Track energy/heat/calories

[ezio-melotti]

(This is based on the [simoc] meeting minutes - dev: 2021 10/17 thread)

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cal vs kcal

• cal aka small calorie aka gram calorie is the amount of heat needed to raise the temperature of one gram of water by one degree Celsius
• kcal aka large calorie aka food calorie is equal to 1000 small calories, and indicate the amount of heat needed to increase the temperature of 1kg of water

Since we are talking about food, let's stick to kcal.

See https://en.wikipedia.org/wiki/Calorie.

J, kWh, and kcal

J (Joules), kWh (kilowatt-hour), and kcal (kilocalories) are units of energy with J being the standard SI unit. Since they are all units of energy, they can be converted directly:

1 J = 1 Ws (Watt per seconds) = 0.000239006 kcal

1 MJ = 0.277778 kWh
1 kWh = 3.6 MJ

1 kJ = 0.239 kcal
1 kcal = 4184 J

1 kcal = 1.16222 Wh
1 kWh = 860.421 kcal

See https://en.wikipedia.org/wiki/Joule#Definition and https://en.wikipedia.org/wiki/Conversion_of_units#Energy.

Energy

The total energy of a system can be subdivided into

• kinetic energy: determined by the movement of an object – or the composite motion of the components of an object
• potential energy: the potential of an object to have motion – generally a function of the position of an object within a field

Some form of energies that are relevant to us include:

Type	Description	SIMOC
Electric	potential energy due to or stored in electric fields	Used by machines, stored in batteries
Thermal	kinetic energy of the microscopic motion of particles, a kind of disordered equivalent of mechanical energy	Produced by most agents
Radiant	potential energy stored in the fields of waves propagated by electromagnetic radiation, including light	Produced by lamps
Chemical	potential energy due to chemical bonds	Stored in food and other compounds
Mechanical	the sum of macroscopic translational and rotational kinetic and potential energies	Humans moving around
Sound wave	kinetic and potential energy in a fluid due to a sound propagated wave (a particular form of mechanical wave)	Machine noise

Heat refers to the amount of energy that is being transferred, and -- like other forms of energy -- is measured in Joules.

See https://en.wikipedia.org/wiki/Energy#Forms.

Tracking energy

Due to the law of conservation of energy, the total energy within the system should remain constant. This also means that the energy going into an agent (e.g. as electricity), should match the amount of energy that is released and/or stored in the agent.

This is analogous to the elemental tracking that we discussed -- which is based on the law of conservation of mass -- and shares similar issues and challenges.

Potato math tracking example

A white potato has these characteristics according to the agent_desc.json:

lifetime: 3168 h
energy input: 0.1952253458 kWh
growth: 0.00125375 kg / h
water vapor out: 0.0027218784338 kg / h

From a quick search we also know that:

white potato calories: 920 kcal / kg
energy to evaporate water: ~0.7 kWh / l 

(source)

We can calculate that the energy input of the white potato is:

tot energy input (kWh): 3168 h * 0.1952253458 kWh = 618.4738954944 kWh
tot energy input (kcal): 618.4738954944 kWh = 532147.71122845123 kcal

And that based on the expected mass and calories the energy of the potato should be:

tot mass: 3168 * 0.00125375 kg = 3.97188 kg
tot energy (kcal): 3.97188 kg * 920 kcal / kg = 3654.1296 kcal 
tot energy (kWh): 3654.1296 kcal  = 4.246910624 kWh

This means that that most of the energy is unaccounted for:

618.4738954944 kWh - 4.246910624 kWh = 614.2269848704001 kWh

Part of this is stored in the water vapor produced:

tot water vapor output: 3168 h * 0.0027218784338 kg = 8.6229108782784 kg
tot energy used to produce vapor: 8.6229108782784 l * 0.7 kWh / l = 6.03603761479488 kWh

However most of the energy is still unaccounted for:

614.2269848704001 kWh - 6.03603761479488 kWh = 608.1909472556052 kWh

Converting heat to temperature

TBD (it seems that the water vapor cools down the environment by sequestrating energy that would otherwise ended up heating the environment)