Energy-technological complex of Kalina cycle for seawater desalination

. A scheme has been developed for the use of low-potential energy for heating water, including for the purpose of desalination of sea water. An assessment of the effectiveness of the Kalina cycle is given. It is proposed to use heated water in the water treatment cycle. This cycle can be implemented on geothermal sources near the ocean. Installations based on renewable energy sources fit into the country's economy in an environmentally friendly way, and also increase energy security. Thus, the cycle is integrated into the seawater desalination system. However, there are some disadvantages to using geothermal energy. First, it is only available in certain parts of the world, since geologically active areas are required to access heat. In addition, installing the necessary equipment and infrastructure can be costly, making it difficult for some people to access this form of energy. Finally, the heat removal process can also lead to environmental degradation as it can harm sensitive ecosystems and water sources in the area.


Introduction
Renewable energy sources have attracted a lot of attention in recent years because of their potential to reduce carbon dioxide emissions and provide an alternative to traditional energy sources.Geothermal energy is becoming an increasingly popular source of renewable energy due to its reliability, availability and economic efficiency, as well as low environmental impact.To extract heat from rocks, a heat pump is used that is included in the Kalina cycle [1,2].
Heat pumps are a reliable, efficient and economical way to use geothermal energy and an important tool for reducing energy consumption [3,4].They work by transferring heat from the ground to the air and vice versa, using a compressor to pump refrigerant between them.Heat pumps are highly efficient and can save a significant amount of energy compared to conventional heating and cooling systems [5,6].
The strategic goals for the development of electric power and thermal capacities in the design of energy complexes with geothermal sources are the reliable energy supply of the population and the provision of drinking water using modern technologies, reducing the impact of greenhouse gases on the environment.Currently, due to rising prices for fresh water, it is trying to find more economical options for its production.It is also impossible to achieve stable production of fresh water with powerful power plants.The importance of generating small-scale electricity using renewable energy sources is due to the security and demand on the world market, as well as the changing socio-economic situation in the world.The main advantage of this method of energy production is the absence of dependence on centralized power supply.In combination with the integration of such technologies, the production of fresh water will become more economical, which will reduce the price of water.
Desalination and desalination of water while creating highly efficient technological schemes can greatly contribute to solving the problem of fresh water shortage in the world.It is advisable to use a circulating water supply system for the purposes of saving water.The development of desalination technology on the basis of a wide range of research has achieved high results to date.Desalination complexes are becoming multi-purpose and low-cost.Such installations can produce drinking and industrial water, as well as salt.

Materials and methods. Scientific novelty
The task of the thermal calculation of the working process in a renewable energy installation is to determine indicators that characterize the economy and efficiency of the cycle under given specific conditions and are necessary for calculating the heating and cooling areas.Based on the thermal calculation, it is possible to calculate the flow exergies, enthalpies and temperatures with sufficient accuracy for practice.Thermal calculation is usually carried out for the operating mode of the installation corresponding to the rated power under the most favorable conditions for the supply of heat.
As already mentioned, the Kalina cycle used in geothermal power plants has two distinctive features [7,8,9].Firstly, instead of using hot water extracted directly from the bowels of the Earth, its energy is transferred to another liquid.This two-circuit or binary system is the second feature in which a two-component water-ammonia mixture is used as a working fluid [10,11,12].This process turned out to be significantly more efficient than other binary schemes [13,14].Scientific novelty lies in the use of this cycle in mountainous areas, for example, in the conditions of the Southern Urals.Such cycles are not widely implemented due to the complexity of use.However, modern methods are such that they allow this cycle to be realized [15,16].The article uses methods for analyzing the efficiency of the Kalina cycle and a desalination plant, including methods of thermodynamic analysis and the exergy method [17,18].The following methods should be noted.Firstly, it is the improvement of the organizing structure of the working process in distillation thermal desalination plants and the creation on this basis of new designs of evaporators.The main task that is solved in this case is a significant reduction in the specific heat consumption for the production of distillate, a decrease in the mass and dimensions of the installation.Secondly, it is the development of desalination technology based on reverse osmosis.Here the task is reduced to the development of new materials.

Results. Practical significance
The results of the study will be presented in comparison with the Rankine cycle.This visualization shows the promise of using such technologies, fig. 1, 2. The efficiency of Rankin and Kalina cycles depends from the temperature pressure between heat carriers [19,20].The Kalina cycle is more efficient, in the same temperature range, in comparison with the Rankine cycle, due to the highest temperature of the heat supply.In addition, the Kalina cycle is more economical in terms of fuel utilization.It should be noted that this cycle has a smaller carbon footprint [21,22].The use of the Kalina cycle for desalination plants makes it possible to use the technological advantages of thermal distillation.The share of thermal desalination plants on the world market is quite large compared to other types of plants.Their main advantage is their simple design.The quality of the resulting water meets the requirements of the consumer.The absence of complex equipment in the Kalina combined cycle and the thermal desalination plant increases the reliability of operation and process automation.Changes made to the design of such plants increase efficiency and reduce the cost of fresh water produced.This is achieved by creating new technological systems that are characterized by minimal heat consumption.

Discussion
The introduction of a heat pump into the thermodynamic cycle of Kalina has the potential to significantly increase its efficiency [23].By using a heat pump [24], the cycle can extract thermal energy from a low-temperature source and transfer it to a higher temperature sink.This effectively reduces the temperature difference between the two sources, allowing the cycle to operate with a lower entropy change As a result, the thermal efficiency of the cycle increases, due to a large heat transfer, which is converted into work.According to technological standards, water in desalination and chemical water treatment systems should be heated; heat pumps can be used for this.Overall, the introduction of a heat pump into the thermodynamic cycle of Kalina is likely to increase its efficiency, fig. 3. The Kalina cycle can work together with the seawater desalination cycle, fig. 4. Consider the variant of the Kalina cycle according to Fig. 3.An interesting fact about this scheme is the use of a mixture of ammonia and water as an intermediate heat carrier.As we can see from the figure, electricity is generated in the cycle.As you know, a water-ammonia mixture is characterized by different boiling points for its two components.In this regard, the cycle is divided into parts with a low proportion of ammonia in the mixture and with a high proportion of ammonia.The cycle according to Figure 3 fits easily into the cycle of operation of the desalination plant according to Figure 4. Figure 4 shows a plant operating on a reverse osmosis cycle.Water must be pumped before use.To drive the pump, electricity obtained from a turbine operating on water-ammonia steam can be used.In reverse osmosis plants, a significant increase in their productivity has been achieved.In addition, the mechanical strength of the membranes has been increased due to a more advanced technology for their manufacture.Ultimately, this led to another positive moment, namely, an increase in the pressure of the source water at the inlet to the reverse osmosis unit.A combined technology of reverse osmosis and thermal distillation has also appeared.The author offers a multifunctional approach that combines the generation of thermal, electrical energy and an algorithm for desalination of water with subsequent extraction of salts from salt solutions.This system eliminates the possibility of repeated pollution of the seas and oceans, and can also be used in various industrial and domestic conditions.In addition, studies have shown that it is possible to develop more reliable and competitive technological schemes that are cost-effective for freshwater consumers compared to existing installations.The desire to solve the problems that have arisen has shown that there are a number of promising studies that need to be industrially tested.However, in this case, the issue of removing agent residues from desalinated water has not been fully resolved.In modern seawater desalination technologies, several group methods can be distinguished.Two groups of methods for desalination of water are known.The first group uses changes in temperature, such as distillation and solar desalination, while the second group does not require any shifts in the state of aggregation, such as reverse osmosis and chemical desalination.As climate change continues to be a pressing global issue, many nations -especially those in warm climates -are now starting to install desalination plants that use seawater as a source of potable water.The widespread use of such plants is hindered by the still high cost of produced fresh water.However, for those countries in which there is a shortage of fresh water, this circumstance is not a deterrent.
The progression of desalination technology, the invention of new sorts of plants, the evolution of new ideas and more modern arrangements lead to a continued growth in the financial effectiveness of energy technology systems for desalination.It is noteworthy that the use of renewable energy sources in this technology drastically decreases the expense of electricity, thus minimizing the cost of the fresh water generated.The effectiveness of desalination plants for the production of edible drinking water is well known.Thermal distillation with complete demineralization ensures the best water quality for the consumer.By treating this type of water, it can be turned into drinking water of the highest quality.

Conclusion
At the end of the study, we present the main fragments.First of all, a technological scheme was developed for using low-potential energy for heating water and generating energy.This scheme is at the beginning of the seawater desalination cycle, and the desalination cycle can be with a change in the state of aggregation, or without changes.The first group of desalination methods is followed by thermal filtration and solar desalination, and the second group of methods is reverse osmosis.The proposed scheme combines the Kalina cycle and the reverse osmosis desalination plant cycle.An assessment of the effectiveness of the Kalina cycle is given.It is proposed to use heated water in the Kalina cycle for water treatment, and the generated electricity to drive pumps.This cycle can be implemented on geothermal sources near the ocean.Installations based on natural environmental energy sources in accordance with the frequencies of countries also increase energy security.Thus, it is cyclically integrated into the seawater desalination system.At the end of the study, I would like to draw the attention of readers to one more problem of using seawater desalination plants.Such a problem is salt pollution of the environment by waste from the production of fresh water.This pollution violates the natural balance and requires a technological solution at the design stage of the energy technology complex.Coastal areas will otherwise suffer from excessive heat and salt exposure.In this case, it is necessary to observe the temperature regime and rational use of natural resources when disposing of waste from the desalination plant.The significance of the last task cannot be overstated, as the release of pollutants into the sea or land will irreparably damage the environment.The ecosystems in these areas are incapable of restoring balance, leading to dramatic changes in the flora and fauna.To counter this, agro-industrial complexes should be established that employ waste-free water desalination technology.