https://jameshrisho.com/2020/10/making-laundry-less-terrible...
Edit: Consider also that the shorter you run the dryer for, the shorter you are running the (substantial) motor and fan, as well as less time spent heating the shell of the dryer and the air surrounding it.
Edit: 20:1 mentioned here https://qr.ae/pGNTie
Total power usage for full heat is (5000W + 250W) * 0.5h = 2625 Wh
Total power usage for half heat is (2500W + 250W) * 1h = 2750 Wh
So the big question remains, does lower heat dry clothes more efficiently, and if so, how much?
The Stack Overflow answer you linked raises some interesting points, but doesn't seem rigorous.
You'll notice this in heat pump dryers. They cannot generate the same amount of heat. They take way longer to dry the clothes. But they're way more energy efficient than other forms of dryers.
Edit: I thought of another example. Heating your home with hot water running through radiators. It's significantly more energy efficient to reduce the temperature of the water. This outweighs the additional time it takes to heat up your home. There are various drawbacks and considerations though, e.g. if the house has terrible insulation (noticeable draft) then it'll not be beneficial. There's various other things that'll significantly reduce energy usage, this while anyone would assume that generating heat is already very efficient.
Edit: Also it's not that using lower-temperature water to convey heat is somehow more efficient, the thing with heat pumps is that they are more efficient at heating things to a lower temperature. If you're burning gas it doesn't really matter either way, you just get the energy out you put in.
Edit: too much metal on clothing...
https://www.energy.gov/eere/articles/no-heat-no-problem-ultr...
My heat pump dryer came with an energy estimate for various functions and loads. The various functions which shorten the time, or the functions which increase the heat (often related) are specified to use way more energy. To me, it's pretty clear, plus the manufacturer specifies it.
> Also it's not that using lower-temperature water to convey heat is somehow more efficient. [..] If you're burning gas it doesn't really matter either way, you just get the energy out you put in.
That's what I used to assume as well. It isn't accurate though. If the water that comes back to the heating element is too hot it'll not be as efficient as when the temperate is lower. Similarly, the additional energy that's needed to heat the water to e.g. 75+ degrees Celsius is wasteful. You can save around 30% of the energy by reducing the temperature of the water that's used to heat your home (though might not work due to various considerations). There are loads of other things that are possible which also significantly reduce the energy usage.
Regarding how to save energy when using a boiler there's a huge Dutch topic about it with loads of tips: https://gathering.tweakers.net/forum/list_messages/2027810. I assume similar information can be found in other languages, though heating using gas and water is really popular in NL (more so than any other country I assume).
They might still be true though, but if you keep in mind that it takes about 5 times more energy to evaporate water than to heat it to 100C, and that heating water is more difficult than most other substances it is really not clear why using more heat would be (far) less efficient. Sure it would consume heat at a higher rate, but also less long.
That depends. For resistive electric it shouldn't make a difference, pretty much all heat is transported.
For non-condensing gas (or wood etc.), if your heater is going full blast and a lot of the heat goes up your chimney and lowering the temperature makes a smaller, slower flame, that gets absorbed better, I think you could get 10-30% difference. The heating of water itself to 20℃, 75℃ or 110℃ shouldn't make much of difference, as you're not supposed to cool the effluents too much, or you get condensation, acids, rust ... which will likely kill you equipment.
Condensing gas is cool, extracting so much heat, that water condenses, but the gas must be clean enough and the condenser resistant to corrosion. Here, lowering water temperature can safely lower the effluent gas temperature for more heat extraction (even in optimal power range), and condensation of resulting water vapor from burning gas is about 10% extra energy that would otherwise go up the chimney. I'd expect about 15-30% more heat than non-condensing, especially if run on lower temperatures.
Heat pumps are quite efficient at moving heat, where 1W of electricity can move 3W of heat for a 4W heating yield. A steeper gradient means more work, so pumping heat from 20℃ to 75℃, 1W may only move 0.5W of heat for 1.5W yield (numbers not accurate). Lowering the temperature can make a 2x difference, or even more in extreme cases.
Right, it doesn't have to, but it's also possible that more heat makes it take proportionally less time (or close enough, with negligible decrease in efficiency).
Obviously, yes, using a heat pump will use less energy than a resistive heating element. But the question is more about how much and how quickly heat is input (regardless of how it was generated) and how that affects drying times.
Some places you pay for the joules delivered into your home. You have flow meter and temperature meters on he input and the output of the radiators and the price for joule is constant regardless of input and output temperatures.
What saves you money is keeping your interior cooler because heat loss is propotional to the temaperature difference.
Unfortunately I only have a Dutch link which goes into way more detail: https://gathering.tweakers.net/forum/list_messages/2027810.
Dutch energy companies by law have to advise their customers how to save money. The app I use give exactly this advice (lower the temperature), plus various other advices.
> Some places you pay for the joules delivered into your home
That's something different than what I said, no? I'm talking about when you generate the heat in your home. I'm aware of that solution as well, they're efficient because of volume plus part of the heat (energy required) is waste-heat from some industry.
There's still various ways to save energy despite exactly measuring the temperature out and in. E.g. radiator fans.
I know this all seems entirely illogical. Energy in (or required) should stay the same. Practically though, it's probably energy losses that somehow occur and are avoided.
E.g. for the radiator fans people measured if they save energy. They do, though the cost of buying them might outweigh the savings. DIY is cheap though.
Someone is paying to heat that water, and that someone would get a bit more efficiency out of the system if the water temperatures were lower.
If you generate energy inside your isolated house and transfer it to radiators also inside your house temperature shouldn't matter.
Until near the end of the cycle your dryer is putting all the energy into evaporating water, so the temperature inside the dryer is actually fairly cool. Right at the end things change as the remaining water isn't enough to counteract all the energy being put in and so you heat the clothing to no purpose. So at the end off the cycle you should either shut off with a little moisture in the clothing, or regulate the temperature so that the heat input is balanced by the water evaporation.
What on earth is thermostat heater, you ask? Surprisingly, many dryers apparently have a simple fixed-temperature thermostat, and in order to make lower settings work, a heating element tricks that thermostat into perceiving a higher temperature.
If that heating element doesn't do its job, then the dryer acts like it's always on the highest setting.
From https://applianceassistant.com/Dryer-Repair/How-Electric-Dry... :
> The thermostat heater is often located within the cycling thermostat. However, it may sometimes be a separate component mounted to the dryer's cycling thermostat. Depending on the dryer's temperature setting, more or less voltage is supplied to this heater. Low settings supply more voltage and create more heat, while medium settings supply slightly less voltage, generating less heat. High heat settings will not energize the thermostat heater at all. In this way the thermostat is tricked into thinking that the dryer is hotter than it actually is, so it opens at a lower drum temperature.
https://www.energy.gov/eere/articles/no-heat-no-problem-ultr...
(Better not leave anything metallic in there though...)
The links to more detail with: > The goal of this project is to develop a clothes dryer prototype, using ultrasonic transducers, with an EF above 10 lb/kWh.
But also: > DOE’s Building Technologies Office is seeking new clothes dryer technologies that can increase the energy factor (EF) from 3.7 to 5.43 lb/kWh
However, a quick Google shows that the 3.7 is not a heat pump dryer, see e.g. https://www.intechopen.com/books/current-drying-processes/th.... The figure for an existing dryer should be 7.6 lb/kWh. Meaning, the solution is (currently) not good enough.
The link in the article and my link shows that the intend is to go way over 10 lb/kWh. The link I found showed it could be around 20 or even 44 lb/kWh (seems to depend on the frequency used). This while being way quicker than anything else, especially heat pump dryers.
Unfortunately doesn't work quite as well with clothing. Or perhaps I could make an analogy that lingerie is like a good knife?
[0] Stolen from somewhere online and can't be bothered to find the original source.
I'm washing t-shirts in 40 deg and drying them in my washing machine with built-in dryer.
They come out a bit damp to avoid creasing too much. I never had them smell even though I was just unloading dryer into a huge pile of damp clothes and leaving them like that for a day or two to dry out completely. I even forgot to take them out of the washing mashine and found out few days later. They were still damp but didn't smell. I washed and dried them again though to be on the safe side.
This stuff lasts forever when washed on cool/warm and then hung.
Friends of mine have complained about one brand or another not lasting very long, but they've been tossing the stuff in the drier.
We're fortunate to have a basement with a nice beam I can place hangers on (for winter drying), or a hanging bar I fitted in the garage (for summer). Lately I've been getting rid of 8-10 year old stuff that I no longer like or no longer fits, and it's sellable, as opposed to just worn out.
(Doesn't sell for much, but folks will happily pay $20 - $30 for special print cycling jerseys that are still in good shape and cost $80-130 new. Way better than tossing them in the trash.)
Always button and zip your jeans, and if you're not in a hurry, cotton clothing seems to be less worn by friction in the dryer than by the high heat. I run a lot of my cotton knits through twice on permanent press instead of once on cotton. And I don't use dryer sheets. Dryer sheets keep your clothes from getting static cling when you have over-dried them, but over-drying them damages them. The static cling is a symptom that you shouldn't ignore.
What you want to do is pull your clothes out when there is just a hint of moisture in them. The air and the latent heat should be more than enough to suck out that last hint of dampness. And if one towel or pair of pants is still damp, nothing stops you from running them by themselves for a couple minutes while you fold the rest.
UV from the sun kills bacteria, and you want that on the side near your skin, and as a bonus the inside fades (UV again) but the outside doesn't. I have some t-shirts that are quite faded on the inside but still reasonable on the outside.
I read in some credible, non-technical publication, I think the NYT or WSJ, an interview with a engineer in that field (something like detergents or washing machines) who said that detergents used to need heat to enhance the chemical reaction, but that it's no longer true and cold water works just as well.
EDIT: Does anyone know a good technical, authoritative resource on laundry? Consumer Reports has well-researched info, but not in the depth I'd like.
So a 40°C cloth can be washed at any lower temp but might deform or loose color or even breakdown if washed warmer than that.
> "Front-loaders and high-efficiency top-loaders run normal cycles 10 percent cooler than agitator washers, and the 'warm' wash temperature in the U.S. has declined by 15 degrees over the past 15 years," says Tracey Long, communications manager for P&G's fabric care products in North America. “Traditional detergent enzymes can be sluggish in cold water so we worked to create a mix of surfactants and enzymes that deliver cleaning performance in cold water across all product lines," says Long.
> Consumer Reports’ past tests found detergents have gotten much better at putting enzymes to work in removing dirt and stains at lower water temperatures, and are less effective at higher temperatures.
Source: Consumer Reports, "Don't Bother Using Hot Water to Wash Your Laundry: Consumer Reports' experts say cold water can get the job done", https://www.consumerreports.org/washing-machines/dont-bother...
If you want to sanitize anything, just use some bleach. It's harsh on fabric, but so is hot water, and the bleach will do a much better job. (FYI, I don't have any whites at all.)
> When a family member is sick, use hot water mixed with chlorine bleach to reduce bacteria in the bed linens and towels. The same goes for cleaning dirty cloth diapers, or other messes.
But also,
> Heating water accounts for about 90 percent of the energy needed to run a washer
So I only use heat for special occasions.
Article: https://www.consumerreports.org/washing-machines/dont-bother...
(This might even help deal with the continually scummy front-loader problem, but I can't speak to that as we prefer our 33-year-old Kenmore top loaders that can still actually be repaired rather than replaced with expensive new Chinese/Korean crap every few years. Mechanical timer controls and durable design and mfg FTW! For what it's worth, our total cost of purchase and repairs over 33 years is maybe $1200.00 for the washer/dryer set.)
I've bought an expensive front loading washer-dryer with water heater (upto 60C) and heat pump dryer recently. Now I always wash with at least 15C water, even 15C, it's significant difference in cold winter situation.
Symbols that you never use aren't very useful when all you really need to know is "do not dry", "do not bleach", "wash with like colors". It's really not that big of a deal to put a tag written in English and Spanish to the US, or in French to France, etc.
When artists use English, CAD designers use Traditional Chinese, and factory staff use Simplified Chinese or Vietnamese, and consumers use every language - there's a need for a standard symbol. You have a good point about dry cleaning services too!
The difficult part is that the people through this international supply chain can't type these symbols in emails, or search for them in databases. That's why a Unicode code point should be assigned.
This article looks like it has a general summary:
https://sewport.com/tips-on-starting-a-clothing-line-from-43...
This is not her company, but a job description for a similar role (you'll need to translate from Chinese):
https://www.104.com.tw/job/5cuv8?jobsource=jolist_c_relevanc...
I'm with you, it bears uncanny parallels to the PCB design workflow. Not just the Gerbers, but the component/fabric selection, simulation, design drawings, etc.
On the other hand, if the text was just in a language that I did not speak, I can either type this into a translation app myself, or use the automatic translation camera on my phone to identify them.
And sure, I can apparently now do that for those washing symbols too, which is nice... but why is that information being conveyed in a "language" that almost no-one speaks? I'd be just as confused if every item of clothing I purchased had washing instructions in Lojban.
I fully understand why an attempt at standardised symbols was made, being able to communicate that information more compactly would be useful, but it very clearly failed. They're not intuitive enough to learn without third-party resources, and a very very tiny fraction of the population is willing to put in the effort to do so. Just use text.
They are like traffic lights.
Sounds like a failure of the point of those symbols. How about using words instead? Then you don't need an app to decode them. You can use google translate if you must.
Oh and I guess just by normal kid clothes (cotton/polyester) so they don't have special instructions.
I wonder about helping manufacturers generate a QR code to use alongside the symbols to provide a detailed per-label translation?