Space Power Generation Research Articles

The high energy electromagnetic field generator

The original concept described is named the high energy electromagnetic field generator. This concept's governing physics entail the coupling of gyration (high frequency spin), vibration (high frequency abrupt pulsations/harmonic oscillations) and possible curvilinear translation, of electrically charged systems. If we couple the system's high frequency of rotation (30,000 to 100,000 RPM, and higher) with high vibration (abrupt pulsations/harmonic oscillations) frequencies in the range of 109 to 1018 Hertz (and above) we can obtain electromagnetic field intensity values in the range 1024 to 1028 Watts/m2 (and beyond). These extremely high electromagnetic field intensity values emphasise the novelty of this concept, especially suited for the design of energy generation machinery with power output levels much higher than those currently achievable. The utilisation of such high power sources for space power and propulsion generation, as it pertains to reduction in a spacecraft's inertial mass as a direct result of local vacuum polarisation, is an important application of the described theoretical concept. In this manner, extreme spacecraft speeds can be achieved.

Irradiation Response of Graphene Enhanced Gallium Nitride Metal-Semiconductor-Metal Ultraviolet Photodetectors

ABSTRACTRadiation-tolerant materials, sensors and electronics can enable lightweight space subsystems with reduced packaging requirements and increased operation lifetimes. Such technology can be used within extreme harsh environments related to space exploration, radiation medicine and power generation (combustion and nuclear). Gallium nitride (GaN), a ceramic semiconductor material, is a candidate material due to its stability within high-radiation, high-temperature and chemically corrosive environments. In addition, the wide bandgap of GaN (3.4 eV) can be leveraged for ultraviolet (UV) wavelength photodetection. In metal-semiconductor-metal (MSM) photodetector architectures using Schottky contacts, transparent electrodes (e.g., graphene) can increase sensitivity and improve overall device response. Here we present fabrication and characterization of GaN-based UV photodetectors using graphene electrodes irradiated up to 200 krad total ionizing dose (TID) then tested under UV light and dark conditions. For current-voltage measurements taken at 90, 120 and 200 krad TID, the current-voltage response does not vary significantly. From 90 to 120 krad TID, the responsivity shifts by 2% before dropping off at 200 krad TID. These initial findings suggest that graphene/GaN MSM UV photodetectors can provide robust operation within extreme harsh environments.

Heat transfer analysis of encapsulated phase change materials

Solar energy is receiving a lot of attention recently since it is a clean, renewable, and sustainable energy. Solar energy is used for space heating, power generation and other applications. A major limitation however is that it is available for only about 2000 h a year in many places. Therefore it is critical to find ways to store solar thermal energy for the off hours. Sensible heat of material has been used for storing thermal energy but due to material properties this type of thermal storage has limitations. Using encapsulated phase change materials is potentially a better way to store thermal energy with the associated reversible heat transfer. The present work deals with certain aspects of storing solar thermal energy in high temperature phase change materials with melting points above 400 °C. The objective is the storage of large amounts of solar energy (∼600 MWh). Two kinds of encapsulated capsules are considered; zinc encapsulated in nickel and eutectic salt mixtures (57 mol% NaCl and 43 mol% MgCl2) in stainless steel encapsulation. Diffusion and phase change computations are reported here in the form of temperature profiles of the phase changing and encapsulated materials for spherical capsules. The time for heating and melting during charging (storage of thermal energy into capsulated phase change material) and the time for cooling and solidification during discharging (retrieval of thermal energy) are presented for both zinc–nickel and salt–stainless steel systems. As per expectations, the time for heat transfer is much shorter for liquid heat transfer media compared to those for gases. Moreover, the heat transfer times are shorter with smaller sizes of capsules.

Experimental study of enhanced heat transfer by addition of CuO nanoparticle

An energy storage system has been designed to study the thermal characteristics of paraffin wax with an embedded nano size copper oxide (CuO) particle. This paper presents studies conducted on phase transition times, heat fraction as well as heat transfer characteristics of paraffin wax as phase change material (PCM) embedded with CuO nanoparticles. 40 nm mean size CuO particles of 2, 5 and 10% by weight were dispersed in PCM for this study. Experiments were performed on a heat exchanger with 1.5–10 l/min of heat transfer fluid (HTF) flow. Time-based variations of the temperature distributions are revealed from the results of observations of melting and solidification curves. The results strongly suggested that the thermal conductivity enhances 6, 6.7 and 7.8% in liquid state and in dynamic viscosity it enhances by 5, 14 and 30% with increasing mass fraction of the CNEPs. The thermal conductivity ratio of the composites can be augmented by a factor up to 1.3. The heat transfer coefficient during solidification increased about 78% for the maximum flow rate. The analysis of experimental results reveals that the addition of copper oxide nanoparticles to the paraffin wax enhances both the conduction and natural convection very effectively in composites and in paraffin wax. The paraffin wax-based composites have great potential for energy storage applications like industrial waste heat recovery, solar thermal applications and solar based dynamic space power generation with optimal fraction of copper oxide nanoparticles.

Ultra-lightweight space power from hybrid thin-film solar cells

The development of hybrid inorganic/organic thin-film solar cells on flexible, lightweight, space-qualified, durable substrates provides an attractive solution for space power generation with high mass specific power (W/kg). The high-volume, low-cost fabrication potential of organic cells will allow for square miles of solar cell production at one-tenth the cost of conventional inorganic materials. Plastic solar cells take a minimum of storage space and can be inflated or unrolled for deployment. We explore a cross-section of NASA in-house and sponsored research efforts that aim to provide new hybrid technologies that include both inorganic and polymer materials as active and substrate materials. For NASA applications, any solar cell or array technology must not only meet weight and AMO efficiency goals, but also must be durable enough to survive launch and space environments. Also, balance of system technologies must be developed to take advantage of ultra-lightweight solar arrays in power generation systems.

Space power generation with a tether heat engine

A new concept of space power generation is presented that exploits thermal cycles of dilatation and contraction of a spinning tethered system exposed to solar radiation. The concept exploits a lightweight film made of shape memory material directly interacting with sunlight. A temperature variation cycle in the film is created by inducing periodic variation of the tether sun aspect angle. As the film length diminishes due to the increased temperature, the mechanical energy of the system increases and can be used to charge an energy storage device. A preliminary assessment of the system efficiency and power density is conducted. It is seen that in spite of the relatively low efficiency—for present shape memory alloys—of the phase transformation the system can benefit from a very high ratio between collecting surface and overall mass, which could make it an interesting alternative to photovoltaic systems for space power plans in the future. Current limitations appear to be in the design of an efficient power conversion and incident light modulation system.

Characteristics, development and utilization of geothermal resources – a Nordic perspective

Geothermal energy is classified as a renewable energy source and it utilizes the heat generated in the earth primarily from the natural radioactive decay of isotopes of uranium, thorium and potassium. Heat is extracted from the earth to generate geothermal energy via a carrier, usually water occurring either in the liquid or steam phase. In the late 19th century and the early 20th century, the first developments of geothermal resources for power generation and household heating got underway successfully. Many of these geothermal fields are still being utilized today, proving their sustainability. Today geothermal energy is being utilized in more than 72 countries around the world and of the Nordic countries Iceland and Sweden have been in the forefront in each of their respective fields. While geothermal heat pumps are widely used for space heating in Sweden, geothermal energy covers 55% of the primary energy consumption in Iceland where it is used for space heating, power generation and industrial purposes. Future developments aim at expanding the range of viable geothermal resources by improving the capabilities to generate electricity from geothermal resources at temperatures as low as 100 C, as well as developing geothermal resources where water needs to be introduced, so-called hot dry rock resources. But the biggest expansion is expected to continue to be in the installations of geothermal heat pumps. (Less)

Analysis of thermal cycles and working fluids for power generation in space

Production of power in space for terrestrial use is of great interest in view of the rapidly rising power demand and its environmental impacts. Space also offers a very low temperature, making it a perfect heat sink for power plants, thus offering much higher efficiencies. This paper focuses on the evaluation and analysis of thermal Brayton, Ericsson and Rankine power cycles operating at space conditions on several appropriate working fluids. Under the examined conditions, the thermal efficiency of Brayton cycles reaches 63%, Ericsson 74%, and Rankine 85%. These efficiencies are significantly higher than those for the computed or real terrestrial cycles: by up to 45% for the Brayton, and 17% for the Ericsson; remarkably 44% for the Rankine cycle even when compared with the best terrestrial combined cycles. From the considered working fluids, the diatomic gases (N 2 and H 2) produce somewhat better efficiencies than the monatomic ones in the Brayton and Rankine cycles. The Rankine cycles require radiator areas that are larger by up to two orders of magnitude than those required for the Brayton and Ericsson cycles. The results of the analysis of the sensitivity of the cycle performance parameters to major parameters such as turbine inlet temperature and pressure ratio are presented, equations or examining the effects of fluid properties on the radiator area and pressure drop were developed, and the effects of the working fluid properties on cycle efficiency and on the power production per unit radiator area were explored to allow decisions on the optimal choice of working fluids.

Thermoelectric Materials for Space and Automotive Power Generation

AbstractHistorically, thermoelectric technology has only occupied niche areas, such as the radioisotope thermoelectric generators for NASA's spacecrafts, where the low cooling coefficient of performance (COP) and energy-conversion efficiency are outweighed by the application requirements.Recent materials advances and an increasing awareness of energy and environmental conservation issues have rekindled prospects for automotive and other applications of thermoelectric materials.This article reviews thermoelectric energy-conversion technology for radioisotope space power systems and several proposed applications of thermoelectric waste-heat recovery devices in the automotive industry.

Flexible Cu(In,Ga)Se 2 thin-film solar cells for space application

Thin film solar cells (TFSC) with Cu(In,Ga)Se 2 (CIGS) as absorber layer have been produced on rigid glass substrates for the terrestrial market. There exist, however, different investigations for manufacturing of TFSC on flexible substrates in order to achieve very thin and highly flexible (rollable) solar cells. Besides their capability to open new terrestrial market segments, they are considered as competitive candidates for future flexible thin film space power generators compared to traditional crystalline solar cells. This paper explains the advantages of flexible TFSC for usage in space, including: – low mass and storage volume, – high power / mass ratio [> 100 W/kg at array level], – high radiation resistance against proton and electron radiation and, – lower production costs. These cells can be produced on flexible conductive and insulating substrate materials and have efficiency potentials of up to 15%. We report on the current development steps to adopt the TFSC technology to space requirements as well as the first European industrial approach to the roll-to-roll production of flexible CIGS-TFSC on polyimide as substrate material. Stability issues in space environment concern not only the TFSC itself, but all system components such as interconnects, cell assembly and flexible blankets. The adhesion of the back-contact to the substrate, the emissivity control in the infrared wavelength range, the electrical contacting and interconnection as well as flexible encapsulation are currently under investigation and are discussed in the paper. The production costs for TFSC for space application can be further reduced by sharing resources for the production of flexible TFSC for the terrestrial market; namely by using both, the existing terrestrial investment in production facilities as well as the synergies in R and D.

Studies on Low Specific Mass NFR/MHD Power Generation System for Space Applications

The aim of this study is to examine a magnetohydrodynamic (MHD) power generation system for the space applications using a nuclear fission reactor as the heat source. This MHD system uses He/Xe mixed gas as coolant instead of alkali-metal-seeded inert gas. The interrelation between the specific heat of the coolant and the mass flow rate was examined. When the specific heat decreases due to increase of the Xe fraction, the mass flow rate must increase to keep the output power and plant efficiency constant. A regenerator efficiency of 100% and reactor output temperature of 1800 K or higher should be chosen for the highest plant efficiency of 56% and lowest specific mass of 1.4 kg/kW. This highest plant efficiency and lowest specific mass were also expected by optimizing parameters for enthalpy extraction and radiator temperature. This means achieving high plant efficiency or low specific mass gives different values for enthalpy extraction and radiator temperature. With a higher net electrical output power, lower specific mass is obtained. This explains why the present space MHD power generation system is better than other conventional space power generation systems for the high MW-range output power.

Renewable energy resources as an alternative to modify the load curve in Northern Cyprus

The average annual increase in electricity consumption and peak demand in Northern Cyprus (N. Cyprus) during the past 20 years have been 7.1 and 5.5%, respectively. In recent years, the demand for electricity has been stretched to its limits in winter. This raised the question of whether renewable energy resources could be utilized to reduce the level of peak demand. Indeed, Cyprus being a Mediterranean island, enjoys an abundance of solar energy, and preliminary studies showed that a considerable potential of wind energy is also available. Utilization of renewable energy for space heating, water heating, pumping and power generation would increase electrical reserve margins, raise system load factor, improve load following capabilities, and reduce the need for capacity expansion. Currently, solar water heating which leads to a saving of at least 72 GWh energy per annum and a significant reduction in CO 2 emission has been extensively used in N. Cyprus. In N. Cyprus, despite the availability of renewable energy resources constructing renewable base-load, electrical power stations has not been found feasible. However, constructing such systems is recommended for two reasons: firstly, as a supplement to saving fuel and secondly, expanding capacity. In this context, the economic analysis for both solar and wind energy systems, has shown a reasonable internal rate of return (IRR). Although, the IRR is higher for wind energy systems, the availability of wind is limited to a few locations and therefore energy distribution is required.

Coalbed methane extraction and utilization

Coalbed methane (CBM) is the generic name for all methane of coal seam origin. It is a natural gas formed by geological, or biological, processes in coal seams and generally consists predominantly of methane, but may also contain some higher alkanes and non-combustible gases. Methane is released whenever coal is de-stressed or fractured by mining. Methane is one of the main greenhouse gases contributing to global warming, therefore releasing it to atmosphere is an environmental hazard. However, it is also an important energy resource and can be recovered from operational coal mines, abandoned coal mines, and virgin (unmined) coal seams. Significant volumes of CBM are exploited worldwide for space heating, industrial processes, and power generation. This paper critically reviews the current UK and worldwide status of CBM extraction and utilization technologies building on a previous study funded through the Department of Trade and Industry's Cleaner Coal Technology Programme [1].

Capillary Limit of Evaporator Wick in Alkali Metal Thermal-to-Electric Converters

Vapor anode, multitube alkali metal thermal-to-electric converters are being developed for potential use in space and terrestrial electric power generation. In these converters, the capillary pressure head produced in the evaporator wick circulates the sodium working fluid. A two-dimensional, thermal-hydraulic model of the porous evaporator wick and of the liquid sodium return artery is developed and thermally coupled to an integrated model of a five-beta-alumina solid electrolyte (BASE) tube, stainless-steel sodium converter (PX-3A), and an eight-tube, Mo-41% Resodium converter. Results showed that the capillary limit in the evaporator wick of the PX-3A converter is reached at zero electrical current, when the thermal input power to the converter exceeds 16 W, or the hot-side temperature exceeds 1136 K. For the Mo-41%Re converter, these values are 22 W and 1150 K, respectively. Before reaching the capillary limit, however, two or more of the following temperature limits occurred in both converters: 1) the TiNi metal-ceramic braze joints' temperature exceeded 1123 K, 2) the evaporator wick surface temperature exceeded 1023 K, or 3) the temperature difference between the cold end of the BASE tubes and the evaporator wick surface was less than +20 K.

Space development, SPS 2000, and economic growth: the need for macro-engineering diplomacy

Solar power generation in space is anticipated as one remedy toward the solution of global environmental problems, including the energy crisis. It is argued that several problems could be solved through global cooperation that makes practical use of space solar power. Such applications today require the reduction of space transportation costs to one-hundredth or less, and the satisfactory operation of a viable pilot plant. In turn, this means that macro-engineering diplomacy is indispensable. The role that the Japanese Ministry of International Trade and Industry (MITI now METI, Ministry of Economy, Trade and Industry) would be expected to play in the former, and the proposal for an SPS 2000 pilot plant project for the latter, are discussed in this paper. Like the U.S. Federal Aviation Administration (FAA), MITI should promote the reduction of space transportation costs by encouraging the private sector to create new industries and grow the economy. An Equatorial Alliance, formed by the equatorial countries that would be supplied with space solar power by SPS 2000, could take the lead in solving global warming problems.

Power from space

This is a concise review of possibilities and prospects for power generation in space for terrestrial use. Advantages of this approach to power production, the economic and technological obstacles to be overcome, various conceptual approaches, including solar photovoltaic, solar dynamic, nuclear, and the use of chemical energy, and recommendations for progress are summarized. In view of the rising demand for energy, and of the diminishing fuel and available terrestrial area, the use of space for power generation seems to be inevitable: (1) It allows highest energy conversion efficiency, provides the best heat sink, makes best use of solar energy, and relieves the Earth from the penalties of power generation. (2) Both the costs of launching payloads into space and those of energy transmission are declining. The major obstacle is the exorbitantly high cost, which under current conditions requires, for example, the reduction of space transportation costs about a hundredfold for competitiveness. Other issues also need to be resolved, some of general nature, such as environmental effects and security and legal aspects, and some system specific, such as safety of nuclear power plants, and the realization of higher energy conversion and transmission efficiencies. Generation of power in space for terrestrial use will require massive resources, strong international cooperation, and several decades. A staged approach, fortified by developing applications collateral with space power, such as space-to-space power beaming for powering satellites, power relaying by orbital microwave or laser beam reflectors, and orbital mirrors for extended periods of terrestrial illumination, is recommended.

Vacuum as a Basis of Science and Technology. Issues for High Voltage Photovoltaic Power Generation in Space.

Vacuum as a Basis of Science and Technology. Issues for High Voltage Photovoltaic Power Generation in Space.

Milestones in the development of crystalline silicon solar cells

The development of crystalline silicon solar cells is traced from their invention to the present day, with an emphasis on the major advances (“milestones”) along the way. The survey covers cells for power generation in space as well as those for terrestrial applications.

Flexible and light weight copper indium diselenide solar cells on polyimide substrates

Thin film flexible CuInSe 2 (CIS) solar cells have been fabricated for the first time on light-weight polymeric substrates. Evaporated CuIn alloy precursors were selenized in H 2Se atmosphere at around 400°C to grow the CIS absorber layers. Low temperature techniques which are compatible with the polymeric substrates were used to deposit the window layers of CdS and ZnO. The demonstrated active area conversion efficiency of 9.3% makes this light-weight device very attractive for many terrestrial and space power generation applications where high specific power and mechanical flexibility are needed.

Advanced Solar Dynamic Space Power Systems, Part I: Efficiency and Surface Optimization

The aim of this work is the proposal and the analysis of advanced solar dynamic space power systems for electrical space power generation. The detailed thermodynamic analysis of SDCC (Solar Dynamic Combined Cycle) and SDBC (Solar Dynamic Bynary Cycle) systems is carried out. The analysis is completed with an optimization procedure that allows the maximum efficiency and minimum surface conditions to be obtained. The calculation is carried out for the orbital conditions of the NASA-Freedom Space Station. The results are presented, compared with the data already published for a reference CBC (Closed Brayton Cycle) plant (Massardo, 1993b), and discussed in depth.