Achieving high power heat-recovery systems using molecularly-complex fluids

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Achieving UK and EU emissions targets requires a transformation in the power generation and manufacturing industries. In the UK we consume 350TWhr of electricity every year, but with modern power-stations which are typically around 50% efficient a large proportion of energy is wasted as rejected heat. Recovering just 10% of this heat would save the equivalent power output of 22 power stations. This is not to mention the heat which could be recovered from manufacturing industries where large quantities of energy are wasted through the heating and cooling during metal-forming processes. In order to make heat-recovery economically viable, low-temperature Organic Rankine Cycles (ORC) can be deployed using fluids with boiling-points close to ambient temperatures, such as many 'molecularly-complex' fluids. The power is extracted in an ORC across a turbine, where these 'molecularly-complex' fluids exist in a gaseous state, and pass through the turbine at high speeds. Increasing the power extracted from the turbine makes heat-recovery systems much more economically favourable and can be achieved by raising the pressure ratio across the turbine. In order to do this efficiently requires a better understanding of molecular-complex gas flows because there is very little known about these complex flows in turbines. The lack of an in-depth understanding of the molecular complex gas-dynamics in ORC turbines means that it is unlikely that optimum power levels are being achieved with present-day design methods.Therefore this proposal aims to determine methods of significantly increasing heat-recovery system power outputs by exploiting the effects of molecular complexity in Organic Rankine Cycle turbines. A target is set of doubling current turbine power levels. In order to determine methodologies to achieve this, a combination of experimental and computational tests are planned. Experiments of molecularly complex gas flows will be studied using a specially designed experimental test-rig which will be able to mimic the flow conditions found in the ORC turbine. The computational simulations will involve the use of a research flow-solver, which will be modified to account for molecular-complex gas properties. The experimental data will aid the development of an accurate computational model, which will then be used to determine novel turbine blade designs to operate at high pressure ratios.This research will directly benefit both the fluid-mechanics research community and the power-generation industry. The research will improve our fundamental understanding of the fluid mechanics of molecularly complex fluids, and will also aid the development of sustainable power generation technologies. An improved understanding of molecular-complex gas flows in turbines has the potential to substantially reduce the UK's fossil fuel dependence and improve our ability to recover currently otherwise 'wasted' heat from power stations and manufacturing processes as well as solar and geothermal radiation. This has a large societal benefit both in-terms of aiding the fight against climate-change and improving the UK's energy security. This work will help towards meeting the targets of the UK Climate Change Act 2008 to reduce by 34 percent our greenhouse gas emissions by 2020 and 80 percent by 2050, against the 1990 baseline.