The natural gas-absorption method system as an alternative to the electric power-mechanical compression system in Spain

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In any energy transformation system, thermodynamical, ecological and economic factors must be considered. However, any one of these, taken separately, is insufficient to make a final decision on the feasibility of substituting one system for another. Our study is focused on finding an analytical framework which might serve as a decision-making instrument for the profitability of absorption-compression systems fed by natural gas (ACNG). To do this, it is necessary to estimate the replacement capacity of these over mechanical compression systems fed by electric power (MCEP), and under what circumstances the probabilities of operational success or failure can be foreseen. The advantages inherent in ACNG systems in Spain are the low cost of natural gas and the uninterrupted use of this fuel, which can be used for both heating and cooling of buildings. Their main handicap is based on the supposition of an insurmountable difference between the energy efficiency of absorption cycles and mechanical compression. However, bearing in mind the conversion efficiency of one cycle or the other from the primary energy source (natural gas to heat and to electricity, respectively), the actual efficiencies of complete transformation from fuel to cold are not all that different. Lithium bromide absorption water condensated COP e = 0.56 Alternative mechanical compression water condensated COP e = 0.96 Centrifugal mechanical compression water condensated COP e = 1.2. From an ecological point of view, in addition to the substitution of R11 with R123, it is necessary to evaluate the effective destructive potential of R22 on the ozone layer and its impact on the greenhouse effect. While the two R22 indexes reflect an improved performance with respect to R11, the effective incidence is hidden. The working pressure of the refrigerant, higher for R22, can compensate for the greater number of chlorine atoms in R11 molecules. In the economic domain, ACNGs can be relatively competitive systems in Spain in comparison to MCEPs. The COP e of mechanical compression, the price of an electric kWh and the difference in initial investments between ACNG systems and MCEP systems are shown in our study as the three most decisive variables in determining the profitability of the former over the latter.