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Show HN: $200 Solar Self-Sufficiency Without Your Landlord Noticing

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Re: Show HN: $200 Solar Self-Sufficiency  Without Your Landlord Noticing

#141

Post by megablast »

pilom wrote: post #24

> Unless you live on an RV or a boat it doesn’t make financial sense yet If you're curious about what a system for an RV does look like, I work remotely full time in an RV and built my own system: https://therecklesschoice.com/2016/04/29/diy-rv-solar/ 6.5 times the solar, 15 times the storage, 20 times the inverter (but mine is overkill for us honestly).

And cost?

> We installed a fairly large (for an RV) completely custom solar power system all by ourselves for right around $3000.

Sorry, saw that. 15x the cost.

Re: Show HN: $200 Solar Self-Sufficiency  Without Your Landlord Noticing

#143

Post by c8g »

nikodunk wrote: post #5
WheelsAtLarge wrote: post #4

Nice hack. Can it power a fan for a night? That might save you some money in cooling, which would help with payback. I won't be using it for my apartment but it has great potential for an off the grid light power use workshop. Good job, thanks for showing. Just a note, the biggest expense these days in solar power installations, home, is the manpower and incidentals needed to install it. Reduce that and solar power r…

Hey! It can power a fan overnight no problem. A large box fan uses around 45W, so this could run it for 10hours on a day's charge. Good point! To your point of expense – the installation cost is what bummed me out, too. That's exactly why the hack is so effective if someone in your family can self-install it! I agree. Similar to an AC unit or a satellite dish that most people just install themselves...

we have a table fan specially made for solar is 11.5W, costs about $14.7

Re: Show HN: $200 Solar Self-Sufficiency  Without Your Landlord Noticing

#146

Post by adrianN »

SwellJoe wrote: post #111

I've been using rooftop solar for many years; I live in an RV (for a total of about 7 years, spread across two different RVs, both with solar on the roof). I currently have a 400W system. It makes extremely good economic sense in my case, because it enables me to live comfortably off-grid for weeks or months at a time; which can save hundreds of dollars a month in RV park fees, when I'm traveling. But, the talk of po…

For water heating, you could skip the electricity step. I suppose that would gain you a factor two or three at least in the available wattage.

Re: Show HN: $200 Solar Self-Sufficiency  Without Your Landlord Noticing

#147

Post by Retric »

trhway wrote: post #138
Retric wrote: post #125

Earlier quoted context omitted.

That's not how wings work. https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html Most obvious problem aircraft can fly upside down.

you're trying to argue with the Bernoulli law. I wouldn't recommend it :) Even your link clearly states: "{The upper flow is faster and from Bernoulli's equation the pressure is lower. The difference in pressure across the airfoil produces the lift.} As we have seen in Experiment #1, this part of the theory is correct." Re-read my original comment - it is pretty much stating the same as the cited text above. The link…

Read the full page.

"The symmetric airfoil in our experiment generates plenty of lift and its upper surface is the same length as the lower surface. Think of a paper airplane. Its airfoil is a flat plate --> top and bottom exactly the same length and shape and yet they fly just fine."

Wings are angled into the wind. The curved shape primarily minimizes drag rather than generating lift.

As to hurricanes most roofs are sloped. Yes, faster moving air has lower pressure, but if you run the equation it's a fairly weak effect. So, it has little to do with stall speed.

Re: Show HN: $200 Solar Self-Sufficiency  Without Your Landlord Noticing

#148

Post by jldugger »

galdosdi wrote: post #42
pilom wrote: post #28

Earlier quoted context omitted.

Unfortunately it isn't a 16% return because he can't sell that system for what he paid. If you buy a stock at $300 and sell it for $348, that's a 16% return. But for him, he probably would have trouble selling all of that for $100 (the battery will be worthless in about 2 years given how far it is being discharged and very few people buy these things on craigslist for anywhere near what they cost). If he can sell it…

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 discount to compensate. Sure you can hold the bond to maturity, but you're still missing out on that 2 percent return in the greater market.

Re: Show HN: $200 Solar Self-Sufficiency  Without Your Landlord Noticing

#149

Post by Retric »

quickben wrote: post #135
Retric wrote: post #126

Earlier quoted context omitted.

Run some actual math > fear. Yes, in a slightly different situation this would be an issue. But, wind is not magic fairy dust that can lift arbitrary loads.

Look, there is a reason why people secure stuff on rooftops. What are you arguing here: That it's okay to leave shit around because the chances are low that it will kill somebody? Just stop with the flawed logic.

No, I have no problem saying securing stuff is generally a good idea. If nothing else it makes it harder for someone to steal it.

My point is the specific bad thing described is unlikely to happen. And sure I got a lot of knee jerk reactions but nobody actually did any kind of meaningful calculation demonstrating an issue.

Re: Show HN: $200 Solar Self-Sufficiency  Without Your Landlord Noticing

#150

Post by jldugger »

matt_wulfeck wrote: post #67
xsmasher wrote: post #30

Earlier quoted context omitted.

Those calculations also assume he'll use all of the energy it produces, every day, with no loss; it's a back-of-envelope best-case calculation, at best.

If we're getting into the nitty-gritty, then let's also include energy cost inflation into the equation. These numbers are for PG&E which is roughly equivalent for SF: 2001: 0.10c kw/h 2017: 0.28c kw/h (as per my recent bill) That's an average of 10% increase in energy cost per year ! https://www.pge.com/tariffs/electric.shtml

Isn't 2001 during the Enron fucking with the West Coast for profit years? A quick review of wikipedia suggests that in 2001 prices may have been held artificially low. A quote by Gray Davis seem instructive:

> "Believe me, if I wanted to raise rates I could have solved this problem in 20 minutes."

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