Interpretation of magnetic anomalies over the Waimangu geothermal area, Taupo volcanic zone, New Zealand

The study area is located on the eastern side of the Taupo volcanic zone in central North Island of New Zealand. It lies a few kilometres to the southwest of Mt Tarawera, the site of the biggest New Zealand volcanic eruption in historical times (the June 1886 Tarawera eruption). The study area includes the Waimangu geothermal field and a small part of Waiotapu and Waikite fields. The extensive surface thermal expressions (boiling springs, hot lakes, craters, and sinter terraces) occurring at the Waimangu field were all formed following the 1886 Tarawera eruption. Another large area of less intense thermal manifestations (thermal ground and hydrothermally altered rocks) exists about 5 km southwest of Waimangu, extending towards the Waiotapu field in the south. In 1993 an aeromagnetic survey was conducted over the study area at an average altitude of about 350 m above the ground. The results show a subdued negative residual anomaly (about −100 nT) over the Waimangu field, which can be interpreted by near-surface hydrothermal demagnetisation of rhyolitic host rocks. The lateral distribution of the demagnetised rocks is much greater than the thermal area of Waimangu, and is consistent with the extent of low resistivity rocks across the study area. The magnetic interpretation also shows that two-high standing dacite domes situated about 5 and 7 km to the southwest of Waimangu have been affected by hydrothermal demagnetisation. There are negative residual anomalies outside the low resistivity zone that could be associated with reversely magnetised rocks (age >0.78 Ma). A strong positive residual anomaly (up to 450 nT) occurs to the east of the Waimangu field. Results from 3-D magnetic interpretation indicate some alternative models for this positive anomaly: (1) southwest–northeast trending, vertical basalt dykes (magnetisation 10 A/m), tops between −0.1 and −0.65 km RL (reduced LEVEL=relative to sea level), (2) a thick ( 1 km) sequence of rhyolites (magnetisation 2.5 A/m) extending from the surface down to about −0.8 km RL, and (3) a rather thin (0.35 km) sequence of rhyolites (from surface to sea level) underlain by basalt bodies similar to those of model (1).     

Techno-economic analysis of MJ class high temperature Superconducting Magnetic Energy Storage (SMES) systems applied to renewable power grids

High temperature Superconducting Magnetic Energy Storage (SMES) systems can exchange energy with substantial renewable power grids in a small period of time with very high efficiency. Because of this distinctive feature, they store the abundant wind power when the power network is congested and release the energy back to the system when there is no congestion. However, considering the cost and lifespan of SMES systems, there is an urgent demand to conduct a cost-benefit analysis to justify its role in smart grid development. This study explores the application and performs economic analysis of a 5 MJ SMES in a practical renewable power system in China based on the PSCAD/ EMTDC software. An optimal location of SMES in Zhangbei wind farm is presented using real power transmission parameters. The stabilities of the renewable power grid with and without SMES are discussed. In addition, a financial feasibility study is conducted by comparing the cost and the savings from wind power curtailment of deploying SMES and battery. The economic analysis tries to find the balance between SMES investment cost and wind farm operation cost by using real data over a calendar year. The technical analysis can help guide the optimal allocation of SMES for compensating power system instability with substantial wind power. Further, the economic analysis provides a useful indication of its practical application feasibility to fight the balance between cost and benefit.     

Carbon Emissions Pinch Analysis (CEPA) for emissions reduction in the New Zealand electricity sector

Carbon Emissions Pinch Analysis (CEPA) is a recent extension of traditional thermal and mass pinch analysis to the area of emissions targeting and planning on a macro-scale (i.e. economy wide). This paper presents an extension to the current methodology that accounts for increased demand and a carbon pinch analysis of the New Zealand electricity industry while illustrating some of the issues with realising meaningful emissions reductions. The current large proportion of renewable generation (67% in 2007) complicates extensive reduction of carbon emissions from electricity generation. The largest growth in renewable generation is expected to come from geothermal generation followed by wind and hydro. A four fold increase in geothermal generation capacity is needed in addition to large amounts of new wind generation to reduce emissions to around 1990 levels and also meet projected demand. The expected expansion of geothermal generation in New Zealand raises issues of GHG emissions from the geothermal fields. The emissions factors between fields can vary by almost two orders of magnitude making predictions of total emissions highly site specific.     

Cost optimal deployment of mirrors associated with a high temperature solar energy system

An absorbing cavity or collector of solar energy is mounted on a tower which is assumed to be erected over horizontal terrain. Located about the base of the tower are many relatively small mirrors of predetermined size. The bases of the mirror mounts are rigidly attached to the ground. During daylight hours, each mirror is continuously positioned so that the specular component of incident sunlight is reflected into an aperture located in the base of the cavity. A sharp upper bound is found on the maximum energy that can be redirected into the aperture by an array of mirrors belonging to a certain family & (the class of locally uniform rectangular arrays) whose total surface area is not more than some preassigned value. The upper bound is obtained by building up an optimal mirror array in local blocks. Although these blocks may not combine to generate a realizable deployment, their properties should be of assistance in finding superior members of &. These results are combined with a simple cost model to obtain a lower bound on the minimum cost per unit of redirected energy as a function of the unit mirror cost.     

Thermal anomalies in lanzarote (Canary Islands)

About a hundred thermometers have been installed 3 m deep in an area of about 20 km² in the ? Montañas de Fuego ? (island of Lanzarote). The temperatures measured oscillate between 16°C and 350°C. In other wells 150 to 250 m deep a gradient of 0.2°C/m has been measured. This gradient is always found in a region of about 200 km² around the zones of the highest superficial anomalies.The local surface anomalies are related to the outflow of hot fluids through tectovolcanic fractures. At great depths these fluids probably form a convective system under impervious layers (hyaloclastites?). The heat transfer takes place by means of convection in a deep reservoir and in the superficial levels, but an intermediate zone with impervious layers must exist where heat is transmitted by conduction.     

Numerical modelling of production from the Poihipi dry steam zone: Wairakei geothermal system,New Zealand

The Poihipi power station utilizes dry steam from a shallow zone near the margin of the Wairakei geothermal reservoir. The station has been in operation for several years, with daily variations in the fluid production rate following variations in time-of-day pricing of electricity. The corresponding varying pressure history provides a good database for testing models of the geothermal reservoir.     

Fluid-rock interaction processes in the Te Kopia geothermal field (New Zealand) revealed by SEM-CL imaging

Scanning electron microscopy-cathodoluminescence (SEM-CL) imaging of hydrothermal quartz exposed by weathering in the Te Kopia geothermal field (New Zealand) has revealed a history of crystal growth, dissolution, overprinting and fracturing that cannot be detected using other observational techniques (e.g. transmitted or reflected light microscopy, back-scattered electron imaging or secondary electron imaging). The crystals initially grew as CL-dark quartz, at least 350 m below their present location on the Paeroa Fault scarp, in a neutral pH, 215±10 °C liquid reservoir (inferred from the analysis of primary liquid fluid inclusions: mean T_h of 213 °C; 0.2–0.4 wt.% NaCl_eq.). Relict quartz–adularia–illite alteration occurs at the surface, in the vicinity of the quartz crystals, and in drillcores from the nearby TK-1 exploration well. Repeated movement on the Paeroa Fault uplifted pyroclastic rocks hosting the quartz crystals, but also provided pathways for “pulses” of hot fluids to move through the system. Quartz precipitation occurred at the edge of the crystals as the reservoir fluids cooled, as indicated by micron-scale alternating CL-dark/CL-bright quartz growth bands, which contain fluid inclusions with T_h values of 210±40 °C. Pressure fluctuations were the likely cause of dissolution, marked by corroded crystal edges, with subsequent precipitation of quartz into open space. SEM-CL imaging shows that the quartz crystals contain healed fractures, which trapped low salinity fluids with T_h values of 201±6 °C. Low-pH fluids in the near-surface setting also rounded the quartz crystals, and coated them with kaolinite and CL-grey amorphous “silica residue”.     

地热+高温水源热泵区域供暖工程的环境影响分析

经过分析计算，对区域燃煤锅炉房供暖方式和地热＋高温水源热泵供暖方式对环境的影响做出比较．证明了地热＋高温水源热泵同燃煤锅炉供暖方式相比具有巨大的环境效益。     

Te Kopia geothermal system (New Zealand) — the relationship between its structure and extent

The Te Kopia geothermal system is one of several high-temperature systems in the Taupo Volcanic Zone (TVZ) of New Zealand. It is located along the Paeroa Fault Zone, a major active fault system trending NE in the central TVZ. Three independent studies, i.e. resistivity survey, magnetic interpretation, and detailed topographic analysis of faults and fractures, indicate the existence of another fault system, trending NW, that also significantly influences the Te Kopia geothermal system. Results from these studies also show that, at Te Kopia, a resistivity low and hydrothermally demagnetised rocks (both are indicators of a geothermal reservoir in volcanic rocks) clearly coincide with a zone of high fault and fracture density. Hence, the Te Kopia field is a good example of the significant influence that geological structures (major fault systems) have on the extent of a geothermal reservoir, by creating zones of fractured rocks that provide permeable paths for thermal fluids.     

Creep damage prediction of the steam pipelines with high temperature and high pressure

Creep is the significant factor that caused failure of steam pipelines with high temperature and high pressure in the period of long-term service. In this paper, the creep tests were performed at serviced temperature of 520 °C for 1.25Cr–0.5Mo pipe material, and the creep and fracture constants were obtained by fitting the creep test data. Based on the modified Karchanov–Rabotnov constitutive equation, compiled the user subroutine computing the damage of the pipe element or 3D solid element, the creep damage prediction was carried out by finite element methods using ABAQUS codes for the steam pipelines with high temperature and high pressure, which serviced in a petro-chemical plant, the damage distribution and maximum damage location of the pipelines were obtained, which is testified by metallographic examination result. Furthermore, the local creep damage analysis of a tapered pipe serviced for 100,000 h was also carried out because tapered pipes used in the main steam pipeline is one of weakness in the piping system. Damage distribution and evolution in the analyzed tapered pipe were obtained. The location with the maximum damage value was determined, which is coincident with cracking position of the actual tapered pipe.     

Numerical study of high temperature proton exchange membrane fuel cell (HT-PEMFC) with a focus on rib design

The rib size is a critical engineering design parameter for high temperature proton exchange membrane fuel cell (HT-PEMFC) stack development, yet it hasn't been studied for HT-PEMFC. A three-dimensional, non-isothermal model was developed in this work to investigate the effect of channel to rib width ratios (CRWR) on the performance of HT-PEMFC. The reaction heat caused by entropy change was divided into cathodic half-reaction heat and anodic half-reaction heat. The results show that the ratio value significantly influence the gas diffusion, electron conduction and the distribution of current density in the porous electrodes. Increasing this ratio facilitates gas transport in the porous electrode but causes higher ohmic loss due to longer distance for electron conduction. As a result, an optimal ratio of about 1 is observed, which results in a peak power density of 0.428 W/cm². High current density is observed under the channel with a small ratio value while a high ratio value would cause high current density to appear under the rib, signifying the rib size effect on electrochemical behavior of HT-PEMFC. Apart from the electrical power output, the CRWR value also greatly influences the fluid flow and temperature distribution inside the cell, which would influence the long-term stability of HT-PEMFC. In the subsequent studies, efforts will be made to develop new stack configurations with more uniform gas distribution, short electron conduction path and low temperature gradient.     

Atomistic insight into dehydrogenation and oxidation of aluminum hydride nanoparticles (AHNPs) in reaction with gaseous oxides at high temperature

Metal hydride additives, aluminum hydride in particular, have extensively been applied in solid rocket motor propellants. This work employed the reactive force field molecular dynamics to elaborate the underlying mechanism for the oxidation of highly active aluminum hydride nanoparticles (AHNPs) by gaseous oxides (CO, CO₂, NO, and NO₂). The results showed that AHNPs first went through four stages: dehydrogenation (<84 ps), Al nucleation and growth (>25 ps), micro-explosion (~31 ps), and oxidation (>28 ps). The dehydrogenation of AHNPs surface overlaps with the Al nucleation in the preheating stage and prevents the oxidation of Al by gaseous oxides. Only a small part of Al on the surface is oxidized to form a thin and uneven oxide film (0.18–0.54 nm). In the core, the formed H₂ is hindered by the shell and gradually gathers into H₂ bubbles. H₂ bubbles have great kinetic energy and become a micro-explosion promoter, eventually causing nanoparticles to burst at high temperatures. The micro-explosion accelerates the dissociation of gaseous oxides. This study provides an in-depth understanding of the mechanism of dehydrogenation and oxidation of metal hydride nanoparticles.     

Energy in the New Zealand household, 1974–1980

We evaluate those economically-traded forms of energy which are consumed in the home in New Zealand, either directly as fuel or indirectly embodied in the goods and services that add up to material lifestyle. The methodology involved using data from our energy analysis of the N.Z. economy, and household expenditure survey data from the N.Z. Department of Statistics. Over the period of the survey (1974–1980), average per household consumption of energy decreased by 19% and per capita consumption by 11%. In any year, household energy consumption (both direct and indirect) was closely related to after-tax household income; gasoline consumption was the only area of expenditure that increased faster than income. The principal conclusion of this study is that, even without improvements in the technology of energy use, the overall demand for consumer energy for direct or indirect household consumption in N.Z. is likely to increase at a much slower rate than increases in real income and significantly more slowly than in the past.     

Poly(benzimidazole)-epoxide crosslink membranes for high temperature proton exchange membrane fuel cells

The crosslinked polybenzimidazole (PBI) proton exchange membrane is prepared by blending the epoxy (diglycidyl ether bisphenol-A) resin in the PBI with an imidazole-NH/epoxide Eqv. no. ratio ranging from 20/1 to 6/1. We show that the mechanical properties of the PBI membrane are improved by introducing a small quantity of crosslinks in the membranes (i.e., an imidazole-NH/epoxide Eqv. no. ratio of 15/1-10/1). Due to its high mechanical strength, the thinner crosslinked PBI membrane (thickness ∼50 μm) has a similar H₂/O₂ gas barrier property to the thicker PBI membrane (thickness ∼80 μm). Thus, the proton transport resistance across the membrane thickness direction of the thinner crosslinked PBI membrane is lower than that of the thicker non-crosslinked PBI membrane. We show that the crosslinked PBI membrane has a better fuel cell performance than the non-crosslinked PBI membrane at 160 °C with a non-humidified H₂ gas.     

New anhydrous proton exchange membranes based on fluoropolymers blend imidazolium poly (aromatic ether ketone)s for high temperature polymer electrolyte fuel cells

The blend polymer membranes were synthesized from the methylimidazolium poly (aromatic ether ketone) (MeIm-PAEK) and fluoropolymers (PVDF and PVDF-HFP) with excellent thermal stability and improved dimensional stabilities for high-temperature polymer electrolyte fuel cells. The MeIm-PAEK exhibited good compatibility with PVDF or PVDF-HFP without phase separation. High phosphoric acid doping contents of the blend membranes were achieved at elevated temperatures with acceptable swellings. The acid doped blend membranes displayed lower dimensional swellings and higher mechanical strength compared to the MeIm-PAEK membrane, which allowed the blend membranes to obtain higher acid doping contents and proton conductivities. The MeIm-PAEK/10%PVDF membrane with a phosphoric acid doping content of 700 wt% showed a proton conductivity as high as 0.192 S cm^?1 at 180 °C under the non-humidified condition and a tensile strength of 4.3 MPa at room temperature.     

Decreasing the thermal dehydrogenation temperature of methylamine borane (MeAB) by mixing with poly(methyl acrylate) (PMA)

This paper reports on a hydrogen storage material of poly(methyl acrylate) and methylamine borane (PMA/MeAB) composite, which is synthesized by a simple solution-blending process at room temperature. The thermal decomposition process of the as-prepared composite is investigated by temperature programmed desorption/mass spectrometer (TPD/MS), thermogravimetry (TG) measurements and water displacement method. It is found that PMA/MeAB100 (100 mg PMA with 100 mg MeAB) starts to release H₂ at the temperature of 90.5 °C with the dehydrogenation peak centered at 120.7 °C. This is about 20 °C lower than that of neat MeAB. Meanwhile, the evaporation of MeAB and the volatile byproducts from the dehydrogenation stage of PMA/MeAB100 are also suppressed. The present result shows that the dehydrogenation property of MeAB is enhanced by using PMA/MeAB composite.     

A vibrational spectroscopic and modeling study of poly(2,5-benzimidazole) (ABPBI) – Phosphoric acid interactions in high temperature PEFC membranes

This paper reports a FT-ATR-IR spectroscopic study on proton conducting poly(2,5-benzimidazole) (ABPBI) membranes doped with orthophosphoric acid. The analysis of the vibrational profiles is a good diagnostic tool to help understand the interactions occurring between the phosphoric acid and the polymer membranes. The experimental data show evidence that an acid-base proton exchange reaction has occurred between the imidazole moieties in the polymer chain and phosphoric acid to produce dihydrogen phosphate ions and protonated imidazolium cations in ABPBIⁿ⁺. Vibrational modes associated with the dihydrogen phosphate ions are evident in the FT-IR spectra at lower doping levels and then become partially masked by the large amount of free phosphoric acid at high acid concentrations. Several bands in the FT-IR and FT-Raman spectra attributed to mixed modes containing varying contributions from NH bending motions exhibit high frequency shifts upon protonation the imidazole moieties. The correlatively assigned experimental vibrational bands were compared with calculated normal modes for small molecule models. The optimized geometry of the benzimidazolium dimer suggests that protonation of ABPBI results in a perturbation of the extended conjugated π system and allows rotation of the benzimidazole monomer units along the polymer chain. The results described here provide insight into the roles of phosphoric acid and ABPBI in the conduction mechanism of polybenzimidazole systems.     

Optimized supply-air temperature (SAT) in variable-air-volume (VAV) systems

A criterion, based on optimization principles, for determining the SAT setpoint in VAV systems is presented. It is generally accepted that conventional SAT reset controls (SATRC), bounded by either space humidity or ductwork size, will save cooling and/or heating energy. How-ever, the ventilation consequences and penalty resulting from increased fan power have generally been overlooked. Ventilation is impacted since changes in the SAT setpoint change the primary airflow rate and the operation of economizer cycles, i.e. the distribution of fresh outdoor air (OA). These changes may result in extra energy demand and ventilation inefficiency if the reset criterion is not appropriate. This optimization concept simultaneously reduces energy consumption and meets ventilation requirements. Simulation results illustrate that the use of the optimized SATRC saves more energy than a conventional one.     

Perovskites based on La(Sr)-Mn-O system as electrocatalyst in PEM fuel cell of high temperature

In this work, perovskites based on La_1−xMnO_3+δ and La_1−ySr_yMnO_3+δ systems were synthesized by the combustion method, where the rhomboedric phase is reached at 600 °C. These synthesized perovskites present sponge type morphology with specific surface areas higher than 10 m²/g, and nanometric crystal sizes (15–41 nm). The combustion synthesis allows using a lower temperature of calcination maintaining the nanometric features of the powders while well-crystalized phases are achieved. The conductivity was measured on the powders hand compacted, in order to obtain information of its behaviour comparative to the texture of the PEMFC electrode. Finally, cyclic voltammetry was used to study the stability of the perovskites and their catalytic activity towards the ORR, the results indicate that from all the compositions prepared La_0.7Sr_0.3MnO₃ and La_0.98MnO₃ show the most interesting results, with the appearance of a cathodic current that indicates the activity of these catalysts towards the ORR at operation temperature of HTPEMFC.