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Assessing and addressing the impact of warmer autumns on the success
of grain cooling
Dean Cook
Science Strategy team
Grain Cooling
• Grain is ventilated at low-volume rate of 10m3/h/t
• Cooling must be – – fast enough to prevent insects
breeding; and temperature as low as to cause death
– Part of an integrated grain storage strategy in conjunction with drying, hygiene measures and monitoring
As a rule of thumb…….
• Cool to below 15°C within 2 weeks to prevent the saw-toothed grain beetle breeding;
• to below 10°C within a further 2 months to prevent the grain weevil breeding;
• to below 5°C by winter (xmas) to prevent mites breeding and kill insects.
Cooling targets for UK stores using low volume aeration at 10 m3/tonne/hr
Cooling starts on 1 J ul 1 Aug 1 Sep 1 Oct
Latest 15°C 16 J ul 17 Aug 12 Sep 8 Oct
date to 10°C 29 Sep 9 Oct 14 Oct 9 Nov
cool to 5°C 8 Dec 8 Dec 9 Dec 1 J an
(After – Armitage et al., 1991)
Has cooling become more difficult? – climate change
• Climate change will bring; Earlier, hotter harvests
Shorter milder winters
Extreme weather events
• Issues for cooling? High harvested temperatures
Fewer “windows” of cold night time air available
Challenge to meet targets; speed and temperature achieved
Comparison of mean monthly temperatures from 1961 to the present day.
0
5
10
15
20
25
J F M A M J J A S O N D
1990199119921993199419951996199719981999200020012002200320042005200620071961/90
(Source: Manley, 1974; Parker et al., 1992 – updated by the Hadley Centre for Climate Prediction and Research, Met. Office, Berkshire, UK.)
Minimum temperatures for the period immediately after harvest.
0
2
4
6
8
10
12
14
16
18
J A S O
199019911992199319941995199619971998199920002001200220032004200520062007
Target 1.
Target 2.
0
2
4
6
8
10
12
14
16
18
J A S O
199019911992199319941995199619971998199920002001200220032004200520062007
Target 1.
Target 2.
Target 1.
Target 2.
(Source: Manley, 1974; Parker et al., 1992 – updated by the Hadley Centre for Climate Prediction and Research, Met. Office, Berkshire, UK.)
Adaptation to climate change – demonstration project
Objectives – “How well are we doing?”“How can we do things better?”
• Measure on-farm cooling profiles in grain stores on 15 farms distributed throughout the UK from harvest 2007
• To compare the performance of automated differential fan control with manual control at 3 sites using identical paired stores
• To illustrate potential problems and “best practice”
Part 1. Efficient control – using differential thermostats
Differential thermostats
Temperature probe inserted into grain
Temperature sensor at ambient
Feedback to fan control
Temperature probe inserted into grain
Temperature sensor at ambient
Feedback to fan control
Advantages of differential thermostats; trials work, East Lincolnshire 1991.
0
5
10
15
20
25
1 3 5 7 9 11 13 15Weeks storage
Tem
pe
ratu
re °
C
Ambient
Automated store
Manually controlled store
SEPTEMBER DECEMBER
[Auto-control using a 4°C differential in conjunction with time clock (20.00-07.30, night time only) Vs manual control.]
Trial detail – differential thermostats vs manual control.
Focusing on 2 sites -
Site 1 - • Farm site, Darlington
• 700t bulk of wheat at 14.5%mc
• Cooled with pedestals at recommended spacing etc.
• Bulk divided into virtual halveshalf bulk controlled by 2°C differentialhalf bulk controlled by manual operation of fans
Darlington trial setup
4.5 – 6 m spacing between pedestals
Small pedestal/fan to deal with corner
Door
Leading edge of heap
PC running STORECHECK
Single fan between 2 –manual control
Single fan between 2 –auto control
= pedestals = sensors °C
123
456
21
3
456
Zone 1Zone 2
4.5 – 6 m spacing between pedestals
Small pedestal/fan to deal with corner
Door
Leading edge of heap
PC running STORECHECK
Single fan between 2 –manual control
Single fan between 2 –auto control
= pedestals = sensors °C
123
456
21
3
456
Zone 1Zone 2
Site 1 – Results; Temperatures at Darlington site and progress against cooling targets
0.0
5.0
10.0
15.0
20.0
7-Sep 17-Sep 27-Sep 7-Oct 17-Oct 27-Oct 6-Nov 16-Nov 26-Nov 6-Dec 16-Dec
Date
Tem
pera
ture
°C
Auto (mean)
Manual (mean)
Ambient (minimum)
15°C Target due 18-Sep
5°C Target due 15-Dec
10°C Target due 20-Oct
Site 1 – Results; Cumulative fan hours run
0
200
400
600
800
1000
1200
1400
15-Sep 25-Sep 05-Oct 15-Oct 25-Oct 04-Nov 14-Nov 24-Nov 04-Dec 14-Dec
Date
No
. of
ho
urs
blo
wn
Manual
AutoUp to 40% energy saving!
Comparison of insect control costs
PROCESS COST FUNCTIONS
Fumigation 150-200p/t - Disinfests
Bulk insecticide admixture 50-75p/t - Prevents and disinfests
Cooling (manually) 50 p/t - Prevents mc Cooling (automatic) 29 p/t movement
- Prevents infestation - Preserves quality - Disinfests over a
season
Trial detail – differential thermostats vs manual control.
Focusing on 2 sites -
Site 2 - • Co-operative store, Cambridgeshire
• Two 6000t silos of wheat at 14-15%mc
• Cooled with upward aeration systemOne silo controlled by 4°C differentialOne silo controlled by manual operation of fans
Site 2 – Results; Temperatures at Cambridgeshire site and progress against cooling targets
Site 2 –Results; Daily spot temperatures (8am) at Cambridge site
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0
5
10
15
20
05-Oct 20-Oct 04-Nov 19-Nov 04-Dec 19-Dec 03-Jan
Date
Tem
per
ature
°C
Ambient
auto bin (D2)manual bin (D4)
1 2
Hours run1. (2-Nov)Auto; 98Manual; 83
2. (4-Dec)Auto; 142Manual; 155
3. (7-Jan)Auto; 156Manual; 236
3
10°C Target due 14-Oct
5°C Target due 9-Dec
Site 2 –Results; Daily spot temperatures (8am) at Cambridge site
-5
0
5
10
15
20
05-Oct 20-Oct 04-Nov 19-Nov 04-Dec 19-Dec 03-Jan
Date
Tem
per
ature
°C
Ambient
auto bin (D2)manual bin (D4)
1 2
Hours run1. (2-Nov)Auto; 98Manual; 83
2. (4-Dec)Auto; 142Manual; 155
3. (7-Jan)Auto; 156Manual; 236
3
10°C Target due 14-Oct
5°C Target due 9-Dec
Part 2. Monitoring exercise – how well are growers doing?
Monitoring exercise overview
iButtons monitoring ambient and fan temperature
Results – monitoring 12 sites across the country
Location Air flowP=PedestalU=Under-floor
Differential Target (oC)
Target met
Best performing
Berwickshire ~10m3/t/hP
No
15105
On time1 week early1 week early
Worst performing
Suffolk ~10m3/t/hU
No
15105
10 weeks lateNot metNot met
• Only 1 site achieved the 15°C target on time• 3 sites achieved the 10°C target on time• 3 sites achieved the target of 5°C on time• 11 stores cooled to 10°C• Only 4 stores cooled to 5°C and below
Five day running mean of ambient temperatures at monitoring locations
Oxfordshire – why stop cooling?
Leicestershire – only cooled on 2 occasions
Lincolnshire – the importance of the correct differential
Part 3. What about the future?
David Bruce Consulting Ltd
Weather data – UKCP09
Weather Generator of UKCP09 hourly weather
Assumptions• Time into future, in 30yr windows. 2020-2049• Emissions scenario. High• ‘Percentile’ is probability of change being as
large as embodied in the data:– 90% (‘very likely’)– 50% (‘as likely as not’)
• Control ‘historical’ data. 1960-1989• Location: Odiham, Hants
Cooling parameters
• Strategy - diffstat control set at 4oC• Sensor at 0.5m depth• 4m bed, 14.5% mc, 25oC, 10 m3/h.t, start 20
Aug• Target temperature 5oC by end December• Also cooled to end February with the same
target of 5oC
Summary of climate change results
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6
7
8
9
10
11
Control(historic)
90% likely 50% likely
Climate change scenario
Tem
per
atu
re,
oC
Target temperature for cooling
88%
61%
38%
Conclusions
• Not all storekeepers are hitting their cooling targets
• Need to continue to improve operator practice
• Differential thermostats can help you achieve cooling targets and can save up to 40% energy-use and running costs
• Future climate change may impact on cooling targets but……will still be able to control insect pests
We would like to thank…….
Participating stores and in particular, Stuart Vernon (Grower, Country Durham), Andrew Ruff and Philip Darke (Camgrain) who took part in the differential control trials.
The work was funded by – Warwick HRI's Defra-funded Innovation network for
adapting agriculture to climate change. Defra through the Sustainable Arable LINK programme
Thank you for listening!