The Algerian economy and electricity generation sector are strongly dependent on fossil fuels. Over 93% of Algerian exports are hydrocarbons, and approximately 90% of the generated electricity comes from natural gas power plants. However, Algeria is also a country with huge potential in terms of both renewable energy sources and industrial processes waste heat recovery. For these reasons, the government launched an ambitious program to foster renewable energy sources and industrial energy efficiency. In this context, steam and organic Rankine cycles could play a crucial role; however, there is a need for reliable and time-efficient optimization tools that take into account technical, economic, environmental, and safety aspects. For this purpose, the authors built a mathematical tool able to optimize both steam and organic Rankine units. The tool, called Improved Rankine Cycle Plant Designer, was developed in MATLAB environment, uses the Genetic Algorithm toolbox, acquires the fluids thermophysical properties from CoolProp and REFPROP databases, while the safety information is derived from the ASHRAE database. The tool, designed to support the development of both RES and industrial processes waste heat recovery, could perform single or multi-objective optimizations of the steam Rankine cycle layout and of a multiple set of organic Rankine cycle configurations, including the ones which adopt a water or an oil thermal loop. In the case of the ORC unit, the working fluid is selected among more than 120 pure fluids and their mixtures. The turbines’ design parameters and the adoption of a water- or an air-cooled condenser are also optimization results. To facilitate the plant layout and working fluid selection, the economic analysis is performed to better evaluate the plant economic feasibility after the thermodynamic optimization of the cycle. Considering the willingness of moving from a fossil to a RES-based economy, there is a need for adopting plants using low environmental impact working fluids. However, because ORC fluids are subjected to environmental and safety issues, as well as phase out, the code also computes the Total Equivalent Warming Impact, provides safety information using the ASHRAE database, and displays an alert if the organic substance is phased out or is going to be banned. To show the tool’s potentialities and improve the knowledge on waste heat recovery in bio-gas plants, the authors selected an in-operation facility in which the waste heat is released by a 1 MWel internal combustion engine as the test case. The optimization outcomes reveal that the technical, economic, environmental, and safety performance can be achieved adopting the organic Rankine cycle recuperative configuration. The unit, which adopts Benzene as working fluid, needs to be decoupled from the heat source by means of an oil thermal loop. This optimized solution guarantees to boost the electricity production of the bio-gas facility up to 15%.

The present work deals with the deployment of an air bottoming cycle as a technology for thermal energy valorization. This solution is integrated within the preheater tower on an Al-gerian cement plant. A combined MATLAB- Coolprop optimization tool has been developed to carry out a thermo-economic calculation allowing to design and optimize the air bottoming cycle and also check its economic returns. The developed code employs the genetic algorithm through a multi-objective function aiming to maximize the cycle’s net power output as a pri-ority objective, then minimize the heat exchanger’s area of exchange, and also maximize the cycle’s net present value. through the implemented models on it, the code gives the ability to confirm the applicability of this technology through the Algerian market which is character-ized by one of the cheapest prices of electricity in the world that doesn’t exceed 0.040 $ kWh-1. The obtained results highlight that the implementation of such technology for energy valori-zation purposes from the preheater tower of the selected cement plant can be a profitable and attractive solution, particularly in scenarios of water scarcity. Since the implementation of this technology presented a power capacity of 1.2 MW covering then around 7.8% of the electricity demand of the investigated cement plant. The economic analysis of the proposed ABC cycle pointed out a net present value of 6.59 M$, and a payback time less than 3.6 years, besides a Levelized cost of energy less than 0.017 $ kWh-1 which is a comparable value to the subsidized prices of electricity in the Algerian market.

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This work evaluated the air bottoming cycles(ABC) as a technology for waste heat recovery (WHR) at the level of the preheater tower in a cement industry. An optimization code has been developed in MATLAB environment and linked with REFPROP database as a way to design and calculate the different parameters and points of the cycle. The theory of power maximization is adopted and the genetic algorithm is employedasa way to maximize the net power output of the cycle, while a case study of a real cement plant has been taken into consideration for the examination purpose. Results showed that the integration of the ABC cycle for energy valorization contributes to covering around 8.5% of the industry need for electrical energy, by generating an amount of power that can achieve 1.07 MW.In addition, although the cycle has shown a low efficiency, it can be a practical WHR solution especially in case of water deficiency.