agricultural-drying

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Grain Drying

The challenge

Drying grain and cereal crops to controlled conditions efficiently, effectively, and without taint, shrinkage or degradation.

The solution

From small scale minimally powered installations, to integration with existing systems, SVPro Grain solutions are cost effective, efficient and effective.

Smarter grain drying, for better returns

“The primary advantage of high-temperature drying is that you can harvest grain at any moisture, dry it quickly, and sell it soon after harvest without moisture discounts.” – Wheat and barley drying (UoM Extension)

“Well designed – purpose built high flow rate aeration drying silos with air flow rates of 15-20 l/s/t and higher, can dry grain from higher moisture contents… over several days and sometimes weeks depending on starting grain moisture and ambient conditions.  For aeration drying, larger fans and ducts are required… a large quantity of ambient air with low to moderate RH (relative humidity) is utilized to push drying fronts through grain. For most inland grain growing regions, fans should run for most of the day and night apart from short periods of high RH.” – DPI Qld

“Moisture content of 25 % is not uncommon in newly harvested grain in humid areas but it must be dried immediately to protect it against mould. At 14 % moisture grain can be safely stored for 2 to 3 months. For longer periods… moisture content must be reduced to 13 % or below”. – Solar Drying (Weiss)

source: WA guide to high moisture harvesting (CBH group)

System design is based on a number of factors, including the amount of moisture to be removed, the timeframe, and the volume of grain to be dried.  To ascertain preliminary system sizing, calculate the desired moisture reduction, and consequent weight reduction, for a given quantity of grain.  For example: wheat, from harvest 16.0% to finished 12.5%, 10000kg: finished weight 9600kg

Around 0.7kWh of energy is required to remove each litre of moisture.  For this example, that equates to 280 kWh.  To dry over 16 days requires 17.5 kWh/day.

Average solar insolation levels in Australia vary by season, and in wheat-belt areas often between 2-8kWh/m2/day.  We’ll assume 3kWh/m2/day, which implies a collection area of 5.8m2.

​A single SVPro module has a collection area of approximately 2m2, so three modules will be required.  Fans with a volume and back-pressure rating suited to the rates of drying and method of storage must then be selected, and ducting incorporated.  Additional options include temperature and humidity controllers, zone monitors, flow control and check valves, each of which must be matched to the system.

Drying & Aerating Stored Grain: sizing a SVPro system

Aeration is the practice of moving air through stored grain to reduce the rate of grain deterioration and prevent storage losses. Spoilage in stored grain is caused by mould growth and insect activity, which is related to the moisture content and temperature of the stored grain. Aeration greatly improves the “storability” of grain by maintaining uniform temperature throughout the storage: reducing mould development and insect activity, and preventing moisture migration.

There are two aeration approaches: cooling, and drying.  The cooling of grain through aeration requires airflow rates of only 7-14m3/h/tonne.  As air passes through the grain it collects moisture and creates a drying front, which must be forced through the volume of grain to attain drying.

Only in very dry climates with consistently low relative humidity and little risk of airborne moisture is this possible.  In most areas, dehumidified and dry air is suggested, and considered best practice.

To dry grain with aeration, airflow rates should ideally be no less than 50m3/h/tonne, and preferably more than 70m3/h/tonne.  Snap drying rates can be as high as 120m3/h/tonne.

Further information

Grain drying brochure

ADVICE: aeration for cooling and drying of grain (DPI QLD)

RESEARCH: solar drying of agricultural produce (Tiwari)

ADVICE: WA guide to high moisture harvest management, grain storage and handling (CBH Group)

RESEARCH: wheat and barley drying (Uni. of Minnesota Extension)

Coffee Drying

The challenge

Drying fresh-picked coffee beans to 11% moisture quickly and efficiently, without taint, mould or off flavours.

The solution

Modular SVPro coffee drying solutions – scaled to operation, extendable and efficient.  Can be integrated into existing drying, or stand-alone and free to run.

Smarter processing

“Some innovative grain drying methods… have been introduced into coffee drying facilities in the last few years in an effort to increase the drying capacity and the energy efficiency of conventional coffee drying installations, and at the same time to maintain high coffee quality.  From the results, the dried coffee beans were considered of excellent quality” – New technologies for drying coffee (de Sousa, Roberto)

“the solar dryer of coffee with the largest natural ventilation area… is the most energy efficient and the most appropriate to preserve the quality of coffee” – Post-harvest installation and a solar dryer of coffee (Campina Grande)

Drying of freshly harvested cherry coffee

Coffee growing along Australia’s east coast is a burgeoning industry, with current estimates of four to five times the 1000 tonne production levels recorded in 2011.  Growing as it is, the Australian industry is still a very small contributor to the annual production of ten million tonnes worldwide.

SVPro solutions are available for both dry processing, as used in the majority of countries exporting coffee, and for those more affluent countries, like Australia, that typically utilise wet processing.

Cherry coffee as harvested has a typical moisture content of around 57%, most of which is in the outer, fleshy pulp.  Within hours of harvest the pulp needs to be treated – either solar dried (dry method); or immersed, the pulp removed, and then dried.

The finished moisture content of the dried green beans, ready for roasting, is typically 11%, with the moisture content needing to be removed after initial pulp processing of up to 45%.

SVPro solutions can be applied to both wet and dry processing methods; system size, scaling and suitability for climatic conditions are key parameters of the design.

SVPro solutions comprise modular solar collectors, which dehumidify and heat the ambient air, and fan and air distribution arrays to deliver the dried and preheated air to the coffee.  Air flow rates, temperatures, relative humidity, and the desired time to complete processing all govern system design, as do a number of other factors.  Additional options include temperature and humidity controllers, zone monitors, flow control and check valves, each of which must be matched to the system.

Further information

Coffee processing brochure

RESEARCH: post-harvest installation and a solar dryer of coffee (Campina Grande)

RESEARCH: new technologies for drying coffee (de Sousa, Roberto)

Fruit Drying

The challenge

To dry or semi-dry fruit, to very specific finished moisture content, gently and efficiently, without spoilage or damage.

The solution

From small scale minimally powered installations, to integration with existing systems, SVPro Fruit dryingsolutions are cost effective, efficient and effective.

Smarter processing to improve quality and processing times

“industrial food drying practices could benefit from the use of solar thermal drying… the use of those devices could cut down labour costs and production time, thus making such productions more cost effective and rewarding” – Solar food processing (Braz)

“drying of sour cherries was carried out… with constant airflow velocity of 1 m/s. Results showed air temperatures had significant effect on drying time and organoleptic properties…  It reduced drying time up to 80% and energy saving was approximately 83% in comparison with no treatment samples” – air treatment sour cherry processing (Gazor et.al.)

Aerating and drying fruit produce: sizing a SVPro system

Drying aeration is the practice of moving air through fruit, with the intention of reducing moisture content.  When done so, for each fruit taken from and to specific moisture contents, deterioration can be prevented and produce stored for longer periods.  Spoilage losses are caused by mould growth and insect activity, which is related to the moisture content and temperature of the produce in storage.

As the fruit produce dries, the process of drying aeration greatly improves its “storability” by maintaining uniform temperature throughout the storage: reducing mould development and insect activity, and preventing moisture migration.

To dry fruit produce using aeration, airflow rates should ideally be no less than 50m3/h/tonne, and preferably more than 70m3/h/tonne.  Snap drying rates can be as high as 120m3/h/tonne, and sometime in excess of this for specific finished products.

System design is based on a number of factors, including the amount of moisture to be removed, the timeframe, and the volume of fruit to be dried.  To ascertain preliminary system sizing, calculate the desired moisture reduction, and consequent weight reduction, for a given quantity of produce.  For example:

figs, from harvest 75% to finished 26%, 1000 kg: finished weight 468 kg.

Around 0.7kWh of energy is required to remove each litre of moisture.  For this example, that equates to 760 kWh.  To dry over 12 days requires 62kWh/day.

Average solar insolation levels in Australia vary by season, and in many fruit growing and riverland areas between 2-8kWh/m2/day.  We’ll assume 3kWh/m2/day, which implies a collection area of a little over 20m2.

A single SVPro module has a collection area of approximately 2m2, so ten modules will be required.  Fans with a volume and back-pressure rating suited to the method of drying must then be selected, and ducting included.  Additional options include temperature and humidity controllers, zone monitors, flow control and check valves, each of which must be matched to the system.

Further information

RESEARCH: solar drying of ginger (Deshmukh et.al.)

Fruit drying brochure

RESEARCH: air treatment sour cherry processing (Gazor et.al.)

RESEARCH: Figs – solar food processing (Braz)

Macadamia

The challenge

To reduce shell moisture content of recently harvested macadamia nuts, for the recovery of perfect and undamaged kernels.

The solution

With outer shell moisture reduced from 25% slowly and efficiently, sufficient kernel shrinkage will permit removal without kernel damage.

Smarter processing to maximise quality

“drying rate and final moisture content of the nuts is of utmost importance to the quality of the kernels”

“the development of a good roasted flavour and prevention of off-flavours are very important aspects of macadamia processing. Too high moisture contents, storage temperatures or storage periods can result in the development of staleness or rancidity. Roasted colour is closely related to flavour and is related to cooking time and temperature” – macadamia nut processing (Weinert)

Shell drying of macadamias

Attaining the finest kernel quality in macadamias is dependent on the interaction of a number of drying conditions: relative humidity, temperature, air speed and ambient conditions.  Of those, drying airflow is amongst the most critical.

When macadamias are initially harvested, moisture contents can be as high as 25-30%, with 22-25% typical in Australia.  Without drying, such high levels of moisture content can rapidly lead to spoilage:fungal, bacterial, browning and in reduced shelf life.  It’s therefore imperative to start drying nut in shell as soon as is possible.

SVPro solutions are based on solar collectors that dehumidify and warm ambient air, which can then be driven through the harvested produce to gently and effectively dry.  The lower the rate of relative humidity, the quicker the drying; SVPro solutions regularly achieve <10% relative humidity in dry and sunny conditions.  As the macadamia nuts dry and their relative humidity decreases, so too much the incoming air remain at lower relative humidity to continue the process.

Integrated with humidity sensors and controllers, SVPro solutions can be designed to deliver drying and dehumidified air only when required, at controlled air volumes.

Fan arrays for providing drying aeration are specified according to the method of storage.  Stored in silos, strong drying is usually required within the first 24 hours to remove any transpiration and water collected during harvest.  Thereafter fans are generally required to run at lower speeds to provide gentle aeration drying.

The specification of fans, ducting, configuration and siting of SVPro solutions is tailored to each situation.  Storage conditions, particularly when stored in silos, will govern fan design; the storage depth, initial moisture levels, back pressures and local climactic conditions all play a part.

Modular and sized to suit processing volumes, SVPro solutions with integrated control systems available now.  And with academic research identifying the link between kernel dryness by airdrying and roasting colour, flavour and quality, can you afford not to manage harvest processing without SVPro?

Additional information

Macadamia brochure

FACT SHEET: drying macadamia nut-in-shell (Aust, Macadamia Society)

RESEARCH: macadamia nut processing – air drying extract (Weinert)

ADVICE: macadamia integrated orchard management practice guide 2016 (HIA, AMS, DPI NSW)

Hazelnut Drying

The challenge

Slow and gentle shell drying at very moderate temperatures, ensuring clean separation of the kernel.

The solution

With outer shell moisture reduced to 6-8% over 7-10 days, an SVPro Hazelnut solution will efficiently and effectively dry the shell to allow the kernel to be recovered without damage.

Further information
Hazelnut brochure

ADVICE: Hazelnut production (NSW DPI)

Herb Drying

The challenge

To dry culinary herbs for storage gently and efficiently, to very specific finished moisture content and without spoilage or damage.

The solution

Modular and suited from from small scale minimally powered installations, to larger commercial operations, , SVPro Herb drying solutions are cost effective, efficient and effective.

Why use solar to dry herbs?  Quality.

“a huge advantage of solar dryers is the fact that different types of fruits and vegetables can be dried. The quality of products dried in this way is excellent…due to a shorter drying process”

“higher temperature, movement of the air and lower humidity increases the rate of drying. The higher temperature deters insects and the faster drying rate reduces the risk of spoilage by microorganisms” – solar drying of agricultural produce (Tiwari)

Airflow drying of fresh herbs

Whilst fresh herbs are relatively easy to dry, the timeliness and speed with which they’re harvested, processed and shipped has a significant effect on final product quality and return.  During processing, the primary objective is to retain volatile oils, which are primarily responsible for flavour.

The report a commercial herb industry for NSW published by the RIRDC identified similar processing requirements across four common commercial crops: basil, sage, thyme, parsley, and further investigated the processing of others.  The general requirements were to minimise delays between harvest and processing, rapid drying to moisture levels of between 9-13% moisture content, monitor temperature thresholds at which individual varieties begin to lose their volatile oils, and to minimise delays between final processing and shipping.

SVPro solutions dehumidify and warm ambient air, allowing a gentle drying of freshly harvested herbs, and significantly reducing the risk of bacterial spoilage.  Designed as modular units that can be scaled as required to suit demand, systems can if required be integrated into existing drying infrastructure.

Local climatic conditions, relative humidity, varieties being processed, temperature, and the finished moisture requirements of each variety are all factors to be considered in designing each SVProinstallation.  With thermostatic and airflow control integrated as needed, SVPro solutions offer clean, green and energy efficient processing to meet exacting requirements.

Product brochure

Herb drying brochure