solar panel output degradation?

I tried a good green LED at 3AM up in the cabin, where it's really dark on a moonless night. My eyebell threshold of detection was just about 1 nA.

I remember the first Cree SiC blue LEDs. We ran them at 50 mA for front-panel indicators.

And buy lots of solar cells and batteries to do it.

Setting up a national grid is an expensive luxury as soon as you can generate locally.

John Larkin thinks that the only way the Third Word can get a First World lifestyle is by doing it the same way the First World did.

Technology has moved on since then.

Some back of the envelope calculations using rounded numbers.

Assume 1000 liter = 1000 kg water tank, start temperature 0 C, end temperature 20 C (room temperature), delta-T = 20 C

Storage capacity 20 C * 4 kJ/kg/C * 1000 kg = 80 000 kJ = 80 MJ

Evening outdoor temperature 35 C, indoor (room) temperature 20 C , delta-T 15 C,

How much energy can be transferred from air to water with just a heat exchanger with no compressor ?

Assuming 4 hours cooling is needed after sunset, which makes 1300

on hour,

Next morning, when the air is cooler, use a solar powered compressor to chill the water back to 0 C.

The latent heat from 0 C ice to 0 C water is 333 kJ/kg,

To melt one ton of ice requires 333 MJ. Compare this with heating water by 20 C or 80 MJ.

Of course it is hard, just look at the specific heat and latent heat, However, the energy storage is huge,

In mains connected houses, what is the peak charge and what time of day it will occur.

On Friday, December 20, 2019 at 1:20:53 AM UTC-5, snipped-for-privacy@downunder.com wr ote:

What is a "dm?"??? I can't find this anywhere.

Water is 1 kg/l.

Air is nowhere near 1 kg/ml.

Is m? something non-SI?

I don't know what braindead newreader you are usingm but my posting clearly indicated

Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit

Lets try with 7 bit USASCII

Water density 1 kg/dm3, specific heat 4 kJ/kg/C Air density 1 kg/m3, specific heat 1 kJ/kg/C

A cubic meter is the volume unit in SI.

No, lights don't require 'more energy', solar gives us excess light during daytime so we use buildings for SHADE. A little time-shifting of natural light would work, OR we could design high windowed rooms like pre-1940 architecture.

Fans of the ceiling type are low energy, and effective.

Food doesn't require petrochemistry to grow, and 'getting crops to market' doesn't require long distance transport if you live in fertile regions. Some travel (wind-driven ships, slow barges with a towpath) have near-zero energy requirement, we just use fast and energy-intensive modes for the convenience.

A bicycle can suffice for personal transport and routine shopping tasks, and takes just enough oil to keep the chain from freezing.

So, 'energy' in large quantity can become a historic blip, a brief Energy Age, but light, comfort, and commerce needn't SCALE with power consumption.

With organic farming, very little external resource input (such as fertilizers) is required. The downside is that the yields also drops.

As long as the population density and population growth is kept under control, preferably by family planning but in the worst case by wars, the farm yield would support the local population.

Even organic farming requires a lot of work, typically done by horses or some engine driven equipment, which both needs some energy input from hay or biofuels or solar panels.

There is the question of human powered bike and electric powered bike.

Powering the bike with human power will require input from some (expensive) food sources, so some solar/wind sourced electric bike might be more efficient in the long run.

Of course, the same tradeoff is between a horse and electric tractor in agriculture,

This might be the case, if the huge uncontrolled population growth

requires about 2,1 children reaching sexually active age born from each woman. In Europe, the rate is much below this ratio but unfortunately in Asia and especially Africa, the population growth is much larger and hence unsustainable.

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rate

But it's declining rapidly, and the route to get it to decline even faster is well known - educate women.

Europe has gone through the demographic transition

The US isn't quite there yet, but while they have got universal education i t's fairly obvious from what gets posted here by Americans that the quality of that education is very variable.

Cool. Tell that to the malnourished kids. They can bicycle for their "routine shopping tasks." All they need is a bicycle, a path to ride on, somewhere to shop, and money to buy food.

On Dec 20, 2019, snipped-for-privacy@downunder.com wrote (in article):

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The powers of three render correctly in one newsreader, but not the other. Problem is that superscript three is a unicode symbol, and unicode is unevenly implemented, for a large number of reasons.

everywhere.

The above analysis misses a large component, the thermal mass of the plaster walls and ceiling, which vastly outweigh the air within the rooms. Floors, usually being wood or wood covered, are less important.

The classic low-cost air conditioning approach is to use a window or attic fan to pull cool air through the house until about 2 or 3 AM, and to close the house up during the day, using the cold stored in the walls to keep cool.

Window fans optionally came with a thermostat that was used to turn the fan off when the night air turned too cold.

I lived in Baltimore and Washington DC for about fifteen years, and used a

when things were reasonably cool.

I also had a window air conditioner that I kept in the basement during the winter, and humped up and down the stairs to the second floor with the seasons. For the last five years, I left the air conditioner in the basement

- one does become accustomed to the heat. Having lived in the Boston area since 1982, probably would be A/C dependent down there now.

Joe Gwinn

Unless you changed something it is rendering just fine now. But even so dm ^3 is a weird unit. Why not liters (l)? So kg/l would have been clear.

Safer yet to not use weird units. It's been a long time since I was in col lege where small differences were pounded into my head, but liters are lite rally an equivalent expression of cubic linear dimensions, no? I ask this because something is nagging at the corner of my brain that a cubic cm, a m l and certainly a gram of water are not all the same exactly. I know they were set to be the same at the time, but better measurements make the densi ty of water a bit off. All the online references say 1000 liters is exactl y 1 m^3.

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His analysis was just attempting to estimate the heat entering a building w ithout considering the air mass is not the way to do it. If the heat is co ming from the outside through the walls, these walls will be warmed/cooled and so will also need to be considered. If the heat is coming through the windows or air leaks or internally generated, it is not so much a matter of heating/cooling the walls.

I've read that winter heat losses are primarily through windows in some hou ses and the attic insulation in others. So no clear winner.

Summer heat seems to be from insolation so southward facing walls and roofs and windows if not shielded by blinds or shades.

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Not sure what part of DC/Baltimore you lived, but there is about a month ea ch year of hot weather when a window fan is just pissing into the wind no m atter what time you use it. I often leave my A/C off and run fans at night , but it doesn't really cool the house, just not so horribly hot so by 3 AM

ent

A second floor would be warmer than the downstairs, so yeah, A/C would be n ice. I've actually left off the A/C the last couple of years to assist in my weight loss efforts. I let the heat take my appetite and lose some 15 l bs. over the summer months. There are a few hours each day when I lay arou nd doing nothing just like the cats. I get it now. lol

The Latin upper case letter A (U+0041) is also a pesky Unicode symbol by that definition :-)

Superscript 3 has been at that position in all ISA Latin variant, in Windows 1252 and originating from DEC MCS (VT-220 1983).

Web browsers have internally supported Unicode for decades (internally either UTF-8 or even UCS-2/UTF-16), so why not Usenet readers, especially when the code page is clearly tagged.

It is not safe to use USASCII, especially the up arrow, since that character position is used for a national letter in national variants of 7 bit IA5 / ISO 646. All the characters #$@' {\}^_{|}~ are risky and should be avoided.

It would be safe to write dm**3 even in IA5.

On Friday, December 20, 2019 at 3:07:15 PM UTC-5, snipped-for-privacy@downunder.com wr ote:

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If that is so, how do people use those same computers to write programs???

The cubic decimeter (actually 0.001 cubic meters) is the official SI volume unit. The liter/litre is an accepted non-SI unit.

Use FORTRAN or COBOL, works fine even with 6 bit character codes (upper case only).

Seriously, when using 7 bit terminals with some national character set variant, the programmer has to know which national character key to press to generate the correct character code.

The compiler is interesting in the character code, but not how the glyph might be rendered.

When printing on a 7 bit printer, some of the language structured such as [ | ] { } are printed as some national character. Using multiple printers set to different national 7 bit codes the printout would look different in each case.

today, UTF-8, but before that "trigraphs"

Too bad you didn't write cubic decimeter. That at least would have been understandable. Had you written liter no one would have had any issue with it and we would not be talking about this.

Why is it important to use SI units?

He did!

(as a google gouper you'll need to engage a fixed pitch font to read the following, in the settins menu (looks like a cog, top right below your ID emblem.) select "view origial")

MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit

this is a partial hex dump of the message as it arrived here (but the offsets are in octal):

s sp u s i n g sp r o u n d e d sp 6360 6e 75 6d 62 65 72 73 2e 0d 0a 0d 0a 57 61 74 65 n u m b e r s . cr nl cr nl W a t e 6400 72 20 64 65 6e 73 69 74 79 20 31 20 6b 67 2f 64 r sp d e n s i t y sp 1 sp k g / d 6420 6d b3 2c 20 73 70 65 63 69 66 69 63 20 68 65 61 m 3 , sp s p e c i f i c sp h e a /\ || 6440 74 20 34 20 6b 4a 2f 6b 67 2f 43 0d 0a 41 69 72 t sp 4 sp k J / k g / C cr nl A i r 6460 20 64 65 6e 73 69 74 79 20 31 20 6b 67 2f 6d b3 sp d e n s i t y sp 1 sp k g / m 3 /\ ||

high bit and rendered it as "3" like it would render 0x33)

it appears that that google groups, is defective. displaying

as: Air density 1 kg/m?, specific heat 1 kJ/kg/C

I think he was just going for symmetry,

Also digraphs in Pascal, for instance

(* This could be a Pascal comment *)

Table (. Index .)