The stagnation temperatures experienced by glazed photovoltaic-thermal (PV-T) collectors pose a threat to their performance and longevity, in part due to the limited temperature stability of ethylene vinyl acetate (EVA) encapsulants. In order to identify suitable solutions for application in residential solar domestic hot water (SDHW) PV-T systems, a comparative analysis of known overheating prevention and stagnation handling measures was conducted and dynamic simulations were used to support the analysis. While no measure was found to comply with all desirable goals including reliability, implementation and operation costs, integral venting mechanisms were identified as the most promising among the control systems reviewed. Moreover, active collector heat dumping and automatic collector shading led to minimal electrical efficiency increases and decreases, respectively, while purging tank water when the collector overheats was found to be ineffective due to delays in the start of circulation

A solar trigeneration system for off-grid households, based on photovoltaic-thermal (PV/T) collectors, photovoltaic (PV) modules and a heat pump (HP), whose aim is to provide enough electricity, domestic hot water (DHW), heating and cooling power to meet the typical demand of an offgrid single family dwelling, is modeled to predict its performance, enable system sizing and evaluate the impact of different control and management strategies. The system integrates an autonomous photovoltaic system, a solar DHW system and a heating, ventilation and air-conditioning (HVAC) system. Thus, according to local climate data, construction elements, load profiles and storage dynamics, the model computes the system’s net results using a simple supply and demand approach. Additionally, a design space methodology is used to evaluate system performance for different sizes and identify a feasible design region within which reliable and cost-effective system sizing is possible.

Active photovoltaic-thermal (PV-T) systems for solar heating and electricity generation are likely to employ the same differential temperature pump controllers as equivalent non-hybrid solar thermal (ST) systems. However, the typical controller setpoint selection methods for cost-effective and stable pump operation fail to consider the effect on photovoltaic (PV) electricity generation taking place in PV-T systems. Analytical relations for the same goals were derived to anticipate this influence using the steady-state Florschuetz PV-T collector model and compared with equivalent numerical methods relying on an extension of the Perers model designed to encompass PV-T collectors, namely by modelling electricity generation and the associated thermal performance reduction. Both methods indicate the minimum turn-on and turn-off setpoints for cost-effective and stable operation increase and decrease, respectively, relative to those for non-hybrid operation of PV-T systems or equivalent non-hybrid systems, and more so at higher irradiance levels, though the variations are shown not to be significant for a range of PV-T systems represented and can be reasoned to be inflated or of limited practical relevance. In conclusion, the effect of pump operation on electricity generation is not predicted to be a determining factor for differential temperature controller setpoint selection in PV-T systems.