Unthreaded
A screenshot from an NDA'd manufacture specification document from a few years back.... (provenance obfuscated to protect the guilty)
Half battery pack capacity gone after 4 years..... no detail charge / discharge regime specified..... - so one might assume it's best case?
Robert - you can only synch to what you can "see" at the connection terminals. The usually quoted timing mismatch is 4ms or 1/4 cycle (for small UPSs) but as can be seen from that demo video (I think) is that once coupled the grid and generator can go back an forth
https://fenixbatteryrecycling.com/ makes a quite interesting read if you're curious about battery recycling....
tomo
A fire at a battery recycling plant in Ayrshire. There are a few question marks about how good for the environment all these green ideas are, but I have to admit it's quite festive with the rosy glow and individual cells shooting off like skyrockets.
Could do with some of that warmth here.
Robert Swan
tomo,
That crispy fellow was trying to nick the copper, but the same Darwinian selection mechanism might be in play for siphoning from EVs.
I liked your choice of video to demo grid synchronisation. I think I've previously posted my own favourite which does less to explain, but is quite exciting: hooking up a 350kW hydro station.
Just musing on it, the seat of my pants tells me a couple of things:
1. There's no way to have an independent synch reference for an arbitrary position on the grid (atomic clock or whatever).
2. It's impossible to synchronise an arbitrarily meshed grid.
1 comes because of propagation delay; the AC signal works its way up and down the line somewhat like tides around the coast, so in addition to a universal time reference, your location would need a propagation time offset.
2. comes from the fact that a typical mesh would have different propagation delays along the multiple paths between pairs of nodes.
I think it's preferable that these problems are sorted out as they are at present: empirically. At any node, I am obliged to synchronise with whatever is on the line already. It's imperfect, in the sense of an atomic clock, but flexible, with no "master". A bit like the internet.
Robert Swan
Mike argh!
I typed up an explainer that I tweaked to a point I was pleased with it - and lost it.... grrrrr....
Grid tied solar is exactly that - the DC to AC converter (the inverter) uses the grid sinusoid voltage as the definitive timing reference for the power electronics, - no mains =no worky, end of. It's less of a cost issue in recent years to implement island operation but originally the extra hardware component cost was driving the implementation - nowadays it's more about control strategies vs. cost.... switching to local operation requires that the grid be disconnected (usually with an air gap) and the conditions to reconnect are strictly regulated.
I'll pontificate a bit later.
This demo is worth a watch.
"repurposing EV batteries" is a cul-de-sac filled imho with buyer remorse. The chemistry of batteries isn't particularly forgiving and I've yet to see one that got better over time - a water leak that stopped itself.... The service life of cells can always be enhanced by not charging to maximum cell voltage and never fully discharging them. As any owner of puffed up LiPo pouch cells can attest, cell electrolyte plays a significant role in durability....
Any system that disconnects and reconnects to the grid has to conform to the principles seen at work in the video.
tomo
tomo; apologies if I'm being thick but why would a generator be any different to a solar array wrt grid connections, etc? OK, 13 kW is bigger than most solar systems but they both produce 240v AC.
Is it something to do with the mechanical nature of a genny, needing to get things "in phase" as power stations do, whereas some electrickery can do that for the DC output of solar panels? Such kit must exist for things like small-scale hydro.
Quite a few commentors on the EV forums I visit have solar panels, often with batteries. Export does not seem to be a priority for them, probably because the rates are rubbish, as you say. Many charge their EVs during the day, if they can and then top up on cheap overnight tariffs. They also use their batteries to time-shift their consumption by charging overnight for use in the day. Clearly an export-enabled EV would help with this as EV batteries are typically much bigger than domestic systems - hence the idea of "re-purposing" old EV batteries for home use. However, as you say, battery life is a consideration since it is influenced by the number of charging cycles.
MikeHig
Mike
I should've been more specific ... the grid synch I had in mind was a generator rather than solar... see page iv of the linked doc.
I looked at installing a grid connected mains gas fuelled generator (literally half priced electricity + oodles of free heat 13kW 3ph electric + ca. 25kW heat) and explored that....
Export rates farcically low, I didn't find a single approved automated synch+connect and export control / monitor box.
I've *not* exhaustively researched "island" operation in power fail on solar - but I have now seen a lot of solar inverters and it's not a feature that I've seen in the docs to run during a mains supply cut....
The feature might best be implemented using an online UPS architecture - only last week I looked at a "hybrid" battery solar system and the operation required a mains supply at all times... it also prioritised grid export over battery charging.
tomo
tomo; in your post about V2G you said:
"Even though it's been talked about for what, 20 years+, there is still no agreed, widely recognised standard for grid synchronisation that allows for net metering"
I am probably misunderstanding but isn't this well-established for roof-top solar?
On that subject, am I correct that domestic solar shuts down during a power outage for H&S reasons unless there's extra kit fitted which isolates the house from the mains, allowing it to continue running on solar - if it's working, obvs. Siad extra kit is not cheap, aiui.
MikeHig
Battery siphoning eh?
Got to expect some Darwinian action in that department.
tomo
Robert
Bah... timer timed...
Hopkins is indeed one of my favourite characters in the FDR regime. He was a cunning and resourceful operator. Without revisiting the rabbit hole of his rise through the New Deal and links to Comintern and associates who were more open about their ideological allegiances - his (undisputed) reaction to a Major Jordan opening cases of nuclear documents, engineering parts and nuclear material samples in mislabelled crates which were being transported as air freight under Hopkins's personal mandate (as FDR's #2 / deputy) to was what really got my attention. When you compare Hopkins's travel in both directions between USA and USSR to other travellers and events, circumstances indicate he was a very important player. Any discussion of Hopkins triggers evasiveness from US establishment sources - they are likely quite relieved that he expired when he did.
tomo
tomo; Robert: thanks for those videos - tricky business!
It's going to be interesting to see how the whole V2G thing pans out as it's nowhere at the moment, afaics.
It's often touted as part of the solution to backing up wind and solar but there's a scale problem. If we take some silly numbers, say 5m EVs each able to supply 30 kWh to the grid, that's 150 GWh. Spread over just 24 hours of a hypothetical dunkelflaute that equates to a little more than 6 GW. Yet, without gas and with almost no nuclear, the grid shortfall could easily reach 20+ GW.
Imho, V2G is a mirage.