My research

Tea withering real-time monitoring, analyzing, predicting and controlling system 

Deenside Tea Manufacturers-Gampola 

May 2019 – Present (Undergraduate project and research)

Background of the Study

Tea is nearly 5000 years old and was discovered, as legend has it, in 2737B.C. by a Chinese emperor when some tea leaves accidently blew in to a pot of boiling water. In the 1600s, tea became popular throughout Europe and American colonies. Now, Tea is consumed as a beverage throughout the world and grown widely in the countries of Asia, Africa and the near East. Earliest mention of tea is from China in 350B.C. It found its way to Europe in 1559, to England 1615, and to Indonesia in 1684. Commercial cultivation began in India n 1823 and in 1867 in Sri Lanka.

Tea industry plays a vital role in the economy in Sri Lanka. It is the major plantation crop in the country and Sri Lanka has the dignity of being the world third largest tea producer. Based on the 2003 data from World Bank tea export is around 13% of the total export of the country. According to the annual report 2005 of the central bank of Sri Lanka, annual production of made tea is nearly 317 thousand metric tons and 97% of this production is exported.

Within the current global tea market filled with the competitive global suppliers, the reputation earned by Sri Lankan tea for its quality has played a major role in securing the existence of the competitiveness of the Sri Lankan tea. Tea manufacture is the process of transformation of freshly plucked green tea leaves to black tea. The process itself is long, requires much care, attention, control and a scientific understanding of the complicated physical and chemical changes in the leaf as the manufacture progresses. There are several distinctive processes that take place in the manufacture of tea. In the conventional tea processing used in Sri Lanka several major steps can be clearly recognized.

1. Plucking

2. Withering 

3. Crushing, Tearing, Curling

4. Fermentation

5. Drying

6. Sorting

7. Storing

8. Packaging

Each of these steps has separate roles in deciding the final product quality. But withering is considered as one of the key stages which affect all the other operations followed.

Importance of the withering

Through all the above mentioned processes withering stands as the initial important process which results the end quality of the product since there is not a proper system to monitor the exact withered level in Sri Lankan tea industry. The importance of obtaining correct withers must be fully appreciated as variation in the degree or evenness of wither are reflected throughout all the stages of manufacturer, and if quality teas are to be produced, constant withering ratio must be adhered to and maintained. 

During withering, the most noticeable change is the loss of water by which the leaf become flaccid and is reduced from its turgid condition to a pliable from by uniform and gradual loss of moisture. This is the most suitable condition for traditional rolling process used in most of Sri Lankan factories. The rollers which are in use at present depend on a wringing action for the very important process of expressing the sap from the leaf and initiating fermentation. Without the correct physical conditions of the leaf, this is not possible, and any attempt at rolling fresh leaves results in cutting and not in twisting the leaf so that the tea tuned out is full of flat pieces of leaf and is referred to as flaky. The chemical changes which take place during withering are not of importance.

The chief factor on the rate of escape of moisture from the leaf is the drying capacity of the air surrounding the leaf. If the air is in dry state withering is rapid, while in the moisture saturated atmosphere no loss of moisture takes place. The second factor influencing the drying capacity of the surrounding air is its temperature. Air raised to a higher temperature has a higher drying capacity than air at a lower temperature.

Artificial withering of tea leaf by means of warm or hot air drawn through a withering loft by ventilating fan is effected by the evaporation of much of the moisture contained in such leaf and chemical changes that take place I the leaf at the same time. On the proper control of the temperature and humidity of the air used for the purpose causes the success of the withering. It is generally accepted that a natural wither gives results superior to those obtained by artificial withering, and one reason for this is that tea leaf while being artificially withered is usually subjected to unduly high temperatures and thereby loss in quality. 

Withers may be divided in to three types according to moisture removed from the leaf. They are termed light or soft, medium and hard withers. When the leaf has been withered down to only 60% or 65% of its initial weight, Leaf is said to be medium withered when it has been withered down to between 50% and 55% of its initial weight by slow respiration and evaporation in 18 to 24 hours by natural means or in shorter time by means of artificial withering. Hard withers reduce the weight of the leaf to about 45% of its initial weight, and more removal of moisture results in over withering.

Controlling the withering process

Therefore this withering process must be controlled using a real-time control platform in order to ensure proper withering and the final quality of the product. The monitoring of the essential parameters, the analyzing of the internal moisture reducing rate and the fan speed must be integrated to the above mentioned system and controlled while monitoring.

In order to achieve this task successfully initially an IOT based moisture content monitoring system was established as a decision support system. In this secondary phase the system was upgraded in to a full automated controlling system with several other add ones to the platform. Through this research component of the project, establishment of the moisture reduction prediction algorithm, initial moisture content identifying algorithm and required air flow rate identifying algorithm were achieved and integrated with the system. Further the input streams of data were increased and reliability and durability of the system was guaranteed.

Introduction to methodology

Our initial step of the entire research was to establish a reliable IOT platform to monitor the weight profile of the tea leaves undergoing the withering process. Under the objectives of the PR 410 we could achieve this task successfully. Then the second step of our research was to establish an analyzing algorithm to calculate the internal moisture reduction of the tea leaves undergoing the withering process. Through the MATLAB analyzing platform offered by the Thingspeak IOT service we could generate the regarding algorithm for the moisture content variation. After establishing the regarding monitoring and the analyzing platforms, the next task was to integrate the platforms with a custom android application to be used as a decision support system. All these tasks were completed under the PR 410. When we consider the entire research there are two other main components left to be completed.

1. Enhancing the moisture content indication platform to generate regarding input signals to automatic control unit and establishment of moisture content prediction platform of the automated tea withering process.
2. Design of an automated fan speed control system to act according to the input signals from the IOT decision making platform for tea withering process and investigate the effectiveness of controlled withering.
3. Under the research component 1, I intended to cover the further enhancing of the moisture content indication platform and the establishment of moisture content prediction platform of the automated tea withering process. The enhancement of the moisture content indication and the analyzing platform was achieved by covering several objectives.
4. Redesign the sensor apparatus and refabricating the sensor fixed apparatus enabling the mobilization of unit emplacement.
5. Finding the root causes for the existing code crashing bugs within the established system and addressing the issues.
6. Develop a reference moisture reduction curve according to the past data collected.
7. Establishment of the moisture content and the withering time prediction algorithm. 
8. Developing mathematical relationships and algorithm to identify the required air flow rate and the required humidity level to be maintained in the air.
9. Developing a mathematical model and an algorithm to calculate the initial moisture content of the withering tea leaves.
10. Simulate the results in a graphical representation. 
11. These are the main objectives covered in the process of enhancing the moisture content indication and the analyzing platform. 

Results