Maciej Neugebauer

The Influence of Weather Conditions and Operating Parameters on the Efficiency of Solar Power Collectors Based on Empirical Evidence

The influence of solar irradiance, ambient temperature and buffer tank temperature on the efficiency of solar collectors was evaluated in the climatic conditions of north-eastern Poland (climatic zone IV) characterized by relatively low irradiance (annual average of 900 kWh/m2). Two types of solar power collectors (flat-plate and evacuated tube collectors) were compared in terms of energy gains, collector efficiency and glycol temperature between May and September 2016. The collectors were mounted on the roof of a building on the campus of the University of Warmia and Mazury in Olsztyn. The roof had a pitch of 45°, the collectors had a tilt angle of 30°, and they faced west of true south. Measurements were performed separately for the analyzed solar collector systems operating simultaneously in identical weather conditions. The combined absorber surface was 4.64 m2 in flat-plate collectors and 3.23 m2 in the evacuated tube collector. Both systems were connected to a water buffer tank. Empirical data were recorded with a controller and were processed and stored in a computer. The factors responsible for differences in the efficiency of the examined collectors are discussed in the paper.

A Fuzzy Model of the Composting Process with Simultaneous Heat Recovery and Aeration Rate Control

Composting is an effective method of managing biomass waste from agricultural crops and food processing. This exothermic reaction produces high-quality humus. Heat generated during composting can be evacuated from the compost pile and used effectively for other purposes. Effective methods are needed to control prism aeration and the evacuation of heat from the compost prism to maximize heat gain without compromising the composting process. A preliminary examination of fuzzy logic systems revealed that the terms of input and output variables and sharpening methods have to be adapted to specific compost materials. This approach also delivers immediate results without the need for lengthy research. The composting process lasts several weeks, therefore, models which illustrate the responses of control systems save time and support the selection of the optimal solutions for changing the aeration rate and heat consumption in feedstock. Fuzzy models of the control system developed in the LabVIEW programs are effective tools which can be directly implemented in a programmable logic controller (PLC).

The use of biological waste as a source of low-temperature heat for hotbeds in spring in north-eastern Poland

This article proposes a method for using biological waste, including kitchen waste and garden waste, as a substrate for hotbeds. Hotbeds have been long used in home gardens, but most of them are supplied with animal manure, usually horse manure. In this study, the temperature of ambient air, soil temperature and temperature distribution in a hotbed and a cold frame were measured with a thermographic camera. The measurements were performed in three experimental treatments - one hotbed, one cold frame and in the garden. Each treatment was sown with radishes (Raphanus sativus). The experiment began on 7 April, and temperature was measured until the temperature of garden soil reached the temperature inside the hotbed and the cold frame. After the experiment, the hotbed was left in place until the end of August to complete the composting process and grow other plants. The amount of heat generated inside the hotbed during the experiment was calculated, and the thermal efficiency of the hotbed was compared with the maximum heat capacity of composting. During the experiment, the hotbed generated 98.7 MJ of heat, and its thermal efficiency reached 12% of maximum capacity. Radishes grown in the hotbed were harvested 5 days earlier than those grown in the cold frame and 12 days earlier than those grown in the garden treatment. The compost produced in the hotbed fully meets Polish Standards for organic fertilizers. The proposed solution minimizes the quantity of biological waste collected from households.

The influence of mixing inside the fermentation reactors during the study of biogas efficiency of the substrates in mesophilic technology

Along with the development of environmental friendly technologies, an increasing interest in generating the electricity and heat from renewable sources has been observed in Poland. Perfect example of such installations are agricultural biogas plants, where methane fermentation produces high-energy gas fuel i.e. biogas. Before investing, it is necessary to perform a detailed studies of the biogas efficiency of the substrates used. The proper run of fermentation process, as well as the high biogas production related to the operation, depend on many factors, including the mixing inside the reactor. The DIN 38 414-S8 standard, commonly used in the tests, assumes the mixing of the whole eudiometric sets, used in accredited laboratory units, which due to their uniform construction may cause problems. The aim of the study was to determine the effect of laboratory mixing in the fermentation reactor on the biogas efficiency of the maize straw. The experiment tests were performed in the Laboratory of Ecotechnologies, in the Poznan, in accordance with the current standard DIN 38 414-S8.The obtained research results confirmed the effect of mixing inside the fermentation reactors on the biogas efficiency of the maize straw.

Impact of Coffee Grounds Addition on the Calorific Value of the Selected Biological Materials

Abstract The objective of the paper was, inter alia, to determine the impact of coffee grounds on the heat of combustion of their combination with other biological materials. Research on the heat of combustion and calculations of the calorific value were carried out with the use of a KL-12 Mn calorimeter according to the technical specifications and standards PN-81/G–04513 i PN-ISO 1928:2002. Coffee grounds, tea grounds, pine wood and yellow wheat straw were used in the research. The heat of combustion of particular substrates was determined and then their mixtures with coffee grounds in the following proportion were prepared: 75% substrate – 25% coffee grounds, 50% substrate – 50% coffee grounds, 25% substrate – 75% coffee grounds. Calorific value of particular substrates was increasing with the amount of added coffee grounds. Their biggest flow was reported in the mixture of 50%/50% of coffee grounds and wheat straw and the smallest in case of coffee grounds and wood on account of a similar calorific value of both substrates.