Solar Power SatellitesA Radical solution to the energy crisis Phase - II

RV College of EngineeringDepartment of Electronics and Communication

Presented by: R Jayanth

MethodologyPhase-IIntroduction to Space Based Solar Power Systems (SBSP).Need for SBSP.Thermodynamic Cycles for Solar Power generation (Brayton Cycle).Reception of Solar Power on Earth by means of Rectifying Antennae.Calculation of Efficiency of Rectification.MATLAB graphs of Wireless Power Transfer circuits.Phase-IIBrief history of Solar Power Satellite (SPS) Technology.Various SPS models proposed.Mechanism of transmission of power through microwaves.Rankine Cycles as an alternative to Brayton Cycle for power generation.Satellite orbit simulation using MATLAB.

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RecapThe worlds non-renewable energy resources are being consumed at an ever increasing rate.Solar Power Satellites are a radical new solution to this problem.They are a means of tapping into the almost infinite energy reserves of the sun in a more efficient way than can be done on earth.

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History

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The concept of Solar Power Satellites was first conceived by Isaac Asimov, in his 1961 short story, Reason.In 1973Peter Glaserwas granted a U.S. patent for his method of transmitting power over long distances.NASA carried out a small-scale study in 1974.Between 1978 and 1986, theCongressauthorized theDepartment of Energy(DoE) andNASAto jointly investigate the concept.On Nov 2, 2012, China proposed space collaboration with India that mentioned SBSP.

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Proposed SPS Designs

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ElectronicsTransmission of 50-60Hz of of electrical energy from the generation point to the consumer without any physical wires is yet to mature as a viable technology.The microwave transmission system has three aspects: 1. The conversion of direct power from the photovoltaic cells, to microwave power on the satellites on geosynchronous orbit above the Earth. 2. The formation and control of microwave beam aimed precisely at fixed locations on the Earths surface. 3. The collection of the microwave energy and its conversion into electrical energy at the earths surface.

Wireless Power Transmission6

Electronics

Magnetron7The generation of microwaves is done with a device called a magnetron.

ElectronicsMagnetron is a high powered vacuum tube device that generates microwaves owing to the motion of clouds of electrons in a crossed electric and magnetic fields. It consists of a cathode which is placed at the centre and has a ring shaped anode with cavities surrounding it.A permanent magnet is placed beneath the anode.The cathode is heated and a potential is applied between anode and cathode.Electrons get liberated from the cathode, and take a helical path to the anode.As the electrons pass the cavities in the anode, microwaves are generated.

Magnetron8

MathematicsVectors are used to represent the position of the satellite w.r.t. the earth. A combinations of vectors and calculus is used to derive the equations for all the parameters related to the satellite orbit.

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Mathematics

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MathematicsSolar Radiation PressureIt is assumed that a fraction, s, of the impinging photons is specularly reflected, a fraction, d, is diffusely reflected, and a fraction, a, is absorbed by the surface.s + d + a = 1The solar radiation pressure (SRP) force acting on an ideal flat surface is then expressed as

For an ideal case of a perfect mirror:Also, for an ideal case of a black body: For most practical cases of satellites with small pitch angles force per unit mass is:

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Mechanical EngineeringIt is another alternative to using photovoltaic cells in Solar power Satellites.The energy from the sun is converted into electrical energy with the help of a working fluid that cycles repeatedly through the system.

Solar Rankine Cycle12

Mechanical EngineeringThe working fluid gets heated by using the energy from the sun.It undergoes constant pressure heating.The high temperature and pressure fluid causes the blades of the turbine to rotate, and thus electricity is generated.The waste heat is rejected by the radiator.The fluid gets pumped into the heater again, and the cycle repeats.

Solar Rankine Cycle13

Mechanical EngineeringThe Rankine cycle studied by NASA uses potassium as the working fluid.Potassium Rankine cycles show lower efficiencies than the steam cycles.However steam cycles require large radiator size since due to low heat rejection rates of water when compared to potassium.The difference between Brayton cycle and Rankine cycle is that the Brayton cycle is normally an open cycle, and uses a constant phase working fluid, while the opposite is true for the Rankine cycle.

Solar Rankine Cycle14

Computer ScienceSimulation is a necessary stage in the development of any new technology.MATLAB (matrix laboratory) is a multi-paradigm numerical computing environment and fourth-generation programming language.It can be used to generate graphs and models using input in the form of programs.Satellite orbit simulation is crucial for both launch operations and long term tracking of the satellite.

Simulation of Satellite Orbit15

Computer Science

Simulation of Satellite Orbit16

References

[1] Bong Wie, Integrated Orbit, Attitude, and Structural Control Systems Design for Space Solar Power Satellites, Arizona State University, 2001[2] ,N. Shinohara, Wireless Power Transmission for Solar Power Satellite (SPS), Kyoto University, 2014[3] Space Research Associates Inc., Solar Power Satellites Built of Lunar Materials, Space Studies Institute, 1985[4] Nancy Teresa Cabrera, MATLAB GUI Visualization of Classical Orbital Elements, California Polytechnic State University, 2010[5] Debarghya Das, Satellite Orbit Analysis and Simulation (in MATLAB) [VIDEO], 2012[6] National Space Society Archives (http://www.nss.org/)

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