Annual performance of a novel configuration for an integrated solar combined cycle utilising municipal solid waste

Sansom, Christopher L. - Associate Supervisor

Climate change has been a major incentive for the global power generation industry to move towards the implementation of sustainable renewable energy technologies in order to reduce the emissions of greenhouse gases, especially carbon dioxide emissions. Concentrated solar power (CSP) has established itself as one of the common renewable energy technologies for large scale power generation. A further attractive feature of this solar technology is its hybrid operation in the form of integrated solar combined cycle (ISCC) which facilitates control and ensures that the power plant is available to meet demand whenever it occurs. ISCC commonly uses natural gas to operate the combined cycle but this CSP hybrid system also has the potential to limit its use of this fossil fuel with a more environmentally friendly fuel, namely the produced syngas from solid feedstock gasification which can be accomplished by further integration of the gasification reactor with ISCC. The organic fraction of municipal solid waste (MSW) was selected for this application, both to replace natural gas as well as for its value as a waste management method. In the present work, the thesis studies and contrasts four configurations of ISCC based on two factors, the type of fuel and the level of solar thermal contribution. One configuration represents the conventional form by using natural gas (ISCC 1) while another configuration uses municipal solid waste (ISCC 2) and in both cases, the solar field generates high -pressure saturated steam using parabolic trough with thermal oil. The last two configurations are related to the research proposal for ISCC which states that this hybrid system runs on municipal solid waste and utilises enhanced solar thermal contribution. This enhanced thermal power from the solar field is used to generate high-pressure superheated steam using parabolic trough with molten salt (ISCC 3) or solar power tower with molten salt (ISCC 4). In all cases, the fuel runs the combined cycle, and the solar field operates in parallel to provide extra steam for the hybrid system. However, the use of gasification in ISCC 2, ISCC 3 and ISCC 4 generates extra steam for the hybrid system through syngas cooling system which is attached to the low-pressure section of the steam turbine cycle. In this work, models are developed to investigate the differences between the various configurations in terms of technical and economic performances using Spain and Saudi Arabia as case studies. The results indicate that the use of a solar power tower in the proposed concept, ISCC 4, gave the highest electricity production at 646 GWh with a solar share of 12.80% under Spanish weather and 644 GWh with a solar share of 15.24% under the Saudi Arabian weather. Furthermore, ISCC 4 offered the lowest levelised cost of electricity at 28.45 $/MWh and 28.62 $/MWh for Saudi Arabia and Spain, respectively, when the novel concept (ISCC 3 and ISCC 4) is compared to the conventional concept (ISCC 1). The main thesis contribution was to reveal the impact of coupling the ISCC using enhanced solar thermal power with municipal solid waste gasification and its potential as Waste-to-Energy plant. Based on the study presented outcomes, The proposed concept of integrated solar combined cycle (ISCC 3 and ISCC 4) demonstrated its practicality against conventional concept (ISCC 1) due to achieving higher performance outcomes with lower costs. The outcomes of ISCC 2 in both countries presented slightly lower LCOE values than the novel concept indicating that the replacement of fuel alone did not show a significant impact against the novel concept in terms electricity production cost.

PhD in Energy and Power