject that I'm very interested in but also a bit confused about.

    Getting excess PV generation into your car seems pretty easy. Zappi car chargers seem to be well reviewed and have solar divert functionality.

    If you want to go the next step and get electricity stored in your car battery back into your home via a vehicle to grid or vehicle to home system it all seems to get more confusing (to me at least). I think we are basically in trial stages here in the UK. I believe you need a pretty new electric car too that can support charging your house (so you can't pick up a cheap old Leaf for example).

    Robert Llewellyn (Scrapheap Challenge, Red Dwarf) runs a YouTube channel about EVs and renewables called Fully Charged. He's having one of the trial systems installed in his house soon and said he'll make an episode about it so could be worth looking out for.
    • CommentAuthortony
    • CommentTimeMay 15th 2019
     
    I have an electric car and can charge on solar

    Battery charging is inherently inefficient so although it can be economic for an individual overall in energy terms it wastes some energy
    •  
      CommentAuthorfostertom
    • CommentTimeMay 15th 2019
     
    That matters less, if at all, if the energy source is abundant and 'renewable'. The imperative for 'efficiency' is vital when the source is fossil, for reasons of greenhouse gases and other toxic pollutants - but that reason doesn't apply to renewables.
    •  
      CommentAuthornigel
    • CommentTimeMay 15th 2019
     
    I am going down the full EV shortly and I am going to extend my PV from 3kWp to 7kWp.

    Zappi and EDDi will be used to use as much as practical and then you can export the excess using someone like octopus energy who will pay 5.5p per Kw.

    They also do an agile tariff that uses half hour rates so you pay the market rate and therefore charging at night is cheaper.

    So most of the daytime use is covered by PV and night time at reduced rates on Agile tariff and the EV can be topped up at night at times when there is insufficient solar. At times the night time tariff can be as low as zero and more often than not no more than the export rate your are paid.

    Battery technology is too expensive at the moment and I think its better to use the grid as your battery store.
    Batteries are also energy intensive to make so consider the embodied energy in their manufacture and later recycling.
    • CommentAuthorbhommels
    • CommentTimeMay 15th 2019
     
    Posted By: tonyI have an electric car and can charge on solar

    Battery charging is inherently inefficient so although it can be economic for an individual overall in energy terms it wastes some energy


    True, although for Li batteries the round-trip efficiency can be as high as 90%. And the electricity grid is not 100% efficient either.
  8.  
    If someone stores solar by charging a car, then discharges it to power a house, will that charge/discharge cycle use up a bit of the lifecycle of the car battery and hence of the car itself? IE they buy an expensive car but it has only a short useful life before the battery gives up. How will the financial/environmental cost of that compare to the solar energy value?

    Alternatively could you buy an old/bashed electric car, park it in the garden and use it as a home battery?
    •  
      CommentAuthordjh
    • CommentTimeMay 15th 2019
     
    Posted By: WillInAberdeenAlternatively could you buy an old/bashed electric car, park it in the garden and use it as a home battery?

    That's what a Tesla Powerwall is, AIUI. Other manufacturers are also moving in that direction.
  10.  
    Posted By: WillInAberdeenIf someone stores solar by charging a car, then discharges it to power a house, will that charge/discharge cycle use up a bit of the lifecycle of the car battery and hence of the car itself?


    I'm not dismissing this as a concern, but I'm not sure how big an issue it is. Car batteries are lasting longer then people expect. All of the car manufacturers quote prices for replacing batteries but I heard 4/5 months ago that none of them had actually ever done a replacement. There are some pretty old Nissan Leafs out there. I've also read reports of an electric taxi in Cornwall that had done 150,000 miles and had 90% of its battery capacity left. As this is such a new area, more research is probably required.
    • CommentAuthorCWatters
    • CommentTimeMay 15th 2019
     
    One way I can see this being useful is to mitigate the evening peak surge in demand. eg people arrive home and plug in their car, instead of charging the car helps the grid over the evening peak. Then later the car starts recharging.

    If that's what happens in practice then I guess the effect on the battery is slightly deeper charge/discharge cycles rather than more cycles. Deeper discharge cycles are known to reduce the life of some li-ion cells.

    Will lease/rental companies allow such use if it wears out their asset faster?
    • CommentAuthorphiledge
    • CommentTimeMay 15th 2019 edited
     
    <blockquote><cite>Posted By: fostertom</cite>That matters less, if at all, if the energy source is abundant and 'renewable'. The imperative for 'efficiency' is vital when the source is fossil, for reasons of greenhouse gases and other toxic pollutants - but that reason doesn't apply to renewables.</blockquote>

    Whilst solar energy may be abundant, the PV electricity isnt abundant and we're still totally reliant on fossil fuels. Only time renewables may be abundant is in the dead of night when wind may be enough to meet base load demand and maybe have some spare for car charging.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 15th 2019
     
    That's true for now - I was just encouraging clarity as to precisely why efficiency is vital now, so that we can keep an eye open for it getting less important.

    Certainly, reducing demand due to efficiency will shorten the time to when its curve crosses the curve of rising abundance of renewable electicity, esp solar, tho wind is taking the headlines at present.
    • CommentAuthorrevor
    • CommentTimeMay 16th 2019
     
    Thanks everyone found out lots today particularly from mentions by nigel. Been on Octopus did not know anything about them but it looks just up my street. followed the Zappi mention and came across this Robert Llywellyn video fully charged mentioned earlier by richardelliot
    https://www.youtube.com/watch?v=0EtegQfZQRw. Made me think of a small wind turbine also as have plenty of wind where I live would not have to be particularly powerful when combined with all the other stuff.
    This followed from the first video https://www.youtube.com/watch?v=nWLzlrGGuxQ.

    Interesting concept buying and older EV for the battery could have mileage.
  15.  
    Posted By: revorInteresting concept buying and older EV for the battery could have mileage.


    I'm not an expert, but I'm not sure an older EV will give you what you want? You can definitely divert excess generation into a car battery and get some 'free' driving miles, but I think you'd struggle to get the electricity back out again (especially when it is an older car) to create a backup off grid system.
    • CommentAuthorborpin
    • CommentTimeMay 25th 2019 edited
     
    If you are after a PV diverter then this appears to be a very good solution - I know of quite afew folk who have one.

    https://mk2pvrouter.co.uk/index.html
    • CommentAuthorborpin
    • CommentTimeMay 25th 2019 edited
     
    Posted By: fostertomThe imperative for 'efficiency' is vital when the source is fossil
    The more efficient you are, the less fossil fuel is used no matter how much the use of fossil fuel is reduced again by the use of renewables.

    Posted By: philedgeWhilst solar energy may be abundant, the PV electricity isnt abundant and we're still totally reliant on fossil fuels.
    Well no, a lot of the energy we use is via nuclear.
  18.  
    Remember that only a small part of overall _energy_ usage is delivered by _electricity_ .... PV and nuclear are still a small part of this small part!

    https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/728374/UK_Energy_in_Brief_2018.pdf
      Screenshot_20190525-204015.png
    •  
      CommentAuthorfostertom
    • CommentTimeMay 26th 2019
     
    Where do renewables show in that chart?
  20.  
    Renewables are part of the light blue 'primary electricity' bar, which includes nuclear hydro PV and wind. Also the dark blue bioenergy bar. Check out the gov.uk link, might interest you

    Edit: there is a table showing "Proportion of UK energy supplied from low carbon sources".
    It shows : nuclear 7.9%, bioenergy 6.4%, wind 2.2%, solar 0.5%, hydro 0.3%
    • CommentAuthorphiledge
    • CommentTimeMay 26th 2019
     
    I thought we were up to around 25/30% renewables, but still totally reliant on fossil fuels
  22.  
    Phil, you're maybe thinking of just electricity, which is only one part of the energy supply. Overall energy consumption also includes heating (mainly gas), transportation fuel (mainly oil), etc.
    • CommentAuthorphiledge
    • CommentTimeMay 26th 2019
     
    Yep, just electricity hence earlier comments on PV.
    • CommentAuthortony
    • CommentTimeMay 27th 2019
     
    My question still is can we as a nation afford to waste 10% on charging and discharging batteries?

    NO
    • CommentAuthorborpin
    • CommentTimeMay 27th 2019
     
    Posted By: philedgebut still totally reliant on fossil fuels
    No, Nuclear is not a fossil fuel so not 'totally' reliant on fossil fuel.

    Posted By: tonyMy question still is can we as a nation afford to waste 10% on charging and discharging batteries?
    If you are generating all of the required energy by renewables (including any extra required for battery storage), then yes. Even with the overhead of efficiency loss due to charge/discharge you would still be de-carbonizing the generation process by generating power, via renewables, that cannot be used immediately and so has to be stored. Obviously the ideal is a battery that is 100% efficient, but even a 10% loss through charge/discharge is more efficient than a fossil fuel ICE in a vehicle no matter how the electricity has been generated (IIRC).
    •  
      CommentAuthordjh
    • CommentTimeMay 27th 2019
     
    Posted By: tonyMy question still is can we as a nation afford to waste 10% on charging and discharging batteries?

    What's your alternative?
  27.  
    re diveter Ive fitted quite a few solar iboost+ with 2 swtiching circuits which Ive found handy.
    • CommentAuthorjamesingram
    • CommentTimeMay 27th 2019 edited
     
    Nigel
    "Zappi and EDDi will be used to use as much as practical and then you can export the excess using someone like octopus energy who will pay 5.5p per kWh.
    They also do an agile tariff that uses half hour rates so you pay the market rate and therefore charging at night is cheaper."
    there's been a few issue with smart meters and PV , i hope theyve sorted this.
    •  
      CommentAuthornigel
    • CommentTimeMay 27th 2019
     
    From the smart meter website;

    How does the smart meter record energy generation if a solar panel is installed?
    All the smart meter meters will record the export and import separately, and you will be able to see the readings by stepping through them on the meter display. All the meters should show all 4 power quadrants. You can ignore the reactive ones and just look at active import and export.

    Power quadrants:
    Active energy import (Wh) - this is what we are billed for normally
    Reactive energy import (varh)
    Active energy export (Wh) - this is your useful export power
    Reactive energy export (varh).
    If you have just the one meter it will measure the net energy consumption, i.e. just your surplus export.
    The bad news is that many companies have not set up their systems to automatically collect or use the export information, as it would have taken time and money they don't have for such a low volume user base.

    Depending on the supplier it should not be an issue but Octopus must be using the smart meter to do half hour billing anyway.
    •  
      CommentAuthordjh
    • CommentTimeMay 27th 2019
     
    Posted By: nigelFrom the smart meter website;

    I take it you mean: https://www.smartme.co.uk/technical.html

    If you have just the one meter it will measure the net energy consumption, i.e. just your surplus export.

    I don't understand this bit. Surely if you have just the one meter it will record four quadrants as just described? And net energy consumption is not the same as surplus export, it's exactly opposite.

    The bad news is that many companies have not set up their systems to automatically collect or use the export information

    Isn't the main issue that your supply contract and export contracts are completely separate? Mine are with different firms for example. I haven't read the rest of the page yet to see how, or even whether, that's dealt with by a smart meter.

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