GALINI: Global ALgorithms for mixed-Integer Nonlinear optimisation of Industrial systems

At the 2015 Paris climate conference, 195 countries agreed that global greenhouse gases should peak as soon as possible and that countries should thereafter rapidly reduce their emissions. The process industries must therefore reduce their energy consumption and increase efficiency while maintaining consumer services. Next generation decision-making software at the interface of engineering, computer science, and mathematics is critical for these efficient systems of the future. Already, state-of-the-art computational packages are routine in the process industries; practically every major company uses simulation and optimisation to model production in different modes including: continuous, batch, and semi-continuous production systems. But more efficient industrial systems require simultaneously considering many tightly integrated subsystems which exponentially increase complexity and necessitate many temporal/spatial scales; the resulting decision making problems may not be solvable with current techniques. Increasing efficiency may also jeopardise safety: the process integration required for efficiency implies interchanging heat between processes and may damage safety precautions by transferring disturbances across a plant.

During this fellowship, we propose to develop GALINI, new decision-making software constructing and deploying next generation process optimisation tools dealing with combinatorial complexity, disparate temporal/spatial scales, and safety considerations. The GALINI project proposes step-changes in optimisation algorithms that are immediately applicable to efficiency challenges in process systems engineering (PSE): safely operating batch reactors, retrofitting heat-exchanger networks, intermediate blending, and integrating planning and scheduling. We will freely release our software on open-source platform Pyomo and build an international user community.

The primary GALINI research aim is to develop optimisation software that pushes the boundary of computational tractability for PSE energy efficiency applications. Effective optimisation software in the process industries answers: How can we best achieve a definite engineering objective? Given constraints such as an existing plant layout or a contractual obligation to produce specific products, the software supports novel engineering by quantitatively comparing the implications of different options and identifying the best decision. GALINI is particularly interested in design: How should we build new facilities or modify existing ones to achieve our design goals with maximum efficiency?

The state-of-the-art in decision making for the process industries is represented by commercial modelling software such as AspenTech and gPROMS. Practically every major company in the process industries uses these software tools since the outputs of the simulation or optimisation can be implemented with minimal day-to-day operational disruption and savings can be realised with a payback time as short as 6-12 months. GALINI will develop deterministic global optimisation software for mixed-integer nonlinear programs, a type of optimisation problem highly relevant to energy efficiency and process systems engineering. Energy efficiency instances may exhibit the mathematical property of nonconvexity, i.e. have many locally optimal solutions; global optimisation mathematically guarantees the best process engineering solution. GALINI proposes transformational shifts in algorithms that creatively reimagine the core divide-and-conquer algorithm typically applied to this type of optimisation problem. Our approach is to freely release GALINI to users including those in the process industries, publicise the software, demonstrate its utility, and build a user community that will feed back into software development.

The GALINI fellowship will positively impact a wide variety of groups beyond the academy, both in the UK and internationally. Here we summarise the impact on: the process industries, solver software developers, policy makers, schools, and the wider public.

Process Industry:

+ The novel engineering research into retrofitting heat exchangers, integrating planning and scheduling, and safely operating batch reactors have immediate, domain specific benefits for the process industries;
+ The advanced decision making tool GALINI can better help the process industries increase energy efficiency and profitability;
+ We are partnering with several software vendors working with the process industries, so advances will be available either through our own GALINI code base or through parts of the research that the project partners chose to pick-up and distribute in their own venues.

Solver Software Developers:

+ We are making our code open-source, so all or part of it may feed into future open-source or commercial optimisation software;
+ We are developing fundamental new algorithms that will drive the state-of-the-art and will encourage more companies to move into this domain.

Policy & Other Decision Makers:

+ Our code will be freely available to policy and decision makers from around the world;
+ GALINI will be able to ask the question "What is it that we need to guarantee the objective that we want?" and will be able to identify gaps where, for example, no existing technology cannot reach a certain engineering objective. This may help guide polices;
+ GALINI will also be able to identify when an energy efficiency policy should be possible for engineering, this could help policy makers choose regulatory structures.

Schools & Wider Public:

+ We will attract advanced undergraduates to our work by allowing them to participate in the user workshops that we will run throughout the UK;
+ We will communicate our work to the general public via events such as Royal Society Summer Science Exhibition and Imperial Festival.

The primary activities for the proposed GALINI fellowship are research software development, novel algorithms, and new engineering research. But we will also release GALINI to process industries users, publicise the software, demonstrate its utility, build a user community that will feed back into software development, and communicate our work with the general public. The Pathways to Impact document explains how we will accomplish these plans.