a b s t r a c tThis two-part paper proposes an approach based on state-of-the-art numerical optimization methods for simultaneously determining the most profitable design and part-load operation of Combined Heat and Power Organic Rankine Cycles. Compared to the usual design practice, the important advantages of the proposed approach are (i) to consider the part-load performance of the ORC at the design stage, (ii) to optimize not only the cycle variables, but also the main turbine design variables (number of stages, stage loads, rotational speed). In this first part (Part A), the design model and the optimization algorithm are presented and tested on a real-world test case. PGS-COM, a recently proposed hybrid derivative-free algorithm, allows to efficiently tackle the challenging non-smooth black-box problem.

No abstract

Cyclic adsorption processes for gas separation, such as pressure and temperature swing adsorption (PSA and TSA), are non-stationary multi-column processes. Their design involves many degrees of freedom, which offers a very high flexibility while calling for a systematic and rigorous optimization approach. As an additional challenge, optimization of these separation processes involves multiple objectives, e.g. minimal energy demand and maximal productivity, which have to be pursued while fulfilling given process specifications, e.g. purity and recovery of the target components. This work extends the multilevel coordinate search (MCS), a well-known model-based derivative free algorithm, to constrained multiobjective problems. The algorithm, called MO-MCS, combines a built-in parallel computing strategy with the use of look-up tables with the goal of minimizing the computational time needed to determine the Pareto curve. The comparison with state-of-the-art optimizers indicates that MO-MCS shows better performance in terms of optimality, well spacing and extension of the Pareto curve. Afterwards, two industrially relevant case studies (TSA for CO2 separation and PSA for H2 and CO2 co-production) are tackled to demonstrate the effectiveness of the algorithm as a tool to guide the design of adsorption processes.

a b s t r a c tThis two-part paper proposes an approach based on state-of-the-art numerical optimization methods for simultaneously determining the most profitable design solution and part-load operation of Combined Heat and Power Organic Rankine Cycles. Compared to the usual design practice, the important advantage of such an approach is to consider the part-load performance of the Organic Rankine Cycle at the design stage. In this second part (Part B), first the part-load model and optimization algorithm are presented and tested. Then, the part-load optimization algorithm is combined with the design optimization algorithm proposed in Part A, and the simultaneous approach is applied to a real-world test case. Computational results show that, with respect to a design optimized for full-load equivalent hours, the solution optimized for part-load operation has a lower investment cost, better part-load efficiencies, and thus up to 22% higher annual profit. The optimized part-load control strategy uses the sliding-pressure mode in the high-load range, and a combination of sliding-pressure and throttling in the low-load range.