Typical Annual Energy Expenditure for a Commercial Greenhouse 10-15% 5-10% 70-80% Source: 2001 Bartok, 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 BTUs 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 Foundation Insulation 3-6% Side wall insulation 5-10% fan Fan box Insulation 1-5% Heater exhaust Peter Ling – OSU, 2006
Structural Paybacks* Install clear divider curtains = 1.2 years Double poly over leaky glass = 0.8 years Insulate North wall – 2 Ins. = 2.0 years Insulate E, W, walls – 2 Ins = 2.8 years Heat Curtains – Inside = 2.3 years Relo / Aspirate Sensors = 0.4 years Establish a north windbreak = 1.2 years Calk Cracks. Lap seals, etc. = 0.7 years * NRAES, U of Minnesota, SAF, DOE, and other sources.
Heating / Cooling System Paybacks Prevent Overlapping Controls= Immediate Repair (align) Louvers / Vents= Immediate Install Draft Baffels ( Entrances) = 1.1 Years Repair Heating Systems= Immediate Insulate Steam / Hot water pipes= 0.5 Years Improve Existing Heater Efficiency= 0.08 Years Repair Water Leaks= Immediate Calk & Weather Strip Doors= 0.7 Years Use 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
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 years Savings is $55.00 / bulb 1000 hours8000 hours
Light Emmiting Diodes LED use half the Energy of CFLs and last 10,000 hours
Glazing 50 O F60 O F70 O F Glass30,393*59,014107,342 Poly18,08936,52966,097 Poly + IR11,70124,02543,683 Poly + IR + Curtain 8,99518,25233,027 Source: 2006, A.J. Both & D.R Mears, Rutgers University * BTUs expended / hour to mainain set point temperature (10 year average) BTUs / Hr Required at Different Set Points Using Different Glazing Technology Levels.
Crop Base Temperature 64 O F61 O F58 O F Warm Season Crops – 41 0 F 15%18%21% Cool Season Crops – 45 0 F 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 Investments Increase 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