A unique ocean and solar based multigenerational system with hydrogen production and thermal energy storage for Arctic communities

Arctic regions have been experiencing some drastic effects of climate change ever, which are more intense than what the rest of the globe faces. In polar regions, the temperature is increasing almost two times the global average. Although thawing permafrost can increase the farmland area by shifting the southern limit of the arctic permafrost into the northward, increasing the darker land area and ocean surfaces causes higher radiation absorptivity, therefore, higher warming effect on the arctic regions [1]. Global climate change and arctic warming exacerbate food insecurity for arctic communities. The declining wildlife populations and sea-ice-dependent animal populations, such as seals, walrus and marine birds make Arctic hunting harder for people, which are recognized as a major threat to food security and the Indigenous culture [2].

Northern territories of Canada are home to many isolated communities where diesel-based energy infrastructure is very common. Although the intermittent characteristic of PV technologies prevents to replacement of diesel-based infrastructure with PV alone, such PV systems help significantly reduce the diesel fuel dependence which brings high environmental impact and high operational cost [3]. Singh [4] observed two photovoltaic arrays in Iqaluit, Canada, which is an arctic environment, in order to provide insightful details about temperature and albedo effects on PV array. Higher albedo and lower temperatures lead to higher energetic and exergetic efficiencies for PV arrays. Although Arctic regions have less solar intensity compared to the rest of the globe, those regions have lower temperatures and higher albedo due to the snow-covered grounds. Fresh and aged snow has a high albedo between 0.6 and 0.9 Bifacial-type PV modules that can significantly increase the collected radiation by using the back surface to collect the reflected radiation. In a recent study, the impact of the environmentally effective albedo is investigated on the performance of the bifacial PERC + solar cells by Mekemeche and Beghdad [5]. They showed that the albedo affects the output power linearly. In their simulations, the output power is increased 43% from green grass (0.24 albedo) to snow (0.85 albedo). Longer snow cover duration leads to higher yields. Therefore, the arctic regions are beneficial for bifacial PV systems regarding the high number of snow cover days.

On the other hand, arctic regions have higher heating demands regarding the low ambient temperatures. Concentrated solar plants (CSP) are directly utilized to convert solar irradiation into heat. This reduces conversion losses compared to PV-based systems, where conversion of the irradiation occurs indirectly via electricity. Unlike the PV systems, CSP technology has disadvantages in arctic environments due to lower irradiation and lower temperatures in comparison to the rest of the globe. Among the CSP technologies, parabolic trough collector (PTC) type systems are more suitable for cold environments due to their small external surface, which reduces the heat losses, concentrating irradiation by focusing the light through parabolic mirrors, and their vacuum annulus, which reduces the heat losses. The parabolic shape of the mirrors concentrates the solar irradiation to generate medium or high-grade heat, over 150 °C in most cases [6]. High-grade heat can cause thermal pollution, which is very crucial since the rapidly warming Arctic melting have connections with jet streams [7,8]. However, the vast majority of the current energy infrastructure of Nunavut territory is based on diesel combustion, which can create or exhaust 800 °C heat. Therefore, the thermal pollution can be reduced with PTC type CSP systems regarding its lower heat losses due to lower grade heat usage compared to the current energy infrastructure.

OTEC is another promising renewable energy technology that can be used in an arctic environment. OTEC systems can exploit the temperature difference between the air ambient temperature and ocean/water temperature. Although the energy source is almost unlimited, the conversion efficiency is lower compared to other renewable energy conversion methods. A practical study [9] showed that the maximum theoretical energy efficiency of OTEC systems is 9.2%; therefore, practical systems should possess lower energy efficiencies. Ammonia is proposed as one of the alternative heat transfer fluids for OTEC systems. The trilateral ammonia Rankine cycle can exploit the energy in lower temperatures compared to the water-based Rankine cycle [10].

Renewable resources are intermittent; therefore, a continuous and reliable energy supply requires an additional energy medium. Diesel is the current energy medium that can be transported via cargo ships or can be stored. Hydrogen is recognized as an environmentally friendly alternative fuel and energy storage medium which can easily be produced from water using electricity and other environmentally benign drivers, such as heat, light and biological and chemical processes . Hydrogen can be used as a sustainable transportation fuel, energy storage medium, and energy transmission medium by the arctic communities. Moreover, hydrogen is a feedstock for various industrial processes as well. It can be produced during the off-peak times; therefore, the production of waste can be eliminated by producing useful output. Fuel cells or internal combustion engines can be used to generate electricity or mechanical energy for various purposes [11].

Further to note that the Polar regions are not rich in terms of solar energy resources. Therefore, integrated multigenerational systems can be beneficial in order to exploit available resources to generate various commodities. Recently, Ishaq et al. [12] studied the integration of wind, solar, and ocean-based hydrogen, electricity, and freshwater production system with OTEC and Cu–Cl cycle. They determined 45.3% energy and 44.9% exergy efficiencies in trigeneration mode. Wang et al. [13] studied techno-economic assessment of OTEC system where organic Rankine cycle is used. They have found levelized cost of electricity (LCOE) and exergy efficiency results for R717, R152a, R134a, R227ea, R699a, and R601 working fluids. R717 and R601 working fluids performed the best results with $0.34/kWh LCOE and 28.17% exergy efficiency for R717, and with $0.52/kWh LCOE and 28.47% exergy efficiency for R601, according to their Pareto optimal solution. Zhou et al. [14] have analyzed a novel OTEC-based trigenerational system with energetic, exergetic, and exergoeconomic approaches. They have found 29.33% exergy efficiency for their proposed system where freshwater, electricity, and cooling are generated. Hasan and Dincer [15] investigated a novel OTEC-based trigeneration system for ammonia, electricity, and cooling generation. Two cases with ammonia production during the off-peak times in the first case and complete power production during the peak times in the second case are investigated. 1.37% energy and 56.1% exergy efficiencies are indicated according to the results for the first case. Energy and exergy efficiencies are found to be 1.83% and 78.02%, respectively, for the second case. In a recent study, Khosravi et al. [16] economically and thermodynamically analyzed an OTEC and solar-based system with hydrogen energy storage. For their integrated system, the overall energy and exergy efficiencies are calculated as 3.32% and 18.35%, respectively. Their economic analysis showed that their proposed system's payback period is found to be eight years, where the unit electricity cost is calculated as 0.168$/kWh. In a recent study by Olabi et al. [17], waste-heat-driven desalination systems are discussed. In order to increase the efficiency of multigenerational systems and to decrease the environmental impacts and carbon footprint, waste-heat driven desalination systems can be implemented. There is a large amount of waste heat generation is available in the current global energy infrastructure, and it can be exploited to turn the multigenerational systems into more economically and environmentally favorable systems. Lourenco and Carvalho [18] showed the potential of desalination systems with a case study; a desalination system integrated electricity generation system can satisfy 70% of the water demand of a municipality. Temiz and Dincer [19] carried out a techno-economic assessment for a CSP and geothermal system with thermal energy storage and desalination systems for electricity, freshwater, hydrogen, and heat generation purposes. Their proposed system's overall energy and exergy efficiencies are found to be 27.4% and 17.3%, respectively. In another study, Luqman et al. [20] thermodynamically investigated a solar-based multigenerational system with a thermal desalination process. PTC type CSP systems and thermal energy storage systems are used with a pressure retarded osmosis unit to provide electricity, cooling, and freshwater. Their proposed system's overall energy and exergy efficiencies are found to be 34.54% and 14.55%, respectively.

In this study, an innovative OTEC and solar-based energy, food, water and fuel generating system with hydrogen producing and deploying systems and thermal energy storage option is developed to combat Arctic communities' energy and food insecurity in polar regions. Cascaded heat pump, OTEC, trilateral Rankine cycle, CSP, BiPV, molten salt two tanks thermal energy storage, multi-effect desalination, PEM electrolyzer, PEM fuel cell systems are integrated to produce heating, electricity, domestic hot water, freshwater, hydrogen fuel, and food for the community, in an environmentally benign manner. The proposed system is extensively analyzed with various methods and software. Commercially available components are considered in calculations for solar systems. CSP and BiPV plants are simulated via National Renewable Energy Laboratory (NREL) ‘s System Advisor Model (SAM) [21] and PVSyst [22]. Simulation and meteorological data are obtained for hourly calculations. The overall system, subsystems, and components are thermodynamically analyzed via energy and exergy approaches. Different input parameters for each hour of an average year are considered for dynamic analyzes.