TEG efficiency code tweaks. (#3220)

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## About The Pull Request

Code is [from
citadel](https://github.com/Citadel-Station-13/Citadel-Station-13)
[this PR in
particular](Citadel-Station-13/Citadel-Station-13#15362)
Tweaks TEG code to have efficiency dependent on temperature delta,
instead of whatever the hell whitesands was doing.
This also results in there no longer being an upper cap on TEG output.
Go for a highscore.

![image](https://github.com/user-attachments/assets/a26719b5-9a05-4c92-97dc-65188b415709)
desmos graph if you want to play with numbers:
Y\ =\frac{0.45}{1+\left(e^{-0.0009\cdot\left(X\ -\ 10000\right)\
}\right)}
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## Why It's Good For The Game
more thermodynamically good is better!
makes room for more accurate and balanced TEGs
also tmtmtl said this was a good and easy first step towards better
TEGs.

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## Changelog

:cl:
code: TEG efficiency now depends on temperature delta. 
/:cl:

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code/modules/power/generator.dm

@@ -13,6 +13,7 @@
 	var/lastgen = 0
 	var/lastgenlev = -1
 
+	var/max_efficiency = 0.45
 
 /obj/machinery/power/generator/Initialize(mapload)
 	. = ..()
@@ -75,12 +76,13 @@
 
 
 			if(delta_temperature > 0 && cold_air_heat_capacity > 0 && hot_air_heat_capacity > 0)
-				var/efficiency = 0.45 //WS Edit - Nerfed down to Cit's efficiency
+				var/efficiency = LOGISTIC_FUNCTION(max_efficiency,0.0009,delta_temperature,10000)
+				//2nd (0.0009) effects how 'steep' the curve is, and 4th (10000) effects where the 'middle' is.
 
 				var/energy_transfer = delta_temperature*hot_air_heat_capacity*cold_air_heat_capacity/(hot_air_heat_capacity+cold_air_heat_capacity)
 
+				lastgen += energy_transfer * efficiency
 				var/heat = energy_transfer*(1-efficiency)
-				lastgen += LOGISTIC_FUNCTION(500000,0.0009,delta_temperature,10000) //WS Edit - Buries the 3x3 freezer heater TEG into the ground
 
 				hot_air.set_temperature(hot_air.return_temperature() - energy_transfer/hot_air_heat_capacity)
 				cold_air.set_temperature(cold_air.return_temperature() + heat/cold_air_heat_capacity)