Are you a FARMER growing CEREALS?
Is your FARM electrical OFF-GRID?
Conservation of the Grain.
The grains continue to live in the silo, after harvest. Like any living organism, the grains breathe, gradually increasing the temperature inside the silo, especially if the humidity is high.
High temperature and humidity increases metabolic activity, causing weight loss, lower quality and more attack by fungi and insects, resulting in a shorter time of storage. Therefore you must do everything possible to reduce the humidity and temperature in the silo.
Regarding TEMPERATURES, the ideal would be to be as low as possible to reduce the metabolism of the grains and weight loss. It is important to fall below 25ºC (77ºF) for not stimulate the growth of fungi and insects, and being his ideal below 16ºC (61ºF). To cool a silo with renewable energy, we will set a target below 20°C (68ºF).
Fans with solar photovoltaic
But .. if you are isolated and have no main power to connect the fans, are you going to resign a proper conservation of your harvested cereal?
The solution I propose is to put a set of photovoltaic modules connected to two fans. Let’s see how:
Calculation of fans for drying with natural air.
The first objective is to reduce the humidity to <15%. The drying of grain in a silo with natural air (NA) is based on passing a high flow of air to remove moisture. The air flow required for NA drying is 1 to 2 m 3 of air per minute per ton of grain.
(This is true in relatively warm and dry climates, where the collection of grain can be relatively dry. If the grain is too wet or if ambient air is very humid, the time required to reduce the humidity could above 60 days. In this case, the best will be to make a preliminary drying process, which I will explain another day).
The proposed system comprises an impulsion blower in the lower zone and another exhaust fan at the top of the silo. Obviously the silo should have a flat perforated bottom and aeration pipes which facilitate the passage of injected air from below and passing through the entire mass of grain. Add a fan on top of the silo will help reduce the residual moisture in the upper zone.
Since evacuate moisture will be held in dry spring or summer seasons, air temperatures will be more elevated, which help to dry moisture grain at reasonable times.
Calculation of cooling fans for aeration.
After reducing the humidity, the second objective is to cool the grain mass below 20°C (68ºF) for long-term conservation. Use the same fans (lower impulsion and higher extraction) but with 10 times lower flow rates than in the case of drying, ie 0.1 to 0.2 m3 per minute per stored ton. For a silo with 1000 ton of grain, we would need to provide a fan 100 to 200 m3 per minute, taking into account the air resistance passing through the grains.
Since your intention at this second stage is to cool, place the fans in the shaded area of the silo to vacuum the colder ambient air. It will help to cool gradually the grains that the aeration phase is prolonged for many months during the fall and winter, with cool ambience air.
In the next post # 2 of this series I will explain how to place the photovoltaic modules in the silo, how to connect the fans and how to manage electrical energy from renewable sources for the entire farm.
For now, how do you see the idea? We are interested in your qualified opinions.
LINKS: The information on the processes of drying and aeration of grain has been extracted from the site www.ENGORMIX.com , excellent professional farming platform. Giving you high on it you can access the following articles, very well written: