Low Carbon Technologies for Greenhouse Horticulture What are the options for Growers in the UK?

©FEC Services Ltd 2007

Low Carbon Technologies for Greenhouse Horticulture

What are the options for Growers in the UK?

Chris Plackett FEC Services Ltd


Topics• Results from two

recent HDC projects

• PC256– A review of closed

greenhouse technology

• PC265– Biomass heating

systems


Closed Greenhouse Technologies• Interesting concepts

• Complex engineering solutions• Impressive headlines

• Commercially, where are they now?– Do they offer

anything to growers in the UK?


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?


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


How Does ‘Semi Closed’ Work?


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


Fan & Duct Systems


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


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


Project Status

• Installation complete• Work ongoing

– 4 year project• Look out for results

– All of the normal HDC communications routes

– Website for HDC members


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


What about biomass heating?• Options?

– Wood pellets– Miscanthus– Wood chip– Straw


One Potential Problem

• CO2 enrichment – not currently commercially

available• What impact does this

have on boiler utilisation?

• What are the alternatives?


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


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


Heat Storage

• Helps to maximise boiler use• Connect as ‘open buffer’

• What size?


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


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


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

/ m2

0

50

100

150

200

250

300

350

400

kWh

/ m2

Biomass Heat Extra Heat Total Biomass Heat Total extra Heat

• No CO2 demand

• 500kW, 200m3 – 84% biomass


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 2Week

tonn

es/H

a/w

eek

• CO2 demand – 423 tonnes/Ha p.a.


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

/ m2

0

50

100

150

200

250

300

kWh

/ m2

Biomass Heat Extra heat Heat for CO2 Total biomass Heat Total extra Heat


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 50Week

t/Ha/

wee

k


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.


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


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


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

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Low Carbon Technologies for Greenhouse Horticulture What are the options for Growers in the UK?