Efficiency analysis and evaluation 4E of a hybrid solar photovoltaic-electric dryer for Brewer’s Spent Grain drying

Abstract

Brewer’s Spent Grain (BSG) is the main by-product of the brewing industry and, due to its high moisture content, presents challenges for storage, transportation, and valorization. When properly dried, however, BSG becomes a biomass with significant energy potential. Considering the high energy demand associated with drying processes, this study evaluated the performance of a photovoltaic-assisted hybrid solar dryer through an integrated energy, exergy, economic, and environmental (4E) assessment. Four operating conditions were investigated, combining different biomass loads and electrical resistance heating strategies. The results showed that overall drying efficiency ranged from 9.51 to 13.16%, while specific energy consumption varied from 5.07 to 7.01 kWh kg −1 . Exergy analysis revealed low exergetic efficiencies, particularly under nighttime operation, where values decreased to approximately 1.0% due to increased irreversibilities and thermal losses. Among the evaluated conditions, continuous electrical heating with a higher biomass load provided the most balanced performance, achieving satisfactory moisture reduction, lower specific energy consumption (6.61 kWh kg −1 ), a payback period of 3.72 years, and cumulative CO 2 mitigation of approximately 2.0 tons over a 10-year lifetime. The dried BSG presented a higher heating value above 15 MJ kg −1 , confirming its potential as a bioenergy resource. The results demonstrate the applicability of integrated 4E analysis for identifying the benefits and limitations of hybrid solar drying systems and provide a basis for future optimization of BSG drying technologies.

The authors' abstract, as published at the source. Thermal Science and Engineering Progress, 2026 · DOI ↗