Exergo-economics of industrial heat pumps performance through process modifications

In contrast, exergy-based methods led to the addition of either an internal heat exchanger or a flash vessel, both of which improved performance. The internal heat exchanger, in particular, increased the coefficient of performance from 2.3 to 2.8 and reduced operational costs by 0.8 M€ after 5 years, while also decreasing the initial investment by 135 k€ and total operational costs from 10.3 M€ to 8.7 M€. Advanced exergo-economic analysis further investigates the factors influencing SGHP performance, focusing on the required steam temperature and heat pump cycle configuration.

The results indicate that direct steam production via a mechanical vapor recompression (MVR) system is the most economically viable option. When direct production is infeasible, a single-stage subcritical (SS) cycle feeding steam at 80 °C into an MVR is optimal for steam temperatures above 130 °C. At intermediate temperatures between 80 °C and 130 °C, a closed cycle heat pump performs comparably or better, with the preferred configuration varying based on sink temperature and temperature lift.

These insights enhance the understanding of SGHP design and highlight pathways for industrial implementation, demonstrating that exergy-based methods are effective in selecting the right configuration for steam-generating heat pumps.