Bio-CO2: Power Generation and Heat Recovery from Biomass with Advanced CO2 Thermodynamic Power Cycles and Novel Heat Exchanger Designs

Lead Research Organisation: University of South Wales
Department Name: Faculty of Computing, Eng. and Science


In the UK, power generation is achieved mostly through the combustion of fossil fuels from remote power stations at a low-efficiency rate of 40%. This can lead to a large depletion of energy resources and pollution to environment. In reality, after taking into consideration long-distance power transmission and distribution losses, the generation efficiency tends to be further reduced to around 32% at the power supply end. To combat this problem, a local and decentralised combined heat and power (CHP) system may be used to attain not only 30% electrical efficiency but also over 50% heating efficiency, which would significantly improve the energy utilisation rate. In areas with simultaneous heating and electricity demand including supermarket and district heating, such systems would be a viable economic option. However, currently most CHP systems still require fossil fuel energy resources, which diminish both their energy-saving merit and potential CO2 emission reductions. Therefore, it would be highly desirable to promote the use of localised renewable resources, such as biomass fuels, with optimised CHP system engineering designs.

Currently, there are two main biomass CHP systems: biomass gasification with gas/steam turbines and biomass combustion with Organic Rankin Cycles (ORC). However, these biomass CHP systems cannot be further developed or extensively applied before the resolution of certain critical issues. These include achieving an acceptable thermal efficiency, compact system size, environmentally-friendly working fluid, advanced thermodynamic power cycles, optimal system design and control, and flexible operation etc. On the other hand, for power generation with medium to high temperature heat sources, CO2 supercritical Brayton cycles (S-CO2) can predominate over conventional ORCs in terms of thermal efficiency, environmental impact and system compactness. The S-CO2 systems have been applied in large-scale waste heat recovery of nuclear power plants but have not yet been utilised in biomass power generations due to various unsettled challenges. In this proposed project, a small-scale biomass power generation system with advanced CO2 supercritical Brayton cycles and novel heat exchanger designs will be investigated experimentally and theoretically. The investigation will address the challenges involved in the proposed system including innovative designs of thermal drive CO2 supercritical compressors, precise CO2 parameter controls at the S-CO2 compressor inlet, novel designs of supercritical CO2 heat exchangers and comprehensive understanding of the complex heat transfer and hydraulic processes involved. In addition, a detailed transient model of the biomass S-CO2 power generation system will be developed which will enable the system to be further optimised and scaled up for actual design and operation.

Planned Impact

The impact of the research will be widespread and varied. It is highly relevant to many sectors including: (i) Industry - The success of this project will directly contribute the performance evaluations and improvements of developing technologies such as thermal driven CO2 supercritical compressors, biomass CO2 supercritical heaters, CO2 supercritical recuperators, as well as the application and control of CO2 supercritical Brayton cycles (S-CO2). It will have long-term influence on the biomass industry by enabling high efficiency power generation and more flexible operations. ii) End-users- UK domestic houses particularly in rural areas with limited power supply have rich energy resources of waste wood/pellet which can potentially be used by the proposed biomass-fired S-CO2 system as fuel for generating electricity and producing heat. This proposal will also benefit other end-user types such as schools, out-of-town retail, leisure developments ,district heating networks and other commercial buildings where biomass resources are available and both electricity and heating/cooling are simultaneously demanded. (iii) Academics - This project will contribute to the investigation and development of a new biomass-fired power generation systems with advanced CO2 supercritical Brayton cycles (S-CO2), its design and selection of main components, and social impacts and business infrastructure. (iv) Government - This project is a prompt response to the government's recent targets for CO2 emission reduction and enhanced utilisation of renewable energy. The proposed programme will support and enhance the achievements of these targets in order to have a significant impact on the policy implementation of biomass power generation and demand side management.

The industrial, end users' and government impact will be achieved through direct industrial interaction and knowledge transfer. Ashwell Biomass Ltd, Kelvion Searle , Entropea Labs Ltd , and SWEP International Limited which are the potential manufacturers of the proposed technology, are directly involved in the project. Residential houses in rural areas and district heating networks in urban areas are our potential users of the proposed product and technology. Our outcomes will also be disseminated through various knowledge transfer networks as well as application-oriented magazines to maximize impact. The academic impact will be achieved via article publications and conferences/seminars events. We will keep publishing our findings in a timely manner in top peer-reviewed journals and conferences. We will also report our outcomes to other relevant programmes such as Sustainable Energy Use in Food Chains' (CSEF) programmes to attract attention in this new area, with the ultimate goal of establishing a society for biomass-fuelled CO2 power generation research. In addition we will be involved in two new developed master programs in Renewable Energy Engineering at Brunel University.

Related Projects

Project Reference Relationship Related To Start End Award Value
EP/R000298/1 01/09/2017 11/01/2018 £198,383
EP/R000298/2 Transfer EP/R000298/1 11/04/2018 02/09/2020 £181,143
Title A brief video introduction for the research project 
Description A brief video introduction for the research project was made. This includeed the test rig explanation , research outcomes and further development in this area. 
Type Of Art Film/Video/Animation 
Year Produced 2015 
Impact The video has demonstrated clearly the development , operation and application of the project. This will facilitate potential future collaboration and development in this area. 
Description The current project is on power generation with biomass combustion and CO2 transcritical/supercritical Brayton cycles. Comparing to the CO2 transcritical Rankin cycle, a CO2 transcritical/supercritical compressor is applied instead of CO2 transcritical liquid pump. Subsequently, the work consumption of CO2 compression is significantly reduced and thus the increase of system thermal efficiency. In addition, the system operation is more stable due to the application of CO2 compressor.
Exploitation Route The research findings will be taken forward by means of public publications such as journal and conference papers. The findings will also be demonstrated to public through seminars and meetings etc. The findings can be used to different users such as academics , manufacturers and industries.
Sectors Agriculture, Food and Drink,Communities and Social Services/Policy,Creative Economy,Education,Energy,Environment,Government, Democracy and Justice,Manufacturing, including Industrial Biotechology,Retail,Transport

Description The findings have been used by a number companies such as Ashwell Biomass Ltd who has modified their biomass boiler into biomass supercritical CO2 heater. This has extended their product applications in the market. A transcritical CO2 compressor which is currently used in refrigeration has now been installed in the test system. This can enhance the market applications of the CO2 compressor. The test rig of biomass-CO2 power generation system is new and can be applied by academics and industries with different applications. The publications of research outcomes from this project will be used by a number of users including academics, manufacturers an industries.
First Year Of Impact 2018
Sector Agriculture, Food and Drink,Communities and Social Services/Policy,Creative Economy,Energy,Environment,Manufacturing, including Industrial Biotechology,Transport
Impact Types Cultural,Societal,Economic,Policy & public services

Description Impact on the waste heat recovery project
Geographic Reach Asia 
Policy Influence Type Influenced training of practitioners or researchers
Impact The power generation with biomass combustion exhaust flue gases or renewable energy and CO2 power cycles will greatly reduce the fossil fuel consumption in power generation and thus reduce the CO2 emissions, air pollution and risk of energy resource . The research outcomes can benefit both renewable energy, waste heat recovery , energy savings , economic and environmental sustainability.
Description Quality Related funding (QR)
Amount £10,000 (GBP)
Organisation University of South Wales 
Sector Academic/University
Country United Kingdom
Start 02/2018 
End 01/2019
Title Design and modelling of power generation system with biomass and CO2 transcritical or supercritical power cycles 
Description The power generation system with biomass combustion and CO2 transcritical/supercitical power cycles works at very high pressures of above 90 bars and very high temperature around 500^C. The components in the system including gas generator, recuperator, turbine and compressor and gas cooler etc need to be special designed , manufactured and operated which have been conducted from this project. In the meantime, a detailed model of the tested biomass-CO2 power system has been developed and validated by the test results. The experience of the biomass-CO2 power system design can be applied into the following projects in this area. In addition, the developed system model can be used as an efficient tool to evaluate , optimize and practical system scale-up. 
Type Of Material Improvements to research infrastructure 
Year Produced 2018 
Provided To Others? Yes  
Impact The experience of the biomass-CO2 power system design can be applied into the following projects in this area. In addition, the developed system model can be used as an efficient tool to evaluate , optimize and practical system scale-up for the new systems to be developed in the near future. 
Title Mathematical model of power generation system with CO2 transcritical power cycles 
Description A model of power generation system with CO2 transcritical power cycles has been developed and validated with the corresponding test results. The system model is an integration of a number of system component models including CO2 turbine, recuperator, air cooled condenser, liquid pump , gas generator and controls. The model can be used to evaluate and optimize the design and performance of the system and components and will be able to achieve system scale-up for actual installation. 
Type Of Material Computer model/algorithm 
Year Produced 2015 
Provided To Others? Yes  
Impact The developed and validated models of the CO2 power generation system and components can be used as an efficiency tools for the system performance evaluation , optimization and potential system scale-up for actual installations. The model simulation can generate more prediction results and data at extensive operating states which will be very helpful to understand the system operations , controls and component heat transfer processes. 
Description Power generation with biomass and CO2 power cycles 
Organisation Ashwell Biomass Ltd
PI Contribution A test rig of 5 kWe power generation system with the heat source from biomass exhaust flue gases and CO2 transcritical/suercritical power cycles has been built up. The industrial partners have provided some main system components including a 100kWth biomass boiler and some heat exchanngers etc. The industrial partners have also involved in the test rig design and component selections. The biomass boiler and an external air cooler have been built and integrated with the main CO2 power generation rig. The power supply , control and data logging systems have also built up. The rest rig is nearly ready to operate and the designed experimental investigation will be carried out soon. In the mean time, a model of the tested system has been developed and validated by the test results. The validated model has been utilized to evaluate , compare and optimize the system design and operation at different operating conditions.
Collaborator Contribution Ashwell Biomass Ltd has provided a modified 100 kWth biomass boiler and made it applicable to the test rig of this project. Ashwell has also involved in the specifications of the biomass boiler control and operation, biomass storage and heat exchanger design. SWEP has provided a plate CO2 gas cooler and its design for the test rig. Kelvion Searle and Entropea Labs have involved in the the designs of heat exchangers used in the new test rig.
Impact 1) A multi-functional and high precision test rig of a power generation system with biomass combustion heat source and CO2 transcritical/supercritical power cycles has been designed and developed. 2) The complex energy conversion processes involved in the CO2 power system have been thoroughly investigated and valuable performance data through the use of advanced measurement technologies has been obtained. 3) The simulation models for the CO2 power system and components have been developed and will be validated with experimental results. 4) The heat transfer and thermal behavior of major components, particularly CO2 gas heaters, condenser and expander in the CO2 power system, and system thermal and exergy efficiencies have been analysed through simulation modelling. 5) The operational specification for the CO2 power system has been prepared.
Start Year 2017
Title Design software for the power generation system with biomass combustion and CO2 transcritical/supercritical power cycles. 
Description Based on the developed model of the power generation system with biomass combustion and CO2 transcritical/supercritical power cycles, a corresponding software has also been developed. This software can facilitate for the system design and optimization of different system component designs and controls at different operating state. This can be an efficient tool for the system and component designs and selections at a specific design conditions and requirements. 
IP Reference  
Protection Copyrighted (e.g. software)
Year Protection Granted
Licensed No
Impact This software can facilitate for the system design and optimization for different system components and system controls at different operating state. This can be an efficient tool for the system and component designs and selections at a specific design conditions and requirements. The software can also be used as an efficient too for the system scale-up so as to facilitate actual installation.
Title Design software for power generation with biomass combution and CO2 transcritical/supercritical power cycles 
Description Based on the developed and validated models of the tested power generation system with biomass combution and CO2 transcritical/supercritical cycles, a design software of the corresponding system and components has been developed. 
Type Of Technology Software 
Year Produced 2018 
Impact The software will facilitate the system performance evaluation and optimization and potential system scale up for actual installation and operation. 
Description FLEXIS Young Researchers Conference 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact The conference of 'FLEXIS Young Researchers Conference' was held at Cardiff on Friday 13th July 2016.
The conference is designed to:
i) Bring together academic and industry leaders with interest in waste heat recovery and its efficient utilisation
ii) Share knowledge of both products and applications
iii) Learn of recent and emerging technology developments

More than 100 people mostly from both academics and Industries in the UK attended this event. Potential collaborations between University f South Wales and industries and other institutions are expected in the area of waste heat recovery.
Year(s) Of Engagement Activity 2018