For heating, you could bring in a small refrigerator rather than a resistive load. Get something besides heat for your power.
But then you would need to run the refrigerator even when it's hot...
Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
151–160 of 192 posts
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#152Earlier quoted context omitted.
Being able to sell the system is irrelevant as long as the system will last indefinitely (or say, 30 years, which approximates the same value anyway). Everything but the battery is solid state and should last indefinitely -- or certainly more than 8 years. I already excluded the battery as a consumable to calculate the 13% rate of return. But one thing you are right about is the other parts will fail eventually, drag…
> Solid state parts can last decades though. But every year we seem to get better silicon. Better CPUs, GPUS, SSDs, etc. Same holds for photovoltaics. To run with the investing analogy, it's like claiming you bought a bond with a 5 percent return, when six months later interest rates shift in the bond market. Now the rest of society is getting 7 percent returns, and you have to sell your to sell your bond at a discou…
To run further with that same analogy, what if you expected bond rates to keep increasing for 50 years? It would not seem wise to keep your savings in a checkings account for these same 50 years, to then get the highest rate.
Yet that's what most of us keep doing with solar, missing out on a good deal because it gets better every year.
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#153The author's calculations for the capacity of the battery are very wrong and the battery will not last many years the way he's using it.
Deep cycle lead-acid batteries should not be discharged below 50% (known as Depth of Discharge, or DoD) unless you really want to kill them quickly. The author's calculations assume he can drain the battery 100% (35Ah), which while technically correct, will kill his battery very quickly.
Unfortunately the manufacturer doesn't provide any data on the capacity over discharge cycles at different DoD's [0], but I can guarantee the author will significantly shorten the battery's lifespan by discharging it so deeply.
If you want some idea of the effect of DoD on battery health, Hoppecke have a very good chart in their datasheet on page 43. [1] At 50% DoD, the battery will last for approximately 3000 cycles, or 8 years. At 90% DoD, the battery will only last for 1500 cycles or 4 years.
If you want to go for 100% DoD in solar, you're looking at Redox flow or Lithium battery technologies, both of which are more expensive than Lead-Acid.
There are other problems with this setup as well. At $17, the charge controller is very unlikely to support an equalization charge mode, which is required to periodically balance the cells within the battery to ensure a long lifespan. The author would be better off skipping AC entirely and charging their MacBook/iPad from a car charger which operates on 12V. DC lights can also be purchased quite inexpensively. The AC inverter is likely putting out something closer to a square wave than a sine wave, and the low voltage cut-off is far too low to avoid damaging the battery.
This is really a case of "you get what you pay for" and for such cheap components, the system will not perform well or last for very long.
If this sounds really negative, I'm sorry. I want more people to become energy independent, but if you follow the author's example, you're going to have a very bad time. If you are seriously interested in going off grid, you should invest in quality components like Victron, Outback, Studer, Hoppecke, etc. Something like the Victron EcoMulti would be a good choice for someone who wants an easy to use system that's been designed for longevity. [2]
[0] http://www.expertpower.us/exp12350
[1] https://www.hoppecke.com/fileadmin/Redakteur/Hoppecke-Main/P...
[2] https://www.victronenergy.com/solar-pv-inverters/ecomulti
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#154I'm hoping to build a similar system in the next year or two. Biggest difference is I plan on building battery banks out of lithium-based 18650 cells. You can salvage them from old laptop batteries, even dead ones (one bad cell can bring the whole battery down, even if the other cells are fine). 18650s are also used in Tesla's car batteries [0] and Powerwall. They literally just cram thousands of them in there. There are some youtubers who have done tons of stuff with them [1][2].
[0] https://youtu.be/NpSrHZnCi-A
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#155Cool! The one thing I notice the author gets wrong is (out of modesty perhaps) claiming the system isn't very financially successful. But it actually is! > 200W system payback period: $300 / $48 = 6.5 years until payback > Either way you cut it, this is not a money saving machine. Energy prices are just too low. That represents like a 16% rate of return with little risk, which any investor would take in a second. How…
Thanks to put that in number. I was unsatisfied with the "not good enough" conclusion after reading it, but couldn't exactly say why.
CO2 footprint probably also is better than mentioned. Certainly, it would take 4+ year to pay back for it, but what would have been the footprint for those 4+ years using coal based electricity? It's not only "how does the system perform", it's also "how does it compare".
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#156Cool! The one thing I notice the author gets wrong is (out of modesty perhaps) claiming the system isn't very financially successful. But it actually is! > 200W system payback period: $300 / $48 = 6.5 years until payback > Either way you cut it, this is not a money saving machine. Energy prices are just too low. That represents like a 16% rate of return with little risk, which any investor would take in a second. How…
Well but 6.5 years sound s like a lot of the parts are getting replaced 1.x times which increases costs again.
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#157You could save some energy by driving Led lights directly from the 12V battery. Not through an inverter.
Doeasn't matter in this case though since one of the things he's running is electric heater. When you are usin lights you are just getting bit more heating comming from inverter.
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#158Earlier quoted context omitted.
It's called a battery isolator, and it's basically a monster diode from the alternator to the battery. Very common setup for RV's, etc. I had one set up in my Jeep so that it would charge the deep cycle marine battery for my fishing pontoon's electric motor... way, way faster than anything you plug into the wall.
I think you might mean solenoid?? It's controlled by the ignition. When the key is on / car running both batteries are in parallel. When the ignition is cut, the solenoid isolates a few circuits that are wired on the backup battery side of the solenoid. This is what I have in my vanagon. I run the radio, fridge, interior lights and some 12v / USB outlets. http://www.gowesty.com/product-details.php?id=2418
I doubt it's a solenoid. Solenoid can be used for galvanic separation in AC circuits not DC. Maybe you mean relay?
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#159I've been chatting a bit about thermal building design. This article reminds me that for most entertainment or work, we don't need much energy.
Cost comes from AC, heater, fridges. Other household appliances too but these are transient.
But with carefully dimensionned walls, you can slow the heat spread enough to avoid AC most of the time.
Surely we could keep our energy needs low if we wanted to.
Re: Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing
#160I work in solar, and your panel really, really, REALLY needs to be secured from wind. Luckily, they make ballast mounts that don't require screwing into the roof[1][2]. [1]: http://www.orionsolarracking.com/commercial-roof-mount/balla... [2]: https://www.civicsolar.com/products/racking-mounting/applica...
Got it! Thanks for the input. Damn that drives up cost, though. I'll work on securing it with weights and post an update.
If that thing catch up wind and fall you'll surely have to pay a lot more. It's surprisingly quick how wind can shift large surface like this.