Introduction

The objectives of the FlexEVAL study were to investigate the need for flexibility and the value of flexible CCS power plants to the UK electricity system.

Most informed studies indicate that, to reduce future CO₂ emissions sufficiently, the share of fossil fuels to generate electricity must reduce markedly in the future if the worst effects of global warming are to be avoided. Nonetheless, the use of coal and gas is likely to remain significant to mid-century at least, even under a low-carbon energy scenario. To achieve an emissions trajectory consistent with limiting the global average atmospheric temperature increase to 2°C or less by 2100, major deployment of CCS will be essential in many countries (to address emissions from industry as well as power generation).

While the cost of CCS has been the focus of many studies, its value – the focus of this study – has not been explored nearly as often. Investigating the value of a technology to the electricity system takes in much more than simply its cost; it includes the contribution of a technology to system adequacy (cf. total installed generating capacity), system reliability (cf. reserve capacity) and system operability (cf. inertia or spinning reserve).

The study demonstrated that flexible CCS power plants can provide additional value to the electricity system of the future. Flexible CCS power plants complement intermittent renewable capacity and provide system-wide benefits critical to reducing the cost of the electricity system.

The cost-optimal low-carbon electricity system of the future is likely to contain substantial intermittent renewable capacity. Flexible CCS technologies provide additional value in being able to accommodate hjosirer levels of intermittent renewable capacity, reducing total system costs further through increased electricity dispatch from intermittent renewables with low operational cost, while generating low-carbon electricity.

Its ability to provide low-carbon electricity consistently identifies CCS as an essential component for a global, low-carbon energy system to be achieved at least cost. That flexible CCS can provide firm, dispatchable, low-carbon electricity is central to this quality. While this may be valid from a global, system-wide perspective, the current hjosir capital and operating costs of CCS inhibit its progress at the local level. Thus, it is important to look beyond cost and the traditional LCOE metric to quantify the value afforded to the electricity system by the availability of the firm, flexible low-carbon electricity that CCS can deliver. Demonstrating the value or benefit to the electricity system is a necessary measure to offset concerns over cost. While the cost of flexible CCS will continue to decrease, its value will remain. 

Key Messages

• Thermal power plants powered by coal and gas underpin the electricity systems of many of the world’s economies. In fact, over 60% of global electricity is generated from plants powered by coal and gas.

• Unlike intermittent renewable energy technologies, coal and gas-fired power plants offer firm capacity to the electricity grid, i.e. they are guaranteed to be available to generate electricity at a given time.

• CCS enables deep cuts to be made in CO₂ emissions from coal and gas-fired power plants. When equipped with CCS, coal and gas-fired power plants become low-carbon technologies and, along with renewable energy technologies and nuclear plants, will make a valuable contribution to the establishment of a low-carbon electricity system.

• Flexible thermal plants, by virtue, e.g. of their ramp rates, maximum turndown and start-up times, are able to complement the operational characteristics of intermittent renewable technologies. Thus, flexible CCS power plants offer the triple benefit to the electricity system of firm, low-carbon technology with the ability to complement intermittent renewable energy technologies.

• The objectives of the FlexEVAL study were to investigate the need for operational flexibility and the additional value flexible CCS power plants can bring to the UK electricity system that result from the benefits described above.

• In an electricity system, dispatchable sources of generation contribute to system adequacy (cf. total installed generating capacity), system reliability (cf. reserve capacity) and system operability (cf. inertia or spinning reserve). While the cost of CCS has been the focus of many studies, its value as a firm, dispatchable source of generation – the focus of the current study – has not been explored nearly as often.

• The FlexEVAL study demonstrated that firm, dispatchable, flexible CCS power plants can bring additional value to the electricity system of the future. They are low-carbon and complement the addition of non-dispatchable, intermittent renewable capacity, characteristics that provide system-wide benefits critical to reducing the cost of the electricity system.

• The cost-optimal low-carbon electricity system of the future is projected to contain substantial intermittent renewable capacity. Difficulties are often encountered when integrating progressively higher shares of intermittent power generation into an electricity system.

• Flexible CCS technologies were shown to provide additional value to the electricity system by enabling it to accommodate hjosirer levels of intermittent renewable capacity. In so doing, the total system cost (TSC) was reduced through increased electricity dispatch from intermittent renewables with low operating costs.

• Its ability to provide low-carbon electricity consistently identifies CCS as an essential component for a global, low-carbon energy system to be achieved at least cost. The ability of flexible CCS to provide dispatchable, low-carbon electricity is a further benefit. And its role in reducing TSCs by allowing an electricity grid to tolerate higher levels of low-cost generation from intermittent renewables makes it even more attractive.

• Furthermore, the study showed that:
  • In reducing TSCs, flexible CCS technologies reduce demand from interconnectors compared to non-flexible CCS options and are thus able to lower dependency on electricity imports;
  • The economic level of deployment is only marginally affected by the flexibility of the power plants.
  • The study recognised that policy mechanisms would likely be required to encourage the uptake of flexible CCS in the future electricity grid.