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Among the various renewable energy-based technologies, photovoltaic panels are characterized by a high rate of development and application worldwide. Many efforts have been made to study innovative materials to improve the performance of photovoltaic cells. However, the most commonly used crystalline panels also have significant potential to enhance their energy yield by providing cooling and cleaning solutions. This paper discusses the possibility of introducing a dedicated direct-water cooling and cleaning system. As assumed, detailed schedules of the operation of the developed direct water cooling and cleaning system should be fitted to actual weather conditions. In this context, different cooling strategies were proposed and tested, including different intervals of opening and closing water flow. All tests were conducted using a dedicated experimental rig. 70 Wp monocrystalline panels were tested under laboratory conditions and 160 Wp polycrystalline panels were tested under real conditions. The results showed that introducing a scenario with a 1-min cooling and a 5-min break allowed for proving the panel's surface temperature lower than 40 °C. In comparison, the temperature of the uncooled panel under the same operating conditions was close to 60 °C. Consequently, an increase in power generation was observed. The maximum power increase was observed in July and amounted to 15.3%. On the other hand, considering selected weeks in May, July, and September, the average increase in power generation was 3.63%, 7.48%, and 2.51%, respectively. It was concluded that the division of photovoltaic installation allows reasonable operating conditions for photovoltaic panels with a lower amount of energy consumed to power water pumps. [ABSTRACT FROM AUTHOR]

The efficiency of solar systems, in particular photovoltaic panels, is typically low. Various environmental parameters affect solar panels, including sunlight, the ambient and module surface temperatures, the wind speed, humidity, shading, dust, the installation height, etc. Among others, the key players are indeed solar irradiance and temperature. The higher the temperature is, the higher the short-circuit current is, and the lower the open-circuit voltage is. The negative effect of lowering the open-circuit voltage is dominant, consequently lowering the power of the photovoltaic panels. Passive or active cooling systems can be provided to avoid the negative effect of temperature. This paper presents a prototype of an active cooling system dedicated to photovoltaics. The prototype of such a system was developed at the AGH University of Kraków and tested under laboratory conditions. The proposed system is equipped with air fans mounted on a plate connected to the rear part of a 70 Wp photovoltaic panel. Different configurations of the system were tested, including different numbers of fans and different locations of the fans. The artificial light source generated a irradiation value of 770 W/m2. This value was present for every variant tested in the experiment. As observed, the maximum power generated in the photovoltaic panel under laboratory conditions was approx. 47.31 W. Due to the temperature increase, this power was reduced to 40.09 W (when the temperature of the uncooled panel surface reached 60 °C). On the other hand, the power generated in the photovoltaic panel equipped with the developed cooling system was approx. 44.37 W in the same conditions (i.e., it was higher by 10.7% compared to that of the uncooled one). A mathematical model was developed based on the results obtained, and simulations were carried out using the ANSYS Workbench software. After the validation procedure, several configurations of the air cooling system were developed and analyzed. The most prominent case was chosen for additional parametrical analysis. The optimum fan orientation was recognized: a vertical tilt of 7° and a horizontal tilt of 10°. For the tested module, this modification resulted in a cost-effective system (a net power increase of ~3.1%). [ABSTRACT FROM AUTHOR]

The potential energy of compressed air represents a multi-application source of power. Historically employed to drive certain manufacturing or transportation systems, it became a source of vehicle propulsion in the late 19th century. During the second half of the 20th century, significant efforts were directed towards harnessing pressurized air for the storage of electrical energy. Today's systems, which are based on storing the air at a high pressure, are usually recognized as compressed air energy storage (CAES) installations. This paper aims to provide an overview of different technologies that take advantage of the energy accumulated in the compressed air. Particular attention is paid to the CAES installations that are working as electrical energy storage systems (EESs). These systems, developed originally as large capacity (>100 MWe) and fuel-based installations, may soon become fully scalable, highly efficient, and fuel-free electrical energy storage systems. To present this opportunity, a thorough review encompassing previous and up-to-date advancements in their development was carried out. In particular, CAES concepts, such as diabatic (D-CAES), adiabatic (A-CAES), and isothermal (I-CAES), are described in detail. This review also provides the detailed characteristics of the crucial elements of these configurations, including compressors, expanders, air storage chambers, and thermal storage tanks. Knowledge of these components and their role allows us to understand the main challenges behind the further development of the mentioned CAES setups. Apart from the CAES systems that are designed as EES systems, this paper describes other prospective technologies that utilize the energy of pressurized air. Accordingly, compressed air cars and their key elements are explained in detail. Moreover, the technology renowned as wave-driven compressed air energy storage (W-CAES) is described as well, indicating that the utilization of pressurized air represents a viable option for converting ocean energy into electrical power. [ABSTRACT FROM AUTHOR]

According to the United Nations, one of the sustainable development goals is to ensure access to affordable, reliable, sustainable, and modern energy for all. Among other options, these goals can be achieved by developing and introducing micro-scale combined heat and power systems powered by renewable energy sources, including solar and biomass energy. Considering renewable energy-powered cogeneration technologies, the most promising are steam/vapor turbines, Stirling engines, and thermoelectric generators. This paper focuses on the selected operational aspects and retrofitting optimization of the prototypical micro-cogeneration system powered by a biomass-fired batch boiler and operating according to the modified Rankine cycle. The existing installation was tested, and the amount of energy transferred from the oil to the condensate and steam and the efficiency of the evaporator and the superheater were determined. A retrofitting optimization aimed at maximizing the piston engine's power output was conducted based on the results. In particular, it was shown that the system's power output might be as high as 9 kWe. Moreover, the analyzed system featured a high energy utilization factor of 97.9% at optimal operating conditions. In general, it was shown that the micro-scale steam Rankine system may successfully serve as an alternative technology for micro- and distributed cogeneration systems. As a technology supplied with renewable biomass energy and operating on a cheap and environmentally friendly working medium (water), it fits very well into the idea of sustainable energy system development. [ABSTRACT FROM AUTHOR]

Refrigeration systems are necessary for people living in hot climates. A majority of tropical and subtropical countries uses electrical power as a source of cooling. During the seasons of high ambient temperature there is a significant cooling load due to increased level of energy consumption. Cooling systems are therefore necessary in African countries in order to keep medications and food in safe conditions. Furthermore, there is a power shortage crisis due to the high demand for cooling. TRNSYS software allows to simulate a complete solar-powered absorption cooling system. A model used in an experiment includes PV modules making it advantageous over a conventional cooling system. PV modules of assumed area are sufficient to maintain the temperature inside cooling device below 6°C over the whole year.

Nowadays, almost 30% of total energy consumption (130 EJ) is consumed for the operation of buildings, mainly by space heating/cooling and ventilation systems, hot water preparation systems, lighting, and other domestic appliances. To improve the energy efficiency of buildings, several countries are promoting the use of renewable energy. The most promising systems include active and passive solar installations. In passive systems, the solar energy is collected, stored, reflected, or distributed by the roof ponds, natural convective loops, and the most popular direct gain walls and thermal storage walls (known as Trombe walls). This paper reviews the experimental and numerical studies devoted to the different solutions of Trombe walls, including solar chimneys integrated on the vertical walls, classic Trombe walls, Trombe walls with incorporated phase change materials, and photovoltaic Trombe walls. The actual state of the art is presented in the context of reducing energy consumption and enhancing thermal comfort. Most of the analyzed studies showed that the application of thermal storage walls allowed achieving these goals, led to lower emissions of greenhouse gases, and improved living standards. Nevertheless, there is a need for more detailed feasibility studies, including cost and environmental indicators. [ABSTRACT FROM AUTHOR]

Renewable energy based micro cogeneration systems are an interesting option for domestic, agricultural and commercial sectors. In this paper, a dedicated system with a 100 kWth biomass-fired boiler was proposed. Developed system works according to modified Rankine Cycle operation. Steam generated in two shell and tube heat exchangers is used to power steam engine (connected with power generator) and then flows via condenser to degasifier. During the presented tests, the selected parameters of the boiler, oil circuit and steam/condensate circuit were analyzed. As was shown, the maximum thermal power taken from the oil circuit to evaporate condensate and superheat steam was ~105 kWth (it was ~91% of thermal power generated in the boiler). The value steam pressure varied from 2 to 5 bars during operation of the steam engine. Steam mass flow was then equal to ~105 kg/h, what allowed to generate electric power at a level of ~1.05 kWel. Such a low value resulted e.g. from limitations in the oil temperature, limitations in the steam temperature, steam pressure and steam flow, limitations caused by power generator’s construction, as well as other construction and operating parameters.

This paper shows results of initial tests of prototypical microcogeneration system based on the modified Rankine cycle operation. This system is powered by a 100 kW straw-fired batch boiler which was adapted to operate as a high temperature heat source. Thermal oil, heated up to 190-200°C, transfers heat to two shell and tube heat exchangers (evaporator and superheater). Steam powers a 2-cylinder, double-acting, 20-horsepower steam engine. Then, it is condensed in a condenser (another shell and tube heat exchanger) and pumped to the degasser. Finally, condensate is pumped to the evaporator and the whole process starts again. The steam engine is connected with a power generator. The operation of the developed micro-cogeneration system is controlled by the control and measurement system based on WAGO PFC200 PLC controller. The following parameters are recording: temperature, pressure and medium flow (in the boiler, oil, steam and water circuits). The results of the initial tests are promising. Power generated in the system is actually about 1,0 kWel. Such power is sufficient for supplying a part of the system’s equipment. On the other hand, it is finally expected to ensure selfsufficient operation of the tested system.

Nowadays, the worldwide growing demand for energy from renewable sources is observed. This fact is related to a number of factors, especially environmental ones. In the renewable energy sector, the most dynamic development which can be seen is wind energy. This is due to the construction of huge wind turbines, whose power exceeds even a few megawatts. The main problem that should be solved is finding a proper location for such turbines. Generally, wind turbines are located off-shore and on-shore. The most favourable are off-shore due to better wind condition, which relates to power generation. Notwithstanding, it is possible to install smaller turbines in urban areas: so-called wind turbines in built-up areas or integrate wind turbines with buildings (BIWT). This creates an opportunity to develop an integrated system of small energy sources located directly in cities. However, it is necessary to be aware of the many problems connected with the above mentioned installations. The article presents an overview and data related to operation of wind turbines integrated with the Center of Energy AGH building.

This paper shows the results of analysis of the wind potential in selected locations in the southern Poland (placed in the Małopolskie, Świętokrzyskie and Podkarpackie Voivodships). The measurements and analysis of the wind resources in potential locations of the wind turbines are important part of the investment process. The statistical analysis involves the creation of histograms (e.g. histogram of the wind speed and direction) and fitting those histograms to theoretical distributions (e.g. Weilbull distributions of wind speed). Such analysis has been described and conducted using measurement data for four selected locations. Basis on the conducted analysis, the economy efficiency and environmental impact of wind turbine operation has been estimated. Three market available wind turbines have been included to calculate NPV, IRR and SPBT indicators. Then, the avoided emissions of CO2, NOx, SO2 and dust have been calculated. There were also conducted some calculation using TRNSYS simulation software. The results of simulations have been compared with measurement data and the level of convergence have been found.

The paper presents an analysis of the use and potential of hydropower in Podkarpackie (Subcarpathian) Voivodship. The current usage of hydropower in the Region is presented, divided for range of generated power, geographical location and given rivers. Existing and planned artificial water reservoirs are taken into consideration in frame of hydropower development in the Region. Selected case studies related to varied hydropower plants are discussed. Problems connected with development of the hydropower were identified and considered. For each county in the Region theoretical available power possible to install in the main rivers was indicated, taking into account environmental aspects, technical problems with connection to the electrical grid and overall possibility of the facility installation. For each county communities with the best favorable situation are indicated. It is discussed the analysis of the evaluation of the use of hydropower in Podkarpackie Voivodship and provided information on planned and considered investments in hydropower plants. In addition, an analysis of the energy potential of the main rivers of the Podkarpackie Region have been procced to indicating the most favorable areas for location of hydropower plants. Moreover, given the environmental conditions, an analysis of the power estimation of the hydropower plants were made.

The proper design of renewable energy based systems is really important to provide their efficient and safe operation. The aim of this paper is to compare the results obtained during traditional static calculations, with the results of dynamic simulations. For this reason, simulations of solar water heating (SWH) system, designed for a typical residential building, were conducted in the TRNSYS (Transient System Simulation Tool). Carried out calculations allowed to determine the heat generation in the discussed system as well as to estimate the efficiency of considered installation. Obtained results were compared with the results from other available tool based on the static calculations. It may be concluded, that using dynamic simulations at the designing stage of renewable energy based systems may help to avoid many exploitation problems (including low efficiency, overheating etc.) and allows to provide safe exploitation of such installations.

High demands in the field of energy efficiency and clean combustion make it necessary to looking for the new developments in the field of stoves, fireplaces and stove-fireplaces with accumulation. An interesting idea is to use the thermoelectric modules, which receive a heat from flue gas and convert it to the electricity. Electricity generated in this way may be used to power combustion optimizers and other components. This paper shows results of studied carried out to determine the possibility of combined heat and power generation using the stove-fireplace with accumulation. Thermoelectric generator with maximum hot side temperature at a level of 150°C was placed on the surface of the exchanger. Cooling down was realized using the dedicated water exchanger as well as the heat sink without and with an air fan. The experimental results allowed to define the effect of the different cooling systems on the output TEG voltage. Moreover, dependence of the current-voltage characteristics and generated power from the temperature was obtained.

A steam generator is an essential unit of each cogeneration system using steam machines. Currently one of the cheapest ways of the steam generation can be application of old steam generators came from army surplus store. They have relatively simple construction and in case of not so exploited units – quite good general conditions, and functionality of mechanical components. By contrast, electrical components and control systems (mostly based on relay automatics) are definitely obsolete. It is not possible to use such units with cooperation of steam bus or with steam engines. In particular, there is no possibility for automatically adjustment of the pressure and the temperature of the generated steam supplying steam engines. Such adjustment is necessary in case of variation of a generator load. The paper is devoted to description of improvement of an exemplary unit together with construction of the measurement-control system based on a PLC. The aim was to enable for communication between the steam generator and controllers of the steam bus and steam engines in order to construction of a complete, fully autonomic and maintenance-free microcogeneration system.

The organic Rankine cycle (ORC) is a very promising process for the conversion of low or medium temperature heat to electricity in small and micro scale biomass powered systems. Classic ORC is analogous to Clausius–Rankine cycle in a steam power plant, but instead of water it uses low boiling, organic working fluids. Seeking energy and economical optimization of biomass-based ORC systems, we have proposed some modifications e.g. in low boiling fluid circuit construction. Due to the fact that the operation of a micro steam turbine is rather inefficient from the technical and economic point of view, a specially modified air compressor can be used as a steam piston engine. Such engine should be designed to work at low pressure of the working medium. Studies regarding the first version of the prototype installation were focused on the confirmation of applicability of a straw boiler in the prototype ORC power system. The results of the previous studies and the studies described in the paper (on the new cogeneration unit) confirmed the high potential of the developed solution. Of course, many further studies have to be carried out.

Straw-fired batch boilers, due to their simple structure and low operating costs, are an interesting option for heating systems dedicated to use in houses, farms, schools, industrial facilities and other buildings. Commercially available solutions include typical water boilers and air heaters with a thermal oil jacket. The high temperature of thermal oil (180-200°C) mean straw-fired devices can be used as a source of heat for micro scale cogeneration and trigeneration systems. The first part of this paper shows an experimental analysis of a micro scale cogeneration system based on modified Rankine Cycle operation. A 100 kWth straw-fired batch boiler with thermal oil jacket was used as a high temperature heat source. Thermal oil, heated in the boiler, was transferred respectively to the evaporator, superheater and oil/water emergency heat exchanger. The steam generated was conditioned and used to power a 20 hp steam engine. Cooling water, heated in the condenser, was pumped to a 4 m³ water tank connected to two air coolers. Control of the system operation was realized using a dedicated automation system based on the PLC controller. In the second part of this study, a micro scale cogeneration system was developed and modelled in TRNSYS software on the basis of the experimental installation. The dynamic operation conditions in terms of temperatures and powers were analyzed for the main components of the system (boiler, evaporator steam engine, condenser). Moreover, some modifications in the system construction were proposed to improve its performance. The results of the experimental tests were used to identify the main aspects of the considered system--temperature, pressure and power levels in oil, steam and water circuits and operating parameters of the steam engine. Dynamic simulations performed in TRNSYS pointed to the nominal operation scenario for the tested system and showed the great potential for further improvements in the system construction. [ABSTRACT FROM AUTHOR]

This paper presents a modified global energy production computation formula that replaces the traditional Performance Ratio (PR) with a novel Solar Reliability Factor (SRF) for mobile solar tracking systems. The SRF parameter describes the reliability and availability of a dual-axis solar tracker, which powers a smart home automation system entirely by using clean energy. By applying the SRF in the global energy production formula of solar tracking systems, we can predict the energy generation in real time, allowing proper energy management of the entire smart home automation system. Regarding static deployed Photovoltaic (PV) systems, the PR factor is preserved to compute the power generation of these devices accurately. Experimental results show that the energy production computation constantly fluctuates over several days due to the SRF parameter variation, showing a 26.11% reduction when the dual-axis solar tracker's availability is affected by system errors and maximum power generation when the solar tracking device is operating in optimal conditions. [ABSTRACT FROM AUTHOR]

The editors would like to express their sincere gratitude to the following reviewers for their precious time and dedication, regardless of whether the papers were finally published: Peer review is the driving force of journal development, and reviewers are gatekeepers who ensure that I Applied Sciences i maintains its standards for the high quality of its published papers. [Extracted from the article]