A Review of Greenhouse A Review of Greenhouse Energy ConservationEnergy Conservation

By Paul A. Thomas, By Paul A. Thomas, University of GeorgiaUniversity of Georgia

2006 Oklahoma Conference

Change of Energy Prices Over Time

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Coal

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Kerosene

LPG

Typical Annual Energy Expenditurefor a Commercial Greenhouse

Electricity

Heating

Shipping

10-15%

5-10%

70-80%

Source: 2001Bartok, NRAES-3

How Do I Do An Energy Audit?1. Pull all your financials from the last 5 years.

2. Inspect your greenhouse – note energy using equipment, tasks, areas of key work. Note electric draw, output BTU’s and hours used.

3. Pull your heating, transportation and electric bills (monthly). Graph them.

4. Calculate usage costs per item, area, or task

5. Calculate savings on Changes, Upgrades or Replacements. Do a payback calculation.

Structural Heat Loss

Energy curtain 20-50%

Go double! 40-50%

Stop leaks

FoundationInsulation3-6%

Side wall insulation5-10%

fan Fan box Insulation1-5%

Heater exhaust

Peter Ling – OSU, 2006

Structural Paybacks*

Install clear divider curtains = 1.2 yearsDouble poly over leaky glass = 0.8 yearsInsulate North wall – 2” Ins. = 2.0 yearsInsulate E, W, walls – 2” Ins = 2.8 yearsHeat Curtains – Inside = 2.3 yearsRelo / Aspirate Sensors = 0.4 yearsEstablish a north windbreak = 1.2 yearsCalk Cracks. Lap seals, etc. = 0.7 years

* NRAES, U of Minnesota, SAF, DOE, and other sources.

Structural Heat Loss

Photo: Peter Ling - OSU

Photo: Peter Ling - OSU

Heating / Cooling System Paybacks

Prevent Overlapping Controls = ImmediateRepair (align) Louvers / Vents = ImmediateInstall Draft Baffels ( Entrances) = 1.1 YearsRepair Heating Systems = ImmediateInsulate Steam / Hot water pipes = 0.5 YearsImprove Existing Heater Efficiency = 0.08 YearsRepair Water Leaks = ImmediateCalk & Weather Strip Doors = 0.7 YearsUse More Efficient Fan Motors = 0.4 Years

Upgrade Conventional Heating Systems

High Mass Boiler Condensing Boiler

Hot water is still the most efficient way to heat a greenhouse!

30%

Reduction

Mass vs Condensing Boilers

Mass boilers rely on the massive amount of steel / metal to hold heat. This maintains a steady supply of heat even if short term changes in boiler efficiency occur. However, they must be kept hot during off peak need periods, and cannot be responsive to rapid changes in external greenhouse temperatures

Condensing boilers have much less mass, and rely on fast heating and efficient use of fuel to be cost effective. They can save up to 30% in fuel consumption, and can respond quickly external demand.

Energy Curtains

• Increased Insulation is gained when energy curtains form still air layer between the curtain and roof

• Reduced radiation heat loss from reflective material, especially effective in poly houses

• Reduced volume of heated air!

Peter Ling – OSU, 2006

Peter Ling – OSU, 2006

Conserving Electricity

Use Low Energy Light Bulbs = 0.87 Years

Turn Off Lights (Evening) = Immediate

Focus Lights On Task Areas = 0.5 Years

Incandescent vs CFL

CFL Payback is 1.5 yearsSavings is $55.00 / bulb

1000 hours 8000 hours

Light Emmiting Diodes

LED use half the Energy of

CFL’s and last 10,000

hours

Glazing

50OF 60OF 70OF

Glass 30,393* 59,014 107,342

Poly 18,089 36,529 66,097

Poly + IR 11,701 24,025 43,683

Poly + IR + Curtain

8,995 18,252 33,027

Source: 2006, A.J. Both & D.R Mears, Rutgers University* BTU’s expended / hour to mainain set point temperature (10 year average)

BTU’s / Hr Required at Different Set Points Using Different Glazing Technology Levels.

Crop Base Temperature

64OF 61OF 58OF

Warm Season Crops – 410F

15% 18% 21%

Cool Season Crops – 450F

11% 13% 15%

Modified from Source: 2006, Eric Runkle, MSU Greenhouse Alert)

Estimated Delay in Crop Finishing Time.

How much does a week of energy cost you?

21% increase in an 8 week crop is 1.68 weeks x weekly heating cost!

Management Changes

• Improve Scheduling = Immediate• Improve Delivery Routing = Immediate• Maximize Payloads = Immediate• Establish Regular Maint. = Immediate• Improve Crop Turn Opt = 0.37 Years• Convert Unused GH Space = Immediate• Reduce Crop Loss = Immediate• Group Plants by Temperature = Immediate• Review Energy Use Monthly = Immediate

Rethink Plug Sizes and Schedules

• Larger plugs will finish sooner…you can start later when heating is not so extreme!

• Changing your crop inventory away from high heat requiring species until later in the spring can allow significant savings.

• Rethink unreasonable customer expectations…can you afford to meet them?

Conserving Water

• Reduce overall use of fertilizer

• Reduce cost of pesticide applications

• Reduce water bill if on city water

• Reduce crop loss from disease

• Reduce labor costs

Automated Irrigation Systems!

Common Sense InvestmentsIncrease number / use of HAF Fans

Purchase Aspirated Sensors

Reduce In & Out traffic in the greenhouse

Bring greenhouse on-line only when needed

Use lighting to speed up crop production