Building-integrated Solar Thermal Systems Research Articles

Energy performance evaluation of a plus energy house based on operational data for two years: A case study of an all-electric plus energy house in Korea

The concept of zero-energy buildings is gaining much interest, and its technical feasibilities have been demonstrated for sustainable development. Although several case studies present how effectively zero-energy performance can be achieved, there is still a lack of data understanding adopting different combined passive and active systems for zero-energy performance. In response to this gap, this study introduces new integrated systematic approaches of enabling all-electric zero-energy performance and presents these features and operating performance for each part of energy consumption contributors based on measured data over two years. Structural insulation panels, vacuum glazing with heated glass were applied as passive techniques. An air-source heat pump and package air conditioner were used for heating and cooling systems, respectively. In addition to the passive and active systems, building-integrated solar thermal and roof-integrated photovoltaic (RIPV) systems were installed to offset all the remaining energy in the house. The energy use intensity of the house was 77.98 kWh/m2·yr; heating and domestic hot water had the highest consumption. To save cooling consumption, exterior electric venetian blinds and natural ventilation were used to cut down energy consumption. The house consumed 7,368.95 kWh/yr and produced 11,439.68 kWh/yr through the RIPV, the annual RIPV surplus accounting for 35.58 % of the annual energy production. The results from this case study provide a comprehensive overview of the feasibility of different combined technologies and insights into proper design strategies to improve the performance of zero-energy houses and buildings from another point of view.

A conceptual framework on the integration of solar energy systems in heritage sites and buildings

The integration between solar energy systems and building components is highly critical in sensitive heritage contexts. On the one hand there is the need for finding a balance between the preservation of the aesthetic appearance and the historical values, but on the other hand, finding the space where to effectively integrate the systems might be quite challenging. The solar systems can be divided in photovoltaic (PV) and solar thermal (ST) systems. Building Integrated Photovoltaics (BIPV) and Building Integrated Solar Thermal (BIST) are PV or ST panels integrated into the building envelope, combining the energy generation with other functions, such as noise, weather protection, thermal insulation, sun shadow, and other aspects. Nowadays, the dynamism of the market allows to design highly compatible products which look like traditional architecture materials. This situation fosters the integration of these products in the BIPV and BIST systems within the heritage sites, especially thanks to the use of advanced customisation processes, special and low-reflecting glasses, and innovative cost-competitive coatings. There is a limited number of studies on the application of these technologies in heritage contexts, due to the presence of architectonic, conservative, and cultural barriers. This paper aims to conduct a comprehensive review of the available literature on the integration of renewable energy sources (RES) in heritage sites and buildings, which would foster the preservation of their cultural and natural values as well as reducing primary energy consumption, increasing comfort levels, minimizing environmental impacts, and improving technical quality and economical outlays. A common framework will thus defined to support restorers, historic conservators, and energy experts and to facilitate the diffusion and application of RES in heritage contexts. This conceptual framework will provide industries and academics with operative strategies and will encourage their diffusion and application in sensible contexts.

Thermal performance of a novel solar thermal facade system in a hot-summer and cold-winter zone

This paper presents a novel solar thermal facade system able to employ renewable energy to relieve building energy consumption. The flat-plate collector, reflection layer, main wall, and indoor radiation plate were designed so as to avoid overheating and create a suitable indoor thermal environment for a hot-summer and cold-winter zone. The thermal performance of the facade system was tested under different conditions in typical summer and winter days. The novel solar facade system makes use of solar energy and a water supply to improve an indoor thermal environment with little temperature fluctuations. Compared with tests under stagnation conditions, the average temperature of indoor air was reduced by 8.9 °C under cooling conditions and increased by 8.0 °C under heating conditions. Validated by experimental results, theoretical calculations were performed to further optimize the system. Finally, the effect of parameters, such as outdoor climate, inlet water of the radiation plate, and main wall on the thermal performance, was assessed and the corresponding conditions to achieve a suitable indoor temperature were analyzed. This work is helpful for the energy-saving design of building-integrated solar thermal systems.

Triple function substation and high-efficiency micro booster heat pump for Ultra Low Temperature District Heating

District-Heating (DH) covers around the 9% of the total heat demand in the EU, with a proven highperformance levels and low operational costs. DH may suffer adaptations in order to maintain competitiveness with individual heating systems. The most important one is the reduction of supply temperatures up to 50°C, emerging the concept of Ultra Low Temperature (ULT) DH. ULT DH allows the transmission and distribution heat losses minimization, since heat losses are proportional to the temperature-gradient between supply line the ambient, increasing overall system performance. Furthermore, enables the integration of low-grade energy sources with low marginal costs, such as solar thermal energy or waste heat from industrial and commercial buildings. This study presents the combination of a novel 3 function-scheme (3FS) substation and a micro booster heat pump for domestic hot water. The novel design of the substation allows different operation modes between the grid and the building according to the temperature level and demand range every moment. Regarding the microbooster, this unit is used directly to lift the temperature of the domestic hot water (DHW), so that risk of legionella is avoided and that the required comfort temperature is reached. Preliminary test for the energy performance of the booster heat pump was measured on serially produced units according to tapping profiles and methodologies of standard EN16147. DHW coefficients of performance of 5.2 and 8.5 were measured for heat source supply temperatures respectively of 25 and 40 °C and return temperatures of 22 and 30 °C. This paper explores the possible operational modes of a 3FS in combination with a Building Integrated Solar Thermal System (BISTS) and a Microbooster heat pump.

A Roadmap for the Integration of Active Solar Systems into Buildings

This paper aims to simplify the interdisciplinary design process that will be used as a design tool for the viable integration of active solar energy systems into buildings, i.e., Building-Integrated Solar Thermal Systems—BISTSs; Building-Integrated Photovoltaic Systems—BIPVSs, through the creation of a roadmap. The research also aims supplement the work of researchers who have dealt with the creation of design tools that aim to optimise a specific aspect of a building design, or their geometric forms, in order to shape energy-efficient and sustainable architectural solutions. More specifically, a prescriptive design strategy is derived from the proposed design tool. This is based on five design steps, each of which is analysed and which lead to the creation of a comprehensive design tool for siting buildings so as to optimise the integration of solar systems. The originality of this tool is based on the fact that it makes an important step in the standardisation of these studies.

Building-integrated solar thermal system with/without phase change material: Life cycle assessment based on ReCiPe, USEtox and Ecological footprint

Abstract The present study assesses the environmental profile of a building-integrated solar thermal system that has been developed and tested in France. The investigation is based on life-cycle assessment according to ReCiPe, USEtox and Ecological footprint. Two configurations (for the solar collector) have been examined: 1) Without phase change material (using only rock wool as insulation) and 2) With phase change material (myristic acid) and rock wool. The main goal is the evaluation of the effect of the phase change material on the environmental profile of the solar thermal system. Both cases (with/without phase change material) have been studied based on the Mediterranean climatic conditions of Ajaccio (France). The results, according to ReCiPe midpoint (with characterization) demonstrate that the tubes (copper), the aluminium components (absorber, casing, gutter) and the phase change material are responsible for the highest impacts in terms of the material manufacturing phase of the collectors. With respect to ReCiPe/endpoint/single-score life-cycle results (scenarios: with/without PCM; with/without recycling; including the gutter), the values vary from 0.014 to 0.020 Pts/kWh. The configuration with phase change material presents 0.003 Pts/kWh higher impact (in comparison to the option without phase change material). Recycling offers an impact reduction of 0.003 Pts/kWh (for both configurations with/without phase change material). In addition, results according to USEtox (in terms of human toxicity and ecotoxicity) and Ecological footprint (with respect to the impact categories of carbon dioxide, nuclear and land occupation) are presented and discussed.

Cumulative energy demand and global warming potential of a building-integrated solar thermal system with/without phase change material

Building-integrated solar thermal (BIST) systems are a specific type of solar thermal systems which are integrated into the building and they participate in building functionality. The present article is about the life-cycle assessment of different options of a BIST system (Mediterranean climatic conditions: Ajaccio, France). The environmental profile of the studied configurations is assessed by means of CED (cumulative energy demand), GWP (global warming potential) and EPBT (energy payback time). The proposed configurations (for the collector) include: i) a system without PCM (phase change material) using only rock wool as insulation and ii) a system with PCM (myristic acid) and rock wool. Concerning life-cycle results based on CED and GWP 100a (scenario without recycling), the configuration without PCM shows 0.67 MJprim/kWh and 0.06 kg CO2.eq/kWh while the configuration with PCM presents 0.74 MJprim/kWh and 0.08 kg CO2.eq/kWh. Regarding EPBT, if the inputs for pumping/auxiliary heating are not taken into account, both configurations (with/without PCM) have almost the same EPBT (about 1.3 years). On the other hand, if the inputs for pumping/auxiliary heating are considered, EPBT is lower for the system with PCM. In addition, scenarios with recycling have been examined and the results demonstrate that recycling considerably improves the environmental profile of the studied configurations.

Progress in building-integrated solar thermal systems

Solar building envelopes are attracting increasing interest. Building-integrated solar thermal (BIST) systems are one of the subgroups of solar building envelopes. This paper summarizes the most important contributions of recent years and extends them. First, BIST elements are defined and available BIST elements are presented. Then, the general functions which BIST systems can provide are presented and the conflict between the constant U and g values of simple planning software and the variable g and U values of BIST elements is discussed. Measurements to characterize BIST elements are presented as well as a design parameter space in which the current BIST elements are located and which can be used when developing innovative new components. Methods to evaluate and compare BIST technologies are presented. The substantial cost savings which were achieved in three building projects between 2002 and 2009 are discussed. Roles within the building process are presented, as well as the general methods and challenges for economic BIST calculations and one economic calculation as an example. Based on existing building processes, a vision for future BIST building process integration is presented. Simple BIST models, which need no programming, are provided with easy-to-use equations. The challenges of standards and regulations are outlined and future research topics are presented. This paper summarizes important recent contributions to BIST research as a basis for future progress in building-integrated solar thermal systems. Instead of aiming to cover all recent BIST developments, the focus is on BIST research findings which are relevant for cost reduction of BIST components and therefore necessary for the economic success of BIST technology. These are discussed, together with proposals for future research.

Experimental verification of state space model and thermal performance analysis for active solar walls

Building-integrated solar thermal system is a new tendency in the building sector. An active solar wall is studied in this paper, which integrates flat plate solar thermal collector and building wall. The performance of an active solar wall is predicted by the state space model and measured by experimental testing respectively. The calculated results by state space model agree well with the measured data from experimental testing, which indicates that state space model is valid. Thermal analysis for a particular solar wall is conducted in clear and cloudy days either in summer or winter respectively by state space model under Shanghai meteorological conditions and compared with the separate wall. The results indicate that: (1) Integration has a little effect on the useful heat gains by solar collector. In clear summer days, the useful heat gains are less than the separate solar collector by about 2–3%; In clear winter days, the useful heat gain is greater than the separate solar collector by about 5–8%; (2) Integration has great effect on the heat flow through walls. In clear summer, heat flow into the room through solar wall is significantly reduced by 55–63% than the separate wall. It is favorable to reduce cooling load. In winter, heat loss through solar wall is heavily reduced by about 80–88% than the separate wall. It is favorable to reduce the space heating load in winter.

Solar Thermal Systems – Towards a Systematic Characterization of Building Integration

Characterization is defined as the act of describing distinctive characteristics or essential features. In most solar thermal collecting systems the energy performance characterization is commonly used as the most important criteria by which the system (or component) is represented. Building Integrated Solar Thermal Systems (BISTS) however are typically classified across a range of operating parameters, system features and mounting configurations, and other criteria are similarly important to be considered. Therefore BISTS characterization should also account for the architectural and building physics integration based on structural, functional and aesthetical features. A comprehensive characterization of BISTS is necessary to give designers, installers and end users confidence that the final solution selected is appropriate to the comprehensive building requirements.

Perspectives for solar thermal applications in Taiwan

Taiwan has long depended on imported fossil energy. The government is thus actively promoting the use of renewable energy. Since 2000, domestic installations of solar water heaters have increased substantially because of the long-term subsidies provided for such systems. However, data on the annual installation area of solar collectors in recent years indicated that the solar thermal industry in Taiwan has reached a bottleneck. The long-term policy providing subsidies must thus be revised. It is proposed that future thermal applications in Taiwan should focus on building-integrated solar thermal, photovoltaic/thermal, and industrial heating processes. Regarding building-integrated solar thermal systems, the current subsidy model can be continued (according to area of solar collectors); nevertheless, the application of photovoltaic/thermal and industrial heating systems must be determined according to the thermal output of such systems.

Simple models for building-integrated solar thermal systems

Building-integrated solar thermal systems (BIST) outperform building-added solar thermal systems (BAST) due to smaller heat losses at the back of the collector. BIST offer economic advantages, too. The insulation behind the collector can be used to reduce the heating demand of the building as well as to increase the solar thermal yield. Therefore, less material and labour are needed. Of course, the energy flux to the building interior needs to be considered. This energy flux depends in general on the operation of the collector as well as on the irradiance. Several innovative solar thermal building skins have been modelled in detail to analyze this coupling between the active building skin and the building. However, planners need an easy approach to include BIST into their calculations. Often, there is not enough budget to measure and model the new façade. This paper presents several new and simple models which are more accurate than neglecting the coupling to the building and which are less complex than detailed physical models.

Experimental study of a building-integrated dual-function solar collector system

As a novel building-integrated solar thermal system, a building-integrated dual-function solar collector system are designed with two operating modes: passive space heating mode in cold winter and water heating mode in warmer seasons. Based on a long-term experimental test, the paper investigates the performance of the system operating under these two modes. Experimental results indicated that the characteristic thermal efficiency of the system working at the water-heating mode with natural circulation was calculated to be 40.5% and at the space-heating mode the functional relationship between the temperature difference of the indoor air and the solar radiation on the absorber plate of the solar collector can be expressed as two linear equations.

Sustainable Development for Solar Heating Systems in Taiwan

In response to the impact of the United Nations Framework Convention on Climate Change, developing and using renewable energy sources and technologies have become vital for managing energy supply and demand in Taiwan. The long-term subsidy programs (1986–1991, 2000–present) for solar water heaters (SWHs) launched by the Taiwanese government constitute the main driving force for market expansion. By the end of 2013, the cumulative area of installed solar collectors was 2.27 million m2. Approximately 0.3 million systems (or 1.545 million m2) are in operation. This corresponds to an annual collector yield of 0.92 TWh, which is equivalent to savings of 98.7 thousand tons of oil and 319 thousand tons of CO2,eq. The market-driven mechanism is associated with cost-to-benefit ratios, construction businesses, types of building architecture, degree of urbanization and household composition. The strong wind load of typhoons is another major concern. For sustaining the solar thermal industry in Taiwan, the dominant factor for disseminating SWHs in metropolitan areas involves developing building-integrated solar thermal systems. Alternative financial incentives are required for industrial heating processes in the commercial sector.

Building Integrated Solar Thermal (BIST) Technologies and Their Applications: A Review of Structural Design and Architectural Integration

Solar energy has enormous potential to meet the majority of present world energy demand by effective integration with local building components. One of the most promising technologies is building integrated solar thermal (BIST) technology. This paper presents a review of the available literature covering various types of BIST technologies and their applications in terms of structural design and architectural integration. The review covers detailed description of BIST systems using air, hydraulic (water/heat pipe/refrigerant) and phase changing materials (PCM) as the working medium. The fundamental structure of BIST and the various specific structures of available BIST in the literature are described. Design criteria and practical operation conditions of BIST systems are illustrated. The state of pilot projects is also fully depicted. Current barriers and future development opportunities are therefore concluded. Based on the thorough review, it is clear that BIST is very promising devices with considerable energy saving prospective and building integration feasibility. This review shall facilitate the development of solar driven service for buildings and help the corresponding saving in fossil fuel consumption and the reduction in carbon emission.

Life cycle analysis of a building-integrated solar thermal collector, based on embodied energy and embodied carbon methodologies

The present study is a life cycle analysis of a patented building-integrated solar thermal collector which was developed/experimentally tested at the University of Corsica, in France, with the concept “integration into gutters/no visual impact”. Three configurations (reference and two alternatives) are evaluated. The life-cycle impact assessment methodologies of embodied energy (EE)/embodied carbon (EC), two databases and multiple scenarios are adopted. The results reveal that the reference system can considerably improve its environmental performance by utilizing collectors connected in parallel. The Energy Payback Time of the reference system decreases to less than 2 years by parallel connection while it is around 0.5 years if recycling is also adopted. The EE of the systems is around 3GJprim/m2 and it is reduced to around 0.4–0.5GJprim/m2 by recycling. The EC of the configurations is approximately 0.16tCO2.eq/m2 without recycling and around 0.02–0.03tCO2.eq/m2 with recycling. CO2.eq emissions are strongly related with electricity mix. A reduction 28–96% in CO2.eq emissions of the systems is achieved by adopting configurations with “double collector surface/output”. Concerning indicator of sustainability, the system with parallel connection shows a value of 0.78. The findings of the present investigation could be utilized for the design of building-integrated solar thermal systems as well as for research purposes.

Modelling and validation of a building-integrated dual-function solar collector

A novel building-integrated solar thermal system known as building-integrated dual-function solar collector is proposed. The system has two independent operating modes: passive space heating mode and water heating mode, and it uses the following criteria to select the operating mode that during cold days such as winter days it works in passive space heating mode, but in warm seasons such as summer it works in the water heating mode. A testing system was established, and it performed in thermosiphon water heating mode for water heating. Two dynamic numerical models were, respectively, presented for the two operating modes of the testing system. The experimental data on the testing system were used to validate the two models. The results show that the numerical model for the system in the thermosiphon water heating mode can give a fairly good prediction and the model for the system in the space heating mode also gives a good prediction.

Thermal characteristics of a building-integrated dual-function solar collector in water heating mode with natural circulation

As a modified building-integrated solar thermal system, building-integrated dual-function solar collector here proposed is able to provide passive space heating in cold winter, and water heating in warm seasons. In this study, evaluations were made on this modified collector system for the warm period operation under the water heating mode with natural circulation of flow. A dynamic numerical model has been developed and validated by experimental data. Based on practical air-conditioned room design conditions, numerical analysis was performed to study the water heating performance, as well as to compare the solar transmission through building facade in different seasons with or without its presence. The results show that when working in the water heating mode, the system performs well in providing services hot water in the warm seasons without bringing in summer overheating problem.

Towards an improved architectural quality of building integrated solar thermal systems (BIST)

Architectural integration is a major issue in the development and spreading of solar thermal technologies. Yet the architectural quality of most existing building integrated solar thermal systems (BIST) is quite poor, which often discourages potential new users. In this paper, the results of a large web survey on architectural quality, addressed to more than 170 European architects and other building professionals are presented and commented. Integration criteria and design guidelines established and confirmed through the analysis of these results are proposed. Subsequently, a novel methodology to design future solar thermal collectors systems suited to building integration is described, showing a new range of design possibilities. The methodology focuses on the essential teamwork between architects and engineers to ensure both energy efficiency and architectural integrability, while playing with the formal characteristics of the collectors ( size, shape, colour, etc.). Finally a practical example of such a design process conducted within the European project SOLABS is given; the resulting collector is described, and integration simulations are presented.