Heat Pump Water Heaters (HPWH) are systems conceived for efficient production of Domestic Hot Water (DHW). The attention for this systems is constantly increasing in many European countries. The subject of this study are air to water HPWHs called Air Source Heat Pump Water Heaters (ASHPWH) or Thermodynamic Water Heaters (TWH) which consist in a heat pump cycle having external air as cold sink and delivering heat to a thermal storage tank. This study focuses on the techno-economic evaluation of innovative solutions aiming to improve ASHPWHs performances. In a first time, preliminary in depth market study and state of the art study are carried out in order to highlight the basic and most used model along with interesting improving solutions eligible to be implemented (such as inverter compressor, microchannel condenser and double stage vapour injection compression). In a second time inverter compressor technology is thoroughly implemented, both in a detailed Modelica based model and in an experimental system. Three modelling methods are presented and compared. Experimental validation is carried out with good results, having a mean relative percentage error of 16,01%, 1,97% and 3,70% respectively for refrigerant mass flow rate, total compressor electric power and refrigerant discharge temperature after the compression, all at the reference conditions (compressor rotation frequency of 50Hz). Annual simulations are made to assess new control strategies emerging on the HPWH market based on inverter compression such as fixed condenser power aiming to increase comfort by providing a fixed heat-up time, and Smart Control where the tank water temperature set point is controlled based on daily tapped energy records. Finally, a parametric study is performed, which shows that the optimal compressor rotation frequency to maximize performances (COP) varies according to the external air temperatures, in particular it assumes values between 30 and 60 Hz for external air temperatures ranging between -10°C and 20°C. These results disclose important hints for future developments.
Gli Heat Pump Water Heaters (HPWH) sono sistemi sviluppati per una efficiente produzione di acqua calda sanitaria. L'attenzione verso questi sistemi è in costante aumento in molte nazioni Europee. Il soggetto di questo studio sono gli HPWHs aria-acqua chiamati Air Source Heat Pump Water Heaters (ASHPWH) o Thermodynamic Water Heaters (TWH) i quali consistono in un ciclo a pompa di calore che utilizza l'aria esterna come "serbatoio freddo" e che fornisce calore a un serbatoio per lo stoccaggio d'acqua. Questo studio è incentrato sullo studio tecnico-economico di soluzioni innovative volte al miglioramento delle performance degli ASHPWHs. In un primo momento, uno studio di mercato e una ricerca bibliografica preliminari sono stati svolti per evidenziare il sistema base e più utilizzato, insieme a delle soluzioni di miglioramento interessanti e idonee ad essere implementate (come il compressore inverter, il condensatore a microcanule e la compressione a doppio stadio). In un secondo momento il compressore inverter è stato implementato, sia in un modello numerico basato sul linguaggio Modelica, sia in un sistema sperimentale. Tre metodi di modellizzazione sono presentati e comparati. La validazione sperimentale ha dimostrato buoni risultati: un errore relativo medio percentuale di 16,01%, 1,97% e 3,70% rispettivamente per la portata massica di refrigerante, la potenza elettrica totale del compressore e la temperatura di scarico del compressore, tutti misurati alla frequenza di riferimento (50Hz). Delle simulazioni annuali hanno confrontato alcune nuove strategie di controllo del compressore inverter come il metodo a potenza di condensazione fissa (mira ad aumentare il comfort producendo un tempo di riscaldo fisso) e lo Smart Control (la temperatura di set point del serbatoio è controllata da registrazioni giornaliere di utilizzo di acqua calda). Infine è stato svolto uno studio parametrico che mostra la frequenza di rotazione ottima del compressione per diverse temperature di aria esterna (tra -10 e 20°C). Questi risultati donano degli importanti indizi per gli sviluppi futuri.
Techno-economic study of air source heat pump water heaters
D'ANGELO, AXEL
2015/2016
Abstract
Heat Pump Water Heaters (HPWH) are systems conceived for efficient production of Domestic Hot Water (DHW). The attention for this systems is constantly increasing in many European countries. The subject of this study are air to water HPWHs called Air Source Heat Pump Water Heaters (ASHPWH) or Thermodynamic Water Heaters (TWH) which consist in a heat pump cycle having external air as cold sink and delivering heat to a thermal storage tank. This study focuses on the techno-economic evaluation of innovative solutions aiming to improve ASHPWHs performances. In a first time, preliminary in depth market study and state of the art study are carried out in order to highlight the basic and most used model along with interesting improving solutions eligible to be implemented (such as inverter compressor, microchannel condenser and double stage vapour injection compression). In a second time inverter compressor technology is thoroughly implemented, both in a detailed Modelica based model and in an experimental system. Three modelling methods are presented and compared. Experimental validation is carried out with good results, having a mean relative percentage error of 16,01%, 1,97% and 3,70% respectively for refrigerant mass flow rate, total compressor electric power and refrigerant discharge temperature after the compression, all at the reference conditions (compressor rotation frequency of 50Hz). Annual simulations are made to assess new control strategies emerging on the HPWH market based on inverter compression such as fixed condenser power aiming to increase comfort by providing a fixed heat-up time, and Smart Control where the tank water temperature set point is controlled based on daily tapped energy records. Finally, a parametric study is performed, which shows that the optimal compressor rotation frequency to maximize performances (COP) varies according to the external air temperatures, in particular it assumes values between 30 and 60 Hz for external air temperatures ranging between -10°C and 20°C. These results disclose important hints for future developments.| File | Dimensione | Formato | |
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2016_12_D'Angelo.pdf
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https://hdl.handle.net/10589/129781