Solar powered life @ LifeInGalicia

Here in the small aldea of Mer near Sober we now own three houses, one we live in and two holiday homes. We have large gardens, various roofs and lots of sun. With our PV / storage system we power the three houses. We are about 90% self-sufficient. Partial PV “after” the Multi (Rule 1:1) help to prevent running to zero should the grid fail for a prolonged period. We do not participate in feed in tariffs.

Power flow @ LifeInGalicia

Technical details (basics)

The main house has a licensed 25A single phase connection to the grid. The PV consists of type “Balkonkraftwerk” e.g. one, two or four solar panels connected to a micro inverter in situ and from there it is basically AC cabling to three different feed in points. In total we have 15 panels of various performances and age (usually paired to the micro inverter) , installation angle (flat, south & east) and situation, like roofs etc.

In 2021/2022 the installation expanded to batteries and a main controller. We now have 4 x Pylon US3000C and a Victron Multiplus (48/3000 GX). This in itself is enough to run a “normal” house.

Installation schematic @ LifeInGalicia

We have three houses, so there is a management software element and some distributed WiFi switching.

 

Design details or why we have what we have

We do like our creature comforts. In the three houses we have underfloor warming in some bath rooms, towel heaters, three washing machines, a dryer, air-con, warm water boilers, etc..

Cooking and baking is done on gas. The main house has a 80L boiler for warm water (1 Kw !), an under table boiler at the sink, the guest houses have gas boilers. We are on natural water and leaving water for extended periods in a containers has its own issues and gas is simply more efficient.

For heating / cooling we use pellet ovens (central), wood stoves as well as split aircon. As the winters get warmer it is less of a problem. In winter we do not have guests and are usually traveling to south America. Houses can be remote controlled by VRM and OpenHab.

Because of the diverse catchment (PV) we produce on average about 18-22Kw/h a day (Spring to Autumn). The batteries store about 10Kw/h (SOC 30%) usable energy, enough for the night and a rainy day. The maximum measured PV peak performance is 4.5Kw divided onto three feed lines.

 

Solar production during the main season
Daily PV production

Power management

Based on OpenHab (Open software), TPlink as well as Sonoff  WiFi switches, a piece of custom developed software, running on a basic windows PC, this rules the distribution of power in the houses. 

The basic system looks after itself, the software provides advanced management options. Solar production, the state of the batteries and present demand determine the allowable demand preventing grid usage or feed in. 
In a nut shell, if there is excess it switches on things by priority, if there is less it switches them off, depending on the state of charge (SOC) of the batteries.

Power balancing @ LifeInGaliciaThe fight for power

The fight for power can become mesmerizingly intensive especially under cloudy skies.

We tell our guests that the house they rent is solar supportet and it would help if they do the washing if the sun shines as well as using power hungry implements only one at a time. In an exchange they do get tranquility and nature pure and help the environment and CO2 foot print… 

The overview
The overview

Some basic costs, calculations & savings

Assumptions: 20 year life time of the system. Panels @ 80%, batteries @ 80%, inverter life span @ 15 years,  Multiplus similar.

Based on time of writing, we have a fixed contract inclusive all taxes @ 0.15€ kWh and 55€ kW termination or potential per year (high & low).

The first saving is a reduction in contracted potential from 4.6 kW to 3 kW, as we no longer draw peak demands. According to the grid supplier we could go down to 2.5 kW.

1.6 x 55 x 20 = 1,760,–€  (Life span saving)

At today’s prices (8/2024) the equivalent of our installation:

5 x “Balkonkraftwerk” (2 panels 550 W/peak & one AP DS 960 micro inverter) @ 390 € each = 1,950.– €

Staging, install  & cabling est. = 1000 €

Replacements & repair est. 1,000,– €

Total cost 3,950.– € (Life span 20 years)

Production during the life span est. @ 130,000 kWh (based on our experience)

Photovoltaic Geographical Information System tool is ideal to check.

Cost per kWh – 3.950 € / 130,000 kWh = 0.03 € kWh (day time)

Storage:

1 x Multiplus (48/3000 GX) basic power and battery management = 900 €

Here we use Pylontech US3000C and we do not go below 30% charge (SOC) @ 900 € each.

Pylontech @ LifeInGaliciaThis results in a net availability of 10 kWh. These batteries are rated @ 6000 full cycles (100% – 10%) deteriorating to 80% capacity. 10 year extended warranty and great remote service.  After this time, these are still working, just having less capacity.
6000 cycles @ 10kWh = 60,000 kWh  3,600,– + 900 €  / 60,000 kWh = 0.075 € kWh (storage cost)

Our power mix on average is 12 kWh day time and 4 kWh night time (both need to be produced!)

16 kWh (production) x 0.03 € plus 4 kWh (storage)  x 0.075 € = 0.78€ daily (for 16 kWh)

It totally depends on your usage, contract etc., but based on our present tariff we save 2.25 € – 0.78 € = 1.47 € daily or 530 € a year. More impressive – life span – 20 x 530 plus 1,760.– = 12,360.– €

This is all very conservative as during the late spring till early autumn, when we have guests, helpers, watering by well pumps and regularly produce more than 22 kWh a day, which are fully used, the savings add up rapidly. Remember – Unit prices have been at 0.40 € kWh in February 2022

Yes, we are grid connected, we feed in about 0.5 kWh daily and we take on average 1.5 kWh resulting in a monthly invoice of around 30 €. This allows extreme balancing of the system, avoiding peak performances which will extend the life span and result in less replacements / repairs.

We could upgrade the Multi to a 5000 and add one more battery to go fully “Island”, but having the grid in a cost controlled manner is quite convenient and avoids the “single point of failure” issue.

Gas supply are external 15Kg bottles, twin or single. The supply comes round every 2 weeks or pick up at any petrol station. We only need about 5-6 bottles a year @18-20€ each. These also fit the standard movable gas heaters.

More details and experiences on the following page – LifeInGalicia solar story part II

Gardens @ LifeInGalicia