Operation of a commercial solar gel pond

The solar gel pond is an innovative concept which overcomes many of the shortcomings of the conventional salt-gradient solar pond. In this paper, the design, construction and start-up details of a commercial scale pond (400 m²), built for a publishing company in Albuquerque, New Mexico will be presented. A pond with trapezoidal cross section was designed so that shadowing could be minimized and also the ratio of surface area to the volume of the storage zone could be maximized. The publishing company required a minimum of 1 GJ/day (1MBTU/day). Generally it has been noted that in ponds with large volume a lesser percentage of retained energy is lost as edge losses. Based on the above consideration a pond size of 400 m² and 5 m deep with a gel thickness of 60 cm and a mass flow rate (for the heat extraction loop) of 1 × 10⁻⁴ to 1 × 10⁻³ kg/m²·sec was determined to be the optimum size for the publishing company's needs. Two to seven percent salt water was used mainly to keep the gel bags floating on the surface. Tedlar bags were used to contain the gel. During the first year of operation, while the pond was still heating up, the pond obtained a temperature of 60°C and the gel showed no signs of degradation.     

A scheme for large scale desalination of sea water by solar energy

A scheme is proposed to desalinate sea water using solar energy for the Thar Desert of India. The scheme has been using solar energy for the Thar Desert of India. The scheme has been designed to produce about 5.25 × 10⁷ m³/yr (13860 MG/yr) of fresh water with 11.52 km² (4.5 miles²) of collector area. The solar collectors are rectangular concrete tubes, half buried in the ground, through which sea water flows and is heated by solar energy. The heated sea water is then flash evaporated in a multi-stage flash evaporator (MSF) unit to yield fresh water. Pumping of the sea water to the site and through the MSF unit is powered by 415 wind turbines each of 200 kW capacity. Economic analysis of the scheme shows that it compares favorably with the existing fossil fuel fired desalination plants of the equivalent capacity.     

A group of improved heat and mass transfer correlations in solar stills

Based on the analogy of heat and mass transfer and an empirical correlation, a group of improved heat and mass transfer correlations in basin type solar stills is established. In order to validate the correlation group, a multi-stage stacked tray solar still with basin area of 0.665×0.650 m² is constructed of aluminum sheets. By comparison of the calculated results with the measurement results, which were obtained from our steady state simulated experiments and reported in previous literature, it is found that the correlation group developed in this work can provide better predictions for the evaporation rate of basin type solar stills at the wide range of Rayleigh number (3.5×10³<Ra<2.26×10⁷) and temperature (35<T_w<86 °C).     

Prospects for geothermal energy applications and utilization in Canada

Like the sun, the earth is a vast energy source. The utilization of this geothermal furnace is still in its infancy, the heat flow from the mantle to the surface (9 × 10⁻¹ cal/cm²/min; 0.063 W/m²) is the energy equivalent to 2 × 10¹¹ barrels of oil per yr (3 × 10¹⁰ tons or about fourfold greater than the present yearly total world energy consumption). Although today only local hot spots yielding dry and wet steam, and shallow hot-water sites are used economically, future technology may well lead to a much greater utilization. This will be done through additional imaginative and sophisticated exploitation of available regions of dry hot rock, geopressure-geothermal fields, and even deep areas of significant heat flow. Such potential utilization of geothermal resources should provide for relatively pollution-free, steam-generated electrical power, steam and hot-water for home and industry, mineral and chemical by-products, as well as numerous uses where hot water is required in agriculture, horticulture, fisheries, mining, pulp and paper and other industries. Canadian developments in these areas are still relatively dormant. The problem areas are not of a technological nature but rather of an institutional type in passing a geothermal act that would provide the incentives for exploration and economical development.     

Seawater as salt and water source for Solar Ponds

This paper presents a method for preliminary design of a 1 km² solar pond that will be supplied with salt and water from the sea. The evaporating basins, needed to concentrate the seawater are also included in the project. Starting from the experience that Agip Petroli gained in running the 25,000 m² Solar Pond, built inside a salt-work in Margherita di Savoia, in southern Italy, two projects were worked out: the first one of 25,000 m² and the second one of 1 km² of surface. Making comparison between harvested energy cost of the solar pond, and the energy cost of alternative and traditional energy sources, the coastal Solar Pond of 1 km² that utilizes seawater as salt and water source, is competitive.     

Combined heat and mass transfer by natural convection at horizontal cylinder electrodes

Simultaneous heat and mass transfer in free convection at horizontal cylinder electrodes has been investigated experimentally using the electrochemical limiting diffusion current technique. The convective flow patterns occuring have been observed using Schlieren photography. The results confirmed the use of a combined Grashof number (GR_m) to account for thermal and concentration buoyancy effects. Various combinations of electroactive species concentration, cylinder diameter and cylinder surface temperature have been used. Results have been successfully correlated by the equations , 7×10⁷ < GR_mSc< 4×10⁹ and , 4×10⁹ mSc<10¹¹ The experiments cover the range of mass transfer and heat transfer Grashof numbers 3.64×10⁴ m <3.02×10⁶, 5.67×10⁴ h <6.55×10⁶     

Energy overview for the sultanate of oman

Since 1967, exporting crude oil has been the leading hard-currency earner for Oman: 9×10⁵ barrels of crude oil per day being extracted in 1997. The total remaining oil reserves, which can be harnessed economically now, amount to approximately 5.2×10⁹ barrels, but this commercially-available resource is expected to be depleted completely by the year 2015. The second most important source of energy in the country is natural gas: present economically-harnessable reserves are approximately 724×10⁹ Nm³. In 1994, the amount extracted was merely 2.4×10⁹ Nm³. This resource is expected to be exhausted by the year 2064. From 1990 to 1995, the Government-run electricity-generation power-capability rose from 1277 to 1642 MW: the peak demand has grown simultaneously by 59%. The total-power generation in 1995 was 6500 GWh, while the annual consumption was 6173 GWh; the domestic sector accounting for approximately 60% of the total consumption. The rate of energy consumption pattern is seasonal in nature, with the mid-summer electric demand being nearly triple that of mid-winter. Private cars accounted for 54% of the total number of vehicles in Oman in 1994, and this number is rising rapidly. The associated freedom of choice to use the private car in order to satisfy the desires for increased mobility and privacy will not be sustainable in the long term.     

Estimation of convective mass transfer in solar distillation systems

In this article a thermal model has been developed to determine the convective mass transfer for different Grashof Number range in solar distillatiOn process. The model is based on simple regression analysis. Based on the experimental data obtained from the rigorous outdoor experimentation on passive and active distillation systems for summer climatic conditions, the values of C and n have been calculated. The modified values of C and n for Nu=C(GrPr)ⁿ, are proposed as C=0.0322; N=0.4114 for 1.794 × 10⁶6 in a passive solar still and C=0.0538; N=0.383 for 5.498 × 10⁶6 in an active solar still. The percentage deviation between experimental and theoretical results are found within an accuracy of 12%.     

Electrical and optical properties of F-doped textured SnO2 films deposited by APCVD

This paper presents the structural, electrical and optical properties of transparent conducting F-doped textured SnO₂ films prepared by atmosphere pressure chemical vapour deposition (APCVD). Polycrystalline SnO₂:F films having a variable preferred orientation have been obtained with resistivity as low as 5 × 10⁻⁴ Ωcm, with carrier concentrations between 3.5 × 10²⁰ and 7 × 10²⁰ cm⁻³, and Hall mobilities from 15.7 to 20.1 cm²/V/s. The average transmittance (including diffusion transmittance) is as high as 94% in the wavelength range of the visible spectrum and the maximum infrared reflectance reaches 92% for a film 655 nm thick. The figure of merit ƒ_TC = T10/_sh, (7.12 × 10⁻² S) of these films is the highest amongst the results reported on doped SnO₂ films.     

Desalination by solar-powered reverse osmosis in a remote area of the Sultanate of Oman

The Ministry of Water Resources successfully conducted an experimental study on the use of solar power to desalinate brackish ground water at their Heelat ar Rakah camp, a remote location some 900 km south of Muscat, the capital of Oman. The system comprises components for pre-treatment of pumped well water to separate hydrogen sulphide, acid dosing to correct the pH, cartridge filtration, a solar powered reverse osmosis unit, and a reject-water evaporation pond. The solar powered system comprises a 23.2 m² solar photovoltaic generator with a peak capacity of 3250 W_p, a boost charge battery of 200 Ah at 48 VDC, a charge controller, a sine-wave inverter of 3000 VA with an output of 230 V, 50 Hz, and necessary controls and instrumentation. The design water output of 5 m³/day during 5 h (of each day) was achieved, with the output sometimes exceeding 7.5 m³/day. The average cost of production is estimated at US$6.52/m³ over the 20-year lifetime of the equipment. The study has demonstrated that solar-powered reverse osmosis systems are particularly appropriate to remote locations that have limited or no access to supply services such as fuel, power or potable water.     

Waste incineration and energy recovery

We discuss the implications of waste incineration on energy production at currently achieved conversion efficiencies to electricity and for realistic estimates of incinerable fractions of municipal, hazardous, and biomedical wastes. We find approximate steady-state contributions in the U.S. of 6.1 × 10³, (3.0–3.9) × 10³ and 0.5 × 10³ MW_e for these three technologies, respectively. A combustion-research agenda for waste incinerators is summarized briefly. Its implementation may be expected to contribute to the efficacious development of waste-incineration technologies and associated energy recovery.     

太阳能在污水处理厂中的运行模式

我国太阳能资源丰富,陆地表面每年接收太阳能辐射总量达3.4×10³ ~ 8.4×10³ MJ /m²。污水处理厂因其占地面积大、高能耗等特点,与太阳能应用具有潜在的共生优势。文章主要通过污水处理厂两大处理内容——污水处理和污泥处置过程中的不同环节介绍了相应的太阳能应用技术,并通过实际案例及相应模拟计算,分析了污水处理厂的整体能耗及经济效益。结果表明,太阳能应用于污水处理厂中可大大降低其能耗和运营成本。     

海洋天然气水合物开发产能及出砂研究

海洋天然气水合物多分布在深水非成岩储层,其开采过程中易出现泥砂运移（出砂）的情况且难以避免,然而出砂条件下的水合物产能估算偏差较大。本文通过室内海洋水合物降压开采出砂实验数据和海洋水合物试采公开资料,首次推导了出砂条件下现场尺度海洋水合物储层产能情况：在相当于1 200 m水深覆压、30.5 m厚的水合物细砂储层和7寸垂直井不防砂的情况下,得到最大产气速率4.63 ~ 14.1 m³/s,折合40.01×10⁴ ~ 121.84×10⁴ m³/d,综合出砂率0.16% ~ 10.74%;泥质储层在不防砂垂直井和水平井单个半径12 mm射孔下,其最大产气速率达到79.95×10⁴ m³/d和170 m³/d,但其综合出砂率是灾难性的。由于时空限制,产气速率、综合产能和出砂率还有很大提升空间,在平衡综合出砂率（控砂精度）和产气效率（产能）的情况下,有望达到产业化规模。本研究为合理估算出砂条件下的海洋天然气水合物产能提供支撑。     

A simple analytical treatment of edge-illuminated VMJ silicon solar cells

The series connected silicon vertical multi-junctions (VMJs) solar cells have been suggested as means for ensuring high voltage high efficiency solar cells. This study includes a review of some previously published work concerning the edge-illuminated VMJs solar cells. We introduce a simple one-dimensional analysis to study the high voltage series connected silicon VMJs solar cells. The cell, under study, consists of 40 VMJs. Each junction (unit cell) has dimensions of 250 μm × 0.78 cm × 500 μm. We calculate the short circuit current, the open circuit voltage and the efficiency for an ideal cell, having perfect carrier collection at short circuit conditions, and for real cells. An optimization with respect to the base doping, the emitter doping, the surface recombination velocity and the number of junctions is done for the real cell. A conversion efficiency of 20% has been calculated under AM1.5 light spectrum for real cells having a base doping of 10¹⁶ cm⁻³ and an emitter doping of 10¹⁷ cm⁻³.     

Volcanoes as a source of geothermal energy

The thermal energy available from high-temperature magma is calculated to be 8 × 10¹⁴ kcal/km³ and an upper bound for volcanic energy of 3 × 10¹⁸ kcal/volcano is determined. Approximately one-third of the energy may be obtained between about 750 and 1150 °C (i.e. above the solidification temperature of the magma), while the remaining two-thirds is available from magma in the solid state between ambient and around 750 °C. Gas dissolved in the magma possesses about 4% of the thermal energy and a large portion of that energy is potentially available as high-temperature steam. After removal of water, the gas remaining is a low-Btu gas with a heat of combustion of about 0.3 kcal/l. Utilization of both the thermal and combustion energy is the subject of current research projects.     

Assessment of oil and natural gas resources in the Gulf Cooperation Council countries

This paper deals with the assessment of oil and natural gas resources in the Gulf Cooperation Council. Currently, the reserves of oil and natural gas are estimated at 461.70 × 10⁹ barrels and 615.58 × 10¹² SCF, respectively. Data are given and analyzed on reserves and production for the period 1978–1989.     

Preparation and properties of transparent conducting zinc oxide and aluminium-doped zinc oxide films prepared by evaporating method

Undoped and aluminium-doped zinc oxide films have been prepared by thermal evaporation of zinc acetate [Zn(CH₃COO)₂ 2H₂O] and aluminium chloride [AlCl₃] onto a heated glass substrate. The structural and optoelectrical properties of the films have been studied. The effects of heat treatment for the as-deposited films in air and vaccum are investigated. Highly transparent films with conductivity as low as 2×10⁻³ Ω cm can be produced by controlling the deposition parameters. The electron carrier densities are in the range 0.2–7×10¹⁹ cm⁻³ with mobilities of 22–58 cm² V⁻¹ s⁻¹.     

Photovoltaic properties of CdTe solar cells fabricated by close spaced sublimation with screen printed CdTe sources

Screen printed CdTe layer was employed as a source for close spaced sublimation process. By controlling the initial mixture of screen printed source, the Cd content in the CdTe film varied from 49.5% to 48%. The solar efficiency of CBD CdS/CdTe cell strongly depended on the stoichiometry of CdTe films due the bulk resistivity change ranging from 2 × 10⁶ to 3 × 10⁴Ω cm. By comparing with the dark forward current of screen printed CdS/CdTe cell, it is suggested that in the CBD CdS/CdTe cell the grain size of CBD US layer should be increased to reduce the interface leakage current at low forward bias.     

基于CORA数据的南海温差能资源时空特征研究

基于2000—2013年中国近海及邻近海域海洋逐日再分析产品(China Ocean Reanalysis,CORA)数据资料,通过计算南海表层(5 m)与深层(1000 m)的温差、卡诺效率、有效水头、暖水体积量、温差能可开发量等参数,对中国南海温差能在季节、年代际的地理分布及其变化特征进行详细分析。结果表明：1)南海大于1000 m水深海域的温差均满足发电净效率的要求,可全年有效开采,温差分布具有明显季节变换特征,夏季最高,秋、春次之,冬季最低,常年高值主要集中在南沙群岛至吕宋岛西部一带。2)中沙群岛以南是卡诺效率高值且月波动较小海区,效率最高月份为5—8月份。3)南海温差能年平均有效水头介于774～945 m,高值主要分布在南海中东部、南部海域,呈西南—东北走向,有效水头在850 m以上;南海中南部、吕宋岛西部海域年际变化呈2.0～3.0 m/a上升趋势。4)南海暖水体积量月变化呈“V”型,冬季8.50×10¹³m³以上,处在较高水平;年际变化0.165×10¹³m³/a,呈增长趋势,年平均7...     

Synthesis and characterization of CuInSe2 thin films from Cu, In and Se stacked layers using a closed graphite box

Various techniques have been used to produce CuInSe₂ but the problem of producing films with the desired properties for efficient device fabrication over large areas has always persisted. The Stacked Elemental Layer (SEL) technique has been demonstrated as a method for producing films over a large area, but the films normally annealed in vacuum or in Se ambient, mostly exhibited poor morphology with small grain sizes which result in poor devices. A method of synthesizing CuInSe₂ films by annealing or selenization of the Cu, In and Se elemental layers using a closed graphite box was developed. SEM, EDX, XRD, spectrophotometric and Hall measurements were used to characterize all annealed films. Results have shown single phase chalcopyrite films with improved crystal sizes of about 4 μm The film composition varied from Cu-rich to In-rich with electrical resistivities of 10⁻³ to 10⁴ Ωcm, cattier concentrations of 5 × 10¹⁵ to 10¹⁷ cm⁻³ and mobilities of 0.6 to 7.8 cm² V⁻¹ s⁻¹ An energy band gap of 0.99 eV and 1.02 eV was obtained for a Cu-rich and near stoichiometric In-rich films respectively. Heterojunction devices using the structure ZnO/CdS/CuInSe₂ were fabricated with electrical conversion efficiencies of 6.5%.