220W from an old 240W panel is pretty good! No one should doubt the output of old solar panels. 4 x 240W panels produced a max of 1050W for me, and they were 14 years old.
Sand makes sense when you go very hot like 250C that means the wooden frame will burn since water holds heat relatively well that means te same volume that is needed to hold heat at 250C is the same as watter at 95C just below boiling when going to 250C-800C then you need sand. When we talk about stove to be like 3 ton and it has average temperature delta 40-60C degrees above room temperature and it gives you heat for a day but when you pump delta 10x like 500C degrees up you stored for 10 days make sand battery 30ton and you cover house for 100 days in US. Here in Estonia winters are longer and no sun in december so that even inverter take more energy than i get from sun. So we store 100 days we use stone wool since glass is liquidid some degree even at room temperatures avoid that 3 feet (1m) is quite enough that hold heat for 100days. Also I have idea to run steam turbine some day on that heat to generate electicity also you get like 50c(150F) water out of steam turbine and thatt is perfect for floor heating but probably you will use like 20-50% waste heat to heat floors and what you need more is done by heat pump. In here we need 75% heat and 25% electricity and you can regulate your generation what goes to short term battery and how much heat you need when winter is not so cold then you cant sun steam whole day but then you have more sun also
I’ve been following the sand battery idea and yours is a great experiment. We need to try a 4” x 4” box of sand mass and see how long it will hold the heat. Your wire you were using could have been Nichromium wire. It is used for the same purpose idea and is readily available. I’m looking at a galvanized grain storage bin for my sand storage container. Keep up on the science of heat storage you’re going in the right direction.
I believe the wire I used was Constantan Wire, used for a thermocouple. It has resistance, but not like nichrome wire. Stainless steel wire would work too. Just have to test the resistance for maximum load from solar panel. You can get a pound of that wire from Harbor Freight for about $9
Think off-grid Earthship heating conduction. Heat rises, which cause a void to be filled by sucking cooler air through long undergound cooling conduits. One wall Sand Battery located in the greenhouse. It can also heat your Hottub. Set on oposite ends of the Earthship to channel the air through the whole home using 100% heat convection which never fails.
Heat does not rise. Hot AIR rises. Heat moves in the direction of denser mass. This is why putting heating wires over a concrete floor, covered by a rug, performs so poorly in heating the room air. The heat is absorbed by the very dense concrete and then down into the ground beneath the concrete. Some of that heat will eventually heat the air, but it is extremely inefficient. This is why concrete floors should be covered with insulation or an air space before installing the wires.
I really like your test rig. I'm interested in scaling that up to a shed sized sand pit. A big kiln filled with sand. Heat it in the summer, draw heat off in the winter to heat the house.
Been there. Done that 😉 I've got an 800 gallon insulated ex fuel tank buried in the back yard here in Saskatchewan. Its got an air plenum in it that circulates the air through the mass. Ive got a 8000w 30Amp construction heater that kicks in every time my solar batteries are full all year long. Heat stratifies in sand just like it will in water. It congregates at the top. The top of my tank right now is 582C. The hydronic heating has already been on for 3 week in the house. There is already snow on the ground here. Last February before the days got longer and my solar was able to start producing more energy that I was pulling out of the tank? It was just under 200C. I have more than enough solar to fill my batteries in a couple hours even in the crappiest conditions. Its amazing what you can do when you cut the greedy installers out of the loop. And pretty easy to justify it when its replacing a $3000 heating bill each year.
@@gregwalker3540 aircrete would make great insulation around the outside to prevent the heat from escaping. Such as a hot fluid loop being pumped to a different location
Great video. TY I can see scaling this up and having a massive heatsink and solar array outside and using heat exchangers to move it inside when needed. A liquid would be even better than fine sand but Im not sure if there is any cheap or environmental friendly alts to water that can get that hot without turning into a gas. Maybe even use water if you have enough of it and a relay hooked to a thermostat to cut the power to it before it boils.
You wouldn't insulate a wood stove, so how did you come to the conclusion of insulating a sand battery? Use or make a metal box,,,right? For the purpose of storing/harvesting heat you want more mass rather than insulation--save that for the structure being heated.
Some heat tubes would spread heat evenly across layers, so you could concentrate heating as nicron wire is not cheap. You can make them cheaply using different materials although copper is very good and soldering ends is easy.
What temperature did the surface rise to? Any idea how quickly it cooled down. Can you imagine you heating your home at night, with a big one of these heated during the day? (Even better, heated during the summer, six months ago.) Sorry. Thank you. Really informative.
Very nice! I'm wondering what the "correct way" of heating this is. Given that the sand seems to be a good insulator, putting as much heat as you dare in the middle rather than spreading the wire out evenly would make the heat spread out over the course of the heating/day, causing less losses & less need for additional insulation. Likewise, if you build some kind of tubing to pump out the heat, those being more at the edges might also pull out the heat less aggressively?
I was using a sand and clay mixture so that it would conduct heat better. There are many different ways to direct the heat. I think it would depend on size and application. Tubing for radiant heating is a good possibility.
Resistive heating wire is usually nichrome, but sometimes tungsten. If you focus the sun with e.g. a space blanket reflector directly onto the dirt, you'll get much higher efficiencies across a much broader spectrum without the cost of a solar panel. Admittedly, your approach does have the advantage of allowing all sides of the box to be insulated without a heat exchanger. You're going to need plumbing anyway though if you want to use that energy to heat water or air, so a heat exchanger isn't out of the question. Not sure what you mean to do with the heat, but hopefully you're not planning this as a viable electrical battery. If you mean to turn it back into electricity, your end to end efficiency is pretty much guaranteed to be in the 1-5% range when you consider both the solar panel and the peltier cells or thermopiles or heat engine + generator or whatever. Resistive heating is highly efficient though, so at least you don't have to worry about that part. For the cost of one solar panel you could have hundreds of square feet of mylar reflecting sun on a very large pile of dirt or patch of dead ground (not organic-rich soil which is combustible and a frequent cause of camp fires causing forest fires and probable source of the smoke you observed). Bury some pipes/ducts/radiators in the dirt for air/water. It'll have its own logistical challenges, but it's so cheap for the size it's hard to imagine it not working to some useful extent. Anyway, hope you don't mind me rambling with my thoughts. Thanks for sharing the inspiration!
Using photovoltaics may not be an efficient way to generate heat, but it sure does simplify a lot of things. With the low price of PV these days, it's totally worth it. I use PV for all my hot water so there's no plumbing/pumping/leaking/possible heat exchangers, etc. involved. Very low maintenance, no moving parts, and the location of the collector isn't tied to where the energy is stored.
@@fxm5715 I do completely agree with the simplicity point. But you must not use hot water much, or have a different idea of "low price". Average hot water power consumption in the US is 10-15 kWh/day. Unless you buy in substantial quantity, PV price is sitting in the $1/watt neighborhood. Keeping in mind that in most of the US there is an average of 4 hours of full irradiance per day, 10 kWh / 4 hours = 2.5 kW/hr, or $2500 worth of solar panels if that's all your hot water. A space blanket costs around $1 for (more than) the same area of sun capture as a $100 PV panel, while being somewhere around 3-4ish times as efficient. We're talking about $5-$10 worth of space blankets to compete against your $2500. Even if you got a great bulk deal by buying a large 5-figure system plus government subsidies so it only cost you $1000 for the panels we're talking about here just for your water, I'd still consider the fact that for the $1000 spent on panels just to not have water flowing through a little extra pipe it could have been generating enough power for multiple entire households, and enough if you so chose to focus it right, to melt metal and turn sand into glass. The pipe, btw, probably costs around the same as the extra cable you had to run to get 2.5 kW from your panels to your water. If you didn't notice, I've been rounding everything against myself here. I'm not saying PV is overall a bad thing. If it's what you use for all your power anyway, by all means find every way you can to make use of it. But I still find it difficult to watch someone making heat with a solar panel's output without thinking about how you could get the same amount of heat production in less space and time for 1% of the cost, with only some aluminized plastic instead of an exotic sandwich of semiconductors and current collectors. Anyway, the whole point of a sand battery is that it's cheap. It's nowhere near as convenient or compact, but it drops the cost of storage to, well, dirt. Seems odd to pair that with the most expensive renewable which *already comes in as heat*. It'd make a lot more sense if the power source was wind or hydro or something. So ultimately I agree that PV panels are more convenient than space blankets. But I do not agree that they're "worth it" for the use case of heating. With regards to reliability, I think there are points on both sides.
@@user-hf3ym7lh4d Yes, I live alone, and only have to account for one shower and washing dishes on a daily basis. My total energy consumption is less than 14 kWh/day, and that includes high demand summer AC use. Laundry is washed cold. I've got only 600 watts of PV specifically dedicated to heating water, but that's more than enough to keep up with usage, on average. I can go three days without using up my hot water tank. The tank automatically switches to municipal current if the temperature at the top of the tank drops below a certain point. That usually only happens in the winter months when there's less light in general.
We have 1,920 watts of PV grid-tie. That more than takes care of our 'annual' electric hot water needs for 2 people. For 3 months in the winter the power output is pretty low. Be nice to think up of a durable, inexpensive, way to charge something up with high temp heat over the whole summer, and make use of it through the winter.
@@doubleMinnovations That's a really tall order. A lot of power to store for a long duration. I feel your winter solar pain though, I'm up in Maine. The usual answer at home scale is batteries obviously, but not cheap unless you want to build them yourself. You'd have to get into the layers and rolls constructions I was talking about in the comments on those videos, though. Not just a single rod or pipe, you'll never get the density you need that way. Even then, most rechargeable chemistries don't do very well holding the same charge for months, even professionally designed and produced. They tend to either self-discharge or break down. The usual answer at utility scale is pumped hydro where they pump the water uphill to charge it and drain it back down through a turbine to discharge. It'd be a cool use for your past turbine work, but it's only cheap at huge scales, unless you happen to already have a giant pond on top of a more giant hill in an area that doesn't freeze much. You could try the same thing with logs or something tied to a rope connected to a winch, but the parts of your property seen in the videos are pretty flat, you'd still need a big (and steep) hill or extremely deep hole. And a ton of otherwise unused space. I did the math once on covering our entire roof with water capture, I think somewhere around 40 by 60 feet if I recall. Turns out the house would collapse before we stored enough to power everything for a single day. So we're talking pretty massive size and weight for months of energy. At *least* a large farm scale irrigation tower, and likely several of them. And they have to keep themselves heated enough to not freeze. The thermal battery thing is theoretically very cheap, and already being commercialized in Europe. But I think you'd need to do a very good job on the insulation of a very large battery. They do self-discharge obviously, so you'd need to scale up a lot. A smaller thermal battery self-discharges faster because of the surface area to volume ratio. As you scale up, the surface area scales as a square, but the volume scales as a cube. So a larger thermal battery can store more heat relative to the amount it dissipates through insulative losses. Again, the scale of what you're wanting to do just translates into equally massive solutions that raise more practical problems. I'm not sure that any of them will scale the way you're hoping for, but there are other unconventional options that make for fun experiments. Like fuel production. Use the excess power to gassify or pyrolize biomass or waste plastic or whatever into methanol or biogas or whatnot. I'll give a nod here to hydrogen, because you can't hardly have an energy conversation these days without it. I've heard of spare PV output being used to electrolyze hydrogen out of water, but I haven't heard of it being done at home scale. Storing it and using it safely requires some detailed knowledge. Without proper design and particularly material selection to avoid steel embrittlement and suppress static buildup, your hydrogen tank becomes a vehicle-sized fragmenting pipe bomb that can go off because of an invisibly small spark from a dusty breeze on a dry day, even if it's been working fine for months. Also, because an oxyhydrogen flamefront can exceed mach 30, it's rather difficult to burn in a controlled way without flashing back through the supply line and blowing the tank if you don't have absolutely *all* oxygen purged from the system. Hydrogen can be fun but make sure you know what you're doing before you scale that up. Burned all my forearm hair off playing with that stuff one 4th of July, and that was just a little partially inflated produce bag at atmospheric pressure. OTOH, circling back to where I started, you could drop a few dozen to a hundred or two dollars on Amazon for some space blankets (or maybe they have mylar in bulk rolls) and have usable amounts of thermal power even in the seasons when the sun isn't very high. This is one of those situations where generating more power is cheaper and easier than trying to store it, especially if we're talking about thermal. Then your problem collapses down to storing enough energy for a few stormy days at a time instead of months, so the thermal battery would probably totally work for cheap even without huge fancy vacuum insulated storage tank arrangements. I'm planning on testing my proposed setup, I'll let you know how it goes. We still have another foot of snow in the forecast, but this has been on my mind for a few years, and I finally have the space to try it out now. So some time this year. It'll either be "I told you so" or "I burned my heavily forested property down with space blankets." :) Tangentially, do you have any wind on that giant open flat property of yours? I was thinking about what a massive amount of wind energy you could capture for cheap with a large tarp or two fastened to a light frame on a rope between two trees for support, spinning on a vertical axis tied to the rope, or using the rope itself as a horizontal axis. Have an old broken winch I was going to use as the generator. It's another tree you could try barking up for ultra cheap power, orders of magnitude larger and cheaper than usual home wind turbines. It'd capture so much while being so light, that you'd have to design some flexibility into the structure just so it doesn't snap in a storm. Anyway, not sure if anybody is going to read all that, but I appreciate your videos. I find them a useful catalyst and reminder for my own ideas. Plus you're just about the only one out of my 3 digits of channel subscriptions who engages in the comments with any regularity. So, thank you for your time. I hope something I wrote here was useful enough to be worth the reading the small novel I apparently just wrote.
Sand is cheap. Concrete would also break apart if heated too much. I put a heat storage furnace in for my (now late) sister 20 years ago. It used off-peak electric to heat up clay bricks; and that worked good.
I tried a couple of experiments with a fresnel lens for heating a container of sand. It works if you have a way to keep the lens tracking the sun. -kind of difficult I thought.
Hello sir. Sorry for commenting here but I need desperate help from you :( I have a project to make about nitinol and I just saw your videos (which are awsome and I want to congratulate you for doing them). I will let the videos down below but I want to know this: how can you set a speed to a nitinol engine which is using hot water as source of energy? I mean how can you control how slow or speed is it rotating? In your videos, I saw that you have some kind of "pipe"/lever that goes through the engine and it controls the speed...how is that working? Thank you and sorry for bothering you :( The videos: ruclips.net/video/Zgf6iYHE1bE/видео.html ruclips.net/video/DJr5Ibwn6ls/видео.html ruclips.net/video/jpPVvD5SeY0/видео.html
All the lengths of nitinol wire are connected to an off-set cam wheel. The lever you see me using, controls the position of the cam wheel, which directs when the tightening of the nitinol happens as it enters the hot water.
@@doubleMinnovations First of all, I thank you so much for responding sir! Second, can I send you a private message on a social platform? (Mail, Facebook, Discord, Instagram, etc)
I consider the comment section a social platform. Many people like to read and respond to other comments. If you have a question, you can ask in these sections, then all can see. But place them under the video it pertains to. There is an email address on the channels homepage, but I don't give out personal information.
This is a dirt cheap way to store a lot of energy, for all 24/7 use. For space heating, water heating, for steam production if you have a steam electric power plant.
In cold areas the vast majority of our energy usage is used directly for heating. So if you could store a tremendous amount of heat in a mass of sand and use it somehow, i.e. flowing water or air through the mass. You have a very efficient way of storing heat. People often think of electricity storage when they hear the word "battery". But this is specifically to store thermal energy, and if used properly can be very efficient.
I just pulled out a bunch of the wire, and connected the positive of the solar panel to one end; with the solar panel in full sun. I connected one lead of the amp meter to the negative of the solar panel, the other lead of the amp meter I moved along the resistance wire until I got the rated amp load stated on the solar panel, and cut the wire there. -Trial and error.
220W from an old 240W panel is pretty good! No one should doubt the output of old solar panels. 4 x 240W panels produced a max of 1050W for me, and they were 14 years old.
Sand makes sense when you go very hot like 250C that means the wooden frame will burn since water holds heat relatively well that means te same volume that is needed to hold heat at 250C is the same as watter at 95C just below boiling when going to 250C-800C then you need sand. When we talk about stove to be like 3 ton and it has average temperature delta 40-60C degrees above room temperature and it gives you heat for a day but when you pump delta 10x like 500C degrees up you stored for 10 days make sand battery 30ton and you cover house for 100 days in US. Here in Estonia winters are longer and no sun in december so that even inverter take more energy than i get from sun. So we store 100 days we use stone wool since glass is liquidid some degree even at room temperatures avoid that 3 feet (1m) is quite enough that hold heat for 100days. Also I have idea to run steam turbine some day on that heat to generate electicity also you get like 50c(150F) water out of steam turbine and thatt is perfect for floor heating but probably you will use like 20-50% waste heat to heat floors and what you need more is done by heat pump. In here we need 75% heat and 25% electricity and you can regulate your generation what goes to short term battery and how much heat you need when winter is not so cold then you cant sun steam whole day but then you have more sun also
Thanks for commenting! Cogeneration can always be a good plan I think. Steam for turbine into electrical energy, and waste heat for heating.
I’ve been following the sand battery idea and yours is a great experiment. We need to try a 4” x 4” box of sand mass and see how long it will hold the heat. Your wire you were using could have been Nichromium wire. It is used for the same purpose idea and is readily available. I’m looking at a galvanized grain storage bin for my sand storage container. Keep up on the science of heat storage you’re going in the right direction.
I believe the wire I used was Constantan Wire, used for a thermocouple. It has resistance, but not like nichrome wire. Stainless steel wire would work too. Just have to test the resistance for maximum load from solar panel. You can get a pound of that wire from Harbor Freight for about $9
Think off-grid Earthship heating conduction. Heat rises, which cause a void to be filled by sucking cooler air through long undergound cooling conduits. One wall Sand Battery located in the greenhouse. It can also heat your Hottub. Set on oposite ends of the Earthship to channel the air through the whole home using 100% heat convection which never fails.
Heat does not rise. Hot AIR rises. Heat moves in the direction of denser mass. This is why putting heating wires over a concrete floor, covered by a rug, performs so poorly in heating the room air. The heat is absorbed by the very dense concrete and then down into the ground beneath the concrete. Some of that heat will eventually heat the air, but it is extremely inefficient. This is why concrete floors should be covered with insulation or an air space before installing the wires.
I really like your test rig. I'm interested in scaling that up to a shed sized sand pit. A big kiln filled with sand. Heat it in the summer, draw heat off in the winter to heat the house.
Sounds great!
Been there. Done that 😉 I've got an 800 gallon insulated ex fuel tank buried in the back yard here in Saskatchewan. Its got an air plenum in it that circulates the air through the mass. Ive got a 8000w 30Amp construction heater that kicks in every time my solar batteries are full all year long. Heat stratifies in sand just like it will in water. It congregates at the top. The top of my tank right now is 582C. The hydronic heating has already been on for 3 week in the house. There is already snow on the ground here. Last February before the days got longer and my solar was able to start producing more energy that I was pulling out of the tank? It was just under 200C. I have more than enough solar to fill my batteries in a couple hours even in the crappiest conditions. Its amazing what you can do when you cut the greedy installers out of the loop. And pretty easy to justify it when its replacing a $3000 heating bill each year.
So you heat your house from the sandpit all winter?
Is it a matter of circulating water in copper pipes at the top of the sandpit?
Did you check how long it took the sand to cool back to 27 degrees?
Awesome video - thank you! Use AIRCRETE TO CREATE A LIGHTWEIGHT INSULATED BOX THAT CAN HEAT TO OVER 2000 F
@@gregwalker3540 aircrete would make great insulation around the outside to prevent the heat from escaping. Such as a hot fluid loop being pumped to a different location
Great video. TY
I can see scaling this up and having a massive heatsink and solar array outside and using heat exchangers to move it inside when needed. A liquid would be even better than fine sand but Im not sure if there is any cheap or environmental friendly alts to water that can get that hot without turning into a gas. Maybe even use water if you have enough of it and a relay hooked to a thermostat to cut the power to it before it boils.
You wouldn't insulate a wood stove, so how did you come to the conclusion of insulating a sand battery? Use or make a metal box,,,right? For the purpose of storing/harvesting heat you want more mass rather than insulation--save that for the structure being heated.
Some heat tubes would spread heat evenly across layers, so you could concentrate heating as nicron wire is not cheap. You can make them cheaply using different materials although copper is very good and soldering ends is easy.
What temperature did the surface rise to? Any idea how quickly it cooled down. Can you imagine you heating your home at night, with a big one of these heated during the day? (Even better, heated during the summer, six months ago.) Sorry. Thank you. Really informative.
Very nice! I'm wondering what the "correct way" of heating this is. Given that the sand seems to be a good insulator, putting as much heat as you dare in the middle rather than spreading the wire out evenly would make the heat spread out over the course of the heating/day, causing less losses & less need for additional insulation. Likewise, if you build some kind of tubing to pump out the heat, those being more at the edges might also pull out the heat less aggressively?
I was using a sand and clay mixture so that it would conduct heat better. There are many different ways to direct the heat. I think it would depend on size and application. Tubing for radiant heating is a good possibility.
Probably Nickel-chrome. Stuff that you find in toasters.
Resistive heating wire is usually nichrome, but sometimes tungsten.
If you focus the sun with e.g. a space blanket reflector directly onto the dirt, you'll get much higher efficiencies across a much broader spectrum without the cost of a solar panel. Admittedly, your approach does have the advantage of allowing all sides of the box to be insulated without a heat exchanger. You're going to need plumbing anyway though if you want to use that energy to heat water or air, so a heat exchanger isn't out of the question.
Not sure what you mean to do with the heat, but hopefully you're not planning this as a viable electrical battery. If you mean to turn it back into electricity, your end to end efficiency is pretty much guaranteed to be in the 1-5% range when you consider both the solar panel and the peltier cells or thermopiles or heat engine + generator or whatever. Resistive heating is highly efficient though, so at least you don't have to worry about that part.
For the cost of one solar panel you could have hundreds of square feet of mylar reflecting sun on a very large pile of dirt or patch of dead ground (not organic-rich soil which is combustible and a frequent cause of camp fires causing forest fires and probable source of the smoke you observed). Bury some pipes/ducts/radiators in the dirt for air/water. It'll have its own logistical challenges, but it's so cheap for the size it's hard to imagine it not working to some useful extent.
Anyway, hope you don't mind me rambling with my thoughts. Thanks for sharing the inspiration!
Using photovoltaics may not be an efficient way to generate heat, but it sure does simplify a lot of things. With the low price of PV these days, it's totally worth it. I use PV for all my hot water so there's no plumbing/pumping/leaking/possible heat exchangers, etc. involved. Very low maintenance, no moving parts, and the location of the collector isn't tied to where the energy is stored.
@@fxm5715 I do completely agree with the simplicity point. But you must not use hot water much, or have a different idea of "low price". Average hot water power consumption in the US is 10-15 kWh/day. Unless you buy in substantial quantity, PV price is sitting in the $1/watt neighborhood. Keeping in mind that in most of the US there is an average of 4 hours of full irradiance per day, 10 kWh / 4 hours = 2.5 kW/hr, or $2500 worth of solar panels if that's all your hot water. A space blanket costs around $1 for (more than) the same area of sun capture as a $100 PV panel, while being somewhere around 3-4ish times as efficient. We're talking about $5-$10 worth of space blankets to compete against your $2500. Even if you got a great bulk deal by buying a large 5-figure system plus government subsidies so it only cost you $1000 for the panels we're talking about here just for your water, I'd still consider the fact that for the $1000 spent on panels just to not have water flowing through a little extra pipe it could have been generating enough power for multiple entire households, and enough if you so chose to focus it right, to melt metal and turn sand into glass. The pipe, btw, probably costs around the same as the extra cable you had to run to get 2.5 kW from your panels to your water.
If you didn't notice, I've been rounding everything against myself here. I'm not saying PV is overall a bad thing. If it's what you use for all your power anyway, by all means find every way you can to make use of it. But I still find it difficult to watch someone making heat with a solar panel's output without thinking about how you could get the same amount of heat production in less space and time for 1% of the cost, with only some aluminized plastic instead of an exotic sandwich of semiconductors and current collectors.
Anyway, the whole point of a sand battery is that it's cheap. It's nowhere near as convenient or compact, but it drops the cost of storage to, well, dirt. Seems odd to pair that with the most expensive renewable which *already comes in as heat*. It'd make a lot more sense if the power source was wind or hydro or something. So ultimately I agree that PV panels are more convenient than space blankets. But I do not agree that they're "worth it" for the use case of heating. With regards to reliability, I think there are points on both sides.
@@user-hf3ym7lh4d Yes, I live alone, and only have to account for one shower and washing dishes on a daily basis. My total energy consumption is less than 14 kWh/day, and that includes high demand summer AC use. Laundry is washed cold. I've got only 600 watts of PV specifically dedicated to heating water, but that's more than enough to keep up with usage, on average. I can go three days without using up my hot water tank. The tank automatically switches to municipal current if the temperature at the top of the tank drops below a certain point. That usually only happens in the winter months when there's less light in general.
We have 1,920 watts of PV grid-tie. That more than takes care of our 'annual' electric hot water needs for 2 people. For 3 months in the winter the power output is pretty low. Be nice to think up of a durable, inexpensive, way to charge something up with high temp heat over the whole summer, and make use of it through the winter.
@@doubleMinnovations That's a really tall order. A lot of power to store for a long duration. I feel your winter solar pain though, I'm up in Maine.
The usual answer at home scale is batteries obviously, but not cheap unless you want to build them yourself. You'd have to get into the layers and rolls constructions I was talking about in the comments on those videos, though. Not just a single rod or pipe, you'll never get the density you need that way. Even then, most rechargeable chemistries don't do very well holding the same charge for months, even professionally designed and produced. They tend to either self-discharge or break down.
The usual answer at utility scale is pumped hydro where they pump the water uphill to charge it and drain it back down through a turbine to discharge. It'd be a cool use for your past turbine work, but it's only cheap at huge scales, unless you happen to already have a giant pond on top of a more giant hill in an area that doesn't freeze much. You could try the same thing with logs or something tied to a rope connected to a winch, but the parts of your property seen in the videos are pretty flat, you'd still need a big (and steep) hill or extremely deep hole. And a ton of otherwise unused space. I did the math once on covering our entire roof with water capture, I think somewhere around 40 by 60 feet if I recall. Turns out the house would collapse before we stored enough to power everything for a single day. So we're talking pretty massive size and weight for months of energy. At *least* a large farm scale irrigation tower, and likely several of them. And they have to keep themselves heated enough to not freeze.
The thermal battery thing is theoretically very cheap, and already being commercialized in Europe. But I think you'd need to do a very good job on the insulation of a very large battery. They do self-discharge obviously, so you'd need to scale up a lot. A smaller thermal battery self-discharges faster because of the surface area to volume ratio. As you scale up, the surface area scales as a square, but the volume scales as a cube. So a larger thermal battery can store more heat relative to the amount it dissipates through insulative losses. Again, the scale of what you're wanting to do just translates into equally massive solutions that raise more practical problems.
I'm not sure that any of them will scale the way you're hoping for, but there are other unconventional options that make for fun experiments. Like fuel production. Use the excess power to gassify or pyrolize biomass or waste plastic or whatever into methanol or biogas or whatnot.
I'll give a nod here to hydrogen, because you can't hardly have an energy conversation these days without it. I've heard of spare PV output being used to electrolyze hydrogen out of water, but I haven't heard of it being done at home scale. Storing it and using it safely requires some detailed knowledge. Without proper design and particularly material selection to avoid steel embrittlement and suppress static buildup, your hydrogen tank becomes a vehicle-sized fragmenting pipe bomb that can go off because of an invisibly small spark from a dusty breeze on a dry day, even if it's been working fine for months. Also, because an oxyhydrogen flamefront can exceed mach 30, it's rather difficult to burn in a controlled way without flashing back through the supply line and blowing the tank if you don't have absolutely *all* oxygen purged from the system. Hydrogen can be fun but make sure you know what you're doing before you scale that up. Burned all my forearm hair off playing with that stuff one 4th of July, and that was just a little partially inflated produce bag at atmospheric pressure.
OTOH, circling back to where I started, you could drop a few dozen to a hundred or two dollars on Amazon for some space blankets (or maybe they have mylar in bulk rolls) and have usable amounts of thermal power even in the seasons when the sun isn't very high. This is one of those situations where generating more power is cheaper and easier than trying to store it, especially if we're talking about thermal. Then your problem collapses down to storing enough energy for a few stormy days at a time instead of months, so the thermal battery would probably totally work for cheap even without huge fancy vacuum insulated storage tank arrangements.
I'm planning on testing my proposed setup, I'll let you know how it goes. We still have another foot of snow in the forecast, but this has been on my mind for a few years, and I finally have the space to try it out now. So some time this year. It'll either be "I told you so" or "I burned my heavily forested property down with space blankets." :)
Tangentially, do you have any wind on that giant open flat property of yours? I was thinking about what a massive amount of wind energy you could capture for cheap with a large tarp or two fastened to a light frame on a rope between two trees for support, spinning on a vertical axis tied to the rope, or using the rope itself as a horizontal axis. Have an old broken winch I was going to use as the generator. It's another tree you could try barking up for ultra cheap power, orders of magnitude larger and cheaper than usual home wind turbines. It'd capture so much while being so light, that you'd have to design some flexibility into the structure just so it doesn't snap in a storm.
Anyway, not sure if anybody is going to read all that, but I appreciate your videos. I find them a useful catalyst and reminder for my own ideas. Plus you're just about the only one out of my 3 digits of channel subscriptions who engages in the comments with any regularity. So, thank you for your time. I hope something I wrote here was useful enough to be worth the reading the small novel I apparently just wrote.
With a tiny home that would be so effective in it. Unless you plan to move it around alot.
Interesting experiment.. ❤
Why would you use sand when concrete stores 6x as much heat?
Sand is cheap. Concrete would also break apart if heated too much. I put a heat storage furnace in for my (now late) sister 20 years ago. It used off-peak electric to heat up clay bricks; and that worked good.
Magnefying glass on copper in the sun would be better to heat sand I think.
I tried a couple of experiments with a fresnel lens for heating a container of sand. It works if you have a way to keep the lens tracking the sun. -kind of difficult I thought.
Hello sir.
Sorry for commenting here but I need desperate help from you :(
I have a project to make about nitinol and I just saw your videos (which are awsome and I want to congratulate you for doing them). I will let the videos down below but I want to know this: how can you set a speed to a nitinol engine which is using hot water as source of energy? I mean how can you control how slow or speed is it rotating? In your videos, I saw that you have some kind of "pipe"/lever that goes through the engine and it controls the speed...how is that working?
Thank you and sorry for bothering you :(
The videos:
ruclips.net/video/Zgf6iYHE1bE/видео.html
ruclips.net/video/DJr5Ibwn6ls/видео.html
ruclips.net/video/jpPVvD5SeY0/видео.html
All the lengths of nitinol wire are connected to an off-set cam wheel. The lever you see me using, controls the position of the cam wheel, which directs when the tightening of the nitinol happens as it enters the hot water.
@@doubleMinnovations First of all, I thank you so much for responding sir! Second, can I send you a private message on a social platform? (Mail, Facebook, Discord, Instagram, etc)
I consider the comment section a social platform. Many people like to read and respond to other comments. If you have a question, you can ask in these sections, then all can see. But place them under the video it pertains to.
There is an email address on the channels homepage, but I don't give out personal information.
Why would you want to heat the sand ? For space heating ? Rooting plants?
This is a dirt cheap way to store a lot of energy, for all 24/7 use. For space heating, water heating, for steam production if you have a steam electric power plant.
In cold areas the vast majority of our energy usage is used directly for heating. So if you could store a tremendous amount of heat in a mass of sand and use it somehow, i.e. flowing water or air through the mass. You have a very efficient way of storing heat. People often think of electricity storage when they hear the word "battery". But this is specifically to store thermal energy, and if used properly can be very efficient.
How do you calculate the length of wire to be used.
I just pulled out a bunch of the wire, and connected the positive of the solar panel to one end; with the solar panel in full sun. I connected one lead of the amp meter to the negative of the solar panel, the other lead of the amp meter I moved along the resistance wire until I got the rated amp load stated on the solar panel, and cut the wire there. -Trial and error.
@@doubleMinnovations love it perfect solution without acalculator
Metal or sand ?
Make a box platform and secure wires put my dog bed over it
Only item of concern is heat transfer wire to fasteners to wood
It'd be neat to get a sterling engine running on the heat and try to get some sort of low-tech power generator going for indoor lighting
Use ORC for greater efficiency.