The world population and consequently the global need for food continue to grow. At the same time, areas will be used to generate clean electricity to cope with climate change and global warming. The combination of crop production and solar photovoltaics in the form of “agrivoltaic technology” offers advantages for both sides that provide an adequate, resource-efficient solution to the persistent problem of competition for arable lands. The implementation of agrivoltaic systems has been exponentially increased in recent years and reached the global installed capacity of 2.8 GW in 2020 from the initial capacity of 5 MW in 2012. The agrivoltaic systems installed worldwide mostly employ conventional opaque photovoltaic (PV) modules, causing a change in the microclimate under the panels that become critical when shading ratios are high. Semi-transparent PV (STPV) modules have been recently employed to mitigate this issue which is profoundly studied in this research by considering the use of semi-transparent technologies based on crystalline silicon (c-Si), thin-film photovoltaics, organic PVs (OPVs), dye-sensitized solar cells (DSSCs), concentrating PVs (CPVs), and luminescent solar concentrators (LSCs) in open (arable farming lands) and closed (cultivation greenhouses) agrivoltaic systems. The results indicated that c-Si STPV modules have the highest share of employment in agrivoltaic systems due to their extreme benefits of low costs, high stability, and high efficiency in comparison with other technologies, while in contrast, the use of thin-film STPV modules have been rarely reported in the literature. Additionally, STPV modules using OPVs and DSSCs offer the capability to achieve wavelength-selective transparency, causing the photosynthetic active radiation to pass through while the remained spectrum is utilized to generate electricity. Other potential solutions come from CPVs and LSCs, in which, diffuse light is available for the growth of cultivated plants, while direct concentrated sunlight can generate electricity. Although STPV modules are proven as a feasible solution for use in agrivoltaic systems, still more developments are required in terms of the modules’ efficiency enhancement and costs reduction, while more detailed research is required to observe the response of cultivated plants to make this technology a viable sustainable solution in the future. 

Progress and challenges of crop production and electricity generation in agrivoltaic systems using semi-transparent photovoltaic technology

Axicon is a versatile optical element for forming a zero-order Bessel beam, including high-power laser radiation schemes. Nevertheless, it has drawbacks such as the produced beam’s parameters being dependent on a particular element, the output beam’s intensity distribution being dependent on the quality of element manufacturing, and uneven axial intensity distribution. To address these issues, extensive research has been undertaken to develop nondiffracting beams using a variety of advanced techniques. We looked at four different and special approaches for creating nondiffracting beams in this article. Diffractive axicons, meta-axicons-flat optics, spatial light modulators, and photonic integrated circuit-based axicons are among these approaches. Lately, there has been noteworthy curiosity in reducing the thickness and weight of axicons by exploiting diffraction. Meta-axicons, which are ultrathin flat optical elements made up of metasurfaces built up of arrays of subwavelength optical antennas, are one way to address such needs. In addition, when compared to their traditional refractive and diffractive equivalents, meta-axicons have a number of distinguishing advantages, including aberration correction, active tunability, and semi-transparency. This paper is not intended to be a critique of any method. We have outlined the most recent advancements in this field and let readers determine which approach best meets their needs based on the ease of fabrication and utilization. Moreover, one section is devoted to applications of axicons utilized as sensors of optical properties of devices and elements as well as singular beams states and wavefront features.

Modern Types of Axicons: New Functions and Applications.

The efficiency of the photovoltaic (PV) module is drastically decreased when integrated with building material. This efficiency decrease is mainly caused due to the temperature rise of the PV module. The temperature rise is responsible for the overall decrease in voltage and power production. Only a small fraction of the solar radiation that falls on the PV module is utilized for electricity production and the rest generates excess heat responsible for the temperature rise of the PV module. The integration of the PV panel on the roof also prevents air circulation results in the accumulation of heat. There are several techniques to manage the temperature rise viz. air cooling, water cooling, thermoelectric cooling, and phase change materials (PCMs). This paper discusses the various cooling technologies that can regulate PV temperature and augment power production. The result showed that passive cooling that relies on convection is the easiest and simplest approach and does not consume additional power. Active water cooling is effective to a greater extent but there is always a requirement of cold water which may offset the benefit of cooling. The temperature up to 18 °C can be reduced and efficiency between 1 and 18% can be enhanced by PV/thermoelectric module (TEM). The PV temperature can be lowered by about 35.6 °C by using a PCM system with the PV panel. The addition of nanoparticles has a positive influence on lowering the temperature of the PV module. The temperature can be lowered up to 16 °C by using nanoparticles in the water system with PCM. The electrical efficiency can be improved by 8–10%. The integration of PV/T with PCM can increase the heat availability time by 100%. The addition of such kind of heat extraction system increases the electrical power production and better thermal efficiency is also observed. The combined efficiency of 70–80% has been achieved in many cases. For the PV/ T system, the economic payback is obtained between 20 and 25 years and the energy payback is between 15 and 20 years.

Thermal regulation of photovoltaic system for enhanced power production: A review

Axicon is an interesting optical element for its optical properties. This paper presents an approach to dynamically generated tunable axicons with a spatial light modulator (SLM). 256-level phase computer-generated holograms (CGHs) were loaded into the SLM to simulate the positive and negative axicons. The intensity distributions of beams passing through these axicons were analyzed with the principle of blazed grating and Fresnel diffraction; and the diffraction patterns were obtained theoretically in terms of zero-order Bessel beams and annular hollow beams, corresponding to the positive and negative axicons, respectively. Experimental results verified that the diffraction patterns have the same distribution as the real axicon. The types of the axicon and the axicon’s parameters can be easily altered through changing the CGHs.

Tunable Axicons Generated by Spatial Light Modulator with High-Level Phase Computer-Generated Holograms

A phase differential heterodyne interferometer for simultaneous measurement of straightness error and displacement

Measurement of four-degree-of-freedom error motions based on non-diffracting beam

Photovoltaic (PV) systems are playing a more and more important role as a renewable energy supplier. However, their large-scale applications is still limited by low conversion efficiency and high land-use requirement, especially for those areas where land and solar energy resources are more important for agriculture. In this paper, we suggest a dish-type high-concentration photovoltaic system, with which the competition between sunlight for crops' growth and PV application is solved by beam-splitting techniques. A purposely-designed beam filter acts as a solar spectrum splitter, and the most effective bands of solar spectrum for plant growth are transmitted down to plants while the other parts are all directed to the solar cell receiver. The spectral and spatial distribution of radiant intensity is investigated by ray tracing method, and the quantitative evaluation of the beam splitting effect on crop growth and PV power generation is provided in detail. The results show that, on one hand, the proposed sy...

A dish-type high-concentration photovoltaic system with spectral beam-splitting for crop growth

The intensity distribution of diffraction field of two non-diffracting beams which interfere in a long distance is derived. Non-diffracting beam is generated by an axicon, which is then split into two coherent beams by a beam splitting prism, one of the two beams is regarded as reference beam, which meet the other one through reflector and another beam splitting prism after a long distance. The distribution of interference field is the coherent superposition of each diffraction field. Results show that the locus of interference fringes can be generally assumed hyperbola, the shape of which is affected by interference instance. When the two beams remain parallel, the diffraction pattern is analyzed to be hyperbolic moire fringe,in a case where there is an oblique angle between two beams, the trend of hyperbolic moire fringe change with the interference fringe trend without axicon. Experimental results are compared with theoretical analysis results. Good agreements between them is obtained.

Yiyuan Shang

Papers

Measurement of four-degree-of-freedom error motions based on non-diffracting beam

A dish-type high-concentration photovoltaic system with spectral beam-splitting for crop growth

Theoretical analyses of non-diffracting beams interference in a long distance