understanding power plant aging

[eastwind]

I'm trying to understand the properties that control power plant aging. The minimum age of an unmodified coal plant is supposed to be 38 years (I think this comes from the official guide). But looking at the properties in the SC4tool building reference what I see is a bunch of numbers (16 of them) for "age to maintenance cost multiplier response curve", another similar bunch for "age to output level response curve", a single age degradation rate number (0.001111) and a soft failure threshold (0.898).

Can anyone explain how to interpret these numbers?

[RippleJet]

Let's take the values for the coal plant as an example:


The Age degradation rate is 0.001111

This tells you the degradation per month. This number is added every month to the accumulated degradation.
Once the degradation reaches the value given in Soft Failure Threshold (=0.9), the plant will show visual distress and have frequent outages.

Once the degradation reaches the value given in Hard Failure Threshold (=1.0), the plant stops working or blows up (as given in the property Hard Failure Type).
In other words, after 1/0.001111 months = 900 months = 75 years you won't get any power at all from a coal plant.


The Age to output level response curve consists of 8 paired values, relative age and relative output level:

Relative Age 0.0	Real Age	0.0 years	Output level	100%
Relative Age 0.4	Real Age	30.0 years	Output level	95%
Relative Age 0.5	Real Age	37.5 years	Output level	92%
Relative Age 0.6	Real Age	45.0 years	Output level	86%
Relative Age 0.7	Real Age	52.5 years	Output level	77%
Relative Age 0.8	Real Age	60.0 years	Output level	60%
Relative Age 0.9	Real Age	67.5 years	Output level	35%
Relative Age 1.0	Real Age	75.0 years	Output level	0%

The Age to maintenance cost multiplier response curve consists of similarly 8 paired values, relative age and relative cost:

Relative Age 0.0	Real Age	0.0 years	Monthly Cost	100%
Relative Age 0.4	Real Age	30.0 years	Monthly Cost	103%
Relative Age 0.5	Real Age	37.5 years	Monthly Cost	105%
Relative Age 0.6	Real Age	45.0 years	Monthly Cost	115%
Relative Age 0.7	Real Age	52.5 years	Monthly Cost	130%
Relative Age 0.8	Real Age	60.0 years	Monthly Cost	155%
Relative Age 0.9	Real Age	67.5 years	Monthly Cost	185%
Relative Age 1.0	Real Age	75.0 years	Monthly Cost	300%

Between the given threshold values, the output level and cost multiplier are linearly interpolated.

[eastwind]

Thanks, that's clear (at least to me)!

I guess usage level during the month must modify the age degradation before it's added to the accumulated degradation -- or else the stuff about power plants aging faster if they're run harder is wrong? To get the 38 year minimum lifespan for a coal plant would require doubling the degradation. I don't know where I got this 38 number from, its in a spreadsheet I have from when I played the game a couple years ago that tries to calculate the lifetime average cost per MWh taking all costs into account. But my spreadsheet is clearly too simplistic.

[RippleJet]

There are two properties in the Utilities Simulator exemplar that set these:


The Funding percentage to decay rate multiplier response curve gives a slight variation on the rate of degradation:

Funding Level	0 %	Degradation Rate	110 %
Funding Level	100 %	Degradation Rate	100 %
Funding Level	120 %	Degradation Rate	90 %

The Usage percentage to decay rate multiplier response curve gives a larger variation on the rate of degradation:

Capacity Used	0 %	Degradation Rate	10 %
Capacity Used	25 %	Degradation Rate	20 %
Capacity Used	50 %	Degradation Rate	45 %
Capacity Used	75 %	Degradation Rate	85 %
Capacity Used	90 %	Degradation Rate	125 %
Capacity Used	100 %	Degradation Rate	155 %
Capacity Used	110 %	Degradation Rate	200 %

A lifespan of 38 years would be a result of using the plant at 110% capacity.