SEMINAR

PRESENTED BY:ASHWINI KUMARREGD NO-1301214026ELECTRICAL ENGINEERING

WIRELESS POWER TRANSMISSION VIA SOLAR POWER

WIRELESS POWER TRANSMISSION

VIA SOLAR POWER

CONTENTS-1. INTRODUCTION

2. CHALLENGES

3. WIRELESS ELECTRICITY TRANSMISSION(WET)

4. COMPONENTS DETAILS OF WET

5. CONSTRUCTION OF SOLAR POWER SYSTEM

6. DESIGN

7. MICROWAVE TRANSMISSION

8. LASER TRANSMISSION

9. DRAWBACKS

10. LAUNCH COSTS

ABSTRACT

The solar power wireless transmission of energy is completely based on solar energy resources widely available through the outer environment. This paper mainly concerns about the conversion of energy obtained from the sun by satellite to microwaves using a externally paced device called magnetron. Satellites in the earth’s atmosphere receives the ultraviolet rays in the form of photons and then broadcast them to the centre by the form of converted microwaves. These microwaves travels a long area to reach the device in the receiving centre called rectenna . These rectenna will convert those microwaves into required energy source and distributes them to all available primary and secondary vectors. Then the transmission and distribution process begins resolving all energy needier.

1. IntroductionThe present electricity generation system is not very efficient in terms of energy transfer. About 20 to 30% energy is lost during the distribution of the electricity. Therefore the scientists are working on the projects to improve the ultimate electricity supply. Scientists are looking for alternate and efficient technologies to provide 100% electricity transfer. The change and development in the various fields have brought more client satisfaction and output.

Part of the solar energy (55–60%) is lost on its way through the atmosphere by the effects of reflection and absorption. Space-based solar power systems convert sunlight to microwaves outside the atmosphere, avoiding these losses, and the downtime (and cosine losses, for fixed flat-plate collectors) due to the Earth's rotation.

Space-based solar power (SBSP) is the concept of collecting solar power in space (using an "SPS", that is, a "solar-power satellite" or a "satellite power system") for use on Earth. It has been in research since the early 1970s.

 solar power satellite (SPS) concept for a future gigawatt space power system, to provide electrical power by converting the Sun's energy and beaming it to Earth's surface, and provided a conceptual development path that would utilize current technologies. SERT proposed an inflatable photovoltaic gossamer structure with concentrator lenses or solar heat engines to convert sunlight into electricity. The program looked both at systems in sun-synchronous orbit and geosynchronous orbit. Some of SERT's conclusions:

1. The increasing global energy demand is likely to continue for many decades resulting in new power plants of all sizes being built.

2. The environmental impact of those plants and their impact on world energy supplies and geopolitical relationships can be problematic.

3. Renewable energy is a compelling approach, both philosophically and in engineering terms.

4. Many renewable energy sources are limited in their ability to affordably provide the base load power required for global industrial development and prosperity, because of inherent land and water requirements.

5. Based on their Concept Definition Study, space solar power concepts may be ready to reenter the discussion.

6. Solar power satellites should no longer be envisioned as requiring unimaginably large initial investments in fixed infrastructure before the emplacement of productive power plants.

2. CHALLENGE:-The development and implementation of any new energy source present major challenges. And it is acknowledged that bringing about the use of Space Solar Power on the Earth may be particularly daunting because it is so different. The major challenges are perceived to be:

(1) The mismatch between the time horizon for the implementation of SSP and thatfor the expansion of conventional energy resources

(2) The fact that space power is intrinsically global, requiring enterprise models thatgive every player a suitable stake and adequate safeguards(3)

(3) The potential for concerns over reliability, safety and environmental implications

(4) The need to obtain publicly-allocated resources outside the normal purview of theenergy community

(5) The prevailing mind set which tends to view the future energy infrastructure as anextrapolation of the present one.However great the challenges, it is important to enhance global energy systems sothey work for all the people of the Earth.

3. WIRELESS ELECTRICITY TRANSMISSION(WET) Wireless Electricity Transmission (WET) technologyWireless power transmission is a process that takes place in any type of system in which electrical current is conveyed from a power source to an electrical load. What makes this process unique is that there is no usage of any type of wiring to connect the system to a source of power. Wireless electricity (Power) transmission basically is the transmission of electricity with the help of microwaves and there is no need to use cables, towers and grid stations . There are three methods:-

1.Short range (Induction)

This ranges few centimetres e.g. transformer in which transfer takes place due to mutual induction.

2. Moderate range (Adaptive Inductive Coupling)

(Adaptive Inductive Coupling) wireless power transfer technology can be used to charge

the electronic objects automatically. The ability of our technology to transfer power safely, efficiently, and over distance can improve products. This principle of wireless electricity works on the principle of using coupled resonant objects for the transference of electricity to objects without the use of any wire.

1. Power from mains to antenna, which is made of copper2. Antenna resonates at a frequency of about 10MHz, producing electromagnetic waves3. Tails’ of energy from antenna ‘tunnel’ up to 2m (6.5ft)

3. Long rangePlans for wireless power involve moving electricity over a span of miles. Long distance wireless

power is the technology of sending power to earth . There are many new techniques but we use only two here.

1. By using Solar Power Satellite (SPS)-

This task is often completed by using solar power satellite (SPS) placed in high earth orbit. This satellite converts the sunlight into energy; this energy is composed of microwaves. These microwave signals are transmitted to an antenna on ground/Main grid station (MGS). From MGS these waves are transferred to BGS (Base grid station) so called rectenna which convert microwaves into DC electricity. There will be energy receiver box or energy router in each home. The information of the electricity or power required for each home will be available with the grid station. At the grid station the electricity will be converted into energy packets like wise internet data packets and the header of that energy packet will include the address of the energy receiver that is mounted on the wall of the house of consumer. We used the same concept as we do in telecom sector and through this act we can buy electricity according to our need.

4. Component details of WET using SPS systemThe primary components of WET using SPS involve microwaves, solar power satellite, rectenna,

dengyo, etc. Microwaves. Microwaves are electromagnetic waves with wavelengths ranging from as long as one meter to as short as one milli meter, or equivalently, with frequencies between 300 MHz (0.3 GHz) and 300 GHz. For Wireless power transfer we use high power microwaves namely 1-10GHz radio-waves .

Microwave power transmission (MPT)-

MPT is the use of microwaves to transmit power through outer space or the atmosphere without the need for wires. It is a sub-type of the more general wireless energy transfer methods. Microwaves are widely used for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna . This allows nearby microwave equipment to use the same frequencies without interfering with each other, as lower frequency radio waves do. Microwave Power transfer (MPT) [2.45 GHz or 5.8GHZ] of ISM band is used. (ISM= Industry, Science and Medical).

FIG- Microwave Power Transfer.

5.CONSTRUCTION OF SOLAR POWER SYSTEM

6. DESIGN Space-based solar power essentially consists of three elements:-

1. collecting solar energy in space with reflectors or inflatable mirrors onto solar cells.

2. wireless power transmission to Earth via microwave or laser.

3. receiving power on Earth via a rectenna, a microwave antenna.

It needs no protection from terrestrial wind or weather, but will have to cope with space hazards such as micrometeors and solar flares. Two basic methods of conversion have been studied: photovoltaic (PV) and solar dynamic (SD). Most analyses of SBSP have focused on photovoltaic conversion using solar cells that directly convert sunlight into electricity. Solar dynamic uses mirrors to concentrate light on a boiler. The use of solar dynamic could reduce mass per watt. Wireless power transmission was proposed early on as a means to transfer energy from collection to the Earth's surface, using either microwave or laser radiation at a variety of frequencies.

7. Microwave power transmission

Microwave power transmission has been demonstrated, in conjunction with solar energy capture, between a mountain top in Maui and the island of Hawaii (92 miles away).Technological challenges in terms of array layout, single radiation element design, and overall efficiency, as well as the associated theoretical limits are presently a subject of research, as it is demonstrated by the Special Session on "Analysis of Electromagnetic Wireless Systems for Solar Power Transmission" to be held in the 2010 IEEE Symposium on Antennas and Propagation.In 2013, a useful overview was published, covering technologies and issues associated with microwave power transmission from space to ground.

Microwaves are widely used for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna. This allows nearby microwave equipment to use the same frequencies without interfering with each other, as lower frequency radio waves do. Another advantage is that the high frequency of microwaves gives the microwave band a very large information-carrying capacity; the microwave band has abandwidth 30 times that of all the rest of the radio spectrum below it.

8.LASER POWER BEAMING

Laser power beaming was envisioned by some at NASA as a stepping stone to further industrialization of space. In the 1980s, researchers at NASA worked on the potential use of lasers for space-to-space power beaming, focusing primarily on the development of a solar-powered laser. In 1989 it was suggested that power could also be usefully beamed by laser from Earth to space. In 1991 the SELENE project (SpacE Laser ENErgy) had begun, which included the study of laser power beaming for supplying power to a lunar base. The SELENE program was a two-year research effort, but the cost of taking the concept to operational status was too high, and the official project ended in 1993 before reaching a space-based demonstration.

In 1988 the use of an Earth-based laser to power an electric thruster for space propulsion was proposed by Grant Logan, with technical details worked out in 1989. He proposed using diamond solar cells operating at 600 degrees to convert ultraviolet laser light.

A laser SBSP could also power a base or vehicles on the surface of the Moon or Mars, saving on mass costs to land the power source. A spacecraft or another satellite could also be powered by the same means. In a 2012 report presented to NASA on Space Solar Power, the author mentions another potential use for the technology behind Space Solar Power could be for Solar Electric Propulsion Systems that could be used for interplanetary human exploration missions.

9.COMPARISON BETWEEN MICROWAVE AND LASER

10.EARTH BASED RECEIVER RECTENNA

A rectenna is a rectifying antenna—a special type of antenna that is used to convert electromagnetic energy into direct current (DC) electricity. They are used in wireless power transmission systems that transmit power by radio waves. A simple rectenna element consists of a dipole antenna with an RF diode connected across the dipole elements. The diode rectifies the AC current induced in the antenna by the microwaves, to produce DC power, which powers a load connected across the diode. Schottky diodes are usually used because they have the lowest voltage drop and highest speed and therefore have the lowest power losses due to conduction and switching. Large rectennas consist of an array of many such dipole elements.

In recent years, interest has turned to using rectennas as power sources for small wireless microelectronic devices. The largest current use of rectennas is in RFID tags, proximity cards and contactless smart cards, which contain an integrated circuit (IC) which is powered by a small rectenna element. When the device is brought near an electronic reader unit, radio waves from the reader are received by the rectenna, powering up the IC, which transmits its data back to the reader.

Earth-based receiver

The Earth-based rectenna would likely consist of many short dipole antennas connected via diodes. Microwave broadcasts from the satellite would be received in the dipoles with about 85% efficiency. With a conventional microwave antenna, the reception efficiency is better, but its cost and complexity are also considerably greater. Rectennas would likely be several kilometers across.

The rectenna can also take any type of rectifying circuit such as single shunt full-wave rectifier, full-wave bridge rectifier, or other hybrid rectifiers. The circuit, especially diode, mainly determines the RF-DC conversion efficiency. Silicon Schottky barrier diodes were usually used for the previous rectennas. New diode devices like SiC and GaN are expected to increase the efficiency. The rectenna using the active devices is not passive element. The single shunt full-wave rectifier is always used for the rectenna. It consists of a diode inserted to the circuit in parallel, a λ/4 distributed line, and a capacitor inserted in parallel. In an ideal situation, 100% of the received microwave power should be converted into DC power. Its operation can be explained theoretically by the same way of a F-class microwave amplifier.

Environmental Issues Interferences to Existent Wireless SystemMost MPT system adopted 2.45 GHz or 5.8 GHz band which are allocated in the ITU-R Radio Regulations to a number of radio services and are also designated for ISM (Industry, Science and Medical) applications. Conversely speaking, there is no allowed frequency band for the MPT, therefore, we used the ISM band. The bandwidth of the microwave for the MPT do not need wide band and it is enough quite narrow since an essentially monochromatic wave is used without modulation because we use only carrier of the microwave as energy. Power density for the MPT is a few orders higher than that for the wireless communication. We have to consider and dissolve interferences between the MPT to the wireless communication systems.

One calculation of the interferences between the MPT of the SPS, mainly 2.45 GHz, to the wireless communication systems was done in Japan. If the harmonics of the MPT frequencies are, however, regulated by the ITU (International Telecommunication Union) power flux density (PFD) limits, some modulation might be necessary. Carrier noises, harmonics, and spurious emissions of the MPT signal should be quite small to avoid interference to other radio services in operation around the world. Grating lobes and side lobes of the MPT beam should be low enough in order to make the affected region as small as possible.

Safety on GroundOne of the characteristics of the MPT is to use more intense microwave than that in wireless communication systems. Therefore, we have to consider MPT safety for human. In recent years there have been considerable discussions and concerns about the possible effect for human health by RF and MW radiation. Especially, there have been many research and discussions about effects at 50/60 Hz and over GHz (microwave). These two effects are different:-

There is long history concerning the safety of the microwave. Contemporary RF/microwave standards are based on the results of critical evaluations and interpretations of the relevant scientific literature. The SAR (specific absorption rate) threshold for the most sensitive effect considered potentially harmful to humans, regardless of the nature of the interaction mechanism, is used as the basis of the standard. The SAR is only heating problem. The scientific research results have indicated that the microwave effect to human health is only heating problem. This is different from the EMF research. Famous guideline, the ICNIRP (International Commission on Non-Ionizing Radiation Protection) guidelines, are 50 or 10 W/m2 for occupationally exposed vs. the general public, at either frequency. The controlled and uncontrolled situations are distinguished by whether the exposure takes place with or without knowledge of the exposed individual, and is normally interpreted to mean individuals who are occupationally exposed to the microwave radiation, as contrasted with the general public. In future MPT system, we have to keep the safety guideline outside of a rectenna site.

11.DRAWBACKS

The SBSP concept also has a number of problems:

The large cost of launching a satellite into spaceIn accessibility: -

1. Maintenance of an earth-based solar panel is relatively simple, but construction and maintenance on a solar panel in space would typically be done tele robotically. In addition to cost, astronauts working in GEO orbit are exposed to unacceptably high radiation dangers and risk and cost about one thousand times more than the same task done tele robotically.

2.The space environment is hostile; panels suffer about 8 times the degradation they would on Earth (except at orbits that are protected by the magnetosphere). Space debris is a major hazard to large objects in space, and all large structures such as SBSP systems have been mentioned as potential sources of orbital debris. The broadcast frequency of the microwave downlink (if used) would require isolating the SBSP systems away from other satellites. .The large size and corresponding cost of the receiving station on the ground. Energy losses during several phases of conversion from "photon to electron to photon back to electron,

12. LAUNCH COST Assuming a solar panel mass of 20 kg per kilowatt (without considering the mass of the supporting structure, antenna, or any significant mass reduction of any focusing mirrors) a 4 GW power station would weigh about 80,000 metric tons, all of which would, in current circumstances, be launched from the Earth. Very lightweight designs could likely achieve 1 kg/kW, meaning 4,000 metric tons for the solar panels for the same 4 GW capacity station. This would be the equivalent of between 40 and 150 heavy-lift launch vehicle (HLLV) launches to send the material to low earth orbit, where it would likely be converted into subassembly solar arrays, which then could use high-efficiency ion-engine style rockets to (slowly) reach GEO (Geostationary orbit).

With an estimated serial launch cost for shuttle-based HLLVs of $500 million to $800 million, and launch costs for alternative HLLVs at $78 million, total launch costs would range between $11 billion (low cost HLLV, low weight panels) and $320 billion ('expensive' HLLV, heavier panels). To these costs must be added the environmental impact of heavy space launch emissions, if such costs are to be used in comparison to earth-based energy production. For comparison, the direct cost of a new coal or nuclear power plant ranges from $3 billion to $6 billion per GW (not including the full cost to the environment from CO2 emissions or storage of spent nuclear fuel, respectively); another example is the Apollo missions to the Moon cost a grand total of $24 billion (1970s' dollars), taking inflation into account, would cost $140 billion today, more expensive than the construction of the International Space Station.

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