Thermal power plants usually refer to those large power plants that typically use coal, and in some cases natural gas. A nuclear power plant is also a thermal power plant (and so is a solar thermal power plant), but the power industry usually implies coal or natural gas powered plants when referring to thermal power plants.
Only those thermal power plants that use fossil fuels such as coal or natural gas give out CO2 emissions. (Nuclear or solar based thermal power plants give out no CO2 emissions during their operations).
CO2 emissions from these fossil fuel based thermal power plants can be reduced by tweaking things prior to or during combustion, or post combustion.
Of special interest is reducing CO2 emissions from coal based power plants, as these emit the highest amount of CO2 per unit of energy, typically measured in Kg of CO2/kWh of electrical energy generated.
What are the efforts being undertaken to reduce the CO2 emissions from fossil fuel based thermal power plants?
The efforts can be divided broadly into two categories:
- Efforts prior to combustion and during combustion
- Efforts post combustion
Efforts for Pre-combustion & Combustion Stages – Today, a range of technologies is being used pre-combustion (before the coal enters the combustion chamber) and during combustion to significantly increase the efficiency. An increase in efficiency of power generation implies use of less coal for a unit of energy, which translates to less CO2 emitted per unit. Many of these efforts have to do with both the way coal is processed before it enters the combustion chamber (through coal pulverisation, gasification etc), and improvements in boiler design.
Efforts to Reduce CO2 Emissions to Atmosphere Post Combustion – Once the CO2 has been emitted, the only known way to lessen its negative impact is to capture it and not allow it to escape to the atmosphere. In this context, the main avenue currently being pursued is carbon capture and storage (CCS), in which the emitted CO2 is captured and stored such that it is not released to the atmosphere. Different solutions are being tried out both for carbon capture and for its storage. Compared to the fairly commercial pre-combustion and combustion solutions mentioned earlier however, CCS is a nascent field and there are very few, if any, commercial scale CCS facilities in the world as of 2016.
Some years back, I was fascinated with CCS as I felt this could buy us at least 30-40 years. With this in mind, I even put up a web resource Power Plant CCS. Since then, unfortunately, the progress in this field has in terms of commercial deployment has been quite slow.