Perfect hay – despite the weather (newspaper article)
Hay drying technology has developed considerably in recent years. The Stierli family in Aristau in the Canton of Aargau in Switzerland have recently started using a new system, which provides improved feed quality with the lowest possible energy consumption thanks to innovative technology and intelligent controlling – even if there is just a short period of time available for harvesting.
Hay drying technology has developed considerably in recent years. The Stierli family in Aristau in the Canton of Aargau in Switzerland have recently started using a new plant, which provides improved feed quality with the lowest possible energy consumption thanks to innovative technology and intelligent controlling – even if there is just a short period of time available for harvesting.
«It smells really good in here», says Stefan Stierli and presents a handful of hay. It is still strikingly green and has a very pleasant “herbal tea” aroma, even though the feed was mown very early in April and was introduced with a high level of residual moisture. The Stierli family started operating a new hay drying system in March which uses technology that is still little known in Switzerland.
The system aims to provide a more efficient hay drying process based on automatic interval ventilation, which alternately ventilates two drying boxes. Another special feature of the system is that it runs on an emergency generator with combined heat usage. The Stierlis have run the farm for the last 10 years without animals and sell the manufactured hay. This makes it even more important that no compromises are made when it comes to feed quality.
The hay drying system was planned and installed by Griesser Kältetechnik [Griesser cooling technology] from Marthalen in Zurich. A large portion of the built-in technology stems from the Austrian company HSR Heutrocknung SR GmbH and was developed by company founder and agriculturalist Josef Reindl based on his own experience.
A new drying philosophy from Austria
«This technology does not have much in common with the cold ventilation systems which are the norm in Switzerland», emphasises Florian Keller, who is responsible for distribution in Switzerland: «The most important principle of our philosophy is that the hay is dried not only with air that has been warmed up but that the air is also dehumidified». Hay drying systems with air dehumidifiers are still rare in Switzerland, and, they didn’t used to have a good reputation:
People said they were too expensive, often broke down and used too much energy. Nowadays, these concerns are a thing of the past, says Keller, coming to the second principle of their philosophy:
«We don’t build the system using standard industrial components. From the ventilator to the air dehumidifiers, the frequency converter to the controlling unit, we only use components which are specifically compatible and specially developed for use in hay drying systems.»
For example, heat exchangers with a blade span of 2mm and special pipe connections are used. The evaporator for the dehumidifier is coated with a layer of anti-stick Teflon to ensure faster drainage of the condensation water. The improved compressor technology of the new generation systems, improved heat exchangers and innovative SPS control technology drastically improves performance and the drying efficiency.
At the same time automatic monitoring of all important parameters, such as CPC regulation, prevents disruptions such as the air dehumidifier freezing, emphasises Keller (more about the technical details later). But first of all, let’s take a closer look at the innovate “multi-box” drying concept.
Give the stalks time
Most SR hay drying systems are fitted with multiple drying boxes, which are all dried by just one ventilator. Up to 12 boxes are dried by a single ventilator. The multiple box concept has numerous advantages: drying is carried out at intervals. As a practical example, the feed from the Stierli’s farm is distributed between two boxes after a big harvest. By switching between air vents, each box is automatically ventilated for 60 minutes at a time. «After 60 minutes of ventilation time the outermost layer of the stalks is so dry that drying efficiency is reduced. This is why we give the feed a 60 minute resting period to allow more moisture to reach the outer layer», explains Keller. Interval drying takes advantage of self-warming without a loss of quality, which leads to a drying time that is around 30% shorter than with constant ventilation and thus consumes less energy. As the Stierlis sell the feed immediately after drying, “only” two large boxes and one small box were installed. More boxes are generally installed on farms that keep their own animals. On Josef Reindl’s farm he has implemented his concept consistently: he has a separate drying box for each cutting with a filling level of six metres. This allows him to mix and use the hay as feed with a constant ratio of all of the cuttings when removing the feed throughout the winter. Additionally, the drying process for fresh feed is never hindered by the older feed.
A smaller box
At least one of the boxes is designed with a smaller surface area. In particular, this is due to the need for minimum filling levels:
«Our high ventilation pressure system only works properly if a minimum filling level of (depending on dry matter content) at least two to three metres is attained (no dry chimney formation)», says ventilation engineer Keller. The smaller box is specifically for smaller harvests – partial areas or sections with low yields. The rule for filling levels differs fundamentally from the previously used systems: in the case of conventional ventilation, it is only possible to fill one to two metres each time – dependent on dry matter content – while two to seven metres are filled in SR systems. This decisively reduces the required grate area per ha of hay brought in. Now back to the technical details of the system.