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dpack

off grid power, modern times, for LLP

as suggested and as it is a big subject i will start off with your power tool example

pv and a storage battery with an inverter to give 240v ac is an apparently simple option, however:

pv panels are getting better in both efficiency and price
battery storage ditto.
good so far

any change in voltage or from ac to dc or visa versa entails an energy loss
from source to load wastes lots of energy so source has to be bigger than the expected load

an ideal system creates power at the correct voltage and as ac or dc depending which the kit requiring that power uses

this is unrealistic as:
most kit is designed for mains voltage input or to be powered at it's demand voltage via a "power supply" that has a transformer ( transformers need ac to work, see inverters) and also converts the supply from ac to dc which then charges the battery or a transformer that delivers a suitable ac voltage via wire to the motor
ie kit has a variety of at "point of use" voltages and can be designed for ac or dc

re power tools, mine range from 240v ac (uk mains), 36v, 28v and 18v dc (battery charged via their 240 ac input/ kit voltage dc output charger units) and i have had a lot of 110v ac kit (mains via transformer and cable supply )

a practical "in the woods" system to use most kit must provide 240v ac for the assorted power supply units which come with the kit and "eat" that 240v ac to then "feed" the machine's battery with the correct dc voltage or to give a suitable ac voltage and amperage via a wire

from source to use this can involve losses of over 50% just to provide the correct voltage and type (ac/dc) inside the machine
ie any generation rig needs an output greater than the expected point of use load

next there is the ac/dc issue
there is a power loss converting ac to dc or dc to ac
inverters for either direction use power
see rig size above Wink

PV is always dc,
PV is daylight only and daylight varies so storage is usually essential

storage in a battery is always dc

most other leccy production things involve movement of a generator and so could be set up as either ac or dc
depending on type they might need storage that means dc at a suitable voltage for the battery rig ( a constant powersource might need no storage )
they often need a voltage conversion to give 240v ac for practical purposes storage or not.

this isn't getting any easier to explain Rolling Eyes it isnt easy, but it can be done.

i will have a look for suitable info sources asap Wink

ps any windmill under semi industrial scale is a toy and probably an expensive and disappointing one at that.

pps i know why we didn't bother with power tools in the woods, charging a phone is easy, high load stuff isnt Laughing
Hairyloon

In my experience, the bigger problem with inverters is that peak loads tend to trip them out: most motors pull a lot more current at startup, or if they snag, than their rated power might suggest.
I can run my angle grinder off my inverter, but only if I start it at a slow speed and use it gently, otherwise the inverter trips over.
Shane

Talking of domestic power generation and storage, this is a potentially interesting development: Linky

I think I mentioned on here blimmin' ages ago that (in my opinion) the obvious solution to the UK's long term power supply is to have as many premises as possible generating and storing energy and feeding into one, huge, supergrid.
Mistress Rose

We do seem to be going towards the small generation by a lot of people Shane, which is a good thing if the energy can be stored. I know I am cynical, which is very sad, but I am afraid that report doesn't inspire me with confidence that the government either know what they are talking about or that it will get done. To do so the financial investment needs to be there, and they are not putting that in, or encouraging it by other sensible means, and the overall 'smart' idea is a bit pie in the sky. Thinking about it, the only white goods I can choose to run while we are not at home are the dishwasher and washing machine, which wouldn't be worth the expense of setting up a smart system. With recent hacking attacks, this sort of remote programming is looking increasingly unattractive as well.
Lorrainelovesplants

Thanks all - good stuff. Any linky's that I can point people to is great.
Hairyloon

Talking of domestic power generation and storage, this is a potentially interesting development: Linky

I think I mentioned on here blimmin' ages ago that (in my opinion) the obvious solution...


I agree: totally obvious. Though possibly because you suggested it so long ago (though I do not recall that), or possibly because my wiring is aberrant and many things seem completely obvious, but apparently are not. Confused

Quote:
to the UK's long term power supply is to have as many premises as possible generating and storing energy and feeding into one, huge, supergrid.


It seems to me that the sticking point is payment: for example Richard is currently generating surplus so why can I not buy some of that surplus?
No, he has to sell it to the grid (for tuppence) and I have to buy it from the grid for 14.9p.
What happened to this "free market" that they keep banging on about?
I feel another letter to my MP coming on...
Woo

There is a new way here in, (Gulp), France.( i believe eu ish.....) if you generate your own power you can sell it to the grid if desired for the same cost as your current tarif. they provide you with a grid tie meter... but of course that means that the companies who have made a fortune from 'selling the system' are loosing out. but the consumer end user benefits.
off grid is a constant challenge, what can we safely use before the inverter goes into fault? its a brave new world, but it doesnt cost the earth, i hope.
dpack

various folk have mentioned issues that arise from the ratio of supply (from source via inverter/transformer ) to load size

the use of a national (or local ) grid as a buffer (battery) or as a means to sell surplus due to supply being out of timing with load is expensive 2p to 14.something is quite a loss to the home generation owner.

battery units have been expensive and/or huge and with a highish year by year cost in maintenance or replacement

new high efficiency batteries are becoming available
longer lasting and smaller is provided by modern li ion types (musk et al )
they are still quite expensive per amp hour stored and the average household might well need a few thousand £worth to cover the loads used for a few hours a day when required.
using timers on kit (washing machine springs to mind ) to time it so it uses power when power is being produced helps.

one side effect of the spread of electric cars is that the batteries for them need to be performing at "new" specifications to make the car practical so will be replaced when they are around 80 to 70% capable of storing their as new charge.
for domestic storage a 70% efficient car battery will still hold a lot of energy so storage rigs based on enough used car batteries will be a sensible option and replacing them (the recycling bonus might part offset the replacement cost but as li is common and quite cheap i would not count on it )as they eventually drop below the needs of a domestic system
it will be a few years before there are plenty of part used car batteries available but folk are planning large scale use of them for energy storage .
Slim

This stuff is starting to get adopted over here: http://products.greenmountainpower.com/product/tesla-powerwall/

Which is particularly useful as a rural state because there are areas that can go without power for days at a time after storms.

Also trying to smarten up water heaters:
http://products.greenmountainpower.com/product/ewater/

Edit: looked into the Aquanta a bit more. Seems like a good idea. Here's their own website: https://aquanta.io/
Unfortunately it's not compatible with a heat pump water heater like I'll be getting shortly.
Shane

This stuff is starting to get adopted over here: http://products.greenmountainpower.com/product/tesla-powerwall/

I'm keeping a keen eye on the Tesla roof tiles - my house in Blighty will need reroofing within the next few years...
dpack

the tesla powerwall is a decent bit of kit but most family homes might need two , one to cover the constant stuff like freezers, pumps ,domestic electricals etc and a second to cover tea parties, washing machines and the lathe in the shed unless those are timed well to avoid conflict of interest:lol: Slim

the tesla powerwall is a decent bit of kit but most family homes might need two , one to cover the constant stuff like freezers, pumps ,domestic electricals etc and a second to cover tea parties, washing machines and the lathe in the shed unless those are timed well to avoid conflict of interest:lol:

I think it can be done without the price premium for their brand and "all in one" package, but for more mainstream markets it's nice for people to have one item that they can identify and see as a plug-in component for their system
dpack

ps two would be good for a cloudy, windfree or drought week.
as they have a 5amp constant output one wont really cover big energy users or stuff with a high start up surge current (see industrial power tools etc)

as is often said reducing demand and especially peak demands is key to domestic off grid leccy.
Slim

Might it make the most sense to just have a gasoline generator for sporadic high demand usage? (power tools)

Is the power need somewhat temporary, as in to build a house, or constant, as in a home workshop that provides year round income?
dpack

in some ways the fred dibnah 19th c style steam engine driving a shaft and belt system is the best bet for off grid high energy power tools such as drills, drop hammers and lathes etc

for charging the batteries of building tools , rechargeable vacuum cleaners etc etc the tesla system would be ok so long as you avoided doing the washing at the same time as charging.
Lorrainelovesplants

help me with this guys!

So - you have the sun.
Running the equivalent of a 9kW electric shower.......from solar panels...

I found this bit of info on the web, but I dont really understand it...

Quote:
8 m² allows ~ 1kWp (Kilowatts peak) of PV system.
For most of the UK there are on average approx. 4-5 peak sun hours in summer going down to an average of 1 hour in winter.
For well sited grid connected PV arrays - 1kWp will produce ~ 800kWh (units) per year.
Installed cost for 3-4kWp PV system is approx. £6-8,000.00.
(this is probably out of date now)[/quote]

so - is 1kWp the same as 1 kW? Would I really need 93 square meters of electric solar panels to run a shower?
Lorrainelovesplants

DPack - can I just confirm I understand the first bit of explanation you did in this thread -

Unfortunately most appliances and power tools rely on mains voltage – 240V AC (alternating current). Sadly PV is always DC (direct current) and storing power in batteries is always DC. So this necessitates the use of a transformer or inverter to convert the load and lose a some power (can be up to 50%) whilst doing so.

is this correct?
Slim

Quote:
A kWp is the kilowatt ‘peak’ of a system. This is a standardised test for panels across all manufacturers to ensure that the values listed are capable of comparison. The test conditions for module performance are generally rated under Standard Test Conditions (STC) : irradiance of 1,000 W/m2, a module temperature at 250C and a solar spectrum of AM 1.5. This spectrum can be found here, but is unlikely to be of any interest to anyone outside the industry. Suffice to say that it is a standardised test.

When the solar PV panels are working they will over an hour convert the suns irradiance into energy, which is measured in kilowatt hours (kWh). A PV system with a kWp of 3kW which is working at its maximum capacity (kWp) for one hour will produce 3kWh.


http://www.evoenergy.co.uk/blog/18514/what-is-a-kwp-and-how-does-it-relate-to-kw-and-kwh/

To put it in a relatable manner, I have a 3.3 kwp system on my garage. It has never produced more than about 2.5 kw at any given time. I'm on the grid, so it's a bit different than what you're trying to figure.

Over the course of a day my system has produced between 3 kwh (a very rainy yesterday) to just under 22 kwh on a clear cool day in June.

Your 9 kw figure for hot water seems awfully high to me. Is that a tankless on-demand water heater? I think you'd want a tank to store heat (and therefore require longer time with less power, as a standard water heater only draws like 5 or so kw, or better yet a heat pump hybrid hot water heater. (or even more likely a gas water heater, as I think that's the most common for off-grid applications)

Electric water heat makes the most sense when you're on the grid....
Lorrainelovesplants

So a kW and a kWp are basically the same for comparison purposes (assuming its sunny and working at peak efficiency?)

This is really complicated.
Slim

Think of kwp as the sticker on a new car at a car dealership. It says that this car is capable of getting 25 miles per gallon, and that truck can get 17 miles per gallon. It helps you compare both vehicles/panels from different manufacturers on equal footing, even if it's not a true estimate of their real-world production.

I.E., when starting either vehicle from a stand still, you're really only getting a couple miles per gallon. Think of that as your hours of the day and days of the year where the sun isn't hitting the panels straight on.

Also, solar panels are more efficient in cooler temperatures, so even with straight on sun in the middle of summer they won't be operating at peak efficiency.

Edit to add: If you buy 10 panels that are rated at 330 kwp it's equivalent to buying 11 panels that are only rated 300 kwp.
It helps as you look at how many panels you can fit, and how much each panel (& installation) costs
Slim

We'd probably be able to provide better advice if we knew more about the motivations, and limitations, etc...

Is a grid tie-in impossible? (I don't know UK net metering laws, but over here I think it's preferable to be tied-in to the grid, personally)

Is this more of a philosophical quest to produce all of one's own power?

Is it about living somewhere that would be mostly inaccessible and therefore prohibitively expensive to be tied-in to the grid?

Over here there are plenty of off-grid folks that power most of their lives through propane. (lamps, refrigerator, etc....) That's not really the same as someone who's trying to reduce their carbon footprint.

If trying to go 100% solar with no grid back up, I would shift as much heating (living space and water) to gas combustion as possible, simply because it's impractical to attempt to store that much energy in batteries for long dark winter months.

I am on the grid with a good net-metering system, so I use the grid as my "battery". Right now we've got over $100 in credit from the power we've sold back to the utility, and we'll use that to make up for whatever electric we use in the winter months that we don't directly off-set with our generation in those months.
Lorrainelovesplants

So, all theoretical. Im doing a book and HAVE to include some stuff on self sufficiency.
Some of the stuff Im quite happy with. Some, Im very unfamiliar with.

So, rainwater harvesting, sand filtering UV treatment - yes - I understand it, I get it and can recommend it.
We dont have mains gas here (like a lot of Cornwall) so we have 2 heating & hot water systems that run independently.
The first is LPG bulk tank to a combi boiler and 8 rads. This gives HW and heat. Its quite expensive, but can be timed efficiently. We actually only use it in the mid winter.
The other system is a solid fuel woodburner with a back boiler which heats our main room, gives us loads of HW and also runs 5 rads. This is the system we use the most as our firewood is free.

I have to look at solar PV and discuss the options in the book.
I have to look at solar hot water (which I think everyone should do), and when we move imminently to France we will be doing.
Ive looked a little at ground source heat - Im not really up to speed on this, but it sounds good. I'd like to know more.

Ive just had a chat with John, who is more technical than me. He explained about solar electric, the inverters, the batteries etc.

I think my advice to anyone contemplating living off grid in a wood or on an island or whatever would be to forget solar, apart from running 12 volt lighting, possibly to power a pump for water, and to use an old fashioned range for cooking & heating, make the most of passive heat collecting windows (we have them in our garden room), and either having a borehole or filtering & treating rainwater.
Lorrainelovesplants

...and for people who want/need to use power tools or whatever, they will have to rely on generators, petrol tools (eg chainsaws) or pony power.
Depressing.
Slim

Just as a BTW, solar thermal hot water is no longer as cost effective as solar pv panels plus heat pump water heaters, and solar pv plust heat pump setups will likely get even more cost effective as the price of solar panels continues to fall. http://www.greenbuildingadvisor.com/blogs/dept/musings/solar-thermal-really-really-dead

The above example will likely give you some stuff to think about as you write....

OK, here I'm about to get rambly, but read on if you're interested:

I'm curious about your book and its aims. I try to blend greater self-sufficiency with greater community sufficiency, and feeding my excess solar electric production back into the grid off-sets the higher cost peak electrical demand for my municipal utility is part of that, as I see it. If I truly wanted to be self-sufficient, I could also purchase a tesla powerwall (or 2) which could theoretically store a normal day's power usage (or more) for me and have a grid disconnect wired up so that I can isolate my home from the grid in the case of an outage, but as I stated above, I'd prefer to not have that expense and help lower everyone's rates by supplying power approximately when our utility most needs it and has to purchase power from the wholesale market at a greater cost than they normally produce it (sunny summer days).

As it is, I'm having heat-pump water heaters installed for my apartment and my for my tenant's apartment (duplex). That will allow us to ditch the gas service for the tenant's apt, and reduce our own gas usage.
That would necessitate at least a second(third?) powerwall if I was trying to be completely off-grid, and possibly a third(fourth? - can't be bothered with that math right now).

I'm keeping an eye closer on the tesla solar roofs, as I don't have much other property space for more panels, and have a 100+ year old roof that will likely need replacing at some point. If that were the case, I would immediately yank out the gas heater that heats my apartment, put in a mini-split heat pump, and a couple resistance baseboard heaters as back-up/supplemental heating for the coldest months, and subsequently be supplying, or at least off-setting all of my power usage, and likely all of my tenant's power usage.

I see the above as self-sufficiency, and going carbon neutral (though my municipal power company is already 100% renewable electric). It may not yield as high a return as a traditional stock market investment, but I would be covering all of our heating, hot water, and normal domestic electrical needs, as well as a necessary roof replacement, and that would essentially be free after the needed loans are paid back (with no utility/heating costs from then on). It would likely be enough power to include all utilities in the higher rent from the tenant (and thereby pay back the solar loan faster) and likely would have enough power left over to provide for an electric bike so that I could ditch my car.

So, that's my grand on-grid self-sufficiency vision. Is that less self-sufficient than being off-grid? Clearly self-sufficiency can mean a lot of things, but if you're not looking to towards the future with a grid-tied setup like this, than aren't you just re-hashing what everyone else has said about off-grid living for decades? (i.e., thermal battery, passive solar gain, etc....)
Slim

Somewhat related, at least tangentially:

"climate battery" systems for greenhouses seem fantastic
http://www.ecosystems-design.com/climate-batteries.html

If I ever get around to building my own greenhouse, you can bet I'll be pursuing this. Possibly less effective at higher latitudes, but then again, you don't face the colder winters that we do.
Slim

Also, I keep bringing up Tesla powerwall units, but only because they're well known. Really I use that name as a stand in for any home battery bank option, of which there are many: http://www.businessinsider.com/rechargeable-battery-options-compete-tesla-2017-5 Lorrainelovesplants

The whole self sufficiency thing has been a large part of our lives.
We have always been thrifty, but wanted to live a simpler life, which isnt always easy when you have a mortgage, 2 kids and need transport in a county that really (really) doesnt do public transport).

We have a house with 1.2 acres, so whatever we did had to be pretty intensive as any number of livestock is really a non starter.
This site helped me loads when we started out, and Ive learned loads, and made some nice (and really supportive) friends.

We used recycled water to wash our apples and equipment when we made cider, tried to get community funded solar panels for our holding (just when the FITS thing collapsed here and the community interest company decided it wasnt feasible), installed the 2 heating systems to reduce our reliance on LPG. Replaced all our lights (inside & out) with LED's.

We downsized to one car, produced a lot of our own meat, eggs, alcohol, apple juice, fruit, veg and nuts. Ditched the tumble drier in favour of polytunnel drying in summer & pulley over the woodburner in winter.

As a FE teacher Ive run loads of courses on the stuff we do and other people want to learn. Its great that people care and want to make a difference.

We really do live very self sufficiently. Im proud of it. Im extra proud of my lovely son, who is at Manchester Uni doing Geography and wants to work in flood control and possibly drought prevention. He sings from the same book as me.

I was delightfully surprised and emotional when in 2014 I was awarded Cornwall Sustainability Awards Best Individual , and then at the start of this year I was asked to write a book on sustainable and profitable smallholding. And thats kind of where we are at the mo.

Apart from packing like crazy as we leave this house in less than 3 weeks!
Slim

A book on sustainable and profitable smallholding sounds great! (although perhaps a little insane when moving so soon! Shocked Laughing )

I guess I'm still not sure why the emphasis on off-grid situations & solutions then?

They aren't inherently more sustainable or more profitable just by virtue of being "off-grid"
dpack

DPack - can I just confirm I understand the first bit of explanation you did in this thread -

Unfortunately most appliances and power tools rely on mains voltage – 240V AC (alternating current). Sadly PV is always DC (direct current) and storing power in batteries is always DC. So this necessitates the use of a transformer or inverter to convert the load and lose a some power (can be up to 50%) whilst doing so.

is this correct?

yep, is the simple answer, why follows.

inverters convert between dc and ac and transformers convert ac voltage to a different voltage, they sometimes come in the same box eg 12 car battery to 240v ac

a power supply unit (charger ) might just convert dc to a different voltage eg 12v to 6v as in a car lighter charger for a phone
or might convert 240v ac to whatever v dc to charge the battery for something like a drill or a toothbrush.

motors are ac (either single or 3 phase, unless you have a semi industrial power supply dont worry about 3 phase stuff) or dc , whichever they are they will only work with the correct type of leccy (ac or dc) at the correct voltage for that design of motor

most uk stuff will require 240v ac to make it work either directly or by powering it's charger/power supply unit.
some stuff has a multi input power supply for mains 240ac or car 12v dc (and sometimes 110v ac )as the power source.

a few things can accept a different input which is another layer of complication

american kit is usually 110v ac so plugging it into EU 240ac supplies gets rather exciting

a rather neat trick is to check the specifications of a bit of kit as quite a few things have internal power supply units that plug into 240v ac but the working parts use a different voltage and perhaps use it as dc (pooters for instance) this does give some scope for avoiding inverters and going direct from a dc supply to the inside of the machine.
tis best to know what you are doing with this type of "make it work somehow" as out of service and on fire is easy to do Laughing

unless you want to become a mad max style electrical engineer it is best to get off the shelf kit that will provide 240v ac (110 in the us ) and either stores it domestically before turning it into ac or uses the grid as a storage facility.
the first costs more to install, the second costs more to run ( see 2p to 14 p as above ).
off grid you need storage for PV or wind but a constant flow of water could be considered to be it's own storage battery. a dam might be required( think small mill pond rather than hoover)

water is good so long as you have gravity and water,

it can be a lot (or a bit ) of water moving slowly or a bit (or a lot )moving fast.
various kit is available to suit what you have
archimedes screws and paddle wheels for low speed/pressure ie a stream on fairly flat land,
turbines for high speed/pressure ie a stream and a mountain.
water require quite a bit of engineering, dams ,races or pipes etc etc as well as the moving bits/generator unit.

again it can be mad maxed but that would be beyond most folk.

with water there is still the issue of converting what is produced to what is needed in terms of voltage and ac or dc

water isn't cheap unless you mad max it via scrapheap challenge, a pit and tarp up the hill etc etc
dpack

"They aren't inherently more sustainable or more profitable just by virtue of being "off-grid" "

very true but if you are off grid due to location or lack of reliable infrastructure diy leccy is rather handy
Mistress Rose

Thanks for the discussion. Very interesting. Lorrainelovesplants

The book thing came from me having a hard time after mum died (last Feb). I was told it would take a year and more to get over it, which it has. Ive only recently been able to go through her jewellery and her photographs.
This together with buying the house in France, the falling through and remarketing and selling of our house here, and stopping the business here - I was finding it very difficult to be idle.

So, some conversations on FB turned into an introduction, and that turned into a sample chapter and that turned into a publishing deal.

Ive written articles before for Smallholder and Country Smallholding, so the idea of a massive article was nice! Ive thoroughly enjoyed it.
My mentor, a fellow writer & journalist is the go-between, and so I have been asked to include a chapter on living off-grid as so many people feel its the only possibility for them to live in the country (basically because housing is so expensive). So, Ive tried to look at this in its broadest terms.
I do frequent many FB off grid sites. Lots of info on there, but depressingly large amounts of people looking 'how to live in a field anywhere between Heathrow and Devon'.

Ive written a lot on living with and lifting an ag tie, as this consumed my life for 10 years. Glad to have that out of the way.
And lots on just living lighter on the land, and making it pay - tons of good ideas- nearly all from fellow DSers or from smallholders Ive met through work at the Rural Business School.

I have 15 days till I move out of here and then no computer for a month, so trying to get as much down as possible. Im at 50,000 of a 80,000 word book. Laughing
Slim

Take out any contractions, and perhaps you will squeeze out an extra 1,000 words Laughing Lorrainelovesplants

I have a headache and a muscle ache in my right shoulder, so Im stopping for the day....
45,800 words.

Enough. Laughing
Slim

Last night I was dealing with the opposite problem as I attempted to get a 2,200 word "research note" closer to the 1,500 word limit.....

I got to 1,900 and am hoping they'll be okay with that amount fudging since that includes silly things like an abstract, references and acknowledgements!
Mistress Rose

Getting an article or book to the required number of words is difficult isn't it. I have a couple of potential books on the go, and neither is going anywhere near the right number of words. On the other hand, trying to fit a series of articles into a 6 page newsletter for our coppice group is sometimes tricky to fit it all in to look sensible if one article just overflows onto another page.

Your book sounds interesting Lorraine. Will be interested to know when it is published.
Lorrainelovesplants

Im actually finding the writing an excellent thing! Ive done stuff before for my thesis and for articles and reports, but the size is massive. Im shitting myself in case the computer crashes (a regular occurrence in our house), but am saving the book on two different mediums.

Im at 50,000 words now with 11 days to go till I pack the computer away. Laughing
Mistress Rose

Always best to save to at least one other place. We have a server in our house, so even the 'private' stuff I have, like partly written books gets saved there too. Otherwise, as you are doing, saving to 2 other mediums means you will only lose a small part if anything goes wrong. Lorrainelovesplants

so BG has decided to bump leccy prices up by 12.5%. Thats gonna make people start thinking about renewables surely? Slim

That's quite an increase. Definitely making the ROI on solar, etc. more favorable! dpack

it does swing things a bit.

the improvements in cost to output and especially in cost of storage combined with a high grid price reducing the time scale of ROI should make micro pv etc more attractive to more people

in global terms much like "wireless" phone and internet has bypassed a landline system for comms. in many places a "gridless" system for leccy might well do the same once the initial costs are affordable to local or global investors or better still to the folk who need leccy.
Mistress Rose

I think a grid system that small producers can put into is a better bet. My father remembered the days before the National Grid, and he said it was a really good thing. Remember before that, each town had its own power station, and those in the countryside often had nothing. dpack

not only did each town /city area have it's own supply there were many variations in voltage and Hz which meant that if you moved from say leeds to wigan you would probably need a new toaster and radio etc etc and even if ac/dc, V and Hz were the same in two places the plugs would be a different shape.

national grid = standardised equipment and with the EU wide standards the area and number of folk who all need the same equipment specifications gives considerable economy of scale

even using micro grid systems a standard for ac or dc, V , phase choice and Hz makes sense to avoid the need for both small and big(on the micro scale) transformers and inverters to standardise the outputs from rooftop PV, wind turbines up the hill, the high and low pressure water power units and the central base load/storage options to give a standardised point of use output .
unless every individual and/or community is to grow it's own tellies and lightbulbs to match their very rare type of leccy it is best they are using the same specs as all the other local grids Laughing

a variation on this theme is that different production methods work best when producing a certain type of leccy eg PV panels make lowish voltage DC and a turbine fed by a high dam might be most efficient making high voltage 3 phase AC. neither will make a telly etc etc work if you feed them in raw therefore it is important to plan for the losses of conversion .

a very rough guide to the ratio of supply (assorted specs) to load (universal spec note issues of 240v ac as a standard supply with transformers etc dedicated to specific electrical goods mentioned above) is that overall supply and storage/baseline/peak etc all need to be considerably greater than overall demand.
the details will depend on the kit and population density, distances, doing the all the maths in all the correct equations etc, etc .

one piece at a time and try to make it all work as a system is the road to madness for small community to city scale stuff ( tis pretty crazy for a stand alone system ) so "off the shelf" plug and play style packages such as those of buffet and musk that hit the market big and first are likely to become standard ( see windows/apple/pooter makers or the seven sisters/car makers etc etc ).
Mistress Rose

That is mainly true Dpack, but sometimes the largest players will get their system in regardless. VHS versus Betamax springs to mind, although Betamax was better.

Remembering computers from about 1970, the first one I saw was a terminal which must have been in excess of 10' long by 4' square, tended by a lady in a white coat, which took punch cards. When the smaller ones started to come along, it was very difficult to find a printer and a computer that would talk to each other unless made by the same manufacturer. This is the sort of thing that needs to be avoided with small scale, and which hopefully we worked through in the first part of the 20th century.

As an aside, husband rewired a house a few years ago that still had the old DC wiring in it as the local power station started by providing DC to a small area. Next came the early AC wiring which was losing most of its rubber coating, and then some patches of modern wiring.
dpack

it is true that the "best" system is not always the system which performs best in the market and therefore becomes the standard system, however be it "best" or not a standard system is a primary requirement for things such as leccy, ( vehicle fuels, ammunition sizes etc etc give further and slightly different examples of the principle ).
this gives scope for assorted makers to develop their products to use the "standard" consumable.

in the reality of a leccy production/distribution service there is a compromise in that a "standard" needs only to be applied to a few aspects of the overall system.
eg 220/240V rms, single phase, AC at 50 Hz at the consumer's 3 pin europlug socket that then can be attached to a wide variety of equipment with a standard 3 pin plug.
the various equipment then either uses power at that spec or converts it with it's own power supply unit/s to a form suitable ac/dc/V/hz/P leccy to power each component group.

iirc folk such as musk and buffet have taken this into account and their systems have been designed to give a "standard" leccy at consumer level to allow for the consumer to power the range of equipment available locally, this avoids the need for a vhs vs betamax style trade war and persuading folk to replace all their kit for new that matches a new standard ( whatever the standard there would still be the issue of the different types of leccy for different units/components of units )

returning to my supply to load ratio conversion costs, distribution costs and further conversion costs energy and any planned power system needs to account for needing considerably more energy input than the expected output.
ie for every watt of power used it takes more watts of renewable energy available for "harvest" to provide it

W out = W in minus losses therefore both minimising losses and ensuring the initial energy harvest is sufficient is important for any practical system.
there is little point in trying to convince folk they have to choose between lights, washing machine and freezers etc and charging the car.

minimising losses is a one piece at a time process but ensuring that W in is big enough to cover losses before it gets to W out is fairly easy as one makes/gets a bigger "harvester".

in practical terms the combined/simplified equations and numbers are available so as one can, for instance, decide how many PV panels and what size of battery you need in your location, for say, a 5 person off grid leccy supply for domestic and small holding use and to power 2 cars (500 miles per week ) and 3 bikes (100 miles per week ) etc etc .
the input will need to be surprisingly greater than the nominal combined outputs of the end user kit.
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