Wednesday, 19 August 2020
A well-sealed store will decrease your energy bills, and increase the efficiency on sprout suppressants like ethylene and spearmint oil. Adrian Cunnington shares some tips for assessing and improving your potato store.
The loss of approval of CIPC will inevitably mandate change within the potato industry. For many it may mean using alternative sprout suppressants, such as mint oil, maleic hydrazide or ethylene. Others, particularly in the fresh sector, may choose to go chemical-free, moving to varieties with a longer dormancy period, or by storing at lower temperatures. For all though, optimising storage conditions and reducing operating costs are likely to be high priorities. Taking some simple steps to improve store efficiency may help to offset the potential increase in operating costs resulting from the use of more expensive sprout suppressants or greater use of refrigeration.
The first step should be creating as well-sealed a store as practically and financially feasible. No matter how well insulated a store is, insulation of the store is compromised if the structure is leaky: energy and sprout suppressant is escaping, adding cost to the business. Those familiar with applying CIPC as a hot fog will likely have seen it escaping from the store through any areas inadequately sealed. Be aware that leakage does not cease when the fogging stops; it is merely much less visible. Air and, crucially, new and invisible sprout suppressant will continue to find their way through cracks and gaps in the structure. Feeling a draught is a sure sign of air leakage, so check that personnel and roller doors seal tightly against the building and add or replace seals where necessary. Similarly, intake and exhaust louvres should close fully, with no daylight visible from inside. Replace any perished or missing rubber strips on the edge of the blades or doors to ensure a tight seal when closed.
Some areas of air leakage are not always immediately obvious to the naked eye. However, an energy efficiency assessment with a thermal imaging camera or a building pressure test may highlight otherwise unseen issues. Cracks or gaps in the structure can be identified as hotspots on a thermal image and should then be filled. A pressure test provides an assessment of the whole building, generating an AP50 value which is an indicator of how tightly the store is sealed.
Once the store is well-sealed, the next step is to insulate
Once the store is well-sealed, the next step is to insulate. While sealing prevents air moving directly between the store and the external environment, insulation is important to prevent heat transfer through the fabric of the store. Where there is no insulation, adding anything will be an improvement, but be aware that not all insulation materials are equal. It is worth looking at the specification of material properties, particularly the U-value, which is a measure of the rate of energy loss — a lower value is better. Stores with existing insulation can be upgraded, as insulation can degrade over time through absorption of moisture. Furthermore, damaged insulation will not function as intended and should be replaced; adding new insulation on top of old can also be beneficial.
Spray foam is often a simple but effective solution, especially in awkwardly shaped areas or where insulation is lacking around ducts, louvres or joints at the eaves of the building. It can be applied to existing insulation as part of a store upgrade. It could also be a solution for store operators who have previously used CIPC and are concerned about future crops being contaminated by residue left in the surface layer of the building fabric. After cleaning, adding a layer of spray foam may help to ‘lock in’ any residual CIPC.
Some people may not like the appearance of spray foam or its potential for trapping dirt. Typical alternatives are composite panels and Styrofoam board, which can give a neater finish. Composite panels are insulation boards sandwiched between two layers of metal cladding, making them slightly more robust against minor impacts than foam. Panels should fit together snugly but additional sealing may be necessary around joins with doors and louvres and at panel ends, both at the base and the eaves. They are generally suited to new stores rather than retrofitting.
Sealing leaks and adding insulation will go a long way towards improving energy efficiency but savings can also be achieved through better store control. Effective and efficient airflow is a key factor in achieving this in a potato store. If it is optimised, it should be possible in a well-sealed and well-insulated store to achieve a homogeneous climate, with similar conditions throughout. Monitoring the climate with a few temperature and CO2 sensors can be useful. The information helps not only to optimise refrigeration cycles and flushing, but also to identify potential issues early.
Carrying out any improvements, be it sealing gaps, adding insulation or installing sensors, requires time for labour and capital investment. Each store is different, and it can be difficult to predict what the financial saving and payback will be. But there will be one and, as the agriculture industry transitions to being carbon neutral, reduced energy consumption through better efficiency will be key: good for both the environment and a business’ finances.
Furthermore, it is important to remember that improving store conditions will help to create a more even storage environment. This is key to avoiding condensation and can lead to delivery of a healthier crop with reduced losses over a longer storage period, all of which should translate to a higher value when sold.
AHDB offers free Storage Network 1:1 site visits at present to assess store suitability. Thermal imaging and pressure testing services are available at extra cost. Call 01406 359419 to book