Investigating Lithium battery generators

[Benjahmin]

Now we're rockin' !
I looked at the Drift cells and was tempted but then realised they would only be good for my van and wouldn't charge my 3 bike batteries - well not more than once anyway.
As the van is the usual crap front wheel drive, and spins out when it even smells wet grass or mud, wild camping isn't really on, so campsites are the norm for us. This means hookup at around £5 a night and I'd have to do a lot of camping to cover the cost of a leisure Drift.
Here's the van just for entertainment:


It has a wheelchair conversion, hence the ramp, with a wheelchair well in the middle of the floor. We get the bikes inside and sleep on top. Great fun unless you need a pee at 3 in the morning.

So I'm back to looking at a house system. I would need a new consumer unit - well two actually. That way I could seperately power the downstairs sockets from their own board and this is the circuit that would be powered from the battery during a power cut, isolated from the grid of course.
This would need a 'smart' system so the panels would charge during the day (it's assumed I export 50% of what I generate) and use it at night. I probably can't get dual rate meter because it would have to be a smart meter and the cell phone signal around here is intermittant at best and I could do without that headache.
I have an old gits suspicion of so called smart stuff. It seems to me that anything so labelled ends up doing some pretty dumb stuff.

 

[Nealh]

I have sat down and done some more number crunching, the limited pv watts I was considering simply won't produce much for about 5 months of the year as we don't see enough good winter sun. Southern eu it makes sense.
Battery storage needs to be far greater then anticipated for winter usage and with little sun to top up they would be drained in a matter of days.
If the uk had a permanent off peak price per kwh across the board then havesting kwh's via batteries for day time usage may be workable but overall, I'm no longer convinced .
Simply the numbers just don't stack up imv nor does the payback in any savings.

 

[Woosh]

I think the baseline is to use the battery to buy cheaper electricity and use it in daytime. It is particularly suitable for small offices where computers account for up to £500 per person per year and heating is often electric.

 

[Nealh]

My priicng is the same 24/7 so no chance of being able to use any off peak rates.

 

[Benjahmin]

I'm also stuck with a one rate meter.
What also acts as an inhibitor to a system of buy night and use/export during the day, is the derisory unit price paid for exporting power. The current rate, on my FIT deal, for exporting is 3.5p/unit. This, set against a supply rating of some 27p/unit or more, demonstrates the mind set of the major power generating companies. As far as I can see, they do not want a system where micro generation plays a significant part. They argue that the infra structure can't handle it. What I think they mean is that, 'We can't keep control of it'. My house has a 60A main supplky fuse and the supply cables capable of handling that. Therefore, so long as I don't try to export more than 60A (not likely is it?), then where's the problem? Import/export meters in each property would track the flows and be payed/billed accordingly, with base load generation providing the smoothing.
If micro generators were paid a decent amount for what they export (say 40-50% of import rate), maybe more would look at having PV's as financially viable. Thus helping the potential power shortages we are looking at.
Why is it not a requirement under planning rules that every new build has to have PV's? Could it be that all the talk of carbon neutrality and energy independance is just hot air - probably emitted by a generation station !

 

[Nealh]

Exporting to a DNO is a waste of time for anyone with excess kwh produced, I would rather spend on a battery to keep the excess.
With an offgrid system one can do that much easier.

It is appalling and shows the contempt the DNO's have for customers with the piffling export rate then have the neck to charge the import whacking rip off rates.

I may change mind again and try a small off grid array at one expects for several months of the year one can have some free power, it's just the late autumn & winter regeneration that 's an issue with a small array. Get more summers like we have had ans even the early spring brightness then one should be able to deplete and recharge LFP with little problems if one can assume the LFP will be viable over 3 or 4 dyas before complete recharge occurs.

 

[Nealh]

Last week it was shell and now this week BP announce obscene profiteering due to price rises, yet goverment stay quite and offer nothing about bringing them to book.

 

[Nealh]

A few simple numbers.
My current price for elec is 0.35314p per kwh.
A 1600watt pv array supposedly will producefor my flat roof 1321kwh of energy.
Using those figures would equate to £466.47 in energy cost for electricity and say for a 3k outlay one would break even in 6.5 years.
Come April likely that electricty kwh will be some by some media comments over £1 a kwh and some quoting £1.175.

 

[Benjahmin]

With these supply costs, Nealh, I'm wondering about something similar to you. An independant pv array feeding a battery permanently connected to fridge freezers. It would need monitoring during short days during winter to ensure the battery wasn't being overly depleted.
Back to the calculator !
I don't have a garage and my kitchen roof already has the FIT array on it. But I do have a south facing single storey wall. Would vertically mounted panels work? Seems to me they would be good at low winter sun angles, not so good in summer when day length would compensate.
I know someone put up a calculator in an earlier post but I couldn't understand it.

 

[Nealh]

Was it me to linked to this one.
PVWatts Calculator (nrel.gov)

Also this is another one.
Solar Irradiance - calculate the solar energy available on your site (solarelectricityhandbook.com)

With the pvwatts calc open it up input your post code top left, use the map to pin point your exact location.
Select the RHS side bar orange arrow to enter the next page.
Infill the boxes with required info;

• DC size use kw array system size so for instance 1200w would input as 1.2 if only 900w input as 0.9.
• Module type. Std are polycrystaline , premium are the mono type like monocrystaline & monoperc's and thin film are the flexi type.
• Array type just select one of the first two options.
• System losses are avergae calculated o can be left as they are.
• Tilt degree ? Angle from the horizontal that the panel sits at 90 degree is not good, any summer collection will suffer by some 50 or 60% , winter collection is only slightly better so not worth considering in the whole as any summer collection is compromised.
• Azimuth is the compass direction the array will face so 180 degree for south.

Once info is input select the RHS orange arrow for the results.

 

[Nealh]

As an example where I live South facing isn't possible but if it were I would get the following results.
The first figures being 35 degree angle at 180 facing and the second figures vertical/90 degree angle both using 1.2kw array as an example:
Jan 40/44 kwh.
Feb 50/47 kwh.
Mar 80/61 kwh.
Apr 123/79 kwh.
May 150/78 kwh.
Jun 139/69 kwh.
Jul 149/77 kwh.
Aug 141/84 kwh.
Sep 104/77 kwh.
Oct 76/69 kwh.
Nov 42/44 kwh.
Dec 27/29 kwh.

Total generation 1125 kwh/ 758 kwh.

 

[Nealh]

One needs to work out the kwh one use per month or as a daily amount for the year.

Over the last couple of years my usage has been approx. 6.8kwh per day for electric use, so an average per month requires approx. 204kwh.

I have been more wary of prices and cost of energy and last month October my total monthly electric use was 108kwh or as low as 3.48kwh per day for the month.
Where I live for the flat roof mounting shading would cut any energy produced to very low values with the low sun from Oct to Mar.

 

[jonathan.agnew]

Was it me to linked to this one.
PVWatts Calculator (nrel.gov)

Also this is another one.
Solar Irradiance - calculate the solar energy available on your site (solarelectricityhandbook.com)

With the pvwatts calc open it up input your post code top left, use the map to pin point your exact location.
Select the RHS side bar orange arrow to enter the next page.
Infill the boxes with required info;

• DC size use kw array system size so for instance 1200w would input as 1.2 if only 900w input as 0.9.
• Module type. Std are polycrystaline , premium are the mono type like monocrystaline & monoperc's and thin film are the flexi type.
• Array type just select one of the first two options.
• System losses are avergae calculated o can be left as they are.
• Tilt degree ? Angle from the horizontal that the panel sits at 90 degree is not good, any summer collection will suffer by some 50 or 60% , winter collection is only slightly better so not worth considering in the whole as any summer collection is compromised.
• Azimuth is the compass direction the array will face so 180 degree for south.

Once info is input select the RHS orange arrow for the results.

Very useful, reggio calabria (south italy) in December, for example, gives 1.9kwh/m Square in December compared to 0.6kwh per m squared for same month in London (I live in both and never realised mid winter difference was that big)

 

[Nealh]

Battery storage needs to be huge for any winter use. It is handy from spring to Autumn as the sun would replenish them during the day with good sun for off grid, following the night time usage.

LFP 24v x 280ah is 7.168 kwh in my area with a near 2kw array for my spilt E/W azimuth the battery will need 3.6 sun hours per day to recharge from a 77% DOD.

No use having huge kwh storage if an array is unable to fully charge it, April to August would save some money but it is only 6 months for me. In the end it depends on array direction and total wattage.

 

[Nealh]

Very useful, reggio calabria (south italy) in December, for example, gives 1.9kwh/m Square in December compared to 0.6kwh per m squared for same month in London (I live in both and never realised mid winter difference was that big)

In southern europe it pays to have solar where the sun shines more.
The difference living at 38 degress longitude compared with 51 degrees for the UK.

 

[jonathan.agnew]

In southern europe it pays to have solar where the sun shines more.
The difference living at 38 degress longitude compared with 51 degrees for the UK.

Yes and oddly it really doesn't correspond with subjective experience - cape town's mid winter output (there june/july) is something like 2.6kwh/m per day, significantly higher than reggio calabria (and didn't feel it when I lived there years ago)
But, and this may not make obvious financial sense, I imagine living on say a standalone solar setup may go with greater awareness of consumed energy, becoming more frugal (say using a different fridge than the 20 year old dinosaur) and so work out cheaper (specially after april)