9 ms·
Fridge 0.1
- dsr_ 8y agoMy new freezer says that in the event of a power outage, if we don't open the door food will remain frozen for 48 hours. All the walls are unusually thick, which I presume indicates a lot of insulation. Mr. Hess might want to consider adding additional insulation to the outside of his unit, especially as temperatures rise in summertime.
- emmelaich 8y agoYes, I'm pretty sure standard refrigerators have far less insulation than they could have. Probably mostly for weight and cost reasons. A good quality camping coldbox (e.g. made of fibreglass or thick polyethylene plastic) can keep ice solid for days even in an Australian summer.
- kickscondor 8y agoOn long river and fishing trips, a standard cooler can work with the help of a good shady spot and a towel that has been dipped in the river and draped over it.
- emmelaich 8y agoEvaporative coolers were popular in Australia before the widespread availability of electricity: https://en.wikipedia.org/wiki/Coolgardie_safe https://en.wikipedia.org/wiki/Coolgardie_safe
- tonyedgecombe 8y agoA smaller version is useful for storing insulin on the go: https://shop.diabetes.org.uk/collections/frio-wallets https://shop.diabetes.org.uk/collections/frio-wallets
- emmelaich 8y agoI don't think they're evaporative. Plus you need to recharge? Also, "patented crystal technology" what?!
- tonyedgecombe 8y agoThey are, you soak them before use to 'recharge'.
- kickscondor 8y agoOh I appreciate you chiming in! I had no idea these existed.
- JonathonW 8y agoTemperatures seem more than a bit high to me-- FDA recommendations [1] are that fridge temperatures should remain below 40°F (~4.5°C) for food safety (to inhibit bacterial growth). This fridge is never making it below 5°C, and (from the real-time data linked in the post) it's peaking uncomfortably close to room temperature-- I see one spike all the way up to 16.5°C, and it doesn't look like it recovers quickly at all. [1] https://www.fda.gov/Food/ResourcesForYou/Consumers/ucm253954.htm https://www.fda.gov/Food/ResourcesForYou/Consumers/ucm253954...
- angrow 8y agoFTA: > (Numbers in this graph are running higher than the actual temps of food in the fridge, for reasons explained in the scuttlebutt thread.)
- sdrothrock 8y agoAnother resource in this kind of measurement would be the mean kinetic temperature -- often it's not entirely useful knowing that the fridge is 15 C or whatever after you open the door and get something; you really want to have a reasonable measurement of how much the temperature of the contents changed in that time and in the time until the fridge interior returns to the set temperature average.
- shakna 8y agoIt's generally sitting around 0.5-1C. The relevant part from scuttlebutt: @IBob on temp probe placement, I think I know why it was seeing such sharp swings when outside the water. I had the wire coming down along the inner fridge wall corner, touching it for a foot, and then the probe was pulled out an inch from the corner. So, it was both very close to the walls, and wire's contact would suck more heat away when the wall cooled down. The spring thermometer I have mounted in there to measure the air temp now avoids this problem, and has been staying just above freezing during long compressor runs despite frost buildup on the walls
- jjeaff 8y agoSo make sure your food doesn't touch the walls of the fridge or it will spoil. Got it.
- deleted 8y ago[deleted]
- dkuebric 8y agoCool project. He's loaded the fridge with some ballast (17 gallons of water), so while there isn't an electric battery, there is a reserve of another kind.
- eric-hu 8y agoIn cooking, I like to think of large thermal masses as a thermal battery. Thus, a cast iron pan is good for searing steaks than typical pans because it's a beefier battery.
- dTal 8y agoA capacitor is an even better analogy - "charge" is asymptotic, and the function of the cast iron (and the water in the fridge) is to smooth out local fluctuations in heat (rather than to store it long term).
- eric-hu 8y agoInteresting observation. Is the line between capacitor and battery a matter of intended storage duration?
- deleted 8y ago[deleted]
- daveguy 8y agoHey Joey, fan of your projects. I'm not sure if the fridge you have pulls a vacuum when it is closed, but pulling a vacuum can make a fridge much more efficient. I worked with some of the engineers that designed this -80C freezer for the International Space Station (where power is at a premium): https://en.wikipedia.org/wiki/GLACIER_(General_Laboratory_Ac.. https://en.wikipedia.org/wiki/GLACIER_(General_Laboratory_Ac.... One of the key efficiency factors was being able to pull and hold a vacuum. And obviously the more efficient the engine that pulls the vacuum the better. If it's a modern high efficiency unit, it probably already pulls a vacuum. If not, it may be worth physically hacking.
- moopling 8y agoThe link is broken, I think it was renamed https://en.m.wikipedia.org/wiki/GLACIER_(refrigerator) https://en.m.wikipedia.org/wiki/GLACIER_(refrigerator)
- jwilk 8y agoNon-mobile link: https://en.wikipedia.org/wiki/GLACIER_(refrigerator) https://en.wikipedia.org/wiki/GLACIER_(refrigerator)
- glass_of_water 8y agoWith the vacuum technique, I imagine you would have to think more carefully about the containers you use (e.g. lids would probably pop off tupperware-style containers).
- buckminster 8y agoAnd unwrapped fruit or veg would dry out really quickly. I wouldn't want this in my regular fridge.
- steamer25 8y agoTheoretically, I'd think you could just wrap most of the central compartment(s) with a (permanent/sealed/static) vacuum chamber--like a big thermos. http://www.greenbuildingadvisor.com/blogs/dept/energy-solutions/does-vacuum-insulation-make-sense http://www.greenbuildingadvisor.com/blogs/dept/energy-soluti...
- slacka 8y agoSome serious over engineering going on here. The fridge should be set to the coldest possible temperature without the food freezing, as close to 1 °C as possible an run whenever there is solar power available. The only software need I see would be a warning if the internal temperature got too warm. Instead of smarter software, the focus should be on insulation and adding mass to hold the heat. For example, I put a foam insulating board over my 22 cu. Chest Freezer to improve it's efficiency.
- jncraton 8y agoYou aren't wrong, but there is some value in a more complex control system. For example, the fridge uses some sort of hysteresis to prevent the compressor from cycling on and off too quickly. Let's say it runs for 15 minutes every hour. You ideally want it to schedule that last 15 minute run at the latest time possible when enough sunlight is still available to run it. This shortens the amount of time that the fridge needs to be able to stay cold without power.
- joeyh 8y agoI've thought about trying to add that eventually, but I think I would need a weather forcast with insolation data and also some modeling of when the sun goes behind trees/hills at different times of the year. Anyone know a good insolation forecast API?
- floatrock 8y agoNever used it, but I've heard good things about the darksky API: https://darksky.net/dev https://darksky.net/dev
- pvg 8y agoAn even further radical simplification would be just plugging the fridge into an outlet. But that seems like it would be missing the point a bit.
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- MisterOctober 8y agothis has much merit
- deleted 8y ago[deleted]
- seltzered_ 8y ago“the fridge itself becomes the battery -- a cold battery.” Wildly my first thought from from this is that you theoretically could use a peltier in reverse to generate energy. It wouldn’t be efficient but possible. At a different level, you can also think about your interactions with the fridge. You could segment the fridge such that it had different insulated sections that you use.
- kpil 8y agoI have three old solar panels in my boat for a total of 105 W, and 2 cheap 85Ah marine deep cycle 12 V batteries. It copes with keeping a number of phones, radios, tablets and a small laptop charged, some moderate use of lights, an occasional run of a webasto diesel air heater, and continously powering a compressor driven fridge box. I think the batteries are one of the cheapest thing in my system.
- joeyh 8y agoBatteries are one of the most expensive parts of an offgrid PV system once you start looking at prices over decades. My 1.5kw solar panels and electronics cost $2k (self-installed) and will last 20+ years. To run the fridge on demand from batteries during the night and rainy days, I'd need something approaching the capacity of a powerwall, $6.6k every 10 years.
- jabl 8y agoOn a larger scale something like this has been proposed (or maybe even already implemented somewhere?) as an economical way to deal with variable renewable energy (wind, solar); when VRE is plentiful and cheap, giant industrial refrigerated warehouses cool down a few degrees, and conversely when VRE is scarce and expensive, let it heat up a few degrees.
- floatrock 8y agohttp://www.axiomexergy.com http://www.axiomexergy.com -- they build "ice-batteries" where they create ice at night when it's cool and electricity is off-peak, then use that ice to cool industrial refrigerators (supermarkets, cold storage facilities, etc) during the day.
- quickthrower2 8y agoAnother hack is to not store things in the fridge that don't need to be. Bread, eggs, etc. Maybe curdle the milk! That looks like a big fridge, maybe then it can be smaller. Although smaller doesn't necessarily mean more efficient you may want to check the star energy rating.
- joeframbach 8y agoHe has made the fridge "smaller" by putting 17 gallons of water in it (per the scuttlebot link). This is even better than a smaller fridge, because the cold water itself keeps the fridge cool when it is off.
- quickthrower2 8y agoThanks, that's interesting. I like to read the article before commenting, but I don't usually go a level deeper!
- memco 8y agoHow are the graphs being done? I'd like to look at using them for a project.
- PascalW 8y agohttp://javascriptrrd.sourceforge.net/ http://javascriptrrd.sourceforge.net/
- tzahola 8y agoWhy don’t you use a supercapacitor bank instead of the powerwall?
- n1000 8y agoNice project. Dependig on the location a ground fridge could be an alternative. Soil temperature is close to the annual mean in a few meters depth. https://www.builditsolar.com/Projects/Cooling/EarthTemperatures.htm https://www.builditsolar.com/Projects/Cooling/EarthTemperatu...
- Gravityloss 8y agoThere is a massive amount of inefficiencies in our power usage. Resistor based water heaters and space heaters, heat pump / compressor based air conditioners and water and space heaters, fridge and freezer cooling compressors, work air compressors etc all could be used to increase grid stability instead of now decreasing it. Or, if you have your own generation or are off grid, to reduce the electricity trading or storage needs
- deleted 8y ago[deleted]
- Keloo 8y agoMy parents live in a village, they have basement, few meters underground (under the house) the average temperature is 0-5C (even in the summer when outdoor temp is 30C). All the food is saved there for years! Engineering sometimes is so wrong, people before tech had a lot of simple an nice hacks!
- BrentOzar 8y agoSomewhere, a team of coders at a top government agency is furiously designing Stuxnet 2.0 to break his fridge, bring him back to the grid life, and raise the nation's GDP again.
- JasonFruit 8y agoFor my diabetic mother in a disaster, I would pay a few grand for something like this that is reliable — it could even be tiny!
- tonyedgecombe 8y agohttps://shop.diabetes.org.uk/collections/frio-wallets https://shop.diabetes.org.uk/collections/frio-wallets
- JasonFruit 8y agoThat's pretty fascinating, and might be something I can work with. Thanks!
- dingdingdang 8y agoWhat is potentially most interesting with this project is that the thermal mass allows a 14 hr down-cycle - could a regular-on-grid fridge be run like this, or close to it, with economic benefit in terms of electricity use? Or would this simply just cause spikes in electricity usage to compensate for the down-cycle along with increased mechanical wear?!
- wongarsu 8y agoAny economic benefits would likely come from using cheaper off-peak electricity. Once smart meters and flexible power prices become more common I would expect fridges (and other appliances) with such features to become more common.
- gregimba 8y ago12 volt fridges used for car camping might be much more efficient than a regular fridge if you rely on solar power.
- e12e 8y agoFrom the scuttlebutt thread (on mixing water and glycerol in order to target a freezing point close to 5C or so): > Glycerol sadly has the tendency to supercool,so once all of your solution melts you will lose all of your seed crystals and then you have to drop down to a really low temperature before it will get back to a solid. Add sand to the water tanks?
- gumby 8y agoInstead of an electrical fridge, use the solar heat directly to boil the refrigerant, as with a gas-powered fridge (once common, now rare due to widespread electrification). The power loss of solar->PV->motor compressor is quite large while a gas refrigerator has no moving parts: https://home.howstuffworks.com/refrigerator5.htm https://home.howstuffworks.com/refrigerator5.htm