Pro's and Con's in relation to climate, crop management and systems. Frank Kempkes. Theo Gieling, Jouke Campen, Marcel Raaphorst

Transcription

1 Semi closed greenhouse: Pro's and Con's in relation to climate, crop management and systems Theo Gieling, Jouke Campen, Marcel Raaphorst Presentation guide Greenhouse growing: Goals & Means Define goals of your crop cycle What can we do to control and improve our climate and crop growth Heating Improve CO 2 level (do we have a CO 2 source?) quality of CO 2 more important when greenhouse becomes more closed Dehumidify Reduce heat load Cool how (last option because expensive solution) Climate distribution inside the greenhouse Air distribution Conclusions 1

2 Greenhouse growing: Goals & Means Holland Top production, High quality More niche than bulk products High return on investment expected Electricity, CO 2, Gas heating, heat/cold storage, mild climate High investment opportunities High education level of staff High tech equipment is commonly used (high ridge glasshouses, computer control, Mexico average production?, fair quality? More bulk than niche? Lower investment lower return Electricity? CO 2? Gas heating? heat/cold storage? Climate?. investment opportunity? education level? High tech equipment is commonly used (high ridge glasshouses, computer control? Systems we apply are based on our local situation. Systems can t be copied but have to be adapted to the local situation Define goals of your production system High production control of greenhouse climate Good quality no blossom end rot (tomato) & more than one branch and flower (Phalaenopsis) On time delivery flowers and pot plants Decrease risk of diseases Environmental goals Water scarcity more crop per drop Energy CO 2 footprint No run off of nutrients into the environment Crop protection But this isn t a matter of just a button on our climate controller or buying a growing system. So don t shop but combine in such a way that you find the best solution for the local situation 2

3 Dutch situation High production costs Some Quality examples: 90% Euro export, Nuevo Quantity Peso x 70 16kg m 2 (tomato) On Land time delivery Euro 50 Phalaenopsis: 100 Euro /m 2 flower induction needs cooling Environmental Greenhouse goals: structure Euro /m 2 Equipment No water scarcity, as artificial but strong light, regulations boilers, by irrigation, government aquifers, heat pump, Energy heat agreement exchangers, to reduce screens energy use Euro /m 2 Nutrients strong regulations on closed growing systems by government Very high investments Crop protection flowers and pot plants zero tolerance for export Running costs By closing the greenhouse: year round control of climate increase Energy of production Euro (CO 2 /meffect), 2 reduction of energy use, reduces inlet of insects via the windows. Labor Euro /man hour Climate differences (Holland vs. Mexico global radiation 0.36 MJ/cm2 (1400 sun h) 53 o north, altitude 5 25 m 20 o north, altitude 1500 m global radiation ±0.9 MJ/cm2 (2800 sun h) 3

4 Climate differences (Holland vs. Mexico global radiation 0.36 MJ/cm2 (1400 sun h) 53 o north, altitude 5 25 m 20 o north, altitude 1500 m global radiation ±0.9 MJ/cm2 (2800 sun h) Climate differences (Holland vs. Mexico global radiation 0.36 MJ/cm2 (1400 sun h) 53 o north, altitude 5 25 m seasonal based heat / cold demand balance 20 o north, altitude 1500 m daily based heat / cold demand balance global radiation ±0.9 MJ/cm2 (2800 sun h) 4

5 Why cooling the greenhouse? optimal growing point 32 o C The variable temperature Why cooling the greenhouse? optimal growing point 32 o C 25 o C The variable temperature 5

6 Why cooling the greenhouse? optimal growing point o C The variable temperature Why cooling the greenhouse? optimal growing point o C The variable temperature 6

7 Why cooling the greenhouse? optimal growing point o C The variable temperature This CO 2 effect can only be achieved by reduction of ventilation Do you have CO 2? If not keep the vents opened What is limiting? Heat or cold demand sun radiation (MJ/m 2.month) July J spring D holland autumn mean temperature ( o C) 7

8 What is limiting? Heat or cold demand sun radiation (MJ/m 2.month) July too low radiation J spring holland Heating D autumn Cooling mean temperature ( o C) What is limiting? Heat or cold demand sun radiation (MJ/m 2.month) ensenada July puebla too low radiation J spring holland Heating D autumn almeria Cooling mean temperature ( o C) 8

9 Environmental goals: Water demand 300 kg fresh product per m 3 water 250 tomato sweet pepper Israel & Spain, field Spain, unheated plastic "parral" Israel, unheated glass growing system Spain, unheated "parral", regulated ventilation Holland, climatecontrolled Holland, as at left, with re-use of Dutch "closed" greenhouse glass, CO22 drain water enrichment increasing control of production factors Heat and cold demand Holland without heating no tomato crop from October March half of March half of September requires ventilation due to energy overload seasonal heat/cold storage March November requires energy to dehumidify More cold then heat demand (depends on closing factor: closed / semi closed Phalaenopsis (warm phase 27 o C year round heating; cold phase 20 o C without cooling between April and October not enough flowers and branches) 9

10 Heat and cool demand Mexico Huge variation in climate zones no general solution Regions with huge difference between minimum (heating) and maximum temperature (cooling) No seasonal heat / cold storage required balance daily heat & cold demand More cold then heat demand reduce heat load Dehumidification (how?) Heat and cool demand: seasonal Seasonal storage 10

11 Heat and cool demand: seasonal Heating in winter & store cold Heating 49 C 45 C heatpump 35 C gasengine 5 C 14 C 7 C warm well cold well Heat and cool demand: seasonal Recharging the storage system in summer by cooling Heat extraction 18 C Heat exchanger 16 C 8 C warm well cold well 11

12 Heat and cool demand: seasonal Lots of equipment Difficult to manage High investments (at least ±100 Euro/m nuevo Peso) Heat and cold demand: daily First try to reduce heat load with conventional means, because this is often cheaper then active cooling If this way of heat reduction is not sufficient: Which cold source is available to me? Cooling tower possible (cold nights?) Heat pump needs electricity (if available, then expensive) Is cold only used to cool or also for dehumidification? What does the heating system look like (water pipes, air heat exchanger)? Economy: Financial balance 12

13 Reduction of heat load Radiative properties of the cover A cover with high NIR reflectivity would reduce thermal load by 50% without reducing assimilation energy The ideal cover has different properties in the PAR, NIR and TIR ranges!! UV NIR(Near InfraRed) = 50% of energy 0 wavelength nm Global radiation UV PAR NIR absorption ventilators open heat stress transmission greenhouse covering Τ outside UV PAR increasing temperature heat Τ inside Τ crop photosynthesis / growth 13

14 Global radiation UV PAR NIR Reflection by NIR filter absorption Vents can be kept closed for a longer period transmission greenhouse covering CΟ 2 Τ outside UV PAR photosynthesis / growth heat Τ inside Τ crop BUT: Contribution of NIR to the heat load is smaller than we expect because of high NIR reflection of the crop (45 %) where PAR reflection is small (5%) 14

15 Reduce heat load: pro s & con s of screens and coatings Screens Reduce transmission transmission of greenhouse x transmission of screens screen = 0.75 x 0.8 = 0.6 Pick your choice from a large number of available screens Most screens are multi functional: both for shading and isolation purposes Keep in mind that especially multi functional screens reduce ventilation capacity Photo selective screen materials are available (expensive and questionable functioning) Screens on the outside of the greenhouse are more effective than inside the greenhouse photo selective coatings (chalk/ white wash) reduce NIR (in or on top of greenhouse) Cost effective Flexible (part of, or whole greenhouse) Changes Direct Radiation into Diffuse Radiation Once applied, not easily removed Almost never the ideal solution Reduce heat load: pro s & con s (roof) sprinklers Roof sprinklers or water screen (big difference) Pro s Evaporation of water uses heat from greenhouse roof, thus cooling the greenhouse air Roof temperature reaches dew point temperature (at the cost of large amounts of water) Temperature of sprinkler water less important than one may expect (Keep in mind the difference between evaporative heat and specific heat) With roof sprinklers allow energy to be harvested; Con s increases RH of the greenhouse air reduces ventilation capacity increases slightly humidity of the outside air entering the greenhouse!!! high use of water!!! Humidification of the greenhouse air (evaporative cooling) increase of ventilation efficiency good (clean) water required keep your crop dry (short running time, high pressure, high greenhouse ridge) 15

16 Ways of cooling: how to apply cold in the greenhouse Ways of cooling : Apply cold from below using air ducts 16

17 Ways of cooling: apply cold from below by decentral units Ways of cooling: apply cold from above by decentral units 17

18 Tomato: some results of closed versus open systems Temperature profile differs T( C) Gesloten Closed kas greenhouse maand gemiddelden cyclemean 01-Jun-2008 June 30-Jun Closed T( C) 25 Tijd (uren) Open kas maand gemiddelden 01-Jun-2008 T top boven day Etmaal: avg o C C T midden day Etmaal: avg o C C T low onder day Etmaal: avg o C C Open greenhouse cyclemean June Jun-2008 Open 20 T top boven day Etmaal: avg C C T midden day Etmaal: avg C C T low onder day Etmaal: avg o C C Time Tijd (uren) (hours) Growers try to reduce this difference Effect of cooling on greenhouse climate Temperature cycle average month of June Company 1 Company 2 Company 1 l below & above Company 2 p below Company 3 t below Company 4 g above Absolute Temp. difference open and closed 1 & 3 Temp. under 2 & 3 low Top cooler (company 4) no vertical temperature gradient Company 3 Company 4 T top closed T mid closed T low closed T top open T mid open T low open 18

19 Effect of cooling on greenhouse climate Humidity cycle average during July 2008 Company 1 l below & above Company 2 p below Company 3 t below Company 4 g above Company 1 Company 2 During daytime more humid in closed greenhouse Start of cooling (vents are more closed) Company 3 Company 4 VD top closed VD mid closed VD low closed VD top open VD mid open VD low open Effect of cooling on greenhouse climate CO 2 effect Company 1 below & above Company 2 below Company 3 below Company 4 above company company Variability open and closed is subject to change Company 4 despite small cooling capacity reasonable differences in CO 2 Differences are smaller than expected! company Closed company 19

20 Effect of cooling on greenhouse climate CO 2 effect in practice Calculated and realized production increase (%) Calculation takes into account that during high radiation effect is largest 2008 grower Production increase (%) calculated realized 3.4 ~ ~ ~ ~ 8 Realized production differs from calculated due to diseases, deficiencies, predators and crop treatment Interaction between cooling and climate Cooling from above Cool unit Wire less Temp. & Humidity Sensors Network At 3 heights 20

21 Interaction between cooling and climate cooling from above Temperature and humidity measured at 3 heights in the crop (at substrate level, ripening truss and top of plant) The influence of the cooler is seen in the temperature profile Temperatuur [ o C] 25-Jul Aug-2008 vpd [g/m3] Arrows show position and air flow direction of cool units Interaction between cooling and climate Temperature with air duct (company 2) 23.5 [o C] van: 02-Mar :00:00 tot: 02-Mar :00:00 Top onder Middle midden Low boven 21 Side wall Middle of greenhouse Side wall [locatie] Temperature distribution good below the crop during cooling 21

22 Interaction between cooling and climate Temperature with air duct (company 2) 18.5 [o C] van: 05-Mar :00:00 tot: 06-Mar-2008 Top onder Middle midden Low boven 16 Side wall Middle of greenhouse Side wall [locatie] Temperature distribution uneven during heating Interaction between cooling and climate example of air distribution (Theory) Bedrijf 1 onder & boven Bedrijf 2 onder Good equal distribution of air through the table in theory 22

23 Interaction between cooling and climate example of air distribution (practice) Inhomogeneous distribution through or even beside the table Conclusions (1) Cooling from below creates a vertical gradient in temperature and humidity in opposite direction compared to natural ventilated greenhouse If differences are too high lower fruit temperatures will result ripening time will increase increase of fruit load overall result: decrease of production Despite the systems, climate is still not homogenous (horizontal and vertical) Influence of the conditioning systems on the climate is minimized when windows are opened Only apply cooling from above when air is spread by fans 23

24 Conclusions (2) Potential production increase (CO 2 effect) lags behind by Lower fruit temperature (unbalanced plants) Increase of CO 2 smaller than expected Diseases show up at some companies During summer quality of Phalaenopsis will increase (more branches and flowers) Air ducts increase energy consumption During heating air ducts will just cause trouble The way growers use the system is subject to changes (we are still all learning) The control of the systems is still mainly manual Conclusions (3) What do these Dutch conclusions mean for the Mexican situation? Closed system only beneficial when CO 2 enriched inside the greenhouse Closed system should be designed for day night cycles rather than winter summer cycles Closed system are beneficial to decrease disease pressure in the greenhouse Closed system increases the water use efficiency considerably beneficial in areas with water scarcity 24

25 Gracias por su atención 25