10/16/2009                                                                              Increased awareness: save fossil e...
10/16/2009Recent years many new developments           Co generation of heat and power  Co generation heat and power  Geot...
10/16/2009                                                                               Energy harvest in summer  Energy ...
10/16/2009CO2 concentrations in closed and conventional greenhouse                                                        ...
10/16/2009 Semi closed greenhouse                                                    How to reduce energy use?            ...
10/16/2009Temperature integration                                                                                         ...
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Energy Friendly Greenhouse Production


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Energy Friendly Greenhouse Production

  1. 1. 10/16/2009 Increased awareness: save fossil energyCrop production in low energygreenhousesLeo MarcelisAims for energy saving (Reduction of CO2 emission; Need for energy saving in greenhouse horticulturefrom 1990 to 2020) Energy costs: 15 30% of a grower Glasshouses: 48% Greenhouses: 10% of national gas consumption Energy for heating, reducing air humidity, lighting, CO2 Netherlands: 30% € 0.45 € 0.40 EU: 20% € 0.35 € 0.30 Gas price (€) € 0.25 € 0.20 € 0.15 € 0.10 € 0.05 €- 2-1-2003 2-1-2004 1-1-2005 1-1-2006 1-1-2007 1-1-2008 31-12- 2008 Energiebalance tomato (reference) How to reduce energy use? Solar radiation roof screens Lower temperature wall Temperature integration (within 24 h, several days) Heat 2 Postponing starting date Heat 1 Control of air humidity Cultivar choice Floor 177 MJ m 2` yr 1 Less lighting Bron: T. Dueck 1
  2. 2. 10/16/2009Recent years many new developments Co generation of heat and power Co generation heat and power Geothermal heat Very efficient use of heat, electricity and CO2 Electricity producing greenhouse (ELKAS) LED lighting (semi )closed greenhouseGeothermal heat ELKAS: Electricity producing greenhouseEnergy saving with LED lights? Greenhouse energy use Solar radiation provides much more energy than needed on annual basis, however …. Provided in summer; needed in winter Problem of timing Solution: closed greenhouse! 2
  3. 3. 10/16/2009 Energy harvest in summer Energy storage in aquifers Harvest solar energy in summer; use it in winter Proven technology, but new in horticulture More than 160 applications in the Netherlands (office buildings, hospitals, apartment blocks) Aquifer = layer of porous sand holding water between 2 clay layers Aquifers 5 8oC 16 18oC (porous sand between 2 clay layers)Use energy from aquifer in winter Features of a closed greenhouse Active cooling and dehumidification v Heat Pump Heat storage in summer in aquifers Use of stored heat in winter Aquifers 5 8oC 16 18oC (porous sand between 2 clay layers) Advantages of a closed greenhouse Closed or semi closed greenhouse Reduced energy consumption & CO2 emission (about 30% less fossil fuel needed) Reduction in biocide use Disadvantage of closed greenhouse High costs Reduction in water use Higher yields, because of Semi closed greenhouse is more realistic * High CO2 in summer Less cooling capacity; allow some window opening * Air movement (boundary layer ) * Higher light transmissivity (no ventilators in roof) 3
  4. 4. 10/16/2009CO2 concentrations in closed and conventional greenhouse Simulated (lines) and measured tomato yield (closed symbols = closed greenhouse) Closed symbol is closed greenhouse, open symbol is control 60 1800 CO2 concentration (ppm) 50 1500 Yield (kg/m2) 40 1200 30 900 20 600 10 300 0 0 0 30 60 90 120 150 180 210 240 270 0 10 20 30 40 50 60 Day number of the year Week number after planting Both in measurements and simulation 16% higher yield in High values in summer ! closed greenhouse Cooling from underneath Cooling from below: bigger tomato fruits sunny weather: 5˚C cooler under crop than above 140 130 Above Fruit size (g) 120 Air temperature (˚C) Above boven 110 Below onder 100 open Open 90 Below 80 15 20 25 30 35 40 Week number Time (hour) Bron: Dieleman et al Bron: Dieleman et al Higher air humidity in semi closed greenhouse Temperature on a sunny day (summer) Open house: plant temperature lower than air Closed house: plant temperature higher than air Open house 6 Vapour deficit (g/m3) Semi-closed house 35 4 30 Temperature (oC) Open: air Open: crop 2 25 Closed: air closed: crop 20 0 1:00 5:00 9:00 13:00 17:00 21:00 15 0:00 6:00 12:00 18:00 0:00 Time (hour) Time of day Bron: Dieleman et al Bron: Dieleman et al 4
  5. 5. 10/16/2009 Semi closed greenhouse How to reduce energy use? screens Lower temperature Semi closed rather than closed greenhouse. Temperature integration (within 24 h, several days) Energy saving of up to 30% Postponing starting date Increase in crop yield: 20% desired Control of air humidity Economics: investment is high Cultivar choice Less lightingHow to save energy at a nursery with high Temperatureintensity lighting and co-generation? Most important factor for energy use (75 90% when no lights) Energy use depends on : Most instances surplus of heat Heating set point Hardly any saving through temperaure or humidity control Temperature integration If heat buffer is empty, let temperature drop at night! Isolation greenhouse (isolation value, window opening, screen) Outside temperature, wind, radiation lossEnergiebalance tomato (temp. setpoint 2oC lower) Temperature integration Solar radiation roof Crop often responds to long term average wall temperature, rather than instantaneous values Heat 2 Heat 1 Make use of flexibility of the plant Automatic by program of climate computer By hand Floor 31 MJ m 2 Yield: 3% Gas use: 15.5% Bron: T. Dueck 5
  6. 6. 10/16/2009Temperature integration Temperature integration (TI) within 24h Temperature greenhouse air Within 24 h TI sunny day reference Two situations: Let the sun heat greenhouse during the day (for free). Less heating at night Day time: less heating while heating at night when closed screen setpoint Several day Sun rise Sun set Day with much wind and less sun: accept lower greenhouse Energy saving: lower temperature at night (heating) temperature: to be compensated later (not needed always!) ; Independent of outside temperature higher temperature during day (windows closed) Additional advantage of closing windowus: higher CO2 concentrationTemperature integration within 24h in sweet pepper Conclusions Optimal: same average temp.; fluctuation 16 30oC during daytime less ventilation, at night less heating 300 Dry mass fruits (g/plant) 200 optimaal By a combination of factors: energy saving of 50% standaard is possible with the same yield 100 ` 0 5 10 15 20 25 30 Time (weeks) 2.5 m3 gas saved; same fruit set and production Bron: A. Dieleman. Thank you for your attention© Wageningen UR 6