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IamIan · 01-31-21, 10:49 AM

Thermal Storage

One of the ironies (to me) .. is that I spend energy in the summer to get rid of heat .. and I spend more energy in the winter to get heat .. If only I could only spend the energy needed to move it to when I need it.

Entropy is a rough .. storing energy as a object of a different temperature is difficult to do for any long period of time .. conventional insulation on water heaters and such do ok in the range of storing for a few hours .. but to get even a few days takes extremely high insulation R values .. never mind trying to store a large % of heat energy for weeks or months.

There are a few 'loop holes' .. if the energy is not stored as heat energy .. there are other types of energy storage that do a much better job of low loss over time.

Energy stored in chemical bonds can more easily be stored for long periods of time numerous years .. wood , coal , hydrogen , etc .. but the down side is the very low round trip efficiency .. a large % of the original heat energy is lost by the time you have converted it back to heat.

Energy could be stored in batteries .. some modern types like LiFePO4 and LTO can have very low .. like under 5% self discharge per year .. and they can have high cycle efficiency ~95% or greater .. but the $/kwh is very expensive to do whole house light heating from them for months at a time.

The reversible desecants are a nice option in that sense .. they give off heat when they absorb water , and they absorb heat when they give off water .. they have very high cycle efficiency , and as long as kept dry they can hold that 'potential' energy for years .. there down side is the cost .. $ , weight , and space needed for a given wh amount of energy storage.

Gravity can be nice .. that weight up high on the hill retains all it's gravitational potential energy for as many years as it's up there .. and no exotic materials .. but .. the density some in again .. the amount of space and weight needed to store significant (to heat a home with) amounts of energy is rather large and prohibitive.

- - - - - -

Where I work gets water soluble wood glue by the 55 gallon drum .. Then when it's empty , they throw away the 55 Gallon water tight drum.

I wouldn't use them for potable (drinking water) .. and I probably wouldn't even use them fro 'grey' water to shower with , without allot of cleaning ... but for thermal storage .. the quality of the water doesn't really matter.

Large amounts of heat for a long period of time will still not be very effective / easy with storing energy as heat .. but at least with something like water .. it's specific heat and density mean a higher amount of wh can be stored in a decent size ... about ~46,000 BTUs can be stored in a single ~55Gallon Drum with 100dT like from 40F to 140F .. that can be used in 1 hour @ 46,000 BTU/hr .. or over 10 hours at ~4,600 BTU / hr.

Soo , I'm leaning this way due to the fairly low cost of tinkering with them.

Because of the insulation losses , this is expected to be a few hours to at most a few days of thermal buffer storage .. not seasonable storage .. not 100% of my heating or cooling needs.

Sense the drums are free to me .. and the water fill them is free to me .. I might splurge and get better insulation .. I'm considering maybe going with something like an ~R70 , 3" thick sandwich shell .. 1" R6 foam + 1" R66 Panasonic Vacuum insulated panel + 1" R6 Foam.

The VIP won't be the cheapest option for insulation .. but .. I do like the crazy high R value from such little space .. all said and done to get a similar R value from normal foam board wouldn't end up being much cheaper anyway.

https://www.digikey.com/en/products/...4DcCGBjEBdAvkA

https://b2b-api.panasonic.eu/file_st...leversion/3247

But , can't puncture or cut them .. they are the size they are .. or maybe I'll try it with just R6 Foam board first , see how it does before splurging.

01-31-21, 10:49 AM	#6
IamIan Lurking Renovator Join Date: Oct 2012 Location: RI Posts: 20 Thanks: 4 Thanked 5 Times in 5 Posts	Thermal Storage One of the ironies (to me) .. is that I spend energy in the summer to get rid of heat .. and I spend more energy in the winter to get heat .. If only I could only spend the energy needed to move it to when I need it. Entropy is a rough .. storing energy as a object of a different temperature is difficult to do for any long period of time .. conventional insulation on water heaters and such do ok in the range of storing for a few hours .. but to get even a few days takes extremely high insulation R values .. never mind trying to store a large % of heat energy for weeks or months. There are a few 'loop holes' .. if the energy is not stored as heat energy .. there are other types of energy storage that do a much better job of low loss over time. Energy stored in chemical bonds can more easily be stored for long periods of time numerous years .. wood , coal , hydrogen , etc .. but the down side is the very low round trip efficiency .. a large % of the original heat energy is lost by the time you have converted it back to heat. Energy could be stored in batteries .. some modern types like LiFePO4 and LTO can have very low .. like under 5% self discharge per year .. and they can have high cycle efficiency ~95% or greater .. but the $/kwh is very expensive to do whole house light heating from them for months at a time. The reversible desecants are a nice option in that sense .. they give off heat when they absorb water , and they absorb heat when they give off water .. they have very high cycle efficiency , and as long as kept dry they can hold that 'potential' energy for years .. there down side is the cost .. $ , weight , and space needed for a given wh amount of energy storage. Gravity can be nice .. that weight up high on the hill retains all it's gravitational potential energy for as many years as it's up there .. and no exotic materials .. but .. the density some in again .. the amount of space and weight needed to store significant (to heat a home with) amounts of energy is rather large and prohibitive. - - - - - - Where I work gets water soluble wood glue by the 55 gallon drum .. Then when it's empty , they throw away the 55 Gallon water tight drum. I wouldn't use them for potable (drinking water) .. and I probably wouldn't even use them fro 'grey' water to shower with , without allot of cleaning ... but for thermal storage .. the quality of the water doesn't really matter. Large amounts of heat for a long period of time will still not be very effective / easy with storing energy as heat .. but at least with something like water .. it's specific heat and density mean a higher amount of wh can be stored in a decent size ... about ~46,000 BTUs can be stored in a single ~55Gallon Drum with 100dT like from 40F to 140F .. that can be used in 1 hour @ 46,000 BTU/hr .. or over 10 hours at ~4,600 BTU / hr. Soo , I'm leaning this way due to the fairly low cost of tinkering with them. Because of the insulation losses , this is expected to be a few hours to at most a few days of thermal buffer storage .. not seasonable storage .. not 100% of my heating or cooling needs. Sense the drums are free to me .. and the water fill them is free to me .. I might splurge and get better insulation .. I'm considering maybe going with something like an ~R70 , 3" thick sandwich shell .. 1" R6 foam + 1" R66 Panasonic Vacuum insulated panel + 1" R6 Foam. The VIP won't be the cheapest option for insulation .. but .. I do like the crazy high R value from such little space .. all said and done to get a similar R value from normal foam board wouldn't end up being much cheaper anyway. https://www.digikey.com/en/products/...4DcCGBjEBdAvkA https://b2b-api.panasonic.eu/file_st...leversion/3247 But , can't puncture or cut them .. they are the size they are .. or maybe I'll try it with just R6 Foam board first , see how it does before splurging.