Power Generation and Heat Recovery from Industrial Waste Heat with Advanced CO2 Thermodynamic Power Cycles (CO2Power)

he vast volumes of waste heat rejected from industrial processes can be converted into electricity and useful heat through advanced energy conversation technologies. In this project, a test rig of a small-scale power generation (up to 5kW) and heat recovery system will be established with a heat source temperature between 100 ^C and 500 ^C, which is representative of actual industrial waste heat. The natural refrigerant CO2 will be engaged as a working fluid in the system, considering its excellent thermophysical properties and negligible environmental impact. Corresponding to the large temperature range of the heat source, the CO2 supercritical Rankine cycle will be applied for temperatures below 350 ^C, otherwise, combined CO2 Brayton and supercritical Rankine cycles will be employed. Simultaneously, a detailed mathematical model for the proposed system will be developed and validated with measurements. The model will then evaluate, compare and analyse different system and component designs, heat recovery potentials and control optimisations which will eventually lead to optimal design and construction of the proposed system.

In the UK and even whole worldwide, currently around 70% of the electricity consumed is generated by burning fossil fuels in central power stations. The extensive consumption of fossil fuels has caused significant atmospheric pollution, global warming and rising energy costs. One of the critical challenges of the 21st century for the UK government is to cooperate with all other countries in the world to tackle these risks surrounding excessive CO2 emissions by replacing fossil fuels with waste heat and renewable energy sources for the power generation. This is essential to meet the government's target to reduce the UK CO2 emissions by 80% of 1990 levels by 2050. It is therefore imperative to continue improving the capability and competiveness of manufacturing industry particularly in the energy sector. With increasing electricity demand year on year, CO2 emissions will increase if power generation cannot be decarbonised. The development of high efficiency low and medium temperature electricity generation systems with advanced CO2 combined Brayton and supercritical Rankine power cycles can make substantial contributions to the national and international efforts of saving energy resources and CO2 emissions.

The manufacturing capability in the UK energy sector is relatively weak, particularly in power generation with low and medium temperature energy resources from industrial waste heat and CO2 combined Brayton and supercritical power cycles. There are currently a range of low temperature nonCO2 ORC products in the market, but they are mostly designed and manufactured from outside of the UK. The research programme proposed here will build on the fundamental understanding of the low and medium temperature energy conversation system for industrial waste heat with the CO2 combined power cycles and their design and control optimisation to provide maximum efficiency over a wide range of conditions. The project will increase the technical knowledge and CO2 supercritical power generation system manufacturing capability in the UK. This should enhance their share of the expanding local and export markets for CO2 power components and systems. It will also provide training and employment opportunities in the UK energy and manufacture sectors

The UK research community is underrepresented in the international effort to develop efficient CO2-based low and medium temperature power generation systems and equipment. The applicants in this proposal are leading the research in the UK on CO2 refrigeration systems , thermodynamic cycle analyses and heat exchangers and the outcomes from this project pave the way for wider engagement of the academic community in the research on CO2 supercritical power systems. The research will provide insights into the design and optimisation requirements of the CO2 gas heaters and expanders at different flow and heat transfer regimes. The models, operational data, and fundamental knowledge developed will inform the work of other researchers, and this should accelerate the design, control optimisation and deployment of efficient CO2 supercritical power systems to the market and contribute to significant reductions in CO2 emissions to the environment.

Project outputs will be widely disseminated by Brunel University and the industrial partners to raise awareness the development, technology, design and manufacture of the new system. Seminars and presentations will be given at the university and meetings of professional and trade organisations such as the Institute of Energy. Publicity material will be fed through to large energy sectors to raise awareness of the new product offerings. The research will also be communicated through papers in high-impact, peer reviewed journals and presentations at a wide variety of conferences.