• Energy Research

The goal of this study is to examine various energy resources in district energy (DE) systems and then DE system performance development by means of multiple thermal energy storages (TES) application. This study sheds light on areas not yet investigated precisely in detail. Throughout the research, major components of the heat plant, energy suppliers of the DE systems, and TES characteristics are separately examined; integration of various configurations of the multiple TESs in the DE system is then analysed. In the first part of the study, various sources of energy are compared, in a consistent manner, financially and environmentally. The TES performance is then assessed from various aspects. Then, TES(s) and DE systems with several sources of energy are integrated, and are investigated as a heat process centre. The most efficient configurations of the multiple TESs integrated with the DE system are investigated. Some of the findings of this study are applied on an actual DE system. The outcomes of this study provide insight for researchers and engineers who work in this field, as well as policy makers and project managers who are decision-makers. The accomplishments of the study are original developments TESs and DE systems. As an original development the Enviro-Economic Function, to balance the economic and environmental aspects of energy resources technologies in DE systems, is developed; various configurations of multiple TESs, including series, parallel, and general grid, are developed. The developed related functions are discharge temperature and energy of the TES, and energy and exergy efficiencies of the TES. The TES charging and discharging behavior of TES instantaneously is also investigated to obtain the charging temperature, the maximum charging temperature, the charging energy flow, maximum heat flow capacity, the discharging temperature, the minimum charging temperature, the discharging energy flow, the maximum heat flow capacity, and performance cycle time functions of the TES. Expanding to ...

The thermal energy storage (TES) system is one of the most innovative technologies available for meeting long-term energy demands. Energy storage technology has demonstrated its ability to close the energy gap between supply and demand. The storage of thermal energy (TES) building integration is expected to reduce energy demand shortages while also allowing for better energy management in the construction industry. This paper will review about recent advancements in thermal energy storage which is in mini-review. There is some point that is highlighted in the review. There is sensible heat storage, latent heat storage and thermal chemical storage and the advantage of thermal energy storage. In this review paper, recent advancement has been studied and discussed, most commercial thermal energy storage was the sensible heat storage which is most cheap and most ready to use in recent technology. While future research is needed for giving confidence to the audience to use their system, which latent heat storage and thermochemical storage provide high energy capacity and high temperature for storing effect. These technologies were come in to track which has the advantage of their effectiveness.

The use of concrete is showing great potential as thermal energy storage material for concentrating solar power plants (CSP) due to its versatility, relatively low cost, and the possibility to reach a high operating temperature, above 500ºC thus increasing the plant efficiency. However, actual configurations based on concrete show different drawbacks including difficulties during the manufacturing on-site, different thermal expansion coefficients between concrete and pipes, and poor thermal conductivity of concrete. In order to address those challenges, this study proposes a new TES concrete tank concept based on three main pillars: modularity, improved concrete formulation, and direct contact concept. A preliminary assessment of the thermal performances of the new concept was analyzed through simulations showing the temperature distribution of the modules. Unión Europea 789051 “NextGenerationEU”/PRTR Ministerio de Ciencia e Innovación RTI2018-093849-B-C31 - MCIU/AEI/FEDER, Ministerio de Ciencia, Innovación y Universidades RED2018-102431-T- MCIU/AEI Ministerio de Ciencia, Innovación y Universidades MCIN/AEI/10.13039/501100011033

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The article discusses the relevance of the use of autonomous geothermal heating in areas of high constraint, dense buildings in large industrialurban areas. The types of low-temperature heat sources and non-traditional renewable energy sources are analyzed. The most common ground collectors are outlined and shown, and the methods of using geothermal heating in load-bearing building structures are shown

Ceramic-based packed bed solutions are becoming more common in the energy fields as both thermal energy storage and heat exchanger. Such solutions are usually designed for the working temperature ranges above600 ◦C, thus thermal radiation becomes significant and even acts as the dominant heat transfer mechanism. Therefore, applying high-temperature coatings with different thermal properties could be an efficient way in enhancing the performance of these applications. In this work, the high-temperature long residency and cyclic thermal stability of six inorganic coatings applied on a ceramic substrate are investigated. Both qualitative and quantitative assessments are performed. The results show that HIE-Coat 840MX and Pyropaint 634 ZO exhibit excellent thermal stability performance both at high-temperature testing (1000 ◦C) and under thermal cycle testing (400 ◦C–800 ◦C). TiO2 based coatings could be a viable solution if the powder is pre-treated to avoid polymorph transition during the operation. Stainless steel 304 powder-based coating could also be a possible solution, since the adhesive curbs the oxidation and hinders the coating from deterioration. Contrarily, Pyromark2500 and MgO-based coating show different degradation problems that limit their exploitation in high-temperature applications undergoing thermal cycles. The investigated coatings show a wide range of thermal emissivity (between 0.6 and 0.9), with stable or decreasing trends with temperature. This enables a potential20% change of the effective thermal conductivity for the packing structure. This work is a stepping-stone towards further detailed experimental studies on the influence of coatings on various packed bed thermal storage systems, and thus offer a new option in improving the performances of the energy equipment with packed bed systems. QC 20220502

Tässä raportissa esitetään yhteenveto "Rakennusten energiankäytön tutkimusohjelmaan RAKET" kuuluvan projektin "Innovatiivisten vaipparakenteiden kehitys" tuloksista, jotka koskevat rakenteiden lämpöhäviöiden pienentämiseen ja kosteusteknisen toiminnan parantamiseen sekä aurinkoenergian hyödyntämiseen tähtääviä keinoja. Tavoitteena oli tuottaa uusiin oivalluksiin perustuvia rakenneratkaisuja ja -periaatteita vähän lämmitysenergiaa kuluttaviin rakennuksiin. Lämpöhäviön pienentämiseen tähtäävät ratkaisut perustuvat tavanomaisiin mineraalivilla- ja solumuovieristeisiin, pitkäaaltoisen lämpösäteilyn sulkuna toimiviin pieniemissiviteettipintaisiin kalvoihin sekä rakennuspapereihin, joilla on halutut ominaisuudet. Aurinkoenergiaa hyödyntävänä ratkaisuna tutkittiin valoa läpäisevään lämmöneristeeseen sekä lasirakenteisiin perustuvaa kerääjää, luonnollisen konvektion ilmakiertoa ja massavaraajaa järjestelmänä. Ulkoseinän paksu kevyt mineraalivillaeristys sisältää käytännössä aina vähäisiä epäideaalisuuksia, jotka lisäävät reaalisen lämmöneristyksen konvektiivisuutta verrattuna ideaalieristykseen. Lämmöneristyksen paksuntaminen lisää epäideaalisuuksien ja konvektion haittaa. Esim. 300 mm:n eristyspaksuudesta voidaan pakkasella menettää tehollisesti 50 mm eristyksen sisäisen luonnollisen konvektion seurauksena. Lisäksi rakenteen sisäinen kosteus jakautuu epätasaisesti lisäten home- ja lahoriskiä. Eristyksen osastointi ilmanpitävillä, vesihöyryä diffuusisesti läpäisevillä pystysuuntaisilla konvektiokatkoilla eliminoi tehokkaasti paksun reaalieristyksen konvektiivisuuden. Kevyessä mineraalivillaeristeessä tapahtuva pitkäaaltoinen lämpösäteily (IR-säteily) muodostaa merkittävän osan eristyksen kokonaislämmönsiirrosta. IR-säteilyä heijastavien kalvojen käyttö suoraan mineraalivillaeristettä vasten vähentää säteilyyn perustuvaa lämpövirtaa vain ohuessa kalvoon rajoittuvassa eristekerroksessa. Kauempana eristeessä säteily tapahtuu kalvosta riippumatta kuitujen välillä. Säteilyn merkittävään vähentämiseen päästään vain pieniemissiviteettipintaisilla kuiduilla tai IR-säteilyn suhteen erittäin läpinäkyvillä kuiduilla sekä pieniemissiviteettipintaisilla kalvoilla eristyksen pinnoissa. Pelkästään pieniemissiviteettipintaisiin kalvoihin ja ilmaväleihin perustuvia lämmöneristysrakenteita analysoitiin laskennallisesti ja kokeellisesti. Kalvot toimivat sekä säteilylämmönsiirron estäjänä että konvektiokatkoina. Pystysuorissa rakenteissa, joissa ilmavälin paksuus on 20...30 mm ja joissa toinen ilmaväliin rajoittuvista pinnoista on emissiviteetiltään pieni (epsilon >/= 0,05), oli rakenteen näennäinen tehollinen lämmönjohtavuus luokkaa 0,03 W/(m * K). Vaakasuorissa eristyksissä, joissa lämpö siirtyy alaspäin, päästiin samaan ilmavälin paksuuden ollessa suuruusluokkaa 50 mm. Paksuudeltaan erilaisten vaaka- ja pystysuuntaisten koerakenteiden mitatut lämmönläpäisykertoimet olivat alueella 0,14...0,17 W/(m2 * K). Käytännön sovelluksena tutkittiin paksu kevyellä mineraalivillalla eristetty seinärakenne, jossa sisäverhouksen ja höyrynsulun välissä oli 30 mm:n ilmaväli. Höyrynsulkuna mineraalivilla sisäpinnassa oli paperiin laminoitu alumiinifolio kirkas pinta ilmaväliin päin. Saavutetut edut olivat: 30 mm:n ilmaväli toimii rakenteessa ylimääräisenä lämmöneristyskerroksena ja asennustilana, höyrynsulku säilyy ehjänä ja toimii tehokkaasti ilmansulkuna sekä samalla diffuusiotiiviinä ainekerroksena. Toisena sovelluksena tutkittiin pieniemissiviteettipintaisen kalvon vaikutus, kun kalvo asennettiin ryömintätilaisen alapohjan alle n. 50 mm sen alapinnasta alaspäin. Tavoitteena oli nostaa alapohjan alapinnan lämpötilaa ja parantaa kosteusoloja sekä alapohjan lämmöneristystä. Sekä laskelmat että kokeet osoittivat, että alapohjan alapinnan lämpötila nousi kalvon vaikutuksesta useita asteita, jolloin suhteellinen kosteus välittömästi alapohjan alla aleni n. 90 %:sta n. 65 %:iin. Vastaavasti jatkuvuustilan lämpötilaero ja samalla lämpövirta alapohjan läpi pieneni n. 40 % verrattuna kalvottomaan tilanteeseen. Laboratoriokokein tutkittiin yläpinnaltaan kallistetulla paksulla EPS-solumuovi-kerroksella eristetyn tuulettumattoman tasakaton kuivattamista kapillaarisesti johtavan viemäröintikerroksen avulla. EPS-eristyksen ja höyrynsulun väliin asetettu kapillaarisesti johtava yhtenäinen kuitukerros siirsi koekatossa n. 6 m:n etäisyydelle räystäästä asetetun vuotoveden räystäsreunalle, josta se poistui ulkopuolelle aluksi tippumalla ja myöhemmin haihtumalla kapillaarisen kerroksen reunasta. Veden poistuminen katosta alkoi n. vuorokauden kuluttua vesivuodosta ja pääosa kattoon asetetusta vedestä oli poistunut 21 vrk:n aikana. Jäännöskosteus katossa oli kokeen päättyessä 0,5...0,7 kg/m2. Rakenteisiin integroitu, luonnolliseen, omavoimaiseen ilmankiertoon perustuva aurinkoenergian kerääjäjärjestelmä osoittautui lupaavaksi ratkaisuksi. Järjestelmässä kerääjä- ja varaajarakenteet olivat erillään toisistaan, mutta yhteydessä suljetun ilmakanavan avulla. Valoaläpäisevään lämmöneristeeseen tai lasirakenteeseen perustuvassa kerääjässä lämpenevä ilma kulkee rakennuksen sisällä olevaan varaajaan. Aktiivisen järjestelmän etuna on pieni kerääjäseinän U-arvo ja varaajan lämpöhäviöiden tuleminen ympäröivien tilojen hyödyksi. Järjestelmä pystyi siirtämään ilmakierrolla yli 40 % kerääjän ulkopintaan tulleesta auringon säteilyenergiasta rakennuksen sisempiin osiin. Avoin ilmakierto huonetilaan antoi paremman hyötysuhteen, mutta käytännön ongelmina ovat kanaviston likaantuminen ja suuret hetkelliset lämpökuormat. Suljetussa ilmakiertokanavistossa lämpö siirtyi suurelta osin kanavistoon ja 3 m etäisyydellä kerääjästä olevaan kevytbetoniseen varaajaseinään saatiin vain 25 - 30 % koko konvektiolla siirretystä energiasta. Kehitystyön jatkona tulee olemaan samaan rakenteeseen integroitu järjestelmä.

The increasing use of concrete as a material propelled by the recent advancements in concrete technology is facing the prospect of its massive growth in the building sector worldwide. In addition to its positive structural characteristics, concrete has an inherent thermal mass feature that is known to save heating and cooling energies. However, such benefits need to be quantified so these benefits can be augmented and exploited. Concrete is also known to provide thermal comfort in a building, a prospect that can be related to its thermal mass property. While some studies have separately explored the effect of thermal mass’s thickness or surface area on building energy and thermal performance in a limited way, only a few have focused on both factors in the same study in detail and for that matter their combined effects, and even fewer have taken into account the distribution of thermal mass in a building. With an integrated approach, this present research has aimed for addressing all three variables: the thickness and distribution of concrete thermal mass in the building envelope; the distribution of thermal mass in a building’s configuration; and their effectiveness in reducing building energy consumption in office buildings and in improving its thermal comfort. The research methodology mainly focused on the quantitative methods with the use of building energy simulation tools including eQUEST, Design Builder, Energy Plus, and Atherna Impact programs. The Department of Energy (DOE) benchmark office building was considered as reference building model and the architectural design variables, including wall thicknesses and exterior thermal amass area, were selected to represent primary thermal mass. The slab thickness and interior wall layouts were selected to represent the secondary thermal mass. The eight climatic conditions of 1A (very hot and humid); 2B (hot and dry); 3C (warm and marine); 4B (mixed-dry); 5A (cool and humid); 6A (cool and marine); 7 (cold and dry); and 8 (very cold) will be assumed as representatives of all 16 U.S. climate zones. Lastly, life cycle assessment (LCA) and life cycle cost (LCC) analyses were conducted for a selected number of case models. This study has indicated that the primary thermal mass elements such as wall thickness and thermal mass area have more effects on building energy and thermal comfort performance compared to secondary thermal mass elements such as slab thickness and interior walls. Therefore, the main thermal mass-related design emphasis needs to be on its implementation in the building envelope. Energy efficiency and thermal comfort are generally conflicting criteria in building design in that the more the energy is saved, the less is the thermal comfort. Therefore, a design challenge is to determine the optimal combination of energy saving and thermal comfort. In terms of the optimization of energy usage and thermal comfort, this research shows that better energy performing thermal mass scenarios also have better thermal comfort performance. The utilization of thermal insulation along with a primary thermal mass, i.e., wall thickness, can also enhance the energy saving effects of thermal mass. In terms of LCA, an increase in wall thickness, for example, has relatively improved the environmental impacts of the building and has helped reduce the cost of building operation in its life cycle. For future research, the effects of design form and building height on the effectiveness of thermal mass in improving building energy and thermal comfort performance can be studied. Furthermore, different types of perimeter wall assemblies and glazing, especially with low-e coating can be combined with thermal mass to study the benefit from other energy saving recommendations in conjunction with thermal mass. In terms LCC, for instance, besides the cost of concrete materials, assembly, maintenance and demolition costs associated with concrete should be determined to assess the actual benefits of thermal mass in comparison with its additional costs.

Thesis (MEng)--Stellenbosch University, 2019. ; ENGLISH ABSTRACT: The rapid increase in demand for solar energy and its contribution to the national grid has placed new emphasis on the performance of Concentrating Solar Power (CSP) Plant. Plant performance can be enhanced by using once-through watercooling instead of the conventional direct air-cooled systems. Water withdrawn from the Orange River for agricultural irrigation purposes near Upington, in the Northern Cape can accommodate once-through cooling. To achieve this, a detailed study of CSP plant and different types of the cooling systems that are available was undertaken. The different types of CSP plant were evaluated and the best CSP plant based on the technology advancement was identified. The use and management of the irrigation system, government policies and environmental legislation along the lower Orange River was studied to look for synergy between CSP and agricultural water use. Once-through cooling for CSP plant that is also known as open-cycle cooling was modelled and fully analysed. The components of the CSP plant were also modelled, with emphasis on condenser fouling. This includes heliostat field, receiver tower, thermal storage, steam generator and power block. The heliostat field model determined the heliostat field optical efficiency over the year. The power block model determined the thermal efficiency of CSP plant and the function of growth with the cooling water temperature in the cooling system. The model was also used to determine the impact of changing different CSP plant operating parameters on the cooling system and evaluate the plant output. All existing CSP plants, except Bokpoort, make use of direct air-cooled condensers. Hence, direct air-cooling was adopted as benchmark for this study. Compared to a direct air-cooled CSP plant, once-through cooling shows that there is an improvement in the thermal efficiency of 2.9 percentage points. The model is based on hourly fluctuations in cooling water temperature from the river that ...