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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]

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]