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 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

Each lightning strike contains 1 GJ and, when averaged over the night, lightning strikes approximately once every 10 seconds per chunk. This energy can only be used to recharge lightning attractors (i.e. lightning rods and lightning collectors). This means lightning attractors have access to ~100MW per chunk. The net efficiency of the lightning rods will significantly lower the amount that can be converted to usable energy (see net efficiency below).

Lightning strikes do 100 electric damage to struck entities. See Fulgora#Lightning for more details, including immune buildings that do not require lightning attractor coverage.

Coverage

Lightning rods protect buildings within their coverage zone by attracting lightning. As lightning rods have 100% electric resistance, they take no damage. The coverage zone of a lightning rod network is shown when lightning rods are selected or hovered over. In terms of actual building protection, the center of a building must be within the coverage zone to guarantee protection. Hovering over any lightning rod will 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.

The coverage zone of a lightning rod can extend further than their listed range due to the ability to bridge small gaps between the default coverage areas. As quality increases this becomes less important but for normal and uncommon quality this can result in a substantial boost to coverage per lightning rod. 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.

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 Range and height: 0.87 x Range 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: 41 Height: 34	Side: 34
Uncommon	Base: 51 Height: 43	Side: 40
Rare	Base: 59 Height: 50	Side: 47
Epic	Base: 65 Height: 56	Side: 54
Legendary	Base: 81 Height: 70	Side: 66

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 range (3.14 x Range²) 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

Adding coverage area increases the maximum sustainable net efficiency achievable by increasing the highest sustainable base demand that can be met. For an isolated large island of ~25 chunks, this implies the following table. The table below assumes 30 chunks are covered and coverage per rod equivalent to 3.14 x Range². 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.

Quality	Coverage (Chunks)	Rods per Large Island	Simultaneous Powered Rods	Night-time Power (MW)	Net Efficiency Achieved
Normal	0.7	44	2	300	10%
Uncommon	1.2	26	2	490	16%
Rare	1.8	17	2.5	580	19%
Epic	2.5	13	3	770	24%
Legendary	4.3	8	4	1100	32%

Total continuous power achievable over the entire day requires halving the above. The above should be thought of as a realistic upper bound for a single large island. 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 significantly lower than listed efficiency unless one uses foundation and big power poles to bridge separated grids.

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.

History

• 2.0.7:
  • Introduced in Space Age expansion.

See also

• Fulgora
• Lightning collector
• Electric system