I am no expert but I am quite skeptical about your "90% of the heat after 5 months". Here are my own calculations: 5 cm of Calcium Silicate (U=0.068 W/mK) has R=0.05/U= 0.7353 m²K/W 11cm of Polyurethane foam (U=0.022 W/mK) has R=0.11/U= 5 m²K/W So the overall R is around 5.7 m²K/W The overall surface of a 1m³ cube is S=6m² (6 faces of 1m²) The temperature delta is T=500K The power loss will be S*T/R = 6*500/5.7 = 526 W So during the FIRST DAY, the energy loss will be 526W * 24h = 12,624 Wh = 12.6 kWh which is 7.5% of the overall 166 kWh of stored heat. Said otherwise, that setup only preserves 92.5% of the stored thermal energy every day. After 1 week 0.925^7 = 58% After 2 weeks 0.925^14 = 34% After 3 weeks 0.925^21 = 19% After 1 month 0.925^30 = 9% After 2 months 0.925^60 = 1% ... Did I make a mistake somewhere? If I am correct then that means that sand batteries are only realistic at a very large scale. For example, if we scale all dimensions by 10 (i.e. a cube of size 10x10x10 surrounded by 1.1 m of PUF ) then R=57 m²K/W and the volume of sand becomes 1000 m³. The stored energy is now 166,000 kWh but the power loss is only 600*500/57 = 5260W (i.e. 100 times more surface but 10 times more isolation). So during the first day, the energy loss is 5260W * 24h = 126 kWh or 126/166000 = 0.075% of the stored energy. The daily efficiency is now 99.925% so after a month the sand battery keeps 0.99925 ^ 30 = 97.7% of its thermal energy.
I agree with your calculations. This is only interesting at higher volumes for 2 reasons. 1) The volume to surface ratio. There is less surface per m3 to lose heat at a higher volume. 2) The capacity. I live in a 15 years old, well insulated house in the Netherlands. Last January I used 4 GJ for heating. Even without losses in storage and transport, I would need about 7 m3 of sand at 500K for the month of January. To have enough heat for the entire winter, I would have to build a new shed in my small garden to store heat.
As the volume cools down, the delta T decreases so as the power losses. However your calculation is sufficient to prove the point, that the seasonal storage cant work at this scale.
@@radomirfilip8741 Yeah. The delta T decreases and so will the amount of energy that will be lost each day. This is why I only gave the kWh figure for the first day. However, the ratio ENERGY LOST / ENERGY STORED shall remain constant over time since both are proportional to the current delta T. This is why I used the 7.25% daily loss (or the preservation rate 92.75%) for the long term computation. PS: And yes, I made a mistake in the first message. 92.5% shall be 92.75% (100% - 7.25%)
Thanks for the video, and best wishes for your channel, but I was really hope to be shown HOT to 'Build a Sand Battery'. I think the idea of thermal energy storage is brilliant, and I think only a complete lack of imagination prevents any village to city from installing them at an industrial/municipal scale. I am planning a larger version of this, but I think your figures of 90% at five months, are fanciful. I would so love it to be true. A house in Ireland uses about 16,000 kWh annually the big majority of this before Feb, so about 100m3 would do it. I think the devil would be in the detail. To get any efficiency, I'd imagine you would need various networks of pipes, air ones and water ones, plus temp sensors throughout, to tell you which pipes you should be using to extract heat. I so want one. I inherited a few acres (13 in three blocks,) with a hope to re-wild most of it, but buy enough second-hand solar panels to build two solar panel 'fences', and store the summer rays for winter days. Get a move-on, world!
My friend. thank you for your attempts and genuine sincerity. Please look into ferrocement water tanks. then foamcrete. then imagine a tank of ferrocement lined with ample foamcrete for insulation and then and inner lining of more ferrocement. You can construct swimming pool sized batteries with insane levels of insulation for very small material usage. Think entire town scales.
Thinking of sand as a fluid or electrical compound, I would imagine more of a "capacitor" type function. Wouldn't it have a high capacity but harder time holding it? Wouldn't your insulating and isolating medium be the most deterministic in its ability to retain that capacity? A deserts sand bakes in the sun all day, and yet it sheds that heat very quickly at night and becomes cold. Theoretically the sand would have to increase its "resistance" as it increases in temperature and then lower as it cools to be somewhat efficient but last I checked, molten glass doesn't cool back into sand when it cools down. That's it... just put a heating element in the center of a well insulated glass sphere, and the heat will be contained within the molten core.
Hi Robert, yes, it is like a capacitor, which increases voltage in a linear way as you pump electric charge in it. In the same way the temperature of the sand goes up, unlike a battery, which stays a some voltage as a chemical reaction is going on. That's my reason to think about Phase Change Materials (PCM) to avoid going in the very high temperature range (which increases heat loss).
Bonjour, Nice vidéo. I'm making a sand battery for a camper. The target is to maintain a °C positive temp. I want to accumalate heat by heating Sand by PTC elements when my lifepo4 battery is full. In your video, you speak about an electrical module to use the excess power. I don't find one which permit to setup the level of voltage equivalent the lithium battery to activate the PTC element... If you have an idea... thanks a lot Fabrice
Bonjour et merci bien. I didn't think for the moment about a temperature control, even if in video 60 I started to look to Smart Home systems. I just pump in the heat and see where the temperature comes. You can see an infrared thermometer in the video, that is what I use for now. Please watch the next video that will bring an update.
Very good 👍 Ive been thinking for many yrs now how to store solar energy to heat my garage over the winter months here in Central Ontario Canada. Im thinking of cutting a large central trench in the middle and putting in a sand battery heated during the sunny days with 1200w of solar. Cheers
Very very good idea, but there's always some man made barriers in our modern society to stop us doing so, the energy safety regulators and the city councils.
That's the plan! At least a smaller prototype, because also video 62, 64 and 65 are candidates and they are higher efficiency because of the heat pump.
Good concept. But I would like to see some real world numbers. If the energy needed to heat my house during winter is about 10.000 kWh, then how much sand at what temperature would I need to heat up during the summer months? Would it be less volume if I used phase change material? How much insulation does it take to make it into spring? In other words, does this make sense to build or does it take up an enormous amount of space? It seems better to use water, which has a five times better specific heat.
The problem with water is that the max temperature is 100C (unless you're going high pressure). I'm skeptical about the insulation aspects. You need 10MWhrs so the answer to the first question, apparently, is 62.5 cubic meters of sand (and, of course at least 10MWhrs of spare solar PV energy.) - you weren't using your garage, were you? :) I joke - but actually if you were building a new house then piling a meter thick layer of insulated sand under the foundation slab and installing the heating coils is not really a bad idea. One thing which was interesting was the impedance balancing of the nichrome wire to the panel impedance. But you'd need a load more than just one panel and if that's the case you'd probably do better to invert the DC to AC as usual and use that output to heat the coils. Also, I think if I were going to try this, I get the wire used in electric furnaces (glass blowing kind of temperatures). I'd like to see someone actually trying this at a residential level.
Hi Charanvantijn, I gave some numbers for 1 m³ of sand: 166 kWh, or 80 hours of a 2 kW heater. That is not enough for winter! I mentioned (but didn't stress enough) that it is a back up system or integration for black out or very cold week. Even if this can be a disappointment, it is simply a great satisfaction that you are covered for those 80 hours with 2 kW when there is a black out or another special problem. The tornado in SE of USA with 4.5 million people with electricity can happen also in the winter (Texas, 3 ears ago). The temperature I mentioned is reasonable, even if 500℃ is really hot and you need mixing with ambient air. The amount of insulation is mentioned in the video (a "tandem" layer is proposed). You can scale this up but 1 m³ is about the max I can ask to most DIY. Phase Change Materials (PCM) will be next video and I will do research to choose a nice one. It certainly will improve the capacity. It will also keep the temperature constant during a long time while the PCM is going back into the solid state. Water has indeed a better capacity per ℃ but limited to 100℃...
@@nnvasen-good-energy If building a new house or barn it would be interesting to dig a basement-sized hole over they whole area of the house, line with insulation and pour in many cubic meters of suitable sand (and nichrome heating wire). Insulate the top too. Store heat in summer then, in winter, you could just open small hole covers in the floor to allow the heat in from below.
Yes sure, it is a very good idea. I don't know how difficult it is to realise it but it will give heat even without holes, it is in fact a big floor heating! But yes, with holes it gives more control and you could even have multi-temperature storage.
I'm definitely curious about the phase change material. I assume it has to be something with a relatively low melting point, to keep things safe. Paraffin wax maybe? Though that's very flammable. A tank of gallium? 😅
Hi W. Coenen, are you also Dutch speaking (seems from name). I would take a much higher melting point because that makes it so practical during heat release. All the time you will have the supply of hot air at for example 300℃ and you can mix that with ambient air. Also you will avoid that above the melting point of wax there is so much temperature range that is (with sand) usable, but the wax will spoil the party.
I am no expert but I am quite skeptical about your "90% of the heat after 5 months".
Here are my own calculations:
5 cm of Calcium Silicate (U=0.068 W/mK) has R=0.05/U= 0.7353 m²K/W
11cm of Polyurethane foam (U=0.022 W/mK) has R=0.11/U= 5 m²K/W
So the overall R is around 5.7 m²K/W
The overall surface of a 1m³ cube is S=6m² (6 faces of 1m²)
The temperature delta is T=500K
The power loss will be S*T/R = 6*500/5.7 = 526 W
So during the FIRST DAY, the energy loss will be 526W * 24h = 12,624 Wh = 12.6 kWh which is 7.5% of the overall 166 kWh of stored heat.
Said otherwise, that setup only preserves 92.5% of the stored thermal energy every day.
After 1 week 0.925^7 = 58%
After 2 weeks 0.925^14 = 34%
After 3 weeks 0.925^21 = 19%
After 1 month 0.925^30 = 9%
After 2 months 0.925^60 = 1%
...
Did I make a mistake somewhere?
If I am correct then that means that sand batteries are only realistic at a very large scale. For example, if we scale all dimensions by 10 (i.e. a cube of size 10x10x10 surrounded by 1.1 m of PUF ) then R=57 m²K/W and the volume of sand becomes 1000 m³. The stored energy is now 166,000 kWh but the power loss is only 600*500/57 = 5260W (i.e. 100 times more surface but 10 times more isolation). So during the first day, the energy loss is 5260W * 24h = 126 kWh or 126/166000 = 0.075% of the stored energy. The daily efficiency is now 99.925% so after a month the sand battery keeps 0.99925 ^ 30 = 97.7% of its thermal energy.
I agree with your calculations. This is only interesting at higher volumes for 2 reasons. 1) The volume to surface ratio. There is less surface per m3 to lose heat at a higher volume. 2) The capacity. I live in a 15 years old, well insulated house in the Netherlands. Last January I used 4 GJ for heating. Even without losses in storage and transport, I would need about 7 m3 of sand at 500K for the month of January. To have enough heat for the entire winter, I would have to build a new shed in my small garden to store heat.
As the volume cools down, the delta T decreases so as the power losses. However your calculation is sufficient to prove the point, that the seasonal storage cant work at this scale.
@@radomirfilip8741 Yeah. The delta T decreases and so will the amount of energy that will be lost each day. This is why I only gave the kWh figure for the first day. However, the ratio ENERGY LOST / ENERGY STORED shall remain constant over time since both are proportional to the current delta T. This is why I used the 7.25% daily loss (or the preservation rate 92.75%) for the long term computation.
PS: And yes, I made a mistake in the first message. 92.5% shall be 92.75% (100% - 7.25%)
You're absolutely right. This guy didn't even calculate anything...
One more problem:
What will be the temperature at the surface of the Calcium silicate ?
More than 400 °C. Not good for the foam.
Thanks for the video, and best wishes for your channel, but I was really hope to be shown HOT to 'Build a Sand Battery'. I think the idea of thermal energy storage is brilliant, and I think only a complete lack of imagination prevents any village to city from installing them at an industrial/municipal scale. I am planning a larger version of this, but I think your figures of 90% at five months, are fanciful. I would so love it to be true. A house in Ireland uses about 16,000 kWh annually the big majority of this before Feb, so about 100m3 would do it. I think the devil would be in the detail. To get any efficiency, I'd imagine you would need various networks of pipes, air ones and water ones, plus temp sensors throughout, to tell you which pipes you should be using to extract heat. I so want one. I inherited a few acres (13 in three blocks,) with a hope to re-wild most of it, but buy enough second-hand solar panels to build two solar panel 'fences', and store the summer rays for winter days. Get a move-on, world!
Timely upload. Really appreciate sharing the creative approach as it helps expand the mental, problem solving toolkit.
My friend. thank you for your attempts and genuine sincerity.
Please look into ferrocement water tanks.
then foamcrete.
then imagine a tank of ferrocement lined with ample foamcrete for insulation and then and inner lining of more ferrocement.
You can construct swimming pool sized batteries with insane levels of insulation for very small material usage.
Think entire town scales.
Thank you Malcolm, this is a great idea for the next video, also to fix the problems of miscalculation (see below)!
Thinking of sand as a fluid or electrical compound, I would imagine more of a "capacitor" type function. Wouldn't it have a high capacity but harder time holding it? Wouldn't your insulating and isolating medium be the most deterministic in its ability to retain that capacity? A deserts sand bakes in the sun all day, and yet it sheds that heat very quickly at night and becomes cold. Theoretically the sand would have to increase its "resistance" as it increases in temperature and then lower as it cools to be somewhat efficient but last I checked, molten glass doesn't cool back into sand when it cools down. That's it... just put a heating element in the center of a well insulated glass sphere, and the heat will be contained within the molten core.
Hi Robert, yes, it is like a capacitor, which increases voltage in a linear way as you pump electric charge in it. In the same way the temperature of the sand goes up, unlike a battery, which stays a some voltage as a chemical reaction is going on. That's my reason to think about Phase Change Materials (PCM) to avoid going in the very high temperature range (which increases heat loss).
Bonjour,
Nice vidéo.
I'm making a sand battery for a camper. The target is to maintain a °C positive temp.
I want to accumalate heat by heating Sand by PTC elements when my lifepo4 battery is full.
In your video, you speak about an electrical module to use the excess power. I don't find one which permit to setup the level of voltage equivalent the lithium battery to activate the PTC element... If you have an idea...
thanks a lot
Fabrice
Bonjour et merci bien.
I didn't think for the moment about a temperature control, even if in video 60 I started to look to Smart Home systems. I just pump in the heat and see where the temperature comes. You can see an infrared thermometer in the video, that is what I use for now. Please watch the next video that will bring an update.
Very good 👍
Ive been thinking for many yrs now how to store solar energy to heat my garage over the winter months here in Central Ontario Canada. Im thinking of cutting a large central trench in the middle and putting in a sand battery heated during the sunny days with 1200w of solar.
Cheers
Thank you Patrick. Maybe you can look to video 62 with the 2 tanks, that gives so much more efficiency (heat pump) if you have space enough.
Very very good idea, but there's always some man made barriers in our modern society to stop us doing so, the energy safety regulators and the city councils.
Well said, but at your house you will not hinder them. Start small and it can become common culture.
Tolle Idee! Vor allem das mit dem Heizelement vom Föhn!!! Hab gerade erst heute ein Föhn mit den Kindern auseinander genommen 😅
Ich mache nächste Wochenend ein neues System, aber jetzt denke ich dass ein altes elektrisches Ofen geopfert wird!
Nice video! Are you going to implement this for your house?
That's the plan! At least a smaller prototype, because also video 62, 64 and 65 are candidates and they are higher efficiency because of the heat pump.
Good concept. But I would like to see some real world numbers. If the energy needed to heat my house during winter is about 10.000 kWh, then how much sand at what temperature would I need to heat up during the summer months? Would it be less volume if I used phase change material? How much insulation does it take to make it into spring? In other words, does this make sense to build or does it take up an enormous amount of space? It seems better to use water, which has a five times better specific heat.
The problem with water is that the max temperature is 100C (unless you're going high pressure). I'm skeptical about the insulation aspects. You need 10MWhrs so the answer to the first question, apparently, is 62.5 cubic meters of sand (and, of course at least 10MWhrs of spare solar PV energy.) - you weren't using your garage, were you? :) I joke - but actually if you were building a new house then piling a meter thick layer of insulated sand under the foundation slab and installing the heating coils is not really a bad idea.
One thing which was interesting was the impedance balancing of the nichrome wire to the panel impedance. But you'd need a load more than just one panel and if that's the case you'd probably do better to invert the DC to AC as usual and use that output to heat the coils. Also, I think if I were going to try this, I get the wire used in electric furnaces (glass blowing kind of temperatures).
I'd like to see someone actually trying this at a residential level.
Hi Charanvantijn, I gave some numbers for 1 m³ of sand: 166 kWh, or 80 hours of a 2 kW heater. That is not enough for winter! I mentioned (but didn't stress enough) that it is a back up system or integration for black out or very cold week. Even if this can be a disappointment, it is simply a great satisfaction that you are covered for those 80 hours with 2 kW when there is a black out or another special problem. The tornado in SE of USA with 4.5 million people with electricity can happen also in the winter (Texas, 3 ears ago).
The temperature I mentioned is reasonable, even if 500℃ is really hot and you need mixing with ambient air. The amount of insulation is mentioned in the video (a "tandem" layer is proposed). You can scale this up but 1 m³ is about the max I can ask to most DIY. Phase Change Materials (PCM) will be next video and I will do research to choose a nice one. It certainly will improve the capacity. It will also keep the temperature constant during a long time while the PCM is going back into the solid state.
Water has indeed a better capacity per ℃ but limited to 100℃...
@@nnvasen-good-energy If building a new house or barn it would be interesting to dig a basement-sized hole over they whole area of the house, line with insulation and pour in many cubic meters of suitable sand (and nichrome heating wire). Insulate the top too. Store heat in summer then, in winter, you could just open small hole covers in the floor to allow the heat in from below.
Yes sure, it is a very good idea. I don't know how difficult it is to realise it but it will give heat even without holes, it is in fact a big floor heating! But yes, with holes it gives more control and you could even have multi-temperature storage.
I'm definitely curious about the phase change material. I assume it has to be something with a relatively low melting point, to keep things safe. Paraffin wax maybe? Though that's very flammable. A tank of gallium? 😅
Hi W. Coenen, are you also Dutch speaking (seems from name). I would take a much higher melting point because that makes it so practical during heat release. All the time you will have the supply of hot air at for example 300℃ and you can mix that with ambient air. Also you will avoid that above the melting point of wax there is so much temperature range that is (with sand) usable, but the wax will spoil the party.
@@nnvasen-good-energy
Sounds far more espensive to impliment versous just sand -- is there a greater payoff over time?
You used a heat retaining volcanic sand, could we use fine river sand or foundry sand? Ik ben het met U eens.
Jazeker, dat kan! I think it will have a similar value of specific heat (kWh/degree and kg).
Yes Patrick, I will talk about prices of Phase Change Materials (PCM) next video and expect to find much higher prices than for sand.
This is very innovative 👏👏👏
Glad you think so Hamza! It becomes better, not only with Phase Change Materials (PCM) but you can also use it in combination with a stove.
@@nnvasen-good-energy that i would like to see