Bernd Eichberger

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.

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.

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.

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.

Guided mutation strategies for multiobjective automotive network architecture

The increasing complexity of electronic functions in cars leads to new challenges in the development of automotive communication networks. A key issue is the mapping of functional software onto hardware nodes, which has a great impact on overall system performance and costs. In this paper we propose two fitness metrics focusing on this mapping process. We further derive guided mutation operators for an application-specific network optimization framework using multiobjective evolutionary algorithms. Our main contribution represents a novel approach to guided evolutionary mutation by interchanging modular operators during execution of the optimization algorithm. We show that our approach outperforms classic random mutation both in terms of convergence behavior and diversity.

Alignment and interconnection of photovoltaics on electric and hybrid electric vehicles

In this paper we discuss the alignment and system structures of photovoltaics on the roof of electric vehicles (EVs) and hybrid electric vehicles (HEVs). We focus on the interconnection of PV cells. In general, the position of photovoltaics on the roof of automobiles is crucial and has a strong impact on the photovoltaic (PV) output behaviour, in particular their output power level. We present strategies which allow the adaption of system structures according to changes in environmental conditions. As a result, we increase output performance levels by changing the interconnection of photovoltaics dynamically.

Impact of sampling interval on the accuracy of estimating the amount of solar energy

This paper presents an accurate, low-cost measurement setup for the collection of solar radiation and temperature levels. Environmental data is required for photovoltaics to investigate their performances in terms of output power. In this investigation, each sensor was sampled 30 times per second and thereby, we achieved a resolution which was much higher than comparable work in the available literature. Furthermore, we present the various influences that can affect the computation of the ideal output power of photovoltaics when we move from a high sampling rate towards a low sampling rate. For predominantly cloudy days, our research indicates that monitoring the environment at least every ten seconds is advisable for attaining a suitable accuracy.

Estimating the impact of defects in photovoltaic cells and panels

This paper investigates defects in photovoltaic cells and panels which cause notable losses in output performances. Here, the focus lies on the impact of hairline cracks which result in a remarkable drop of the available output current and, thus, the available output power. Firstly, samples were characterised with the help of synchronized thermography (ST) in order to localise and analyse the defects. Secondly, samples were measured with the help of electrical verification to obtain the characteristic I-V (Current-Voltage) curve. Finally, the geometric area of PV cells was calculated which corresponds to the effective area for energy production due to the presence of a defect. Results show the correlation between the available power of PV cells with temperature variations in IR-emissions. Proposed methods are capable of detecting defects in PV cells and quantise the impact on output performances.