off grid power, modern times, for LLP

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off grid power, modern times, for LLP
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dpack

Joined: 02 Jul 2005
Posts: 46233
Location: yes

Posted: Tue Jul 25, 17 12:23 am Post subject: 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

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

it isnt easy, but it can be done.

i will have a look for suitable info sources asap

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

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Tue Jul 25, 17 1:20 am Post subject:
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

Joined: 31 Oct 2005
Posts: 3467
Location: Doha. Is hot.

Posted: Tue Jul 25, 17 3:36 am Post subject:
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

Joined: 21 Jul 2011
Posts: 15981

Posted: Tue Jul 25, 17 6:21 am Post subject:

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

Joined: 13 Oct 2006
Posts: 6521
Location: Dordogne

Posted: Tue Jul 25, 17 6:59 am Post subject:
Thanks all - good stuff. Any linky's that I can point people to is great.

Hairyloon

Joined: 20 Nov 2008
Posts: 15425
Location: Today I are mostly being in Yorkshire.

Posted: Tue Jul 25, 17 7:40 am Post subject:

Shane wrote:

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.

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

Joined: 19 Sep 2011
Posts: 787
Location: Mayenne, Pays de Loire

Posted: Tue Jul 25, 17 8:35 am Post subject:

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

Joined: 02 Jul 2005
Posts: 46233
Location: yes

Posted: Tue Jul 25, 17 10:47 am Post subject:

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

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Tue Jul 25, 17 10:57 am Post subject:

This stuff is starting to get adopted over here: https://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:
https://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

Joined: 31 Oct 2005
Posts: 3467
Location: Doha. Is hot.

Posted: Tue Jul 25, 17 11:12 am Post subject:

Slim wrote:

This stuff is starting to get adopted over here: https://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

Joined: 02 Jul 2005
Posts: 46233
Location: yes

Posted: Tue Jul 25, 17 12:05 pm Post subject:
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

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Tue Jul 25, 17 12:17 pm Post subject:

dpack wrote:

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

Joined: 02 Jul 2005
Posts: 46233
Location: yes

Posted: Tue Jul 25, 17 12:19 pm Post subject:
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

Joined: 05 Mar 2006
Posts: 6612
Location: New England (In the US of A)

Posted: Tue Jul 25, 17 12:22 pm Post subject:
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

Joined: 02 Jul 2005
Posts: 46233
Location: yes

Posted: Tue Jul 25, 17 12:29 pm Post subject:
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.

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