I have a few solar panels installed in 2008.
They are mounted in an extremely bad location: on a south facing wall, without proper airflow on the back side.
They continue to work, even if output is degraded. Newer planels installed in the same location overheated and their elements cracked, indicating inferior manufacturing quality, but the oldest batch is not showing this symptom.
If you don’t mind buying from Guangdong and being hit with import and customs fees, then on Linux, this gadget presents a standard V4L (Video4Linux) USB camera.
https://www.aliexpress.com/item/1005007938478574.html
The cable is delicate, you’d have to find a way to secure it against damage (e.g. tape). For the 256 x 192 pixel sensor, focal length 4 mm will get you an ordinary field of view (e.g. 45 degrees), while 9 mm will get you a very narrow field of view (e.g. 20 degrees). Grayscale image, very fast frame rates, automatic calibration against a shutter (occasional sub-second stops in video).
Note: never ever point at the Sun. It has poor solar protection, I almost ruined it when my code erred and scanned across the Sun, leaving a massive black track which took several hours to fade. The shutter closes when it sees the Sun, but not fast enough.
Coincidentally, it is cold here too. Walked around the house with a USB drone camera. Window edges are radiating like crazy. There was no difference between a window with shades down vs. a window with shades up (I hoped to find a difference, but was disappointed). However, edges need considerable extra foam.
What makes me worry is the size of the “reflector”. I wonder what symbol rate it is possible to get if the “reflector” is literally everywhere above you - the time delay between start of reflection and end of reflection might be considerable.
I found a resource with practical advise about using NVIS, including using meteorological data (ionograms) to determine the best frequency, antenna diagrams and such. (His drawings are in Spanish, but I think most English-speakers can decode Spanish antenna diagrams with a few clues, since meter is metro, and frequency is frecuencia.)
https://www.ipellejero.es/hf/NVIS/english.php
Some additional interesting antenna designs (vertical yagi on ropes, spiral antenna, etc) and propagation shemes, can be found in this research paper.
They have a passage which addresses data rates, and the data rates are poor…
In [110] two alternative channel access technologies are tested and compared in wireless mesh networks: Automatic Link Establishment (ALE) and fixed-frequency MAC protocols. These are also described in the book of Johnson et al. [111]. In [112] we find measurements on a MIL-STD-188-110C [113] link over distances of up to 160 km, providing the users with bit rates up to 9.6 kbps in 6–9 kHz RF bandwidth. The standard gives the option of selecting bandwidth and modulation, and includes wideband modulation with up to 24 kHz bandwidth with elaborate coding and interleaving.
So, some military radios use a narrow slice of 6…9 KHz for each channel and push 9 kilobits per second. Widening the slice used will give more speed. Enough to send SMS, I would say. A text of 1000 characters could be 8 kilobits, and would require initial air time for 1 second (+ exponential back-off resends, most likely). Let’s assume a total of 3 transmission events per message. An hour contains 3600 seconds, divide by 3 --> a channel at 100% capacity could accommodate 1200 messages per hour.
Thanks for dropping the abbreviation. :) For those who want text:
https://en.wikipedia.org/wiki/Near_vertical_incidence_skywave
Summary for those in hurry: with NVIS, the ionosphere is your reflector, but you must use bloody low frequencies (e.g. 8 MHz in daytime, 4 MHz at night, because the ionosphere changes properties in sunlight). This will require loooong antennas (which may be horizontal, e.g. between trees) and the full wavelength is about tens of meters long, so you can’t really use full-wave antennas (quarter wave is practical) and all of this will limit the data rate considerably. Overcrowding of the narrow range of good frequencies may occur if it becomes popular.
Disclaimer: not an engineer, but I’ve built a house and squatted half a dozen.
Questions:
Ideas:
don’t remove woodwork until you have investigated the cracked concrete, removing bits that come loose without hammering; I would determine for sure if the concrete is fully compromised or partly so
if concrete is only partly compromised, one method would be cutting off the compromised layer (e.g. with a cutting disc) and casting a filler
if you end up removing rebar, you should re-calculate the load bearing ability of the beam as if the filler was nothing (if there is a choice, preferably clean and don’t remove rebar)
if it’s critically important and cannot be removed, I’ve seen concrete structures renovated by cutting off parts with a pressure sprayer (not a method one would use in domestic settings, sprayers that cut concrete are expensive and dangerous), cutting off bad rebar with a cutting disc, cleaning the end of good rebar, tying new rebar to the old, and casting fillers
after this you’d have a concrete beam that can be more effectively supported from below (it won’t compress at the crack)
if you use a jack and a pillar, prefer a mechanical (not hydraulic bottle) jack, people sell and rent such instruments for temporary support, it’s a steel pillar made of 2 parts that you rotate against each other to extend
in a pinch, you can create a screw-type jack from a wooden pillar, a short length of serious threaded bar (e.g. M24, M32) and some appropriate washers and nuts
your plan to offer support from the center and replace the framework from sides makes sense
if water if a frequent visitor there, use treated wood (or make sure that water doesn’t return)
This actually sounds great, if the solvents are widely available and have as low footprint as the material itself (bamboo).
Production involves two eco-friendly steps. Deep eutectic solvents break apart bamboo’s hydrogen-bond network into smaller cellulose molecules. Ethanol then triggers molecular reconstruction, reforming dense hydrogen bonds and creating a tough, uniform plastic. This ethanol-mediated restructuring produces a chemically modified cellulose network that delivers exceptional mechanical performance.
The material can be shaped through injection molding, compression molding, and machining, making it compatible with existing manufacturing systems. That versatility is crucial because new materials must fit into current industrial pipelines to be commercially viable. Tests show that the bamboo plastic outperforms commonly used engineering plastics such as ABS and polylactic acid, making it suitable for rigid applications requiring durability and heat resistance.
Sadly, they don’t mention the solvents, only the catalyst for hardening (ethanol - which would be OK).
I believe the original article is this:
In this case, the solvents would be:
By employing a hydrated ZnCl₂/formic acid deep eutectic solvent (DES), we disassemble the native H-bond matrix of bamboo cellulose into a homogeneous molecular system. Subsequent ethanol stimulation triggers the rearrangement of cellulose chains, fostering dense, ordered H-bond interactions between hydroxyl and formate ester groups (Fig. 1b).
Now, formic acid is ecologically OK. Zinc chloride, not entirely so (zinc is not a substance to waste or throw around), but if it’s recovered in the process then it would be OK. Coincidentally, their process includes recovery of zinc chloride:
DES recycling
The spent calcium chloride solution and the ethanol used for washing the gel were collected and mixed. An equimolar amount of 48 wt% sulfuric acid was then added to precipitate the calcium ions. This mixture underwent vacuum filtration to remove the precipitated ions, followed by rotary evaporation of the residual liquid to eliminate the ethanol and recover the recycled DES.
Recycling and reuse process of BM-plastic The recycled DES solvent (ZnCl 2 /FA) was obtained by adding equimolar mass of sulfuric acid to precipitating CaCl 2 , and steaming out ethanol. The recycled BM-plastic was prepared from Re-DES and BM-plastic chips, through the molecular system and molecular gel preparation process mentioned above, as well as the ethanol stimulation process.
So, overall, this all sounds sensible to me. Whether it’s economical, I cannot tell so fast.
Opinion (shooting from the hip here, may be off the mark) - mycelium was used to replace glass fiber epoxy.
In the research paper, I see among other items a copper- or gold-plated antenna constructed on a sheet of mycelium, and it falling apart over time (11 days).
As a result, this seems to me like a technology to use if you must spew disposable ciruitcs in nature and want them to maximally degrade. Definitely not the tech to use for things that must work 20 years.
Then I would suspect partial shadow. Is there anything near the lower string that could cast a partial shadow on the panels?
I notice these green curved lines on your diagram. They resemble what people usually draw to denote tree cover on a map. If they are trees, how tall, how far, and how high up are your panels?
Short answer: snow lingers longer on the lower part of your roof. The flatter the roof, the bigger the difference.
I’m not a representative sample, but…
…my hobby is my job. I learnt to code and to build stuff as a hobby, and now it’s my job.
I don’t think I could exist without designing and building something interesting. Even if I know that someone out there does it better. Because I want to understand the process and be able to alter it. I’m OK with someone else doing something that I find boring. If the subject interests me, I want to do it myself.
As for the concept of being free, if someone said “you’re free now”, I would ask “in what sense - am I free to stop paying taxes and repaying debt? can I finally squat land, start a license free mobile phone network and start practising medicine, or free in some other sense?”. I would likely conclude that I’m not free yet, and mutual dependencies are in fact quite numerous.
About those solar heat collectors: I can confirm it works because I’ve built one. It’s not as efficient as collectors that use coolant and a compressor system, but it’s very reliable and cheap.
I will second the opinion about aluminum recycling. Making aluminum from alumina is very energy expensive. Melting down cans is efficient compared to that.
P.S.
Notes about cans: if one wishes to make a model engine (e.g. compressed air engine, Stirling engine, lightweight models that work but cannot produce practical amounts of energy), some soda cans fit inside each other with extremely tight clearances (on the order of micrometers) and there is no seal, they slide on a layer of air. Of course, they have to be cut (with scizzors) and have to be kept clean, and despite keeping clean, there is abrasion (they wear down).
It’s very hard to machine a part to those tolerances. If a piston-cylinder system does not have to withstand detonation (not an internal combustion engine) and doesn’t have to do heavy work or last long, cans are a neat way to quickly get matching pistons and cylinders for experimenting.
(examples cannot be relied on as manufacturers have different production lines and production batches)
Most likely, it could help slow the process (buy time for firefighters to arrive) in some percentage of cases where a cell’s surface has been mechanically punctured.
Provided large amounts of nitrogen and an already empty battery (devoid of chemical energy), in a small percentage of cases, it might prevent a fire.
However, having seen a lithium polymer cell heat up from mechanical damage (a drone crash), I can confidently tell that very high temperatures can be achieved without oxygen. They’ll just be even higher with it.
Out of curiosity I checked if their sources properly accounted for confounding variables (e.g. age, because the global population is aging). I didn’t check all, but all the sources that did I check accounted for age properly.
Then I scanned some more. To bring a medical viewpoint into the discussion, took a particularly close look at one of the referenced studies of 67 health risk factors, to determine if it’s stress, pollutants, communicable or environment-triggred disease that is harming people most.
The factors dishing out most harm seem to be diseases with a lifestyle / stress component (high blood pressure), behaviour patterns with a stress component (overconsumption of food and intoxicants, primarily alcocol and tobacco), and only after these comes home air pollution (cooking with open fire in developing countries). Outdoor air pollution (“ambient particulate matter pollution”) isn’t in the top 5, but one one diagram, it’s factor number six.
(Reservation of judgement: there’s not enough data yet about chemicals in the food chain. Pesticides and microplastics definitely need attention, there is absolutely no reason to expect no effect. The effect has to be measured and summarized.)
Quoting the relevant passage from “A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010”
Findings: In 2010, the three leading risk factors for global disease burden were high blood pressure (7·0% [95% uncertainty interval 6·2-7·7] of global DALYs), tobacco smoking including second-hand smoke (6·3% [5·5-7·0]), and alcohol use (5·5% [5·0-5·9]). In 1990, the leading risks were childhood underweight (7·9% [6·8-9·4]), household air pollution from solid fuels (HAP; 7·0% [5·6-8·3]), and tobacco smoking including second-hand smoke (6·1% [5·4-6·8]). Dietary risk factors and physical inactivity collectively accounted for 10·0% (95% UI 9·2-10·8) of global DALYs in 2010, with the most prominent dietary risks being diets low in fruits and those high in sodium. Several risks that primarily affect childhood communicable diseases, including unimproved water and sanitation and childhood micronutrient deficiencies, fell in rank between 1990 and 2010, with unimproved water and sanitation accounting for 0·9% (0·4-1·6) of global DALYs in 2010. However, in most of sub-Saharan Africa childhood underweight, HAP, and non-exclusive and discontinued breastfeeding were the leading risks in 2010, while HAP was the leading risk in south Asia. The leading risk factor in Eastern Europe, most of Latin America, and southern sub-Saharan Africa in 2010 was alcohol use; in most of Asia, North Africa and Middle East, and central Europe it was high blood pressure. Despite declines, tobacco smoking including second-hand smoke remained the leading risk in high-income north America and western Europe. High body-mass index has increased globally and it is the leading risk in Australasia and southern Latin America, and also ranks high in other high-income regions, North Africa and Middle East, and Oceania.
My personal conclusion: it’s not pollutants harming us yet. Pollutant densities may well increase (but many are decreasing, e.g. people are cooking less with gas and solid fuel) but our social conditions are stressful as shit, and that encourages certain behaviours which have an evolutionary factor.
E.g. people are prone to over-eat when they have plentiful food, even if the food is junk and there’s no need to eat more. A sedentary lifestyle and driving instead of walking then doubles down on that. People are prone to relieve stress by consuming tobacco and alcohol, despite it harming them. Our ancestors didn’t have an unlimited access to food, booze and stuff to smoke for a passtime, and didn’t evolve defense mechanisms against such behaviour patterns.
But as usual, culture getst to be the first responder. Genes will take millenia to get anything done, but culture can get things done in decades. Awareness of how people harm their health, and awareness of how society may be encouraging self-harm, needs to spread.
May have been a good post, but in the wrong thread. :D
deleted by creator
I would likely try the methods of car headlight repair:
However, since I see that the sink has a glossy surface… I would be deterred by that. The method I mention may reach a layer which isn’t burnt, but will wear off glossy finish and there’s no certainty of it returning in the same tone after polishing is done.
What paint to use - sorry, no idea.
In case humanity forgets about how to make CPUs, some folks would still remember how to make stateful relays, magnetic core memory, punch cards and pneumatic logic valves.
It would take a bit of time from there back to a CPU.
I cut aluminum with mine (and professional aluminum sellers cut theirs with their saw, but it likely costs thousands), but I will second the “be careful” part.
Aluminum can snag your saw blade (especially if you use a blade meant for wood, which I don’t recommend because it also produces messy output). Snagging can have dangerous results (saw jumping upward and losing teeth or more in the process).
Ensure the work piece is clamped down very well. Ensure that the saw is either on a large level surface or better yet - bolted or clamped down. Ensure that the saw jumping cannot hurt you in any way.
When cutting aluminum, push very gently. And when the raw material gets too small, don’t try cutting the last little piece. Small working material will increase the chance of accidents. I set my limit around 20 cm.
Heyva Sor is real and if you can, I am sure they welcome any help. :)
https://en.wikipedia.org/wiki/Kurdish_Red_Crescent