Newbie from Portugal building a house :)

[gonmag8]

Hi all.
I am new to solar but I have been playing with batteries in my profession for a few years, I am an automotive engineer by trade and have been involved in some mild-hybrid vehicles. I am familiar with electricity (mainly DC)

At the moment I am building a new house in Portugal and I am starting to think about what sort of solar system will I put in place.

The new house has 100m2 flat roof without shades that I plan to use for solar panels. The roof floor has white stone gravel so I was thinking would it be a good reflecting surface for bifacial panels ?

I have been watching some youtube videos and reading these forums for a while but even so I probably need to continue learning before deciding on anything.

Portugal has a few constrains that I must keep in mind.

• Exporting to the grid is not paid, so there is no point doing so
• No real benefit in having dual tariff as most companies charge a huge premium for daily rate and the night rate is just a little bit cheaper than fixed tariff
• We pay a fixed monthly fee based on the max power input of our mais board, (so think a peak shaving functionality would be beneficial here ?)
  • If we drain more that that "hired" max power the board switches off and the house looses all electricity, this leads most people to overestimate the max power input to prevent power cuts in case by coincidence someone turns on all appliances at once.
• Customs are very problematic here, things often just disappear and in some cases duty paid parcels end up having to pay duty again

The house does not have access to gas or any other form of energy other than electricity, it will have the following main loads:

• 11KW heat pump (draws about 5KW electrical) but mainly used in winter when its colder and there is less sun
• Fridge / Freezer
• Induction Hob
• 2 x 1.5KW Sewers pumps
• 7m wide garage gate will have an interesting start-up current on the electric motor to open it
• Electric Oven
• Might get electric car in the future ?

With regards to space to accommodate the equipment, that shouldn't be a problem as the garage is plenty big

The idea is to be grid tied but produce as much as I can, What would you recommend in terms of inverter?
The microinverters seems to be out of the question due to wanting a 48V DC battery. Is a "all in one" inverter the best option ? but that will create a single point of failure in the system …

No budget as of yet as house is not finished. Not sure how much money will I have left

anyway, thanks for reading, happy to learn from you guys ?

 

[Don B. Cilly]

Out of curiosity... why spend a lot of money on solar if you have grid access?
You don't really get black-outs in Portugal, do you?
Is it because

If we drain more that that "hired" max power the board switches off and the house looses all electricity ?

If the house loses all electricity, can you turn it back on, or does the electric company have to do it?
In the latter case, why not just have a breaker that trips before you reach that limit?
-

 

[gonmag8]

Out of curiosity... why spend a lot of money on solar if you have grid access?
You don't really get black-outs in Portugal, do you?
Is it because


If the house loses all electricity, can you turn it back on, or does the electric company have to do it?
In the latter case, why not just have a breaker that trips before you reach that limit?
-

thanks for your reply.
No, you are right, blackouts aren't common.
When the house loses all electricity we can turn it on by ourselves.

The idea is to do solar as an investment to reduce electrical bills

 

[Don B. Cilly]

The type of load you have doesn't really go well with solar, IMHO.
I don't know, do the math, can you really save enough to justify the investment/hassle?
-

 

[mrzed001]

Off-grid (with grid support) is the way
If sun is up then solar reduces actual utility consumption.
If you put a small lead-acid battery under the inverter then it is an UPS too.
If you put a bigger LiFePO4 battery under the inverter then you can charge it at day and discharge it at night.
Also you can charge your EV from it (if you are not home at day, to charge it directly from PV)

11kW heat pump? 3 phase 400V ?
3pcs of 5-8 kW off-grid inverter can make 3 phase (3x5kW or 3x8kW).
Also there are 3 phase real hybrid inverters (12kW, can be paraleled).

 

[Don B. Cilly]

• 11KW heat pump (draws about 5KW electrical) but mainly used in winter when its colder and there is less sun
• Fridge / Freezer
• Induction Hob
• 2 x 1.5KW Sewers pumps
• 7m wide garage gate will have an interesting start-up current on the electric motor to open it
• Electric Oven
• Might get electric car in the future ?

So what would you be installing? 30 kW of panels, 15 kWh of LFP batteries, a couple of all-in-one-inverter/chargers in the 10kW range each?
Plus cables, etc... say, roughly 35-40K € of equipment? Which would not cover all those loads, mind you...

How many years would it take you to spend that on electric bills? Even if you reduced them by 50%, would it be worth it?

Now, using gas for cooking - which is better anyway - and heating, getting more efficient appliances, and such, that would be the approach I would take.
Gas, if you can't get a butane/propane tank installed near the house... I remember a big house in Formentera years ago, they had some 10 or 12 big (the 1.5 metre tall cylinders) gas bottles in a shed, all connected together, it basically did the same job. Repsol delivered them by lorry, just like the small ones.
-

 

[gonmag8]

Thank you both for your views, it is making me consider.

Unfortunately Gas is out of the question as the build is already advanced enough to not allow any other form of Energy.

The heat pump (and the entire house) is single phase 220V (The 11KW is heating capacity, not electrical consumption, that should be about 5KW)

Does this change the analysis ?

 

[Don B. Cilly]

Unfortunately Gas is out of the question as the build is already advanced enough to not allow any other form of Energy.

That makes no sense. Gas is very simple to install. I've seen it installed in less than a day (methane, from pipes) in a 17th century house, imagine how far the build was on that ;·)
-

 

[gonmag8]

Everything can be done, agreed
Would involve council permits and other things I am not willing to go through at the moment. The heat pump is also already installed and don't forget that gas prices are about twice as high here compared to spain.
The fact that there isn't plumbed gas and it is expensive is leading most new builds to have heat pumps.

 

[Don B. Cilly]

Would you require council permits to connect a 12 kg. gas bottle to a gas cooker/oven and an on-demand water heater? Probably not.
Well just that (the amount of gas used is negligible) would cut your power usage by... quite a bit. And it will let you use gas for cooking, which is vastly superior to electricity. Gas water heaters are also quite efficient.

If you could go wood-stove for heating (see my signature for some hints ;·) and address other appliance consumptions, it would not only cut your electricity bill to start with, but it would allow for (a lot) more sensible investment in solar.
-

 

[gonmag8]

Agreed, but I aint gonna move wood or gas bottles every couple of weeks

 

[mrzed001]

So what would you be installing? 30 kW of panels, 15 kWh of LFP batteries, a couple of all-in-one-inverter/chargers in the 10kW range each?
Plus cables, etc... say, roughly 35-40K € of equipment? Which would not cover all those loads, mind you...

How many years would it take you to spend that on electric bills? Even if you reduced them by 50%, would it be worth it?

Now, using gas for cooking - which is better anyway - and heating, getting more efficient appliances, and such, that would be the approach I would take.
Gas, if you can't get a butane/propane tank installed near the house... I remember a big house in Formentera years ago, they had some 10 or 12 big (the 1.5 metre tall cylinders) gas bottles in a shed, all connected together, it basically did the same job. Repsol delivered them by lorry, just like the small ones.
-

Did you never hear of off-grid with grid support systems ?
Many (most in EU) only know grid-tie and separated off-grid systems. And know nothing about other alternatives.
Really EU is 10-15 years behind US in this. Knowledge and some regulations missing too.

An off-grid with grid support and GTIL systems lets the grid through (to the house)
If sun is up then it lowers the grid consumption by the amount the PV system is generating.
You do not need to be able to generate all the power your home needs (separate off-grid) if full UPS mode is not required.

Also 40K € ???? Whaaaat ?
14,4 kWh LiFePO4 is $2700 + BMS $200
An 5kW MPP Solar off-grid (with grid support) inverter costs about $800
An 12kW 3 phase real hybrid Deye inverter costs about $3300
You have a x6 somewhere in your calculation

 

[Don B. Cilly]

You wouldn't have to if you stock up
Still, I agree, a wood stove is not for everybody. It's messy, you have to tend it... I really like it, but I understand the drawbacks.

Still, you can do the math, right? This thread is quite helpful on the subject of batteries (the costliest part).
-

 

[mrzed001]

You wouldn't have to if you stock up
Still, I agree, a wood stove is not for everybody. It's messy, you have to tend it... I really like it, but I understand the drawbacks.

Still, you can do the math, right? This thread is quite helpful on the subject of batteries (the costliest part).
-

14 kWp solar panels costs about $7000
12 kW Deye inverter costs about $3300
14,4 kWh LiFePO4 costs about $3100
Even if you buy double of it, so 28,8 kWh LFP then it is only $6200
So why it is the "costliest part" ?

For the cells, I'm using Docan as a reference: 304Ah EVE cells. These go for $158 per cell. As mentioned we need 16, so this brings the cost to $2528.

 

[Don B. Cilly]

Yes, sorry, I got it wrong about the panels.
In Portugal, you could use <10kW for 15kWh of LFP - and that sort of load. So some €5k.
But on batteries, those numbers only work if you want to build them yourself from Chinese cells.
So for 15k, you're more likely looking at 4-5000 - even buying the cheapest rack batteries.

See, me, off-grid, I have 5.6 kWh of LFP, 1kW of panels - of which I get 7-800W at best (but I don't have any big loads) and I'm happy - we haven't really seen much sun at all for a week, and I only had to turn the generator on for some four hours altogether.

So yes, with big loads, the math is a little different. It has to be worked out, I haven't done it, I was just trying to get a quick ballpark figure.
-

 

[mrzed001]

Yes, sorry, I got it wrong about the panels.

Many do.

In Portugal, you could use <10kW for 15kWh of LFP - and that sort of load. So some €5k.
But on batteries, those numbers only work if you want to build them yourself from Chinese cells.
So for 15k, you're more likely looking at 4-5000 - even buying the cheapest rack batteries.

This forum is all about DiY
From the simple ready Rack/wall mount to the not much heavier build from cells (or IKEA style all included DiY packs like the Seplos Mason)

See, me, off-grid, I have 5.6 kWh of LFP, 1kW of panels - of which I get 7-800W at best (but I don't have any big loads) and I'm happy - we haven't really seen much sun at all for a week, and I only had to turn the generator on for some four hours altogether.

That is why the grid support is good. No need to go separated off-grid if the grid is available.

So yes, with big loads, the math is a little different. It has to be worked out, I haven't done it, I was just trying to get a quick ballpark figure.
-

Here we did some bigger installations. Like smaller factory had lost a lot of money because small blackouts.
Even by making its plant UPS made a lot of money for them.
The PV generated free energy was only the extra win on top

 

[houseofancients]

Out of curiosity... why spend a lot of money on solar if you have grid access?
You don't really get black-outs in Portugal, do you?
-

those are pretty simple questions to answer.
Electricity ( with exception of CA ) is very expensive here, and taxation in most European countries is about to sky rocket.
Add to that , that electricity prices are coupled to natural gas prices, and you get the point.

some people here had a 400% increase of the energy costs over the last few months.
Mostly due to gas, bit as electricity prices are coupled, it's been crazy

as the grid in most parts of europe is very very stable, it's a good idea to have it as a backup, but it makes sense to self generate as much a possible

 

[Don B. Cilly]

Ibiza happens to be in Europe :·)
The grid is not available here (I'm quite far away from any wires), if it were, I don't think I would bother with solar. I use very little anyway.
-

 

[houseofancients]

Ibiza happens to be in Europe :·)
The grid is not available here (I'm quite far away from any wires), if it were, I don't think I would bother with solar. I use very little anyway.
-

ibiza ... that isnt Europe.. that's party away ;-)

 

[Don B. Cilly]

Oh, Ibiza is so much more than parties...
Still, up to about a year ago I lived in a house in a village. No solar, just grid. My monthly bills were always <€30.
Now, I still get electric bills - for a warehouse I share in town. My last bill for that was €21. The one before, €19.
It really depend how you use it... right now, off-grid, 1kW (theoretical) of panels, 4PM, half-cloudy day, batteries charged fully, I'm running the washing machine. "Cold" cycle - which isn't really cold, the water goes through some 20 mt. of black pipe, even on a cloudy day the water gets to the house quite warm.
-