Space Power Satellites & Microwave Power Transmission Presented By : Nikhil A Kothari Next Generation Future Energy

Outline Introduction Concept of SPS Solar Power Satellite Key Technologies being evaluated Microwave Power Transmission Rectannas Conclusion

Introduction The space solar power satellite (SSPS or SPS) that will transmit energy from space to the Earth has a potential to become an alternative energy sources even though there are many technical and other hurdles to realize it. Dr. P. E. Glaser first introduced a concept of the solar power satellite in 1968. Since then, many concepts of the solar power satellites were studied. NASA and DOE (Department of Energy) of U.S.A. conducted feasibility study of the proposed SPS in 1970’s. The proposed SPS has the solar array of 5km by 10km wide and a microwave antenna of 1km diameter. The on-ground rectifying antennas (Rectenna) of 10km by 13km in oval axis will produce 5GW of electrical power on ground. In 1968 PE Glaser 1st introduced to Space Power Solar Transmision.

Concept A solar-energy collector : convert solar energy into dc Electric Power. A dc-to-microwave converter :coverts dc electric power to microwave. A large antenna array : To beam the microwave power to ground. Rectanna : To convert it back to dc electric power. A solar-energy collector : convert solar energy into dc Electric Power. A dc-to-microwave converter :coverts dc electric power to microwave. A large antenna array : To beam the microwave power to ground. Rectanna : To convert it back to dc electric power.

Solar Power from Satellites 1968’s idea for Solar Power Satellites proposed by Peter Glaser Would use microwaves to transmit power to Earth from Solar Powered Satellites. Inventor of this Concept in early 1968

How it works Solar panels on satellite capture light, sends power to earth using microwave wireless power transmission technology Signal sent from receiving antenna on earth (green) allows satellite to pinpoint it’s microwave beam.

Different SPS designs Different Concept Model presented by different countries.

Microwave Power Transmission Power Received from sun at outer edge of atmosphere 1360W/m^2.

Microwave Concerns ≠ + At the earth's surface, the microwave beam has a maximum intensity in the center of 23 mW/cm2 (less than l/4 the solar constant) and an intensity of less than 1 mW/cm2 outside of the rectenna fenceline Retrodirective phased array antenna/rectenna Any animal flying through the beam would have not only a low intensity beam strike them, it would also be for only a split second, not long enough to do any real damage -Passengers in an airplane would be completely protected by the beam because of the plane’s outer casing -Retrodirective phased array antenna/rectenna: the way this works is a pilot microwave beam is emitted by the rectenna (on the ground) at a certain frequency. When the satellite gets it in space, it checks to verify that it is indeed the correct frequency and then fire back along the same path. Therefore, if anything were to disrupt the “pilot” microwave beam, the whole process would automatically shut off so a bird or a plane or any human would suffer no harm.

Factors to look at Frequency 2.45 GHz microwave beam Retro directive beam control capability Transmitting antenna The output power (beamed to the earth) Maximum power flux density Power level is well below international safety standard Why only 2.45Ghz to 5Ghz frequency is used :

Microwave vs. Laser Transmission More developed High efficiency up to 85% Beams is far below the lethal levels of concentration even for a prolonged exposure Cause interference with satellite communication industry Laser Recently developed solid state lasers allow efficient transfer of power Range of 10% to 20% efficiency within a few years Conform to limits on eye and skin damage

Rectenna “An antenna comprising a mesh of dipoles and diodes for absorbing microwave energy from a transmitter and converting it into electric power.” Microwaves are received with about 85% efficiency Around 5km across (3.1 miles) 95% of the beam will fall on the rectenna

Rectenna Design Wire mesh reflector Currently there are two different design types being looked at Wire mesh reflector Built on a rigid frame above the ground Visually transparent so that it would not interfere with plant life Magic carpet Material pegged to the ground

5,000 MW Receiving Station (Rectenna) 5,000 MW Receiving Station (Rectenna). This station is about a mile and a half long.

Reliability Ground based solar Array only works during clear days, and must have storage for night Power can be beamed to the location where it is needed, don’t have to invest in as large a grid A network of low orbit satellites could provide power to almost any point on Earth continuously because one satellite would always be in range

Environmental Possible health hazards Location Effects of long term exposure Exposure is equal to the amount that people receive from cell phones and microwaves Location The size of construction for the rectennas is massive

Pros Any location on Earth can receive power Satellite can provide power up to 96% of the time Power can be beamed to the location where it is needed, don’t have to invest in as large a grid Solar panels do not take up land on Earth Lots of space in space Waste heat is radiated back into space No air or water pollution is created during generation

Cons VERY expensive initial cost Microwave/lasers may be harmful? Cosmic rays can deteriorate panels Maintenance Problems Very large receiving antennas on earth Solar winds could kick it off course No need for costly storage devices for when the sun is not in view Only a few days at spring and fall equinox would the satellite be in shadow

Conclusions More reliable than ground based solar power In order for SPS to become a reality it several things have to happen: Government support Cheaper launch prices Involvement of the private sector

Famous Ever Green Words “Where there is Will there is way so do not give up in difficult times.” THANK YOU