Christian Schuss

Measurement and verification of photovoltaic (PV) simulation models

In this paper we present strategies that can potentially improve the accuracy of photovoltaic (PV) simulation models. Generally, output performance levels vary in similar types of photovoltaics. We have categorised different model parameters and highlighted their potential impacts because of the tolerance limits from PV manufacturers. We have focused on the fill factor (FF) to express the characteristics of photovoltaics. Additionally, we have applied our considerations on maximum power tracking (MPPT) techniques such as voltage-based MPPT (VMPPT) and current-based MPPT (CMPPT). Our research suggests the verification of a large sample range of similar photovoltaics for the improvement of PV simulation models.

Use of mobile phones as microcontrollers for control applications such as maximum power point tracking (MPPT)

In this paper we propose the use of conventional mobile phones for a control application, which is usually carried out by microcontrollers. Different extension opportunities of mobile phones, which offer the opportunity to perform control capabilities in an easy way, are discussed. Hence, the microcontroller structure can be left out, as is normally needed. Mobile phones can manage then different power sources by themselves to quickly gain recharge power, which is important due to increased power consumption of these devices. The research is carried out on an experimental phone with a Symbian operating system (OS), and as an example for a control application, maximum power point tracking (MPPT) for photovoltaic (PV) cells is presented. The performance is compared with that of conventional available solar chargers.

Design specifications and guidelines for efficient solar chargers of mobile phones

This paper discusses design requirements to efficiently gather solar energy for mobile phones. It examines current system structures such as conventional solar chargers with an aim to highlight evident weaknesses in existing system structures. Based on the analysis, the paper presents measurement results that indicate that prevailing strategies are not sophisticated enough to meet smartphone users expectations. It is important to note that the recharging time and the quantity of energy required for operational smartphones are critical. We propose design specifications that make solar changers competitive in terms of expenses when compared with universal serial bus (USB) chargers.

Photovoltaic (PV) energy as recharge source for portable devices such as mobile phones

This paper presents opportunities to recharge portable devices, in particular mobile phones, with photovoltaic (PV) energy. Conventional available PV chargers suffer from the disadvantage of long charging times, which are unacceptable for the users of these types of electronics. We review approaches to overcome this drawback and discuss possibilities to shorten the recharging time. We present efficient system configurations, which help that PV energy becomes part of our daily life.

A monitoring system for the use of solar energy in electric and hybrid electric vehicles

In this paper we propose the use of a monitoring system to enhance the degree of efficiency of photovoltaics. We discuss electric vehicles (EVs) as well as hybrid electric vehicles (HEVs) as potential target applications. For these kinds of vehicles we evaluate different connection opportunities for photovoltaics within an on-board power supply. Furthermore, we present a novel connection opportunity to avoid disadvantages from other approaches. We illustrate how our monitoring system responds to changing solar radiation conditions thereby selecting suitable maximum power point tracking (MPPT) strategies. Additionally, we increase the degree of efficiency by disconnecting shadowed photovoltaic (PV) cells from unshadowed PV cells. Moreover, predictions on the energy output of the PV installation are provided as helpful information to the driver.

Solar energy harvesting strategies for portable devices such as mobile phones

In this paper we present strategies to harvest solar energy for mobile phones. Thereby, we discuss system structures, in which mobile phones act as either active or passive devices depending on an available communication between smartphones and their solar chargers. Both design approaches have their advantages and disadvantages, which we will elaborate in more detail in our analysis. At the moment, conventional solar chargers do not meet user expectations and need substantial improvements. We aim to establish design guidelines to make solar chargers competitive with normal chargers, which are plugged into electric sockets. As a result, we achieve appropriate recharging times for smartphones on the one hand and satisfy user requirements on the other hand.

Adaptive photovoltaic cell simulation with maximum power point tracking simulation for accurate energy predictions

This paper presents a modelling tool for photovoltaic (PV) cells, which can build and optimise a simulation model based on measured data, and can plot the I-V (Current-Voltage) and the P-V (Power-Voltage) curve. Furthermore, it allows using solar irradiation and temperature profiles to make cumulative energy simulations during a day, for example, and compare the efficiency of different MPPT algorithms by simulating their behaviour and performance. It was found out that realistic temperature data is very crucial for estimating the effects of MPPT algorithms. The tool is implemented in LabVIEWTM, which makes it easy to combine with actual measurements and offers a suitable graphic user interface (GUI).

Efficient use of solar chargers with the help of ambient light sensors on smartphones

This paper discusses the possibilities to measure the amount of light with the help of portable devices such as mobile phones and tablets. Focus is directed to the accuracy of the ambient light sensor on smartphones in order to obtain the illuminance indoors and the solar radiation level outdoors. In general, information on the ambient conditions is vital to improve the performance of solar chargers. For example, if users are able to allocate beneficial locations to deploy solar chargers inside buildings, up to 100 times more energy can be gathered during the same periodic time. Similarly, under outdoor environmental conditions, solar modules can be aligned better towards the sun to increase the possible amount of output power. We analyse the accuracy of ambient light sensors which are available in todays low-cost and upper-class smartphones. Additionally, we present calibration strategies for ambient light sensors in order to minimise the error between conventional measurement equipment and mobile phones.

Detecting Defects in Photovoltaic Cells and Panels and Evaluating the Impact on Output Performances

This paper investigates the ways to detect defects in photovoltaic (PV) cells and panels. Here, two different methods have been used. First, the output behavior was characterized by measuring the amount of current at different voltage levels to obtain the current-voltage and power-voltage curves. Second, infrared emissions of forward-biased nonilluminated PV cells and panels were measured by the use of synchronized thermography. From these measurements, temperature maps can be derived, which indicate that the temperature within a given PV cell unevenly rises due to the defects in the cell. Uneven temperature distribution indicates defects and reduced output power.

Detecting defects in photovoltaic modules with the help of experimental verification and synchronized thermography

In this paper we investigate defects in photovoltaic modules which cause variations in output performances. Here, we concentrate on two possible ways to verify potential output power levels. Firstly, we characterise the output behaviour by measuring the amount of current at different voltage levels to obtain the I-V (Current-Voltage) and P-V (Power-Voltage) curves. Secondly, we measured the infrared (IR) emissions of photovoltaic modules by the use of synchronized thermography. From those measurements, temperature maps can be derived which indicate that the temperature rises differently in photovoltaic modules due to defects. As a result, we are able to establish quantitative and qualitative verifications of photovoltaic modules.