Recently, the demand for small grid-connected photovoltaic (PV) systems has been rapidly increasing; this is due to the reduction in the costs of grid-connected storage systems as compared to those of the stand-alone ones. Notably, the performance of the solar tracking system is not only depending on the types but also the region that they are set up and used. To understand how solar tracking systems work globally, we need to know their performance in each country and even the different parts of a country. In this study, two grid-connected PV systems with 250 W solar modules were used to investigate the efficient improvement of a single-axis sun tracking system in Central Vietnam. First, a mechanical tracking device with a linear actuator and a controller was designed and then its performance was comprehensively investigated with a grid-connected PV system. In addition to evaluating the energy gain by the tracking system, this study also considered the energy consumption of the linear actuator with its controller and a small grid-connected PV system; this has generally been omitted in previous works. Experimental results indicate that the total energy consumption of the tracking system was approximately 2–8% of the energy generated by the grid-connected PV system. The maximum overall energy generation was confirmed to have increased by up to 30.3% on a sunny day upon using the proposed tracking system; further, the net energy gain by using the sun tracker was ascertained to be 15.2% in average weather conditions. Based on the success of this work, we will keep experimenting with other parts of Vietnam. Also, we will collaborate with colleagues in other countries to create a guideline for understanding and using the solar tracker regionally and globally.

In the present work, we consider systematically the electronic and optical properties of two-dimensional monolayer germanium monosulfide (GeS) under uniaxial strains along armchair (AC-strain) and zigzag (ZZ-strain) directions. Our calculations show that, at the equilibrium state, the monolayer GeS is a semiconductor with an indirect band gap of 1.82 eV. While monolayer GeS is still an indirect band gap semiconductor under ZZ-strain, an indirect–direct energy gap transition can be found in the monolayer GeS when the AC-strain is applied. The optical spectra of the monolayer GeS have strong anisotropy in the investigated energy range from 0 eV to 8 eV. Based on optical properties, we believe that the monolayer GeS is a potential candidate for applications in energy conversion and optoelectronic technologies.

This paper presents modeling and experimental studies on water spray coolers for commercial photovoltaic modules. This paper has compared the energy yield of four photovoltaic commercial modules that were installed with a fixed tilt angle being equal to the local latitude in central Vietnam, including one photovoltaic module using a water spray cooler and three photovoltaic modules without cooling. Experimental results on sunny days have been shown that the energy yield difference between four PV modules under the same working condition is lower than 1%. In addition, on sunny days when the set working temperature of the water spray cooler is 45 °C, the average improvement efficiency of a photovoltaic module using a water spray cooler compared to three reference photovoltaic modules is 2.64%, 3.83%, and 6.18%, for an average of 4.22%. A simple thermal–electrical model of a photovoltaic module with a water spray cooler has been developed and tested. The normalized root mean square error between simulated and measured results of photovoltaic module power output on a sunny day without cooling and with water spray cooler reached 6.5% and 8.5%, respectively. The obtained results are also demonstrated that the reasonableness of the simple thermal–electrical model of the photovoltaic module with water spray cooler and the feasibility of a cooling system is improved to increase the efficiency of the photovoltaic module. In addition, they can be considered as a basis for new experimental models in the future.

Recently, the use of small-scale grid-connected photovoltaic (GCPV) systems for households has been growing in Vietnam. The installation of a rooftop GCPV system provides many benefits to households, such as lowering monthly electricity bills, reducing absorbed heat of the building, and creating additional income by penetrating electric power to the grid. However, the technical issues of the payback period is complicated and requires a lot of considerations. The main goal of this study is to develop a computational model and investigate the effect of electrical energy consumption on the payback period of rooftop GCPV systems. A case study is used in this study to create a model of a rooftop GCPV system for households in north-central Vietnam under feed-in tariff (FiT) schemes. The results show that the investment rate and electrical energy consumption of the installed household have a strong influence on the payback period of the GCPV system. In the case of the lowest investment rate of 666.4 USD/kWp, the fastest payback period is 43 months for households consuming all of the generating energy of the GCPV system, and the longest payback period is 131 months for households that do not use electricity, implying that all of the generating energy of the GCPV system is connected and sold to the distribution grid. The research findings will actively assist in calculating the installed capacity suitable for households in order to have the most suitable payback period while also assisting policymakers in the future in setting a reasonable rate of feed-in tariff for rooftop GCPV systems

The paper presents the concepts of solar tracking controllers for photovoltaic panels based on the fuzzy control law. The controller uses a microcontroller and algorithm based on fuzzy logic. In this study, a triangle type is seen to be appropriate as a membership function, so that the microcontroller can solve problems faster. The fuzzy logic controller uses a MISO fuzzy system with two inputs of the ADC signal from the light sensor and one output of the PWM duty cycle rate. Membership functions and fuzzy control systems are created via a MATLAB program, thereby checking the correctness of fuzzy logic controllers.