Coupling of energy conversion systems and wellbore heat exchanger in a very deep oil well

The conventional geothermal power plants use the reinjection wells mostly to avoid the depletion of the geothermal reservoir gathering in the underground of the produced brine. Nevertheless, reinjection operations entail high economic costs and some risks. An alternative is the extraction of the heat without geothermal fluids production, the wellbore heat exchanger. The goal of the present paper is the analysis of the power production of the wellbore heat exchanger (WBHX) in time and the comparison between two different conversion systems of the thermal energy into electrical: the organic ranking cycle (ORC) plant and the Stirling motor. The selected case study is the oil field of Villafortuna Trecate, a medium enthalpy geothermal resource. The simulation results show a substantial decrease of the wellhead temperature in the first 6 months. After 1 year, the thermal power extracted with the WBHX is greater than 1.3 MW. The design parameters are 20 m3/h for the flow rate, outlet temperature 100.38 °C and the inlet temperature is 40 °C. The R-C318 has been selected as working fluid in the ORC plant: the net electrical power is 121 kW. The air is the working fluid in the Stirling motor: the evaluated net electrical power is 152 kW. The Stirling engine has an efficiency greater than 41 % compared to a system ORC

Light Concentrators for Borexino and CTF

Light concentrators for the solar neutrino experiment Borexino and the Counting Test Facility (CTF) have been developed and constructed. They increase the light yield of these detectors by a factor of 2.5 and 8.8, respectively. Technical challenges like long term stability in various media, high reflectivity and radiopurity have been addressed and the concepts to overcome these difficulties will be described. Gamma spectroscopy measurements of the concentrators show an upper limit of 12e-6 Bq/g for uranium and a value of 120e-6 Bq/g for thorium. Upper limits on other possible contaminations like 26Al are presented. The impact of these results on the performance of Borexino and the CTF are discussed and it is shown that the design goals of both experiments are fulfilled.Comment: submitted to Nuclear Instruments and Methods in Physics Researc

Solar and Reactor Neutrinos: Upcoming Experiments and Future Projects

Sub-MeV solar neutrino experiments and long-baseline reactor oscillation experiments toe the cutting edge of neutrino research. The upcoming experiments KamLAND and BOREXINO, currently in their startup and final construction phase respectively, will provide essential information on neutrino properties as well as on solar physics. Future projects, at present under development, will measure the primary solar neutrino fluxes via electron scattering and neutrino capture in real time. High precision data for lepton mixing as well as for stellar evolution theory will become available in the future. This paper aims to give an overview of the upcoming experiments and of the projects under development.Comment: 11 pages, 14 figures, LATEX (espcrc2.sty). Contribution to the proceedings of "TAUP2001 - Topics in Astroparticle and Underground Physics", LNGS, Italy (September 8-12, 2001

Summary and highlights

Energy means development, and access to energy and electricity should be possible for everyone. The energy challenge for the years to come is to have a sustainable energy supply and after the week spent in Varenna it is clear that "sustainable" cannot be identified with green gas emission reduction only: it has to be an energy supply system respectful of the environment and the humankind, able to provide reliable and affordable energy to the whole world population. This is definitely not an easy challenge: no single energy technology will suffice to safeguard our future and any possible solution has to be exploited at its best, from renewable to nuclear energy, from clean fossil fuels to biofuels. Last but not least, it is the energy efficiency that, given the actual technology, may give the most important and immediate contribution to this challenge. Meanwhile researchers must examine a broad range of options and develop different kinds of technologies: only new investments on R&D can allow to meet the growing demand for energy in a responsible, equitable, and sustainable way

Geoneutrinos in Borexino

This paper describes the Borexino detector and the high-radiopurity studies and tests that are integral part of the Borexino technology and development. The application of Borexino to the detection and studies of geoneutrinos is discussed.Comment: Conference: Neutrino Geophysics Honolulu, Hawaii December 14-16, 200

Maximal νe→νs\nu_e \to \nu_s solution to the solar neutrino problem: just-so, MSW or energy independent?

We examine the maximal $\nu_e \to \nu_s$ solution to the solar neutrino problem. This solution can be motivated by the exact parity model and other theories. The $\nu_e$ survival probability exhibits one of three qualitatively different behaviours depending on the value of $\Delta m^2$, viz. approximately energy independent, just-so or MSW. By the last of these we mean an enhanced night-time event rate due to regeneration in the Earth. We study all of these possibilities in the context of the recent SuperKamiokande data.Comment: minor changes to text and fig.

Time and position distributions in large volume spherical scintillation detectors

Large spherical scintillation detectors are playing an increasingly important role in experimental neutrino physics studies. From the instrumental point of view the primary signal response of these set-ups is constituted by the time and amplitude of the anode pulses delivered by each individual phototube following a particle interaction in the scintillator. In this work, under some approximate assumptions, we derive a number of analytical formulas able to give a fairly accurate description of the most important timing features of these detectors, intended to complement the more complete Monte Carlo studies normally used for a full modelling approach. The paper is completed with a mathematical description of the event position distributions which can be inferred, through some inference algorithm, starting from the primary time measures of the photomultiplier tubes.Comment: 29 pages, 20 figures, accepted for publication on Nucl. Instr. and Meth.

Optical properties of bialkali photocathodes

The optical properties of the `bialkali' KCsSb and RbCsSb photomultiplier cathodes have been experimentally investigated in the visible range. The measurements carried out include the absolute reflectance at near-normal incidence, the polarization-dependent relative reflectance at various angles and the change in polarization upon reflection from the photocathode. These experimental inputs have been combined with a theoretical model to determine the complex refractive index of the photocathodes in the wavelength range 380 to 680 nm and their thickness. As a result of this work, we derive a model which predicts the fraction of light impinging on a photomultiplier tube that is reflected, absorbed or transmitted, as a function of wavelength and angle, and dependent on the medium to which the photomultiplier is coupled.Comment: 51 pages (double spacing), 16 figures, submitted for publication in NIM