• Energy Research

Dynamic growth of photovoltaic capacity in Poland encourages many entities to invest in photovoltaic systems. However, in the case of buildings with low roof-bearing capacity it can be problematic or even impossible to mount conventional PV modules due to their relatively high weight. Hence, the use of lightweight PV modules is a potential solution. In this paper four different prototype silicon lightweight modules of novel structure manufactured by the Xdisc S.A have been investigated in terms of their electrical and thermal features. The measurements showed that all prototypes have efficiency exceeding 19.5% and power in range of 214 to 242 Wp at standard test conditions. Their area density is about 3.5 kg/m2 which is typical for lightweight modules. In turn, the Power-to-Weight Ratio exceeds 40 W/kg threshold and in one case reaches almost 58 W/kg. Thanks to the measurements, the prototypes could be modelled in PVsyst (PVsyst SA, Satigny, Switzerland). The performed simulations of an example PV system revealed that installations based on prototypes have comparable performance to a conventional installation. Nevertheless, at current prices they are less profitable than the standard system and it shows the need for future cost reductions in the manufacturing process. The proposed materials selection may be the starting point for search of inexpensive substitutes of these materials which still conserve modules high performance. A system based on the prototypes can still prove advantageous when simplicity and promptness outweigh higher initial costs.

In recent years, pressure has been growing to increase the share of renewable energy sources in electricity generation, which may offer opportunities for the development of geothermal energy in regions that have been so far considered unprofitable in this respect. One such country currently undergoing an energy transition is Poland in which low-temperature geothermal resources are currently used for district heating and recreation purposes. Nevertheless, research on the possibilities of using geothermal energy for electricity production is ongoing. The objective of this paper was to perform a comprehensive analysis of a binary power plant construction in relation to low-temperature petro-geothermal resources. The potential binary power plant is located in the area characterized by temperature of 120 ◦C at depths of 5000 m. About half of Poland’s area, especially the regions of western and central Poland, has these characteristics. It was assumed that brine at volume flow rate of 400 m3/h is a heat source for the Organic Rankine Cycle with isobutane as a working medium. The thermal efficiency based on the First Law of Thermodynamics and the power output were estimated at 10.5% and 1.79 MWe, respectively. In addition, the thermal efficiency based on the Second Law of Thermodynamics was calculated at 29.0%. For the calculated cycle parameters, a preliminary design of a two-stage axial turbine was constructed. All results were compared to the other binary power plants and they confirm that establishing the binary power plant in Poland would be thermodynamically justified. The main novelty of the present work is the combination of three issues, namely the selection of the low- temperature heat source, the design and analysis of the cycle together with a turbine adapted to these conditions.

The paper presents theoretical assumptions and implementation of the T-history method, which was used to estimate the thermal capacity and latent heat for phase change materials (PCMs). The research equipment, measurement system and obtained results were discussed. The T-history method was used to investigate the heating and cooling process of two PCMs, sold under the trade names of RT15 and RT18. Obtained results were compared with the manufacturer’s data. The analysis of the research results has led to the conclusion that the presented measurement method made it possible to perform a preliminary verification of the enthalpy–temperature dependency of the PCMs. The method can be also used for studying different commercial materials and estimating this dependency for materials of yet unknown properties.

Modern distribution grids may suffer problems of voltage distortion, especially along radial low-voltage feeders with a high penetration of intermittent, unbalanced and distorted loads and generation sources. It is a challenge to develop an effective voltage-regulation method using a straightforward implementation. This paper proposes a novel method for local voltage control and balancing using a shunt-connected energy storage system. The compensation principles are explained, and a complete controller design is proposed. The algorithm is designed to be implemented in power electronic converters that provide the interface between the storage and the grid. The original contribution is the development of a low-level control method, which includes voltage balancing and a method to minimize the compensator current and is to be implemented in power electronic converters that provide the interface between the storage and the grid. The calculation of active and reactive compensator currents is explained with relation to the estimated grid impedance. The efficacy of the designed controller is verified by laboratory experiments. It is shown that voltage regulation using the proposed method is achieved with less apparent power compared to a system where only reactive power is used. The controller presents a very good dynamic response to rapid voltage variations, such as unbalanced voltage dips. The applicability and constraints of the method are discussed with respect to the present state of the art in low-voltage-grid voltage regulation.

In the article, the method and algorithm for a control strategy of the operation of a micro combined heat and power (mCHP) unit and for reducing the power consumption peaks (peak shaving) are proposed and analyzed. Two scenarios of the mCHP’s operation, namely with and without the control strategy, are discussed. For calculation purposes, a boiler fired with wood pellets coupled with a Stirling engine, manufactured by ÖkoFEN, was used. These results were used to analyze two scenarios of the control strategy. In this study, the operation of mCHP was simulated using the energyPRO software. The application of this control strategy to dispersed mCHP systems allows for a very effective “peak shaving” in the local power grid. The results of calculation using the new algorithm show that the electricity generated by the mCHP system covers the total demand for power during the morning peak and reduces the evening peak by up to 71%. The application of this method also allows for a better reduction of the load of conventional grids, substations, and other equipment.