Empirical versus Optimal Control of Flow in Solar Domestic Hot Water Systems

AbstractA closed-loop system based on a detailed flat-plate collector model and a water storage tank operating in a fully mixed regime has been considered. The system operates in Timisoara, Romania, under a southeastern European temperate continental climate. Four empirical strategies for flow-rate control have been compared with an optimal control strategy, used as an ideal reference. Days for all seasons and all cloudiness classes have been considered. Also, days with more-stable or less-stable radiative regimes have been used. Under the specific climatic conditions, the most appropriate empirical control strategy uses the momentary values of solar irradiance as input data. It provides good results during all seasons, independent of the class of relative sunshine and the stability of the radiative regime. An empirical strategy based on the constant-mass flow rate has been also identified as a good alternative. This strategy might be easier to implement since it involves a single-speed pump. The recommen...

[1]  W. Beckman,et al.  Solar energy thermal processes , 1974 .

[2]  Le Minh Nhut,et al.  A study on automatic optimal operation of a pump for solar domestic hot water system , 2013 .

[3]  D. E. Prapas,et al.  Large DHW solar systems with distributed storage tanks , 1995 .

[4]  Robert Fischl,et al.  Optimal control of a solar collector loop using a distributed-lumped model , 1981, Autom..

[5]  F. de Winter,et al.  Investigation of methods to transfer heat from solar liquid-heating collectors to heat storage tanks. Final report , 1978 .

[6]  Consumers' influence on the thermal performance of small SDHW systems: Theoretical investigations , 2002 .

[7]  Theodore F. Smith,et al.  Development of proportional-sum-derivative control methodology , 1996 .

[8]  Viorel Badescu,et al.  New approach to measure the stability of the solar radiative regime , 2011 .

[9]  S. Kalogirou.  Solar Energy Engineering: Processes and Systems , 2009 .

[10]  Viorel Badescu,et al.  A new kind of cloudy sky model to compute instantaneous values of diffuse and global solar irradiance , 2002 .

[11]  Simon Furbo,et al.  Optimum solar collector fluid flow rates , 1996 .

[12]  Viorel Badescu.  Optimal control of flow in solar collector systems with fully mixed water storage tanks , 2008 .

[13]  Adrian Bejan,et al.  Optimum flowrate history for cooldown and energy storage processes , 1982 .

[14]  K.G.T. Hollands,et al.  Optimum flow rates in solar water heating systems with a counterflow exchanger , 1992 .

[15]  Tomas Persson,et al.  Increasing solar gains by using hot water to heat dishwashers and washing machines , 2007 .

[16]  Adrian Bejan.  Extraction of exergy from solar collectors under time-varying conditions , 1982 .

[17]  K.G.T. Hollands,et al.  Plume entrainment effects in solar domestic hot water systems employing variable-flow-rate control strategies , 1992 .

[18]  Optimal control of a multicomponent solar collector system , 1985 .

[19]  Francis de Winter.  Comments on optimum flow rates in solar water heating systems with a counterflow exchanger , 1992 .

[20]  M. Kovarik,et al.  Optimal control of flow in low temperature solar heat collector , 1976 .

[21]  William A. Beckman,et al.  Control problems in solar domestic hot water systems , 1994 .