The objectives of the paper were to show that the evaporation intensity of water can be increased by the application of appropriate textile materials. The purpose was to determine the dependence of the evaporation intensity on the textile characteristics and the influence weather conditions on the evaporation intensity of different textiles. Five different textile strips of different widths and of single- and multi-layer were tested in definite experimental pots under open air conditions. The results of the experiments showed the total evaporation surface of the textiles depended on the texture material and the capillary volume of the textiles and the capillary volume had a limit at approximately Vc = 1000–1200 cm3/m2. Another important result was that the relative air humidity is a main factor of the weather conditions that has principal influence on the evaporation intensity. However, the other parameters — such as temperature, solar radiation and wind speed — have only a secondary effect on the evaporation intensity of textiles.
Clod crushing is a principal problem with soils of high clay content.
Therefore, there is a need for determining the conditions for clod breaking and
clod crushing. The objective of the work was to develop a special purpose tool
for single clod breaking both by rigid support of the clod and by a single clod
supported by soil and to develop a machine for clod crushing. Furthermore, the
purpose was to determine the relationship between the specific energy
requirement for clod crushing in the function of soil plasticity and the soil
moisture content by the means of the developed tool and machine. The main
result of the experiments is summarized in a 3D diagram where the specific
energy requirement for soil clod crushing is given in the function of the
moisture content and the plasticity index for different clay soils.
Water pumping for irrigation has a relatively high energy demand, depending on the applied irrigation method. At the same time, there is a considerable energy from the sun during the irrigation period. The solar PV (photovoltaic) technology may be suitable to ensure electric energy for pumping in many cases in agriculture, where the electric network is not available or reduction of the energy costs is wanted. There are some pilot plants for water pumping on the base of solar energy in the world and the spreading of these solar technologies is predictable. The solar energy based pumping process can be approached both in theoretical and experimental ways. In this paper, both the theoretical questions of the solar based pumping process and the experimental results of a model testing pump station powered by PV panels are shown.
Authors:István Patay, Miklós Erdélyi, and László Gulyás
A relatively new trend is the development of concentrator-type solar collectors and cells for the use in micro-concentrators. The geometry of these concentrators is simple, the reflexion surfaces or mirrors are usually flat-plate surfaces. The relations of radiation in the inner spaces of these collectors are complicated. The OSLO optical edition software can be used to study and simulate the light paths in the concentrator elements and resonators, using the laws of geometrical optics. Based on the results of study and simulation, a pilot collector was built for energetic testing. In the applied arrangement, the absorber surface was the heated tube itself and fitted exactly to the inlet concentration surfaces. By this way, the relation of the absorber surface and collecting surface was reduced to 0.25. Since the radiation losses decreased, the efficiency of the pilot collector was relatively high even at high outlet temperature conditions (50% at 50 °C outlet temperature and Δ
= 18 °C). The optical concentration of solar radiation energy is a possible way to increase the liquid heat transporter collector efficiency and the outlet temperature. Importance of air solar collectors is lower, but their application in some agricultural post-harvest processes (drying, desiccating) may be useful and profitable. A flat-plate-plate solar air collector was built and tested, with special absorber geometry and material. The results of tests are also shown in this study. The proved daily ΔT-asymmetry at both of pilot collectors is an important result for the practice. Practically it means that the afternoon hours are more favorable for the energy production than the morning hours. Since this effect probably exists in all types of solar collectors, the practice of horizontal direction of collectors needs modifying.