Jäähdytystornien mallintaminen ja lämmön talteenotto

The European Organization for Nuclear Research (CERN) has agreed on a commitment to minimize the environmental impact of the wide range of activities the Laboratory carries out. A key measure is waste heat recovery (WHR), as approximately 75 % of the power consumed in the electricity intensive particle accelerator complex, is dissipated to the sky as waste heat by cooling towers. A project for installing waste heat recovery to the cooling system of the Large Hadron Collider (LHC) at LHC point 8 has started and is expected to be operational in the beginning of 2020, after the second LHC long shutdown in 2018-2019. The operation of WHR causes a risk of temperature transients in case of unexpected WHR shutdowns. A dynamic simulation model of the cooling towers is needed to verify robustness against these temperature transients. In this Thesis, a thorough literature review of existing evaporative cooling tower modeling methods is performed, and the hybrid modeling method presented by Jin & al. (2007), is implemented to simulate the cooling towers at LHC point 8. The developed model is validated against real operational data. To the authors knowledge, this study is the first published use case of this evaporative cooling tower modeling method. A selection of anticipated sudden WHR shutdown scenarios are simulated in virtual commissioning environment with real programmable logic controller (PLC) to verify robustness of the cooling system against sudden temperature transients. A conclusion is that the cooling towers and their current control scheme is sufficient in dampening the anticipated temperature transients. This knowledge allows the WHR installation project to proceed.Euroopan hiukkasfysiikan tutktimuskeskuksella CERN:illä on tavoitteenaan minimoida laboration aktiviteettien ympäristövaikutukset. Tämän tavoitteen saavuttamisessa lämmön talteenotto (LTO) on tärkeässä roolissa, sillä energiaintensiivisessä hiukkaskiihdytinkompleksissa noin 75 prosenttia käytetystä sähkötehosta haihdutetaan taivaalle jäähdytystornien kautta hukkalämpönä. Toisen pitkän käyttökaton aikana vuosina 2019 - 2020 suuren hadronitörmäyttimen (LHC) pisteelle 8 asennetaan lämmön talteenottojärjestelmä. Lämmön talteenoton käyttö aiheuttaa riskin lämpötilavaihteluiden syntymiselle, jos hukkalämmön vastaanotto katkeaa äkillisesti. Dynaaminen jäähdytystornien simulaointimalli tarvitaan suuren hadronitörmäyttimen toiminnan kannalta kriittisen jäähdytysjärjestelmän luotettavuuden varmistamiseksi. Tässä diplomityössä esitellään kattava kirjallisuuskatsaus jäähdytystornien mallinusmenetelmistä ja implementoidaan Jin & al. (2007) julkaisema hybridi-menetelmä LHC pisteen 8 jäähdytystornien simuloimiseksi. Malli validoidaan järjestelmästä mitattua dataa vasten. Tehdyn kirjallisuusselvityksen perusteella tämä diplomityö on ensimmäinen julkaisu, jossa tätä jäähdystornien mallinusmenetelmää sovelletaan käytössä olevan järjestelmän simuloimiseen. Järjestelmän lämpötilatransienttien vaimmenuskyvyn tutkimiseksi jäähdytystornimallilla simuloidaan eri vuodenaikoina odetettavissa olevia lämmön talteenoton pysähtymisiä virtual commissioning -ympäristössä, jossa todellinen ohjelmoitava logiikka (Programmable Logic Controller PLC) ohjaa mallia. Simulointien tulokset osoittavat, että nykyinen jäähdytyskapasiteetti ja ohjauslogiikka vaimentavat odotettavissa olevia transientteja tehokkaasti. Tämän tiedon perusteella lämmön talteenottoprojekti voi edetä

Next stop: Isosaari – the new patterns of a military island

Helsingin eteläisen ulkosaariston laidalla sijaitseva 76-hehtaarinen Isosaari on jäänyt vuosisadan mittaisen sotilasaikakauden jälkeen tyhjilleen. Tämä diplomityö käsittelee saaren uudelleenkäyttömahdollisuuksia osana Helsingin saariston kokonaisvaltaista kehittämistä. Työn tavoitteena on tarjota vaihtoehtoja ja työkaluja saariston ja erityisesti Isosaaren kehittämiseen esimerkiksi saavutettavuuden, palvelutarjonnan ja vetovoimaisuuden kannalta. Työssä tutkitaan Isosaaren uudistamista väliaikaisen asumisen, työnteon ja virkistyskäytön tarkoituksiin yhteisöllisyyttä, omavaraisuutta ja luonnonläheisyyttä painottaen. Ensiksi käsitellään Helsingin saaristoa ja sen kehittämismahdollisuuksia, minkä jälkeen tarkennetaan Isosaareen ja sen lähtökohtiin. Sitten esitellään tekijän omat suunnittelutavoitteet, joita seuraa katsaus suunnittelussa huomioitaviin tulevaisuuden muutosilmiöihin ja elämänlaadun osatekijöihin. Seuraavaksi kartoitetaan Isosaaren potentiaali uudiskäyttöön kulttuurihistoriallisten ja luontoarvojen säilyttämisen ehdoilla. Analyysin pohjalta laaditaan strategia Isosaaren uudelleenkäytölle ja luodaan konseptisuunnitelma Isosaaresta kaikille avoimena virkistys- ja residenssisaarena sekä yhteisöllisenä hiilineutraaliuden pilottikohteena, jota voi tulevaisuudessa kehittää kohti ympärivuotisuutta ja vakituista kyläyhteisöä.Isosaari, a 76 hectare-sized island in the southern edge of Helsinki archipelago was in military use for a century and has recently been abandoned. This Master´s thesis processes potential patterns for the new use of the island as a part of developing the whole archipelago area of Helsinki. The objectives of this thesis are to provide options and tools for the development of Helsinki archipelago area and especially the Isosaari island in aspects of accessibility, service supply and attractiveness. The thesis examines the renewal of Isosaari for periodical living, working and recreational purposes emphasizing on collectiveness, self-sufficiency and the proximity of nature. The thesis begins with surveying the Helsinki archipelago and its development possibilities, after which it zooms in on Isosaari and in its premises. Next the author´s targets are presented followed by a review of the future trends and components of the quality of life, which are affecting the design process. The renewal potential of Isosaari is explored considering the preserving of cultural history and natural values in all the actions. The rejuvenating strategy for Isosaari is composed on the basis of the conditions analysis which leads to a conceptual vision of Isosaari as a hospitable place for recreation and residency for the city-dwellers and tourists as well as a communal, ecological and self-sufficient pilot site, which could be further developed towards year-round activities and permanent housing

Futures pricing in the Nordic electricity market

This master's thesis examines the behavior of electricity spot and futures prices and the futures premium in the Nordic electricity market. The objective of the study is to identify, whether a nonzero futures premium exists in the Nordic electricity market, and to gauge its economic significance and the factors affecting its behavior. Furthermore, the forecasting ability of electricity futures over the future spot price is examined, and finally the existence of arbitrage opportunities is tested by constructing synthetic futures and comparing their prices with actual futures prices. The data in this study consists of daily electricity spot prices in the Nord Pool power exchange for years 2000 - 2011, and electricity futures price data for weekly, monthly, quarterly and yearly contracts during the same period. The price data is complemented by coal price data and Nordic level data on water reservoir levels and electricity demand, which are the variables used to examine the behavior of electricity prices and the futures premium. The results show that the futures premium in the Nordic electricity market is nonzero and positive for the time period 2000 - 2011, generally increasing with contract maturity. The futures premium exhibits very high variation, but on average the relative futures premium ranges from being close to zero with weekly futures to levels above 20 percent for yearly futures. The OLS regression analyses show that deviations from historical water reservoir levels have an inverse relationship with electricity spot and futures prices so that above average water reservoir levels have a negative impact on electricity prices, and vice versa. Coal price and the overall electricity demand exhibit a positive relationship with electricity prices, and the influence of all these physical factors diminishes with the futures' time to maturity, being the strongest for shorter maturity futures and weak or inexistent for futures with longer maturities. On the contrary, deviations from historical water reservoir levels indicate a positive relationship with the futures premium, this relationship being negative for coal price and electricity demand. Furthermore, consistent with the expectations theory, electricity futures seem to possess strong explanatory power over the future spot price in the Nordic electricity market, whereas no evidence of time-varying risk premiums is found. Finally, the comparison of synthetic futures prices to actual futures prices reveals that with yearly futures the mean relative price difference is close to zero, indicating that no opportunities for arbitrage exist, but for quarterly and monthly futures the price difference is different from zero on average, reaching a maximum mean value of 2.0% for 1-month contracts. This indicates that opportunities for risk-free profits may exist for arbitrageurs using synthetic futures to mimic the actual futures contracts. These arbitrage opportunities continue to prevail when transaction costs are at levels below two percent of the futures price, although their economic significance is low

Membraneless energy conversion and storage using immiscible electrolyte solutions

peer-reviewedBreakthrough alternative technologies are urgently required to alleviate the critical need to decarbonise our energy supply. We showcase non-conventional approaches to battery and solar energy conversion and storage (ECS) system designs that harness key attributes of immiscible electrolyte solutions, especially the membraneless separation of redox active species and ability to electrify certain liquid–liquid interfaces. We critically evaluate the recent development of membraneless redox flow batteries based on biphasic systems, where one redox couple is confined to an immiscible ionic liquid or organic solvent phase, and the other couple to an aqueous phase. Common to all solar ECS devices are the abilities to harvest light, leading to photo-induced charge carrier separation, and separate the products of the photo-reaction, minimising recombination. We summarise recent progress towards achieving this accepted solar ECS design using immiscible electrolyte solutions in photo-ionic cells, to generate redox fuels, and biphasic “batch” water splitting, to generate solar fuels.ACCEPTEDpeer-reviewe

Electrocatalyst nanoparticles go with the flow

Electric current is now shown to induce movement of the atoms in electrocatalyst nanoparticles, leading to morphological changes and performance degradation. This electromigration effect needs to be taken into account when designing nanostructured catalysts for electrochemical devices.</p

Mediated water electrolysis in biphasic systems

peer-reviewedThe concept of efficient electrolysis by linking photoelectrochemical biphasic H2 evolution and water oxidation processes in the cathodic and anodic compartments of an H-cell, respectively, is introduced. Overpotentials at the cathode and anode are minimised by incorporating light-driven elements into both biphasic reactions. The concepts viability is demonstrated by electrochemical H2 production from water splitting utilising a polarised water-organic interface in the cathodic compartment of a prototype H-cell. At the cathode the reduction of decamethylferrocenium cations ([Cp2*Fe(III)]+) to neutral decamethylferrocene (Cp2*Fe(II)) in 1,2-dichloroethane (DCE) solvent takes place at the solid electrode/oil interface. This electron transfer process induces the ion transfer of a proton across the immiscible water/oil interface to maintain electroneutrality in the oil phase. The oil-solubilised proton immediately reacts with Cp2*Fe(II) to form the corresponding hydride species, [Cp2*Fe(IV)(H)]+. Subsequently, [Cp2*Fe(IV)(H)]+ spontaneously undergoes a chemical reaction in the oil phase to evolve hydrogen gas (H2) and regenerate [Cp2*Fe(III)]+, whereupon this catalytic Electrochemical, Chemical, Chemical (ECC’) cycle is repeated. During biphasic electrolysis, the stability and recyclability of the [Cp2*Fe(III)]+/Cp2*Fe(II) redox couple were confirmed by chronoamperometric measurements and, furthermore, the steady-state concentration of [Cp2*Fe(III)]+ monitored in situ by UV/vis spectroscopy. Post-biphasic electrolysis, the presence of H2 in the headspace of the cathodic compartment was established by sampling with gas chromatography. The rate of the biphasic hydrogen evolution reaction (HER) was enhanced by redox catalysis in the presence of floating catalytic molybdenum carbide (Mo2C) microparticles at the immiscible water/oil interface. The use of a superhydrophobic organic electrolyte salt was critical to ensure proton transfer from water to oil, and not anion transfer from oil to water, in order to maintain electroneutrality after electron transfer. The design, testing and successful optimisation of the operation of the biphasic electrolysis cell under dark conditions with Cp2*Fe(II) lays the foundation for the achievement of photo-induced biphasic water electrolysis at low overpotentials using another metallocene, decamethylrutheneocene (Cp2*Ru(II)). Critically, Cp2*Ru(II) may be recycled at a potential more positive than that of proton reduction in DCE

Gamma-aminobutyric acid-functionalized naphthalene diimide for aqueous organic flow batteries

An anionic gamma-aminobutyric acid-functionalized naphthalene diimide (GABA-NDI) was investigated for its possible application in flow batteries. A GABA-NDI/ferrocyanide flow battery was stable over 200 cycles and demonstrated an average coulombic efficiency of 99.96% and an excellent energy efficiency of 80.9% at 60 mA cm−2 while accessing 95% of the theoretical capacity of GABA-NDI. An increase in solubility and stability was achieved compared to previous studies. </p

Gold Raspberry-Like Colloidosomes Prepared at the Water-Nitromethane Interface

Here, we propose a simple shake-flask method to produce micron-size colloidosomes from a liquid-liquid interface functionalized with a gold nanoparticle film. A step-by-step extraction process of an organic phase partially miscible with water led to the formation of raspberry-like structures covered and protected by a gold nanofilm. The distinctive feature of the prepared colloidosomes is a very thin shell consisting of small gold nanoparticles of 12 or 38 nm in diameter instead of several hundred nanometers reported previously. The interesting and remarkable property of the proposed approach is its reversibility: the colloidosomes may be easily transformed back to a nanofilm-state simply by adding pure organic solvent. The obtained colloidosomes have a broadband absorbance spectrum, which makes them of great interest in such applications as photothermal therapy and Surface Enhanced Raman Spectroscopy studies as well as microreactor vesicles for interfacial electrocatalysis

Solvent effect in photo-ionic cells

Photo-ionic cells convert solar energy into redox fuels. Unlike in photovoltaic devices where the photo-induced charge transfer reactions occur at an electrode, the photoreaction takes place in one bulk solution of a biphasic liquid-liquid system, and the charge separation is realised by the transfer of one of the photoproducts into the adjacent phase to avoid recombination. After separation of the two phases, the redox fuels can be stored and then converted to electricity on demand with a biphasic fuel cell. Here, we compared the effect of the two organic solvents, 1,2-dichloroethane and propylene carbonate, on the performance of the photo-ionic cell. By replacing 1,2-dichloroethane, the maximum cell voltage was increased to 0.6 V. Additionally, propylene carbonate helps to reduce aggregation of dyes and it shows faster kinetics for the photoreaction