Coal combustion and electricity generation
Why focus on efficiency?
Much effort is currently being focused on reducing greenhouse gas emissions from coal-fired power generation. However, it is just as important to reduce the amount of carbon dioxide (CO2) that ends up in the waste flue gas that comes out of the flue stack of a power station. This is done by improving the efficiency of the coal combustion process. It stands to reason that the less coal used per unit of electricity generated, the less CO2 is produced.
One way to support the reduction of the amount of CO2 produced during this process is to improve the efficiency of the steam and gas turbines currently used in the generation process.
These turbines convert the heat released (from burning coal) into power or work, otherwise known as ‘thermal efficiency'. In fact, a one percent increase in thermal efficiency can result in a 2-3 percent decrease in CO2 emissions. This improves the performance of Carbon Capture and Storage (CCS) programs and reduces the associated economic costs.
Efficiency gains can also be made by developing innovative ways to generate electricity from coal or by reducing the amount of energy (and associated greenhouse gas emissions) required to power specific equipment at key steps in the electricity generation process.
Coal Innovation NSW have funded a number of projects to drive innovation to improve the efficiency and associated costs of coal-fuelled electricity generation and CCS initiatives.
The challenge:
Identifying and developing more efficient ways to generate electricity from coal with significantly less greenhouse gas emissions.
The action:
Coal Innovation NSW funded the University of Newcastle to research and develop a Direct Carbon Fuel Cell (DCFC).
Grant amount:
$608,719 (EOI Round 2009).
The project:
The University of Newcastle received funding in 2010 to research and develop a DCFC. In a DCFC, electricity is generated directly from coal through the chemical oxidation of coal which has been ground and purified of ash and other contaminants.
This technology is widely promoted as being able to generate electricity with much higher thermal efficiencies (~70-80%) than engines and turbines (~35-55%). The higher efficiencies result in substantial reductions in greenhouse gas emissions. Also, the emissions that are produced are almost pure CO2 so are ready for capture and storage.
This project has been completed and the final report, Development and Optimisation of the Direct Carbon Fuel Cell (PDF, 10.76 MB), contains further details of the project findings.
Direct Carbon Fuel Cell Demonstration Pilot Plant (photo courtesy of Prof Scott Donne, University of Newcastle)
The challenge:
Increase the efficiency of the chemical looping process in adoption of carbon capture technologies and develop its novel application as energy storage for coal fired power generation.
The action:
Coal Innovation NSW funded the University of Newcastle Priority Research Centre to undertake two projects to investigate a novel way to make coal fired electricity generation more efficient with the chemical looping process.
Grant amount:
$886,618 (EOI Round 2009) and $383,663 (EOI Round 2015).
The project:
The University of Newcastle Priority Research Centre for Energy received grant funding in 2010 to undertake research into a novel way of producing pure oxygen for use in the efficient burning of coal to generate electricity. The technology, termed Chemical Looping Air Separation (CLAS), relies on the principles of ‘chemical looping’ and uses the cyclic interaction of a metallic compound (called a metallic oxide carrier) with air as a means of separating out the oxygen.
CLAS offers the prospect of reducing the greenhouse gas emissions from the air separation processes. It also promises to be a cost-effective way to overcome a major barrier to the adoption of carbon capture technologies such as oxy-fuel combustion (i.e. electricity generation via steam produced by the combustion of coal in pure oxygen rather than air) as conventional air separation is notoriously expensive.
This project has been completed and the final report, A Novel Chemical Looping Based Air Separation Technology for Oxy‐Fuel Combustion of Coal (PDF, 29.53 MB), contains further details of the project findings.
Seven-metre high demonstration unit (photo courtesy of Behdad Moghtaderi, University of Newcastle)
The challenge:
Make post combustion capture of CO2 more commercially viable by reducing the energy requirement.
The action:
Coal Innovation NSW funded CSIRO Energy to prove a novel process to harvest energy from the CO2 capture process.
Grant amount:
$578,991 (EOI Round 2015)
The project:
CSIRO Energy is receiving grant funding to explore the harvesting of low-grade thermal energy by adding an electro-chemical energy conversion step to the conventional carbon capture process. The energy conversion is achieved by the electro-chemical reaction between CO2 and organic liquid absorbents such as ammonia and monoethanoalmine (MEA).
This CO2 capture and energy harvesting process could provide a technological breakthrough for post combustion carbon capture by significantly reducing the additional energy required to capture CO2, thereby making post combustion capture of CO2 more commercially viable.
This project has been completed and the final report, Energy harvesting from a CO2-capture process, contains further details of the project findings.
Energy Harvesting schematic (photo courtesy of Paul Feron, CSIRO Energy)
The challenge:
Assist coal-fired power stations to better manage their load demands and reduce greenhouse gas emissions with energy storage technologies.
The action:
Coal Innovation NSW funded the University of Newcastle to develop an energy storage technology termed ‘Redox Energy Storage’.
Grant amount:
Up to $383,663 (EOI 2015).
The project:
The University of Newcastle is receiving funding to develop an energy storage technology termed ‘Redox Energy Storage’ (RES) to help power stations better manage their power load by storing energy in off-peak periods for later dispatch.
The premise is that a RES unit can store large amounts of electricity during off-peak times when electricity demand is low, which can then be supplied back to the grid during peak times when demand is high.
The RES unit has potential to provide flexibility to coal-fired power plants to operate in the cycling mode without disrupting its baseload operation. This would reduce the need for more high cost capital generation equipment for serving times of peak electricity demand only, whilst reducing greenhouse gas emissions.
The project has been completed and the final report, Combining Thermochemical Energy Storage with Coal-Fired Power Generation, contains further details of the project findings.
Energy Storage Pilot Plant (photo courtesy of Behdad Moghtaderi, University of Newcastle)
The challenge:
Assist coal-fired power stations to better manage their load demands and reduce greenhouse gas emissions through the integration of large-scale battery storage technologies.
The action:
Coal Innovation NSW funded Sunset Power International Pty Ltd (trading as Delta Electricity) to undertake an assessment of the technical feasibility and financial viability of a Battery Energy Storage System (BESS) installation at Vales Point Power Station.
Grant amount:
$460,000 (EOI Round 2018).
The project:
This project assessed the technical feasibility and financial viability of a BESS installation at Vales Point Power Station. Applying BESS behind-the-meter provides network energy support without changing the generation capacity at the network connection point. This reduces load cycling and ramping of coal units and provides additional frequency support services to the electricity market. This is important to the stability of our electricity system a time of diminishing system strength and inertia due to increasing variable renewable generation.
The study showed a BESS could be integrated with an existing synchronous generator and would not compromise the co-located thermal unit or electricity network. However, the cost outweighs the anticipated revenues from this BESS/synchronous generator configuration. Without additional market mechanisms or incentives, it is unlikely that this technology will be developed in NSW.
The project has been completed and the final report, A techno-economic study of a battery energy storage system at Vales Point Power Station (PDF, 14.65 MB), contains further details of the project findings.
Vales Point Power Station, Lake Macquarie (Image courtesy of Delta Energy)
The challenge:
To better understand how the efficiency and environmental performance of coal-fired power stations could be improved by the integration of renewable geothermal energy resources.
The action:
Coal Innovation NSW funded the University of Newcastle to investigate how a novel technology termed Geothermal Assisted Power Generation could help reduce CO2 emissions and convert existing NSW coal plants into cleaner hybrid renewable energy plants.
Grant amount:
$99,165 (EOI Round 2018)
The project:
This project was a desktop mathematical modelling study designed to assess the feasibility of combining geothermal assisted power generation (GAPG) with NSW coal fired power stations. GAPG uses low grade geothermal heat to provide a heating boost to the steam cycle of the coal plant. This either increases electrical output without increasing coal consumption or maintains output by reducing coal consumption. In both cases, the emissions intensity of the coal fired power station reduces.
The results showed the GAPG system was feasible and more commercially viable than integrating a solar system into a coal plant. The maximum benefits that the GAPG technology could bring to NSW coal plants were a saving of up to 826 thousand tonnes/year of coal or the additional generation of 2,224 GWh/year of clean power. Bayswater Power Station was the most suitable NSW coal plants for application of the technology. After GAPG integration, the thermal efficiency of this coal plant could be increased by up to 6.5% and the emission intensity of the coal plant could be reduced by up to 6%.
The project has been completed and the final report, An In-depth Assessment of Geothermal Assisted Power Generation for NSW Coal-Fired Power Plants, (PDF, 3.8 MB) contains further details of the project findings.
The challenge:
To better understand how the economic and environmental performance of an existing coal-fired power station could be improved through the integration of large-scale renewable solar energy.
The action:
Coal Innovation NSW funded the University of Technology, Sydney to study the application of solar photovoltaic (PV), concentrated solar power and energy storage systems to a coal-fired power station to reduce coal consumption through solar-coal hybridisation.
Grant amount:
$96,390 (EOI Round 2018).
The project:
This project aimed to reduce coal consumption at a NSW coal-fired power plant by the integration of photovoltaic (PV), concentrated solar power (CSP), and energy storage systems. The underlying goal was to determine an optimal plant configuration at minimum cost. The configuration could not compromise the power plant’s generation capacity whilst maximising reductions in both power station emissions (by both CSP and PV) and spinning reserve cost (by PV). The final project outcome was the design of a solar-assisted coal plant integrated with 100MW of CSP and a 30MW PV farm. This was shown to reduce emissions by approximately 400,000 tonnes of CO2 per year.
The project has been completed and the final report, Optimal design of solar photovoltaic and concentrated solar power system for coal-fired power plants, contains further details of the project findings.
The challenge:
Investigate the potential to reduce the carbon dioxide emissions from coal-fired power generation by assessing the integration of alternate low-emissions technologies and fuels.
The action:
Coal Innovation NSW funded the University of Sydney to assess the technical and economic viability and emissions reduction potential of substituting a proportion of the coal combusted in NSW coal-fired power stations with dry organic waste with carbon capture and storage.
Grant amount:
$96,630 (EOI Round 2018).
The project:
This study investigated the technical and commercial viability of equipping coal fired power plants with co-firing capability for MSW (a source of biomass) and CCS. This technology (BECCS) is a negative emissions technology. The study investigated using dry combustible organic waste in power stations which is a small fraction of MSW.
The results revealed that as co-firing increased (more biomass was used), life cycle CO2 emissions decreased. Co-firing at a biomass-to-coal ratio of 10% reduced life cycle CO2 emissions by only 3%. When combined with CCS emissions fell by 81%. Net zero emissions power generation was achieved at 30% co-firing with CCS. This scenario is inhibited by the limited availability of biomass in NSW. The levelised cost of electricity (LCOE) also increased with the co-firing ratio, while the cost of CO2 avoided decreased. The study demonstrated that the use of BECCS can significantly reduce CO2 emissions in NSW, however further consideration of additional biomass sources is required.
The project has been completed and the final report contains further details of the project findings.
Possible MSW configuration showing diversion of MSW to power plants and carbon sequestration (Courtesy of the University of Sydney)
The challenge:
Develop new ways of generating electricity that combine renewable energy with combustion technologies to provide both cost-effective CO2 mitigation and firm electricity supply.
The action:
To develop a design pathway for integrating concentrated solar power (CSP), photovoltaics (PV) and ultra-supercritical (USC) coal power (USC) into a single power station setup for hybrid power generation.
Grant amount:
$946,500 (EOI Round 2018).
The project:
In this project Toshiba, with technical support by industry partners Abengoa and Ishikawajima-Harima Heavy Industries, developed a design pathway for ultra-supercritical (USC) hybrid solar/coal plants. This included detailed specifications for key equipment, detailed work on the integration of the renewable and combustion technologies, and the development of operational modes and control logic for the hybrid plant.
The research showed that it is technically feasible to develop and operate a solar/coal hybrid plant using commercially available technology. Techniques for increasing the plant’s efficiency and capturing CO2 emissions were also studied and incorporated into the overall plant designs.
The study (PDF, 7.03 MB) showed significant commercial and technical advantages of USC hybrid solar/coal plants over other forms of dispatchable power generation. An economic evaluation comparing the hybrid plant designs with that of a conventional coal-fired plant and a standalone CSP plant, showed that the hybrid designs have similar or better economic performance than a standard CSP plant. The technology is also highly dispatchable which is a necessary feature of modern electricity grids.
The concept of hybrid solar/coal plant – image courtesy of Toshiba International Corporation
The challenge:
To Identify and develop more efficient ways to generate electricity from coal with significantly less greenhouse gas emissions.
The action:
Coal Innovation NSW funded the University of Newcastle to research and develop a Direct Carbon Fuel Cell demonstration unit.
Grant amount:
$1,643,001 (EOI Round 2015)
The project:
The University of Newcastle received funding to build on its previous studies to develop and optimise a world first Direct Carbon Fuel Cell (DCFC) demonstration unit. The DCFC is not a new concept and the technology has undergone a major boost in international research interest in recent years, however technical barriers have prevented commercialisation.
This project aims to deliver a technology package capable of being licensed as a 1-kilowatt DCFC module based on laboratory findings and pilot plant optimisation. This project bridged a crucial gap between research and commercialisation of DCFC technology.
A large amount of laboratory data and results were generated that have improved the understanding of the functioning of the technology. This knowledge was employed in the successful demonstration of a 1kW scale DCFC, the largest operating system of its kind built to-date.
Figure 1 The 1 kW DCFC demonstration unit – Image courtesy of The University of Newcastle
The project has been completed and the final report, Development of a 1 kW Modular Direct Carbon Fuel Cell Demonstration Plant (PDF, 8.58 MB), contains further details of the project findings.