• Energy Research

Abstract The intensive exploitation of natural resources, expansion of human population and degradation of natural and semi-natural habitats, caused among others by agriculture, forestry and urbanisation, enforce special care for the natural resources, especially the disappearing types of vegetation that are refugees of biodiversity. One of the most threatened plant communities are grasslands (pastures and meadows), which has suffered the most in recent decades due to the intensification of agriculture and the transformation of land use. The purpose of this paper is to propose a hybrid approach to clean energy production on photovoltaic (PV) farms, taking into account the needs of grassland conservation and restoration. Nine sets of sciophilous species are proposed, including grasslands rich of pollinator benefits, grasslands with low pollen production to maintain high electrical efficiency of panels, and rich, standard meadows in wet (Molinion, Calthion, Alopecurion, Cnidion), fresh (Arrhenatherion) and dry (Cirsio-Brachypodion) types. The combination of clean energy and grassland conservation has been called ecovoltaics (EV) because it combines the production of renewable electricity with care for the diversity of valuable grassland ecosystems. The research will continue on an experimental ecovoltaic farm with innovative technical solutions to effectively maintain the desired meadow species composition. The purpose of this study was to analyse and select plant species that could be introduced into areas where PV cells are installed under climatic conditions in southern Poland. Using databases, environmental and ecological factors were taken into account. As a result of the study, a list of 206 species was selected that could be introduced to areas where they will coexist with PV panels, taking into account the effect of shading. The developed selection of these plant species provides a starting point for future work by botanists and engineers seeking to increase the biodiversity of sites where PV panels will be placed.

Abstract The presented article relates to aspects of PV module testing using natural sunlight in outdoor conditions. It is a continuation of the article Part III: parameters of atmospheric transparency - determining and correlations. This article discusses the practical application of the indexes: atmosphere purity - k Tm , diffused component content - k s/o , beam clear sky index - K b - in testing various modules in outdoor conditions. Their influence on the conversion of modules made from various absorbers and various technologies is demonstrated. Their practical application in module testing in outdoor conditions is described and it - has been demonstrated that the results of the analyses carried out using the indexes conform to the results obtained using spectral parameters of solar radiation (i.e. APE and UF). These are the measurements that require the use of very expensive equipment.

Due to rapid urbanization, the number of wastewater treatment plants (WWTP) has increased, and so has the associated waste generated by them. Sustainable management of this waste can lead to the creation of energy-rich biogas via fermentation processes. This review presents recent advances in the anaerobic digestion processes that have led to greater biogas production. Disintegration techniques for enhancing the fermentation of waste activated sludge can be apportioned into biological, physical and chemical means, which are included in this review; they were mainly compared and contrasted in terms of the ensuing biogas yield. It was found that ultrasonic- and microwave-assisted disintegration provides the highest biogas yield (>500%) although they tend to be the most energy demanding processes (>10,000 kJ kg−1 total solids).

Sorption of copper ions by the alga Spirogyra sp. was investigated to determine the influence of experimental conditions and the methods of sample preparation on the process. The experiments were carried out both under the static and the dynamic conditions. Kinetics and equilibrium parameters of the sorption were evaluated. In addition, the influence was studied of the algae preparation methods on the conductivity of demineralized water in which the algae samples were immersed. The static experiments showed that the sorption of Cu(2+) ions reached equilibrium in about 30 min, with approximately 90% of the ions adsorbed in the initial 15 min. The sorption capacity determined from the Langmuir isotherms appeared highly uncertain (SD=±0.027 mg/g dry mass or ±11%, for the live algae). Under static conditions, the slopes of the Langmuir isotherms depended on the ratio of the alga mass to the volume of solution. The conductometric measurements were proven to be a simple and fast way to evaluate the quality of algae used for the experiments.

In this work some results of theoretical analysis on the selection of optimum band gap semiconductor absorbers for application in either single or multijunction (up to five junctions) solar cells are presented. For calculations days have been taken characterized by various insolation and ambient temperature conditions defined in the draft of the IEC 61836 standard (Performance testing and energy rating of terrestrial photovoltaic modules) as a proposal of representative set of typical outdoor conditions that may influence performance of photovoltaic devices. Besides various irradiance and ambient temperature ranges, these days additionally differ significantly regarding spectral distribution of solar radiation incident onto horizontal surface. Taking these spectra into account optimum energy band gaps and maximum achievable efficiencies of single and multijunction solar cells made have been estimated. More detailed results of analysis performed for double junction cell are presented to show the effect of deviations in band gap values on the cell efficiency.

The article presents the influence of changes in the solar radiation spectrum distribution on the properties of various photovoltaic modules, with particular emphasis on the scattered component. We compared the relative efficiency of the photovoltaic modules based on various semiconductor absorbers during bright and sunny, and cloudy summer days. Additionally, we presented the impact of the module tilt angle on the magnitude of the surface incident scattered component and on the efficiency of the module. The solar spectra for various weather conditions were estimated using specialised computer programmes,such as SolarSpectrum or SMARTS2, and we present here the validation results for the former. The obtained results confirm the published experimental data and the conclusions drawn show the applicability of the tested modules with various absorbers for the specific photovoltaic systems. The theoretical analysis of the a-Si structures, both single-, as well as multi-junction shows better performance of these structures at low-irradiance conditions (in comparison with e.g., c-Si, CIS structures), during days characterised by a spectral distribution common for cloudy days with high air water vapour content. This type of device should show unaltered efficiency both at mid-day, as well as during the morning and late afternoon.