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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]

Passive solutions in buildings have recently been rediscovered because they allow the rational use of solar radiation, which promotes energy savings. Thermal energy gained from the sun may be stored in the form of sensible heat in accumulative solid materials in a building envelope. This paper proposes an innovative solar air heater that captures and accumulates solar energy during the day and releases it during the night. The analyzed system is based on inexpensive ceramic modules, which can be used to construct thermal storage walls or solar chimneys in modern buildings. Both configurations have been tested experimentally and by a numerical model in ArCADia BIM software. Experiments have been carried out in laboratory conditions using a specially developed prototype. Among other parameters, power transferred from the solar air heater to the ventilation air in different conditions has been analyzed. When airflow was set to 150 m3/h, the maximum power observed under stable working conditions was approx. 355.0 W when the developed solar air heater operated as the solar chimney, and approx. 165.0 W when it operated as the solar thermal wall. When airflow was set to 200 m3/h, the maximum power was approx. 385.0 W. Experimental results have been used to calculate the efficiency of the solar air heater in real conditions. The total efficiency in the case of the solar chimney was estimated as 0.25, while in the case of the thermal wall it was estimated as 0.78, which resulted in an annual reduction in energy usage at a level of 190.7 kWh and 556.1 kWh, respectively (4.8 and 14.0%). In practice, these values can be significantly higher due to the possibility of increasing the length and shape of the accumulation heat exchanger. [ABSTRACT FROM AUTHOR]

Numerous numerical and experimental studies have been conducted regarding the Concentrated Photovoltaic Thermal (CPVT) system because of its significant potential for efficient conversion of solar energy. The overall efficiency of the CPVT system is strongly dependent on the device, which extracts excess heat from photovoltaic cells. The most efficient cooling technology involves active cooling, which means that heat is collected from the PV cell via the forced flow of heat transfer fluid. This research paper provides an extensive discussion on devices dedicated to active-cooling CPVT systems, taking into account the latest solutions. First, a short introduction regarding CPVT systems and their main components is presented. The second part of this study presents state-of-the-art solutions in the field of heat extraction devices for the active cooling of photovoltaic cells. The available solutions are classified into two main groups depending on the scale of internal channels: macro- and micro-. Each geometry of the heat receiver is juxtaposed with the corresponding concentrating element, photovoltaic cell, concentration ratio, heat transfer fluid, and operating parameters of the specified system. In addition, this paper discusses the advantages and disadvantages of various devices for heat extraction and provides a comparative study of these devices. Finally, a set of recommendations for CPVT cooling devices is provided. [ABSTRACT FROM AUTHOR]

Among all the energy production technologies based on renewables, the photovoltaic panels are the ones with the highest rate of development and applications worldwide. In this context, significant efforts are put into research on innovative materials in order to improve the performance of photovoltaic cells. Nevertheless, possibilities available to enhance the energy yield of existing technologies also exist and are explored, such as the cooling of photovoltaic modules. This approach can decrease the mean operation temperature of photovoltaic cells, leading to an increase in efficiency and energy produced. In the present paper, this method is investigated by developing and testing a dedicated water cooling system for photovoltaic panels. In order to investigate the performance of the cooling system, two market-available monocrystalline photovoltaic panels with a power of 50 and 310 Wp were tested under laboratory and real operation conditions, respectively. Based on the results obtained under laboratory conditions, the most promising variant of the cooling system was selected and assessed under real operation conditions. For this system, the maximum temperature of the water-cooled 310 Wp panel was lower by approx. 24 K compared to an uncooled panel, as pointed out by a measurement performed during a typical sunny day when solar irradiation was approximately 850 W/m2. This improvement of the cell temperature led to a 10% increase in power generated by the water-cooled photovoltaic panel compared to the uncooled one. The economic analysis revealed that the estimated simply payback time for installing the cooling system in typical domestic photovoltaic installations can be less than 10 years, while from the point of view of net present value, the introduction of the water cooling system can be a profitable option for a 10-year period when a discount rate of 5% is considered. [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]

Abstract Nowadays, the use of wood for cooking and heating has become very popular, especially in rural and suburban areas. Fireplaces and solid fuel stoves with heat accumulation provide both low-cost heating and an aesthetic atmosphere from burning wood. Additional benefits may also be connected with micro-scale power generation, realized using thermoelectric generators. The aim of this study was to examine the selected aspects of integration of a typical wood-fired stove with commercially available thermoelectric generators. Among several aspects included in the carried out analysis, there were e.g. the operation parameters of the tested stove (including temperature variations during combustion process), the efficiency of electricity generation in the tested thermoelectric generators and the requirements for the stove configuration and operation. Three types of thermoelectric generators were tested: two generators designed for mounting on a flat hot surface (cooling respectively by air and water) and one designed for mounting on a flue gas channel (cooling by water). The experiments were carried out using dedicated measuring, controlling, and visualizing systems with a PLC controller as well as an infrared camera. Thermographic analysis allowed determining of the temperature distribution on the rear wall of the stove and selection of the most optimal areas for mounting generators. However, non-homogeneous temperature distribution was observed, identified as one reason for lowering of operational efficiency of the generators. A further problem was identified in the case of the generator mounted on the flue gas channel being too low a cross-section of its gas channels (reducing flue gas flow volume). These problems significantly impacted on the operating characteristics of the thermoelectric generators – meaning they produced no more than 41.7, 31.2, and 7.2% of their nominal power, respectively. The obtained results enabled the proposal of two approaches connected with further development of the micro scale cogeneration systems with thermoelectric generators: These two methods would differ in terms of costs, final product price, and necessary fitting of production lines. Highlights • Good thermal contact and sufficient heat flux is essential for the TEGs operation. • Theoretically available power of TEGs is impossible to reach in real conditions. • Water cooling system is recommended for the increase in power generated in TEGs. • Up to 41.7 ± 3% of the nominal power of the TEG No.1 was obtained during the tests. • TEG No. 1 is characterized by the highest possibility of application. [ABSTRACT FROM AUTHOR]

A significant part of the world’s population (about 40%) cooks their meals and provides heating for their homes using wood-burning heating devices. Due to the relatively low cost of fuel and their aesthetic design, solid fuel stoves capable of heat accumulation are convenient and common. The use of dedicated small-scale power generators provides also additional benefits. This paper presents the results of a study conducted to verify the possibility of generating power using stove-fireplaces with heat accumulation systems. In such units, the temperature of the flue gas should be kept at a certain level for the purposes of storing heat, which results from certain limitations of the thermoelectric generators. To verify the possibility of applying thermoelectric modules in such heating devices, a dedicated system with thermoelectric generators was selected from among various microcogeneration systems and implemented. Three types of heat exchangers were studied and the most efficient unit was selected for further testing. Two types of generators, with maximum operating temperatures of 320 and 175 °C, were compared. Subsequently, the characteristics of the latter were determined. The conducted tests allowed to determine the performance and the total efficiency of the generators that were used. It has been demonstrated that the maximum power of the generator would not exceed ca. 30 W e and that there is no economic justification for such a device. However, providing a self-powered and self-sufficient operation of stove-fireplaces with heat accumulation systems remains an important goal. [ABSTRACT FROM AUTHOR]

• Solar energy can be effectively used to power an autonomous surface vehicle. • During summer days PV panel can match approx. 92% of the entire load of the vehicle. • The use of composite materials of natural origin can reduce the carbon footprint. • Dynamic simulation was conducted for different operation time and locations. • The change in location can increase the primary energy savings by about 30–50% Nowadays, the use of autonomous surface vehicles has increased in popularity. Autonomous surface vehicles can be adapted to perform water quality measurements, water contamination and hazards detection, garbage collection, aquatic animal population control, shore control, and other applications. This paper shows the novel construction of a small solar-powered autonomous surface vehicle. The vehicle was manufactured of composite materials of natural origin. It was equipped with an electric engine powered by ultralight photovoltaic panel, and a set of sensors and actuators used for autonomous operation and measurements of such factors, as pH, turbidity, purity, and oxygen content in water. The investigations carried out have been divided into three main parts. First, the geometry of the proposed autonomous surface vehicle was modelled using computational fluid dynamics and optimal shape of hull and deck was determined. Then, a dedicated construction of the photovoltaic panel was developed and tested under real conditions. The maximum power generated was 41.7 W when solar radiation was 850 W/m2. The matched power related to the area of 1 m2 was higher by 9.7% – 34.3% compared to other tested market-available panels. Finally, simulations in the TRNSYS software were carried out to determine the operational parameters of the developed autonomous surface vehicle under different operating scenarios. Simulations showed that the operation scenario of the autonomous surface vehicle significantly affects its primary energy consumption due to the energy supplied from the grid to recharge the system after each day of operation. The change in location can increase the primary energy savings, since among the investigated locations the primary energy saving ratio varied between about 30 and 50%. The analysis pointed out that the developed construction of the solar-powered small autonomous surface vehicle is a really promising solution and can be considered as an addition or replacement to the actual available water quality monitoring systems. [ABSTRACT FROM AUTHOR]

Thermoelectric generators are devices that harvest waste heat and convert it into useful power. They are considered as an additional power source in the domestic sector, but they can also be installed in off-grid objects. In addition, they are a promising solution for regions where there is a lack of electricity. Since biomass heating and cooking stoves are widely used, it is very appropriate to integrate thermoelectric generators with wood-fired stoves. This paper shows the experimental analysis of a micro-cogeneration system equipped with a wood-fired stove and two prototypical constructions of thermoelectric generators dedicated to mounting on the flue gas channel. The first version was equipped with one basic thermoelectric module and used to test various cooling methods, while the second construction integrated four basic thermoelectric modules and a water-cooling system. During the tests conducted, the electricity generated in the thermoelectric generators was measured by the electronic load, which allowed the simulation of various operating conditions. The results obtained confirm the possibility of using thermoelectric generators to generate power from waste heat resulting from the wood-fired stove. The maximum power obtained during the discussed combustion process was 15.4 W (if this value occurred during the entire main phase, the energy generated would be at a level of approximately 30 Wh), while the heat transferred to the water was ca. 750 Wh. Furthermore, two specially introduced factors (CPC and CPTC) allowed the comparison of developed generators, and the conclusion was drawn that both developed constructions were characterized by higher CPC values compared to available units in the market. By introducing thermoelectric modules characterized by higher performance, a higher amount of electricity generated may be provided, and sufficient levels of current and voltage may be achieved. [ABSTRACT FROM AUTHOR]

• The optimal temperature of the drying agent should be a maximum of 130 °C. • It is possible to obtain 120 MJ more energy burning dry straw compared to wet fuel. • An increase in boiler return temperature from 20 to 80 °C reduces PM emission by 50%. • The functionality of batch boilers may be increased with power generation. • The expected power generation in the system should be at a level of 10 kW el. This paper shows the results of experimental and numerical investigations related to the energy use of straw from the point of view of its preparation (drying), combustion, energy production and emissions. Experimental works on straw drying were conducted on a specially developed installation based on dedicated batch straw dryers, which use flue gas, coming from a 500 kW th boiler, as a drying medium. The further part of the work was conducted on a prototype of a micro-scale cogeneration system that operates according to a low temperature Rankine cycle and it is powered by a 100 kW th biomass-fired batch boiler. Conducted so far research allowed to analyse selected operation aspects of the developed system. An analysis of straw drying, proximate, ultimate, and heating value analysis, heat generation process in the boiler, steam generation process in the evaporator and superheater, steam engine operation as well as dust emissions during straw combustion related to the boiler return temperature were presented. Energy transferred from flue gases to straw with a high value of moisture content was 5.75 kW, which allowed to evaporate about 18.6 kg of water from 192 kg wheat straw bale. The moisture content was reduced from 36.9 to 27.2%. The power generated in the system was lower than the one expected, since only 1.15 kW el was achieved which was about 1% of the boiler's heat capacity. Such result was caused by construction restrictions of the installation. Experimental results were supported by dynamic simulations performed in TRNSYS software. The simulations were performed for both the current configuration of the system and suggested modifications. Simulation results showed, that the expected power generation in the final version of the system should be at a level of 10 kW el. Results obtained during the analysis of multi-cyclone operation showed, that the concentration of dust was reduced in a range from 55% to even 85% depending on the temperature of the boiler return and flue gas flowrate in multi-cyclone. [ABSTRACT FROM AUTHOR]

Renewable energy sources, such as solar, wind, biomass, and geothermal energy, are being more and more adopted in small and micro-scale distributed generation systems. In this context, different hybrid configurations and layouts that may adopt, lead to different energy and economic performance of energy generation systems. In micro-scale applications, biomass and solar energy sources are more frequently investigated in literature compared to other combinations as biomass and wind energy. The analysis of the performance of a novel small-scale trigeneration system is presented in this paper. The system includes biomass boiler, water steam turbine, absorption chiller, and wind turbine, and it is linked to the electric grid by means of a bidirectional connection, allowing to the store virtually the electrical energy produced in excess, and use when needed. For the proposed system, a zootechnical farm and a residential building are considered as case study, including different scenarios for the reference energy system. The Transient System Simulation (TRNSYS software is used to model, simulate, and investigate the system performance under realistic operation conditions. Energy and economic performance of the system is assessed by means of a daily, weekly, and yearly analysis. The effect of the main design parameters, as steam and wind turbine power on the system performance, is investigated by means of a sensitivity analysis. The investigations show that the Simple Pay Back time of the proposed system is below 6 years, when the biomass is free, capacities of steam and wind turbines lower than 4 kW are selected, and a reference system with a natural gas boiler and electrical grid is considered. The system allows one to achieve satisfactory energy and economic performance under the considered conditions, when a proper design of the system component capacities is adopted. [ABSTRACT FROM AUTHOR]

Combined heat and power systems dedicated to micro-scale applications are currently increasing in popularity. The use of such systems is beneficial from the standpoint of increasing the usage of renewable energy, increasing energy efficiency and reducing CO2 emissions into the atmosphere. This paper shows two examples of prototypical micro-cogeneration systems powered by biomass. In the first, smaller one, electricity is generated in thermoelectric generators using heat from the wood-fired stove. The second one is equipped with a 100 kWt batch boiler and operates according to a modified Rankine cycle. The energy and ecological analysis were conducted and discussed, including selected aspects of heat and power generation and gaseous pollutant emission. Measurements were performed using a dedicated control and measurement station with a PLC controller. As was shown, thermoelectric generators operated respectively with the power of 22.5 We in the case of the air-cooled unit and 31.2 We in the case of the water-cooled unit. On the other hand, the maximum power level of ca. 1145 We was obtained in the system with a batch boiler operating according to a modified Rankine cycle. The ecological analysis showed that the average amount of CO emission during the wood combustion in the tested stove was 1916 mg/m3 (in the combustion phase). In the case of straw combustion, it was characterized by lower CO2 emissions compared to coal, but higher CO2 emissions compared to gasoline and natural gas. Based on the obtained results, some outlines for the systems development were given. [ABSTRACT FROM AUTHOR]

The combustion processes of biomass occurring in furnaces run with an emission of exhaust gas consisting of groups of chemicals which occur both in gaseous and particulate-bound form. The purpose of the work presented in this paper was to investigate the impact of wood combustion processes occurring in domestic heating units (DHUs) on the emission of particulate matter (PM) and other exhaust components. The process of combustion was divided into three steps: A. firing, B. combustion, and C. post-combustion. During fuel burning, the weighting platform was used to measure variations in the mass of fuel and a gaseous analyzer was used to measure gaseous exhaust components such as CO 2 , CO, O 2 and SO 2. A dust sampler equipped with a dilution tunnel, a filter holder and a pump were installed in the stack. The samples of PM were collected on quartz fiber filters with a diameter of 47 mm. The PM was then analyzed for the presence of inorganic and organic components. The results obtained in the studies confirmed the influence of using the accumulation layer on the emitted exhausts. Application of accumulation layer led to decrease the emission of gaseous fumes (NO, NO x and SO 2), although, the CO and PM emission were higher. One also observed the impact of combustion phase on the chemical composition of collected PM. The highest measured concentrations of analyzed PAH compounds were determined for acenaphthene (Ace) and benzo(a)pyrene (BaP). In all analyzed events BaP mostly contributed to the budget of PAHs in the final phase of burning: during the post-combustion process, when the temperature in the combustion chamber decreased. The application of the accumulation layer enabled to decrease the BaP concentration in the ignition phase of burning. The highest concentration of Ace was observed for the combustion phase using the Stove 1, while in the Stove 2, both with and without an accumulation layer, the Ace concentration was higher in the initial phase of burning. [ABSTRACT FROM AUTHOR]

• Biomass-fired straw batch boiler was investigated dynamically. • Experiments were performed on the micro combined heat and power system. • A parametric study of the system was presented. • Simple Pay Back Time of the installation was between 1 and 15 years. • It is possible to obtain about 2 times higher electrical efficiency. Microscale heating devices are mandatory for users located in areas lacking of heating networks, especially in the rural ones. An interesting option for schools, farms, houses, and other users is to increase the functionality of heating devices with the power generation option. Such systems may operate on the basis of a simple Rankine Cycle fired by biomass. In this paper, the energy and economic parameters of a prototype micro-cogeneration system based on a 100 kW th straw-fired boiler with a thermal oil jacket and a 14.8 kW steam engine were investigated. During the experimental tests, the power at a level of 1.1 kW el was obtained by the prototype installation when steam pressure was equal to 4.3 bars and steam mass flow was about 105 kg/h. The relatively low electric power resulted from a limited heat exchange surface of the evaporator and, undersized nominal power of electricity generator and piping heat and pressure losses. On the other hand, the maximum measured pressure was 10 bars, when steam temperature was ca. 200 °C, pointing out that the installation has a significant potential of improvement from the power generation point of view. A dynamic simulation model was developed using TRNSYS software in order to investigate the system capabilities. This model was calibrated using experimental investigations, and further technical improvements of the installation were analyzed from energy and economic points of view. The possibility of integrating an absorption chiller in the system was also considered. As a result, the operation of the existing micro-cogeneration system was simulated and the operation parameters of the proposed micro trigeneration system were analyzed. [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]