The transition towards Nearly Zero Energy Buildings (nZEB) requires renewable energy systems to cover the thermal energy need. These have to cover the demand for domestic hot water, for heating and ...for cooling, in the needed amount and during the required periods, according to the building types and the implementation locations. Solar-thermal systems can play a key role in the sustainability scenario of any nZEB. However, implementing solar thermal systems beyond demonstration projects requires innovative solutions able to surpass the barriers that currently limit the widespread of these types of systems. Therefore, several prerequisites have to be fulfilled, related to functionality (efficiency), feasibility (implementation and O&M costs), architectural integration (giving use to roof, rooftops but also to suitably oriented facades), and end-users acceptance (incentives, promotion, etc.). These novel solutions were implemented in the R&D Center Renewable Energy Systems and Recycling, in the Transilvania University of Brasov and the results of infield optimized implementation confirm the viability of the novel trends presented by the paper.
In this work, the CMK-3 is successfully prepared with SBA-15 as the template and first annealed to 2000 °C to improve thermal conductivity. The annealed CMK-3 has a thermal conductivity of 6.981 W m
...K
higher than un-annealed CMK-3. The annealed CMK-3 is used to encapsulate the RT44HC, and RT44HC/annealed CMK-3 has 10-fold of thermal conductivity and enhanced thermal stability than RT44HC. The RT44HC/annealed CMK-3 has a large melting enthalpy of 177.8 J g
and good thermal stability. The RT44HC/annealed CMK-3 has optical absorptive coefficient of visible range of solar spectrum, which identify seven-fold higher than RT44HC. The RT44HC/annealed CMK-3 has great photo-thermal performance, and the photo-driven energy charging and discharging rate of RT44HC/annealed CMK-3 is almost 30-fold larger than the RT44HC. The results show that the annealed CMK-3 is a great mesoporous carbon nanomaterial for phase change materials and the annealed CMK-3 based phase change material has great potential in solar thermal utilizations such as solar water heating system and solar heating building systems.
Solar thermal systems with a total solar panel area varying from 2 to 204 m2 have been installed in Lithuania for over 20 years. The reviewed solar thermal domestic hot water systems in Lithuania ...produce up to 528 kWh per year per one square meter of solar collector absorber area. However, the performance of these systems varies depending on the type of energy users, equipment and design of the systems, as well as their maintenance. The aim of this paper was to analyse solar thermal systems from the perspective of energy production and economic benefit as well as to outline the differences of their actual performance compared to the numerical simulation results. A number of different solar thermal systems in Lithuania were selected for the analysis varying both in equipment used (flat type solar collectors, evacuated tube collectors) and type of energy user (domestic hot water heating, swimming pool, district heating). The simulation software Polysun 8.1 was used for evaluation of solar thermal system performance, as well as financial analysis of alternatives of these systems. The results of the analysis showed that in the analysed cases the gap between measured and modelled data of heat energy produced by solar thermal systems was up to approximately 11%. The calculation of internal rate of return showed that a grant is required in most cases for solar thermal projects to be fully profitable.
Solar heating systems have the potential to be an efficient renewable energy technology, provided they are sized correctly. Sizing a solar thermal system for domestic applications does not warrant ...the cost of a simulation. As a result simplified sizing procedures are required. The size of a system depends on a number of variables including the efficiency of the collector itself, the hot water demand and the solar radiation at a given location. Domestic Hot Water (DHW) demand varies with time and is assessed using a multi-parameter detailed model. Secondly, the national energy evaluation methodologies are evaluated from the perspective of solar thermal system sizing. Based on the assessment of the standards, limitations in the evaluation method for solar thermal systems are outlined and an adapted method, specific to the sizing of solar thermal systems, is proposed. The methodology is presented for two common dwelling scenarios. Results from this showed that it is difficult to achieve a high solar fraction given practical sizes of system infrastructure (storage tanks) for standard domestic properties. However, solar thermal systems can significantly offset energy loads due associated DHW consumption, particularly when sized appropriately. The presented methodology is valuable for simple solar system design and also for the quick comparison of salient criteria.
In this work, the issues of development of high-temperature solar collectors have been discussed. The structure of a newly-developed solar collector, as well as the design parameters of its ...components and the results of experiments has been described. Collectors of this class are a core part of self-sustained energy supply system for rural buildings and settlements. The newly-designed solar collector is capable to store intensively heat energy in periods of solar energy in excess to the demand and to supply heat and generated electricity in periods when solar energy income is insufficient and collector alone can not sustain system operation. The newly-designed solar collector is an integral part of the entire energy supply system of self-sustained buildings. The energy produced by collector is consumed in the systems of hot water supply, heating, air conditioning, cooling and electric power supply.
Within the Aktifas project, a road map is being developed for research and development of façade-integrated solar thermal systems. The road map is based on an analysis of the barriers for ...façade-integrated solar thermal systems as well as a market overview of existing components. This paper presents the methodology for creating the road map as well as first results. The final road map will be published on http://bit.ly/Z0hkso at the beginning of 2015.
•A simulation-based fault detection approach for solar thermal systems was developed.•Faults are detected by comparing simulated and measured energy yields.•Faults causing an energy loss of ca 25% ...can be detected.•A field test with three systems between 15 and 1290m2 was carried out.•Several faults were detected, identification of faults is more difficult.
This paper discusses a simulation-based fault detection approach for detecting faults during the operation of low-temperature solar thermal systems. An effective fault detection approach for solar thermal systems can ensure a quick response and reparation of occurring malfunctions that cause a reduced solar energy yield. Several fault detection methods can be applied, e.g. manual fault finding, algorithms, spectral analysis or simulation-based fault detection.
The simulation-based fault detection approach is based on an hourly, daily or monthly comparison of measured and simulated energy yields. The method was applied and evaluated for three field test systems with different hydraulics and a collector area between 15 and 1290m2. Several faults were successfully detected. Faults in the solar loop can be detected as long as the fault causes a large enough energy loss in comparison to the uncertainties of the simulated and measured energy yield. Fault diagnosis turns out to be more difficult and is expected to greatly improve by integrating the simulation-based fault detection approach in a larger framework that includes data management and algorithm-based fault detection.
Exergy analysis is a more powerful tool than mere energy analysis for showing the improvement potential of energy systems. Direct use of solar radiation instead of degrading other high quality energy ...resources found in nature is advantageous. Yet, due to physical inconsistencies present in the exergy analysis framework for assessing direct-solar systems commonly found in literature, high exergy losses arise in the conversion process of solar radiation in direct-solar systems. However, these losses are disregarded in indirect-solar systems.
In this paper, contradictions and physical inconsistencies which result from including the conversion of solar radiation only for direct-solar systems are shown. An evaluation framework physically coherent for systems making direct and indirect use of solar radiation is derived and its physical correctness is thoroughly discussed. Results from case studies using the proposed framework are presented and compared with the conventional approach, enabling their direct comparison and better understanding of the benefits and correctness of the proposed method. The new method allows recognizing clearly the suitability of direct-solar systems, being appropriate for highlighting more sustainable energy supply systems.
Although this paper focuses on building systems, the framework might be used for exergy analysis of direct-solar systems in the context of other energy uses.
AbstractThe energy used in the built environment represents approximately 40% of the total energy consumed by the community, with significantly higher values in rural communities. Out of this, a ...significant share is used for heating, cooling, and domestic hot water (DHW) production. Therefore, identifying renewables-based thermal energy production systems represents an essential step in the transition toward the status of sustainable communities; however, their wide spread has to be supported by efficiency and a high social and economic acceptance. The use of renewable energies in collective households is currently facing certain technological and financial barriers; therefore, acceptable and affordable implementation needs to be stepwise designed by (partially) involving the already existing infrastructure. Technical and economic feasibility is supported by accurate design that considers the local variability of the renewables’ potential and consumption. In a first step, renewables-based DHW production can be considered because this is relatively constant throughout the year, and solar–thermal systems represent good candidates because there already exists a high degree of acceptance at the community level for this type of system. This paper presents a novel methodology for the design of solar–thermal systems implemented in rather small communities, considering the actual energy consumption for DHW production in collective households (based on the local solar energy potential; the methodology targets the identification and use or extension of energy production and distribution systems). A case study (Taberei District in Odorheiu Secuiesc City, Harghita County, Romania) is detailed, allowing technical analysis and feasibility assessment and also considering affordability and sustainability.
The purpose of this work is to present a comparison between two standardized test methods for the evaluation of the energy performance of Solar Domestic Hot Water (SDHW) systems. The approaches ...investigated concern the Dynamic method (DST) and the Input–Output method (CSTG). These methods have been officially established as ISO standards, thus they have found wide dissemination, and their results are supposed to be equivalent to one another.
A description of the operation principle of each method and the corresponding test procedures is presented, focusing on the aspects related to the practical implementation of these methods on a laboratory level.
A Solar Domestic Hot Water system is tested according to both methods. On the basis of the measurements, the characteristic parameters of the SDHW system are calculated for each method and the long-term performance under typical meteorological conditions is estimated. Consequently, a comparative evaluation and analysis of the observed deviations between the results of the two methods are performed.
Besides the quantitative comparison, this work has attempted to evaluate the two methods on a qualitative basis as well, by focusing on their functionality, their requirements regarding the number of test days considered and the physical interpretation of the results.
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