Repurposing coal-fired power plants: benefits and challenges
There are currently more than 8,500 coal-fired power plants throughout the world with a capacity to generate approximately 2,000 GW of electric power . In North America, there are over 220 coal-fired plants with a capacity to generate approximately 220 GW of electricity [2,3]. This was approximately 23% of the total electricity generation capacity in the region in 2021.
Unfortunately, coal-fired power plants emit substantial amounts of particulate matter; greenhouse gases (GHG) including carbon dioxide, sulfur dioxide, and other contaminants negatively affect our health and our environment. Despite this, 1,400 GW of coal-fired power generation capacity has been added to the world’s power generation output since the year 2000. These are considered relatively new facilities with significant remaining life. . Additionally, these are base load plants, a key benefit in being able to meet power demands, whereas most commercially available green solutions, like solar or wind, are intermittent and cannot meet base load demand. It is considered impractical to retire relatively new facilities that produce one-third of the world’s electric power or to replace them with intermittent cleaner generating units.
A better solution is to repurpose these plants where possible—an approach that will ensure the continued fulfillment of our energy needs with less capital investment while significantly reducing CO2 and other harmful constituents.
Converting coal-fired plants to biomass fuel
Biomass fuel is considered carbon neutral and presents an alternative solution to coal firing. Switching fuel from coal to biomass will allow coal-fired power plants to continue to operate and requires the fewest modifications to the power plant. The entire fuel storage, reclaiming, conveyor system, coal bunkers, pulverizers, and burners can be repurposed to accommodate biomass with minor modifications. This type of conversion has been successfully implemented at utility-scale power plants.
Challenges to the conversion include the high volatility of biomass fuels (almost double that of coal), the availability of adequate biomass fuel, and the transportation of biomass. These challenges can be mitigated by updating the fuel storage and fire protection system, conducting a biomass availability survey using modern surveying technologies, and by using low-cost transportation options such as railways where available.
Functionally, the conversion of relatively new coal-fired plants to biomass is a promising solution that can help to provide base load power plants with a reduced level of GHG emissions.
Switching to renewable power
This option is best suited for older coal-fired plants where most of the power island equipment has reached its end of economic feasible life and are slated to be retired.
The physical space required for producing the equivalent capacity (in GWs) from renewable plants—such as solar or wind— will be significantly larger than coal-fired power plants. Without added space, the power generation capacity from the converted facility will be reduced significantly. The demolition of power island equipment is also a challenging and costly process. These challenges are not purely technical; the commercial constraints to convert older coal-fired plants to renewable power plants include the capital required for demolition and the increase in unit cost of electricity.
The use of the land available at the power plant—along with the civil and power transmission system—is the real benefit to converting these facilities.
Adding small modular reactors
Newer coal-fired power plants are the most suitable candidates for such conversion. Small modular reactors (SMRs) are considered a clean and viable replacement for fossil fuels. The steam cycle of the coal-fired power plants and high temperature nuclear power plants are similar. The turbine island of coal-fired plants, therefore, can be re-used and powered with steam generated by SMRs.
The maturity of SMR technology is currently the biggest challenge to deployment. Currently, there are numerous well-funded technology developers and a few utilities and industrial companies supporting these efforts. The availability of nuclear fuel, experienced personnel, and nuclear waste management are all areas that conventional fossil fuel plant operators will find challenging. These challenges, however, can be mitigated with partnership, training, and co-operation with experienced organizations that have been operating nuclear facilities for decades.
The key benefits of this conversion are savings in grid infrastructure costs, capital costs, and a relatively small effort to develop and update the environmental impact assessments.
Firing with natural gas
Natural gas-fired plants generate up to 50% less GHG emissions compared to coal-fired plants. Several utilities have converted their coal plants to natural gas and many others are exploring this option. Conversion to natural gas also results in an improved plant net heat rate as it reduces the plant auxiliary power consumption by eliminating all coal handling and flue gas treatment equipment.
This conversion is expensive though, and dependent on the availability and supply of natural gas. Major modifications include the replacement of coal burners with natural gas burners, addition or expansion of existing natural gas pipelines and natural gas fuel trains, modification to the combustion air system, and the addition of flue gas recirculation. These factors make this option less attractive.
Given the ability to generate up to 50% less GHGs, coal to natural gas conversions have been implemented by operators who have committed to a low carbon future for power generation. Plant operators are considering this conversion to keep their plants running with natural gas and to significantly reduce their GHG emissions in support of their decarbonization goals. They are considering this conversion as an interim solution while renewable, battery storage, and SMR technologies become reliable enough to provide base load power.
Using coal for power generation may soon be a thing of the past. However, it is very likely these power plants will continue to operate until GHG free energy can provide reliable base load power. In the interim, repurposing these plants to use alternative fuels or repowering the plants with carbon neutral or emissions free energy sources will help reduce GHG emissions and still provide base load power generation.
Hatch has the experience and expertise to manage such repurposing of coal-fired plants to all the above-mentioned technologies. We collaborate between multiple sectors and business practices, including power, nuclear, infrastructure, climate change, renewable energy, risk management, digital, and advisory services to create unprecedented outcomes that are cost effective, safe, and sustainable.
We’re responding to the energy transformation by providing our clients with responsible energy solutions that will help us to achieve our low carbon future and shape a new energy landscape.
References:1. It’s critical to tackle coal emissions – Analysis - IEA
2. Coal in Canada - Wikipedia
3. List of coal-fired power stations in the United States - Wikipedia
4. Summary Tables - Global Energy Monitor
Kamran Akhtar, P.Eng.
Senior Engineer, Thermal Power
Kamran is a senior thermal engineer at Hatch, with over fifteen years of experience in power. He is a system design engineer, and project manager, and has experience as a technical expert for major power plant equipment manufacturers. Kamran has worked on several thermal and renewable power projects across the globe. As a thermal power professional, Kamran is always keen to help address the world’s energy needs with minimal impact to society and the environment.
Todd Thomas, P.E.
US Regional Manager, Thermal Power
Todd is a Regional Manager in the United States with Hatch. Todd has over 28 years in the power generation business with experience in all portions of the generation plant life cycle. He has managed the demolition program for one of the largest utilities in the United States and has first-hand experience regarding the impact of shutting down major coal-fired generation sources. The requirements, planning, and impacts of retiring a coal-fired generator ripple through the company, community, and industries that host and support the asset. Todd and the Hatch team are prepared to help our clients navigate this process from initial decision to the final acceptance of the project.