My solar-powered blog is now on lithium iron phosphate
louwrentius.com
louwrentius.com
I switched the marine batteries out after about four years of operation.
I took down the solar panels in 2013 because the roof needed repair.
If I were doing it today, I would probably give Lithium-Iron a try. They weigh less, have higher power density, and last longer.
Or were the renewables strictly to run the server?
I now have another house elsewhere with 4kW of solar on the roof. I would add more, but for two reasons:
1) There might be enough space up on the roof for another 2-3kW, but it's close.
2) The local laws governing grid-tie are such that I can't just add more panels. I can put up another separate system, but with a separate meter. I'm concerned that two separate systems on the same grid point trying to sync to the grid may have problems where they interfere with each other. I have read about such problems.
Fortunately the solution would appear to be use of a GPS central time clock that is fed to the 2x PV arrays individualy... if you run your own local time server you can 'skew' the clock signals to each array to get them in sync with each other and then in to a dummy load of spare lead-acids or a capacitor bank (if you want to get fancy and don't mind the 'large gray box' emitting smoke and launching itself off the wall from time to time).
Then you sync your 'mini-grid' to their slightly larger mini-grid.
Oh and when synching - never forget the old-school 4-light-bulb trick as a visual confirmation that things are synched correctly before tying in to the grid. Oh and fuses, large ones. With spares.
If you can find a friendly H.V. engineer or Linesman they might be able to tell you what clock source 'their grid' uses (GPS, Network time etc etc) which makes synching to the local-ish grid a whole lot easier if you have the exact same setup. I think the main thing is to make sure you have the dummy-load ready to feed/smooth what can be at times be a large inrush/outrush till the load equalizes.
Obviously, always seek out advice from someone that knows what they are talking about and has knolwedge of local laws, quirks of the grid etc.
I'm somewhat skeptical that GPS synchronization is the real answer here. The problem is synchronizing the phase of the PV system to the grid so they can work together to power the load, allowing excess PV power to be sold back into the grid when not needed locally. To synchronize, one needs to control the phase of the PV system so it always slightly leads the phase of the grid. Determining the phase of the grid is the challenge. With two or more locally grid-tied PV systems, you cannot know the phase of the grid with much certainty because each PV's take on the grid phase is the aggregate of the actual grid phase and the phase of the other PV systems. Positive feedback and phase oscillation are likely.
Using GPS to synchronize with the grid assumes that the grid's phase is stable, but my observations over the past few years have revealed that today's grid has much less short-term stability than the grid of old. I'm assuming that the lower phase stability today is caused by the recent massive adoption of grid-tied PV arrays. So instead of using GPS time to guess the current grid phase, you really need to know what it is (locally). Aside from placing grid phase monitors on nearby houses, I don't know how to do this.
Also, they say that usually LFPs will last a bit longer if they're installed such that they're under a bit of sideways compression. I don't know why that is.
it makes sense that cylinders would be immune to swelling
Not sure why, but when I saw your name in this thread - it was entirely expected ¯\_(ツ)_/¯
Snark aside, I feel that on HN, there are enough actual proper experts who will point out avenues of research and gotchas that a single person chasing down rabbitholes on their own is unlikely to discover.
one of jacquesm's previous personal rabbitholes was designing and building a wind turbine from scratch, down to cutting out the stator and rotor windings for the generator from sheet metal
Email in profile.
And if you google my name + long range e-bike you get an article about a pack that I laid out (170 cells, 2.2 KWh).
I think this video by off-grid-solar explains it quite well. https://www.youtube.com/watch?v=63-Nx75_xXM
In the Netherlands it's near impossible unfortunately to achieve 100% off-grid due to the winter months, when you basically have no solar. Maybe there are Dutchies who have somehow achieved it (with overprovisioned solar).
Do you still have a grid connection for backup or are you 100% disconnected from the grid?
What is the typical kWh/day consumption of a household there in winter months?
To be frank, I've looked in my Energy supplier app (Vattenfall) and it states for December an average usage of 122 KWh (all households) and energy efficient households (solar) of 91 KWh.
122 kWh per day ? That can't be right.. does that include gas or something?
https://re.jrc.ec.europa.eu/pvg_tools/en/
What you're looking for is the "Off Grid" tab, plug in your details. e.g. solar array size, size of battery, etc. Then click visualize results. After visualizing, there are a few tabs to help you make some decisions.
For your case (Netherlands, it looks like a 5.4kWp solar array and 4kWh (I assumed 5) used per day, and with a single 5kWh battery, you should be able to go off-grid :) In fact, during summery months, you could even push to the grid.
This tool even looks at cloud data based on various databases. I don't know of it's accuracy, but I'm inclined to trust it.
To be frank, my consumption was already quite lower, but I've made quite a lot of changes to reduce energy consumption even more.
I ran a custom x96 router/fw that I replaced with a $60 Mikrotik router that also replaces a separate switch. I've replaced more power-hungry computers with energy-efficient ones.
My existing server setup ~500Watt continously would likely take up 10KWh a day, but this is my magic trick: I don't need them 24/7. So they are off, and only turned on when required (remotely with WoL / remote power switch). The rest of what I need is on several Raspberry Pi 4B+ devices (I was lucky to buy a ton when we still could).
A lot of people here in South Africa are keen on off grid but it's unreasonably expensive since you'll have to cater for those rainy days, and that means you'll need to build a very large system.
BTW kWh/day consumption here in the winter (which is probably typical) is around 25kWh per day.
I wonder if it would make sense to get a generator[1] to supplement solar on rare occasion.
If you want to build solar, but the cost of achieving reliability is the one thing stopping you, then maybe a generator could remove that obstacle.
Yes, it emits carbon, and the fuel costs money. But if you only use it a few days each year, that might not be very significant.
However, it makes the system design more complicated, and generators require maintenance.
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[1] I'd use propane since it can be stored 10+ years, whereas gasoline and diesel last 6-12 months. Also propane can be used for emergency heat.
Have you had to scale back usage of certain appliances such as irons, air conditioners, washing machines etc?
Thanks to the oversized PV array, we generate power even in cloudy conditions. The PV array is also split in half and oriented east+west so it catches more sun through the entire day instead of a midday peak.
For things like clothes washing, drying, and hot water heating, those are the heavy users but can be moved to times of good sunlight.
We only run out of power if we have 2 or more days of heavy rain in a row, which only happens a few times a year.
We really only use it for short showers, and it stays warm enough for that, for about 3 days without power.
At 10% years they will have 80% of capacity.
A-grade cells are often rated for 6000 cycles.
It’s amazing. I've updated the article with those numbers.
These things are fun, but they pack a whole lot of energy!
Even Bosch got this wrong on their pannier mounted battery packs, I've opened up a whole pile of failed Bosch packs to see how they fail as a guide to my own pack design and the most common failure was water ingestion due to bad seals followed by burned out balancing wires that some how got worn out or pinched. This stuff is very critical and I would (1) never buy a pack that some other hobbyist made and (2) never sell the pack that I made to someone else.
If something goes wrong with these kind of batteries, it's never the batteries themselves (specifically LiFePO4) but it's always a bad connection or an undersized wire causing high resistance and thus heat --> fire.
In my case, my wires are quite oversized and I bought a proper lug nut crimping tool (and not use a vice or soldering (Don't do it)) to make the connections. I've also really made all connections tight, double-checking them.
But doesn’t that mean you had some partial downtimes? How did you manage to keep everything running during these 30 minutes where data was copied from the old DB to the new one? Let’s say there is a cron job that must be executed and its result would be stored back to the DB. Did you “pause” everything and reschedule it in the new instance once the diff copy was over?
1. Have you considered adding a small wind turbine (DIY of course) to supplement?
2. Although the costs are certainly coming down and within the realm of possibility for many, they are still too prohibitive for those that would benefit the most. Do you see any way that you could recreate your project on a shoe-string budget?
Yes, I've looked into running a small wind turbine but from what I can tell it's not worth the money or effort.
There is a reason why they build wind turbines so large and high. At small sizes, with our wind speeds, they barely produce any energy.
I can't also just put one on my balcony as I'm not allowed to (building regulations).
If I ever want to build my dream renewable energy build, I really have to relocate :)
Regarding a shoe-string budget: it all depends on your goals. A key thing is doing everything second-hand, maybe except for the LiFePO4 batteries, unless you can find those. In the Netherlands, There's a lot of solar gear moving through our local Ebay (Marktplaats, owned by Ebay) so that's something to look out for.
Though, I suppose this is more of a challenge thing
Panels and batteries are relatively cheap (and getting cheaper) to the point that it can makes sense to have purpose-built setups.
Another interesting case would be to use an API to get your areas power generation stats and when the wholesale pricing is low due to solar/wind generation peaks, charge your battery off the grid.