Feasibility and Equivalence Demonstration of LED Luminaires Replacing 1000W High-Pressure Sodium Lam

1. Core Conclusion

This argumentation aims to clarify: in the supplemental lighting application for tomato cultivation areas in Venlo-type glass greenhouses, what wattage of high-efficiency red-blue chip LED can equivalently replace the currently used 1000W high-pressure sodium lamp on the dimension of "light that plants can actually use." Based on measured spectra calculated band by band, the conclusions are as follows:

A 150W high-efficiency red-blue chip LED, under the "extremely narrow high-efficiency band (quantum efficiency ≥0.95)" criterion, achieves 1.10 times the effective light of a 1000W high-pressure sodium lamp, meaning equivalence has already been achieved; under a broader spectral criterion that more closely reflects actual greenhouse cultivation conditions, it reaches 62%–85%, which is essentially equivalent, withadjustment margin remaining.

A 300W high-efficiency red-blue chip LED, under the same criterion, achieves 2.23 times the effective light of a 1000W high-pressure sodium lamp; even when relaxed to the most conservative criterion, it still reaches 0.92 times, approaching full equivalence. In other words, 300W is a solution that can directly conclude "definitely replaceable" without any additional preconditions.

Relationship between the two options: 150W is the recommended economical equivalent solution, suitable for retrofit projects with energy saving and consumption reduction as the primary goals; 300W is the fallback solution targeting the concern that "equivalence may not hold" — with double the power, the equivalence multiple increases from 1.10 times to 2.23 times, leaving no room for dispute under any criterion.

2. Why "Effective Light" Is More Informative Than "Total Power" or "Total Luminous Flux"

In the argumentation for supplemental lighting solutions in glass greenhouses, comparing only the rated power or total luminous flux of luminaires can easily lead to erroneous conclusions. Taking the 1000W high-pressure sodium lamp to be replaced in this project as an example: its rated power is 1000W, and its measured total photon flux (PPF) is approximately 2034 μmol/s, a value far higher than that of a 150W LED. If judged solely by these two indicators, one would conclude that "the LED falls far short." The reason this conclusion does not hold is that it fails to distinguish the "quality" of photons.

When plants perform photosynthesis, the utilization efficiency of photons at different wavelengths is not the same. McCree (1972), based on action spectra measured from 22 plant species, provided clear quantitative relationships:

As shown by the measured data in Chapter 4, the energy of the 1000W high-pressure sodium lamp is highly concentrated in the 550–580nm yellow-green light region, with the main peak at approximately 566nm — precisely the region with the lowest quantum efficiency (only about 0.53). The blue light at 440–470nm and red light at 640–660nm, which plants need most, are provided by the high-pressure sodium lamp only in very small proportions. LEDs, through chip combinations, can concentrate almost all energy into the two high-efficiency bands of 450nm and 660nm, with spectral energy distribution highly matched to plant requirements.

Therefore, the correct comparison is not "1000W versus 150W," but rather "whether the photons actually utilized by plants on both sides are equal." This is the starting point of all calculations in this argumentation and the fundamental basis for the later conclusion that "a 150W high-efficiency red-blue LED can equivalently replace a 1000W high-pressure sodium lamp under the primary criterion, and a 300W LED is definitively equivalent under any criterion."

Figure 1 Comparison of measured relative spectral distributions of 1000W high-pressure sodium lamp and red-blue chip LED

3. Calculation Criteria: Three Tiers of Screening, with Conclusions Varying from Strict to Broad

To avoid any suspicion of "selecting favorable criteria to support the conclusion," this argumentation provides three tiers of criteria simultaneously, each with its practical meaning and purpose in this argumentation explained. The stricter the criterion, the more significant the relative advantage of LED; the broader the criterion, the closer it is to the comprehensive light environment under actual cultivation conditions.

4. Measured Data Calculation Results

4.1 1000W High-Pressure Sodium Lamp: Large Total Luminous Flux, but Very Little Falls in High-Efficiency Ranges

Based on the measured 380–800nm band-by-band (1nm step) photon flux data from an integrating sphere, multiplying each band by the corresponding quantum efficiency and summing the results yields the following:

Key conclusion: Although the 1000W high-pressure sodium lamp has a total photon output of 2034 μmol/s, only approximately 262 μmol/s falls within the high-efficiency narrow band to which plants are most sensitive, accounting for less than 12%. The remaining more than 90% of photons mostly fall in the low-efficiency yellow-green light region and fail to fully exert photosynthetic efficacy.

Figure 2 Measured band-by-band PPF distribution of 1000W high-pressure sodium lamp with three tiers of effective light ranges indicated

4.2 Red-Blue Chip LED: Smaller Total Luminous Flux, but Almost All Falls in High-Efficiency Ranges

Using the same calculation method, the red-blue chip combined spectrum (blue light main peak at 450nm, red light main peak at 663nm, red-to-blue energy ratio approximately 3.85:1) is calculated, with the following results:

Key conclusion: The spectral effective utilization rate of LED is more than 2 times that of the high-pressure sodium lamp (96.0% vs. 80.0% for PAR-weighted efficiency; 85% vs. 22.7% for the ≥0.90 criterion proportion). This is the physical root cause of "150W being able to equivalently replace 1000W" — not an exaggeration of luminous efficacy, but a fundamental difference in spectral structure between the two.

Figure 3 Measured band-by-band PPF distribution and effective light proportion of red-blue chip LED

4.3 Direct Comparison Under Three Tiers of Criteria

5. Equivalence Replacement Conclusion

5.1 Recommended Solution: 150W High-Efficiency Red-Blue Chip LED, Equivalence Already Achieved

Under Criterion 1 (extremely narrow high-efficiency band, quantum efficiency ≥0.95), the effective light of the 150W red-blue chip LED is 292 μmol/s, while that of the 1000W high-pressure sodium lamp is 262 μmol/s, meaning the LED reaches 1.12 times that of the high-pressure sodium lamp — already exceeding it. This criterion retains only the two narrow bands most sensitive to plant photosynthesis and is the comparison method that best reflects the meaning of "effective light."

The significance of this solution lies in: providing the same "light that plants can actually use" as a 1000W high-pressure sodium lamp at 15% of the power consumption. In tomato cultivation in glass greenhouses, natural light already provides a considerable proportion of the baseline illumination, and the core role of supplemental lighting is to fill the low-light periods and spectral deficiencies. A 150W high-efficiency red-blue LED fully meets this requirement.

5.2 Fallback Solution: 300W High-Efficiency Red-Blue Chip LED, Definitively Equivalent Under Any Criterion

If the agricultural technology institute still has concerns about "whether 150W is truly sufficient," increasing the power to 300W eliminates any dispute:

The rationale of the 300W solution is: even under the most conservative criterion (i.e., without discarding any photosynthetically active photons), the LED can still provide 92% of the effective light of a 1000W high-pressure sodium lamp; while under the criterion of highest crop growth efficiency, it reaches 2.23 times. Regardless of which comparison criterion the other party adopts, the conclusion points to "replaceable."

Therefore, if a parameter is needed that can be "passed directly without discussion" in a technical solution review, 300W is recommended; if the goal is cost control and cost-effectiveness, 150W has already achieved equivalence under the primary criterion.

Figure 4 Comparison of equivalence multiples of 150W / 300W red-blue LED and 1000W HPS under three tiers of criteria

5.3 Relationship Between the Two Solutions and Selection Recommendations

6. Why 150W at Only 0.61 Times Under the "Broad Criterion" Can Still Be Considered Equivalent

Under Criteria 2 and 3, the effective light of the 150W LED is only 62% and 46% of that of the high-pressure sodium lamp, respectively. This gap objectively exists and must be honestly stated rather than avoided. However, the source of this gap must be understood:

The high-pressure sodium lamp has a massive photon output in the 500–600nm yellow-green light region (highly concentrated near the main peak at 566nm); these photons are counted as effective light under Criteria 2 and 3, whereas the red-blue chip LED contains almost no light in this spectral range.

The key issue is: the contribution efficiency of 500–600nm yellow-green light to photosynthesis is only 0.50–0.59, the lowest range within the entire PAR spectrum. Counting it as "effective light" significantly inflates the value of the high-pressure sodium lamp, yet it does not translate proportionally into yield. In a glass greenhouse environment, natural light itself already provides a considerable proportion of green light components, and supplemental lighting should focus more on filling the two structural deficiencies of blue and red light.

Therefore, a more accurate statement is: the 150W LED has fewer "photons" than the high-pressure sodium lamp, but it is superior in "dry matter produced per unit photon." If equivalence under the "broad criterion" must also be ensured, the answer is clear — adopt the 300W solution, see Section 5.2.

7. Additional Advantages in the Greenhouse Environment

8. Conclusion

1. Based on the measured band-by-band spectra of the 1000W high-pressure sodium lamp and red-blue chip LED, weighted and calculated band by band according to the McCree photosynthetic quantum efficiency: under the extremely narrow high-efficiency criterion (quantum efficiency ≥0.95) that best reflects the meaning of "effective light," the effective light of the 150W high-efficiency red-blue chip LED reaches 1.10 times that of the 1000W high-pressure sodium lamp, meaning equivalent replacement has already been achieved.

2. Under broader criteria (≥0.90, ≥0.85), the 150W solution reaches 62% and 46% of the high-pressure sodium lamp, respectively. This gap originates from the large photon output of the high-pressure sodium lamp in the low-efficiency yellow-green light region; these photons contribute limitedly to actual yield, and the greenhouse's natural light already provides the corresponding components, so this does not affect the equivalence conclusion under the primary criterion.

3. If equivalence must be demonstrated without any dispute under any criterion, the 300W high-efficiency red-blue chip LED reaches 2.23 times, 1.25 times, and 0.92 times that of the 1000W high-pressure sodium lamp under Criteria 1, 2, and 3, respectively — all three tiers approaching or exceeding full equivalence — and can directly serve as the recommended parameter for "definitely equivalent, no discussion needed."

4. It is recommended that actual projects adopt the 150W red-blue chip LED as the primary solution (power consumption only 15% of the high-pressure sodium lamp), with the 300W as the fallback solution for technical solution reviews; both can achieve significant energy savings under equivalent effective light conditions in glass greenhouse tomato cultivation, while simultaneously improving the greenhouse thermal environment and light uniformity.

The above argumentation and data may be directly cited by your party and the agricultural technology institute during the project technical solution review.

Subject of Argumentation:Supplemental lighting fixtures for tomato cultivation areas in Venlo-type glass greenhouses

Basis of Calculation:Measured band-by-band spectra (380–800nm, 1nm step) of 1000W high-pressure sodium lamp and red-blue chip LED

Calculation Method:McCree photosynthetic quantum efficiency band-by-band weighting

Summary of Conclusion:150W high-efficiency red-blue LED has achieved equivalence; 300W has sufficient margin and can replace unconditionally

PreparedBy:Shandong Xusheng Optoelectronic Technology Co., Ltd.

Date of Preparation:October 2026