MichaelApproved

Great points across the board. Thanks!

> Will you build a bridge that’s inexpensive, but will have to be replaced in 25 years, or will you spend twice the money for more concrete and more steel to make it last for 50?

> > Of course the second (which is what is actually usually done) the issue being that in real world after 50/60/70/80 years the bridge won't be replaced/repaired.

Assuming the bridge would actually be replaced at its actual end of life (25/50 years) and assuming a horrible return on spending (double money for only double the life), I'd say the 25 year option would be better in many (not all) cases.

From a cash flow perspective, it'd be helpful for a local government to avoid immediately spending on infrastructure costs that could be delayed for 25 years (when the lower cost bridge would be due to be rebuilt).

From the unknown future perspective, the city/town population could possibly change (bigger/smaller) 25 years into the future.

If the population grows, replacement bridge would need to be bigger and they could use the saved money to build a bigger one. Of course, if the population shrinks, they could spend less on a smaller replacement bridge.

Again, this assumes a poor return on increased spending. Doubling the costs to double the life. If you could double the costs and triple the life or increase the cost by only 50% to double the life, the equation favors going with the longer term bridge.

What about UPDATE performance?

Your article and the parent one are explaining performance improvements related to INSERT and SELECT but what about the improved performance for UPDATE?

I wrote a long comment[0] on yesterday’s PostgreSQL post related to column order optimization with regards to UPDATE.

My information was 20+ years old and I figured it was horribly outdated but these articles make me think it could still be true.

The TLDR is you want to put variable length columns at the end because it makes UPDATE more efficient. My theory was it’ll be less likely the DB would need to move data around when updating the variable column contents.

Less data being moved = improved performance.

Seeing these articles means I was right with regards to improved performance of INSERT/SELECT but I wonder if I’m right about improved UPDATE performance.

Anyone know?

[0] https://news.ycombinator.com/item?id=32055596

> Why would you be trying to prevent the DB from reordering the data?

Sure. “Reduce the need” would be a better word than “prevent”.

If I can do a good job organizing the table columns (as described above) it’ll lower the need for the DB to reorder data.

Reduced need to reorder, improves performance.

> the database should be able to reorder the data in whatever way it likes

My point was that you’re trying to prevent the DB from reordering the data because there’s a performance cost when that happens.

Based on my understanding of DB storage (which is decades old and as I write the comment my explanation seems stupid but it’s what I was taught. Please someone correct me).

Image a table with the following:

id (int), title (varchar), created_date (date)

That data is stored in a similar order on disk (is this still true?).

So, if the initial insert has a title of 10 characters, then the date will get placed after those 10 characters on disk:

Int, 10 characters, date

Later, the row is updated with a longer title of 500 characters.

Because it’s longer, you now have to get more space for the title on another part of the disk.

Since there are columns after the title, it’ll either leave dead space where the old 10 character title was or it’ll need to move those other columns too.

I can’t remember which I was taught. I just remember that columns after variable columns get impacted when the data in a preceding variable column changes.

If the title were at the end of the row, the db could expand the data without needing to move other columns over (if there happened to be available space right there).

If you were updating with a shorter value, it could shorten the row by moving the terminating character to the new shorter location, freeing up the space the longer title was using.

Bottom line is you want to keep variable columns which get updated most frequently towards the end of your table structure.

Knowing which column that would be isn’t always clear when creating the table.

Again, this understanding was taught to me over 20 years ago. I’m probably remembering parts of it wrong and DB storage has likely (hopefully) advanced since then.

In her video, she claims that linking to studies is the proper way to present news.

Then she quotes a study and doesn’t link to it in the video description. She doesn’t link to this post either.

I like the videos she makes explaining scientific concepts but her criticism videos tend to miss the mark with me.

I think it’s meant to provide an emergency source of water for drinking.

You wouldn’t want to use this for a large population for a prolonged period of time because you’d have trouble disposing of all the salt waste.

Figuring out how to handle the salt byproduct is a critical part of long term desalination.

They pass the initial law as opt-in. That allows them to fund the initial infrastructure.

Then they make it out-out. The change doesn’t get much attention because the funding is already in place and “think of the children”.

Then they add political thought crimes to the filters.

Then they make it so you can’t opt-out.

Then I’d say you walked 1.5 miles in 30 minutes. The equivalent to saying generated 15 watts of power over 30 minutes from a panel that’s providing 30wh of power.

I’m assuming what I’m saying is wrong, I just can’t spot it. Thanks for the help.

Thanks. I’ll need to read that a few times because I struggle with this constantly.

I almost instantly hit the edit button after I post a comment.

OP here. Thanks for understanding what I’m trying to say and putting it in the correct terminology.

However, I think I’d still make the same mistake in the future because I don’t understand how to express what the (assumed) 50 watt rated panel is generating over half an hour.

If it’s running at 60% efficiency then it’s generating at 30 watts per hour.

After an hour of running, we’ve accumulated 30 watts of energy.

If we only ran it for half hour, we’d have 15 watts.

Dividing that out tells me that 3 watts of energy will provide 1 once of water.

Does it matter if those 3 watts are provided over an hour via a 3wh power source or over 10 minutes via a 16wh power source?

Good point. I wish articles like these would include figures. I’d love to know what they calculate RO efficiency to be at small scales and how far away they are from beating it.

Sure, that might be boring for some readers but they could throw a couple of sentences about it at the bottom.

Thank you. And you’re right, I am amazing ;)

But seriously the main reason I write these comments is to work through my thoughts as I try to articulate them and get feedback on what I’m thinking.

I’m actually happy when someone points out a mistake because I learned something.

When I’m right, I haven’t gained anything. Sure, my ego enjoys the satisfaction of being right but my already inflated ego doesn’t need anymore stroking.

You’d have to raise them up pretty high to get them colder than the dew point.

The energy it’d take to raise and lower the material would make it cost prohibitive.

I considered that the balloons would be a balancing force but don’t forget the rope length changes as the balloons go up and down. That changing length shifts the weight around. You can’t be balance against it.

Would dry regions that need water have enough cloud coverage for that to be viable?

My guess is that any place with sufficient cloud coverage is already getting enough rain water to satisfy their needs.

The article claims 3x more efficiency in a confusing sentence:

”Their prototype generates drinking water at a rate of 0.3 liters per hour, and requires only 20 watts of power per liter.”

So the unit only produces 0.3 liters an hour but if you wait 3 hours and provide 20 watts of power (7watts/hour), you’ll have a full liter.

For these small amounts, I doubt pumping it back out would be an issue but is that what they’re doing?

I thought the metal plates were collecting the salt but the article and video don’t make it clear.

It wouldn’t be the first time I made a mistake like that by not clearly identifying my units but I think I got it right.

Let me rephrase and use watt/hour units.

I was assuming it was a 50 watt panel that would only produce 30wh from the weak winter sunlight.

Divide 30wh by two (since it was only ru Ning for half an hour) and get 15 watts generated to purify 5 ounces.

Had they let it run for the full hour, they’d get 10 ounces from my assumed 30wh of energy the panel produced.

30wh divided by 10 ounces would be 3wh per ounce (or unit of water produced).

How many units of water can be produced by 1kwh? Let’s divide 1,000wh by 3wh to get the result of 333.3 units (ounces) produced.

I was so quick to criticize technology that I completely overlooked those points. Reading the article again, it’s embarrassing to see that I missed it when they were emphasizing it so much.

I have one more lingering criticism that I don’t think they addressed (I reread it twice).

What happens to the salt after it’s removed? If they don’t have a filter, where does it go? Do they pump brine water back?

“Atmospheric Water Generators”

At first I thought you were just using a marketing term for dehumidifiers but I looked it up before posting.

I see that term is used for tight mesh fabric that’s hung vertically as a passive matrix to collect condensation.

While those are actually game changers, they unfortunately only work in special regions that have the needed weather and topography to make them work.

I think there’s only one place on earth that has the perfect combination for AWG: weather, drought, and humidity. It’s an awesome technology for them but that’s about the extent of it.

I’ll try to find the region and update my comment with more info.

Edit: here’s a video that talks about what I think you’re talking about.

https://youtu.be/YxRONAZoMDk

It’s providing water in the Atacama Desert near Lima Peru.

Edit 2: They’re called fog collectors and apparently Morocco uses them too. https://youtu.be/0F7CQMd6mQ4

Edit: I wrote out the comment below criticizing the efficiency of this device, when compared to reverse osmosis RO desalination (100x less efficient).

However, they’re not trying to be more efficient than RO devices, they’re trying to be more compact, portable, and avoid the need for filters.

They’re solving for a different problem than I was measuring them against.

In my race to criticize, I overlooked those key details.

I still think my comment is worth reading to learn about the efficiency differences but I guess that measurement is not important for the viability of this technology.

Original criticism below: ———————

I’m skeptical about how practical this actually is.

While it’s refreshing to see a drinking water solution that isn’t based on inefficient dehumidifier technology, this still seems impractical.

From the demonstration video, their portable ~50 watt solar panel took 30 minutes to get a few ounces of drinking water.

It looked like a cold winter day, so let’s be generous and assume the panel only produced 15 watts of power during those 30 minutes.

Let’s also be generous and say they got 5 ounces of water.

That means they produce 1 ounce of water for every 3 watts.

That’d be 333 ounces per kWh.

To put that into perspective, a desalination plant produces more than 100x that much.

Yes, there is lots of additional infrastructure to consider with a traditional desalination plant but It’s not like this solution wouldn’t require the same complexity to scale up.

I don’t remember the cost of dehumidifier drinking water “solutions” but I think this is slightly more efficient than those horrifically inefficient solutions.

That’s what I was getting from them but their marketing isn’t clear.

Use cases would be very helpful.

No, that’s not what I’m trying to argue.

People who claim “standardized test is systematic racism” are not necessarily the same people who think “asian americans being discriminated at ivy leagues even with good standardized test score is not seen as systematic racism.”

You are taking two different points of views which are made by two different groups, reducing their arguments down to practically nothing, and pretending they’re being made by the same group.

You are mutating the arguments and inventing a boogie man. Textbook straw man argument.

> Often sensitive debates that don't follow a certain mainstream narrative are brushed off as strawman

There’s a reason for that. It has nothing to do with following a mainstream narrative or not. It has to do with the false assumptions in the basis of your questions.

I’d say you’ve got more straw men in that loaded question than farmers have in their field.

You’re taking poorly summarized opinions and pretending that combination of opinions are held by a group of significant size.

And the damage done to consumers would also be enormous.

For whatever faults they might have, the regulations are intended to protect consumers, not harm them with a scorched earth plan out of a libertarian fantasy.

There are plenty of ways you can punish a company for wrongdoing without risking the consumer as much as that idea would.

Since you’re conducting an experiment, I’ll provide my feedback. Usually I’d downvote a simple comment talking about being first to post but you also provided a link to the previous discussion which I thought was worth upvoting.

Regarding the talk of downvotes, I’d usually downvote for all the classic reasons but you turned it into an experiment which will spark discussion, so that’s an extra reason to upvote.

I take my upvote/downvote powers very seriously. Or maybe a bit too seriously?

Edit: after making this comment I clicked and saw your post got no comments, so I must now consider it to be a “simple” comment with little value.

Hmmmm. I guess I’ll just take back my upvote but refrain from downvoting.

If we're talking about chimney efficiency then we should talk about including heat exchangers within the chimney walls.

Jamie Hyneman of Mythbusters added one to his house and talks about it here https://www.youtube.com/watch?v=0T3nIk3S8Wc