Use for excess energy without sending to grid?

[timselectric]

If you bury them at least 3000m deep, then your sand should remain at 100 degrees C minimum

lol
Not going that deep. More like 6ft to 12ft.
I'm not trying to use the planets heat source. Just storing my own production.

 

[justinm001]

More important is whether water runs through the sand.

It would have to be something other than water ran through a condenser coil in the sand. If the sand is over 100C then it'll boil the water creating a gas and pressure which we wouldn't want. Would need to be an oil or something similar.

I think the idea is burying the sand a few feet underground, running condenser coils through it that'll absorb the heat and transfer to a heating coil inside his home. During the summer it'll work the opposite where the coil is heated up with excess electricity to transfer it to the sand. This is very similar to a geothermal system like I and others have but it'll actually be creating the heat at very high temps for storage for months.

Its a great idea in theory although I do not know how efficient sand is for storing heat or how well of an insulator dirt/clay is to keep that heat months long. Also what long term affects the sand will have when its being heated to 600C back to 13C every year.

I'm not that well versed in sand thermodynamics but I believe the assumption is sand is a great insulator and thus with a large sand pit it'll be very hot in the middle and cooler on the outside, so heat is trapped.... although an issue is the sand needs to be able to absorb a large amount of that heat so you're not just circulating 600C hot oil

 

[Hedges]

Like I said, "More important is whether water runs through the sand."

You've buried the sand and insulated it. But if water gets in, it will carry away the stored thermal energy (as steam, if hot enough, otherwise just run out as water.)

To recover the heat, water/steam might work for use in radiators & generators. Or oil, and a tempering valve (or varied pumping rate) to create water of the desired temperature.)
A heat pipe stuck in the sand would evaporate its working fluid (typically water) and stagnate until you extracted enough energy to condense.

 

[timselectric]

It's a lot simpler than that.
You just heat air and push it through the piping to heat the sand.
Then in winter. You just push the air (heated by the sand) back to the house.

 

[Danke]

It's a lot simpler than that.
You just heat air and push it through the piping to heat the sand.
Then in winter. You just push the air (heated by the sand) back to the house.

Sounds like a lot of hot air to me.

 

[Hedges]

I think sand will be quite poor heat conductor, may or may not impact thermal transfer too much. Would need large surface area.
I think there could be convection of air within the sand.

I'd think electric resistance elements (regulated to not overheat and burn themselves out) near the bottom, and air tubes near the top.
The elements and tubes maybe should be connected to sheet metal or wire fins.

There has to be a waterproof enclosure. And insulation sufficient for high temperature, but not flattened by the weight (otherwise asbestos would be ideal, rock wool for health/environmental reasons.) What materials do you think would meet all the requirements?

Some people remove or fill in swimming pools. This could be an alternative. Would need to be thoroughly sealed, maybe a pump to extract water from the sump.

 

[timselectric]

Sounds like a lot of hot air to me.

Which makes it perfect for me. lol

 

[Ampster]

It's the perfect way to balance the seasonal production.

My seasonal production difference this winter was 2500 kWhs. How much sand would that take?

I can reduce that to 1000 kWhs Net consumption by True Up, but it is the small dollar credit that means I don't pay for that Net consumption.

 

[Ampster]

Could you sell it to the neighbor?

Ironically most utilities have rules that prevent that to protect their monopoly.

 

[timselectric]

Since I will only be using it for heating my house. The system is very simple, and resilient.

 

[timselectric]

My seasonal production difference this winter was 2500 kWhs. How much sand would that take?

I can reduce that to 1000 kWhs Net consumption by True Up, but it is the small dollar credit that means I don't pay for that Net consumption.

There's probably a sweet spot in capacity.
But I assume that any size will work. You will just run a higher temperature in a smaller setup.

 

[Hedges]

My seasonal production difference this winter was 2500 kWhs. How much sand would that take?

SiO2

Specific Heat

680

730

J/kg.K

Properties: Silica - Silicon Dioxide (SiO2)

Silica is one of the most abundant oxides in the earths crust. It exists in 3 crystalline forms as well as amorphous forms. It hasmany useful properties and is used in a range of applications such as silicon, elctronics, refractories, sand, glass making, building materials, investment casting etc.

www.azom.com

(now it is just a word problem.)

There's probably a sweet spot in capacity.
But I assume that any size will work. You will just run a higher temperature in a smaller setup.

Or a gooey molten glass problem.

 

[hwy17]

I've had it in my mind to try out the solar pond concept. I learned of it on this forum. But priorities keep getting in the way.

I guest first test could be just to try stratifying salinity in a small proof of concept, but I don't know if it requires the large heat capacity to keep it stratified.

Solar pond - Wikipedia

en.wikipedia.org

 

[timselectric]

More information

 

[justinm001]

It's a lot simpler than that.
You just heat air and push it through the piping to heat the sand.
Then in winter. You just push the air (heated by the sand) back to the house.

Heating air to super hot temps seems complicated, inefficient and hard to manage. Using something like oil or another fluid would be a better solution as you can control the temps coming/going and the rate of flow. How hot are you planning the air to be and how are you planning to push the air? I'm thinking 400+C is needed to get the sand to be 100C after a couple months.

No matter what medium you use there's going to be losses at storage and at transfer

 

[timselectric]

Or a gooey molten glass problem.

1700°C (3090°F)
Never going to get that hot.

 

[timselectric]

Heating air to super hot temps seems complicated

Simpler than anything else.

No matter what medium you use there's going to be losses at storage and at transfer

That's a given.

But it's all created by excess energy. So it's more of a waste to not use it at all.

 

[SamDeleted]

More information

There's a start up company in the UK using the same idea , but , instead of just using the heat as heat , they flash water into steam to turn a turbine to make electric again

Not sure how efficient they whole process is

 

[timselectric]

There's a start up company in the UK using the same idea , but , instead of just using the heat as heat , they flash water into steam to turn a turbine to make electric again

Not sure how efficient they whole process is

Yup
I'm going the simple route.
Heat in/heat out.

 

[justinm001]

Simpler than anything else.

That's a given.

But it's all created by excess energy. So it's more of a waste to not use it at all.

Typically its boilers and steam which is a big NO NO with insurance companies. I have another house built in like 1890 in WV and it uses hot water to heat the entire 7000sqft that we can't use because of it. I love the idea of some out of the box way to use this system. This system along with the types in the videos still use exchangers to transfer the steam to heat the air. Without this there's all kinds of pressure issues and other concerns. Even just simply blowing HVAC air long distances causes issues with low pressure zones and high pressure zones.

The question that I haven't found an answer for is how much heat is expected to be lost and what they're using to convert the electricity to heat. I'm still trying to watch that great video