Supplemental Light Shortfall Hours

Invert measured natural-light deficit into supplementary hours with delivery loss and a caller available photoperiod; unmet photon budget is explicit, not a crop lighting recommendation.

Description

Daily light integral is accumulated photon dose per area.

Daily light integral is accumulated photon dose per area. A measured natural-light shortfall can be converted to supplementary operating time when delivered PPFD is known.^{[1, 2]}

Invert measured natural-light deficit into supplementary hours with delivery loss and a caller available photoperiod; unmet photon budget is explicit, not a crop lighting recommendation.

When to use Supplemental Light Shortfall Hours

Use this tool to invert measured natural-light deficit into supplementary hours with delivery loss and a caller available photoperiod; unmet photon budget is explicit, not a crop lighting recommendation.

Prepare the plant, nutrient, light or scheduling measurements for the intended crop and period. Keep paired records aligned and confirm units and supplied target values.

How to use Supplemental Light Shortfall Hours and understand its results

Prepare the plant, nutrient, light or scheduling measurements for the intended crop and period. Keep paired records aligned and confirm units and supplied target values.
Enter targetDailyLightIntegral, measuredNaturalDailyLightIntegral, supplementalPpfd, lightDeliveryFraction, remainingPhotoperiodHours using the field table and calculation rules, then run the tool.
Read requiredSupplementalHours, deliverableSupplementalDose, remainingDoseShortfall, withinAvailablePhotoperiod. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
targetDailyLightIntegral	Target daily light integral	number	Required
measuredNaturalDailyLightIntegral	Measured natural daily light integral	number	Required
supplementalPpfd	Supplemental ppfd	number	Required
lightDeliveryFraction	Light delivery fraction	number	Required
remainingPhotoperiodHours	Remaining photoperiod hours	number	Required

Use nonnegative doses, positive supplemental PPFD and delivery fraction in (0,1], with available hours in [0,24]. Return required hours, dose deliverable within available time, remaining shortfall and an inclusive within-time flag.

shortfall=max(0,target−natural dose); hours=shortfall/(supplemental PPFD × delivery fraction × 0.0036)

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
requiredSupplementalHours	Required supplemental hours	number
deliverableSupplementalDose	Deliverable supplemental dose	number
remainingDoseShortfall	Remaining dose shortfall	number
withinAvailablePhotoperiod	Within available photoperiod	boolean

json

{
  "input": {
    "targetDailyLightIntegral": 10,
    "measuredNaturalDailyLightIntegral": 4,
    "supplementalPpfd": 100,
    "lightDeliveryFraction": 0.5,
    "remainingPhotoperiodHours": 8
  },
  "output": {
    "requiredSupplementalHours": 33.333333333333336,
    "deliverableSupplementalDose": 1.44,
    "remainingDoseShortfall": 4.5600000000000005,
    "withinAvailablePhotoperiod": false
  }
}

Limitations and assumptions

The target and delivery loss are supplied. This photon-budget calculation is not a crop-specific lighting prescription.

Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use Daily Light Integral MOL M2 Day: Integrate measured time-varying PPFD by trapezoids into observed daily photon dose; unobserved hours are not silently filled and a constant PPFD-to-DLI alias is excluded. For a complementary task, use LED Cost Per DLI Delivered: Compare electrical and allocated fixture costs per delivered canopy photon mole and per DLI unit using supplied efficacy/delivery; canopy area distinguishes total photons from areal dose.

Further background: Measuring daily light integral in a greenhouse.

References

Supplemental Light Shortfall Hours — tool.io
Measuring daily light integral in a greenhouse — Purdue Extension

Similar or alternative tools

Daily Light Integral MOL M2 Day
Integrate measured time-varying PPFD by trapezoids into observed daily photon dose; unobserved hours are not silently filled and a constant PPFD-to-DLI alias is excluded.
LED Cost Per DLI Delivered
Compare electrical and allocated fixture costs per delivered canopy photon mole and per DLI unit using supplied efficacy/delivery; canopy area distinguishes total photons from areal dose.