Carbon capture in power sector of China towards carbon neutrality and its comparison to renewable power

Highlights

• •CO2 capture has been proved to be technically feasible but far beyond technology mature.
• •Technical and economic analysis of operational CO2 capture demonstrations in power plant.
• •The reasons and bottlenecks of slow development of CCS are revealed.
• •Thermodynamic limit of energy penalty and cost reduction for CO2 capture is clarified.
• •Efficiency and cost competitiveness of CCS to renewable powers in China is analyzed.

Abstract

CO₂ capture from coal power plants is an important and necessary solution to realizing carbon neutrality in China, but CCS demonstration deployment in power sector is far behind expectations. Hence, the reduction potential of energy consumption and cost for CCS and its competitiveness to renewable powers are very important to make roadmaps and policies toward carbon neutrality. Unlike the popular recognition that capturing CO₂ from flue gases is technically and commercially mature, this paper notes that it has been proved to be technically feasible but far beyond technology maturity and high energy penalty leads to its immaturity and therefore causes high cost. Additionally, the potential energy penalty reduction of capture is investigated thermodynamically, and future CO₂ avoidance cost is predicted and compared to renewable power (solar PV and onshore wind power). Results show that energy penalty for CO₂ capture can be reduced by 48%-57%. When installation capacity reaches a similar scale to that of solar PV in China (250 GW), CO₂ capture cost in coal power plants can be reduced from the current 28-40 US$/ton to 10-20 US$/ton, and efficiency upgrade contributes to 67%-75% in cost reduction for high coal price conditions. In China, CO₂ capture in coal power plants can be cost competitive with solar PV and onshore wind power. But it is worth noting that the importance and share of CCS role in CO₂ emission reduction is decreasing since renewable power is already well deployed and there is still a lack of large-scale CO₂ capture demonstrations in China. Innovative capture technologies with low energy penalties need to be developed to promote CCS. Results in this work can provide informative references for making roadmaps and policies regarding CO₂ emission reductions that contribute towards carbon neutrality.

Graphical abstract

Cost reduction potential for CO₂ capture in power plants, and its cost competitiveness with renewable power.

1. CCS demonstration deployment is far behind its expectation

Recently, the Chinese government proposed the targets for peak carbon emissions in 2030 and carbon neutrality in 2060. Since coal power still contributes to over 60% power generation in China, carbon capture in power plants is necessary to achieve the above targets [1]. In 2019, the total carbon emission in China reached 9.57 billion tons, accounting for 28.6% of the world total emissions, in which 80% is from coal and 51% is from power and heat generation [2]. In 2021, the world total CO₂ emission reached 33.6 billion tons, around 5% rebound compared to 2020 [3]. The emissions from coal and coal power in China are beyond the world average levels of 44% and 41.7%, and far beyond the levels of 28.4% and 41.4% in USA [2]. Because of the huge energy consumption, the high carbon energy dominated structure, and the world highest installation of coal power, the application of carbon capture is the only way to mitigate CO₂ emissions of fossil fuels in China.

There are 19 large scale carbon capture and storage (CCS) facilities in operation worldwide, four of which are still under construction, capturing and storing around 40 million tons of CO₂ in 2020 [4]. As shown in Fig. 1, these projects are concentrated in the natural gas processing and hydrogen production industries, as CO₂ separation is a necessary step to obtain the final chemical products or fuels needed in these plants, thus as a byproduct, CO₂ can be affordably collected. Further, CO₂ concentration prior to separation in these processes is normally higher than that in the flue gases of power plants, and less energy is paid for CO₂ capture, making CO₂ capture economically feasible. Unfortunately, only two large CCS facilities are in power sector, Boundary Dam and Petro Nevo. Both projects make use of post-combustion CO₂ capture, the primary method of capturing carbon, while IGCC pre-combustion and oxy-combustion technologies are still in pilot trials.

Fig. 1.

Large scale CCS demonstration projects in operation and under construction[3].

The deployment of CO₂ capture, especially of that in power sector, is far behind its expected role in CO₂ emission reduction. In 2009, in the International Energy Agency's (IEA) technical roadmap, CCS contributed to 19% of the total greenhouse gas emissions. The IEA has planned to reduce emissions by 2050, with the aim of reducing global heating to 2 °C, meaning that the required number of CCS projects exceeds several thousand [5]. However, because lots of CCS projects cannot be deployed, its share in emission reduction is adjusted to 1/6 in 2013 [6], and further lowered to 9% by IEA in 2019 [7]. However, with the development of new opportunities for CCUS applications for BECCS (Bioenergy with carbon capture and storage), DAC (Direct air capture), and hydrogen production, in the latest report [8,9], IEA claimed that CCUS accounts for nearly 15% of the cumulative reduction in emissions in the Sustainable Development Scenario. The current number of operational and constructing CCS projects is 23 and is far lower than the expectations of roadmaps (Fig. 2). It is indisputable that the development of CCS is slow and its real contributions to emission reduction is fading.

Fig. 2.

Gaps between CCS project deployment and IEA's roadmaps.

It was well recognized that capturing CO₂ from flue gases is a technically and commercially advanced technology, but CCS facilities are far behind their expected output. Thus, the question remains, how effective is CO₂ capture technology when implemented within a power plant facility and what explanations are available that could explain the slow development of CCS? There are many researchers analyzing CCS from a strategical point of view [10], [11], from the aspect of techno-economic performance of certain designs [12], [13], and in terms of finance and policy [14], [15]. However, deep technical, and economic analyses of operational CO₂ capture facilities located within power plant are lacking. In addition, the thermodynamic limit of energy consumption and the cost reduction potential for CO₂ capture also need to be clarified, which are vital for the future of CCS development. Furthermore, the competitiveness between CCS and the renewable energy sector in China also needs to be compared to make emission reduction policy changes aimed toward carbon neutrality. The present study analyzes the technical and cost differences between the first CO₂ capture demonstration projects in China and Canada, the energy and cost reduction potential of the facilities, and the competitiveness between CCS and renewable powers in China. These comparisons will provide an informative framework for establishing and amending policies regarding CO₂ emission reductions with the aim of achieving carbon neutrality.

2. Current status and the problems of coal power CCS demonstrations

There are currently only two large scale CCS demonstration projects in power industry that have been successfully operated: Boundary Dam and Petra Nova projects. The Boundary Dam post combustion CO₂ capture (PCC) demonstration project is located in Regina, Canada, whose purpose is to demonstrate the PCC technology adopting organic amine as the absorbent solution. The project is retrofitted based on the Boundary Dam Unit 3 and equipped with CO₂ capture facilities. The original Unit 3 served in the 1970s, adopting Saskatchewan lignite as the raw material (comprising low sulfur content of 0.3%-0.9%, high moisture and a volatile content of 37.5%-41%), and a subcritical unit with the steam parameter of 12.5 Mpa/538 °C/538 °C was employed. The plant net efficiency is currently about 35% with a net electricity output of 139 MW. The annual CO₂ emission is about 1.1 million tons/year. In May 2011, SaskPower upgraded the original power plant and equipped it with CO₂ capture facilities. The retrofitted power plant adopts the Hitachi 160 MW steam turbine with the steam parameters of 12.5 MPa/565 °C/565 °C, and the net power output of the system is about 141 MW. After the addition of the CO₂ capture facilities, the net power output of the system was reduced to 95 MW, and the power generation efficiency was roughly 23.9%. The steam parameters of the retrofitted unit were optimized to 29 MPa/593 °C/621 °C. With the addition of the CO₂ capture facilities, the optimized net electricity output of the system can be increased to about 110 MW, and the optimized power generation efficiency is roughly 27.7%. The demonstration project is designed to capture 91% of all CO₂ emitted from the flue gas, which is about 1 million tons/year. The captured CO₂ is transported to the Weyburn oil field for enhancing oil recovery, which is about 100 km away. The total investment of the project was about 1.24 billion U.S. dollars, of which 50% was invested in CO₂ capture facilities, 30% in the refurbishment of original power stations, and about 20% in emission control facilities [16]. During the month of February 2022, the facility at Boundary Dam Power Station captured 41,584 tonnes of carbon dioxide. The average daily capture was 2,796 tonnes per day with a peak one-day capture of 2,950 tonnes when CCS was online [17].

The W.A. Parish post combustion CCS demonstration project is one of the third-round projects funded by the US Department of Energy Clean Coal Power Initiative, which aims to demonstrate the use of advanced amine-based solutions to capture CO₂ from the exhaust gas of power plants. NRG Energy is responsible for submitting the proposal and installing the CO₂ capture facility on the 650 MW Unit 8 of Parish Power Plant. The total amount of power generation sourced from the existing W.A. Parish power plant is roughly 3,865 MW, the gross power generation amount of unit 8 is 650 MW, and the net power output is roughly 616 MW. The capacity factor is roughly 80%, and the net power generation efficiency ranges between 30% and 33%. The unit 8 uses Powder River Basin Wyoming sub-bituminous coal with an average low heating value (LHV) of 19.77 MJ/kg. In this project, advanced amine-based absorbents were employed to recover CO₂ from part of the flue gas. Nearly 250 MW of flue gas is bypassed from the 650 MW flue gas of Unit 8 for decarbonization. The CO₂ capture ratio is set to 90%, and the amount of captured CO₂ is roughly 1.6 million tons/year (5,475 tons/day). To build a post-combustion CO₂ capture system in the existing Unit 8 (coal-fired unit) of WA Parish Plant, the company built a new 80 MW natural gas single-cycle gas turbine unit to produce electricity and steam for the CO₂ capture unit. The gas turbine is equipped with a waste heat boiler to produce steam and the steam produced is supplied for absorbent regeneration. The absorbent in the CO₂ capture unit adopts MEA, mixed with other amine components of comparable properties. The gas turbine uses GE's 7EA gas turbine with a net electrical output of 80 MW, of which, 50 MW is used for the CO₂ capture unit to operate at full load, and the remaining 30 MW can be integrated into the power grid for sale. The power generation efficiency of the natural gas single cycle is roughly 32.7%, and the combined cycle power generation efficiency is about 51%. The captured CO₂ is compressed to 14.6 MPa and transported to the West Ranch oil field in Jackson County, Texas, through an 80-mile-long pipeline with a diameter of 12 inches for EOR [18]. Except boundary dam and W.A.Parish projects, Kemper County project began construction in 2010 [19]. This IGCC pre-combustion CO₂ capture used TRIG™ gasification technology, and can capture around 3 Mt of CO₂ captured annually [19]. The Kemper County project was developed by Mississippi Power, and it received a $270 million grant from the Department of Energy [19]. The project was initially estimated to cost $2.2 billion, but was projected to cost almost $6.66 billion in 2016 [19]. In July 2016, Southern Company announced that Kemper County had started to produce synthetic gas from coal [19]. Unfortunately, in 2017 Mississippi Power announced the cancelation of Kemper County due to both the raise of cost and the technical problems of coal gasifiers.

The technical and economic evaluation of the Petra Nova project is complicated because the gas generators are employed to integrate with the CO₂ capture unit. This article takes the first large scale demonstration of the coal power CCS-Boundary Dam project as an example to illustrate the techno-economic performance of coal power CCS. The techno-economic performances of the project are summarized in Table 1. It can be seen that the power generation efficiency of the project without CO₂ capture can be increased to about 37.8% through boiler modification and the upgradation of steam turbines. The capture and compression of 91% CO₂ of the flue gas will decrease the system efficiency to 23.9%-27.7%. The unit investment is around 7654 US$/kW-gross, which is far beyond the predictions of the established literature. Compared with the power plant prior to the retrofit, the unit CO₂ capture cost of the project was around 182 US$/t-CO₂, most of which is caused by the expensive investment. The major expenses from the latter investment comprised primarily of the boiler modification, steam turbine upgradation, and the desulfurization system retrofit. However, the CO₂ capture facility only accounted for about 50% of the total investment, and the fuel cost accounted for a small proportion of the expenses. In fact, boiler modification and steam turbine upgradation do not belong to CO₂ capture facilities and this kind of retrofit is beyond the necessary modifications required by CO₂ capture. If the retrofit investment is treated as the cost of a reference power plant, the CO₂ capture cost of the Boundary Dam Project can be reduced to 142 US$/t-CO₂ compared to the refurbished power plant. Additionally, according to the power plant's estimation, the retrofit investment of a second PCC can be reduced by 92% through optimization, and the capture infrastructure investment can be reduced by two thirds [20]. Based on the investment reduction, the CO₂ capture cost of the second set of PCC can decline to around 50 US$/t-CO₂. Thus, it can be seen that unnecessary upgrades to the power plant (i.e., those not contributing to CO₂ capture) cause high CO₂ capture costs in the Boundary Dam power station. Although many lessons in operations regarding CO₂ capture in power plants have been gained from the first large scale demonstration Boundary Dam, insufficient investment of non-CCS facilities (such as retrofit cost) is involved into CO₂ capture, leading to the impression that the cost of CO₂ capture from a coal power plant is extremely high.

Table 1.

Techno-economic analysis of the Boundary Dam demonstration project.

Techno-economic parameter of the retrofitted Boundary Dam PCC
Fuel	Saskatchewan lignite
Energy input, MW	397.1
CO2 capture rate (CO2 capture ratio)	100 million ton/year (about 91%)
CO2 capture technology	Cansolv amine-based carbon capture process
Retrofitted steam parameter (no optimization)	12.5 MPa/565 °C/565 °C
Retrofitted power output (no optimization), MW	95
Retrofitted system efficiency (no optimization), MW	23.9
Retrofitted steam parameter (optimized)	29 MPa/593 °C/621 °C
Retrofitted power output (optimized), MW	110
Original plant consumption, MW	11
Optimized CO2 compression power, MW	9
Optimized CO2, SO2 capture (energy consumption for amine regeneration), MW	14
Retrofitted system efficiency (optimized), %	27.7
CO2 utilization	Weyburn EOR
Total investment	1.24 billion
Unit investment, US$/kW- gross	7,654
Unit investment, US$/kW- net	11,273
Annual investment, M$	156.21
Annual O &M cost, M$	49.62
Annual fuel cost, M$	44.13
COE, US$/kWh	0.305
CO2 capture cost, US$/t
Techno-economic parameter of the retrofitted Boundary Dam power station
Fuel	Saskatchewan lignite
Energy input, MW	397.1
Steam turbine	Hitachi 160 MW
Steam parameter (no optimization)	12.5 MPa/565 °C/565 °C
Optimized steam parameter	29 Mpa/593 °C/621 °C
Retrofitted power output (no optimization), MW	141
Retrofitted system efficiency (no optimization), %	35.5
Retrofitted gross power output (optimized), MW	162
Retrofitted net power output (optimized), MW	150
Retrofitted system efficiency (optimized), %	37.8
CO2 emission, Mt/y	110
Original system
Fuel	Saskatchewan lignite
Energy input, MW	397.1
Steam parameter	12.5 Mpa/538 °C/538 °C
Gross power output, MW	150
Net power output, MW	139
Efficiency, %	35.5
CO2 emission, Mt/y	110
COE, $/kWh4	0.082

¹Annual investment coefficient CRF = 0.12.

²Operation & Maintain factor = 0.04.

³Average LHV: 8000 btu/kg; coal price: 35 $/ton.

⁴Due to the inability to obtain the power generation cost of the SASK POWER, this article uses the retail electricity price in Regina as the reference coal-fired power plant supply cost.

There is no large-scale CCS demonstration project in China's power sector. The Huaneng Shidongkou project is the only small-scale pilot project with a CO₂ capture capacity of more than 100,000 tons/year. The annual CO₂ capture capacity of the Huaneng Shidongkou CO₂ capture demonstration is 120,000 tons, and the total investment is about 150 million RMB. The second power plant in the Huaneng Shidongkou is a supercritical unit with a total installed capacity of 252 MW, including two 600 MW supercritical units and two 660 MW supercritical units. The average standard coal consumption for the plant is 280-305 g/kWh, and the power generation efficiency is 40.3%-43.9%. The CO₂ capture facilities are located in a 660 MW supercritical unit, using amine absorption technology. The flue gas processing capacity is 66,000 Nm³/h (about 4% of the total flue gas volume), the designed annual operating time is 8000 hours, and the CO₂ recovery ratio is as high as 85%. The technical indicators, such as the energy consumption of CO₂ capture, include steam consumption of 3.0 GJ/t-CO₂ (1.84 tons/t-CO₂), the power consumption of 75 kWh/t-CO₂, and solvent consumption of 6 kg/t-CO₂ [21]. The captured CO₂ has a purity greater than 99.9% and is stored in storage tanks after cooling by liquid ammonia, and finally sold to food companies. Table 2 summarizes the performances of the whole plant. The whole plant efficiency is about 40.3%-43.9% without CO₂ capture and declines to 25.2%-27.5% with a total of 90% CO₂ captured. The unit investment of the original power plant is about 600 US$/gross-kW and will rise to 1,100 US$/gross-kW with 90% CO₂ captured. The designed CO₂ capture cost is around 38.3 US$/ton, and the expected CO₂ avoidance cost is approximately 66.7 US$/ton.

Table 2.

Techno-economic performances summary of PCC in China.

	PC	PC with 90% CO2 capture, estimation based on Shidongkou project
Energy input, MW	1,506	1,506
CO2 capture amount (CO2 capture ratio)	-	3.4 Mt/year
CO2 capture technology	-	amine
Boiler	Supercritical	Supercritical
CO2 pressure, MPa	-	10
Gross power output, MW	660
Net power output, MW	634
System efficiency, %	42.1%1[22]
Energy consumption of CO2 regeneration (power equivalence), MW	-	228.7
Power consumption in the CO2 capture unit, MW	-	8.4
Net power output of PC+CC, MW	-	396.9
System efficiency of PC+CC, %	-	26
efficiency penalty of CO2 capture	-
Power plant investment, M$	3962	726
Unit investment, $/gross-kW	600	1,050
CO2 capture cost, $/ton	-	38.9

¹The supercritical power plant is estimated at 600 $/gross kW investment.

²Estimated by the scale factor method, the scale factor of the capture unit is set to 0.7.

Comparing the Boundary Dam project to China's large scale coal power plant with CO₂ capture (scaling based on Shidongkou project), the energy consumption for CO₂ capture of the two projects is similar. However, the investment made for Boundary Dam is significantly larger, and it contains about 50% of the power plant retrofit cost, which results a 4.3 magnitude difference in CO₂ capture cost. Additionally, the fuel cost of the two demonstration projects is also significantly different. The price of coal in Shidongkou project is over two times that in the Boundary Dam. Thus, fuel cost accounts for only a small proportion of CO₂ capture cost for the Boundary Dam project while over 40% for the Shidongkou project.

From the techno-economic analysis of the above demonstration projects, it can be seen that although CO₂ capture demonstration is successfully operated among the power plants, extremely high costs limit further deployments. Unlike the general view that the technology for capturing CO₂ from flue gas is well-established, the present study deems this technology to be only technically feasible. High energy consumption is an important reason that leads to technological immaturity. Initially, when the first-generation solvent-MEA was assessed and its regeneration heat was over 4.0 GJ/t-CO₂, CO₂ capture from power plants was thought to be technically mature as gas separation had been applied in chemical industry for years. Then, second-generation solvents including advanced amine-based solvents were developed to further reduce the regeneration heat to around 3.0 GJ/t-CO₂. Further, recent solvent developments can potentially reduce energy consumption to around 2.3-2.4 GJ/t-CO₂. Even so, CO₂ capture from power plants is still difficult to spread due to its high energy consumption and cost. The low CO₂ concentration and large amount of flue gas treated after combustion have led to the high energy consumption for CO₂ capture, making it difficult to deploy demonstrations widely even if the first large scale project has been run successfully. The reduction of energy consumption will play a key role in cost reduction and will push the maturation of the technology. Based on the Shanghai Shidongkou demonstration project, the Huaneng Group has recently developed a new type of absorbent and conducted a 1000 ton/year CO₂ capture demonstration test. The absorbent adopts a liquid-liquid two-phase absorbent. This solvent can form two layers after absorbing CO₂, of which one layer primarily comprises water and the other primarily comprises CO₂ rich solvent. By sending only a CO₂ rich solution to the regeneration tower and by recycling the water layer for sue in the absorber, the heat duty of the reboiler in the regeneration column can be significantly reduced. While the assessed energy consumption of CO₂ regeneration declines from 3.0 GJ/t-CO₂ to 2.3 GJ/t-CO₂. Through improvements in non-aqueous solutions, liquid-liquid absorbent, and a higher level of heat integration, the power plant efficiency is only reduced by 5.25-6.25 percentage points when 90% CO₂ is captured (see section below). If the reduction of energy consumption is considered and the reduction in equipment investment and maintenance costs are not, the CO₂ capture cost of the demonstration project in China will decrease to 23.5%-24.8 US$/t-CO₂ (a decrease of around 35%-39% assuming that the coal price is 75 US$/t), and the cost of the CO₂ avoidance cost will be reduced to approximately 27.0-29.6 US$/t-CO₂ (a decrease of approximately 56%-61%). Therefore, high energy consumption is the main reason for the technical immaturity of CO₂ capture from power plants.

3. Potential of energy consumption and cost reduction for CO₂ capture

3.1. Energy consumption reduction potential

Current CO₂ capture technology in coal-fired power plants cannot be applied broadly due to its high energy consumption and cost. Thus, it is vital to know the reduction potential both in energy consumption reduction and cost of CCS in coal-fired power plants. The decrease of energy consumption for post combustion technology mainly depends on the heat and temperature requirements of the absorbent regeneration. The heat consumption for absorbent regeneration is comprised of three components, including the heat of CO₂ desorption, the sensible heat required to heat the solvent, and the heat needed for water vaporization. For the first-generation absorbent of 30 wt.% MEA aqueous solution, the heat consumption is more than 4.0 GJ/t-CO₂, in which the heat of water vaporization and CO₂ desorption account for 30% and 50%, respectively. To further reduce the energy consumption of CO₂ regeneration, new solvents have been developed from two approaches. The first is the development of non-aqueous, two-phase, liquid-liquid absorbents, focusing on reducing the amount of water entering the regeneration tower, thereby reducing the heat of evaporation. The second is to develop new compositions of the absorbent to reduce the heat of CO₂ desorption, such as new organic amines and ionic liquid absorbents The regeneration temperature of the Shell CANSOLV absorbent used in the Boundary Dam power station is around 120 °C, and the heat consumption of CO₂ regeneration is 2.33 GJ/t-CO₂. The Huaneng Group in China is currently testing a novel liquid-liquid absorbent based on a 1000 t/day CO₂ capture pilot with a heat consumption is approximately 2.3 GJ/t-CO₂. With technological improvements, such as the latter, the regeneration temperature of absorbents is expected to be further reduced to 90-110 °C, while the regeneration heat consumption will decline to 1.7-2.0 GJ/t-CO₂, as shown in Fig. 3.

Fig. 3.

The developments of regeneration temperature and heat requirement of the solvents[23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46], [47], [48], [49], [50].

The theoretical relationship between the efficiency penalty of CO₂ capture, the temperature, and the heat consumption of CO₂ regeneration are shown in Fig. 4. According to current levels, the typical regeneration temperature of rich solvent is between 120 °C and 130 °C, and the heat consumption of CO₂ regeneration is around 3.0-3.5 GJ/t-CO₂. The theoretical efficiency penalty ranges from 8 to 10 percentage points (including compressing CO₂ to 100 bar) when 90% CO₂ is captured. Considering actual heat loss and the level of system integration, the efficiency penalty of 90% CO₂ capture is around 10 to 15 percentage points. If the regeneration temperature is reduced to 90-110 °C and the regeneration heat is reduced to 2.0 GJ/t, the theoretical efficiency penalty can decrease to 4.2-5.0 percentage points (thermodynamics limit is 3.5 percentage points). The energy consumption of CO₂ capture is also related to energy integration levels between the power station and the CO₂ separation unit. Considering the irreversible loss of the actual processes and the system integration, the efficiency penalty can be reduced to 5.25-6.25 percentage points, as shown in Fig. 4.

Fig. 4.

Potential of energy consumption for post combustion CO₂capture (90% CO₂is captured and the efficiency of the supercritical PC plant is assumed to be averagely 42% in China).

3.2. Cost reduction potential

An energy consumption reduction will further reduce the cost of CO₂ capture. Additionally, investments in CCS facilities will also be reduced after large scale demonstrations. Therefore, CO₂ capture cost will continue to decline as the technology matures. Fig. 6 shows the forecast of the reduction in CO₂ capture cost of the coal-fired power plants whereby the current CO₂ capture cost of the Boundary Dam project is roughly 142 US$/t-CO₂ (excluding the investment of non-CCS facilities). Saskatchewan power claims that the second set of demonstration investments can be reduced by 67%. Based on this, our calculated CO₂ capture cost is 45 US$/t-CO₂. Assuming cost learning starts from the third set of demonstration, CO₂ capture cost in North America will drop to around 16-30 US$/t-CO₂ when total installed capacity reaches 250 GW (shown in Fig. 5). In contrast, based on the experiences of Huaneng power plant's small scale demonstration projects, CO₂ capture cost of supercritical units has been roughly 28 US$/t-CO₂ in areas with lower coal prices, such as inner Mongolia, Xinjiang, Shanxi, Shaanxi, and Ningxia. While in eastern regions where the coal prices are high, such as Shanghai and Zhejiang, the cost of CO₂ capture is as high as 35-40 US$/ton, as shown in Fig. 6.

Fig. 6.

CO₂capture cost in different provinces of China and its cost reduction potential.

Fig. 5.

Redcution potential of CO₂capture cost in Canada and China (assuming coal price is 35 $/ton).

With plant efficiency improvements and a wide deployment of power stations with CO₂ capture, CO₂ capture cost in China is expected to be further reduced to 10-20 US$/t-CO₂. In Northwest China, such as Inner Mongolia, Xinjiang, Shanxi, Shaanxi, and Ningxia, where coal prices are relatively low, the CO₂ capture cost will drop to 10-16 US$/t-CO₂. While in the eastern regions, the CO₂ capture cost will be closer to 18-20 US$/t-CO₂, as shown in Fig. 6. The energy consumption reduction of CO₂ capture will play a key role in reducing CO₂ capture cost, especially under the condition of high coal prices and low investment learning. Currently, the power generation efficiency will reduce by 12 percentage points with a CO₂ capture rate of 90%, but the efficiency penalty is expected to decline to 5.25-6.25 percentage points in the future. When coal prices fluctuate between 35 and 95 US$/t in China, the decrease of CO₂ capture energy consumption will contribute between 67%-75% (low investment learning rate) and 30%-45% (high investment learning rate) to the total capture cost reduction. Therefore, future CO₂ capture cost reduction of the coal-fired power plant will primarily depend on the drop of CO₂ capture energy consumption, as shown in Fig. 7.

Fig. 7.

Role of energy consumption drop in CO₂capture cost.

3.3. CCS versus solar PV and wind power

If the installed capacity of PCC could reach the current scale of solar PV or onshore wind power in China, the cost of electricity and CO₂ avoidance in the northwestern region would be comparable to or lower than the best levels attained by these industries, as shown in Fig. 8. When the installed capacity of coal power CCS is 250 GW, its COE can be reduced to 0.038-0.044 US$/kWh, which is competitive with onshore wind power or solar PV in China. As for power generation efficiency, the current net efficiency of PC with 90% CO₂ capture is around 26-28%. It is expected to reach 32%-34% in the future, which may be higher than that of solar photovoltaic power. However, it should be noted that although the cost of PCC can be reduced to the current best level of the onshore wind power and solar PV, CCS seems to have missed the prime development period. The truth is that the current COE of the best photovoltaic and onshore wind power has been reduced to be almost the same as that of coal power without CO₂ capture through policy incentives. As the emission reduction timeline approaches and there is still no large-scale coal power CCS demonstration in China, the time window for coal power CCS's playing a major role in CO₂ emission reduction is being shut down. The first large scale development of China's domestic wind power and photovoltaic energy production started in 2010, when coal power CCS also started small scale demonstrations (such as the Huaneng CCS). After two to three years, the onshore wind energy and photovoltaic technology have experienced a rapid decline in costs, while coal power CCS stagnated at its early stage of demonstration. It can be seen from Fig. 8 that at the beginning of the development of photovoltaics, its COE far exceeded that of coal-fired power generation with CO₂ capture. The rapid decline of solar PV COE was due to the implementation of subsidy policies and the continuous growth of technology itself, which led to a significant reduction in module prices. In addition, although photovoltaic power has gone through a stage of "abandonment", there is always a huge demand for power products. There is currently no huge market demand for captured CO₂. In the future CO₂ used for EOR or fuel production will create huge market, but these technologies need low cost and stable CO₂ sources. Simultaneously, the CO₂ pricing mechanism is in an initial stage in China and is imperfect, resulting in a lack of an inherent driving force to implement coal power CCS. Therefore, if the coal power CCS in China is promoted, its power generation efficiency will be higher than that of the solar photovoltaic and onshore wind power. Further, the induced COE and CO₂ avoidance cost following a large-scale promotion could be comparable to the current best level of renewable power sources, such as solar and wind power. However, if further increases in the installed capacity of the wind power and solar PV are considered, their costs will continue to decrease but will be limited by the infancy of the development of CCS. Therefore, it is possible that innovative technologies with lower energy consumption will be needed to make the coal power CCS in China more competitive.

Fig. 8.

Comparison of COE and CO₂avoidance cost between coal power CO₂capture and renewable powers in China.

4. Conclusion and suggestions

In this article, the development of CCS demonstration projects is summarized, and the energy consumption and cost of coal power CCS demonstration are investigated. Additionally, the reasons for the slow development of coal power CCS demonstration are explored. This work also predicted the energy consumption, and cost reduction potential of coal power CCS technology, and further investigated its competitiveness with renewable power generations. We concluded that: (1) In contrast to the common view that the CO₂ separation from the power plant flue gas is a mature and commercial technology, this study believes that this technology is immature. Excessive CO₂ capture energy consumption leads to technological immaturity. Reducing CO₂ capture energy consumption is crucial to promote the commercialization of coal power CCS. (2) As the world's first large scale power plant demonstration project, the Boundary Dam Project has shown the experience of CO₂ capture based on a coal-fired power plant. However, many investments of non-CCS facilities have been included in this project, leading to capture costs as high as 182 US$/t-CO₂. The CO₂ capture cost will be reduced to around 142 US$/t-CO₂ excluding the cost of non-CCS facilities. Based on the experience of the Shanghai Shidongkou pilot project, the investment and cost of CO₂ capture for full size coal power plants are much lower, and the CO₂ capture cost is around 38 US$/t-CO₂. Comparing the CO₂ capture demonstration between the Boundary Dam Project and China's coal-fired power plant, the energy consumption performances of both are similar, but the excessive investment undertaken for the Boundary Dam Project and the high coal price in eastern China cause the 4.3 times difference in the CO₂ capture cost. (3) With the decrease of heat consumption and temperature of CO₂ regeneration, the efficiency penalty of the coal power plant with 90% CO₂ capture will decline from the current over 10 percentage points to 5.25-6.25 percentage points. When the installed capacity reaches 250 GW, the CO₂ capture cost of coal power can be reduced to 19-33 US$/t-CO₂ in North America and 10-20 US$/t-CO₂ in China, respectively. When the coal price is high and the investment learning rate is low, the energy consumption reduction of CO₂ capture is crucial to the reduction of the CO₂ capture cost. (4) When the installed capacity of coal power CO₂ capture reaches the scale of onshore wind power or solar photovoltaic power, the cost of electricity and CO₂ avoidance in Northwestern China is comparable to that of the current best level of solar photovoltaic and onshore wind power and even be lower. Furthermore, the net efficiency of PCC can be higher than that of solar photovoltaic power, and thus PCC can be competitive with renewable powers in China.

Coal power CCS is necessary and important for the transition from a high carbon energy structure to carbon neutrality in China. To promote the development of coal power CCS, this article suggests that: (1) The energy structure of China is dominated by coal; the implementation of coal power CCS is a necessary way to reduce carbon emissions. Early demonstrations are suitable in the northwest of China to reduce costs and to promote the rapid development of coal power CCS. On one hand, subsidies or carbon prices should be set to allow coal power CCS to be promoted by external benefits. On the other hand, motivation through policy implications only can be insufficient, seeking and stimulating the internal demand of CO₂ is thus a more worthy of consideration. For example, combined with hydrogen energy maybe a feasible way. The development of hydrogen utilization will promote the need for carbon capture.

(2) The deployment of large-scale post-combustion CO₂ capture technology of coal power plant CCS in China seems to have missed the prime ten-year development period. Even so, if it could be deployed immediately, the CO₂ capture cost could be reduced to the current best level seen in onshore wind power and solar photovoltaic power within ten years of development. However, when considering the timeline, the competitiveness of the development of current carbon capture technology is no longer as sufficient as renewable onshore wind power and solar photovoltaic. Thus, the demonstration of novel technologies with a greater potential of reducing energy consumption and cost such as chemical looping combustion can be more competitive in the future than renewable energy power generation technologies. (3) A complete market mechanism should be established to make CO₂ products more valuable. Otherwise, coal power CCS will still lack the required motivation from the internal market. By breaking the monopoly between the power, oil and gas, and chemical industries at the national level, demonstrating full chain demonstrations, and combining CO₂ with enhanced oil recovery and the other industries, CCS development can be promoted.

Declaration of competing interest

The authors declare that they have no conflicts of interest in this work.

Biography

Sheng Li is a professor of Beijing Institute of Technology. His research interests include CO₂ capture, coal gasification, hydrogen production from fossil fuel, thermodynamic analysis and polygeneration energy system integrations. He was awarded by “Outstanding member of Youth Innovation Promotion Association, Chinese Academy of Sciences” and “National Science Foundation for Outstanding Youth”. As first author, he has published papers in Nature Climate Change, Environmental Science and Technology, The Innovation, etc. He also got several academic awards including ASME Young Engineer Travel award, A hundred Excellent Doctoral Dissertations in Chinese Academy of Sciences, etc. He was also invited as keynote speaker at international academic conferences and the associate editor of SCI journals.