Robust and adaptive control strategies for closed-loop climate engineering

Bonetti, Federica (2019) Robust and adaptive control strategies for closed-loop climate engineering. PhD thesis, University of Glasgow.

Abstract

Climate engineering aims to offset human-driven climate change through engineering interventions. This thesis focuses on the deployment of Solar Radiation Management (SRM) methods which aim to counteract radiative forcing generated by the concentration of atmospheric CO2. The climate system is investigated as a closed-loop control problem with uncertainties in its dynamics mitigated by robust and adaptive control strategies. Indeed, an adaptive controller for climate engineering is presented for the first time in a multi-variable control scheme. A low order three-box energy model is developed for the climate system to investigate such adaptive control strategies. Climate engineering measures are then deployed in 3 boxes, thus representing northern, southern and central (equatorial) bands. It is demonstrated that, through the on-line estimation of the controller parameters, adaptive control can overcome key-issues related to uncertainties of the climate model, external radiative forcing and actuator dynamics. The use of adaptive control provides a robust means of dealing with unforeseeable abrupt perturbations and the parametrisation of the model considered, while still providing bounds on stability and control performance. Importantly, the convergence of the controller is guaranteed through the Lyapunov stability criterion. Moreover, an analytical model describing the main latitudinal dynamics of the Earth’s climate with closed-loop control has been developed. This model has analytical solution and allows for quick evaluations of non-uniform climate engineering strategies. Multi-objective analyses are considered and analytical expressions for control laws with latitudinal resolution are obtained in several scenarios. Results are broadly comparable with the literature, demonstrating model’s utility in rapidly assessing climate engineering controls laws. Using the PDE model, ice line dynamics are investigated and a Lyapunov stability analysis is employed to estimate the maximum insolation reduction before the current climate falls into an ice-covered state. This provides an extreme operational boundary for future climate engineering ventures. Finally, the PDE model is employed to investigate strategies involving the deployment of space shields. The grade of obscuration provided at each latitude is estimated and an optimization process performed in order to minimize the shield size and to find the ideal orbit to counteract 2xCO2 concentration.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Climate engineering, climate change, control theory, Solar Radiation Management, space mirror, solar sails, Lyapunov stability.
• Subjects: G Geography. Anthropology. Recreation > G Geography (General); G Geography. Anthropology. Recreation > GE Environmental Sciences; T Technology > TL Motor vehicles. Aeronautics. Astronautics
• Colleges/Schools: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Supervisor's Name: McInnes, Professor Colin
• Date of Award: 2019
• Depositing User: Dr. Federica Bonetti
• Unique ID: glathesis:2019-74275
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 01 Jul 2019 15:03
• Last Modified: 05 Mar 2020 22:37
• Thesis DOI: 10.5525/gla.thesis.74275
• URI: https://theses.gla.ac.uk/id/eprint/74275