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©FEC Services Ltd 2007
Low Carbon Technologies for Greenhouse Horticulture
What are the options for Growers in the UK?
Chris Plackett
FEC Services Ltd
©FEC Services Ltd 2007
Topics• Results from two
recent HDC projects
• PC256– A review of closed
greenhouse technology
• PC265– Biomass heating
systems
©FEC Services Ltd 2007
Closed Greenhouse Technologies
• Interesting concepts• Complex engineering solutions
• Impressive headlines• Commercially, where are they now?
– Do they offer
anything to
growers in the UK?
©FEC Services Ltd 2007
Where is the technology now?
• Themato project has been a flagship– Successfully grown tomatoes
– Moved to other crops - strawberry
• Commercial focus now on ‘semi-closed’ greenhouses
– Similar advantages– Reduced investment
– Lower risk?
©FEC Services Ltd 2007
What about the UK?
• Aquifer thermal energy storage is not viable
• No other commercially attractive energy storage options currently exist
• But!– Air handling / heating technology has good
potential
©FEC Services Ltd 2007
How Does ‘Semi Closed’ Work?
©FEC Services Ltd 2007
Air Movement Technology
• The Benefits – Uniform greenhouse
conditions» temperature, humidity &
CO2
– More efficient heating?» Better response» Use low grade heat» Increased opportunities to
use alternative heat supplies
©FEC Services Ltd 2007
Fan & Duct Systems
©FEC Services Ltd 2007
New HDC Project – PC278• Adapting the Dutch approach ……
– And doing it better!– Meeting the needs of the UK grower
• R&D with a commercial installation– 1Ha Tomato Nursery
– Side by side comparison with conventional system
• Partnership between– HDC
– Mill Nursery Ltd– Industry suppliers
©FEC Services Ltd 2007
Project Objectives
• Reduce energy use & cost • Reduce CO2 emissions
• Expand the opportunities to use alternative heat sources
• Improve yield & quality• Reduce disease incidence & the
use of crop protection chemicals
©FEC Services Ltd 2007
Project Status
• Installation complete• Work ongoing
– 4 year project
• Look out for results– All of the normal HDC communications routes
– Website for HDC members
©FEC Services Ltd 2007
Summary – Sealed Greenhouses
• Not likely to be economic in the UK– Aquifer thermal storage not widely available– Long paybacks
• ‘Semi-sealed’ offers better opportunities– Air movement technology– Opportunities for ‘low grade’ heat
• A new HDC Project is investigating the potential– PC 278
©FEC Services Ltd 2007
What about biomass heating?
• Options?– Wood pellets– Miscanthus– Wood chip– Straw
©FEC Services Ltd 2007
One Potential Problem
• CO2 enrichment – not currently commercially
available• What impact does this
have on boiler utilisation?
• What are the alternatives?
©FEC Services Ltd 2007
Options for CO2 enrichment
• Pure CO2
– Not currently economic
• Biomass for winter heating only?
– Heat with biomass when CO2 demand is low
– Use mains gas to produce CO2 in summer
©FEC Services Ltd 2007
What size boiler?
• Choose the biggest possible?– Satisfy peak winter heat
demand– Low output most of the year
• Smaller boiler?– Won’t meet all of the heat
demand but…– Lower capital cost– Higher utilisation
©FEC Services Ltd 2007
Heat Storage
• Helps to maximise boiler use• Connect as ‘open buffer’
• What size?
©FEC Services Ltd 2007
Finding the answers
• Data from commercial nurseries– CO2 demand – 5 minute data– complete cropping season
• Scenarios– Low CO2 demand, moderate heat use– High CO2 demand, high heat use
©FEC Services Ltd 2007
Scenario 1
• 1 Hectare• Energy
efficient– Thermal
screen etc.
• Low CO2 user
• Ignoring the need for CO2
Boiler size (kW) Buffer size (m3)
Heat from biomass %
1,420 0 100
800 150 99.2
800 200 99.4
800 250 99.6
600 200 90.9
500 200 83.9
400 200 73.4
200 200 40.5
©FEC Services Ltd 2007
Scenario 1
0
2
4
6
8
10
12
14
16
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 2 4
Week
Wee
kly
kWh
/ m
2
0
50
100
150
200
250
300
350
400
kWh
/ m
2
Biomass Heat Extra Heat Total Biomass Heat Total extra Heat
• No CO2 demand
• 500kW, 200m3 – 84% biomass
©FEC Services Ltd 2007
Nursery 1
0
2
4
6
8
10
12
14
16
18
20
6 10 14 18 22 26 30 34 38 42 46 50 2
Week
ton
nes
/Ha/
wee
k
• CO2 demand – 423 tonnes/Ha p.a.
©FEC Services Ltd 2007
Scenario 1
• CO2 demand satisfied by mains gas
• 500kW, 200m3 – 42% biomass
0
2
4
6
8
10
12
14
16
6 10 14 18 22 26 30 34 38 42 46 50 2Week
Wee
kly
kWh
/ m
2
0
50
100
150
200
250
300
kWh
/ m
2
Biomass Heat Extra heat Heat for CO2 Total biomass Heat Total extra Heat
©FEC Services Ltd 2007
Scenario 2
• Higher energy & CO2 user• 697 tonnes CO2 /Ha p.a.• Biomass heat = 31%
0
3
6
9
12
15
18
21
24
27
30
1 5 9 13 17 21 25 29 33 37 41 46 50
Week
t/H
a/w
eek
©FEC Services Ltd 2007
Some simple economics
• Assumptions– 600kWh/m2/year heat use
– ‘Low’ CO2 demand
– 42% heat provided by biomass
• Comparative fuel costs– Mains gas 2p/kWh (60p/therm)
– Wood chip 0.7p/kWh (£25/t)
• Fuel cost saving = £32,760/Ha/year.
©FEC Services Ltd 2007
Simple economics
• 3Ha nursery– Total fuel cost saving = £98,280/year.
• Cost of 1.5MW boiler & infrastructure– £200k - £300k– 2 - 3 year pay back, ignoring O&M costs
• Economies of scale & fuel cost sensitivity are high– Gas price 1.5p/kWh, payback up to 6 yrs– Lower capital cost /MW for bigger boiler
©FEC Services Ltd 2007
Also consider
• Boiler selection– Fuel flexibility– Ease of use
• Fuel– Cost now & in the future– Reliability of supply– Ease of storage & handling
• Operation & maintenance– Labour
• Rules & regulations
©FEC Services Ltd 2007
Summary - Biomass
• Lack of CO2 enrichment is a barrier to uptake– But not a complete ‘lock out’
• The technology is not fit & forget• There are opportunities
– Do your homework– The economics are very site specific