Low Temperature Waste Heat to Power Generation

来自工业过程和机构建筑的大部分废热（超过60%）是低品位热，这使得其难以在设施内直接利用，也降低了使用朗肯或有机朗肯循环（ORCs）发电的潜力。orc还要求在热源和散热器之间保持足够的压力和温差，以便为涡轮机提供足够的膨胀能量。这限制了热源可以冷却到的温度和热回收和发电的潜力。该项目的主要目标是通过开发一种创新的低温热能转换系统来克服传统技术的局限性，该系统可以从低温废热流中回收能量。该项目通过以下方式解决能源三难问题：1)减少排放：利用低温废热发电和取代化石燃料的使用。ii)供应安全：利用废热发电将减少所需的初级燃料的数量，并提供一种替代能源供应来源。3)节约成本：利用余热将为用户节省大量成本。该系统将在热源温度为75℃至90℃时进行优化，以达到最高效率，从而最大限度地扩大应用范围和潜在市场。它将按照我们所说的“控制相循环（CPC）”运行。CPC是三边闪蒸循环（TFC）的一种变体，TFC是一种三段式动力循环，其中工作流体在高压下从饱和液态膨胀到低压下的两相状态，然后在膨胀器中排出热量并在冷凝器中冷凝。产生的液体然后由进料泵压缩到更高的压力水平，然后由热源加热（废热流）并重新膨胀。与ORC相比，“湿”膨胀显着增加了功率输出。由于可用的膨胀器效率低，寄生损耗高，特别是泵送功率大，TFC尚未商业化。这些缺点将通过本项目的创新来克服，包括：1)在膨胀前控制流体的质量到高湿分数，以提高膨胀效率；ii)热力代替机械泵送液体从冷凝器到膨胀压力；iii)创新的热交换器设计和控制，最大限度地从废热流中转移热量，最大限度地减少压力损失；4)改进螺杆膨胀机转子外形，进一步提高效率。该项目将导致安装一个概念验证系统，用于在乳制品工厂进行演示和评估。

Most of the waste heat (more than 60%) from industrial processes and institutional buildings, is low grade heat which makes its direct use within the facility difficult and also reduces the potential for power generation using Rankine or Organic Rankine Cycles (ORCs). ORCs also require that adequate pressure and consequently temperature differential is maintained between the heat source and heat sink to provide sufficient expansion energy for the turbine. This limits the temperature that the heat source can be cooled down to and the heat recovery and power generation potential. The Main aim of this project is to overcome the limitations of conventional technologies by developing an innovative low temperature heat to power conversion system that can recover energy from low temperature waste heat streams. The project addresses the energy trilemma through: i) Reduction of Emissions: by generating electricity from low temperature waste heat and displacing fossil fuel use. ii) Security of supply: the generation of electricity from a waste heat will reduce the amount of primary fuel required and provides an alternative source of energy supply. iii) Cost savings: using waste heat will result in significant cost savings for the users. The system will be optimised for maximum efficiency at heat source temperatures 75 C to 90 C to maximise the range of applications and potential markets. It will operate on what we term 'Controlled Phase Cycle (CPC)'. The CPC is a variant of the Trilateral Flash Cycle (TFC), which is a 3-leg power cycle in which the working fluid expands from saturated liquid state at high pressure to a two-phase state at lower pressure in an expander before rejecting heat and condensing in the condenser. The resulting liquid is then compressed by a feed pump to the higher pressure level before is heated up by the heat source (waste heat stream) and re-expanded. The 'wet' expansion increases significantly the power output compared to the ORC. The TFC has not been commercialised as yet, due to the low efficiency of available expanders and high parasitic losses, particularly pumping power. These shortcomings will be overcome by innovations in this project which include: i) Control of the quality of the fluid before expansion to a high wetness fraction to increase expansion efficiency;ii) Thermal instead of mechanical pumping of the liquid from the condenser to the expansion pressure; iii) Innovative heat exchanger design and controls to maximise heat transfer from the waste heat stream and minimise pressure losses;iv) Improved screw expander rotor profile to further increase efficiency. The project will lead to a proof of concept system to be installed for demonstration and evaluation in a dairy facility.