The energy output of solar-thermal systems using flat plate collectors can be improved by tracking. Tracking is well known as a path for increasing the amount of solar radiation received by the collector; additionally the paper proposes a new concept that considers the inverse tracking as a viable option for protecting the collectors against overheating. An analysis of the thermal energy output and conversion efficiency is done considering forward tracking in three different days with different radiation profile (cloudy, sunny and mixed days), followed by an analysis of the inverse tracking concept. The in-field data show that there is a limiting angle below which inverse tracking is not effective and this value is estimated at 40° as compared with the optimal orientation. A logical scheme is proposed based on four different programs for forward tracking, inverse tracking, maximum inverse tracking or fixing the collector; this decisional scheme covers a broad range of functional situations having as central concept the production of thermal energy only when needed, for satisfying the demand, decreasing the energy consumption for forced circulation and supporting the systems reliability and safety

A total of five different types of photovoltaic (PV) modules were comparatively analyzed in terms of electrical output, efficiency, and relative efficiency losses, based on infield data collected in a temperate mountain climate, to outline the influence of the high relative environmental humidity on the PV conversion efficiency during time intervals with clear sky and low amounts of incident solar irradiance. The mono- and poly-crystalline silicon, cadmium telluride (CdTe), copper indium selenium (CIS), and copper indium gallium selenide (CIGS) modules mounted on a fixed tilted, South-oriented platform were individually monitored or in groups of modules using power optimizers. The electrical energy production, the PV conversion efficiency, and the relative efficiency losses were correlated with the weather data, and the analysis discusses the lower electrical energy output during periods with high relative air humidity. The analysis indicates that in a temperate climate, during days with high humidity intervals similar to the ones discussed in the paper, crystalline silicon modules have the lowest efficiency losses, followed by CdTe, CIGS, and CIS modules. The results can be useful for PV system designers, installers, and end-users of PV systems for a better system design and for a more accurate prediction of the daily energy production.

Developing efficient, sustainable, and affordable buildings requires combinations of passive and active measures that exploit specific onsite features. However, in temperate climates, reducing the heating demand (by south-oriented, triple-glazed curtain walls) has as a direct consequence an increased cooling demand. Using data collected over three years (2013–2015) in a mountain temperate continental climate, this paper analyzes the effect of (passive) natural night ventilation and (active) ceiling cooling on reducing the cooling demand in large office spaces in energy-efficient buildings. The results match those modeled using in-field climatic input data, whereas simulations using interpolated data lead to differences compared with experimental data. The results show that natural night ventilation decreases the cooling demand by 97% in June, and reductions of 33% are reached during the hottest month, August. When involving natural night ventilation and ceiling active cooling (heat pump in reversed mode), 88% coverage of the cooling demand is reached in August. A significant indoor temperature gradient (10°C) is registered during hot days, with peak differences in early afternoon, suggesting a need for customized cooling algorithms.

One key component of the energy demand in the built environment is the thermal energy required for domestic hot water preparation. Currently, fossil fuels are mostly used to meet the thermal energy demand in the built environment, lately, solar thermal systems have been increasingly implemented, mainly for domestic hot water preparation, enhancing the building's sustainability. A case study is presented in the paper for a solar thermal system with six flat plateand three evacuated tube solar thermal collectors installed on the rooftop of the Renewable Energy Systems and Recycling Research Centre, in the Colina Campus of the Transilvania University of Brasov, Romania. In 2017, this system provided 17,412 kWh of thermal energy to prepare domestic hot water for a Solar House and for the Sports Hall locker rooms. Evacuated tube solar thermal collectors showed better specific thermal output than flat plate ones.

The suppression of the recombination of photogenerated carriers in a dye-sensitized nano

Space heating represents the largest share in the energy demand of the built environment, in temperate and cold climates. Therefore, the use of solar thermal systems to convert solar into thermal energy for space heating, along with domestic hot water production, represents a challenge in these climates where the number of sunshine hours is rather low during the cold seasons, when heating is needed. Novel solar thermal collectors with nonrectangular shape (trapeze) and different colours (red, blue, green) were developed in the Renewable Energy Systems and Recycling Research Centre in the Research and Development Institute of the Transilvania University of Brasov, Romania, to increase the coverage factor, social and architectural acceptance when integrated in buildings facades. The results for an entire year (2017) are presented as monthly thermal energy produced by novel trapeze versus commercial rectangular flat plate solar thermal collectors installed on the vertical southern facade of an outdoor testing rig. The specific thermal energy produced by trapeze collectors is 28.7% lower than commercial collector over the entire year, but this drawback is compensated by higher coverage factor which can be obtained by using trapeze instead of rectangular solar thermal collectors.