Heat in cold places
Cooling in hot places
Sand cheap, widely available, fireproof, natural, easy to play with, easy to move, already widely used in sandbags for flood control, its even under many roadway surfaces. Sand dunes are features of desolate arid regions, but such dunes of sand are also used for recreation on 4 wheelers and 3 wheels famed for causing serious injuries.
Sand Energy Storage nothing more than pumping heated air into a tall insulated tank filled with sand.
Think of how traditional Turkish coffee made in a wok of heated sand, such that the sand stores the heat energy absorbed by the wok during primary heating.
Its important to understand that storing solar thermal energy in sand or thermal energy created using off peak excess grid power or by burning natural gas or wood or other fuels, once thermal energy stored in the sand, its efficient to use it for heating, district heating, home heating, and even to boil water to make steam to make electricity, but making electricity with the heat means huge loses of efficiency.
There are similar ways of storing energy in Liquid Metal Batteries or LMB by AMBRI, or in heated aluminum.
For example, I have a 10lb SS metal furnace the burns propane + air to heat crucibles made of mixed oxides to very high temperatures. A 4.6 gal 20lb painted steel propane tank + brass valve holds enough fuel to run the furnace for 4-8 hours. During warm seasons I save aluminum beverage cans, crush them with a pneumatic can crusher powered by a small oil-less low noise air compressor, using grid power as input for the air compressor.
It takes about 20 min of heating the crucible in the furnace to get it up to an operating temperature where it can melt the smashed beverage cans and burn off the label and or polymer can liner as a foul smelling yellow flame that comes out of the glory hole of the lid of the metal furnace. I open the lid with thick leather gloves and metal tools by removing it and placing it on a paver brick to protect the driveway or patio where this happens. Then I use tongs to add 3 smashed cans to the hot crucible, the restore the lid and turn the heat back up. Within a minute or so the cans are smelted and other materials are burned off. I then lift the lid and use a long steel spoon to scrap dross off the top, then add more cans and repeat until the crucible is mostly full of hot molten aluminum with a little bit of magnesium since the can lids are made of an AlMg alloy thats 6x stronger than the sidewalls but also 3X more expensive.
Once I have a full crucible of hot liquid aluminum, I use a propane jet torch to preheat a graphite mold sitting on another paving stone, then use crucible tongs to carefully pour the hot aluminum into the graphite to cast aluminum bars.
Heating these aluminum bars on our glass top electric stove top to as a bundle of ten 400 gram AL bars makes a hot metal pile that I carefully transfer to the drivers footwell of my car thats parked outside to help warm the driver area and defrost the cabin during the coldest times during winter. In this way I replace gasoline with human labor effort and electricity and my aluminum bar heat batteries warmed on the glass stove top :)
I also cast scrapped copper wire that I have recovered from other sources in another crucible, into small copper bars in graphite molds, using the same technique, but more heating since copper has a higher melting point and more difficult to work with. I tried doing brass once, but the smoke was toxic and abundant and made me sick, so back to aluminum with an occasional copper run for now. I am also interesting in doing a scrap glass load to try it :)
Playing with metal casting made me notice that aluminum stores a lot of heat energy, and also good at absorbing heat quickly. Many computer heat sinks are made of machined aluminum for this reason, for its thermal conductivity or ability to effectively move heat from a hot sold contact spot to the high surface area fins to transfer the heat away to air blown at the heatsink by a brushless DC PC cooling fan on the CPU or GPU for example. Aluminum also very good at conducting electricity, something I learned about more recently.
Cold Energy Storage for Hot Climates or Hot Weather Seasons
Just at sand can be heated up with hot air, it can also be chilled or cooled with cold air or similar cold loops with refrigerant liquids or gasses. In hot weather the stored cold can be used to absorb heat from inside the building to accomplish energy efficient AC or cooling of indoor spaces. The pumped cold working fluid can then steal heat in the indoor fan assisted heat exchanger radiator setup. Such a system can be adapted with geothermal or air source heat pump systems, such that the large cold trap can store heat or a lack of heat and absorb heat, depending on conditions and season. The HVAC system can then use the sand or aluminum heat battery SHB or AHB to save or discharge heat energy to accomplish heating or cooling respectively.
This YouTube Video about Sand Batteries Should Help
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