Solar thermal energy is a possible technology in order to increase the renewable share inside district heating as required by European Directive 2012/27. However, these systems represent an important investment and need to be appropriately sized and operated, mainly because of the intermittency of the solar energy, to deliver heat at reasonable cost while preventing any conflict of usage between various heat producers: Combined Heat and Power (CHP), biomass boiler, solar thermal energy, etc. Exergy analysis is a promising tool to tackle this issue. To progress in that direction, this paper presents a dynamic exergoeconomic analysis on an existing solar district heating (SDH) located in the North West of France in which conflict of usage occurs. The actual configuration is implemented in Dymola and includes a large-scale solar field, a biomass boiler, a gas boiler and a thermal energy storage. Based on models available in Modelica Buildings Library, an exergoeconomic approach (Specific Exergy Costing) is implemented. Field data from year 2019 are used as input to model the demand and solar data are taken from SoDa Service. Two cases are considered: one without the solar field (reference case), and one with the solar field. This study demonstrates that adding a solar field in an existing district heating system leads to a degradation from an exergy point of view. This degradation mainly occurs during the non-heating season, when the solar energy is the source of 26% of the overall exergy destruction. It is shown that with the solar field the specific cost of the heat increases by 10% during the non-heating season. The study highlights that adding a solar field reduces the operating time of the boilers and thus increases their investment cost rates. Moreover, the solar field is the main source of extra cost, which degrades the system for an exergoeconomic point of view.
A large amount of research has been conducted on the reuse of construction and demolition waste (CDW) in concrete. Yet, CDW may display pre-existing damage which raises concerns on its use. In this work, coarse recycled concrete aggregate (RCA) is reclaimed from distinct members of an alkali-silica reaction (ASR) affected overpass. RCA mixtures incorporating 50 and 100% replacement are then manufactured and stored in conditions enabling further ASR development. Mechanical (Stiffness Damage Test- SDT) and microscopic (Damage Rating Index- DRI) analyses are conducted at a fixed "secondary" induced expansion. Results indicate that the overall damage of ASR-affected RCA mixtures is different from conventional concrete and depends upon the "past" RCA condition. Furthermore, the DRI can capture the "past" and "secondary" expansion while the SDT simply detects the "secondary" distress. Finally, an adapted DRI version is proposed to better evaluate and distinguish "past" and "secondary" damage in ASR-affected recycled concrete.
Solar heating and cooling systems can significantly contribute to the energy and climate European goals. A complete assessment of this contribution needs the analysis of these systems from a life-cycle perspective, in order to estimate the energy and environmental costs of their manufacturing and end-of-life, and to compare these costs with the benefits obtained during operation. A well-established methodology to fulfil this task is the Life Cycle Assessment (LCA). The paper describes some LCA experiences of solar heating and cooling systems, developed within the Task 53 "New generation solar cooling & heating systems (PV or solar thermally driven systems)" of the International Energy Agency. The results of these analyses can be useful to orientate manufacturers, researchers and decision makers for a more sustainable use of solar technologies.
SOCOL is a collaborative platform gathering specialists, professionals and institutions operating within the solar thermal market in France. Dedicated to promoting multi-family and commercial solar thermal systems, SOCOL is fully representative of the industry. Operationally, SOCOL consists of working groups manned by solar thermal specialists, who regularly produce documents and other tools (such as software) and make them freely available online. For nine years, French experts working with SOCOL have been providing free access to technical and pedagogical tools, addressing ST experts and project-owners alike, targeting medium to large solar thermal installations in the residential sector. These tools now cover every step in solar thermal projects, from conception to daily maintenance, ensuring peace of mind for project-owners and performance in the long run for solar thermal systems.
