Direct air capture using nuclear power plants

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A "Feasibility study for coupling of Nuclear Power Generation with Green House Gas capture" (pdf) by Dmitry Grishchenko and Pavel Kudinov examines the potential for using some of the waste heat from nuclear power stations to drive low temperature absorption and capture of CO
2
from the atmosphere.

Abstract – Humankind must urgently find solutions to two major and tightly coupled problems: (i) transition to CO2-free energy and (ii) control of climate by changing concentration of greenhouse gasses in the atmosphere. Both problems are targeted in the UN sustainable development goals and must be achieved by 2030. Four scenarios aiming to limit global temperature rise to 1.5ºC were summarized by the 2015 Intergovernmental Panel on Climate Change. All scenarios rely on two- to six-fold increase in nuclear energy production by 2050 and require mass deployment of negative emission technologies, i.e. CO2 capture and storage (CCS). Mass deployment of the CCS technologies require a source of a CO2-free electric power and heat. Nuclear energy can provide both.

The goal of this study is to demonstrate the feasibility of the climate control and CO2-free energy production using nuclear power coupled with CCS technology. In this work we provide (i) a review of different methods for CCS, (ii) possible approaches to optimization of energy extraction from existing and expressly designed NPP thermal cycles to achieve high efficiency of the coupled NPPCCS facilities and (iii) assess the needs and potential for NPP CCS deployment to achieve and maintain pre-industrial level of greenhouse gas concentration in atmosphere needed to effectively counteract climate crisis.

The paper discusses

  • technologies for Direct Air Capture, identifying techniques requiring low temperature heat,
  • the temperature characteristics of light water reactors and potential for extracting low temperature heat (which are already employed in some co-generation schemes such as district heating)
  • the possible outcomes of coupling DAC with Nuclear Power Plants in terms of quantities of clean energy produced and CO
    2
    captured.

Presumably waste heat from other thermal power plants, such as coal, oil, gas, biomass, solar thermal (e.g. concentrating solar), and geothermal energy, could be used in the same manner, as well as possibly solar thermal energy and low temperature geothermal. Combining DAC with a CO
2
-emitting fossil fuel or biomass plant fitted with Carbon Capture and Storage might be attractive in sharing a common CO
2
transport and sequestration stream. The economics of implementing such schemes would depend on, or be much enhanced by a carbon pricing scheme which rewarded negative emissions.

Implementation

Sizewell C

EDF, who are planning to build a twin-EPR nuclear power station at Sizewell C (SZC), are involved in a project to build a Direct Air Capture plant at the SZC site.

In November 2020 EDF published an Expression of Interest document to participate in a competition run by the UK's BEIS Department for a DAC demonstrator project at SZC.

An article EDF invites interest in DAC project at Sizewell C published by World Nuclear News on 25 November 2020 describes the principle of operation:

By diverting a very small amount of the plant’s thermal output for DAC, the project would have the potential to become carbon negative ...

...the DAC would utilise steam of about 280 degrees C or lower tapped off from the turbine installation at the SZC power station when operational; it would remove CO2 from the ambient air where the concentration is around 400ppm by placing large volumes of air in contact with chemicals known as sorbents; the two methods being considered are: (i) absorption: CO2 dissolves into liquid sorbent; and (ii) adsorption: CO2 adheres to the solid surface of the sorbent material; and in both cases, the sorbents are treated so that the CO2 is released from them and they can be re-used.

In January 2021 a consortium of Sizewell C, the University of Nottingham, and commercial contractors released a report DAC AND GGR INNOVATION PROGRAMME PROJECT NNB202043–HEAT-DRIVEN DIRECT AIR CAPTURE POWERED BY NUCLEAR POWER PLANT into a pilot study ('Phase 1') of the project.

...The research has demonstrated that stable air circulation can be achieved by applying a set heat input (which can be provided by a low-carbon source such as nuclear energy) to the process, and that UoN’s high performing carbon capture sorbent can achieve an uptake of 80% of its equilibrium capacity with only a 45 second contact time in air. The experimental phase also identified that the effect of a crosswind moving across the outlet of the air-sorbent contactor has a positive impact on the performance of the system, and during periods of elevated wind speed a significant reduction in the heating requirements of the DAC system could be seen. The experiments performed using a lab-based pilot plant have enabled the process design for a 100t CO2/year demonstration plant to be completed. The construction and delivery of this plant in a future phase (if selected) will enable further process development and optimisation to be performed.

An article 'Megatonne' CO2 capture plant plan for Sizewell C published on 13 June 2022 on the World Nuclear News website describes the project:

The idea is to utilise heat (steam) from the turbine installation at Sizewell C power station when it is operational, removing CO2 from the ambient air where the concentration is around 400ppm by placing large volumes of air in contact with chemicals known as sorbents using an adsorption system, where the CO2 adheres to the solid surface of the sorbent material. The sorbents are then treated so that the CO2 is released from them and compressed for storage or reuse, while the adsorbent materials can also be re-used.

Their proposal is to build the demonstration plant, at an estimated cost of GBP3.0 million (USD3.7 million), on a plot about 12 metres by 20 metres at, or around, the Sizewell C site, saying: "The key advantage of siting the demonstration plant in or around the wider Sizewell C estate is that the environmental conditions that the adsorber column is exposed to will be representative of the potential commercial scale plant for integration with Sizewell C, subject to any necessary permissions and other consents being secured at the appropriate time."

During the phase 1 trial the team discovered that a crosswind increased the efficiency of the system, but says that one area of study with the demonstration plant would be any impact of sea salt in the air, at the coastal location.

"Once significant data has been generated from the demonstration plant, giving further confidence in the technology’s commercial potential," the next stage of the plan is to progressively scale up to capturing 50,000 tonnes CO2/year by 2030 and "we are exploring opportunities to make use of heat sources from other nuclear plants in the UK".

It will then further scale up to the plant linked to Sizewell C "capable of capturing CO2 on a Megatonne scale", although it adds that "an alternative nuclear (or other) plant needs to be identified with a heat source that could drive the process, as Sizewell C would not be in place by this time, but of course Sizewell C will be capable of driving carbon capture solutions at a megatonne scale when operational in the 2030s".

The consortium's report also notes that the high-cost currently associated with direct air capture has been a "major barrier to the development of a significant UK market" but says the use of "future low-cost, low-carbon heat available from a nuclear power plant" means it could achieve the goal of removing CO2 at a megatonne scale at a cost of less than GBP200 per tonne of CO2 removed.

For that commercial-scale plant, Sizewell C is proposing to extract up to 400 MWt of heat from the nuclear power plant once operational. A "minor modification to the power plant design will be required to implement cogeneration", but Sizewell C "does not expect any significant change to the replication of the design from Hinkley Point C or its safety case at this stage".

Footnotes and references