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

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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.

Normal-quality lightning rods in a square pattern can be at most 34 tiles apart, or every 35 tiles, while completely protecting the area between them. This is a density of 1 lightning rod per 35x35=1225 tiles. More tile efficient is a triangular pattern with an outside 42x76 rectangle with one rod in its center. This is a density of 2 lightning rods per 42x76=3192 tiles, or one per 1596 tiles.

To align with a 50x50 grid of roboports the quality needed is epic, as epic-quality lightning rods in a square pattern can be placed 54 tiles apart.

Lightning and Coverage

Each lightning strike is 1 GJ and, when averaged over the night, strike approximately once every 10 seconds per chunk. This means the power-density of lightning is ~100 MW per chunk at night when averaged over the night but this can only be used to recharge lightning rods. The net efficiency of the lightning rods will significantly lower the amount that can be converted to usable energy (see net efficiency below).

A large island on Fulgora can be ~25 chunks and even with only 10% net efficiency the lightning rods can provide 250 MW averaged over the night. This is plenty for early-Fulgora but modules and beacons can quickly exceed this amount requiring higher quality lightning rods or lightning collectors.

Coverage and Tiling

Lightning rods can protect further than their listed radius due to their ability to bridge small gaps between the default coverage areas. As quality increases this becomes less important but for common and uncommon quality this can result in a substantial boost to coverage per lightning rod.

An equilateral triangular tiling is most efficient as this can be placed in a hexagonal pattern that maximizes sphere packing and leverages the gap-bridging mechanism. However islands on Fulgora are relatively small so one will still be required to fill in gaps on the edges in an ad-hoc manner. Nonetheless, triangular tiling even with boundary conditions can result in a 10%-30% improvement in coverage per lightning rod relative to the circular coverage estimate of 3.14 x Range².

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 sustainable. For an isolated large island of ~25 chunks, this implies the following table. The table below assumes 25 chunks must be covered and coverage per rod equivalent to 3.14 x Range². Also even at very high power consumption the stochastic nature of lightning strikes and large area means that multiple lightning rods will be active simultaneously. So 2-3 are assumed active in the table below.

Quality	Coverage (Chunks)	Rods per Large Island	Night-time Power (MW)	Net Efficiency Achieved
Common	0.7	44	300	10%
Uncommon	1.2	26	490	16%
Rare	1.8	17	680	22%
Epic	2.5	13	770	24%
Legendary	4.3	8	1000	34%

Total continuous power achievable over the entire day requires halving the above. Net efficiency can be observed to be significantly lower than listed efficiency due to the drain wasting large amounts of energy.

History

• 2.0.7:
  • Introduced in Space Age expansion.

See also

• Fulgora
• Lightning collector
• Electric system