Check my power math

[Occam Blazer]

Doing some power calculations:

A bunker door draws 120w.

It's active for about 44 seconds when closing (39 while opening). That's 120 x 44 = 5,280j.

64 doors draw 5,280 x 64 = 337,920j or 337.9Kj when they open or close.

A jumbo battery stores 40Kj, so I need 337.9 / 40 = 8.4 of them to store enough energy for the demand spike when the bunker doors are running.

Do I have that right?

[Onairda]

Seems fine to me. You loose an extra 1.32kj  (2*44*9/600) from the batteries power runoff, but it's still easily within 9 jumbo since you had more than 20kj of margin. You could probably get away with 8 jumbo or less if you're going to produce power while the doors open (20kj/44s = 455 W is enough for removing the last battery with still a small margin). the only thing you may want to think about is how often you're going to need to open the doors. If you just open and close for every meteor shower, since according to the wiki you can get gold showers as short as 50 seconds, you may need enough storage for both opening and closing, unless you don't mind the doors being slow while opening.

[Occam Blazer]

4 minutes ago, Onairda said:

the only thing you may want to think about is how often you're going to need to open the doors.

Thanks for the sanity check. I think I'm getting brown-outs because I'm not generating enough power when solar is down. There is a little automation to only discharge those jumbos when the doors are opening or closing, but I think I'll add a second bank so I have one for opening and one for closing.

[Gurgel]

14 hours ago, occamrazor said:

A jumbo battery stores 40Kj, so I need 337.9 / 40 = 8.4 of them to store enough energy for the demand spike when the bunker doors are running.

Do I have that right?

You have some loss in the batteries over time, but basically, yes.

[TheMule]

The math is ok, but I feel something is missing. During the time the doors are closed, panels produce no energy. So you have to store energy for two power spikes, the closing and the opening. You have to double the number of batteries.

 

That said, storing energy in batteries is not the only solution, expecially with solar power. One single nat gas geyser is enough, provided you have storage. One reservoir (150Kg) and 10 nat gas generators provide 1,200kJ at 8kW. (64x120 = 7,680W).

So, if you have enough tanks to account for dormancy (or infinite storage) and you don't burn nat gas when panels are active, you don't need a battery bank.

That applies to any fuel you have or can produce. The idea is that you might need quite a lot of generators (13 coal, 10 hydrogen/nat gas, 4 petroleum/ethanol) for the power spike, but not much fuel overall. So even a small source of fuel is enough (one geyser, one hatch stable, etc.)

Ethanol is a special case, since you can have distillers run only when solar power is active. It's wasted energy anyway. Then you burn the ethanol during power spikes. It works better with wild trees but if you don't like pip-planting, domesticated trees work too, the process is only slightly water negative (most of the pwater is recovered via the petroleum generators - if you have clean water you can run a skimmer for the missing part, CO2 definitely is something you'll have plenty of).
 

[Yalp]

9 hours ago, TheMule said:

...storing energy in batteries is not the only solution...

To add to that: 809 kg of steam with a workable temperature of 100 K provides enough energy for an opening or closing procedure as well. Achievable with a Steel AT (and maybe a Tepidizer) or an exploity Tepidizer. A steel AT can provide almost 200 K of workable temperature and the mass of steam can be adjusted to any power demand. Add steam turbines as needed, maybe block ports.

[Occam Blazer]

18 minutes ago, Yalp said:

To add to that: 809 kg of steam with a workable temperature of 100 K provides enough energy for an opening or closing procedure as well.

Yeah, I'm messing around with a heat battery that runs aquatuners when solar is available and steam turbines when it isn't. It works okay.

[TheMule]

3 hours ago, Yalp said:

To add to that: 809 kg of steam with a workable temperature of 100 K provides enough energy for an opening or closing procedure as well. Achievable with a Steel AT (and maybe a Tepidizer) or an exploity Tepidizer. A steel AT can provide almost 200 K of workable temperature and the mass of steam can be adjusted to any power demand. Add steam turbines as needed, maybe block ports.

Tepidizer exploits create energy out of nothing.

Storing power as hot steam is totally feasible with space materials, it's only slightly power negative. It doesn't matter if it's energy that would go wasted anyway. You need 9 steam turbines and a few ATs (maybe even just one), but also quite a lot of steam. 9 turbines delete 785.83 kDTU/s * 9 = 7,072.47 kDTU/s. In 40s, they delete 282.9 MDTU. If I'm not mistaken, that's 645 kg of steam at 305C reduced to 200C, in ideal conditions.

 

[Gurgel]

And alternatively, I can just build a really large battery. Simple, reliable, somewhat less efficient but with solar power, who cares.

[Occam Blazer]

5 hours ago, Gurgel said:

And alternatively, I can just build a really large battery. Simple, reliable, somewhat less efficient but with solar power, who cares.

Normally that's what I'd do. However, I'm using a regular-watt wire power grid and you can't just pop batteries on the backbone without a little automation.

[Gurgel]

1 hour ago, occamrazor said:

Normally that's what I'd do. However, I'm using a regular-watt wire power grid and you can't just pop batteries on the backbone without a little automation.

True. The better I get at this game, the longer it takes for me to go to a "thick wire" power grid.

[Occam Blazer]

I also added this.

I have the space for a few more.