Identifying Energy-Saving Opportunities in Oppo tu t es

Greenhouse Operations

Bob SchultheisNatural Resource Engineering Specialist

With special thanks to Scott Sanford, University of Wisconsin – Madison, for his work on this presentation 1

G h E UGreenhouse Energy UseEnergyEnergy

3rd largest cost (~15%)70-80% for space heating70 80% for space heating10-15% Electricity

The Agronomic-Economic BalanceLight transmission for plant growthEnvironmental factors – humidity, temperatureStructure costO ti tOperating costs

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P i i l f H t LPrinciples of Heat LossConductionConduction

Heat conducted through a materialU-value – Btu/(hr-°F-sq.ft.)

ConvectionConvectionHeat exchange between a moving fluid (air) and a solid surface

RadiationRadiationHeat transfer between two bodies without direct contact or transport medium – Sunlight

I filt tiInfiltrationExchange of interior and exterior air through small leaks/ holes in building shell

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Greenhouse types

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Structure EfficiencyyGutter-connected

Lower heat loss / less surface areaBetter space utilization1.5 ratio – heat loss area to floor area (25,000 sq. ft.)

Stand-alone (quonset, gable, gothic)Isolated growing conditionsHeat as filled Natural Ventilation with open / roll-up side walls1 7-1 8 ratio - heat loss area to floor area (3000 sq ft )1.7 1.8 ratio heat loss area to floor area (3000 sq. ft.)

What shape would have the lowest heat loss area to floor ratio?

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Wh t i th b t l ti ?What is the best location?Site selection factorsSite selection factors

Availability of sunlight (8-10 hours/day)Topography (level building site)p g p y ( g )Wind break or hill to north (for heat loss)Proximity to treesDrainage (inside & outside)Logistical convenienceA th tiAesthetics

Decision usually permanent6

Decision usually permanent

G h O i t tiGreenhouse Orientation

Single spanSingle spanEast/West: maximize winter sunlight

G tt t d lti l bGutter-connected – multiple bayNorth/South: gutter shadows move

North

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Gl i M t i lGlazing MaterialsHeat loss

Single pane glass Highest heat loss (1.1 Btu/sq. ft.-hr-F)Longest life (Unless large hail) – 25 years +g ( g ) yHighest cost structure – weigh of glassHigh light Transmittance

Double Polyethylene FilmLow heat loss ( 0.5 to 0.7 Btu/sq. ft.-hr-F)Sh lif 3 4 (UV d d i )Shortest life – 3-4 years (UV degradation)Low costLowest Light Transmittance

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Glazing Material Comparison% Light % Thermal Conduction

Transmission Transmittance Heat loss Estimated

Material PAR IR U-Value Life FlammabilityMaterial PAR IR U-Value Life Flammability

Glass

Single 88-93 3 1.1 25+ none

Double, insulated 75-80 <3 0.7 25+ none

Acrylic

Single 93 <5 1.1 20+ high

Double 87 <3 0.6 20+ high

Polycarbonateo yca bo a e

Single 91-94 <3 1.1 10-15 low

Double (6mm to 10mm) 78-85 <3 0.53-0.63 10-20 low

Fiberglass, reinforced

Single 90 <3 1.2 10-15 high

Polyethylene

Single 87 50 1.2 3-4

Double 78 50 0.7 3-4 Varies

Double, IR 78 <20 0.5 3-4

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I f d R di ti thInfrared Radiation pathwaysGlass or Polycarbonate

P l filPoly-films

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R di tiRadiationSolar or short radiationSolar or short radiation

Absorbed by plants, soil & greenhouse

Re-radiate heat out - long wave or Infrared (IR) radiationVaries with cloud cover

Glass and rigid plastic glazingInhibit loss of IR radiation (< 4% loss)

Polyethylene film IR losses ~ 50%IR losses ~ 50%

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Polyethylene film w/ IR additivew/ IR additive

Reduces IR heat loss by 15-20%Incremental Cost ~ $0.015 / sq. ft.$ qPayback ~ 2-3 months / one seasonNo light transmittance lossesDiffuses light – faster, fuller more even crop growthOften combined with anti condensate (AC) coatingOften combined with anti-condensate (AC) coating

AT Plastics Dura-Film 4 Thermal ACDura-Film 4 Thermal AC Plus

Covalence Plastics Tufflite InfraredKlerk’s K50 IR/AC

K3 IR/ACGreen-Tek SunsaverGreen Tek SunsaverGinegar Plastics Sun Selector AD-IR / Suntherm

InstallationIR film on inside with anti-condensate side down (inside greenhouse)IR film on inside with anti condensate side down (inside greenhouse)Standard poly film used for outer layer

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F t ff ti l iFactors affecting solar gain% Light = % growthGlazing Transmittance

Differences between materials - (75% to 94%)

Condensation can reduce light 15 25%Condensation – can reduce light 15-25%Anti-Condensate Films (additive)Sun-Clear – Spray on anti-condensate

DustAnti-Dust additive

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Double Poly Inflation BlowerDouble Poly Inflation BlowerLocated on inside but drawing air from

t idoutsideCold air has lower humidityLess condensation between sheetsJumpers to ensure proper inflation

Source: http://www.bwgreenhouse.com/products/inflation.htmlSource: http://www.greenhousemegastore.com/Poly-Inflation-

Fan-Kit/productinfo/GF-INFL/

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Gl i M t i l I filt tiGlazing Materials vs InfiltrationInfiltration Rates

Louvers, doors, holes, laps in glazing Glass – high (2x compared with double poly)Double Poly – lowest

Air ExchangesNew Construction Per HourNew Construction Per HourDouble-layer plastic film 0.5 to 1.0Glass, fiberglass, polycarbonate, acrylic 0.75 to 1.5

Old ConstructionGlass, good condition 1.0 to 2.0Glass poor condition 2 0 to 4 0Glass, poor condition 2.0 to 4.0

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Wi d B kWind BreaksPre ailing Wind

• 15 mph wind doubles heat loss

Wi d b k d l 5 10% Prevailing Wind

4-5 rowsMixture:

• Wind break reduces loss ~ 5-10%

• Reduce snow accumulation

• Wind damage

4 to 6 x H

Coniferous & Deciduous• Wind damage

H

4 to 6 x H

50% speed reduction

H = Mature Height of TreesFast growing trees-Hybrid Poplar-White PineWhite Pine

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Infiltration leaksSave 3-10% in heating costs

Check roof and wall vents - seal tightTight coverTight coverGlazing / lap seals on glassFix holes in coverWeather stripping around doorsWeather stripping around doorsDoor sills Roll-up doors – seal for winter?Ventilation louvers close tightVentilation louvers close tight

Dry lubricant - use graphite or TeflonCover unneeded fans / vents during winter

Foam and plasticPlug gaps around foundation – Earth up to sill boardDouble/Single polyethylene over glass – 40% savingsg p y y g g

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C d ti H t LConduction Heat Loss

Insulate side walls to plant heightInsulation must be sealed to wall

North walls – insulate all opaque surfaces and more?and more?

Perimeter 24” below ground – 1 to 2” FoamNew constructionNew construction

Warning Foam Board is flammable keep away from stoves!Warning – Foam Board is flammable – keep away from stoves!

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Thermal / Shade ScreenThermal / Shade Screen

19Saves 30-50% on heating fuel costs

What are Energy Curtains?What are Energy Curtains?Support T k

Insulating Blanket

Track

EdEdges Sealed

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Thermal / Shade Curtains

Thermal curtains 80% of greenhouse heating is at nightReduces night heating up to 50%Double poly w/ internal thermal blanket

– 0 4 Btu/hr-F-ft2 versus 0 7 Btu/hr-F-ft20.4 Btu/hr F ft versus 0.7 Btu/hr F ftDouble as summer shade system

Shade curtainsAluminized shades – 10ºF lower air temperaturesInternal Shade cloth can be as thermal curtain

Costs: $2 to $4 00 per sq ftCosts: $2 to $4.00 per sq. ft. Automated curtains for large greenhousesManual open curtains for hoop houses - Lower cost?

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p p

Curtain Installation IssuesCurtain Installation IssuesPlants hanging from raftersIrrigation hanging from raftersLOTS of things hanging from raftersH ti iHeating pipesPoly tubesH t L ti & h t di t ib tiHeaters – Location & heat distribution

Gable or roof vents or open roof systemsGable or roof vents or open roof systemsFully drawn curtain will restrict summer air flowUse porous curtain material

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Use porous curtain material

Thermal / Shade MaterialsNon-porous material

Highest heat retentionImpervious to water and air movement p

Can fail if water collects on top of curtainSemi-porous materials (preferred)

Allows moisture to migrateAllows moisture to migrateHigh heat retention – 50 to 75%

Porous curtains Allows condensate and rain leakage to drainAllows condensate and rain leakage to drainLower heat retention than nonporous materials – 20 to 30%

Shade in summer / heat retentionShade in summer / heat retentionHigher shading factor = Higher heat retention

Curtain life: 8 to 12 years

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Curtain Materials – Semi porousAluminized and clear polyethylene woven fabric

240% 25% 35% 45% 85%

Whi h h d f t t h ?Which shade factor to choose?Heat of summer maximum sunlight (June July)Heat of summer maximum sunlight (June, July)

10,000 foot-candlesMost bedding and flowering plants can tolerate 4000 to 5000 foot candles of light5000 foot-candles of lightGreenhouse glazing light transmission

Glass ~ 90%Double Poly ~ 80%

10 000 fc x 80% x 55% LT = 4400 foot-candles10,000 fc x 80% x 55% LT 4400 foot candles45% shading/ 55% light transmission recommended (52% energy savings)

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Whi h F l S i th B t?Which Fuel Source is the Best?FuelType

SellingUnit

Avg.Efficiency %Type Unit Efficiency, %

Electricity KwH 100-280Natural gas CCF (therm) 65Natural gas CCF (therm) 65LP (propane) gas Gallon 65-80Wood Cord 15 60Wood Cord 15-60Wood pellets Ton 80Corn (shelled) Bushel 80Corn (shelled) Bushel 80Fuel oil Gallon 60Kerosene Gallon 85

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Kerosene Gallon 85Coal Ton 60

St d d H ti U it (SHU)Standard Heating Unit (SHU)One SHU = 100,000 BTUs,Cost per SHU

= Fuel cost x _______100,000____________ (H t C t t A S Eff )(Heat Content x Avg.Sys. Eff.)

LP (propane) gas = $1.21/gal x 100,000LP (propane) gas $1.21/gal x _____100,000_____ (91,000 BTUs x 0.65)

= $2.05 per SHU

Electricity = $0.07/KwH x _____100,000____ (3413 BTUs x 1.00)

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( )= $2.05 per SHU

H Th R kHow They Rank

H i S F l C CHeating System Fuel Cost Cost per SHU

Pellet stove - shelled corn $ 2.50 / bu. $ 0.75LessGround-source heat pump $ 0.075 / KwH $ 0.78

Air-tight stove - dry red oak $ 160 / cord $ 1.05Pellet stove wood pellets $ 140 / ton $ 1 07Pellet stove - wood pellets $ 140 / ton $ 1.07Air-to-air electric heat pump $ 0.075 / KwH $ 1.33

Natural gas forced-air furnace $ 1.46 / therm $ 1.78Electric resistance heat $ 0.075 / KwH $ 2.20LP gas H.E. forced-air furnace $ 1.70 / gallon $ 2.34LP gas older forced-air furnace $ 1.70 / gallon $ 2.87

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g g

Forced-air furnace - #2 fuel oil $ 2.40 / gallon $ 2.88More

C l l ti h t i tCalculating heat requirements

Basic equation =sq. ft. greenhouse surface x

Basic equation =

temperature difference (inside temp.* minus outside temp.**) x 1.2 = p )

BTU/hour heat needed

*Desired temperature in greenhouse

29**Average low outside temperature for area

Example heat requirementsExample heat requirementsAssumptions:

Free-standing greenhouse10’ W x 12’ L x 6’ H with

6/12 roof pitch6/12 roof pitch

Calculations:Sides: 2 x 6’ x 12’ = 144 sq.ft.Ends: 2 x 6’ x 10’ = 120 sq.ft.Roof: 2 x 5.5 x 12’ = 132 sq.ft.Roof peaks: 2 x ½ x 10’ x 2.5 ‘ = 25 sq.ft.

TOTAL 421 ftTOTAL = 421 sq.ft.

421 sq. ft. x (65°F- 10°F) x 1.2 = 27,786 BTU/hourheat needed

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heat needed

(about the same heating needs as 1,350 sq.ft. home)

G h it h tGreenhouse unit heaters

Low costLow costEase of installationLow installation costsEasily stagedReliable

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Unit Heater TypesypGravity Vented heater -Large diameter exhaust

S t d C b ti BlSeparated Combustion – Blower and intake air duct

Power Vented – Blower meters air flow

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Fuel Savings and Payback

H T I lEst. Fuel % F l F l C

Simple PaybackHeater Type Incremental

CostFuel (Gal.)

% Fuel Savings

Fuel Cost Savings*

Payback (yrs)

Gravity-Vented #& ___ 2494 ___ ___ ___

Power-Vented # $ 200 2078 16% $ 624 0.3(39 days)

Separated $ 3246 2026 19% $ 702 4 6Separated Combustion #

$ 3246 2026 19% $ 702 4.6

HE Condensing Sep Combustion ^

$ 3956 1743 30% $ 1126 3.5Sep. Combustion ^

HE Condensing & Power-Vented

$ 2068 1810 27% $ 1026 2.0

* $1.50/gallon LP gas, # 250,000 Btu/hr rating, ^ 215,000 Btu/hr rating, & manufacturing discontinued33

Gravity Vent Conversion kitsGravity Vent Conversion kits•Convent to Power Vented unit•13% increase in seasonal efficiency• List price (2007): $438 plus installation• Payback – 1 or 2 seasons

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Non-vented unit heatersNon vented unit heatersFuel savings

99% Thermal Efficiency99% Thermal Efficiency80% Seasonal Efficiency

Increases CO2 levelsG d f l t D tiGood for plants - DaytimeCould be used in place of a CO2 generator

Increases H2O levelsCan increase / cause disease problemsIncreased condensation – lower light levels

MUST be used with fresh air intakesOxygen depletion in tight greenhouses ~ poor combustion1 in2 air intake area per 1000 to 2000 Btu/hr of furnace capacity

12” diameter opening for a 250,000 Btu/hr heater

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Non-electric unit heatersConvection heat flowVenting requiredLow Btu / hr capacityp yMultiple units needed per greenhouseMost suited to hobby greenhouses without electricityAir intake for combustion air

ThermostatSingle stage Thermostat

Maintains same temperature day orMaintains same temperature day or night

Set-back ThermostatBattery operated clockBattery operated clockOne setting for day timeOne setting for night timeM t f h tMount away from heater

Source: http://www.southernburner.com/

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Portable Kerosene/Oil Heaters

Only recommendOnly recommend using NG or LP gas for emergencies

Combustion byproducts from oil / kerosene harmful to some plants p(tomatoes) and people

Ethylene, Sulfur Dioxide, Nitrous Oxide CONitrous Oxide, CO

Venting REQUIRED

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Heating System Distribution LocationIn-Floor heating w/ Floor growing system

Concrete or dirt floorHydronic heating (hot water)

B h / U d B h h tiBench / Under-Bench heatingLower heating costs 20-25%

Hydronic or forced air

Study - 7% increased yields for tomatoes

Forced Air Under bench distributionForced Air Under-bench distributionPoly tubes under bench

Approximately equivalent to a 5-10°F reduction inApproximately equivalent to a 5 10 F reduction in greenhouse temperature

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Under-Bench Forced Air

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Under-bench Hydronic heatingUnder bench Hydronic heating

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Under-bench Hydronic heating• Natural Convection /

Thermal buoyancy

• No pumps

Supply from boiler

Distribution to pipes running under benchesrunning under benches

Return piping to boiler41

Heating MaintenancegHeat Equipment Maintenance

Insulation of pipes and ducts in head-houseClean air heat exchangersLubricate motors & fansRemove soot – can reduce fuel consumption by 10%Remove soot can reduce fuel consumption by 10%Steam trap maintenance Burner tune up

Ch f l filtChange fuel filterCorrect nozzle

Thermostat – Calibrate annually Up to 20% fuel savings

Provide air intakes for boilers and unit heatersSmell of combustion gases indicated lack of large enough air intakesg g g

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High Efficiency B il S tBoiler Systems

High Efficiency 90%+High Efficiency– 90%+Hot water boiler systems Modulated firing ratesCondensing Boiler – up to 98% AFUEAdd on to existing boiler

HE Boiler PrimaryyOld Boiler Secondary

Numerous Manufacturers

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Water to air heat exchanger44

Radiant / Infrared H ti S tHeating Systems

Heats objects not airHeats objects not airCan burn plant leavesHeat distribution varies alongHeat distribution varies along pipe on many systemsBest Uses

Loading docksWork areas Publication: Gas-Fired Infrared Heating

for GreenhousesTransplantingSeeding

Warehouse

for Greenhouses

By manufacturer Roberts Gordon LLChttp://www.greenhouse-heater.com

Warehouse

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Environmental ControlsCentral Control Unit to control:

HeatersFansLouvers / VentsIrrigationLightingCO2

Ensures systems are not competing Example - Heater on while vents are open

Computer tied to on site weather dataAnticipates heating and ventilation needs

Use DIF – difference between day and nightPlants see average daily temperatures75°F day, 65°F night - same as 70°F - Save 5% / 10°F DIFy, g

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Space Utilization - Bench Layout

Longitudinal Peninsula Movable

Bench Area Percentageg59% 69% 81%

Aisle

Aisl

e

Aisl

e

Bench

Ben

ch

Bench

Source: Greenhouse Engineering, pg 45 – NRAES-33

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Moveable Benches w/ under Bench heating g

& Bench irrigation

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Space UtilizationpRacking Systems

Take advantage of different plant light andTake advantage of different plant light and temperature requirements

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Hanging Basket SystemsHanging Basket Systems

Pipe system withPipe system with automatic watering

C bl t ithCable system with automatic watering

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Circulation fansCirculation fansMix air to prevent stratification of airReduces heatingDries wet leaves faster – prevents diseaseDries wet leaves faster prevents disease

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Greenhouses - VentilationGreenhouses VentilationEnergy-Efficient Fans

48” fan efficiency48 fan - efficiency Ranges from 12 to 27 CFM/watt

Test data available at:Test data available at:BESS Lab - http://www.bess.uiuc.edu/index2.htm

Agricultural Ventilation Fans, Performance and Efficiencies ($9 + $3 50)Efficiencies ($9 + $3.50)332 Agricultural Engineering Sciences Building, Urbana, IL 61801217-333-9406217 333 9406

36” or 48” fans – efficiency greater than 20 CFM / watt @ 0.05” H2OL di t f ffi i tLarger diameter fans more efficient

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Motor Efficiency – Single PhaseMotor Efficiency Single PhaseHorse Power Typ. Std. Eff Motor High Efficiency

1/4 55% 74%1/4 55% 74%1/3 60 771/2 62-68 78 51/2 62-68 78.53/4 74 841 67 82.5

1-1/2 75.5 842 75.5 82.53 78 85.55 80-82.5 86.5

53Cost for HE motor usually justified if it runs 70% of time or more

G h V til tiGreenhouses - VentilationFan Maintenance

Shutter lubrication & maintenance(dry lubricant – graphite or Teflon spray

Sh tter can red ce air flo b 40%Shutter can reduce air flow by 40%Belt tension / alignment – Automatic tensioners

Loose belt can reduce air flow by 30%yTrim weeds & shrubsBearing lubrication?

Should be using Totally-Enclosed motors(with sealed bearings)

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Passive Solar GreenhouseGreenhouse

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Passive Solar GreenhousePassive Solar Greenhouse

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www.ruralenergy.wisc.edu/esa58

S i tiSummary – energy saving tips

Pi k t i t ti f h tPick correct orientation for greenhouse typeConsider Infrared (IR) plus anti-condensation treated filmsPlant windbreaksPlant windbreaksSeal up the gaps to reduce infiltrationInsulate lower sidewalls when using bench systemsInstall thermal curtains to conserve heat at nightClean thermostats & fans regularlySelect efficient fuel source and heating unitsSelect efficient fuel source and heating units Do a tune-up of furnaces & fan motors and shuttersMove heating pipes & air distribution lower to floor

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G h T l / RGreenhouse Tools / Resources

A E R b it (U i f Wi i )AgEnergy Resource website (Univ. of Wisconsin)www.uwex.edu/energy/greenhouses.htmlNRAES137 Greenhouses for Homeowners and Gardenersextension.missouri.edu/p/NRAES137NRAES-3 Energy Conservation for Commercial GreenhousesGreenhousesextension.missouri.edu/p/NRAES3NRAES-33 Greenhouse Engineeringextension missouri edu/p/NRAES33extension.missouri.edu/p/NRAES33Energy Self-Assessment website (NRCS)www.ruralenergy.wisc.edu/default.aspx

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G h T l / RGreenhouse Tools / Resources

P i S l G hPassive Solar Greenhouseaes.missouri.edu/bradford/education/solar-greenhouse/solar-greenhouse.phpg g p pHigh Tunnelshightunnels.org/M170 High Tunnel Tomato Production extension.missouri.edu/explore/manuals/m00170.htmM173 High Tunnel Melon ProductionM173 High Tunnel Melon Productionextension.missouri.edu/explore/manuals/m00173.htmNational Greenhouse Manufacturers Association

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www.ngma.com

Questions?Questions?Robert A (Bob) Schultheis Program Complaint InformationRobert A. (Bob) Schultheis

Natural Resource Engineering SpecialistWebster County Extension Center

800 S. Marshall St.Marshfield MO 65706

Program Complaint InformationTo file a program complaint you may contactany of the following:

University of MissouriMU E t i AA/EEO OffiMarshfield, MO 65706

Voice: 417-859-2044Fax: 417-468-2086

E-mail: schultheisr@missouri.eduWeb: extension missouri edu/webster

MU Extension AA/EEO Office109 F. Whitten Hall, Columbia, MO 65211MU Human Resources Office130 Heinkel Bldg, Columbia, MO 65211

USDAWeb: extension.missouri.edu/webster USDAOffice of Civil Rights, DirectorRoom 326-W, Whitten Building14th and Independence Ave., SWWashington, DC 20250-9410

"Equal opportunity is and shall be provided to all participants in Extension programs and activities, and for all employees and applicants for employment on the basis of their demonstrated ability and competence without discrimination on the basis of their race, color, religion, sex, sexual orientation, national origin, age,

disability, or status as a Vietnam-era veteran. This policy shall not be interpreted in such a manner as to violate the legal rights of religious organizations or military organizations associated with the armed forces of the United States of America."g

62Portions of this presentation adapted from information provided by:-- University of Wisconsin Extension