Lightning rod

Lightning rod

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Recipe
5 + 12 + 8 + 4 → 1
Total raw
8 + 6 + 8 + 4
Map color
Health	100 130 160 190 250
Resistances	Electric: 0/100% Fire: 0/90%
Stack size	50
Rocket capacity	50
Range	15 19.5 24 28.5 37.5 + Lightning reach
Efficiency	20% 26% 32% 38% 50%
Dimensions	1×1
Drain	150 MW (electric)
Energy capacity	500.0 MJ (electric)
Mining time	0.1
Buildable only on
Crafted only on
Prototype type	lightning-attractor
Internal name	lightning-rod
Required technologies
Produced by
Consumed by

Object description

Space Age expansion exclusive feature.

The lightning rod is a type of lightning attractor, a building from Fulgora that protects an area from getting struck by lightning from the nightly storms. When struck, they generate power for a limited time. The peak power production is limited only by the demands of the connected electric system, but the internal storage is subject to a 150 MW drain in addition to the load from the electric system. It is unlocked by researching the Planet discovery Fulgora technology.

The lightning rod cannot be crafted on any planet other than Fulgora, as other planets lack the same strong magnetic field.

Lightning Mechanics

Main article: Fulgora#Lightning

For the purposes of understanding lightning rods, there are a few important behaviors of lightning. First is that one can expect 6.48 lightning strikes per night per chunk (32x32 tiles). Each strike contains 1 GJ which can be used to recharge lightning rods and lightning collectors. The net efficiency of the lightning rods will significantly lower the amount that can be converted to usable energy (see net efficiency below). The reach of lightning is 10 tiles and Lightning strikes do 100 electric damage to struck entities.

Most importantly, each lightning strike will have a "source" and a "target". If the source of a strike is within building_reach+ lightning_reach of a lightning attractor (i.e. within range meters, then that strike is guaranteed to only hit lightning attractors.

Coverage

Lightning rods are guaranteed to protect buildings whose center is within the blue coverage zone. This coverage zone is made visible whenever a lightning rod is selected or hovered over. Hovering over or selecting lightning rods will also cause unprotected buildings to display a red border around them. This can be useful when buildings lack power as the plug warning icon will override the thundercloud warning icon. Protection occurs by simply making the lightning rod become the target of the strike. But since lightning rods have 100% electric resistance, they take no damage when struck. For reference, a large island on Fulgora can be ~25 chunks, requiring between ~8 - 45 lightning rods depending on rod quality, tiling, and island shape.

Technically, the blue coverage zone doesn't actually do anything; it is merely a visualization aid. All protection is caused by the fact that lightning with a source within range meters of an attractor will target the attractor. Remember that range = building_reach + lightning_reach. The blue coverage zone is merely a reflection of which tiles cannot be the targets of any generated lightning. Another way to express this is that a location will be within the blue coverage zone if and only if all locations within 10 meters are within the range of a lightning attractor. This has two important implications.

First, the blue coverage around an isolated rod or collector is, by default, equal to a circle of radius building_reach since lightning with a source just outside range can "reach in" lightning_reach meters and hit objects just outside the circle. Second, attractors whose ranges begins to overlap will remove potential sources for lightning strikes targeting tiles in the ring between the building reach and the range. As they get closer more potential lightning sources for tiles in the region are removed and eventually all potential sources for some tiles are removed. When this occurs the blue coverage zone will expand to include them.

Tiling Options

An equilateral triangular tiling is most efficient as this maximizes circle packing when arranged in a hexagonal tiling. For all lightning rods a nearly equilateral triangle of base: 2 x building_reach and height: 0.87 x building_reach will work and provide plenty of flexibility to move the vertices to accommodate interference from buildings. If flexibility is not needed, one can stretch out the size of each tile to the maximums described below.

Quality	Triangle	Square
Normal	Base: 42 Height: 34	Side: 35
Uncommon	Base: 52 Height: 43	Side: 41
Rare	Base: 60 Height: 50	Side: 48
Epic	Base: 66 Height: 56	Side: 55
Legendary	Base: 82 Height: 70	Side: 67

Keep in mind that these are center-to-center distances. The gap between rods will be 1 less than these.

Islands on Fulgora are relatively small and jagged so one will still be required to fill in gaps on the edges in an ad-hoc manner. With reasonably good tiling lightning rods will, on average, cover at least the circular coverage implied by their reach (3.14 x building_reach²) even accounting for the edges of islands. This makes circular coverage a useful estimator for max power.

To align with a 50x50 tiling of roboports one can tile rare lightning rods in an isosceles triangle pattern or epic lightning rods in a square pattern. More generally, aligning with a M x N grid (with M > N for simplicity) with triangles requires that the base > M and height > N. With squares aligning requires that side > M.

Net Efficiency

Lightning rods are ultimately energy storage devices which are recharged with lightning strikes and have unlimited power output potential. However the 150MW drain-to-ground means that they are very lossy storage devices which will rapidly dissipate their stored energy even if unconnected. The actual usable energy we get out of a lightning rod per lightning strike is thus less than strike energy times efficiency. This section provides an overview of this relationship.

Definition of Net Efficiency

Energy stored in a lightning rod will inevitably go to one of two sources: base power or drain. With P representing power and d representing the drain-to-ground, it can be readily seen that the fraction of total energy that goes to each is simply P/(P+d) or d/(P+d) respectively. To see this note that energy-to-source = power-to-source x time and taking the ratio of energy-to-source over total energy will lead to cancelation leaving one with the desired result.

This means we can define a "net efficiency" (which depends on power) of the lightning rod that takes into account the drain by simply multiplying efficiency by the fraction of power we can actually use:

Net Efficiency(power) = Efficiency x power/(drain + power)

If we have N active lightning rods on average then for the purposes of net efficiency analysis, this is effectively 1 big lightning rod with 10 drain sources. Thus for N lightning rods we have a net efficiency of:

Net Efficiency(power, N) = Efficiency x power / (drain x N + power)

Implications

Increasing the size of the lightning rod network increases the maximum sustainable net efficiency achievable by increasing the highest sustainable base demand that can be met. As mentioned this will reduce the energy lost to the drain. This leads to a non-linear effect where e.g. going from a network with 30 chunks in range to 150 chunks in range increases the max sustainable power by 10x rather than 5x.

Since isolated large islands are common, the table below assumes 30 chunks are within range and range per rod equivalent to 3.14 x building_reach². Even at very high power consumption the stochastic nature of lightning strikes and large area means that multiple lightning rods will be powered simultaneously. The best case number of simultaneously powered rods (caused by perfectly spaced lightning) is shown in the table. This means the power figures in the table are more of an upper bound.

Quality	Range (Chunks)	Rods per Large Island	Simultaneous Powered Rods	Night-time Power (MW)	Net Efficiency Achieved
Normal	0.7	44	1.5	200	10%
Uncommon	1.2	26	1.5	340	16%
Rare	1.8	17	2	390	18%
Epic	2.5	13	3	430	18.5%
Legendary	4.3	8	4	640	25%

Total continuous power achievable over the entire day requires halving the above. Again, larger tilings of connected lightning rods will be able to achieve higher net efficiencies, but convergence of net efficiency to listed efficiency is slow. Even arrays ten times larger than the table above will have net efficiencies which are still only 90%-95% of listed efficiency. In practice, net efficiency will be noticeably lower than listed efficiency unless one merges the network of several large islands.

One should note that increased quality leads to the following effects:

• Higher quality Lightning rods stay powered longer due to higher efficiency and lightning strike frequency. This can lead to more rods being powered simultaneously which increases the drain and reduces efficiency slightly.
• The number of active rods is constantly in flux due to the nature of lightning. Higher quality (and properly tiled) lightning rods have lower variance for number of active rods, making max achievable power more predictable.
• Quality lightning rods can reach further into the oil ocean, effectively increasing the coverage area for a given island.
• The vast majority of the increased efficiency of higher quality lightning rods comes from the higher base efficiency. This means re-tiling is not usually necessary unless many rods are active simultaneously and power-density of the base is quite high.

As the table above indicates, in smaller networks the increased number of active drains with higher quality dramatically dampens the benefit of increased quality. In larger networks each increase in quality allows for an ~20% - 30% increase in max sustainable power.

History

• 2.0.7:
  • Introduced in Space Age expansion.

See also

• Fulgora
• Lightning collector
• Electric system