PSI Bulletin: December 2024
Merry Christmas to All Our Subscribers!
No. 12/24 SUBSCRIBER EDITION: please go to potatostorageinsight.com/subscribe to sign up as a Synopsis subscriber.
Dear Subscriber,
It seems amazing where the time has gone, but the end of the calendar year is upon us again as I prepare this, your December edition of Synopsis.
I would like to thank you for your continued support as a reader of this bulletin and wish you a Merry Christmas and a Happy New Year.
Technically, potato store managers don't really get time off at this time of year as the potato crop is in continual need of attention. This is particularly the case for late-lifted material where keeping quality is reported as being marginal at best.
Nevertheless, I am aware that many of you do try to take your foot off the gas for a well-earned break. The key, of course, is to do this is a managed way so that there are no surprises when you're back up to speed in the New Year.
Routine assessment of store conditions is a good way to minimise risk, with detailed temperature and sprouting checks at no less than monthly intervals, preferably less. At this time of year, changing climatic conditions can trigger problems such as condensation - see below for more information. If there are already rots present, it doesn't need a lot of free moisture to create an environment that is very well suited to those rots spreading. So please make your judgment about that Christmas break wisely...
PSI activity
Adrian Cunnington has recently presented at a workshop on storage at the pre-Christmas CUPGRA conference, focusing on energy management. Some of his slides form the basis of our Technical Insight feature this month.
Regular readers will recall that we launched details of our two-day residential store managers' course, that will be held on Tuesday 4th and Wednesday 5th March 2025 at the Greetham Valley Hotel & Conference Centre near Oakham, Rutland, in this publication just last month. I am delighted to report that, in the intervening 3½ weeks, the course has been completely booked out, despite extending the number of places from 20 to 25. Thank you to all those who have committed their support.
Best practice
Condensation, condensation, condensation
A good quality, well-sealed potato store will naturally create a high humidity environment of its own. This is because we are storing many, many 'micro-humidifiers' all in one place. They're called potatoes!
The potato is 75 to 80% water and even with a fully set skin, it will gradually lose moisture to the environment around it, mostly through evaporation from the skin. As the humidity in the store builds up, the store becomes increasingly at risk from condensation. Only relatively small changes in temperature are needed to push the environment past saturation. If this happens, free moisture is deposited on the crop or, sometimes, on the frame of the building.
In either case, the presence of free moisture can put the crop at risk from disease, sprouting - or both!
In processing stores, there is often a high risk of condensation in the roof space. As the air above the crop loses heat, for example in a cold spell, it’s capacity to carry moisture is reduced so it can hit dewpoint on the inside of the roof and this will then drip onto the crop. To combat this problem, such stores are often fitted with roof space heating. this is usually electrically heated and sometimes the air is distributed using collapsible polythene ducting.
This works as, by warming the air above the crop slightly, it is possible to increase the moisture carrying capacity of the air - ie reduce the humidity away from 100%.
A further risk of condensation comes from air leakage. If warm, moist air from outside the store leaks into the building, it could readily condense on cooler potatoes inside the store. This can be a particular issue if fresh air ventilation is needed in a store to manage CO2 for example. Normally, it is possible to limit the ingress of external air to some degree to allow it to be blended gradually with recirculated air in order to avoid sharp changes in temperature.
The key in store management is to identify when there is a risk of condensation and to check the crop status accordingly. but it is far better to predict the risk and to take action to prevent free moisture deposition rather than have to correct the problem after it has occurred.
Corrective measures deployed at this time of year might also include using additional localised heat in a cold store corner or the addition of fans to keep air moving and reduce the risk of moisture dropping out.
If using temporary equipment, always be careful to ensure electrical supplies are protected with residual current detection (RCD) to keep them safe. It goes without saying that the fact that you are trying to alleviate the risk of condensation means that there is a higher chance of electrical shock in these circumstances.
Technical insight
Energy management presentation at CUPGRA workshop
At the recent CUPGRA conference, I was involved in a workshop with Professor Chris Bishop of University of Lincoln, who also presented in the session on heat exchangers for use in warm climatic conditions.
My contribution to the workshop was on energy management. This isn't the first time I have touched on this subject (we worked on it over two major projects at Sutton Bridge between 2004 and 2014) but I think some of the data bears revisiting as the rate of uptake of this technology in potato storage still remains far too low given its importance as the major variable cost in storage. So here goes....
There's a huge amount of energy used to drive potatoes and to keep potatoes stores at the right temperature. In general terms, far too little emphasis is placed on measuring usage and managing energy consumption.
There is some good quality energy control and monitoring equipment available. And the payback on this is alarmingly short so the chances are, whatever you do now, you can upgrade to something more informative and save money.
Energy consumption follows seasonal trends Like the ones you can see in the graph below. Generally it's a U-shaped curve across the winter months but this data is from an AHDB survey of 4 commercial stores and you can see they all have slightly different patterns of use.
To get a good comparison across multiple stores. It is. Important to try to translate all of the data. To a common unit. Electricity is paid for in kilowatt hours. Potatoes are paid for in tonnes. So kWh per tonne is a good starting point. The only problem with this is that storage periods tend to vary significantly. So it is better to standardise the unit to kWh per tonne per day.
This next graph shows kWh per tonne in the green bars but kWh per tonne per day in the open bars, topped by the pink line. This shows how just looking at kilowatt hours per tonne can be deceiving. The lowest parts of the pink line (the most efficient stores) are on the right hand side. And they're using about 60% less electricity compared with the ones on the left!
![Energy use for 22 stores [green bars: kWh/t; pink line/open bars: kWh/t/day] (AHDB data, 2013)](https://static.wixstatic.com/media/83860c_528ae47d010f4575b0fdb0488693d7c4~mv2.jpg/v1/fill/w_633,h_368,al_c,q_80,enc_avif,quality_auto/83860c_528ae47d010f4575b0fdb0488693d7c4~mv2.jpg)
To cover some of the practicalities involved in obtaining this kind of data, here are a few pertinent points:
Smart meter technology is now quite widespread so, if there are separate supplies to stores, these can be used to automatically provide broken down consumption data on a store-by-store basis. Or you can always revert to reading the meters every month and typing the data into an Excel spreadsheet!
But many farms have electricity all running back to a central meter that does several buildings, possibly a grain drier or a grading system and the farm office all lumped together. But it is still possible to meter usage separately... The sort of kit you need to deal with this includes:
Current transformers
these can be put around feed cables without cutting into the supply to sense the electricity use by induction:
Plug in sensors
– ideal for small kit such as heaters or fans etc:
DIN rail sensors
– suitable for hard-wired components:
Once you can measure the usage it can report to individual meters, a store control box or a power management dashboard (below). Some of these systems can provide powerful management tools with full internet connectivity.
And you can tie in other components such as solar panels all on the same system so that you can monitor when free energy is available and how much you are using. For example, if the sun is shining, it could be worth overrunning the fridge by 0.1 or 0.2°C on free energy to save it running later, especially if the store is good enough to keep temperature variation tight (say 0.5-1°C max). Potatoes make pretty effective batteries in this respect!
With all of this information you can expect to start making significant savings from day one. The energy experts all agree that once you have meaningful data it becomes a very powerful management tool (no pun intended!) that will help you optimise the way you run your storage enterprise. If you have not invested in the technology yet, why not make it your New Year resolution to get yourself up to speed on energy management?
AC
Snippets
GB Potatoes leadership change
Mark Taylor stepped down as Chair of GB Potatoes at the organisation's AGM held on 12 December. His place at the helm has been taken by north Lincs grower Alex Godfrey.
PSI price increase
PSI has announced a small increase in the subscription cost of Synopsis, the first for over two years. From 1 January 2025, the price of a standard subscription will be £114 +VAT per year. Group subscriptions are also available: contact us at admin@potatostorageinsight.com for details.
DMN gets Codex clearance
The sprout suppressant 1,4-dimethylnaphthalene has recently been assigned a Codex maximum residue level (CXL) reports Potato News Today. The Codex Commission adopted a level of 15 mg/kg for the compound at its annual meeting held on 26 November 2024 in Geneva, Switzerland.
PNT reports that this newly adopted global food safety standard will foster international trade. Obtaining a CXL is considered as a critical step towards full international acceptance of 1,4DMN-treated potatoes and processed products made from treated potatoes.
PSI Christmas wordsearch
There's a bottle of fizz on offer for the subscriber finding the most 'storage relevant' words of three letters or more in our Christmas wordsearch grid. Words can be horizontal vertical or diaginal and read left to right, top to bottom or vice-versa. Send your answers as a list or a picture to adrian@potatostorageinsight.com by 17 January.
Forthcoming events
If you are hosting a potato or agricultural industry event, please send details to admin@potatostorageinsight.com. Key dates with relevance to the potato sector in the coming months in the UK include:
January 2025
Thu 9 - Fri 10 Potato Expo 25. Orlando, Florida
February 2025
Fri 7 SACAPP Potato Conference, Apex Hotel, Dundee.
Contact is kyran.maloney@sac.co.uk
March 2025
Tue 4 - Wed 5 PSI residential Store Managers' Course for 2025, Oakham, Rutland.
Two day comprehensive course that includes the option to sit the BASIS Stored Potatoes exam. Sorry - fully booked!
Please note that you, or a colleague, can subscribe to Synopsis at any time by going to potatostorageinsight.com and clicking on SUBSCRIBE. We can also now take payments by credit card. Call Adrian on +44 (0)7970 072260 if you have any questions.
Subscriptions: we issue invoices as individual subscribers reach the anniversary of their payment. A full year's subs is great value at just £9.50/month (£114 + VAT per annum), so please renew promptly. Unpaid subscriptions will be closed within 8 weeks of invoice issue. Thank you.
Synopsis is written by Adrian Cunnington and published by Potato Storage Insight Ltd., 45 Main St., Gedney Dyke, Spalding, PE12 0AJ. UK.
© Potato Storage Insight Ltd. 2024
Comments