Abstract
Abstract This paper presents experimental investigation of low-temperature heat to electricity generation system based on Organic Rankine Cycle (ORC) using R152a as the working fluid. Both energy efficiency and exergy efficiency were analyzed based on the experiments. Although energy efficiency was low to 5.0% when the evaporating and cooling temperatures were 65°C and 11°C, respectively, the exergy efficiency reached 25%, which showed great competitiveness among low-temperature heat utilization technologies. To reveal the energy recovery proportion from the waste heat, both energy extraction efficiency and exergy extraction efficiency as well as energy and exergy loss paths were analyzed. When the heat source was 65°C, 14.9% of the maximum possible thermal energy in the heat source was absorbed by the organic working fluid, and 10.7% was transferred to the cooling medium. The power output contributed 0.64%. A total of 1.8% of the exergy in the heat stream flowed to the cooling medium. The start-up work takes dramatically 0.16% and 1.7% of energy and exergy, respectively. Other energy and exergy loss occurs due to the irreversibility of the heat transfer process and expansion process. Cascade ORC system could enlarge the temperature difference of the heat stream and raise the power output. However, the energy efficiency of the multi-stage ORC system is lower than single-stage system, since there was a downward trend of the temperature of heat source for the latter stage. ORC cycle can lower the temperature of heat source to 45°C.
Highlights
Converting low-grade heat into electric energy can effectively improve energy utilization efficiency and reduce environmental impacts
This paper presents experimental investigation of low-temperature heat to electricity generation system based on Organic Rankine Cycle (ORC) using R152a as the working fluid
It demonstrated that the ORC system was not applicable when the temperature difference between the heat and cooling sources was lower than 35◦C since the exergy efficiency was less than 8% and energy efficiency was lower than 2.3%
Summary
Converting low-grade heat into electric energy can effectively improve energy utilization efficiency and reduce environmental impacts. Over the last two decades, many efforts have been devoted to working fluid selection, component optimization, system integration and adaptability to multiple heat sources Expander is another key component, which converts thermal energy into electricity. Braimakis and Karellas [11] optimized a double-stage ORC cycle in a waste heat conversion system and compared its performance with several working fluids. The results showed that the double-stage ORC can raise the exergetic efficiency by up to 25%, depending on the heat source temperature and the working fluid used. Sun et al [17] analyzed the exergy efficiency of an ORC cycle and an ORC-based combined cycle driven by low-temperature waste heat. Since exergy contained in the low-temperature heat sources is relatively low, exergy efficiency is commonly used to evaluate the performance of energy utilization systems in conjunction with energy efficiency. The energy and exergy flow paths were analyzed to illustrate the causes of low energy efficiency and exergy efficiency
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
