New covering materials – how far can we go in energy saving?A look into the future

Seminar 23rd of October 2012, Gjennestad, Norwegen

Silke Hemming

(Sensible and Latent heat by ventilation, leakage and dehumidfication)

Convection and radiation from cover

1500 MJ

Soil 150 MJ

Total energy loss: 3950 MJ

Total by ventilation: 2300 MJ

2400 MJ

Boiler or CHP

Inside

1600 MJ

Total energy in: 4000 MJ

Photosynthesis: 50 MJ

Background

2400 MJ

Boiler or CHP

Inside

1600 MJ

Total energy in: 4000 MJ

Photosynthesis: 50 MJ

Background

Energy input by solar radiation

Importance of PAR

Rule of thumb: 1% more light means 1% higher yield

Crop Yield increase at 1% more lightLettuce 0.8%Radish 1%Cucumber 0.7-1%Tomato 0.7-1%Rose 0.8-1%Chrysanthemum 0.6%Pointsettia 0.5-0.7%Ficus benjamina 0.6%

Source: Marcelis et al., 2006

Energy input by solar radiation =PAR+NIR More PAR by:

Advanced covering material●Low iron glass (+1-2%)●New plastic films ETFE (+1-3%)●Modern coatings on glass, AR (+5-8%)●New surface structures (+5-8%)

Lighter greenhouse construction (+1-5%)

Less installations (+1-3%)

Greenhouse orientation / shape

Cleaning

Energy input by solar radiation

Filtering out NIR radiation

Effects: Lower greenhouse temperature Reduction in transpiration Less humidity control needed No effect on crop production

In summer: Reduction heat load More efficient use of CO2

In winter: More energy needed

0

1

2

3

4

0 1 2 3 4

reference transpiration [kg/m2/day]

NIR

tra

nsp

ira

tion

[kg

/m2 /d

ay]

Source: Kempkes et al., 2008

(Sensible and Latent heat by ventilation, leakage and dehumidfication)

Convection and radiation from cover

1500 MJ

Soil 150 MJ

Total energy loss: 3950 MJ

Total by ventilation: 2300 MJ

Photosynthesis: 50 MJ

Background

Reduction of energy losses

Double covering materials

High insulation = less convection losses

Specific coatings (low-e) = less radiation losses

Reduction of energy losses

Double covering materials

Humidity:

Humidity is an increasing problem with increasing insulation

Decrease of condensation from 100l/m2/yr to about 10l/m2/yr

Search for alternative dehumidification system

Plant reactions:

High light transmission necessary Less CO2 available

Increase of crop temperature in top of plant

New climate control strategies possible (temperature integration, nbo minimum pipe...)

Innovative energy saving coverings

ETFE (F-Clean)

Plastic film material

Long lifetime (20 years)

Lighttransmission 93% (86%) clear film

Lichttransmission 93% (82%) diffuse film, high diffusion 75%

UV transparant

Ca. 20% Energy saving double materials

PMMA (Plexiglas Alltop)

U-value 2.5 W/m2/K

16 mm space

Lighttransmission 91% UV transparant material

Lighttranmission 86% Plexiglas Resist, UV-bloc material

Ca. 25 energy saving

Glass with modern surface treatments/coatings

New covering materials with different surface treatments/coatings

●Diffuse structure light scattering

●Low-iron increase light transmission (PAR)

●Anti-reflection increase light transmission (PAR)

●NIR-reflection decrease solar transmission (NIR)

●Low-emission decrease solar transmission (NIR), decrease heat losses

Single and double glass

Effect on energy saving, greenhouse climate (temperature, humidity, CO2), light transmission, crop response

Diffuse glass

Spring crop 2008 Kg/m2

+6.5% +9.2%

Autumn crop 2008 Kg/m2

+8.8% +9.7%

Referenceclear

Low diffusion 27%

High diffusion74%

Diffuse glass - crop

Diffuse light is positive because…

Photosynthesis

● Horizontal light distribution more equally (Hemming et al., 2006)

● Changed light penetration in crop vertically (Hemming et al., 2007)

● Diffuse light is absorbed more by middle leaf layers (Hemming et al., 2007; Dueck et al. 2009, 2012)

● Higher photosynthesis in those leaf layers (Hemming et al., 2006, 2007; Dueck et al. 2009, 2012)

● Higher dry matter in those leaves (Dueck et al. 2012)

Diffuse glass - crop

Diffuse light is positive because…

Stress:

● Lower crop temperature in upper leaves during high irradiation, higher crop temperature in lower leaves (Dueck et al., 2009)

Morphology and Development

● More generative growth and faster fruit development (Hemming et al., 2007; Dueck et al. 2009, 2012)

● Higher yield, mainly due to heavier fruits (Dueck et al. 2009, 2012)

● Faster development potplants (Hemming et al., 2007)

1% light ≠ 1% growth rule

AR glass

Spectral transmission of glass with different anti-reflection coatings from three different producers (SA, CS, GG)

Hemming et al., Greensys 2009

• Increase of PAR by AR coating Higher crop production

• Changed spectrum

• Possibilities for cooling

• Possibilities for energy saving with double materials

More PAR

Cooling

Low iron and AR glass

Light transmission of different greenhouse glasses (producer CS) with anti-reflection (AR) coatings and/or low-iron treatment

AR and low-e glass

Light transmission and energy saving of different greenhouse glasses (producer GG) with anti-reflection (AR) and/or low-emission (LOWe) coatings

Modern coatings on glass – energy & CO2

Year-round energy consumption and CO2 concentration under different greenhouse glasses calculated by KASPRO, CO2 use from boiler

33%25%

energy saving

need for external CO2 !

Summary

Increase light transmission covering

more light more production more energy less fossil fuels needed

Make light diffuse more production

Increase insulation by double coverings and low-e coatings

use AR / low-iron compensate light

less energy needed

higher humidity dehumidification needed Less CO2 available external CO2 needed

Venlow Energy Greenhouse

Double glass

Modern coatings: AR, low-e

Low u-value

Lighttransmission ~ single glass

Energy saving tomato 50-60%

New growing strategies!

Screen, active dehumidification with heat regain, no minimumpipe, temperatureintegration

Venlow Energy Greenhouse – double glass

  tp th

Single glass AR-AR 98 91

Single glass AR-Low-e 91 81

Double AR-AR-Low-e-AR 89 80

Single glass traditional 90 82

Mohammadkhani et al., 2011

Venlow Energy Greenhouse – energy use

m3 gas/year

Energy(I)

saving (II)

VenlowEnergymeasured 16.3 48% 54%VenlowEnergyestimated 15.8 49% 56%

commercial(I) 31.2

commercial (II) 35.5

Kempkes et al., 2011

VenlowEnergy Greenhouse – tomato yield

Janse et al., 2011

A look into the future

New surface structures on covering materials

●Micro V surface

●Micro pyramides

●Micro moth-eye

●Principle: multiple reflection increase light transmission?

Micro pyramides

Micro pyramides

V-grooves

Gieling et al.

Energy reduction tomato: how far can we go?

Reference: 40 m3 g.e. per m2 per year

●Later planting, shorter cultivation: 2.5 m3

●Screening strategy: 1 m3

●Double screen: 3.7 m3

●Temperature integration: 3.2 m3

●Humidity control: 2.5 m3

Reduction by new growing strategies: 27 m3 g.e. per m2 per year

●Double glass with modern coatings: 12 m3

●Heat exchangers+heat pump+aquifer: replace 10 m3 gas by solar energy, but use more electricity

Total energy needed: 11 m3 g.e. per m2 per year

Source: Poot et al., 2011 & Kempkes, 2012

Special thanks to my colleagues:Vida Mohammadkhani, Frank Kempkes, Feije de Zwart, Tom Dueck, Jan Janse, Eric Poot, Theo Gieling, Gert-Jan Swinkels et al.

Takk skal du ha!