reality of solar power in the uk?

m6yru

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Sep 6, 2017
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here in "sunny" uk its never full sun except for about 3 weeks during summer lol... soooo

my ideas was to go big in tie-grid inverter but that since has been explained and is a bad idea!

My question now, as i have worked out the mean valueim using about 350w/h at 240v i was thinking of going small to just "offset" my bills...
now the reality of solar is that i wouldnt have the full power out of the pannel, if i needed to charge a bank of cells suitable to run a 350w tie inverter with a 24v battery pack, how many 100w at 12v solar pannels would i need...

i was thinking of only 6 hours of winter daylight and maybe running the tie inverter during peak power use,
how many amps would theinverter take off the cells when running at max (24v pack)
 
Ok first, even if it's never full sun, you'll get 85-90% of the power output of your solar panels during cloudy days. You'll just not get full peak power, unless it's full sunlight.

At 12V/100W per panel, you'd need 4 solar panels, as in 2 in parallel and 2 in series. If you could though, get a 2x24V 200W solar panel instead. You'll need less wiring, have lower power losses, and the setup is going to be less complex in general. Also, get a 600W inverter just in case you want to add a third solar panel. You won't regret it.

Finally, since it's a 24V inverter at 350W, you'd need about 15A off of the cells, which could easily be achieved with either 15 cells at 1A each in parallel. So no worries there.
 
BlueSwordM said:
Ok first, even if it's never full sun, you'll get 85-90% of the power output of your solar panels during cloudy days. You'll just not get full peak power, unless it's full sunlight.

At 12V/100W per panel, you'd need 4 solar panels, as in 2 in parallel and 2 in series. If you could though, get a 2x24V 200W solar panel instead. You'll need less wiring, have lower power losses, and the setup is going to be less complex in general. Also, get a 600W inverter just in case you want to add a third solar panel. You won't regret it.

Finally, since it's a 24V inverter at 350W, you'd need about 15A off of the cells, which could easily be achieved with either 15 cells at 1A each in parallel. So no worries there.

thank you for your answer, may i ask about the charge of the cells...
my question is that 4x 12v100w pv will only give 7amps at 85% (24v @170w) this wouldnt charge the cells if the 350w inverter uses 15a off them...
thats a hellotta pv pannels! just for only 350w inverter
 
15A draw on the inverter is the "Max" the inverter will draw when under full load. If you're running lights, you'll only draw around 2Amps or so. So unless you plan on running your inverter at full capacity all the time, you shouldn't have an issue.
 
Korishan said:
15A draw on the inverter is the "Max" the inverter will draw when under full load. If you're running lights, you'll only draw around 2Amps or so. So unless you plan on running your inverter at full capacity all the time, you shouldn't have an issue.

i was looking at a grid tie unit, thus it would use the full power :/

if i was to run lights i use LED and can run them from buck/boost converter...
my bedroom lamp 10w led is run from a 12v psu

there is only a few things i run continious that isnt 12v, laser printer, (cctv monitior) but the recorder is 12v...the laptop, this is an issue, the psu has a chip inside so it knows what charger is connected, without that data the laptop will supply power but not charge...

i am looking at making the other well used lights toLED but atm i got my lamp on an extension ;)
 
A grid-tie unit will put into the grid what ever power you don't use.

So, it wouldn't matter what size you had, it would draw as much as possible to feed back to the grid. Unless you can limit the amp draw it requires.

Just curious, if you use so little power, why would you want to use grid-tie? Seems like you would only need to use a regular inverter for a few devices that require AC.
 
A grid tie unit as such will tak all it can from the input and ouput. if it goes to your load or grid doesnt matter. it will just output it. So for grid-tie to solar it will send out all solar it can and what you use you use....

So if you dont want to sell to the company you need a 0meter system where it only ouputs what you use and not back-feed to grid. This is not allowed everywhere....
 
Korishan said:
A grid-tie unit will put into the grid what ever power you don't use.

So, it wouldn't matter what size you had, it would draw as much as possible to feed back to the grid. Unless you can limit the amp draw it requires.

Just curious, if you use so little power, why would you want to use grid-tie? Seems like you would only need to use a regular inverter for a few devices that require AC.

i worked it out over a few days that i use about 6kwh in 24hours... i devided this by 24 hours and got 250wph, then allowing for days i run other items like washing machine and tumble dryer i added on 100w per hour to try offset and ballance...
i use high current draw items like an electric shower but for only a short amount of time, however coming to the winter i will now n then use a 3kw heater when needed...


daromer said:
A grid tie unit as such will tak all it can from the input and ouput. if it goes to your load or grid doesnt matter. it will just output it. So for grid-tie to solar it will send out all solar it can and what you use you use....

So if you dont want to sell to the company you need a 0meter system where it only ouputs what you use and not back-feed to grid. This is not allowed everywhere....

i thankfully have a old meter and im not looking to "sell" them energy, just off set my own, as to say, make it look like my meter hardly turns lol...

i have asked this question in a different way and found that the 350w inverter will use ~16amps, so i will need a few pannels to be able to charge the batteries and use over night, however i cant have too many as i dont have the room.. come summer i might even need to pack them away too to allow for the vegies i plant to get the sunlight lol
 
If you take the majority of your loads off of mains and only leave on the heavy hitters (range, water heater, room heater) then you'd not need the grid tie. The meter will only turn when those items are in use.
I think you'd find the most efficiency in just using the inverter for small loads, forget about grid tie, and move all lower draw items to the batteries and have a transfer switch (either manual or automatic; MTS or ATS) to switch to mains if your packs voltage drops to low (or simply turn on a charger that charges the batteries from mains for a short while).

I think grid-tie is going to over complicate things and be more hassle than it's worth in the end. There's a lot of extra stuff you need for safe grid-tie operation.
 
Korishan said:
If you take the majority of your loads off of mains and only leave on the heavy hitters (range, water heater, room heater) then you'd not need the grid tie. The meter will only turn when those items are in use.
I think you'd find the most efficiency in just using the inverter for small loads, forget about grid tie, and move all lower draw items to the batteries and have a transfer switch (either manual or automatic; MTS or ATS) to switch to mains if your packs voltage drops to low (or simply turn on a charger that charges the batteries from mains for a short while).

I think grid-tie is going to over complicate things and be more hassle than it's worth in the end. There's a lot of extra stuff you need for safe grid-tie operation.

the most heavy hitting of the small loads id guess is the fridge when running, otherwise im going to guess it would be my `12v psu for all my stuff to run as this is continiously running...

the most of the house kwh's thats used is by the big hitters used for short time that adds up, so the shower would only be 0.5-1kwh in a day...

this is why in the beggining i was wanting to use a large inverter with a transfer switch to charge at night and use in the day for cost of poweris cheaper at night but to run such a large inverter and the quantity of cells with loss of economy.... but i thought as its winter im not growing any veggies so i could get away with a few PV pannels in the garden, sooo, echnomically i thought lets dump it all into the grid and use back what i have dumped....
 
so after working a few things out, i will need a 7s 30p minimum to run a 350w inverter off batteries giving only 0.5a per cell...

however that would be (approx using 2000mah cells) 60amps, that is then needing 10amps of solar per hour (equating for 6 hours of daylight) to charge +15 amps on top to run the inverter... total needed amps being 25, so at 24v i will need 600w of PV running 100%

i found this on a sales page for some PV pannels, this was the answer i was looking for....

image_cmcthe.jpg

pretty sad that where i live in the UK in spring/autum andwinter i could get only 20% out of solar... so even if i had the space for 600W of solar, id only get about 120w which is 5 amp....
at this rate i could run my LED lampfor about 12 hours off the batteries directly lol

the space i have for PV would only be 4m x 1m, spec of one pannel i see is99.6cm x66.5cm for 100w 12v... so i could squeeze 8 with some shading, thats only 400w at 24v and at only 20% of its power due to crap daylight here its only going to provide 3.3amps...

well its 8:30 am and its time to go to bed, all these numbers hurting my head
 
Are you set on using 12v panels? If so, why? Why 100w panels?
There are 24 volt panels availible now with more power and take up less area than the
four 100w panels.
 
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