Photovoltaic Thermal Heat Research Articles

The detection and correction of various faulty sensors in a photovoltaic thermal heat pump system

Accurate and reliable measurements collected from various physical sensors are of great importance to improve the energy utilization efficiency of solar energy systems. Sensor errors have various significant negative impacts on the automatic control and optimized operation. The current study used the virtual in-situ calibration (VIC) instead of traditional methods to spot possible systematic and random errors of temperature, pressure and mass flowrate sensors in a photovoltaic-thermal heat pump (PVT-HP) system. Seven working conditions were designed to check the robustness and accuracy of the proposed VIC technology. The effects of systematic and random errors on the sensor calibration process and performance estimation of a PVT-HP system were investigated. It’s shown that after calibration the systematic errors of all kinds of sensors were less than 2% and the random errors were also reduced by as much as 74%, significantly reducing the possibility of abnormal data and enhancing the reliability of sensor measurements. The VIC method is very effective to guarantee the thermal performance of PVT-HP system.

Performance assessment of a hybrid photovoltaic-thermal and heat pump system for solar heating and electricity

This work investigates a solar combined heat and power systems based on hybrid photovoltaic-thermal heat pump systems for the simultaneous provision of space heating and electricity to residential homes. The analysed system connects a photovoltaic-thermal (PVT) panel, through a PVT water tank, to a heat pump. The study is based on quasi-steady state heat transfer and thermodynamic analysis that takes incremental time steps to solve for the fluids temperature changes from the heat pump and the solar PVT panels. The effects of solar irradiance, size of the water tank and the water flow rate in the PVT pipes (laminar and turbulent) on the performance of the system are analysed. Particular focus is made towards the efficiency (electrical and thermal) of the PVT and the COP of the heat pump. Results show that the minimum COP of the heat pump is 4.2, showing the high performance of the proposed hybrid system. Increasing the water flowrate through the PVT panel from 3 L/min (laminar) to 17 L/min (turbulent) increases the PVT’s total efficiency (electrical + thermal) from 61% to 64.5%. Increasing the size of the PVT water tank from 1 L to 100 L, increases the total efficiency of the PVT panel by 6.5%.

Refrigeration characteristics of a hybrid heat dissipation photovoltaic-thermal heat pump under various ambient conditions on summer night

This paper presents a radiative/convective hybrid heat dissipation photovoltaic-thermal heat pump (HHD-PVT-HP) refrigeration system based on the traditional PVT solar heat pump, which can be used to meet the cooling demand of buildings. PVT modules are used for the system condenser. The PVT modules emit heat to the ambient surroundings (hybrid heat dissipation) mainly by two ways: radiation to the night sky and convection with the surrounding air. An experimental study and parametric analysis of the HHD-PVT-HP system is conducted. The experimental results indicate that the HHD-PVT-HP system is able to stably refrigerate on summer night, with an average COPref value ranging from 1.8 to 2.1. Moreover, the heat dissipation performance of the PVT modules is good, with an average hybrid heat dissipation flux of ∼420 W/m2. To predict the operation characteristics of the HHD-PVT-HP under various ambient conditions, a system simulation model is established and validated with experimental data. The simulation results show that changes in the ambient air temperature and wind velocity have obvious effects on the heat dissipation characteristics of the PVT modules and system refrigeration performance. However, when the outdoor wind velocity is greater than 1 m/s, its influence is obviously lessened. Additionally, the relative humidity of the ambient air has little effect on the refrigeration capacity and COPref of the HHD-PVT-HP system.

Unglazed PVT collectors as additional heat source in heat pump systems with borehole heat exchanger

An unglazed photovoltaic-thermal (PVT) collector provides a double benefit in a heat pump system compared to a conventional heat pump system with PV and borehole heat exchanger. First, the PV cells in the PVT collector are cooled, leading to lower cell temperatures and a higher PV efficiency. Second, the PVT heat raises the temperature level of the heat pump and the borehole heat exchanger and consequently leads to a higher heat pump system performance. In this context a system was measured with a 39 m2 unglazed PVT collector field. The impact of the solar heat to the heat pump is determined by TRNSYS simulations using energetic weighted temperatures for validation and to quantify the impact of the solar heat. The investigated system revealed a temperature increase of 3K which equals 9% lower electricity consumption. The yearly additional PV yield was determined to 4% by reference measurement of uncooled conventional PV panels. Additionally, system simulations in TRNSYS are presented.