Greenhouse Energy Cost-Reduction Strategies

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1 Greenhouse Energy Cost-Reduction Strategies Use a Positive DIF & Increase the Deadband Increase the day and lower the night temperature, for example: day/night: 65 F/65 F day/night: 70 F/60 F Dr. Erik Runkle runkleer@msu.edu Also, increase the deadband between heating and venting Temperature Integration +DIF Approximately 75% to 80% of heating occurs at night Therefore, a cooler night and a warmer day can consume less energy while still realizing the same average daily temperature However, this strategy creates a positive DIF, which promotes stem extension in many greenhouse crops Day cooler than night DIF shorter plants Day warmer than night + DIF taller plants DIF Day: 57 o F Night: 86 o F Day: 86 o F Night: 57 o F Estimated Heating Cost per Acre to Maintain Average 65 F in Boston, MA Install horizontal airflow fans Month January February March April +10 F DIF $17,417 $13,333 $11,639 $ 6,8 0 F DIF $17,54 (+1%) $13,667 (+3%) $1,88 (+6%) $ 7,3 (+15%) 10 F DIF $17,73 (+%) $14,109 (+6%) $13,030 (+1%) $ 8,79 (+3%) Horizontal-airflow (HAF) fans: mix warm air near the roof with cool air near the floor Improve temperature uniformity within a greenhouse provide air movement that can reduce disease problems 70 day 60 night 65 day 65 night 60 day 70 night Erik Runkle, Dept. of Horticulture, Michigan St. Univ. January 5, 009

2 Without HAF Fans Nonuniform temperature horizontally Nonuniform temperature vertically Plants dry out slower pathogen problems Start with a larger/older plug Heat and lighting costs are lower per plant during the plug stage than finish stage Although a larger plug takes longer, the finish time is usually shortened by almost as much Requires more propagation space early on, but in the long run can be a profitable strategy Space Use Efficiency To produce 1, cell packs of petunia 88-cell plug trays: Total space used: 10,809 ft -weeks 51-cell plug trays: Total space used: 1,59 ft -weeks In this instance, growing larger plugs used 16% less greenhouse space Use greenhouse space efficiently If you have multiple ranges, try to schedule your crops so that each is filled when first opened Avoid numerous gaps between crops Close spacing will likely increase plant elongation and reduce plant quality, especially for high-light crops Grow cold-tolerant and cold-sensitive crops separately Grow cold-tolerant crops in cool greenhouses (at F), including ageratum, pansy, and ivy geranium Grow cold-sensitive crops in separate, warm greenhouses (at 7-75 F), including vinca, celosia, and New Guinea impatiens Rate of plant development (progress to flowering) Base temperature Linear range Optimum temperature Average temperature ( F) Erik Runkle, Dept. of Horticulture, Michigan St. Univ. January 5, 009

3 Cold-Tolerant Crops Ageratum Alyssum Campanula Cineraria Cyclamen Easter lily Gaillardia Leucanthemum Marigold (French) Nemesia Osteospermum Pansy Petunia Rudbeckia Scabiosa Schizanthus Thanksgiving cactus Cold-Sensitive Crops African violet Alocasia Angelonia Banana Begonia (fibrous) Blue salvia Caladium Canna Celosia Coleus Hibiscus New Guinea impatiens Pepper Phalaenopsis orchid Poinsettia Purple fountain grass Vinca (Catharanthus) Improve insulation Reduce air infiltration: seal gaps near fans, pads, roof vents, and doors Add extra insulation to the north wall Insulate side walls from below the greenhouse floor up to bench height Use an IR & anti-condensation poly as the inside layer of a double poly greenhouse Inflate all double-layer roofs and ensure that blower fans are working Greenhouse Auditing Company INVESTMENT GRADE ENERGY AUDITS Developed by Delta Institute, Chicago, Illinois and EnVise LLC, Madison, Wisconsin Simple Payback Measure (Years) Repair Compressed Air Leaks 0. Install IR AC Poly Film-Roof 0.6 Insulate Hot Water Distribution Piping 1.0 Dehumidify Roof Plenum Air 1. Reduce Air Infiltration 1.3 Install VFDs to Control Hot Water Supply Pumps 1.3 Insulate Walls.1 Replace Double Poly with Triple Poly Roof.6 Replace Steam Boilers w/direct Fired Hot Water Heaters 4.1 Number of Companies 3 3 Provide long days to long-day plants Provide at least 10 footcandles to bedding plants and perennials that are long-day plants Light until early April, when the days become naturally long In general, provide long days to plugs during the last two weeks, and to finish plants until flower buds are visible Erik Runkle, Dept. of Horticulture, Michigan St. Univ. January 5, 009

4 Rudbeckia hirta Indian Summer Short Days Long Days Petunia Fantasy Pink Morn Short Days Long Days 61 days to flower 34 days to flower Plants that require a particular photoperiod have an obligate, or qualitative response (long days are required). Plants that flower more rapidly under a particular photoperiod have a facultative or quantitative response (long days are beneficial). Bedding Plant Responses to Photoperiod Short-day plants African marigold (O) Cosmos (F) Dahlia (F) Morning glory (F) Salvia (F) Zinnia (F, some cvs.) F = facultative response O = obligate response Day-neutral plants Cleome French marigold Geranium Impatiens N.G. impatiens Thunbergia Tomato Vinca Wax begonia Zinnia (some cvs.) Long-day plants Ageratum (F) Blue salvia (F) Dianthus (F) Fuchsia (F or O) Gazania (O) Lobelia (blue) (O) Pansy (F) Petunia (F or O) Rudbeckia (O) Snapdragon (F) Strawflower (O) Sunflower (F) Tuberous begonia (O) Verbena (F) Provide supplemental lighting to plugs and liners Provide light from high-pressure sodium lamps to plugs & liners until mid-march Lighting during the plug/liner stage can reduce plug timing and also induce plants to flower earlier at the finish stage Investment costs for lamps are returned quickly with plugs/liners, not as much so with finish crops Average Outdoor Daily Light Integral (mol m - d -1 ) New Guinea Impatiens Harmony White 16 Days after stick Average DLI (mol m - d-1 ): December January February March Media Temperature = 77 ºF (5 ºC) Maps from Jim Faust, Clemson University Erik Runkle, Dept. of Horticulture, Michigan St. Univ. January 5, 009

5 For More Information 98-page book and cd containing articles on greenhouse lighting Published by Meister Pro $34.95 (plus shipping) To order a copy, visit Use a retractable energy or shade curtain Most heating (about 80%) is used at night Using a retractable curtain can significantly reduce heat loss and also increase plant temperature A closed-weave curtain that provides 35% shade can reduce heat loss by 30% to 50% at night Curtain Materials Shade curtains are commonly made of a woven material containing aluminum strips, and can be of open or closed (using transparent plastic strips) design Thermal blankets reduce plant heat loss at night by creating a warmer surface above the greenhouse crop. Thus, more radiant energy is emitted to the crop than a cold glazing material. The aluminum strips efficiently reflect incoming radiation with minimal absorption 35 F 64 F 64F Open design: air passes through Closed design: air is trapped Don t cheat on heat Crops grown cool require a longer production time To market plants on the same date, crops need to be started earlier in the year or from a larger plug In the spring, cold-sensitive crops grown cooler can actually require more heating per crop than the same crop grown warmer and planted later. Estimated Greenhouse Heating Costs A software program developed by the USDA-ARS in Toledo, Ohio to estimate energy costs for greenhouse heating based on: Greenhouse location Time of year Greenhouse characteristics Energy type and cost Heating setpoints To download for free, type virtual grower into an internet search engine Erik Runkle, Dept. of Horticulture, Michigan St. Univ. January 5, 009

6 Which Scenario Is Less Expensive? Continuing to grow a crop at a relatively warm temperature Growing a crop at a lower temperature for a longer period of time Crop Timing at Different Temperatures Time to first flowering from transplant of 88-cell plugs grown at different average daily temperatures under a 16-hour photoperiod and daily light integrals (DLI). DLI Average temperature ( F) Marigold 'Antigua Primrose' Petunia 'Purple Wave' Crop Transplant Date at Different Growing Temperatures Estimated heating cost (US$) to produce ½ an acre of greenhouse crop in Grand Rapids for two market dates Approximate date of transplant from a 88-cell plug required for first flowering on April 1 (8 mol m - d -1 ) or May 15 (16 mol m - d -1 ) at four average temperatures. Crop April 1 finish 63 F May 15 finish 63 F April 1 finish May 15 finish Marigold 15,147 15,966 15,897 14,117 6,36 6,90 7,196 7,590 Crop 63 F 63 F Petunia 14,601 11,560 9,859 8,958 6,597 4,885 4,8 4,104 Marigold 1/17 1/7 /5 /14 3/11 3/18 3/4 3/30 Petunia 1/0 /10 /1 /8 3/8 3/9 4/10 4/16 Calculations performed with Virtual Grower.0 software with constant temperatures. Greenhouse characteristics: 8 spans each 11 ft 4 ft, triangular 1 ft roof, 9 ft gutter, polycarbonate bi-wall ends and sides, forced air unit heaters burning natural gas at $1.00 per therm ($10.4 MCF), 45% heater efficiency, no energy curtain, and air infiltration rate of 1.0. Greenhouse Energy Website Acknowledgments Project GREEEN, the Fred C. Gloeckner Foundation, the American Floral Endowment, and the USDA Floriculture and Nursery Research Initiative for funding Funding and donations from private greenhouse companies and greenhouse grower associations The Michigan Agricultural Experiment Station for subsidizing greenhouse operating costs Lee Ann Moccaldi and Roberto Lopez (former MSU graduate students) and Mike Olrich (MSU Floriculture research technician) Erik Runkle, Dept. of Horticulture, Michigan St. Univ. January 5, 009