Give feedback: steam power overhaul

[crysanja]

All the production steps, from start to finish, use the "same" energy amount.
With higher tier production facillities, it becomes cheaper.

Maybe the mod lacks some high energy intenive products.

[bobingabout]

It's not quite true.
All HE's have 100% efficiency, so use the same amount of fuel.
All boilers have different efficiencies, 50% for the T1 and +10% per tier, ending at 90% for T5.

[Nightinggale]

Drop the Efficiency above 100% from the steam engine, making them 100% efficient across the board (Since the steam engine is tuned to that tier of boiler, and higher temperature steam is wasted in a steam engine, there's no incentive given for the higher efficiencies anymore)

Actually steam engine efficiency highly depends on pressure and the higher the better. This goes for boiler as well as piston/turbine.

Let's look at a classic steam locomotive with copper firebox. Copper has great heat transfer properties and is a great metal to keep between fire and water, but it's a bit soft and it caps the boiler pressure at 12 km/cm^2 (11.7 bar/125 psi). This was for ages the standard steam locomotive and is what you will most likely see if you see preserved steam today. Higher pressure existed, but the change of metal and production methods meant they came at a steep price. High quality steel were used in high pressure boilers.

At this pressure, the boiling point for water is 200 °C. This mean the boiler takes in 20 °C water, heats it by 180 °C and then it goes from water(200 °C) to steam (200 °C). Looking at the amount of joules needed for this step, the latter part takes up 2/3 of the energy. As the pressure increases, the boiling point increases, but the energy needed to go from liquid to gas decreases. Interestingly the latter is numerically bigger, meaning increasing the pressure will reduce the overall cost of making steam.

The problem is that this is saturated steam, meaning it will try to condense all the time and whatever condenses will be a waste and needs to be drained. The solution is a super heater. Pipe the steam pipe through loops in the smoke and heats it to 400 °C. The temperature will have to drop to 200 °C before it starts condensing again. This step gives a 30% decrease in fuel consumption.

Last step is the cylinders. At low speed, steam is added to one side until the piston reaches the end and then it switch side (mainly stall avoidance). However when speed increase, the duration and timing of when steam is added is changed. It relies on the fact that steam expands as the pressure drops. If you have one liter of air at 10 bar and you increase the volume to two liters, you have 5 bar of air. If you have 10 bar of steam and double the volume, the steam will expand and you will have something like 8 bar. This is very important because it allows adding steam like 20% of the time and then let it expand to push the piston for the rest of the stroke.

Simply put, there are two main keys to reducing fuel consumption while maintaining the same power output and they are linked. One is the boiler and the fact that the price of creating steam is linked to amount, not pressure. The other is the valve timing, meaning higher pressure for a shorter duration (read: less steam usage each cycle) will provide the same power.

Leaving steam locomotives, the same is true for turbines. Low volume at high pressure will provide the same output as low pressure with a high volume. There are other tricks, like making the steam go through 3 turbines in series (triple expansion). The energy gained from a piston/turbine doesn't depend on pressure, but rather the pressure difference between input and output. If you rapidly cool the output, it will condense and create a vacuum, ideally half the pressure of the outside air and you gained energy out of the steam even after it lost the pressure. This will require a lot of cold water and the steam exits as hot water.



An entirely different question is how it should work ingame. Despite what I just wrote, I vote for keeping it simple. It's a game. It needs to be fun to use. The numbers need to be human readable. The effects of different setups needs to be somewhat predictable to the player even if the player isn't an engineer. One boiler feeds two steam engines is a good guideline and it makes it easy to plan your power supply layout.


I have been wondering about fuel consumption. More specifically oil burning fuel consumption. If you want to turn oil into power, you either refine and make solid fuel or you go for oil burning generators. Steam is much earlier in the research tree and it comes at the cost of making the solid fuel while oil burners are much harder to build (electric engines, which can't be hand crafted), meaning I would assume oil burners would use less oil. However I started calculating the power output for each unit of oil and it looks to me like oil burning is useless with the current numbers.

Let's take a tier 1 refinery and feed a chemical plant. The refinery produce 6 light oil/s. The chemical plant consumes 4.167 light oil/s. Burning the solid fuel from 4 light oil/s in tier 1 boilers to feed tier 1 steam engines provides 5 MW. The refinery and chemical plant consumes 630 kW combined, leaving 4.37 MW surplus. Even with the added power cost of inserters, it's way better than the highest tier oil burner, which only provides 3.5 MW when consuming 4 liquid/s. Using the highest tier boiler and steam engines, the solid fuel approach can provide 9.5 MW at 4 light oil/s and the production cost is still only 630 kW.

Using heavy oil will double the oil usage for each solid fuel, but it's still providing 4.1 MW for 4 heavy oil/s after subtracting production costs.

This leaves the question: when will it make sense to use the oil burners? Also what about oil burning boilers? Wouldn't it be more efficient to burn the oil directly than it is to convert it to solid and then burn it?

[bobingabout]

Part of the reason why I'm removing the efficiency from steam engines is simply because it starts at 100%, and goes above it. I'm also just trying to simplify things. In theory I could make up for this reduced efficiency by reducing the efficiency of the vanilla steam engine, but don't really want to nerf the starting position... I guess I could buff the boilers to balance out a nerf of the steam engines... The problem there is that you end up using more water to compensate for the lower efficiency of the steam engine, which starts to make things complicated again (Which is why I want 100% across the board)

Direct oil burning boilers is something I would like to do, but there is no support for it right now. Klonan does something in his mod, but it's actually an electric boiler that turns oil into steam... or something like that.

But, I do need to look into fuel consumption elsewhere too. Part of the fluid generator's failing is it's low efficiency, though the Hydrazine generator top end is definitely better. I went with lower efficency on purpose as to not make it too overpowered, since you can simply dump oil into it directly without having to process first, but it is still more processing than steam so...