A widely-proposed way to retrofit coal-fired power plants with post-combustion CO2 capture (PCC) is to supply all the electricity and heat required to operate the capture equipment from the existing steam cycle (an ‘integrated retrofit’), at the expense of a reduction in site power output. As an alternative, it is possible to add a gas turbine (GT) plant to maintain, or even increase, the net site power output. The GT can be integrated with the capture plant in various ways to supply all or part of the heat and power required for the capture and compression systems. But there is then the issue of how to capture the CO2 emissions from the added GT plant. In this study a novel retrofit configuration is proposed. The exhaust gas of the GT replaces part of the secondary air for the coal boiler and a common capture system is used for both coal- and natural gas-derived CO2. This new ‘GT flue gas windbox retrofit’ is based on the principles of previous hot windbox repowering proposals, with additional modifications to permit operation without extensive coal boiler modifications. To achieve this, the heat recovery steam generator (HRSG) attached to GT is designed to maintain the main steam turbine flow rates and temperatures, to compensate for a necessary reduction in coal feed rates, and this, with the GT output, maintains the net power output of the site A techno-economic analysis of coal plants retrofitted with GT power cycles shows that these ‘power matched’ retrofits can be competitive with integrated retrofits at lower natural gas prices (as is now the case in North America). In particular, the novel GT flue gas windbox retrofit provides a promising alternative for adapting integrated capture retrofits that are initially designed for flexible operation with zero to full (~90%) capture (as at the Boundary Dam 3 unit) for subsequent operation only with full capture. In this case the addition of a GT flue gas windbox retrofit will restore the full power output of the site with full CO2 capture and using the original capture plant. In general, techno-economic analysis shows that the economic performance of GT retrofit options depends on the site power export capacity. If there is no limit on power export then retrofits may advantageously also include an additional steam cycle, to give a combined cycle with the GT, otherwise retrofits with a single pressure HRSG producing process steam only are preferred.

The rapid electrification through natural gas in Mexico; the interest of the country to mitigate the effects of climate change; and the opportunity for rolling out Enhanced Oil Recovery at national level requires an important R&D effort to develop nationally relevant CCS technology in natural gas combined cycle power plants. Post-combustion carbon dioxide capture at gas-fired power plants is identified and proposed as an effective way to reduce CO2 emissions generated by the electricity sector in Mexico. In particular, gas-fired power plants with carbon dioxide capture and the sequential combustion of supplementary natural gas in the heat recovery steam generator can favourably increase the production of carbon dioxide, compared to a conventional configuration. This could be attractive in places with favourable conditions for enhanced oil recovery and where affordable natural gas prices will continue to exist, such as Mexico and North America. Sequential combustion makes use of the excess oxygen in gas turbine exhaust gas to generate additional CO2, but, unlike in conventional supplementary firing, allows keeping gas temperatures in the heat recovery steam generator below 820°C, avoiding a step change in capital costs. It marginally decreases relative energy requirements for solvent regeneration and amine degradation. Power plant models integrated with capture and compression process models of Sequential Supplementary Firing Combined Cycle (SSFCC) gas-fired units show that the efficiency penalty is 8.2% points LHV compared to a conventional natural gas combined cycle power plant with capture. The marginal thermal efficiency of natural gas firing in the heat recovery steam generator can increase with supercritical steam generation to reduce the efficiency penalty to 5.7% points LHV. Although the efficiency is lower than the conventional configuration, the increment in the power output of the combined steam cycle leads a reduction of the number of gas turbines, at a similar power output to that of a conventional natural gas combined cycle. This has a positive impact on the number of absorbers and the capital costs of the post-combustion capture plant by reducing the total volume of flue gas by half on a normalised basis. The relative reduction of overall capital costs is, respectively, 9.1% and 15.3% for the supercritical and the subcritical combined cycle configurations with capture compared to a conventional configuration. The total revenue requirement, a metric combining levelised cost of electricity and revenue from EOR, shows that, at gas prices of 2$/MMBTU and for CO2 selling price from 0 to 50 $/tonneCO2, subcritical and supercritical sequential supplementary firing presents favourably at 47.3-26 $/MWh and 44.6-25 $/MWh, respectively, compared with a conventional NGCC at 49.5-31.7 $/MWh. When operated at part-load, these configurations show greater operational flexibility by utilising the additional degree of freedom associated with the combustion of natural gas in the HRSG to change power output according to electricity demand and to ensure continuity of CO2 supply when exposed to variation in electricity prices. The optimisation of steady state part-load performance shows that reducing output by adjusting supplementary fuel keeps the gas turbine operating at full load and maximum efficiency when the net power plant output is reduced from 100% to 50%. For both subcritical and supercritical combined cycles, the thermal efficiency at part-load is optimised, in terms of efficiency, with sliding pressure operation of the heat recovery steam generator. Fixed pressure operation is proposed as an alternative for supercritical combined cycles to minimise capital costs and provide fast response rates with acceptable performance levels.

Power dissipated during scan testing is becoming increasingly important for today’s very complex sequential circuits. It is shown that the power dissipated during test mode operation is in general higher than the power dissipated during functional mode operation, the test mode average power may sometimes go upto 3x and the peak power may sometimes go upto 30x of normal mode operation. The power dissipated during the scan operation is primarily due to the switching activity that arises in scan cells during the shift and capture operation. The switching in scan cells propagates to the combinational block of the circuit during scan operation, which in turn creates many transition in the circuit and hence it causes higher dynamic power dissipation. The excessive average power dissipated during scan operation causes circuit damage due to higher temperature and the excessive peak power causes yield loss due to IR-drop and cross talk. The higher peak power also causes the thermal related issue if it last for sufficiently large number of cycles. Hence, to avoid all these issues it is very important to reduce the peak power during scan testing. Further, in case of multi-module SoC testing the reduction in peak power facilitates in reducing the test application time by scheduling many test sessions parallelly. In this dissertation we have addressed all the above stated issues. We have proposed three different techniques to deal with the excessive peak power dissipation problem during test. The first solution proposes an efficient graph theoretic methodology for test vector reordering to achieve minimum peak power supported by the given test vector set. Three graph theoretic problems are formulated and corresponding algorithms to solve the problems are proposed. The proposed methodology also minimizes average power for the given minimum peak power. Further, a lower bound on minimum achievable peak power for a given test set is defined. The results on several benchmarks show that the proposed methodology is able to reduce peak power significantly. To address the peak power problem during scan test-cycle (the cycle between launch and capture pulse) we have proposed a scan chain reordering technique. A new formulation for scan chain reordering as TSP (Traveling Sales Person) problem and a solution is proposed. The experimental results show that the proposed methodology is able to minimize considerable amount of peak power compared to the earlier proposals. The capture power (power dissipated during capture cycle) problem in testing multi chip module (MCM) is also addressed. We have proposed a methodology to schedule the test set to reduce capture power. The scheduling algorithm consist of reordering of test vector and insertion of idle cycle to prevent capture cycle coincidence of scheduled cores. The experimental results show the significant reduction in capture power without increase in test application time.