Heat pumps are a technology that is gaining more and more importance because they allows to satisfy the energy needs of room heating and cooling and for production of domestic hot water, without directly using any fossil fuel but, by exploiting for more or less 2/3 the heat coming from the external environment and, for the remaining 1/3 electricity, which can be generated by renewable sources, such as solar PV. In order to study this situation, two Daikin Altherma 3 heat pumps have been installed in the Micro-Cogeneration Laboratory of the Energy Department of Politecnico of Milan, who is part of the bigger Multi-Good Micro-Grid Laboratory (MG2Lab), that deals with the micro grid of the Department. This thesis work regards the firsts steps of the heat pumps integration process in the micro-grid: the construction of a test rig, complete of all the measurement instruments needed to monitor the operation of the heat pumps and to calculate their performances; the calculation of the PID parameters, applying the Ziegler-Nichols closed-loop method, to be inserted in the control system of the laboratory to allow the complete automatic and remote control of the plant; the development of a first experimental campaign, with a series of repeated tests, at different working points, to verify the correct operation of the test rig and to have the first values of the performances. For the experimental data analysis, a more consistent procedure from a statistical point of view has been adopted instead of the classics procedures of the laboratory: for every tests, at first a steady state is extrapolated, then the charts of the autocorrelation and the residuals distribution are studied and, at the end, all the steady states are merged together and treated with the unweighted batch means method, in order to build Shewart control charts to establish the effective stationarity of the observed process and validate the results. The results show that in the case at 35 °C is not possible to observe a stationary process and therefore give the performances; on the other side, in the case at 45 °C, the process’ stationarity is observed and the performances calculations return lower values than the ones given by the manufacturer [1], in particular the electrical consumption is equal to 1.69 kW (13% more), the thermal power produced is equal to 5.54 kW (6.1% less) and this means that the COP is equal to 2.891 (17.4% less).
Le pompe di calore sono una tecnologia che sta sempre più prendendo piede in quanto permette di soddisfare i fabbisogni energetici di riscaldamento e raffrescamento degli ambienti domestici e di produzione di acqua calda sanitaria, senza l’impego diretto combustibile fossili, ma sfruttando per circa 2/3 il calore proveniente dell’ambiente esterno e per il restante 1/3 energia elettrica, che può essere prodotta da fonti rinnovabili, ad esempio tramite pannelli fotovoltaici. Al fine di studiare questa situazione, due pompe di calore Daikin Altherma 3 sono state installate nel Laboratorio di Micro-Cogenerazione del Dipartimento di Energia del Politecnico di Milano, il quale fa parte del più grande Multi-Good Micro-Grid Laboratory (MG2Lab), il quale si occupa della micro-rete interna al Dipartimento. Il lavoro di questa tesi riguarda la parte preliminare all’integrazione delle pompe di calore nella micro rete: la realizzazione di un banco prova provvisto di tutti gli strumenti di misura necessari per monitorare il funzionamento delle pompe di colore e stabilirne le prestazioni; il calcolo dei parametri PID, applicando il metodo di Ziegler-Nichols, da inserire nel sistema di controllo del laboratorio per poter controllare tutto l’impianto automaticamente ed in remoto; lo svolgimento di una prima campagna sperimentale, formata da una serie di prove ripetute nel tempo, a differenti punti di funzionamento, per verificare il corretto funzionamento del banco prova e le prestazioni della macchina in stato stazionario. Per l’analisi dei dati sperimentali rilevati durante la campagna di prove, viene utilizzata una procedura più consistente da un punto di vista statistico rispetto alle classiche procedure del laboratorio: per ogni prova viene dapprima isolato uno stato stazionario, poi vengono studiati i grafici di autocorrelazione e la distribuzione dei residui ed infine vengono tutti accorpati e trattati con il metodo delle medie batch non pesate al fine di potere costruire delle carte di controllo di Shewart per potere così stabilire l’effettiva stazionarietà del processo osservato e validare i risultati. I risultati mostrano che nel caso a 35 °C non è possibile osservare un processo stazionario e quindi validare i valori delle prestazioni; al contrario, nel caso a 45 °C, la stazionarietà del processo è osservata ed il calcolo delle prestazioni ritorna dei valori inferiori rispetta a quelli indicati sul sito del costruttore [1], in particolare consumo elettrico 1.69 kW (13% in più), potenza termica prodotta pari a 5.54 kW (6.1% in meno) che si traducono in un COP pari a 2.891 (17.4% in meno).
Construction of a test rig for heat pumps in a microgrid and application of a statistical protocol for steady state analysis
SALDARINI, SAMUELE
2018/2019
Abstract
Heat pumps are a technology that is gaining more and more importance because they allows to satisfy the energy needs of room heating and cooling and for production of domestic hot water, without directly using any fossil fuel but, by exploiting for more or less 2/3 the heat coming from the external environment and, for the remaining 1/3 electricity, which can be generated by renewable sources, such as solar PV. In order to study this situation, two Daikin Altherma 3 heat pumps have been installed in the Micro-Cogeneration Laboratory of the Energy Department of Politecnico of Milan, who is part of the bigger Multi-Good Micro-Grid Laboratory (MG2Lab), that deals with the micro grid of the Department. This thesis work regards the firsts steps of the heat pumps integration process in the micro-grid: the construction of a test rig, complete of all the measurement instruments needed to monitor the operation of the heat pumps and to calculate their performances; the calculation of the PID parameters, applying the Ziegler-Nichols closed-loop method, to be inserted in the control system of the laboratory to allow the complete automatic and remote control of the plant; the development of a first experimental campaign, with a series of repeated tests, at different working points, to verify the correct operation of the test rig and to have the first values of the performances. For the experimental data analysis, a more consistent procedure from a statistical point of view has been adopted instead of the classics procedures of the laboratory: for every tests, at first a steady state is extrapolated, then the charts of the autocorrelation and the residuals distribution are studied and, at the end, all the steady states are merged together and treated with the unweighted batch means method, in order to build Shewart control charts to establish the effective stationarity of the observed process and validate the results. The results show that in the case at 35 °C is not possible to observe a stationary process and therefore give the performances; on the other side, in the case at 45 °C, the process’ stationarity is observed and the performances calculations return lower values than the ones given by the manufacturer [1], in particular the electrical consumption is equal to 1.69 kW (13% more), the thermal power produced is equal to 5.54 kW (6.1% less) and this means that the COP is equal to 2.891 (17.4% less).| File | Dimensione | Formato | |
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2020_06_Saldarini.pdf
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https://hdl.handle.net/10589/153933