Climate change and the increase of the consumption of energy resources are expected to further strain anticipated water stress scenarios. The operation of existing thermal plants depends greatly on their cooling capacity, for which large amounts of water are withdrawn and consumed. Dry-cooling systems, on the other hand, do not require water, but they are less efficient and more expensive relative to conventional water-based systems, because of their dependency on the ambient temperature. This paper introduces the new idea of replacing water-based cooling systems in thermal power plants with earth-cooling air tunnels. Based on the concept of existing earth-air heat exchangers, the system takes advantage of the low and relatively constant underground temperature for cooling ambient air before it is introduced in the air condenser of the plant. In this work, we present an initial design of such an open-loop system for a 20 MW concentrated solar power plant. A sensitivity study of both geometric and flow parameters is realized using computational fluid dynamics simulations. Under the requirements of the study, we find that a system using a design of pipes with 0.5 m diameter and about 300 m length can be considered a technically viable zero-water alternative to water-cooling technologies.
Water dependency of power plants undermines energy security by making power generation susceptible to water scarcity. This study evaluates the economic performance of a novel dry-cooling system for a water-independent solar power plant. The proposed cooling system is based on the concept of earth–air heat exchangers, approaching zero environmental impact. The viability of the proposed design is discussed based on both costs and benefits, and it is compared to both conventional dry- and wet-cooling systems. The installation costs of the plant are found to be EUR 13,728/kW, resulting in the substantial levelized cost of electricity of EUR 505.97/MWh. The net present value of the studied design assuming a water-cost saving of EUR 1/m3 is found to be MEUR –139.59. Significantly higher water prices in the future might eventually make the proposed system economically attractive when compared to water-cooling systems. However, the new system would require drastic modifications to become more attractive when compared to existing dry-cooling systems. Specific possibilities to improve it for zero-water use in thermoelectric power plants are further discussed.
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