Fermentative hydrogen production from molasses—a renewable by-product of beet-sugar processing—was considered. Technical and economic evaluations were performed of a stand-alone production plant employing a two-step fermentation process (dark thermophilic fermentation and photofermentation) followed by an adsorption-based upgrading of the produced hydrogen gas. Using a state-of-the-art knowledge base and a mathematical model composed of mass and energy balances, as well as economic relationships, the process was simulated and equipment data were estimated, the hydrogen cost was calculated and a sensibility analysis was carried out. Due to high capital, operating and labor costs, hydrogen production cost was estimated at a rather high level of 32.68 EUR/kg, while the energy output in produced hydrogen was determined as 68% more than the combined input of the thermal and electric energy needed for plant operation. As the room for improvement of plant performance is limited, a perspective on the cost competitiveness of large-scale hydrogen production from fossil sources is unclear.

This paper summarizes the results of the flow boiling heat transfer study with ethanol in a 1.8 mm deep and 2.0 mm wide horizontal, asymmetrically heated, rectangular mini-channel. The test section with the mini-channel was the main part of the experimental stand. One side of the mini-channel was closed with a transparent sight window allowing for the observation of two-phase flow structures with the use of a fast film camera. The other side of the channel was the foil insulated heater. The infrared camera recorded the 2D temperature distribution of the foil. The 2D temperature distributions in the elements of the test section with two-phase flow boiling were determined using (1) the Trefftz method and (2) the hybrid Picard–Trefftz method. These methods solved the triple inverse heat conduction problem in three consecutive elements of the test section, each with different physical properties. The values of the local heat transfer coefficients calculated on the basis of the Robin boundary condition were compared with the coefficients determined with the simplified approach, where the arrangement of elements in the test section was treated as a system of planar layers.

The present work is an extension of the authors’ previous research, where changes in the dynamic behavior of heat exchangers induced by fouling build-up were studied. In the present work, the authors used the previously elaborated and validated mathematical model of transient heat exchange with the influence of thermal resistance of fouling taken into account. The behavior of specific Heat Exchanger Networks (HENs) coupled with a Crude Distillation Unit together with their control loops is simulated using Simulink/MATLAB and the influence of fouling build-up on specific indices of quality of operation is investigated. According to the presented results, the higher the number of heat exchangers in the PID control loop and the greater the number of heat exchangers interacting in the network, the smaller the influence of fouling on the control quality indices, and in the extreme case, this influence may be negligible. This might be caused by the compensation of the negative effects of fouling build-up when the heat exchangers are interacting in the HEN. Nevertheless, potential adverse effects of fouling on HEN operation can be prevented by periodic adjustments of the optimal values of PID gains.

Photovoltaics (PV) is the phenomenon of converting sun energy into electric energy by using photovoltaic cells. Furthermore, solar energy is the major renewable energy source. PV modules are systematically more efficient and manufacturing costs decrease at the same time. The PV module performance is affected by ambient temperature, humidity, wind speed, rainfall, incident solar radiation intensity and spectrum, dust deposition, pollution, and shading, which are environmental factors. The problem of partial shading of the generator often arises when designing photovoltaic installations. If it is not possible to avoid this phenomenon, its impact on the operation of the photovoltaic system should be estimated. The classical method is to measure the current–voltage characteristics, but it requires switching off the installation for the duration of the measurements. Therefore, this paper proposes a method using a computer simulation in the Matlab package with the implemented component “Solar Cell” for this purpose. Three cases of partial shading of photovoltaic modules with different degrees of shading were analyzed. The obtained results of the computer simulation were verified for two types of silicon PV modules: Mono- and polycrystalline.

Investigation of the heat transfer by conduction and convection through a finned housing of an electric motor rated 373 W operated in the drive unit of a vacuum pump was carried out. As the speed is changed, so is the velocity of air flow, and consequently, the coefficient of heat transfer across the housing surface is changed too. To predict the values of the average heat transfer coefficient and to determine the heat flow that was dissipated at variable motor speed is a complex task, for which no reliable tools can be found in the literature. Using finite element approximation, the heat transfer was numerically simulated and the temperature distribution on the housing surface was determined. In order to validate the simulation model, an experimental set-up was assembled, including the vacuum pump complete with its driving unit, that is, electrical motor and frequency converter, and FLIR SC7600 thermovision camera. Using the validated simulation model, the heat flux transferred through the housing to the environment and the share of heat dissipation in the power consumed by the vacuum pump drive was determined. The combination of numerical simulation and thermographic measurements is an effective tool.