HardCounter t1_j23jocj wrote on December 29, 2022 at 11:49 AM

Reply to comment by nslenders in Lego world map of energy to harvest water from the atmosphere [OC] https://doi.org/10.1039/d2ee01071b by WaterScienceProf

How are you going from 1kWh/L to 50Wh/L? You aren't reducing the amount of water harvested, you're just reducing the power for some reason. 50Wh would be 1/20L with a direct conversion.

Am i missing something?

nslenders t1_j23mb4a wrote on December 29, 2022 at 12:20 PM

3600Kj is 1Kwh. And 1kg is 1L. But the graph shows values from 0Kj/L till 280 Kj/L

Since 3600Kj is not on the chart. Taking a value that I can easily divide, being 180Kj/L. Would give me 1/20th of that 1Kwh. Or 50Wh/L

The map has values higher and lower, but 180Kj/L looked like a reasonable middle ground to calculate. Taking 1,5x our 180Kj/L would give 270Kj/L, or almost the top values. And is still only 1,5x 50Wh/L or 75Wh/L.

HardCounter t1_j23nv2c wrote on December 29, 2022 at 12:37 PM

I guess i don't know what you're trying to achieve.

Pick a number between 1 and 280 and it's on the chart somewhere, no math required. 50kJ/kG is on there somewhere, so is 83.4kJ/kG since it seems to be a continuous scale. 280kJ/kG or so seems to be the maximum for Earth. I'm not sure why 3600kJ/kG entered your mind, or what planet that would apply to.

nslenders t1_j23oy44 wrote on December 29, 2022 at 12:49 PM

My mind does not think in Kj. But if u tell me something uses as much energy as a 50W lightbulb for 1h. I know what that means.

I do know that 3600Kj equals 1Kwh. So I used that as an intermediate step to do the conversion. It does not have to be a relevant value on the map.

The reason I found the values low. Is that I have a big dehumidifier that uses 2000W. But it does not give me 40L every hour. But OP already explained that these are theoretical minimum values.

HardCounter t1_j23rmj8 wrote on December 29, 2022 at 1:15 PM

2000W? Is it industrial strength? You'd probably get a lot more water if you put the dehumidifier outside, though.

> Portable dehumidifiers typically consume between 30 and 50 watts while whole-home dehumidifiers can use up to 250 watts per hour.

https://www.perchenergy.com/energy-calculators/dehumidifier-electricity-usage-cost-to-run

I also found this:

> On average, a home dehumidifier collects five gallons of water per day.

That's about 19 liters per day inside an already dehumidified home. That comes out to about 315 watts per liter in a relatively low (30-50%) humidity environment. That's not too bad.

I should get a dehumidifier in case of zombie apocalypse.

Fhotaku t1_j287bsz wrote on December 30, 2022 at 9:56 AM

I did the legwork for a phd project that involved comparing indoor dehumidifiers efficacy on AWC in a desert. The cost varied wildly, in the 10c-4$/liter range, but that also included tests at 5% humidity and 120F outside, and others while it was raining.

Most places could use active systems like this for cheaper and cleaner water than they're currently getting. I will mention though, the refrigeration based dehumidifier collected every damn particulate in the air with it. It definitely needed filtration. Even moreso, this water is salt-free, and you can't live off that. These are costs to consider when using AWC.