Combined photovoltaic solar thermal systems (PVT) literature review: Difference between revisions

This page describes selected literature available on PVT

Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems[1]

Abstract: In this work Author(s) present a study of the optoelectronic properties of nanocrystalline GaN (nc-GaN) and amorphous GaON (a‐GaON) grown by ion-assisted deposition. The two classes of film show very distinct photoconductive responses; the nc-GaN has a fast small response while the a‐GaON films have a much larger response which is persistent. To describe the observed intensity, wavelength, and temperature dependence of the photoconductivity in each class of film, Author(s) build a model which takes into account the role of a large density of localized states in the gap. The photoconductivity measurements are supplemented by thermally stimulated conductivity, measurement of the absorption coefficient, and determination of the Fermi level. Using the model to aid our interpretation of this data set, Author(s) are able to characterize the density of states in the gap for the two materials.

A review on photovoltaic/thermal hybrid solar technology[2]

Abstract: A significant amount of research and development work on the photovoltaic/thermal (PVT) technology has been done since the 1970s. Many innovative systems and products have been put forward and their quality evaluated by academics and professionals. A range of theoretical models has been introduced and their appropriateness validated by experimental data. Important design parameters are identified. Collaborations have been underway amongst institutions or countries, helping to sort out the suitable products and systems with the best marketing potential. This article gives a review of the trend of development of the technology, in particular the advancements in recent years and the future work required.

Photovoltaic thermal (PV/T) collectors: A review[3]

Abstract: This paper presents a review of the available literature on PV/T collectors. The review is presented in a thematic way, in order to enable an easier comparison of the findings obtained by various researchers, especially on parameters affecting PV/T performance (electrical and thermal). The review covers the description of flat plate and concentrating, water and air PV/T collector types, analytical and numerical models, simulation and experimental work and qualitative evaluation of thermal/electrical output. The parameters affecting PV/T performance, such as covered versus uncovered PV/T collectors, optimum mass flow rate, absorber plate parameters (i.e. tube spacing, tube diameter, fin thickness), absorber to fluid thermal conductance and configuration design types are extensively discussed. Based on an exergy analysis, it was reported that the coverless PV/T collector produces the largest available total (electrical + thermal) exergy. From the literature review, it is clear that PV/T collectors are very promising devices and further work should be carried out aiming at improving their efficiency and reducing their cost, making them more competitive and thus aid towards global expansion and utilization of this environmentally friendly renewable energy device.

HYDROGENATED AMORPHOUS SILICON PV AS AN ABSORBER COATING FOR PHOTOVOLTAIC THERMAL SYSTEMS

Abstract: Driven by the limitations of solar-optimized roof space and International Energy Association (IEA) Task 35, there is a renewed interest in photovoltaic solar thermal (PVT) hybrid systems. Current PVT systems focus on cooling the solar photovoltaic (PV) cells to improve the electrical performance. This however, causes the thermal component (T) to underperform. An exergetic study was completed comparing a PVT, PV + T and a PV only system in Detroit, Denver and Phoenix. It was found that the PVT system outperformed the PV + T system by 72% for each location and by 8, 8.6 and 9.9% for Detroit, Denver and Phoenix when compared to the PV only system. To further improve the PVT system, using hydrogenated amorphous silicon (a-Si:H) PV as the absorber layer of the solar thermal device was explored. The temperature coefficient and annealing properties of a-Si:H allow the thermal component to run more efficiently, while enabling the a-Si:H i-layers to be thicker resulting in more electricity production. It was found that running i-layer thicker cells (630nm and 840nm) stabilized at higher efficiencies at 90°C (potential PVT operating temperatures) than the thinner cell (420nm) by 2% and 0.5% respectively. In addition, spike annealing, which is a new concept of stagnating a PVT system to allow for the a-Si:H PV to anneal and return it to its original efficiencies was also investigated. It was found that over the lifetime of the system with the spike annealing occurring once a day 10.6% more electricity was produced than a system without stagnation.

High-efficiency a-Si/c-Si heterojunction solar cell

Abstract: An aperture-area conversion efficiency of 20.0% (intrinsic efficiency: 21.0%) has been achieved for a 1.0 cm2 CZ n-type single crystalline silicon (c-Si) solar cell, by using the “HIT (heterojunction with intrinsic thin-layer)” structure on both sides of the cell. This is the world's highest value for a c-Si solar cell in which the junction is fabricated at a low temperature of below 200°C. In this paper, the junction fabrication technologies and features of the HIT structure are reviewed. The stability under light and thermal exposure, and the temperature dependence on performance of a high-efficiency HIT solar cell are also reported.

Hybrid photovoltaic and thermal solar-collector designed for natural circulation of water

Abstract:The electricity conversion-efficiency of a solar cell for commercial application is about 6–15%. More than 85% of the incoming solar energy is either reflected or absorbed as heat energy. Consequently, the working temperature of the solar cells increases considerably after prolonged operations and the cell’s efficiency drops significantly. The hybrid photovoltaic and thermal (PVT) collector technology using water as the coolant has been seen as a solution for improving the energy performance. Through good thermal-contact between the thermal absorber and the PV module, both the electrical efficiency and the thermal efficiency can be raised. Fin performance of the heat exchanger is one crucial factor in achieving a high overall energy yield. In this paper, the design developments of the PVT collectors are briefly reviewed. Our observation is that very few studies have been done on the PVT system adopting a flat-box absorber design. Accordingly, an aluminum-alloy flat-box type hybrid solar collector functioned as a thermosyphon system was constructed. While the system efficiencies did vary with the operating conditions, the test results indicated that the daily thermal efficiency could reach around 40% when the initial water-temperature in the system is the same as the daily mean ambient temperature.

Design, fabrication and performance evaluation of a hybrid photovoltaic thermal (PVT) double slope active solar still

Abstract:A modified photovoltaic thermal (PVT) double slope active solar still was designed and fabricated for remote locations. The system has been installed at the campus of KIET, Ghaziabad (India) and its performance has been experimentally evaluated under field conditions in natural and forced circulation mode (series and parallel). Photovoltaic operated DC water pump has been used between solar still and photovoltaic (PV) integrated flat plate collector to re-circulate the water through the collectors and transfer it to the solar still. The production rate has been accelerated to 1.4 times than the single slope hybrid (PVT) active solar still and obtained highest (7.54 kg/day) for the parallel configuration in forced mode in the month of October, 2010. The daily average energy efficiency of the solar still is obtained as 17.4%. Comparative results have been predicted on annual basis with the single slope hybrid (PVT) active solar still accounting 250, 275 and 300 clear days in a year. We have found that energy payback time is significantly reduced by almost 30% in present design with less capital investment.

References