Six considerations for determining the value of LEDs in commercial greenhouses HPS LED. Bruce Bugbee Utah State University

Transcription

1 Six considerations for determining the value of LEDs in commercial greenhouses HPS LED Bruce Bugbee Utah State University

2 Nine cardinal parameters temperature humidity light wind CO 2 Root-zone temperature water Nutrients Oxygen

3 Economic Analysis of Greenhouse Lighting Jacob Nelson & Bruce Bugbee 2014 as of 5 April ,000 views

4 HPS 1000 W State-of-the-art Efficacy umol per joule purple LED white

5 Six considerations 1. Distribution of photon output

6 1400 Photosynthetic Photon Flux (PPF; mol m -2 s -1 ) HPS Gavita LED Narrow Focus distance from center (m)

7 100 Normalized Photon Distribution HPS Gavita LED Narrow Focus degrees from center

8 Six considerations 1. Distribution of photon output 2. Time to recover initial cost

9 Difference in initial cost HPS 1030 J/s * 1.7 umol/j = 1751 umol/s LED 215 J/s * 2.5 umol/j = 538 umol/s 1751/538 = 3.3 fixtures $300/fixture * 3.3 fixtures = $ $400. (HPS) = $590. Savings in electricity HPS 2500 h/year * 1 KW/h * $0.10 kwh = $ 250 /year LED 2500 h/year * 0.68 kw/h * $0.10 kwh = $170 /year $ 80 /year $ 590 / $80. = 7.4 years

10 Six considerations 1. Distribution of photon output 2. Time to recover initial cost 3. Maintenance costs

11 Double-ended HPS lamps (1000-W) have a life expectancy of 15,000 hours to 90% initial light output (based on manufacturer literature), or 6 years when used 2,500 hours per year. Adding the cost of lamp replacement every 6 years increases the five-year cost of operation by only 3%.

12 Effect of temperature on decline in output of LEDs Replacement of HPS bulbs 50,000 hours L70 can be 50,000 hours to 70% initial output; 20 years when used 2500 hours per year. Replacing an LED fixture is more expensive than replacing an HPS bulb.

13 Dirt accumulation on the top of a HPS bulb after two years in a greenhouse at Utah State University Light output was decreased about 1 % after 2 years of operation

14 Six considerations 1. Distribution of photon output 2. Time to recover initial cost 3. Maintenance costs 4. Plant temperature

15 PPFD= 1000 µmol m -2 s -1 HPS Grn Hse LED Outside, clear sky Nelson JA, Bugbee B (2015) Analysis of Environmental Effects on Leaf Temperature under Sunlight, High Pressure Sodium and Light Emitting Diodes. PLoS ONE 10(10): e doi: /journal.pone

16 Six considerations 1. Distribution of photon output 2. Time to recover initial cost 3. Maintenance costs 4. Plant temperature 5. Diffuse light

17 At least 7 published studies have found that plant growth was better under fluorescent than LED technologies direct vs. diffuse light

18 Diffuse light penetrates deeper into plant canopies than direct light Direct beam Diffuse

19 Direct beam Diffuse

20 Red Green Blue Craig Brodersen & Thomas Vogelmann Functional Plant Biology. 37: Do changes in light direction affect absorption profiles in leaves?

21 Six considerations 1. Distribution of photon output 2. Time to recover initial cost 3. Maintenance costs 4. Plant temperature 5. Diffuse light 6. Spectral effects on plant size and shape

22 Shade Avoidance Shade Tolerance Relative Photon Flux Full Sun Canopy Shade Wavelength (nm)

23 Lettuce Control +10 % Far-Red

24 Tomatoes Control + 10 % Far-Red

25 Cucumbers Control + 10 % Far-Red

26 Responses to blue light High pressure sodium 5 % blue 100 g Metal Halide 25 % blue 80 g Dougher, T. and B. Bugbee Effects of Blue light on plants. Photochemistry and Photobiology. 126:

27 Swan, Boston and B. Bugbee Blue light reduces leaf expansion and growth in red lettuce.

28 An important supplemental advantage of LEDs Auto-dimming to fill in between clouds

29 60 mol m -2 d MJ m -2 d -1 photovoltaic panels: 15% efficient 70% transmission 4.5 MJ m -2 d -1 The best LEDs can produce 2.4 umol/j 42 mol m -2 d -1 transmitted to the plant canopy 10.8 mol m -2 d -1 delivered to the plant canopy

30 Crop area with equivalent photon flux using electricity from the best solar panels and the best electric lights 1 acre 4 acres solar panels

31 Solar energy 60 moles m -2 d -1 $1,000,000 per hectare per 100 day growing season $1 per m 2 per day Fossil fuels Ground water

32 Without sunlight Fossil fuels to run the electric lights

33 Natural gas heat (joules) Greenhouse vs. indoor agriculture Moles of photons from sunlight 50% Transmission Winter days Moles of photons from electric lights Electricity (joules) Constant 1.7 umol per J

34 Effect of Plant Morphology meristem Erectophile most monocots Planophile most dicots Monocots appear to be less sensitive to light quality, Perhaps because their meristem in protected below several leaf layers

35 Conclusions LEDs are now about 40% more efficient than the best HPS technology, but per photosynthetic photon, the initial cost is still 3 to 5x higher than HPS Maintenance costs are small and similar between technologies Warmer plant temperature from HPS lighting is usually an advantage for supplemental lighting in a greenhouse Diffuse light results in more growth than light directly from above Leaf expansion is often decreased by high blue light Stem elongation can be reduced by high blue light

36

37 soybeans Cool Neutral Warm Fluorescent PPF = YPF = PPE = Volts = Amps = Watts = YPF/PPF = % Blue = PPF Efficiency = YPF Efficiency = cool white neutral 9.02 warm white % blue light: 30% 20% 10%

38 Fig 1. Average absorption (red line) of leaves from tomato, pepper, basil and broccoli. Nelson JA, Bugbee B (2015) Analysis of Environmental Effects on Leaf Temperature under Sunlight, High Pressure Sodium and Light Emitting Diodes. PLoS ONE 10(10): e doi: /journal.pone

39

40 Six considerations HPS less focused warmer plant temp LED more focused cooler plant temp

41 Maintenance costs are small relative to the cost of electricity. Maintenance costs are largely determined by the life expectancy of the fixture.

42 Photobiology studies

43

44 Figure 5. Effect of electricity price on average annual cost over five years for two capture scenarios. Philips LED technology $ W 2.5 umol/ J 2500 hours/ yr Nelson JA, Bugbee B (2014) Economic Analysis of Greenhouse Lighting: Light Emitting Diodes vs. High Intensity Discharge Fixtures. PLOS ONE 9(6): e doi: /journal.pone

45 Photon Flux (µmol m -2 S -1 nm -1 ) Photon Flux (µmol m -2 S -1 nm -1 ) Wavelength (nm) Wavelength (nm)