A new trigeneration study just published at Renewable Energy is a collaboration between Fatih Yilmaz from Isparta University of Applied Sciences in Turkiye, and Basharat Jamil from Spain’s IMDEA Energy Institute in Madrid.
They have proposed a concept in which three power cycles would be deployed in sequence to supply electricity, heating, and freshwater generation to help with energy and water needs in New Delhi, India in a mini 4 MW power plant.
Heat would be delivered as space heating. The electricity from two of the three cycles would deliver electricity to the grid and the third would run a reverse osmosis (RO) desalination project to provide freshwater.
Capturing the waste heat from each of the three power cycles in sequence is key to this trigeneration concept.
The three power cycles are a high-temperature Brayton cycle, a medium-temperature Rankine Steam cycle, and for the lowest temperature heat – an Organic Rankine Cycle (the power cycle used to capture low-temperature heat to generate electricity for the geothermal industry).
The energy input is a high temperature heat transfer fluid that captures the heat of a concentrated solar heliostat field of mirrors directed to a solar receiver atop a tower. (How Tower CSP works)
1. Solar heat transferred at 790°C would supply a helium-gas-driven Brayton cycle, generating electricity and supplying some heat at 60°C for commercial space heating.
2. Waste heat from this first power cycle would then be fed at around 360°C to run a Rankine Steam cycle, producing only electricity.
3. Finally, waste heat from this second power cycle is sent to run a low-temperature ORC at 90°C, generating the electricity to run a Reverse Osmosis desalination plant.
Recaptured heat
“We are trying to recover the heat losses,” explained co-author Basharat Jamil, a researcher at IMDEA’s High Temperature Processes Unit.
“So the waste of one cycle is useful for another cycle. This way, we will be able to increase efficiency and reduce waste. Multi-generation cycles have to have multiple outputs, but they have to have relatively higher efficiency.”
Their paper (Parametric and a case study of an innovative solar-driven combined system: Thermodynamic and environmental impact analysis for sustainable production of power, heating, and freshwater) was published in January. It includes a review of all previous trigeneration studies involving concentrated solar thermal as the input energy source.
“Our system aimed to design something that has improved efficiency compared to previous ones,” he noted.
“That’s why, when we did the parametric study, also we picked up potential parameters from the literature. So the focus wasn’t about the compression ratio – though we studied it parametrically as well, to quantify how much it varies between to impact the outputs. But the overall aim here is to propose an efficient configuration.”
Proposed trigeneration system would be for New Delhi, India
The system was a first—specifically designed for deployment in New Delhi, India, where the weather is highly variable. New Delhi has a humid, subtropical climate, with high-heat summers, the monsoon, and very cold winters.
More than 90% of India receives an average insolation above 5 kWh/m2/day, with a maximum recorded at 7.5 kWh/m2/day in certain regions.
“But these do not reflect annual sunshine hours, because in July and August, India experiences a heavy monsoon season. So we wanted to do the first study using the actual data from the weather of New Delhi,” Explained Jamil.
“So the expected sunshine hours and the actual sunshine hours are less. Some other parts of India, like Rajasthan or the western part, receive even 300 sunny days yearly. So in a large portion of India there is enormous potential for solar energy. I know that Reliance Infrastructure is right now building concentrated solar power plants in the Rajasthan region of India because my colleagues are directly working on these plants. ”
The thermodynamic analysis of their trigeneration concept found annual average energy efficiency of 25.12% and exergy efficiency of 17.64%. The outputs include 3.7 MW of net electricity, 871 kW of industry heating, and 33.52 mÂł/h of freshwater production.
Over 90% efficient energy storage improved by flowing heat round two pebble layers
