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Greening the greenhouse:general considerations
Gerard Bot
Wageningen UR Greenhouse Horticulture
Greening the Greenhouse; April 2, 2008
Trends in European HorticultureIncrease of scale partner in the market chain
Greening the Greenhouse; April 2, 2008
Introduction
Improved control crop growth factorsproduction : quality + quantity
Year round crop production: labour + market
Sustainability: CPC, water, materials, energybottleneck: energy consumption Licence to produce
Licence to deliver
Energy consumption in European greenhouses
1900 MJm-2
(45 l oil m-
2)
1500 MJm-2
(35 l oil m-
2)
500 MJm-2
(12 l oil m-
2)Greening the Greenhouse; April 2, 2008
Amsterdam
0
150
300
450
600
750
Cyprus
Spain
Egypt
Greece
Israel
Italy
Palestina
Average Mediteranean
Netherlands
Tomato Cucumber Sweet pepper
yield (ton/ha)
Greening the Greenhouse; April 2, 2008
Yield in European greenhouses
Introduction
Greening the Greenhouse; April 2, 2008
objectives for Northern and Southern regions
Year round:
- maximize solar radiation (crop production!)
- minimize energy consumption
Hot periods:
- energy efficient cooling to reduce high temperatures
Of course grower needs:
- profitable crop production
Greening the greenhouse: energy saving properties: low heat loss:
greenhouse cover insulation
control: climate settings and control strategy: temperature + humidity + CO2
winter: heating and ventilation; summer: efficient cooling
conversion of primary energy to heat: the “engine” of the greenhouse: boiler, cogeneration, heat pump, fuel cell, …
combined with high light transmission: crop production + solar energy in
From a systems point of view:
coverk-value (W/m2K)
single glass 5.7
Double or 1+screen 3.0
triple or 2+screen 2.3
HR++* 1.6
Vacuum glas* 1.0
0
20
40
60
80
100
0 1 2 3 4 5 6
k (W/m2K)
Rel. Econs (%)
boiler
Properties: cover insulation and energy consumption
Greening the Greenhouse; April 2, 2008
coverk-value (W/m2K)
single glass 5.7
Double or 1+screen 3.0
triple or 2+screen 2.3
HR++* 1.6
Vacuum glas* 1.0
0
20
40
60
80
100
0 1 2 3 4 5 6
k (W/m2K)
Rel. Econs (%)
boiler
properties plus energy friendly control
about 20 % improvement possible maintaining optimal crop production
Greening the Greenhouse; April 2, 2008
heat-demand
energy in:
boiler
Also changing the “engine”
100
heat demandenergy in:
work
HeatPump
energy
reservoir
100
100
100
COP=4
25
75
25 work (electricity) needs 60 primary energy so 40% energy saving
Greening the Greenhouse; April 2, 2008
properties, control and other “engine”
Properties: Reduction of energy losses: insulation Decreasing k-value (W/m2K):
Thermal screens Double or triple cover (glass, plastic film) Gas filled space between glass layers Vacuum space between glass layers
Reduction of thermal radiation loss: Low TIR emission coatings
Bottleneck: Light transmission
Greening the Greenhouse; April 2, 2008
Properties: improved light transmission
geometry of the material V structure: material Micro V: surface
anti-reflection coating: +6%
cleaning!
Principle: multiple reflection increases light transmission
25 mm
25 mmLexan ZigZagLexan ZigZagTMTM
Greening the Greenhouse; April 2, 2008
Energy friendly control
aim: optimal crop production
Greening the Greenhouse; April 2, 2008
grower holds the control-wheel
estimated risks with humidity control
crop dependent
crop oriented research
Engine: heat pump and energy reservoir
contains sufficient amount of energy in winter
Greening the Greenhouse; April 2, 2008
to be filled in summer: exploiting excess solar energy
Large capacity, 10 l oil eq per m2: 10 m3 water/m2 with ΔT = 10K or 2000 kg PCM /m2
Physically only possible in the soil: Aquifer or VSHE
emptying cold aquifer (greenhouse is cooled)
filling warm aquifer
17 oC 7 oC
heat exchanger
Aquifer: Summer period: excess heat
Aquifer: Winter period
17 oC 7 oC
heat
pump
heat exchanger
emptying warm aquifer: greenhouse is heated filling cold aquifer
Seasonal storage
Aquifer: 2 wells at different temperature specific geological conditions
Vertical Soil Heat Exchanger: passive storage via boreholes
not available at TLR
Greening the Greenhouse; April 2, 2008
Generating electricity Electricity plant: 100% fuel energy in, 42% electric energy, useful 48% reject heat, lost
By exploiting reject heat: 30% energy (CO2) saving Bottleneck: centralised electr production
greenhouses Holland 2000MW installed40% of greenhouse area
decentralise ep: local exploitation reject heat:
Greening the Greenhouse; April 2, 2008
Conclusions
Greenhouse horticulture is vigorous in N-W Europe
Greening the Greenhouse; April 2, 2008
Energy is bottleneck in sustainability
Energy saving via greenhouse properties, climate control and energy conversion
Conclusions
Greening the Greenhouse; April 2, 2008
Greenhouse properties: - insulation - light transmission
Climate control: interaction T and RH controlgrowers tool to control productioncrop dependent: quantity and qualitygrowers try to avoid risks (disease control)
Energy conversion: - boiler with condensor - heat pump/seasonal storage - cogeneration
Thank you for your
attention
Greening the Greenhouse; April 2, 2008
Introduction Sustainable greenhouses Seasonal energy storage To be realised conclusions
Greening the Greenhouse; April 2, 2008
Energy demand?
demand for energy carriers like oil, gas, coal, etc??
in principle demand for
- mechanical work, both at fixed locations and mobile - heat for processing and climate conditioning - lighting (included in mech work) - communication/info-tainment (same)
Greening the Greenhouse; April 2, 2008
Demand for mechanicalwork versus heat?
energy demand in various sectors
MWU HU
• transport 20% (efficiency 25%) 5 -• industry 40% (28% raw materials+heat>100oC) 8 (electr) 4• domestic 20% 4 (electr) 16• remainder 20% 7 (electr) 13
total excl transport 19 (electr) 33
domestic ~ 20%
transport ~ 20%
industry~ 40%
remainder ~ 20%
Estimation:
Mech Work Units (MWU)
and Heat Units (HU)
First step to sustainability: energy savingGreening the Greenhouse; April 2, 2008
Generating electricity Electricity plant: 100% fuel energy in, 42% electric energy, usefull 48% reject heat, lost
By exploiting reject heat: 30% energy (CO2) saving
Bottleneck: centralised el production
greenhouses Holland 2000MW installed40% of greenhouse area
decentralise ep: local exploitation reject heat: 19 units electricity covers 19 units heat
Greening the Greenhouse; April 2, 2008
high
evaporatorlowcondensorhighCarnot T
TT )()(
5.0, cwithc carnotpraktical
Heat Pump:
Energy targets (Netherlands 2020: greenhouses
without fossil fuel)
1980 1990 2000 2010
20
40
60
80
100
target 2000 (50)
target 2010 (35)
2020
target 2020 (0)
Greening the Greenhouse; April 2, 2008
Greening the Greenhouse; April 2, 2008