cbr
Joined 17 years ago
Karma
3,404
Submissions
1,146
Member since
Jul 2
http://www.jefftk.com
View on Hacker NewsRecent submissions
Comment · 8 years ago
> Curious about SPS + A/C
The SPS is rated for 2000W, best-effort. That gets you probably one large window AC. It will run when the grid is down and the sun is shining on your panels, which depending on how your roof is angled and what trees etc there are might or might not be enough?
It will have times when it loses power due to clouds. I believe when that happens the SPS turns itself off and you need to manually re-enable it by flipping a switch in the basement. So might be a lot of hassle.
Comment · 8 years ago
> Why propane? Because gasoline slowly degrades (polymerization) and needs to be drained, disposed of, and replaced with new (typically every year or so). Propane doesn't degrade over time.
If you have natural gas piped to your home then a natural gas generator is a solid option. Expensive, though.
Comment · 8 years ago
> They do have models that can function off-grid, and even models with attached batteries to handle surge loads and night-time operation, but these models are not as widely installed.
Talking to solar salespeople, they say it's not code to run your house off-grid directly on the panels, without batteries. I'm not sure why; maybe they think handling brownouts is too much of a problem?
We're planning to install an SMA inverter [1] that has a "Secure Power Supply" outlet in the basement that gives best-effort power during a grid outage. This seems to be the only option on the market that gives you some power when the grid is out without needing the very large (quoted at $10k for the smallest size) expense of a battery system.
[1] https://www.sma-america.com/newsroom/current-news/news-detai...
Comment · 8 years ago
> What about heat in a power outage?
Right now we'd have no heat. I'm thinking of putting together a small general purpose battery backup that we can normally charge via the wall but can also charge via the SPS on the solar system we're installing. I'd use it for whatever was highest priority; depending on time of year that could be boiler, sump pump, fans, or unexpected things.
Comment · 8 years ago
I looked into this some and found some of the most useful advice was for people going to Burning Man. For example: https://www.theplayalabs.com/shopping-list-solar
My understanding is that for anything big like a fridge (even a minifridge) the efficiency and reliability of standard well-optimized 120V AC appliances means it's worth it inverting to AC instead of sticking to DC. Lots of RVs use/used 12V DC systems so things are available, they're just not very good. Inverters are very efficient these days. Plus it's really helpful to have a way to run AC things you already have if you need to.
Though if you only want lights, I do see how DC could make more sense if you can either find or DIY the right electronics to handle the voltage issues.
Comment · 8 years ago
It's unfortunate that ImageMagick decided to call their primary command "convert".
Comment · 8 years ago
1. This uses the Image Magick command "convert" so it will work on any system that has it installed. I've only used it on Mac and Linux.
2. It isn't lossless, no. I think jpegtran can do this, but you'll need to first read the correct orientation out of the EXIF data and then give the right arguments to jpegtran. Since the loss in quality is tiny, I just use -auto-orient.
Comment · 8 years ago
I found several of these in Hollywood Cemetery in Richmond a few years ago and was confused by them: https://www.jefftk.com/p/assorted-pictures#tree-graves
Comment · 8 years ago
To fix these:
convert -auto-orient in.jpg out.jpgComment · 8 years ago
Author here: I don't know very much about how swamp coolers are used in practice, so I could easily be missing something. I do know that they're basically never used up here in the Northeast (Boston) because they work by increasing humidity and in the summer we tend to have pretty high humidity already. We also tend to have daytime highs high enough that the air leaving a swamp cooler would be warmer than the temperature of a structure that's been cooled overnight with a whole-house fan, plus more humid, which means during the hotter parts of the day you don't want to bring in outside air. So, how could a swamp cooler be used without increasing the daytime humidity of the house?
What I'm imagining is running a swamp cooler overnight to cool the structure of the house as close to the wet bulb temperature as possible, then in the early morning run it a bit in fan-only mode to bring in drier outside air (accepting that this will warm the house up a bit), and then shut the house up and turn the cooler off for the day.
What we currently do is run a whole-house fan overnight, and shut the house up during the day, with no swamp cooler. I'm trying to figure out whether adding some evaporation to the system could make sense.
Comment · 8 years ago
Japanese isn't as well suited to a keyboard as English is; a smartphone and keyboard are about equally fast for typing Japanese.
Comment · 8 years ago
>patients are known to be highly inconsistent when reporting their own alcohol consumption. Answers patients provide depend on many factors, including the doctor-patient relationship. And patients’ spouses often disagree with their partners’ assessment of their drinking. The MACH15 trial had some sophistication built in to it, including the use of random smartphone-based check-ins for patients. But while some evidence suggests that smartphone-based self-reporting on alcohol consumption often contradicts patients hindsight reports, MACH15 had no ability to tease out which patients would adhere to the smartphone check-ins, and which were providing accurate accounts of their consumption. In essence, the NIH was making a $100 million gamble that volunteers would portray their alcohol consumption accurately.
This doesn't seem like a problem with the study design to me. You're effectively assessing the effect of telling people to drink "zero" vs "moderate" alcohol as opposed to the the effect of actually drinking those quantities, but since one major use for a study like this is to figure out what doctors should be telling people this still seems valuable.
Comment · 8 years ago
> Based on past experience, it is estimated that between 1 and 2 people out of every 1 million people vaccinated may die as a result of life-threatening reactions to the vaccine.
-- http://www.who.int/vaccine_safety/committee/topics/smallpox/...
Comment · 8 years ago
Are they saying they were misquoted? I'm seeing them unhappy about the publicity, but that's not slander.
Comment · 8 years ago
Where did you read that? It can't possibly be right: the Pacific alone is 160M km^2.