St1 Deep Heat Project : Geothermal energy to the district heating network in Espoo

Publisher Copyright: © Published under licence by IOP Publishing Ltd.St1 Deep Heat Project with its two deep wells extending to 6.2 - 6.4 km depth is the world's deepest industrial geothermal energy project. The aim is to build an EGS (enhanced geothermal system) at the depth of about 5 - 6 km. The project is a pilot aiming at exploring the technical and economic feasibility of geothermal energy in the crystalline rock conditions of Finland for production of thermal power to a district heating network. Due to the demands of the district heating, the aim is to produce hot fluid at about 100°C and re-inject it to the formation at 50°C. The 100°C goal requires to drill to about 6 km depth. The drill site is located in Espoo, next to the Fortum district heating plant on the Aalto University campus. So far (2020) the project has drilled a 2 km deep completely cored pilot hole (OTN-1), and two deep wells OTN-2 to 6.2 km and OTN-3 to 6.4 km. Hydraulic conductivity has been enhanced by hydraulic stimulation in both deep wells in 2018 and 2020. The extreme depth level sets significant challenges for drilling and hydraulic stimulation, as well as controlling of induced seismicity. At present, the project proceeds with the installation of production pumps in OTN-2 and OTN-3, and first test cross-hole pumpings are expected to start in January 2021. In the presentation we provide an insight to the project and its major achievements and challenges.Peer reviewe

Heat flow, seismic cutoff depth and thermal modeling of the Fennoscandian Shield

Being far from plate boundaries but covered with seismograph networks, the Fennoscandian Shield features an ideal test laboratory for studies of intraplate seismicity. For this purpose, this study applies 4190 earthquake events from years 2000–2015 with magnitudes ranging from 0.10 to 5.22 in Finnish and Swedish national catalogues. In addition, 223 heat flow determinations from both countries and their immediate vicinity were used to analyze the potential correlation of earthquake focal depths and the spatially interpolated heat flow field. Separate subset analyses were performed for five areas of notable seismic activity: the southern Gulf of Bothnia coast of Sweden (area 1), the northern Gulf of Bothnia coast of Sweden (area 2), the Swedish Norrbotten and western Finnish Lapland (area 3), the Kuusamo region of Finland (area 4) and the southernmost Sweden (area 5). In total, our subsets incorporated 3619 earthquake events. No obvious relation of heat flow and focal depth exists, implying that variations of heat flow are primarily caused by shallow lying heat producing units instead of deeper sources. This allows for construction of generic geotherms for the range of representative palaeoclimatically corrected (steady-state) surface heat flow values (40–60 mWm−2). The one-dimensional geotherms constructed for a three-layer crust and lithospheric upper mantle are based on mantle heat flow constrained with the aid of mantle xenolith thermobarometry (9–15 mWm−2), upper crustal heat production values (3.3–1.1 μWm−3), and the brittle-ductile transition temperature (350 °C) assigned to the cutoff depth of seismicity (28 ± 4 km). For the middle and lower crust heat production values of 0.6 and 0.2 μWm−3 were assigned, respectively. The models suggest a Moho temperature range of 460 to 500 °C.Being far from plate boundaries but covered with seismograph networks, the Fennoscandian Shield features an ideal test laboratory for studies of intraplate seismicity. For this purpose, this study applies 4190 earthquake events from years 2000–2015 with magnitudes ranging from 0.10 to 5.22 in Finnish and Swedish national catalogues. In addition, 223 heat flow determinations from both countries and their immediate vicinity were used to analyse the potential correlation of earthquake focal depths and the spatially interpolated heat flow field. Separate subset analyses were performed for five areas of notable seismic activity: the southern Gulf of Bothnia coast of Sweden (area 1), the northern Gulf of Bothnia coast of Sweden (area 2), the Swedish Norrbotten and western Finnish Lapland (area 3), the Kuusamo region of Finland (area 4) and the southernmost Sweden (area 5). In total, our subsets incorporated 3619 earthquake events. No obvious relation of heat flow and focal depth exists, implying that variations of heat flow are primarily caused by shallow lying heat producing units instead of deeper sources. This allows for construction of generic geotherms for the range of representative palaeoclimatically corrected (steady-state) surface heat flow values (40–60 mW m−2). The 1-D geotherms constructed for a three-layer crust and lithospheric upper mantle are based on mantle heat flow constrained with the aid of mantle xenolith thermobarometry (9–15 mW m−2), upper crustal heat production values (3.3–1.1 μWm−3) and the brittle-ductile transition temperature (350 °C) assigned to the cut-off depth of seismicity (28 ± 4 km). For the middle and lower crust heat production values of 0.6 and 0.2 μWm−3 were assigned, respectively. The models suggest a Moho temperature range of 460–500 °C.Peer reviewe

Physical properties of 368 meteorites: Implications for meteorite magnetism and planetary geophysics

Petrophysical studies (susceptibility, intensity of natural remanent magnetisation (NRM) and dry bulk density) of 368 meteorites are reviewed together with magnetic hysteresis data for 50 achondrites and chondrites. The relationships between dry bulk density, metallic FeNi-content and porosity will be discussed in the case of L-chondrites. Using the petrophysical classification scheme the meteorite class and the petrologic group of a sample can be determined in most of the cases providing a rapid means for determining a preliminary classification of a new sample. In addition, the petrophysical database provides a direct source of basic physical properties of the small bodies in the solar system. Paleointensity determinations with Thellier technique will be presented for 16 meteorites representing different chondrite groups. The results yield high paleofield values ranging from 51μT to 728μT for the magnetically hardest meteorites consistent with previous studies. However, these values must be looked with caution, because of possible physico-chemical or mineralogical alterations during heating

Thermal and porosity properties of meteorites : A compilation of published data and new measurements

We report direct measurements of thermal diffusivity and conductivity at room temperature for 38 meteorite samples of 36 different meteorites including mostly chondrites, and thus almost triple the number of meteorites for which thermal conductivity is directly measured. Additionally, we measured porosity for 34 of these samples. Thermal properties were measured using an optical infrared scanning method on samples of cm-sizes with a flat, sawn surface. A database compiled from our measurements and literature data suggests that thermal diffusivities and conductivities at room temperature vary largely among samples even of the same petrologic and chemical type and overlap among, for example, different ordinary chondrite classes. Measured conductivities of ordinary chondrites vary from 0.4 to 5.1 W m(-1) K-1. On average, enstatite chondrites show much higher values (2.33-5.51 W m(-1) K-1) and carbonaceous chondrites lower values (0.5-2.55 W m(-1) K-1). Mineral composition (silicates versus iron-nickel) and porosity control conductivity. Porosity shows (linear) negative correlation with conductivity. Variable conductivity is attributed to heterogeneity in mineral composition and porosity by intra- and intergranular voids and cracks, which are important in the scale of typical meteorite samples. The effect of porosity may be even more significant for thermal properties than that of the metal content in chondrites.Peer reviewe

Glasiomariiniset kerrostumissysteemit

Tiivistelmä. Glasiomariiniset kerrostumissysteemit tarkoittavat ympäristöjä, joissa jään reuna päättyy mereen, ja joissa muodostuu geneettisesti yhtenäisiä litofasieskokonaisuuksia. Ympäristössä tapahtuu glasiaalivaikutteisia prosesseja, joiden tuloksena syntyy kerrostumia. Kerrostumissysteemit voidaan jakaa jääproksimaaliasemaan, joka sijaitsee lähellä jäätikön reunaa, ja jäädistaaliasemaan, joka sijaitsee kauempana jäätiköstä. Kerrostumissysteemien vaikutus ulottuu laajalti mannerreunuksen ympäristöön ja jopa meren abyssaalisille tasangoille asti. Kerrostumasukkessioiden muodostumiseen ja sedimenttisaantoon vaikuttavat merkittävästi alueelliset ilmasto-olosuhteet. Glasiaalivaikutteisissa altaissa tapahtuvien merenpinnanvaihteluiden ja jäätikön aseman muutosten vuoksi merelliset allasrakenteet kokevat muutoksia. Muutokset voivat olla eustaattisia eli jäätikön kokoon liittyviä muutoksia, tai glasioisostaattisia eli jään painaman maan kuoren palautumiseen liittyviä muutoksia. Muutokset vaikuttavat myös altaan energiatasoihin, jotka puolestaan vaikuttavat sedimentaatioprosessien tehokkuuteen. Jäätiköstä irtoavilla jäämassoilla on merkittävä ympäristöä ja merenpohjaa muovaava vaikutus etenkin korkeilla leveysasteilla. Glasiomariinisten prosessien ja kerrostumien sekä glasiaalisten sedimenttisukkessioiden tulkitseminen auttaa ymmärtämään aiempaa jäätiköitymishistoriaa ja menneitä ilmasto- ja paleoympäristöolosuhteita. Kerrostumisprosessien tulkinta on hankalaa, mutta glasiaalisedimentologinen tieto voi auttaa ratkaisemaan tulevaisuuden ympäristöongelmia laajenevilla urbaaneilla alueilla

Screened Interaction and Self-Energy in an Infinitesimally Polarized Electron Gas via the Kukkonen-Overhauser Method

The screened electron-electron interaction $W_{\sigma, \sigma'}$ and the electron self-energy in an infinitesimally polarized electron gas are derived by extending the approach of Kukkonen and Overhauser. Various quantities in the expression for $W_{\sigma, \sigma'}$ are identified in terms of the relevant response functions of the electron gas. The self-energy is obtained from $W_{\sigma, \sigma'}$ by making use of the GW method which in this case represents a consistent approximation. Contact with previous calculations is made.Comment: 7 page

COST ES0602: towards a European network on chemical weather forecasting and information systems

The COST ES0602 action provides a forum for benchmarking approaches and practices in data exchange and multi-model capabilities for chemical weather forecasting and near real-time information services in Europe. The action includes approximately 30 participants from 19 countries, and its duration is from 2007 to 2011 (<a href="http://www.chemicalweather.eu/" target="_blank">http://www.chemicalweather.eu/</a>). Major efforts have been dedicated in other actions and projects to the development of infrastructures for data flow. We have therefore aimed for collaboration with ongoing actions towards developing near real-time exchange of input data for air quality forecasting. We have collected information on the operational air quality forecasting models on a regional and continental scale in a structured form, and inter-compared and evaluated the physical and chemical structure of these models. We have also constructed a European chemical weather forecasting portal that includes links to most of the available chemical weather forecasting systems in Europe. The collaboration also includes the examination of the case studies that have been organized within COST-728, in order to inter-compare and evaluate the models against experimental data. We have also constructed an operational model forecasting ensemble. Data from a representative set of regional background stations have been selected, and the operational forecasts for this set of sites will be inter-compared and evaluated. The Action has investigated, analysed and reviewed existing chemical weather information systems and services, and will provide recommendations on best practices concerning the presentation and dissemination of chemical weather information towards the public and decision makers

Resistivity, Hall effect and Shubnikov-de Haas oscillations in CeNiSn

The resistivity and Hall effect in CeNiSn are measured at temperatures down to 35 mK and in magnetic fields up to 20 T with the current applied along the {\it b} axis. The resistivity at zero field exhibits quadratic temperature dependence below $\sim$0.16 K with a huge coefficient of the $T^2$ term (54 $\mu$$\Omega$cm/K$^2$). The resistivity as a function of field shows an anomalous maximum and dip, the positions of which vary with field directions. Shubnikov-de Haas (SdH) oscillations with a frequency {\it F} of $\sim$100 T are observed for a wide range of field directions in the {\it ac} and {\it bc} planes, and the quasiparticle mass is determined to be $\sim$10-20 {\it m}$_e$. The carrier density is estimated to be $\sim10^{-3}$ electron/Ce. In a narrow range of field directions in the {\it ac} plane, where the magnetoresistance-dip anomaly manifests itself clearer than in other field directions, a higher-frequency ($F=300\sim400\text{T}$) SdH oscillation is found at high fields above the anomaly. This observation is discussed in terms of possible field-induced changes in the electronic structure.Comment: 15 pages, 5 figures, to appear in Phys. Rev. B (15 Sept. 2002 issue