I heat my greenhouses by thermal buffer (there is a thread on my realization) and I have just made an observation: I have beehives and this season fed my zazas with a solution of sugar 75% sugar, 25% of water). On the one hand, it is very long to heat up and very long to cool. Example, 14 liters brought to a boil at 10 a.m. this morning, were still at 52 degrees around 15 p.m. this afternoon, room temperature around 16 degrees.
I deduce that it might be a good product to store energy but I couldn't find anything on the net regarding this characteristic.
An idea ?
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Example, 14 liters brought to a boil at 10 a.m. this morning, were still at 52 degrees around 15 p.m. this afternoon,
An idea ?
You must be able to find, ex. :
https://fr.baker-group.net/confectioner ... -mass.html
But hey, your syrup brought to a boil, it was not at 100 ° C like water, but maybe at 110 or 120, depending on its concentration.
There is everything I was looking for in this article, but it is true that the boiling point was above 100 degrees. The next batch of syrup, I will carefully measure the temperature.
In the end, I would be surprised if it was higher than water. If it stays hotter for longer, it's also a matter of heat exchange: a molasses, semi-solid, will exchange less than pure water (no or much less convection)
Checking at 80 ° C
The heat capacity of sugar solutions, including sugar syrup and caramel mass, depends on temperature and concentration. It can be calculated by the formula of VV Yanovsky [in J / (kg • K)]
c = 4190 - (2514-7,540 t) * a, (1.13)
where a is the concentration of sugar in the solution, in kg / kg.
The specific heat capacity of water in practical calculations can be taken equal to 4190 J / (kg • K)
c = 4190 - (2514 - 7,54 * (80 + 273)) * 0.75 = 4300 J / kg. K
It is therefore superior to water! My intuition was not good.
Your mixture therefore has 2.6% more heat capacity than water ... at 80 ° C ... and this increases with temperature.
To be greater than water, (2514-7,54 t) must become negative, i.e. from 2514 / 7,54 = 333 K or 60 ° C ...
The problem is that the sugar costs a ton a ton ... for a few percentage gain ...
So your impression probably comes from the weak heat exchanges more than from the few% gained ...
To obtain a 50% gain in heat capacity compared to water, it is therefore necessary to rise to 430 ° C.
Obviously the formula will no longer be valid because (except under pressure) the water at 435 ° C has evaporated from the syrup which has charred!
In fact, as you point out Christophe, it is the heat exchange of the syrup which is thwarted by the viscosity so that if the solution is not stirred, only the base heats up strongly and vice versa, during the phase cooling, for the same reason, it stays hot for a long time.
So no Nobel Prize for this idea, I go back to my studio.
And too bad for the beet trees that I thought I would help ...
I think beeswax would be a better candidate it's a phase change material that can hold a lot more energy ... since you have access to it!
What is its melting point?
After obviously economically it is certainly more expensive than sugar per kWh stored ...
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