Technical Evaluation of a Stand-Alone Photovoltaic Heat Pump Dryer without Batteries

Antonio Quijano, Celena Lorenzo (), Antonio Berlanga and Luis Narvarte
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Antonio Quijano: Instituto de Energía Solar, Universidad Politécnica de Madrid, 28031 Madrid, Spain
Celena Lorenzo: Instituto de Energía Solar, Universidad Politécnica de Madrid, 28031 Madrid, Spain
Antonio Berlanga: GENAQ, 14900 Córdoba, Spain
Luis Narvarte: Instituto de Energía Solar, Universidad Politécnica de Madrid, 28031 Madrid, Spain

Energies, 2024, vol. 17, issue 18, 1-17

Abstract: This paper presents the results of the technical validation of an innovative prototype for drying alfalfa bales. It is based on a 4.1 kW Heat Pump (HP) that uses an advanced technology (optimized for extracting the humidity from the air) and is directly powered by a 6.6 kW p PV generator without grid or batteries support. The main technical challenges of this work were managing solar irradiance fluctuations due to cloud-passing and achieving good drying efficiency. The prototype has been validated for two consecutive drying campaigns in La Rioja (Spain). There were no abrupt stops generated by cloud-passing. The PR PV , which evaluates the performance of the PV system only during the periods when the PV energy can be used by the HP unit, presented values of 0.82 and 0.85, comparable to a well-performing grid-connected PV system. Although the bales’ initial relative humidity (RH) ranged from 18 to 30%, all but one of them presented a final RH below 16%, which is the limit point to avoid fermentation. The drying times ranged from 1 to 5 h, and the specific energy consumption per liter of water extracted, from 0.7 to 1.46 kWh/L. These values are comparable to traditional diesel and grid-powered systems. It is worth noting that the agricultural drying market represented USD 1.7 billion in 2023.

Keywords: photovoltaic; heat pump; dryer; stand-alone photovoltaic heat pump (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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