#11 Upgrades!
Over the course of writing this blog, I’ve made several upgrades and expansions to the systems in place. Some I mentioned briefly in previous posts, others I have not, or I might have only mentioned that things were in the planning phase. In this post I will show you what has changed in more detail, the reasons why, and the cost.
Before that, I think I never shared a good picture of the finished inside with floor in place, painted ceiling and walls, lights, and the masonry fireplace fully installed with chimney, so here goes:
This is before any furniture was placed. The combination of the spots and ‘spider lamp’ (Serge Mouille inspired) works really well I think. They’re all LED of course, and on dimmers, and have different color temperature options depending on the intended atmosphere. All sockets, light switches and dimmers are Schneider Exxact, in anthracite color. These things don’t seem to be available outside of the Nordics, hence the link to the Finnish site. Maybe I should write an entire blog entry on the interior, material choices, and appliances.
On to the upgrades.
Solar
I expanded the amount of solar panels. Initially I started with 10kW, and in the mean time I added another 6.5kW. These panels I sourced locally: we finally have decent solar panel options here in Finland at competitive prices. I bought an entire pallet of Astronergy 410W solar panels (36 in total) of which 20 were installed at family. The remaining 16 I added to my system. To do this, I added another charge controller (the same type as the others, a MUST PC1800F — but they’re calling it the MC1900E nowadays). The entire pallet of 36 panels, including shipping, came at a cost of 3000 Euro — that’s around 83 Euro per panel, or 0.2 Euro per Watt. The charge controller came in at around 150 Euro including shipping — taking advantage of seasonal sales on Aliexpress.
Where did I install these? In two locations: on top of the wood shed, and on top of a roof forming the extension to the technical building, under which I also park the tractor. Speaking of which, look at this beauty:
That’s a 1969 McCormick 434. It took me ages to find one that is in a good condition and at a reasonable price. I got this one for 2500 Euro, including delivery to my place. It needs a few minor things taken care of, but otherwise it’s perfect. The main use for this one is twofold: forest work, and snow clearing. It’s also a lot of fun to drive!
So really I did not just add extra solar because I needed it, but since I was building two roofed areas anyway, I just decided to put solar panels on them. The tractor expansion roofing material in fact are just the solar panels, nothing else.
Battery
The original battery was 28kWh. This was later doubled to make a 56kWh pack. I’ve now bought the cells to make this a 100kWh pack. Battery cell prices have been dropping quite a bit over the last year, and we can now easily get them at competitive prices without long waiting times due to shipping from China. My preferred vendor in Europe today is NKON. I went with Envision 305Ah cells, at 71.9 Euro per cell. Shipping to Finland comes at around 380 Euro for 48 cells, making the cell price 80 Euro per cell (including bus bars), or about the same price per kWh.
For the BMS, I’m sticking with the JK BMS. There is a new ‘inverter style’ version which provides communication with other equipment such as charge controllers and inverters, but I still prefer the ‘old’ style. You should visit Andy’s Off Grid Garage YouTube channel for in-depth looks at the inverter style BMS. I also stick with the 100A version with 0.6A balance current — this has never caused any issues. Price per BMS was 72 Euro including shipping, again, with some right timing to get a discounted deal on Aliexpress.
While at the time of writing I’ve not yet installed these new cells, they should be up and running somewhere around autumn, bringing my total storage capacity to 100kWh. Part of the delay is that I’m reorganizing the batteries a bit to make it more ‘clean’, that is, I’ve noticed over the past few years I don’t need the insulated/heated set-up anymore. The 3000L heat storage tank is in the same building, keeping the whole building acceptably warm even in dead of winter — even with the record breaking cold we had this winter. I’m now placing the batteries on a shelf instead. This is more space efficient, and I like that I can now see the battery cells as well. It’s an off-the-shelf (pun intended) shelf, from the local hardware store (about 80 Euro or so each) with some added reinforcements.
Together with the increased amount of generation, I believe this will be the final upgrade at the power side of things for some time to come (I know, famous last words). There are times where I’m thinking it would make sense to build a 1MWh battery in a shipping container. Even at 10kWh of use a day (about twice what I typically need), this would last 100 days: enough to get through the darkest winter months… If cell prices go towards $50 per kWh, I’ll seriously consider it.
Heat Pump
I mentioned in the heating systems blog entry that I was in the process of getting a heat pump. It’s now up and running and has been providing heating in autumn and spring. This provides a very efficient way of using excess solar. While during spring and autumn I generate a lot of power (especially with the upgrades), I can multiply this energy in the form of heat by a factor of 3 to 4 with the heat pump (I’ve seen CoP over 4 as well). Remember that a heat pump does not create heat, but moves it — which is much more efficient. This is why you see heat pumps with 400% or more efficiency and this does not violate any laws of physics: per kWh you put in, you get 4kWh of heat. This way, I need to burn less (or no) wood during these periods, and increase overall comfort. It’s usually still freezing well into April, and being able to heat the home during those days without having to fire up the wood gasifier makes it feel like spring is actually really finally there (or that winter isn’t there just yet in the autumn).
In summer, I use the heat pump to cool the house, using underfloor radiant cooling. While this is definitely not something that works in every climate, for those few weeks per year we get hot weather (read: anything above 25°C, with a couple of days up to 30°C even!) it’s perfect. The heat pump cools the water in the storage tank, which in turn gets pumped in the floor, cooling it down. It acts as a heat sink for infrared radiation and, with an added fan for air circulation, it cools the house down. You have to be careful to not make the water too cold since then you have the possibility of condensation (you have to monitor dew point), but in this climate it’s not an issue. Even at a relative humidity of 50% and air temperature of 30°C, one can safely circulate water at down to 18°C. Together with the mechanical ventilation, there are no issues — but just in case (and I want to experiment with colder water temperatures), I’ll soon add a dehumidifier as well — plenty of power to run that anyway! You can find a dew point calculator here.
The actual heat pump model is a Power World PW030-DKZLRS Monoblock 8kW heat pump. The 8kW is the heating output, not the power input. It typically draws under 2kW from the inverter and I can run this easily off my ‘winter inverter’, the 3kVA Victron Multiplus II. It uses R32 as the refrigerant. I know there are R290 heat pumps (Power World has the same model with R290) which can deliver water at higher temperature and are more efficient when it’s very cold. Thing is, I don’t need hotter water (in summer I use a regular immersion heater tank for hot water since the large tank is cooled) and in the dead of winter I don’t have enough electricity to power the heat pump. The R32 version was/is cheaper as well, and I was able to get one for under 2000 Euro including shipping.
Installing this type of heat pump is easy: I just have to connect the inlet and outlet of the heat pump to a lower and upper connection respectively on my storage tank. No messing about with refrigerants, or dealing with an indoor and outdoor unit, drawing vacuum… I just used PEX piping to go from the tank to the outside through the wall, and hooked up the heat pump with some flexible armored hoses.
Conclusion
While some of the upgrades such as solar and battery were technically not needed, it made sense to do them anyway. The cost of solar panels is so low that they can be used as a building material: the roofing material on the extension was cost effective and functional using solar panels instead of more traditional roofing materials such as metal or asphalt shingles. The added battery storage coupled to the extended amount of solar allows me to bridge more days of bad weather and get me further into autumn and earlier through spring without having to run a generator.
The added generation and storage capacity also allows for a more efficient and effective use of the heat pump. I made a control and monitoring system based using Grafana and a bunch of Python. Based on things like state of charge, weather forecast etc. it decides if it can use battery, or of course when the battery is full everything can be diverted. With weather forecasting, it can decide if the battery can be discharged further down or not based on forecast generation, which in turn means the heat pump can run more consistently.
