In order to use all the potentials of agricultural production in the Republic of Serbia, it must be modernized. One of the possible directions in that modernization is the striving for the self-sustainability of the village.

The self-sustainability of the village, especially the one related to the greatest possible energy self-sustainability, cannot be imagined without the cooperative connection of agricultural producers. Cooperative connection provides preconditions for: changing the structure of agricultural production, processing and finishing of agricultural products, industrialization of villages, etc. All these prerequisites also provide the opportunity to create new jobs in the countryside and connect agricultural production with the latest scientific advances in the field of cultivation and processing of agricultural products. The text emphasizes the energy self - sustainability of the village in connection with the cooperative connection of agricultural producers.

 

The extinction of the Serbian village is one of the biggest problems of the Republic of Serbia. The demise is a consequence of the opening of the market, the collapse of the socialist way of doing business, as well as the difficult placement of agricultural products and their processed products due to the shrinking market and the general political situation. In addition, the problem is in the fragmentation of plots (possessions) and all kinds of production whose products can never be competitive on the open market. One of the possibilities to prevent the extinction of villages is to focus on their greater self-sustainability. Cooperative networking of farmers can play a key role in this. Again, on the other hand, the measure of greater self-sustainability of the village is the creation of conditions for greater energy independence. This means using, as much as possible, the energy resources of renewable energy that the village has. This article is dedicated to this, which shows the attempt to apply the results of two scientific projects in the field of "Multidisciplinary Sciences - III projects" and "Technological Development", funded by the Ministry, in the application of the most common form of biomass in the Republic of Serbia for energy purposes. these development achievements can help in the cooperative connection of agricultural producers as well as the energy self-sustainability of the village.

Resources of renewable energy sources in the Republic of Serbia

The largest potential source of renewable energy in the Republic of Serbia is biomass. Biomass potential represents ≈61% of the total renewable energy potential in the Republic of Serbia (official data). Of the biomass potential, ≈60% is in agricultural biomass, while ≈40% refers to forest biomass. When we talk about agricultural biomass, we mean that part of agricultural production that is not used in human and animal nutrition and which is treated as the rest of agricultural production. These are mainly: residues of field production, wood mass from fruit and vineyard production, residues from fruit and vegetable processing, manure, etc. Of these types of agricultural production residues, the most common are those that can be collected in the form of bales, ie residues of field production (straw and stalks of field crops: wheat and other cereals, corn, soybeans, sunflowers, oilseed rape, etc.). To this should be added the possibility of collecting in the form of bales and a good part of energy plants that can be grown only to meet energy needs. Unused, or poorly used potential of biomass is the residue from deforestation (waste wood-branches, roots ...) as well as residues from the processing of agricultural products.
The mentioned projects of the Serbian Ministry of Education, Science and Technological Development referred to the development of technologies suitable for the use of agricultural biomass in the form of bales, as the largest individual potential of renewable energy in the Republic of Serbia, as well as other underused biomass.

DEVELOPED TECHNOLOGIES - Starting points of development

The development was based on the following principles:

- to develop technologies suitable for the most common agricultural biomass in Serbia, as well as those that have not been used so far,
- adapt to the possibilities of domestic industry,
- the operation of the developed devices must be in accordance with the adopted norms on environmental protection,
- the degree of efficiency (energy efficiency) must be at the level of devices acceptable to the EU, ie over 80%,
- devices must be as simple as possible, and thus cheaper, both in terms of basic investment and operating costs,
- In parallel with the development of basic devices, logistics systems (collection, transport, storage, ash handling, etc.) must be developed.

After insight into the starting points of development, it was decided to develop combustion technologies. Before entering the concrete development of technology, possible combustion technologies were considered. We found help in deciding which combustion technology to develop in the Study of the EU Energy Institute. This study shows Table 1, which shows which combustion technologies are suitable for different forms of biomass. The last column in Table 1 lists the straw, which means all biomass that can be collected in the form of bales. In addition, we have added the last row in the table based on our many years of experience in the application of fluidized bed combustion technology.

 

 

Acceptance marks of combustion techniques from Table 1: (-) extremely unfavorable, (-) unfavorable, (0) possible, (+) favorable, (++) very favorable.
Based on all the above, the development of a system for cigarette combustion of biomass in baled form was started. We have supplemented the technology of cigarette combustion with the technology of combustion in a fluidized bed. In the fluidized bed, the coke residue of biomass is burned, which is separated (waste) from the bale, ie from the process of cigarette combustion. Fluidized bed furnaces can also be independent of cigarette combustion. The development came to industrial application.

Developed plants

Boiler with cigarette combustion of baled biomass

The boiler has a unique construction, protected by a patent, with a capacity of 1.5-2 MW (Figure 1). It is installed in the PKB corporation and is used to heat 1 ha of greenhouses. It works for 9 heating seasons without any problems and saves PKB € 1,000-3,000 every working day, depending on the weather conditions.

Fluidized bed combustion boiler

Fluidized bed boilers are suitable for the combustion of those types of potential fuels and even harmful substances that cannot be burned in other, conventional systems. Such fuels include: sludge liquids (sediments from the reservoir of edible or mineral oil and crude oil, pulp from fruit processing and from the paper industry, etc.), various powders, granular substances such as waste coal, fruit stones, infected corn, etc. Materials with extremely high moisture or ash content can also burn in the fluidized bed. If the substances we want to burn do not have sufficient thermal power to achieve the required combustion temperatures, some conventional additional fuel can be added, gaseous, liquid or solid. An experimental demonstration boiler of industrial dimensions was built at the "VINČA" Institute, on which all potential fuels can be tested. Since each such fuel is specific, the tests serve to obtain design parameters for a realistic plant in which the tested fuel would be burned.

Advantages of developed combustion technologies

- Simple constructions
- Work within the recommended norms on environmental protection
- With the boiler for combustion of baled biomass, extremely low own consumption for bale handling. The average engaged power of the hydraulic dispenser is 1 kW / h, which is negligible in relation to systems where it is necessary to apply the following manipulative operations with bales: bale shredding, biomass shredding, intermediate transport to the shredded fuel buffer screw dispensers.
- Due to the simplicity of construction, both developed combustion systems have low maintenance costs.
- Boiler operation can be fully automated.
- An important advantage of the developed technologies is that they are completely the fruit of domestic development and 100% produced in our country. This statement is very important because any problems that may arise in the exploitation can be quickly solved by the intervention of domestic experts. This advantage is especially important in greenhouse production or in animal husbandry, when there must not be a single day of heating downtime during the heating season.

 

THE IMPORTANCE OF COOPERATIVE CONNECTION OF AGRICULTURAL PRODUCERS IN THE APPLICATION OF THE DESCRIBED COMBUSTION TECHNOLOGIES

Due to their characteristics, the developed technologies are ideal for application in rural areas. They can be used for heating as well as for processing and cultivation of agricultural goods. The average engaged power of heating plants in Serbia, during the heating season, is 45-50% of the installed. If the mentioned data is reduced to the whole year, it means that the available power of the heating plant, which can be used for needs other than heating, is greater than 75%. The last data is the basic precondition that small industrial zones for cultivation, processing and storage of agricultural products can be built within the mentioned heating plants. In winter, such a plant can be used for heating and to a lesser extent for technological purposes, while outside the heating season it can be used exclusively for technological purposes. There is no technology for processing agricultural products that does not require energy consumption. In order for such an idea to come to life, farmers would have to unite in cooperatives and agree on who would produce what in order to hire boilers throughout the year. This means introducing specialization in production. Specialization in production as well as product finishing certainly brings higher profits per unit of product or unit of arable land. All this is made possible by the use of such boilers. Fuel for the mentioned boilers can be provided by the farmers themselves, again by agreement, and the possible payment for heating could be made by delivering their own biomass (agricultural production residues that do not serve in human or animal nutrition and which had no market value before such use). An important item in considering the application of these boilers is that the possible construction of small industrial zones implies the employment of rural labor, which would significantly contribute to preventing the extinction of the village.

Possibility of application of developed technologies

Only in AP Vojvodina there are 6 cities, 52 larger urban settlements and 457 villages which are ideal for the stated application of developed boilers. They are ideal because they are urbanized and therefore suitable for heating. In addition, there are other regions in the Republic of Serbia where the situation is similar to that in AP Vojvodina (Posvina, Pomoravlje). With a good design and combination of the mentioned technologies, it is possible to achieve that these small industrial zones work all year round.
All the indicators presented here indicate that cooperatives can help revive the Serbian village. Everyone can benefit from that: cooperative members, other villagers, domestic machine building and industry, as well as the state as a whole. In order for the cooperative, described here, to come to life, it is necessary to engage the state in support of the proposed initiative. The Laboratory for Thermotechnics and Energy of the Vinca Institute, with its associates on the mentioned projects: Faculty of Mechanical Engineering in Belgrade, Innovation Center of the Faculty of Mechanical Engineering in Belgrade, Faculty of Agriculture in Novi Sad, Faculty of Technical Sciences in Novi Sad and Land Institute in Belgrade are always available. providing assistance in the application of the described systems.

 

Author: Dr Dragoljub Dakić
Innovation Center of the Faculty of Mechanical Engineering in Belgrade