Cycle modes and valve positioning.
\r\n\t
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She is a member of the National Scientific and Technological Research Council (CONICET) of Argentina in the genetic toxicology field, the Latin American Association of Environmental Mutagenesis, Teratogenesis, and Carcinogenesis (ALAMCTA), the Argentinean Society of Toxicology (ATA), the Argentinean Society of Genetics (SAG), the Argentinean Society of Biology (SAB), and the Society of Environmental Toxicology and Chemistry (SETAC). She has authored more than 380 contributions in the field, including scientific publications in peer-reviewed journals and research communications. She has served as a review member for more than 30 scientific international journals. She has been a plenary speaker in scientific conferences and a member of scientific committees. 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He is a former member of the Executive Committee of the Latin American Association of Environmental Mutagenesis, Teratogenesis, and Carcinogenesis. He is the author of more than 450 contributions, including scientific publications, research communications, and conferences worldwide. He is the recipient of several national and international awards. Prof. Larramendy is a regular lecturer at the international A. Hollaender courses organized by the IAEMS and a former guest scientist at NIH (USA) and the University of Helsinki, (Finland). He is an expert in genetic toxicology and is, or has been, a referee for more than 20 international scientific journals. He was a member of the International Panel of Experts at the International Agency for Research on Cancer (IARC, WHO, Lyon, France) in 2015 for the evaluation of DDT, 2,4-D, and Lindane. 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The electrically driven refrigeration systems have high coefficients of performance (COP), low weights and small sizes compared to their current alternatives. However, they rely on a high-grade energy produced mostly from burning fossil fuels in thermal power plants and employ environmentally harmful refrigerants. Meanwhile, the increased demand of the electricity consumed by these refrigeration systems during the hot summer days leads to a considerable increase in the peak loads on the electricity grids causing increasing costs, blackouts and brownouts, and represents a great challenge in many of the developing countries. Thermally driven refrigeration technologies appear to be a promising alternative solution to limited energy resources and ecological problems. Such systems can utilize directly low-grade thermal energies or waste heat recovered from industrial processes, and use environmentally safe refrigerants as systems presented in [1]. The most interesting technologies are called ‘sorption cooling systems’ including desiccant, absorption and adsorption refrigeration systems (ARSs). Although the most cited drawbacks for sorption refrigeration systems are the high initial cost, heavy weight, large size, and the possible need for backup cooling systems, the benefits are nonetheless obvious [2]. They can employ natural substances as working fluids (water, ammonia, etc.), and use the available heat sources and clean energy more efficiently to produce refrigeration effect. For examples, burning fuels can be used directly to drive the sorption refrigeration systems; thereby the inefficiencies associated with the conversion of thermal energy to electricity and its transmission to the consumers can be eliminated. Solar refrigeration systems which offer the features of minimal operating cost, environmental preference, transforming solar energy directly into cooling power and maximum solar radiation are generally in phase with the peak demand of the cooling loads. Recovering the waste heats in industrial applications could improve the overall performance of such systems. Adsorption refrigeration systems (ARSs), one of these heat-driven systems, have a distinct advantage in their ability to be driven by relatively lower temperature heat sources as well as not involving any moving parts in the refrigerant cycle which means minimal maintenance and more durability. Nevertheless, there are two main drawbacks that limit their commercialization: the intermittently working principle (discontinuous cooling effect) and the low cycle COP. The latter is influenced by poor mass and heat transfer of the adsorbent bed, the heart of the cycle, which plays the role of compressor in conventional refrigeration cycles [3]. Historically, the earliest record of the adsorption phenomena for refrigeration purpose was introduced in 1848 by Faraday who found that the cooling capacity could be generated when silver chloride adsorbed ammonia. Compression refrigeration systems were developed starting from 1930s after Freon was developed. In the 1970s, the energy crisis took hold, and in the last four decades, the environmental impacts of conventional refrigeration systems had been recognized worldwide, which offered a great chance for the development of such ARSs. The objective of this chapter is to introduce a comprehensive overview about the principles, application and challenges of ARSs. In addition to the description of the basic adsorption system, the chapter covers the following topics such as characteristics and development of working pairs; trends in improving the heat and mass transfer of the adsorber; advanced adsorption cycles; and state of the art adsorption cooling applications.
From the thermodynamics point of view, a basic adsorption refrigeration cycle can be considered as two separate cycles. One a heat engine and the other is a refrigerator (or heat pump), and operates with three temperature levels. It is assumed that the work produced by the heat engine is used to drive the refrigerator as illustrated in Figure 1 [3].
Representation of the thermodynamics cycle of ideal ARS.
The basic ARS consists of four main components: an adsorbent bed, which contains highly porous bodies called adsorbent with tremendously large internal surface (such as silica gel, activated carbon, zeolite, etc.) having strong adsorptive property to a specified gas or gases called adsorbate/refrigerant (such as water, ammonia, methanol, etc.). The adsorbent is normally packed on a metal surface which is required to conduct the heat transferred from/to a heat transfer fluid (HTF) (usually by heating and cooling water) that flows in the bed. The other 3 cycle components are: a condenser, an evaporator and an expansion valve. They are similar to those normally used in a simple conventional refrigeration cycle and play the same roles with an electrically driven compressor, so that the adsorbent bed is called a thermally driven compressor which circulates the refrigerant in an adsorption cycle by periodical switching between heating and cooling HTFs. The Carnot COP of a basic ARS can be expressed as Eq. (1) [4]:
A simple adsorption refrigerator produces cooling effect by subjecting the adsorbent bed to four sequential processes which are pre-heating, desorption, pre-cooling and adsorption as shown in Figure 2. Clapeyron diagram (LnP vs. −1/T) with respect to isosteres of adsorbent-adsorbate pair in Figure 3 is typically used to illustrate the four ideal thermodynamic processes of an adsorbent bed and calculate the cycle COP theoretically. In this ideal cycle, the adsorber (adsorbent bed) operates between the two constant pressures, the condenser and evaporator pressures, and the two (minimum and maximum) adsorbate concentration levels. These four ideal processes can be described as follows:
The flow diagrams of the basic adsorption cooling system under one complete cycle.
Clapeyron diagram of an ideal adsorption refrigeration cycle.
Pre-heating process (A−B): In this heating and pressurization period, the valves between the adsorbent bed and both of the condenser and the evaporator (V1 and V2) are closed, and the adsorbent bed is operated as a closed system that is subjected to heat source at temperature of TH by means of heating HTF. Meanwhile, the bed temperature increased sensibly which induces the vapor pressure inside the bed also to be increased. Whereas, the total amount of refrigerant in adsorbed phase remains constant at the maximum concentration. This process lasts until the vapor pressure reaches the condenser pressure at point B.
Desorption process (B−C): After the first process, the heating of the adsorbent bed is continued while the valve (V2) connecting the bed with the condenser is opened. The bed temperature is gradually increased, which induces a part of refrigerant which is in adsorbed phase to leave the solid surface of adsorbent to be in a vapor phase in a process called ‘desorption process’. Then this desorbed vapor flows into the condenser and condenses there. The vapor pressure in the bed is considered equal to the condenser pressure during this period which is ended when the adsorbed amount reaches the minimum concentration level.
Pre-cooling process (C−D): After the bed reaches the maximum temperature in the cycle at point C, the cooling and depressurization period for the bed is stared, and the two valves (V1 and V2) are set closed. The temperature is then decreased which induces the pressure inside the adsorber to be reduced to the evaporator pressure level by the end of this process.
Adsorption process (D−A): In the last period in which only the effective cooling occurs, the valve between the adsorber and the evaporator is opened, and the adsorber is continuously subjected to cooling by means of cooling HTF which induces an adsorptive vapor to accumulate on the adsorbent surface and converted to a new phase called ‘adsorbed phase’ in a process named ‘adsorption process’. Then, the vaporized vapor in the evaporator, which gives the cooling effect, is directed to the adsorber to take place in the adsorptive vapor. Cooling for the adsorbent bed is required in this process to release the associated heats from both the heating period and the adsorption process.
The average cooling capacity
where
The overall performance as well as the design and operating parameters for an ARS are greatly affected by the employed working adsorbent/refrigerant pairs. In general, good adsorbents should have wider range of adsorption capacity with temperature variation, higher heat and mass transfer properties, along with thermal stability and low susceptibility to contamination. In addition, distinctive properties of a refrigerant should be examined, and that include heat of vaporization, thermal conductivity, boiling point and working pressures, reactivity and stability, toxicity, environmental impact and freezing point. The adsorption capacity of an adsorbent-refrigerant pair is commonly determined from plots known as adsorption isotherms as shown in Figure 4 [5]. These isotherms give the amount of adsorbed mass taken up by the adsorbent, after reaching the thermodynamic equilibrium, as a function of pressure at constant temperatures. Accordingly, adsorbent-adsorbate pairs and their developments can be compared based on their isotherms. However, when the adsorbent domain undergoes transient operating conditions, a kinetic model is required to define the mass transfer kinetics and gives the instantaneous amount of adsorbate through a relation with the equilibrium uptake that is given by the isotherms. Mass transfer kinetics is a catch-all term related to intra-particle mass transfer resistance. The increase in the adsorption capacity increases capability of an ARS to have a large cooling capacity, where it sets up the total amount of refrigerant that can be adsorbed in a cycle. However, faster mass transfer kinetics is required to insure higher cooling capacity as it controls the duration of the adsorption cycle.
Isotherms for type RD silica gel-water pair [5].
The most commonly used adsorbent/refrigerant pairs are silica gel/water, zeolite/water, activated carbon/methanol, activated carbon/ammonia, calcium chloride/ammonia and composite adsorbent/ammonia. In general, according to the nature of the forces involved in the adsorption process, they are classified into three categories such as physical, chemical and composite adsorbent/adsorbate pair.
The physical adsorbents that are used in ARSs rely on van der Waal’s forces to contain adsorbate. Three adsorbent-adsorbate pairs are generally considered to be the best available in applications:
Silica gel is an amorphous silicon dioxide, SiO2, made synthetically from sodium silicate, and has a granular, vitreous and highly porous form. The high-density silica is the common type of silica gel used in adsorption systems such as Fuji Davison types ‘A’ and ‘RD’ silica gel, which have pore diameter in the range of 2.0–3.5 nm, the pore volume is 0.3–0.4 cm3/g and the specific surface area is 400–700 m2/g [6]. The other types of silica gel with relatively high pore sizes can be used as a host material in composite adsorbents. The thermodynamics characteristics of silica gel-water working pair were investigated experimentally by several researchers as in [5, 7], and the empirically determined parameters for the isotherm equations had been calculated from the experimental data. The performance of the two-bed silica gel-water was evaluated experimentally and analytically by several researchers [8, 9, 10].
In general, the main advantage of silica gel over other adsorbents is that the regeneration temperature is typically 85°C which makes such system to be suitable for solar energy use and low temperature waste heat sources. Moreover, it could be as low as 50°C when multi-stage configuration system is applied [11]. In such case, for non-regenerative cycle, the dynamic losses due to the heat capacities of the adsorber components will be reduced which lead to higher COPs since the adsorbent itself and the container vessel do not need to be heated to high temperatures. However, desorption temperature must not be too high. If it is higher than 120°C, silica gel will be destroyed. The adsorption heat is relatively higher than activated carbon pair between 2500–2800 kJ/kg. Also, silica gel porosity level is lower than activated carbon (100–1000 m2/g). The maximum adsorption capacity at equilibrium could be between 0.35 and 0.4 kg/kg silica gel, while the net change in the instantaneous amount of adsorbate may not exceed 0.1 kg water/kg silica gel under typical operating conditions which is low. Another drawback is the limitation of evaporating temperature due to the freezing point of water and the uptake also is effected badly under a very low vacuum, that make silica gel-water refrigeration system be better to be applied in the air conditioning applications with large chilled water flow rates.
Zeolites are microporous, alumina silicate crystals composed of alkali or alkali soil. The zeolite-water working pair has a wide range of desorption temperature (70–250°C). Due to its stable performance at high temperatures, the adsorber can be directly heated by the exhaust gases from engines. Therefore, the zeolite-water system is simpler than that one driven by the hot water. However, the adsorption heat of zeolite-water is higher than that of silica gel-water, between about 3300 and 4200 kJ/kg [12], which will lead to low COPs, in addition to the drawbacks associated with using the water as a refrigerant. Several studies had been presented experimentally and theoretically to investigate and improve the performance of zeolite-water adsorption system particularly for vehicle air conditioning.
Activated carbon is a form of carbon that has a large specific area available for adsorption approximately between 800 and 1500 m2/g for most used carbon. Initially, raw materials such as coal, lignite, wood, nut shells and synthetic polymers undergo number of special pyrolysis or chemical treatment at high temperatures (700–800°C) to produce activated carbons. They can be produced in many forms including powders, microporous, granulated, molecular sieves and carbon fibers. Activated carbon has advantages of that: a relatively low adsorption heat among the other types of physical adsorbent pairs (1800–2000 kJ/kg), low adsorption heat is beneficial to the system’s COP because the majority of heat consumption in the regeneration phase is the adsorption heat [12], higher surface reactivity, suitable pore size [13] and large surface area. However, the thermal conductivity of activated carbon is poor and is near to the insulation material. For example, ACF-methanol system with a higher specific adsorption reaches up to 0.55 kg/kgads, and good mass transfer characteristics where void fraction of ACF layer is more than 0.90%, but the measured thermal conductivity is as low as 0.0893 W/(mK) [14]. The carbon physical characteristics could be optimized to obtain the best performance of ARSs.
Activated carbon-ammonia
While most of adsorbent-adsorbate pairs operate under high vacuum, an activated carbon-ammonia pair system has a high working pressure (about 1600 kPa when the condensing temperature is 40°C). So, permeability of sorbent is not critical and it can be easier and more applicable than sub-atmospheric systems. It is also more suitable than the activated carbon/methanol pair for heat sources of 200°C or higher. The drawbacks of this working pair are the toxicity and pungent smell of ammonia.
Activated carbon-methanol
Large adsorption capacity of activated carbon-methanol pair has adsorption capacity of about 0.45 kg/kgads. Low regeneration temperature can be used to drive ARS employing activated carbon-methanol pair (about 100°C). On the other hand, it should not be used with regeneration temperature higher than 120°C, where activated carbon will catalyze methanol to decompose into dimethyl ether at a temperature more than 150°C, and operating pressure of the system will be sub-atmospheric and that requires assistant vacuum system.
Chemical adsorbents sorb the refrigerants differently than physical adsorbents where the strong chemical bond between the adsorbent and the refrigerant takes place in chemical adsorption. The uptake in the chemical adsorbents is not limited by the surface area of the material, which generally leads to higher mass transfer kinetics when compared to physical adsorbents. The metal chlorides are commonly used as chemical adsorbents due to their high adsorption capacity, and they involve calcium chloride (CaCl2), strontium chloride (SrCl2), magnesium chloride (MgCl2), barium chloride (BaCl2), manganese chloride (MnCl2) and cobalt chloride (CoCl2), among others. For example, in CaCl2/ammonia pair, 1 mole calcium chloride can adsorb 8 moles ammonia [15].
Generally, chemical adsorbents have very large uptakes with specific adsorptions approaching 1 kg/kgads in some cases, and desorption temperatures varying from 40 to 80°C which are very promising. However, chemical adsorption systems stability is lower than that for physical adsorption systems due to agglomeration and swelling phenomena, which are common in chemical adsorbent beds. This instability reduces heat and mass transfer which limits the cooling capacities of chemical adsorbents. Consequently, heat-driven chillers utilizing these adsorbents have been less common than those using physical adsorbents. To overcome this problem, the porous heat transfer matrixes were put forward for the improvement of mass transfer as well as the heat transfer by using composite adsorbents.
Composite adsorbents, also called “Salt in Porous Matrix (CSPM)” represent the promising solution of aforementioned drawbacks associated with pure physical and chemical adsorbents. Thus, many of these composites, which are typically made of porous media and chemical adsorbents, have been developed synthetically to be applied in adsorption refrigeration systems as in Refs. [16, 17, 18]. In such composites, porous media work on improving the heat and mass transfer properties of the chemical adsorbents along with limiting the swelling characteristics of the chemical adsorbents, while the chemical adsorbents increase the refrigerant uptake of the adsorbent pair. The common examples of these composites are combinations of metal chlorides and AC, ACF, expanded graphite, silica gel or zeolite. For example, silica gel and chlorides/water which are known as selective water sorbents (SWSs) which are tested and studied by Aristov et al. [6]. Composite adsorbents of silica gel and chloride are usually produced using the impregnation method. The silica gel is immersed in a chloride salt solution and is then dried to remove the water. There are also four types of porous media were used with chlorides to produce composite adsorbents/ammonia: activated carbon, activated carbon fiber, expanded graphite or vermiculite.
Metal-organic frameworks (MOFs) are highly crystalline porous material that are widely regarded as promising materials for various applications such as catalysis [19], gas separation [20] and gas storage [21]. The high crystallinity of MOFs can be highlighted through the description of MOF-5 structure which was once described as “The zinc carboxylate cluster with the six carboxylate carbons forming a regular octahedron but with tetrahedral symmetry was elegantly beautiful especially when linked in such regular arrays like terracotta warriors” [22]. Usually, the approach of assembling new frameworks out of molecular building blocks or secondary building blocks held together by strong bonding has been considerably used in designing new materials even though it is a challenge to control the assembly of the basic building blocks in the solid state and thus predicting of the resulting structure. Based on the same concept or what is called the reticular synthesis, MOFs are designed based on the assembly of organic units and metal clusters as secondary building units (SBUs) to build the robust complex structures (Figure 5) [23]. Compared to conventional microporous inorganic materials such as zeolites and silica gel, MOFs were found to be flexible regarding controlling their architecture and functionalization of the pores [24]. Such tunable properties have given the lead to MOFs over conventional adsorbents as they offer high stability and porosity as shown in Figure 6 . As mentioned above, these exceptional properties made this class of materials very interesting in a number of applications. Adsorption heat pumping for cooling applications has attracted a massive research over the past few years. For decades, the adsorption cooling application was mainly based on silica gel, activated carbon and zeolites which suffer from the limited adsorption capacity. The next section will discuss the different MOF materials with different refrigerants for cooling applications.
Schematic representation of how the framework is formed [47].
BET surface area comparison between some reported MOFs and zeolite [48, 49].
Water is an environment friendly refrigerant with high latent heat of evaporation and high heat and mass transfer properties. Water-based adsorption systems use adsorbents like silica gel and zeolites which have limited water uptake capabilities (up to 0.3 gw/gads) leading to low specific cooling power. The introduction of metal-organic frameworks (MOFs) material for adsorption cooling application allowed an improvement in the performance of the systems due to the high-water uptake that can reach up to 1 gw/gads and the potential of using low temperature waste heat or solar collectors as primary energy sources. Shi et al. [25] showed that using CPO-27(Ni) MOF material (a max water uptake of 0.45 gw/gads) for automotive air conditioning can outperform SAPO 34 zeolite material in terms of specific cooling power. They showed that CPO-27(Ni) produced specific cooling power of 440 W kg−1 at a desorption temperature of 130°C and a cycle time of 900 s compared to 310 W kg−1 for SAPO-34 at the same operating conditions. Numerous metal-organic framework materials have been studied to investigate their water adsorption capacity, Figure 7 shows maximum water uptake of a number of MOFs that were investigated for adsorption cooling applications at 25°C.
Maximum water uptake comparison between some reported MOFs, silica gel and zeolite.
Ehrenmann et al. [26] showed that MIL-101Cr can adsorb up to 1 gw/gads with high performance stability, also the heat of adsorption value was near the evaporation enthalpy of water, meaning that the interaction energy with the framework was believed to be very low compared to other materials used so far, like zeolites and hence the material do not require high regeneration temperature. A further modification was investigated by Khutia et al. [27] as the water loading capacity of four nitro or amino-functionalized MIL-101Cr materials (fully and partially functionalized) was assessed for heat transformation applications. The fully aminated MIL-101Cr-NH2, and partially aminated MIL-101Cr-pNH2, showed the best water loadings (about 1.0 gw/gads) and proving the weak host-guest interactions and hence a lower regeneration temperature is required. Elsayed et al. [25] further improved the thermal conductivity and the water vapor capacity of MIL-101(Cr) to be used in adsorption heat pump application through using hydrophilic graphene oxide. Two methods have been used to develop MIL-101(Cr)/GrO composites. It was shown that introducing low amounts of GrO (2%) to the neat MIL-101(Cr) enhanced the water adsorption characteristics at high relative pressure but enhanced the heat transfer properties by 20–30% while using more than 2% of GrO reduced the water adsorption uptake but significantly enhanced the thermal conductivity by more than 2.5 times. Yan et al. [28] managed to improve the performance of the material through developing another composite (MIL-101@GO) of MIL-101(Cr) and graphite oxide (GO) with high-water vapor capacity for adsorption heat pumps (AHPs). It showed that MIL-101@GO possessed a super-high adsorption capacity for water vapor up to 1.58 gw/gads. This superior water vapor adsorption/desorption performance make MIL-101@GO a promising candidate as the water vapor adsorbent for adsorption heat pumps (AHPs) process. Another factor that was studied was the effect molding on the water adsorption properties of MIL-101(Cr) after pressing the prepared powder into a desired shape which was investigated by Rui et al. [29] . It showed that the forming pressure has a large influence on pore structure of shaped MIL-101, as the forming pressure increases from 3 to 5 MPa, the equilibrium adsorption capacity of water is up to 0.95 gw/gads at the forming pressure of 3 MPa. Other types of MOFs such as Al fumarate was investigated by Jeremias et al. [30] in the form of coating on a metal substrate via the thermal gradient approach. It was concluded that Al fumarate is a promising adsorbent for heat pumping applications as it can be regenerated at low temperature as low as 60°C with a water loading difference higher than 0.5 gw/gads. Fadhel et al. [31, 32, 33], generated cooling effect from using aluminum fumarate and MIL-101(Cr) in different multi-bed water adsorption systems. The performance was compared to other adsorbent materials such as AQSOA-Z02 and conventional silica gel. The isostructural CPO-27(Ni) was compared to aluminum fumarate by Elsayed et al. [34]. It was highlighted that the CPO-27(Ni) outperformed the aluminum fumarate at low evaporation temperatures, while the aluminum fumarate was more suitable for applications requiring high evaporation temperature. It was also mentioned that CPO-27(Ni) is suitable for systems operated with high desorption temperature while on the contrary aluminum fumarate can be regenerated at low desorption temperatures.
The performance of a number of MOFs such as HKUST-1 and MIL-100(Fe) was investigated and compared to silica gel RD-2060 by Rezk et al. [35]. They showed that HKUST-1 performed better than silica gel RD-2060 with an increase of water uptake of 93.2%, which could lead to a considerable increase in refrigerant flow rate, cooling capacity and/or reducing the size of the adsorption system. However, MIL-100(Fe) MOF showed reduced water uptake comparable to silica gel RD-2060 for water chilling applications with evaporation at 5°C. These results highlight the potential of using MOF materials to improve the efficiency of water adsorption cooling systems. Other MOFs such as MIL-53(Cr), MIL-53(Fe), Birm-1, Birm-1(K) and Birm-1(Li) showed water uptake of 0.14–0.35 gw/gads which is lower than the water adsorption capacity of HKUST-1, proving that HKUST-1 regarding to the water capacity outperform conventional porous materials such as silica gel and other MOF materials [36], comparing HKUST-1 with other zeolite materials like SAPO-34 and AlPO-18 showed that the best SAPO-34 samples had a water uptake of 0.253 gw/gads which is a factor of 4.9 larger compared to the reference silica gel. Those results were only exceeded by the best AlPO-18 sample with a measured water uptake of 0.254 gw/gads for the low driving temperatures. This equaled an improvement by a factor of 6.2. For driving temperature of 140°C, the highest water uptake was found for the metal-organic framework HKUST-1 [37].Other MOFs such as MIL-100 (Fe and Al) with a water uptake of 0.76 and 0.5 gw/gads were found to be also very interesting candidates for thermally driven, sorption-based chilling or heat pump systems [38, 39]. A 3D MOF material (ISE-1) was found to have water loading of 0.210 gw/gads which was found to be larger than other five zeolites in that study and of the reference silica gel demonstrating the potential of MOF materials for use in adsorption heat pumping processes [40]. MIL-53(Al), MIL-100(Fe) and ZIF-8 were compared with the previous materials and were found to have a water uptake higher than 0.3 gw/gads proving that MOFs are a very promising class of materials for the use in adsorption heat pumping/cooling processes [41, 42]. The amino-functionalized MOFs UiO-66 and MIL-125 (H2N-UiO-66 and H2N-MIL-125) featured also very promising H2O adsorption isotherms due to their enhanced hydrophilicity with a water load of ≈0.4 gw/gads and were considered to be especially beneficial for the intended heat pump application [43].
Saha et al. [44] presented experimental and theoretical investigations of adsorption characteristics of ethanol onto metal-organic framework namely MIL-101(Cr). The experiments have been conducted within relative pressures between 0.1 and 0.9 and adsorption temperatures ranging from 30 to 70°C, which are suitable for adsorption cooling applications. Adsorption isotherm data exhibit that 1 g of MIL-101(Cr) can adsorb as high as 1.1 g of ethanol at adsorption temperature of 30°C. The experimental results showed that the studied pair would be a promising candidate for developing high performance cooling device. Rezk et al. [45] experimentally investigated the ethanol adsorption characteristics of six MOF materials namely CPO-27(Ni), MIL-101(Cr), HKUST-1, MIL-100(Fe), MIL-53(Cr) and MIL-100(Cr) compared to that of silica gel as a conventional adsorbent material that is widely used in commercial adsorption systems. The results revealed that MIL-101(Cr) have shown superior performance with uptake value of 1.2 gw/gads. Also, MIL-101(Cr) proved to be stable through 20 successive cycles at 25°C. The results from theoretical modeling of a two-bed adsorption system with heat and mass recovery have shown that using MIL-101(Cr)/ethanol pair has remarkable potential in low temperature cooling applications.
Jeremias et al. [46] showed that the use of alcohols (methanol) as working fluids turned be a good prospect for the application of otherwise promising, but hydrothermally unstable or not sufficiently hydrophilic materials like HKUST-1 or MIL-101(Cr), respectively, or for low temperature applications, where the vapor pressure of H2O is not sufficient for acceptable kinetics and that heat and mass transfer could be optimized by various shaping procedures.
Enhancing the heat and mass transfer (HMT) of the adsorber is the most crucial part in developing ARSs. For a given cooling capacity, higher specific cooling capacity (SCC) means smaller amount of adsorbent to be used, and that can be a direct result of improving the heat and mass transfer performance of the adsorber. Besides, a lighter weight and smaller volume are existed in such case. As the adsorption system consumes less heat during regeneration modes, the COP is increased. Two methods are commonly used to increase the HMT: one is the development of adsorbents and the second is the optimization of the adsorber designs and cycle modes.
Intensifying the heat transfer of an adsorbent depends mainly on increasing its thermal conductivity where the conduction is the major way to transfer the heat through the adsorbent. Consolidating the adsorbent or using additives with good thermal conductivity into the adsorbent are the common approaches used to enhance the heat transfer in the adsorbent [50, 51]. However, such approaches always decrease the permeability of the adsorbent leading to a decrease in inter-particle mass transfer. The overall performance of the bed will be affected by this contradiction between heat transfer and mass transfer in the adsorbent. Thus, it should be considered that the increase in thermal conductivity 20-fold, for example, does not mean a similar great enhancement in the overall performance due to the reduction in mass transfer. On microscopic level, the distribution of micro layers inside the samples of an adsorbent affects both the thermal conductivity and permeability, and then investigation can be applied for enhancing both of them as made in Ref. [52]. Therefore, sample preparation and filling techniques can be optimized to enhance both heat and mass transfer. Testing adsorbents in various forms and sizes is also an effective way to investigate the best HMT performance of the adsorber. Developments of the composite adsorbents are another active area used to enhance refrigerant uptake of the pure adsorbents and their stability. More recently, there are two trends: coating the adsorbent over the heat transfer metal surfaces of adsorbers, aiming at the elimination both of thermal contact resistances and large inter-particle voids, or using the new metal-organic frameworks (MOFs) materials which provide attractive adsorption characteristics compared to common adsorbents.
From the standpoint that loose grains and consolidated adsorbent beds have poor heat transfer and mass transfer properties, respectively, the concept of coated adsorber has been developed to introduce adsorbers with efficient heat and mass transfer. Applying direct synthesis, or using a binder for deposition a layer of adsorbent over walls of the metal heat exchangers are two common technologies of adsorbent coatings. Different approaches have been reported and discussed in Ref.s [53, 54] as for illustrated in Figure 8 [55].
Adsorbers’ manufacturing procedure [55].
Optimized parameters and sophisticated designs of adsorber configurations can help in enhancing the inter-particle mass transfer in the adsorbent domain, along with facilitating the heat transfer between the adsorbent and heat transfer fluid HTF. Extended metal surfaces ‘fins’ are commonly used to intensify the heat transfer and overcome the low thermal conductivity of the adsorbent materials. However, the COP of an adsorption system is strongly affected by the metal-adsorbent mass ratio [56]. Therefore, the net effects of the fins parameters such as fin spacing, height and thickness should be investigated carefully to optimize the overall system performance [57, 58, 59, 60].
In the same context, operational control parameters, such as adsorber modes’ durations and fluid flow rates, influence considerably the ARSs’ performance and need to be also optimized. Basically, in view of the fact that the diffusion of mass within the adsorbent particles is better with higher temperatures, therefore, the desorption process is carried out faster than the adsorption process. That explains why the differences between equilibrium and instantaneous amount of adsorbate (Weq–w) in desorption and adsorption modes are not identical during the cyclic steady state. A larger difference is required during an adsorption mode to adsorb the same total amount desorbed during a desorption mode for making cyclic steady state. Increasing the cooling water velocity and/or adsorption duration over heating water velocity and/or desorption mode are the common ways to reach steady state cycle. And that increases need to be optimized for maximizing the adsorption system performance, as by adsorption/desorption times reallocation, [61]. Operating under low pressures is another challenge as in the case of water and methanol as refrigerants. In this case, the poor mass transfer in adsorbers can lessen greatly the difference in the refrigerant uptakes during the cycle. That requires more developed designs for such adsorbers to improve their performances. It is important to mention that studying the net effect of any operating parameter on the adsorption kinetic during only one mode (adsorption or desorption) based on given initial conditions may lead to inaccurate predictions for the overall performance.
In view of the fact that the basic adsorption cycle produces intermediated cooling output and its COP is low, many advanced adsorption refrigeration cycles have been proposed and developed to help in overcoming these main drawbacks such as the heat recovery cycle, mass recovery cycle, thermal wave cycle, cascade cycle and multi-stage cycle. However, the basic cycle is mostly used in the solar powered adsorption system for its simplicity.
The flow diagrams of a conventional two-bed cycle representing one complete cycle are illustrated in Figure 9. Each adsorber undergoes four operating modes: pre-heating, heating (desorption), pre-cooling and cooling (adsorption) processes in repeating cycles and according to the sequence shown in Table 1. The system consists of two adsorbent beds, a condenser, an evaporator and an expansion valve, in addition to the four connecting valves and connecting pipes. The working principle of the basic cycle is discussed in detail in Section 1.1 for one-bed ARS. In a two-bed ARS, while hot water is used to heat up Bed-A during the first two processes: cooling water is used to cool down Bed-B. The hot water is switched to Bed-B in the last two processes, as Bed-A is subjected to cooling water. The four valves are completely closed during the two switching modes. Circulating the cooling water and chilled water in the condenser and evaporator, respectively, are supposed to be continuous during the whole cycle.
Schematic diagram of a conventional two-bed adsorption chiller, as Bed-A in desorption mode, Bed-B in adsorption mode.
Mode | Component | |||||
---|---|---|---|---|---|---|
Bed-A | Bed-B | V1 | V2 | V3 | V4 | |
Mode-A switching | Pre-heating | Pre-cooling | X | X | X | X |
Mode-B Des/Ads | Heating/Des | Cooling/Ads | O | X | O | X |
Mode-C switching | Pre-cooling | Pre-heating | X | X | X | X |
Mode-D Ads/Des | Cooling/Ads | Heating/Des | X | O | X | O |
Cycle modes and valve positioning.
In a system of two or more adsorbers work between an evaporator and a condenser, there is a hot adsorber under cooling process and a cold one under heating process which offers the availability to recovery the heat inside the system. The experimental results show that the COP of the system will increase by up to 25% with the heat recovery cycle [62]. In a typical two-bed cycle equipped with mass recovery system, while one bed at the end of desorption mode at higher pressure and temperature, the other bed at the end of adsorption mode at lower pressure and temperature. Internal mass recovery process is started via connecting the high-pressure adsorber to the low-pressure one typically by means of a valve. The process ends when the two pressures become equal. The combined heat and mass recovery procedures may increase COP more than 10% [62], compared to heat recovery cycle. Thermal wave cycle is another way to recovery the heat inside the cycle. A typical thermal wave cycle is composed of two adsorbers, an evaporator, a condenser, a cooler and a heater as shown in Figure 10 [63]. Experimental results showed that the COP of a two-bed adsorption air conditioner (zeolite-water) with thermal wave cycle was approximately 1.0 in cooling season [12].
Schematic representation of the thermal wave adsorption heat pump during the first half of the cycle [63].
There are many of advanced and novel cycles proposed in literature for ARSs. The advanced cycles such as multi-bed cycle, multi-stage cycle and dual-mode cycle are originally developed to make utilize of lower temperature heat sources applicable and more efficient. Another trend in advanced cycles is eliminating the vacuum valves by putting the adsorber, condenser and evaporator in a single chamber to increase the reliability of the system, particularly under the vacuum operating conditions. Table 2 summarizes data about some applied or prototype adsorption chillers.
Summary of some adsorption prototypes.
Adsorption refrigeration systems have a lot of advantages making them more and more competitive when compared to conventional vapor compression refrigeration systems. Apparently, the environmental regulations and local safety considerations, the expensive and limited petrol energy resources, solar driven possibility and the increasing of industrial waste heat availability are all in favor of thermally driven refrigeration systems, particularly adsorption systems. The adsorption refrigeration technology has not been carrying out in mass production level yet. That justifies its higher initial cost compared to the conventional technology. On the other side, there is a serious need to consider together all aspects of energy, exergy, environment and economy in the future comparative studies. Also, it should be noticed that the thermal COPs of ARSs are around 0.6 which is low. However, the electrical COP values of ARSs can reach up to 10 which is high compared to that values of conventional systems typically between 3 and 5. In order to find out new direction of adsorption refrigeration systems developments, previous related researches are reviewed and classified in this chapter.
This work is funded by the Science and Technology Development Fund (STDF) program in Egypt under the UK-Newton Institutional Links Grants, project ID 26148, in collaboration with University of Birmingham, Birmingham in UK.
ARSs | adsorption refrigeration systems |
COP | coefficient of performance |
HEX | heat exchangers |
MOFs | metal-organic frameworks |
SCC | specific cooling capacity |
Weq | equilibrium amount of adsorbate |
At the beginning of this century, the topic of global climate change became of particular relevance for the regions of the Arctic and the North. This problem is actual in modern conditions. The Arctic climate changes faster than any other part of the world; this is the only highly integrated system in this belt; changes in the Arctic will have a big impact on other parts of the world. The Arctic will become an increasing center of world attention. Over the past few decades, the average annual temperature due to an increase in the average winter temperature in the Arctic has grown two times faster than elsewhere, causing the melting of sea ice and permafrost and a reduction in the snow period. The consequences of global warming in the Arctic are already obvious and numerous. Modern climate changes significantly affect coastal communities, species diversity of animals and plants, human health and welfare, as well as the economy and infrastructure of the Arctic regions. Global warming is the process of gradual growth of the average annual temperature of the surface layer of the Earth’s atmosphere and the World Ocean, due to all sorts of reasons (increase in the concentration of greenhouse gases in the Earth’s atmosphere, changes in solar or volcanic activity, etc.). Global warming will change the habitats of many species of terrestrial and marine flora and fauna. The most large-scale changes will be felt by the indigenous peoples of the North, whose life is inseparably linked with the natural environment. As the permafrost is thawing, the threat of destruction of buildings, roads, pipelines, airports, and other infrastructure increases, which in a number of cases will lead to significant economic losses, deterioration in the quality of drinking water supply, social tension, forced migration, and, as a result, an increase in the number of infectious and noninfectious diseases, including mental disorders and psychosomatic and addiction diseases. Indigenous peoples of the North are the most vulnerable category of the population to the climate negative impact in the Arctic. Limiting the possibility of using bioresources as a result of hunting and reindeer herding, fishing, and gathering, as well as reducing the safety of movement when the parameters of ice and weather conditions change significantly, increases the risks to health and life and, possibly, in the future, threatens the very existence of some nationalities and cultures.
\nGradually, in countries the understanding comes that the nature is the original environment of human life, but not capital, which should be used in economic circulation. Preservation of this environment is becoming one of the main tasks of state policy based on the principles of energy efficiency and resource saving. For example, in the Russian Federation, such basic documents as the Strategy of Ecological Safety of Russia [1], the state program on energy efficiency and development of energy [2], etc. were adopted. However, despite the billions of dollars invested by developed countries in greening the economy, the development of innovative technologies, and the reduction of greenhouse gases, there are still no visible effects on a global scale, and in fact the world is facing a degradation of the natural environment. As Nobel laureate academician Vladimir Kotlyakov notes, our planet is experiencing an era of global warming. The increase in global air temperature in the last century was slightly more than 0.7°C. However, over the past 30 years, this growth has increased, which is especially reflected over the continental regions of Eurasia and North America and most of all in the Arctic [3]. The current model of the functioning of the world economy allows us to make disappointing forecasts: the growing population of the Earth will be able to supply the products of consumption only with the increase of production, the improvement of technologies, and, unfortunately, the destruction of the biosphere.
\nFigure 1 demonstrates the anomalies of temperature values in the Northern Hemisphere, including the Arctic. This gives grounds to predict the increasing influence of negative factors on the ecosystem of this region, as well as on the life of the indigenous population. Certainly, climate change is a particularly important issue in the context of the development of the Arctic and the indigenous communities that inhabit it. Indigenous peoples also have their own observations related to climate change, since no one can see better what is happening now in the North, and there are significant shifts in their strategies for adapting to these changes. Traditional knowledge is a valuable resource that can and should be used in various fields of exploration and development of the Arctic. Unfortunately the representation of indigenous peoples in international governance structures does not guarantee that traditional knowledge is entirely engaged in evidence-based policy making and that traditional knowledge is not always valued as an equal source of knowledge by some relevant scientific bodies [4]. Hundreds of years of tribal communities’ observations over the changes in the Arctic, the formation of ideas about the laws of nature, beliefs in the “living land of ancestors” give today the opportunity to transform traditional knowledge into the daily practice of government, business, and scientists in the extreme North and integrate it with modern technologies. According to the Paris Climate Change Agreement, indigenous peoples and local communities are recognized as the important actors in building a world that is resilient in the face of climate impacts [5].
\nMap of monthly values and anomalies of meteorological values in the northern hemisphere for June 2018 (source: https://meteoinfo.ru/anomalii-tabl3).
We can rightly call the Arctic zone a “locomotive” of the modernization of the Russian economy [6]. In this vein, state policy is being drawn up, investments are attracted, and projects are being implemented to extract natural resources (gas, oil, gold, rare earth metals, etc.). Almost every one of these projects implemented in the northern regions of the country, one way or another, affects the territories of traditional nature use—the habitat of indigenous peoples of the North. Therefore, the issue of research and assessment of changes in these territories under the impact of climate change and industrial development is very relevant, since it has a multifactorial specificity, centered on the unique culture of the northern people, its traditions, and its customs. In Russia, indigenous peoples of the North, as a rule, live in the rural areas of the Arctic zone, which population, according to the Federal State Statistics Service, declines annually. Therefore, it is important to study the changes in these territories and develop policies aimed at preserving not only local communities as a carrier of culture and traditions of northern peoples but also traditional economic activities (reindeer herding, fishing, hunting, etc.), since the reindeer herding is the basis of the traditional culture of the North (Figure 2).
\nThe numbers of the permanent population of the land territories of the Arctic zone of the Russian Federation as of January 1, 2018 (number of people) [7].
The future of the Arctic territories is connected, on the one hand, with the expansion of the zone of industrial development and the extraction in deposits and on the other hand the increasing pressure on the unique ecosystem of the Arctic, the changes in the territories of traditional nature use, the transformation of indigenous population’s way of life, and tribal communities under the influence, including climate change. In Table 1 the main indicators describing the territories of traditional residence and traditional economic activity of the indigenous peoples of Russia are presented. This type of territory is located in 21 regions of the Russian Federation with reindeer pastures, hunting grounds and rich fishing opportunities, and gathering of wild plants on a total area of 994.2 million hectares, including lands used directly as reindeer pastures—407.0 million hectares [8].
\nClimate change leads to the transformation of the traditional way of life and also forces regional and local governments to seek new approaches to managing these changes, allowing them to adapt and adequately respond to emerging challenges. Prospects for the revitalization of the industrial development of the North in the future involve the withdrawal of an increasing number of lands of traditional nature use for inclusion in economic circulation. Undoubtedly, industrial development of indigenous peoples’ habitats at the present time determines the prospects for their further socioeconomic and ethno-cultural development. Considering the strategic nature of the state interests in the Arctic region and the attention paid to the development of deposits in Siberia and the Far East, it is necessary to devote harmonization of interests of industrial development of these territories and preservation of the habitat of indigenous communities, creation of mechanisms for interaction of task forces on optimization of economic, and social and environmental interests of all stakeholders in the territories of traditional nature use [10].
\nThe impact of climate change on indigenous peoples is diverse. This is especially reflected in health and the traditional way of life. Health as a factor in the well-being of indigenous peoples worsens, which shows itself in a high level of mortality with relatively high birth rates, problems with alcoholism, and diseases of the digestive system due to poor-quality drinking water. Significant climate change resulting in the increase of natural disasters, abnormal winter and summer temperatures, floods, mudflows, and landslides increases the number of deaths from unnatural causes, injuries, and subsequent health problems. Climatic changes are also the cause of more serious phenomena, as the deterioration of the parasitic and epidemiological situation. Degradation of permafrost in areas where this type of soil has been preserved for centuries, and on the basis of which the habitat of indigenous peoples and their feeding systems has been formed, leads to catastrophic consequences. Moreover, changes in the permafrost sometimes have unexplained causes, which raise an active discussion in the scientific community. So, in 2014 in Yamal, a giant dip of a soil of unknown origin was discovered. A huge funnel was noticed by helicopter pilots who serve the oil and gas fields on the Yamal Peninsula. The fault is located next to the Bovanenkovo gas field (Yamal LNG), one of the largest in Yamal—the place of one of the most innovative projects of modern Russia for liquefied gas production jointly implemented with Italy, France, Japan, and China (Figure 3).
\nYamal hole in 30 km from the Bovanenkovo gas field. (source: https://www.moya-planeta.ru/news/view/uchenye_vpervye_issledovali_dno_yamalskoj_voronki_8251/).
Later Russian scientists from Yamal managed to descend for the first time to the bottom of this dip—to a depth of 200 m. The hole has a cone-shaped view with dimensions of 60 and 40 m. They took more than a dozen samples for chemical analyses, including ice and soil. It turned out that the Yamal “black hole” from the inside is covered with a layer of ice of unknown composition, which has yet to be investigated in the laboratory. Analyses of air inside the funnel revealed the absence of harmful impurities and dangerous gases—on the basis of this fact, scientists concluded that in a mysterious earthly failure, a new life could arise in time. The scientists noted that they failed to solve the main riddle—how the process of a mysterious holes’ formation was going on in the Yamal land. The most authoritative experts consider these holes to be the result of the process of degassing the permafrost due to global warming [11]. Currently, the problem of tundra transformation under the climate change factors is becoming a significant threat to the traditional forms of economic activity, especially reindeer herding. The formation of thermokarst lakes, the degradation of biota, and the waterlogging of significant areas of the tundra during the summer period are risk factors and cause deer to change routes, and in the spring and autumn, a phenomenon such as ice, which is ruinous for reindeer herding, began to increase. Due to the steady increase in the amount of precipitation in recent years, a deeper snow cover is formed, creating difficulties for animals to hoof the reindeer moss. At the same time, the late arrival of colds led to difficulties in the transition of reindeers to winter pastures (Figure 4).
\nThermokarst lake in tundra with landscape degradation near Vorkuta, Komi Republic, Russia (photo: V. Gassiy).
In the northern regions of Russia in recent years, there have been no isolated cases in which thousands of reindeers perished from hunger. The increase in the mean annual temperature is detrimental to the regions of permafrost, where the centers of anthrax are revealed during thawing. In the summer of 2016 on the territory of Yamal, an outbreak of anthrax was caused by an abnormal heat. The most dangerous infection was safely suspended in the permafrost for 75 years. The most objective cause of the outbreak was called climate warming. Abnormal heat in the tundra to +35°C kept for more than a month. Comprehensive measures were taken to protect Yamal reindeer herders from dangerous diseases. All the livestock of the deer are vaccinated; the animals are fitted with chips. Vaccination is conducted among the tundra population and specialists from the risk group: in 2017, about 8.2 thousand people were vaccinated in the region, and the entire number of reindeer and more than 730 thousand animals were vaccinated against anthrax. Forty-two thousand representatives of the indigenous peoples of the North—14,000 of them live in a traditional nomadic way of life—and the largest reindeer herd in the world live in the territory of Yamal, so the ecological component plays an important role in preserving the traditional economic activities of indigenous peoples [12]. One of the main threats is the change in the water regime of rivers. Most of the modern settlements in the North are located on the banks of rivers. In recent years, spring floods have sharply increased, floods have become more frequent, and the processes of erosion of shores have accelerated, which bring great disasters to the population. For example, in the regions of northern Yakutia, the banks of the rivers Lena, Yana, and Anabar collapse under the influence of high temperatures and melting of permafrost, which leads to shallowing of rivers, a change in the relief of the bottom. As a consequence of these processes, boats of local fishermen cannot sail along the riverbed; the fish does not go far downstream; thus indigenous peoples are deprived of the type of product that forms the basis of their food ration. Reduction of fishing takes place together with a decrease in the level of production of hunting objects (wild reindeer changes migration routes; the number of fur-bearing animals decreases; because of warming, the meat of a wild animal is often affected by a viral infection or parasites), i.e., we are talking about the problem of access to traditional types of resources.
\nAccess to resources is closely linked to security, which is provided by traditional knowledge, accumulated for millennia. But the transformations that are taking place change the reality; the representatives of indigenous peoples are increasing in situations where their practice, experience, and knowledge cannot help them. This leads to an increase in the number of accidents, especially those associated with late freeze-up, ice, and early floods. One of the consequences is the restriction of access to traditional food. In addition to the above factors, one of the reasons is the deterioration of storage conditions. In recent years, the quality of food has sharply deteriorated. So, in the Bulunsky District of Yakutia, local residents often face the problem of phimosis (cysticercosis) caught from the Lena River. It should be noted that a similar problem is a characteristic of other regions of the Arctic where indigenous peoples eat fresh or slightly salted fish [13]. In 2016, Federal Service for Veterinary and Phytosanitary Surveillance in the Komi Republic during federal monitoring sampled liver and kidney samples of slaughtered animals belonging to the reindeer herding enterprises of Intinsky and Usinsky districts. Sixty-four samples were examined, of which 52 results were found with excess of mercury—the maximum permissible level was exceeded by 0.9 mg/kg—and 43 results with excess of cadmium, the maximum permissible norm is exceeded by 8.3 mg/kg [14]. In addition, in the liver samples, an excess of the normative indices of dioxins was detected—the maximum permissible rate was exceeded by 8.3 times. However, meat and other offal (with the exception of kidneys and liver) do not contain dangerous chemical pollutants and do not pose a danger to citizens. Accumulation of toxicants in the liver and kidneys of animals is due to the physiological properties of these organs, which are biological filters of organisms. Dioxins are formed in a number of industrial and natural processes, for example, in the production of chlorine and pesticides, burning fuel and debris, and forest fires. Cadmium and mercury pollute the environment both for natural and as a result of industrial activities. In particular, heavy metals pollute the environment during the smelting of nonferrous metals and other processes in the mining industry. It is believed that the northern communities of plants and animals tend to accumulate persistent contaminants, as they have a number of properties necessary for this, including the characteristics of the climate (preventing the destruction of substances) and food chains that are distinguished by a small variety of plant and animal species. According to the world scientific data, some traditional food of the inhabitants of the northern regions of the planet (Alaska, Greenland, Scandinavian Peninsula, Far North of Russia) have a high content of harmful chemicals. Such types of food include meat and fat of marine mammals, reindeer offal, and others [15]. In this way, there are more and more people who are forced to refuse from the consumption of raw fish, which often turns out to be infected with phimosis and other diseases. As a result, the probability of losing certain cultural traditions is growing, since food is an integral part of the traditional way of life and culture.
\nIt is also necessary to say about the impact of climate change on the health of indigenous peoples. In recent years there has been an increase in mortality in the Arctic. Almost every year there are floods, with every third year—with disastrous consequences and deaths. The number of hits to hospitals increased due to sunstroke, dehydration, pressure drop, etc. Surface water pollution increased, both from floods and melting of permafrost. This leads to an increase in intestinal diseases, especially in the period of floods. Also, in Arctic regions, there is increasing cases of oncological diseases [16]. Some experts attribute this to a more intensive chlorination due to the deterioration of water quality. The prolonged exposure to increased concentrations of chlorine and its constituents, according to doctors, increases the risk of cancer. Warming has widened the areas of spread of diseases, the carriers of which are insects or mites that spread to all new territories. One of the main risk groups for climate change is the children. In northern regions, up to 70% of children have deviations in health status. The incidence of children in the northern regions is significantly higher than the national average. Over the past 10 years, they tend to grow. Children of the North and children of other regions are in unequal starting conditions of life. Under the influence of unfavorable climatic factors and polluted environment, the age development of the immune system falls behind in children of the North for 2–5 years. Thus, for indigenous peoples of the Arctic, the warming of the climate and the associated lengthening of the season, during which the sea is not covered by ice, a decrease in the surface and thickness of sea ice, changes in the migration routes of wild reindeer and their food base, and a drop in the number of marine animals may lead to a reduction in traditional craft. This, in turn, will lead to a violation of traditional food. The indigenous inhabitants of Alaska and Greenland, Chukotka, and Yamal are already recording the negative effects of climate warming, which appeared in a decrease in thickness and an earlier opening of sea ice. These circumstances make it more difficult to hunt and lead to an increase in the number of injuries, which is already the cause of a significant number of deaths among indigenous peoples of the North [17].
\nFigure 5 shows the riverbed of the Anabar River near the village of Saskylakh in the northwestern part of Yakutia. Fishermen are forced to manually drag the boat a few kilometers downstream to reach the fairway (Figure 6).
\nShallowing of the Anabar River in Yakutia (photo: V. Gassiy).
Collapse of the riverbank of Yana due to permafrost melting, Yakutia (photo: V. Gassiy).
In 2017, an expedition aimed to the research on socioeconomic and environmental problems of the Arctic indigenous communities was organized by the financial aid of the Russian Fund for Basic Research (RFBR) to the Anabar National (Dolgan-Evenk) ulus (district) and Ust-Yanskiy region in Yakutia. These areas belonged to the compact residents of the indigenous peoples of the North. The study allowed to determine the attitude of the local population to traditional activities and to identify the socioeconomic problems of the territories and environmental threats to indigenous communities in the context of climate change. In the structure of the respondents in the Anabar area, representatives of indigenous peoples were Evenks 43 people (33%) and Dolgans 71 people (55%) (Figure 7) (Table 2).
\nRatio of men and women in the total number of respondents.
Education organizations, units | \n1735 | \n
Number of medical treatment and prophylactic organizations, units | \n2045 | \n
Number of cultural and leisure type organizations, units | \n834 | \n
Libraries and museums, units | \n542 | \n
Number of sports facilities, units | \n10,161 | \n
Hospitality facilities and accommodation | \n1123 | \n
Shops and supermarket, units | \n28,364 | \n
Restaurants and cafes | \n3773 | \n
Settlements with post office, units | \n1735 | \n
Commissioning of residential buildings, square meters | \n1,496,550 | \n
Number of people living in dilapidated houses | \n192,411 | \n
Extension of a street water supply network, meters | \n7,566,841.0 | \n
Including in need of replacement, meters | \n2,411,098.0 | \n
Number of enterprises for utilization and neutralization of domestic and industrial waste, units | \n151 | \n
Indicators of the social development level of territories of traditional nature use in Siberia and the Far East of the Russian Federation in 2017 [9].
Indigenous community | \nRespondents | \nShare of respondents from the total number, % | \n
---|---|---|
Yuryung-Khaya | \n29 | \n22 | \n
Saskylakh | \n101 | \n78 | \n
Total | \n130 | \n1000 | \n
Distribution of respondents who participated in the survey, by settlements in the district.
It is worth noting that this ratio between men and women, when the number of women prevails, is typical for indigenous communities, since it is associated with the high mortality of men engaged in traditional crafts: hunting, fishing, and reindeer herding. In addition, we can add problems of alcoholism reducing life expectancy, as well as chronic diseases caused by the harsh climate. As a result of the survey, residents of indigenous communities noted the following socioeconomic problems in their places of residence:
High prices for food products, 22.5%
The lack of jobs, 20.2%
Low level of income, 19.7%
Old state of housing and communal services, 19.1%
Poor transport accessibility, 9.0%
Low level of medical services, 6.5%
Low level of equipping educational institutions, 3.1%
As can be seen from the survey results presented, the majority of the respondents connect the socioeconomic problems of the territory with the lack of a stable income, the need for employment, and the underdeveloped infrastructure. In this regard, the implementation of investment projects for the industrial development of territories can create additional jobs for the local population. It should be noted that in the experience of some Russian regions, there are examples of the implementation of a targeted policy for the local labor market development. For example, for several years in the Republic of Sakha (Yakutia), JSC Almazy Anabara (Alrosa group) has been implementing the educational program, which provides training for the company’s interests and the residents of indigenous communities, where an investment project on the extraction of minerals starts. The survey made it possible to determine the list of sociocultural problems that concern the local population:
Increase in morbidity and mortality of the population, 20.7%
Loss of communication between people and their culture, traditions, 18.3%
Alcoholism, 18.3%
The lack of organized forms of leisure, 14.1%
Problems of selling traditional craft products, 12.3%
Outflow of youth, 12.0%
Crime rate, 4.5%
It should be noted that the majority of respondents attributed an increase in morbidity and mortality of the population with active industrial development of territories of traditional nature use. However, these are often only subjective assessments, since the problem of early diagnosis of diseases in the Arctic regions of Russia is particularly acute, and not only instruments and specialists are available in the district centers that could conduct regular medical checkups of the population but even a morgue, i.e., in rural settlements there is no way to establish reliably the cause of death. In most cases, early and sudden deaths, the local population refers to oncological diseases as the consequences of the activity of an industrial enterprise in the territory of their living. In the course of a poll among the inhabitants of indigenous communities, it was found that a high mortality rate is also associated with the problem of alcoholism and crimes committed under the influence of alcohol. The traditional types of economic activity associated with hunting and fishing also endanger life: water safety rules are not followed as well as dealing with weapons.
\nAmong environmental problems, the majority of respondents noted the decline in traditional craft facilities, which is directly attributed to climate change (e.g., the wild reindeer changes its migration routes under the influence of this factor and, as in the case of the Republic of Sakha (Yakutia), goes to the Krasnoyarsk Territory). According to observations of indigenous peoples, winters become warmer, which is expressed in heavy snowfalls and increased winter temperatures. This leads to river spill in spring, flooding of villages, and loss of the fishing opportunity in the traditional way, as the fish goes deeper. Flood threatens another serious problem for traditional craft—broken trees, which the river carries, can break the seines, which means that an indigenous individual and his family can be deprived of food. Many of the representatives of indigenous communities also note the man-made factor—pollution of rivers due to the implementation of industrial projects, shipping, etc.
\nThe Ust-Yanskiy region, the second researched area, has specificity concluded in a huge accumulated damage due to a previous gold extractive mine Kular and closed settlements (Vlasovo, Severniy) caused by mass outflow migration since 1998 when this mine was closed. The barbaric way of extracting gold from only the large and medium fractions, the pursuit of the indicators, led to the fact that there is still enough gold in the recycled dumps that can be produced. Since 2017, the license for processing and restoring Kular mine has been transferred to Arctic Capital LLC, which has undertaken the task of eliminating the accumulated environmental damage, recultivation of soil, employment of the local population among indigenous peoples in the newly discovered deposit, and procurement of traditional products (venison, fish, etc.). The concept of social responsibility of business comes to the Russian part of the Arctic, and it becomes one of the few ways to preserve indigenous community and people on the place of their original habitat (Figure 8).
\nAccumulated environmental damage in Vlasovo, Ust-Yanskiy region, Yakutia (photo: V. Gassiy).
The specificity of the researched territory is its inaccessibility, which has a negative impact on the development of traditional spheres of economic activity. Producing objects of traditional nature use (fish, berries, furs) involves not only consumption for personal purposes but also the need to transport them to the market in larger settlements. The lack of roads and the high cost of transportation by air or auto trucks make economic activity (trade) by-products of traditional nature use almost impossible. In the Ust-Yanskiy area, the main source of income is the extraction of the mammoth tusk, which brings a significant income to the tribal communities and individual entrepreneurs. However, this type of activity requires special training (traditional knowledge, physical form, etc.) and technical equipment (pumps, boats, etc.). Although there are widespread cases of attempts by local residents to obtain tusks and without the necessary equipment, which leads to lethal incidents. On average, according to local residents, the “washing” season is about 100 days, for which one well-trained person can collect from 500 to 800 kg of tusks. In monetary terms, such a “crop” can fluctuate from 10 to 15 million rubles or 160,000–230,000 US$. Moreover, a hot summer with anomalous temperatures is considered by local hunters for tusks as a blessing, since actively melting permafrost itself gives away the hidden remains of ancient animals hidden for thousands of years. It should be noted that in the villages where the main activity is the extraction of the mammoth tusk, one can see expensive modern machinery that local authorities do not always have (Figure 9).
\nType of transport vehicle in a Kazachye indigenous community, Ust-Yanskiy region (photo: V. Gassiy).
The purchased transport equipment allows local residents to develop trade between settlements within the region. Given their remoteness from each other, and the impossibility of year-round traffic, this is an important factor in actually helping people survive in such a harsh terrain. This fact makes indigenous peoples to adapt to the climate change in tundra in a unique way. For example, it is often possible to meet indigenous peoples who are using a winter mode of transport during the summer period, since flooded areas of the tundra do not allow movement on motorized wheeled vehicles, Figure 10.
\nSnowmobile in summer tundra on the way to Khayyr (even community), Ust-Yanskiy region, Yakutia (photo: V. Gassiy).
Figure 10 shows a group of Evens moving on a snowmobile to their native village. In their opinion, in recent years the climate in the tundra has changed considerably: “Winters have become warmer, and summer is unstable: there can be both hot days and cold months when berries do not have time to ripen” (reindeer herder Nikolai, 43); “The deer goes North and does not come here because of the midges, which is very much due to the heat” (hunter Michael, 52) (Figure 11).
\nExample of private household in Kazachye (even community), Ust-Yanskiy region, Yakutia (photo: V. Gassiy).
As a survey of the indigenous community showed, the traditional economy for the majority of local population ceases to be the basic criteria for determining the ethnic characteristics of the people. The high level of unemployment among indigenous peoples of the North, including the Evenks, Evens, and Dolgans, is complicated by the peculiarities of the sectoral structure of employment and the qualification and educational level of the economically active population. The succession of generations in the traditional sectors of the North is gradually disappearing. Young people, being witnesses to the everyday, problematic life of the older generation, are of the opinion that work in reindeer husbandry, hunting, and fishing is not prestigious and does not bring sufficient income to create the corresponding financial situation of the family. The studied living conditions of indigenous communities on the territories of traditional nature use testify to the low level of social, communal, transport infrastructure development, which affects the behavior of the younger generation, their desire to go to the city or find work in extractive companies. “The benefits of civilization” in the form of the Internet, social web sources, and public amenities, along with climate changes, form challenges to the traditional way of life, undermining the age-old foundations of tribal communities. The domestic problems of indigenous peoples are one of the main reasons for the reluctance to remain on their land, to lead a traditional way of life, especially nomadic. Often villages in the territories of traditional residence are not provided with drinking water, and the only sources are river, rain water, or snow (Figure 12).
\nRainwater harvesting for personal consumption, Khayyr (even community), Ust-Yanskiy region, Yakutia (photo: V. Gassiy).
Thus, climate change in the Arctic for indigenous communities is not a prospect of the future, but a real threat to the traditional way of life, food security, and their habitat. We believe that ensuring the social status, decent level, and quality of life of the indigenous communities depends on the ways of preserving and developing the traditional economy on a new material, technical, and technological basis. Market relations in reindeer husbandry and hunting are constrained by the peculiarities of the nomadic way of life and the mentality of indigenous peoples. The theory and practice of managing changes in the territories of the traditional nature use of the Arctic require a critical rethinking of established views. In the coming years, new management approaches will be needed to quickly respond to changes in the Arctic territories, as climate change and global warming lead to the biggest social problem—changing the traditional way of life of indigenous peoples. On the other hand, industrial development expands the area of its presence in the Arctic, which creates not only challenges for the indigenous population but also the opportunities to preserve their culture, traditions, and crafts. In this regard, it is necessary to introduce into the practice of public administration the decision-making model for choosing investment projects based on the priorities of local development, the interests not only of the state and business but also of the indigenous communities [18]. Therefore, in order to solve the problem of survival and adaptation of Arctic indigenous communities in the context of climate change, a proactive reaction of science and practice is needed, based on complex sociological, ethno-cultural, ecological-economic, and statistical studies of traditional nature-use territories.
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