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Author Topic: Advice needed over going full solar Electric  (Read 3152 times)
peterfc
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« on: June 23, 2014, 01:59:40 PM »

Hi All

After just getting my latest electric bill i am looking to  install a full solar system, Yingle panels 220/ 250w, batteries etc.

Could some kind person list all the bits i would need to turn my house full solar, i would not be looking to sell back to the electric company.

Thanks

Peter
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stephendv
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« Reply #1 on: June 23, 2014, 02:30:57 PM »

Hi Peter,

I see you're in Portugal so no access to those tasty UK feed in tariffs.  If you're doing this purely for economic reasons then going full off-grid might actually be more expensive than staying on the grid.
A good middle ground is to keep your grid connection but augment it with solar + batteries.  Whether this is permitted will depend on your local laws.  Whether full or partial off-grid the first step is understanding your loads, how many kWh do you use on a typical winter day, and on a typical summer's day?
Next, what is the maximum peak Watt draw you have?  E.g. hair dryer + borehole pump + AC all on at the same time, could be more than 5kW.

Once you have a handle on that you can then design the system to meet those loads, for a partial off-grid, where you maintain your grid connection you'd need:
- Solar PV as much as you'd like, preferably to cover your daily loads for at least 80% of the year
- Batteries to cover up to 1 day of loads
- Charge controller to charge the batteries
- Inverter/charger that sits between the grid and your house and will supply house power while the sun's out and batteries are full, or will switch to grid power automatically if the batteries are below a certain level.

Pure off-grid would be similar, except you'd need bigger batts to take you through say 2-3 days without sun.  And you'd need a generator to supplement power.  You'd then have 3 sources of energy (batteries, solar and generator) and to some extent you can decide to emphasise some over others.  E.g. you can install a smaller battery bank and decide to run the genny more often- but then you need a reliable fuel efficient gen.  Or you can decide to go for more solar, more battery and then get buy on a cheap emergency-only generator.  Really depends on your loads and how you're prepared to shift them in bad weather.
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billi
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« Reply #2 on: June 23, 2014, 04:17:10 PM »

Hi,

i would as well , first look at your local (Portugal ) politics and regulations !

Each country is different ! And layout the system clever , accordingly

As an example , Germanys FiT are down to close to 10 p  and the own  units you consume from your roof , will get  charged  (soon) ...


But , as Stephend described , there are several options .....

Mine would be , to get the right gear  , to  stay at least semi off grid or / later total off grid

As said , we need your consumption data  , to figure out your needs

Portugal seem a nice place to show a finger to utility companies ( unfortunately most  countries in Europe  have not  got the idea right , for us "selfproducers" , and integrate us )


I just looked here http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#

And a 4 kw PV -battery  -inverter  thing (like i have here ) would run our whole house all year round  (if transferred from Ireland to Portugal )

So please tell us your  needed kWh per year and day


Billi

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peterfc
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« Reply #3 on: June 23, 2014, 04:46:47 PM »

Hi Guys

Thanks for such helpful replies.

My usage will take me a little time to work out. For example i don't knwo the rating for my electric cooker so thanks and i will be back soon.

Here in Portugal there was a scheme where you had to buy a system via your bank if you wanted to sell back to the grid. That stopped a while ago. I intend to keep my power supply but not use any mains electric.

I have a friend full of grid and i will speak to him for help in getting my daily and yearly usage.

Thanks

Peter
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billi
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« Reply #4 on: June 23, 2014, 04:56:33 PM »

Hi Peter

Quote
For example i don't knwo the rating for my electric cooker
I would try to split electric cooking to 50 % gas  or just accept that only 5000 watt can be drawn  ( i would not go higher in respect of inverter and battery size )


You should know your consumption , cause you know your el. bill    Cheesy

CU
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stephendv
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« Reply #5 on: June 23, 2014, 05:03:15 PM »

I intend to keep my power supply but not use any mains electric.

Ok, there may be a third option: panels + device which prevents feeding the grid + grid tied inverter.  This is known as a self-consumption system here in Spain and used to be a grey area, but now you have to register and pay for the solar power you generate.  If this type of system is legal in portugal then it'll be cheaper than a battery based install, but you will only use solar power that's available that instant, i.e. all your night time loads will come from the grid.


Battery based will give you more independence and you'll be able to use more of your own generated power, but will work out more costly.
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« Reply #6 on: June 23, 2014, 05:05:11 PM »

Good advice from Stephen and Billi but both said something like:

As said , we need your consumption data  , to figure out your needs

OK so far but you also need to think about how you can adapt your consumption to match the available energy. E.g., use a slow cooker during the day when the PV is producing to avoid taking power out of the batteries in the evening. Pick what to cook for dinner depending on what energy is available. Let washing pile up until the batteries are reasonably well charged then run the washing machine. Etc. If you're at home a lot of the time your consumption will be a bit higher but you probably have more flexibility in use.

In other words, don't take your existing consumption as a given which has to be supplied by PV but also think about reducing and adapting to match the PV's production.

Where I am in the north of Scotland it's imperative to get absolutely the most out of panels possible in the winter so mine will be all south facing.  Further south this is less critical in many ways so it might well be worthwhile for you to have a split east/west system. That way you have gentler charging and  a longer window for direct consumption (without the energy going into and out of the batteries - that's the expensive bit) and more opportunity to get at least some energy on days which are dark in just the morning or just the afternoon.

That pvgis site is good but needs careful interpretation for off-grid use. It tends to optimize for maximum production across the whole year (which in, say, England means optimizing for summer because there's so little production in winter anyway) whereas if you want to be off-grid or nearly so then what you need to do is optimize for winter. If you can deal with that then summer will not be a problem (unless you have electric cooling, of course).
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« Reply #7 on: June 23, 2014, 07:37:25 PM »

If one intends  to keep the Grid powerline ( for the time beeing ) then surely a small  PV battery   inverter idea makes sense


 But again , i would go the full  road cause its only a fraktion more expensive  and there is a only a fraktion of time left until they do not like us selfproducers  anymore


3 or 5 kw Off grid inverter   that is able to communicate with  or without the grid ( Victron or , Studer or SMA)

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« Reply #8 on: June 23, 2014, 08:46:50 PM »

To further EA above it is necessary to optimise winter production in essence Dec and Jan because if you cope with these the rest is easy.  For these months the optimum angle is close to vertical and this can be further increased by putting the pv on a south facing wall and laying a reflective surface horizontally in front.  (no need to mess around on roofs)

Ken
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peterfc
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« Reply #9 on: June 23, 2014, 08:47:50 PM »

Hi All

Again thanks for your help.

I found my electric bill for December to March and i think the figure you want may be on there. It say i used from the 13th Dec to 17th March 1378 KWH. Would i be better counting each electrical item and there usage?

If it helps i live on my own and the figure was i think high due to the amount of aircon i used during that period to keep my house warm. I now have a log burner and i have also gone mad with insulation. Internal walls have had insulated plasterboard with a 35m airgap between the wall and the insulated board. I only have a few more walls to do now and the whole house is insulated and then the ceiling. Half my windows have been double glazed.

If it helps my house is South facing. 

Peter


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stephendv
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« Reply #10 on: June 23, 2014, 09:07:19 PM »

It say i used from the 13th Dec to 17th March 1378 KWH. Would i be better counting each electrical item and there usage?

So about 39kWh per day.  In off-grid standards that's HUGE.  Using http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php# and a random spot in portugal you would need a 20kW array to produce that in December, and it would produce 85kWh/day in September!  Count on about 0.7 Euro/Watt for PV, so 14 000 Euro just for the PV.  Ouch.

The advantage of maintaining your grid connection is that you don't have to supply 100% of your demand with PV.  There'll be an economic sweet spot where the PV will cover the majority of your consumption without being sized to match the rare peaks in winter.  Since heating would have been such a large part of that number, it'll probably better to work from the individual appliances.
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« Reply #11 on: June 23, 2014, 09:11:00 PM »

To further EA above it is necessary to optimise winter production in essence Dec and Jan because if you cope with these the rest is easy.  For these months the optimum angle is close to vertical and this can be further increased by putting the pv on a south facing wall and laying a reflective surface horizontally in front.  (no need to mess around on roofs)

Tilting the panels a little from vertical will not reduce direct sunlight much but will increase the amount of global radiation (sunlight scattered from blue sky and reflected from clouds). For an arbitrary point in mid Portugal with default settings for everything else PVGIS generation (kWh/day) in December for different inclination angles are:

35 2.53
50 2.76
60 2.82
70 2.82
80 2.75
90 2.62

Ie, it's not terribly sensitive but the best is probably somewhere around 60 to 70.

With a horizontal reflector in front I would imagine that the best angle would be a little steeper.
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« Reply #12 on: June 23, 2014, 09:19:34 PM »

So about 39kWh per day.  In off-grid standards that's HUGE.

By on-grid standards it's not small, either. However, counting on fingers - Jan, Feb, Mar - 3 months and a few days - call it 100 days - 13.78 kWh/day. Huh?
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« Reply #13 on: June 23, 2014, 09:25:44 PM »

Quote
Quote from: peterfc on Today at 08:47:50 PM
It say i used from the 13th Dec to 17th March 1378 KWH. Would i be better counting each electrical item and there usage?

So about 39kWh per day.  In off-grid standards that's HUGE.


Probably i am wrong , Stephan , but i only see  about 15 kwh a day in winter !

cause  .... 3 month    @ 30 days @  15 kWh  make 30 x3 (month) x15 = about 1350 kWh
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« Reply #14 on: June 23, 2014, 09:33:11 PM »

.... so multiplied those  3 month to the year  by 4  ( some people like calendars)   makes it  to about 5500 kWh a year

Now !!!!!!!! Most people will say ! reduce your  usage ,  id say u are fine and increase your PV  onpatrol


Surely 0.1405 cent per kWh  from your grid supplier  is not sooooooo much   , compared to other prices in Europe ( germany would be over 24  cents, easy)

But anyway  .... you have the sun   and choice  extrahappy


Please , have a think about your peak loads ( i mean oven cooker   etc) , but on the other hand , if u keep the grid , it will help out automatyically

Best regards 

« Last Edit: June 23, 2014, 09:47:17 PM by billi » Logged

1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
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