The planet is running out of time. Consider this: every day that you continue to use power generated from coal fired power stations, you contribute to the eventual collapse of the global eco-system as we currently know it.

SAVE THE PLANETPLUG INTO MOST POWERFUL RESOURCE AVAILABLE

THE SUN

• a means of collecting solar power in space, for example via solar cells .

• a means of transmitting power to earth, for example via microwave or laser .

• a means of receiving power on earth, for example via a microwave antennas (rectenna).

• Photovoltaic (PV) conversion - semiconductor cells (e.g., silicon or gallium arsenide) to directly convert photons into electrical power

• Tolerant to the space radiation environment

Solar energy conversion (solar photons to DC current)

From the Satellite

• Microwave transmitter– Frequency 2.45 GHz

• Power level is well below international safety standard

• Received at a “rectenna” located on Earth

• Recent developments – laser

Laser power stations, perhaps drawing energy from the local environment, might one day propel spacecraft throughout the solar system. Credit:NASA/Pat Rawlings

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

• 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

Rectenna Design

The rectennas will be huge, but the land underneath need not go to waste. Since the array absorbs the microwaves, but allows sunlight and rainfall through, the land could be used for farming or ranching. Or, as in this case, the rectenna could be built as a vast set of greenhouses, feeding millions.

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

20

How large is the GEO solar resource?

1 year x 1 km wide band ≈ 212 TW-years

All Remaining Oil Resource≈ 250 TW-years

1km

•Does not emit greenhouse gases.•Does not produce hazardous waste•24 hours a day, 7 days a week, in huge quantities. •It works regardless of cloud cover, daylight, or wind speed. •Any location on Earth can receive power.•Lots of space in space.•Promotes growth of space,solar and power transmission technology.

Harvesting energy from space. This recent solar power satellite design features sets of lightweight, inflatable Fresnel reflectors. These devices focus the Sun's energy on small arrays of high-efficiency photovoltaic cells. Credit: NASA artwork by Pat Rawlings/SAIC

"Sun Tower"

• Advantages –much shorter energy transmission path

lengths allowing smaller antenna sizes,– lower cost to orbit,

• Disadvantages – increased debris collision difficulties, – requirement of many more power stations

to provide continuous power delivery at any particular point on the Earth's surface.

LEO instead of GEO

• power generator - harvesting energy from the Sun • Two small solar panels could power a communications

satellite• four panels might power a robotic interplanetary probe,• six a manned spacecraft• 20 panels might supply energy to a lunar base.

"Solar Disc

• 2001: NASDA (Japan's national space agency) announced plans to perform additional research and prototyping by launching an experimental satellite of capacity between 10 kilowatts and 1 megawatt of power.

• 2007: The Pentagon's National Security Space Office (NSSO) issued a report on October 10th, 2007 that states they intend to collect solar energy from space for use on Earth to help the United States' ongoing relationship with the Middle East and the battle for oil. The International Space Station is most likely to be the first test ground for this new idea, even though it is in a low-earth orbit.

• 2007: In May 2007 a workshop was held at MIT to review the current state of the market and technology.

• 2009: A new company, Space Energy, Inc., plans to provide space-based solar power commercially. They say they have developed a "rock-solid business platform" and should be able to provide space-based solar power within a decade.

PROBLEMS

Environmental

• Possible health hazards– Effects of exposure to microwaves

• Location– The size of construction for the rectennas is

massive

Economic• Launch costs are high

International

• Geosynchronous satellites would take up large sections of space

• Interference with communication satellites• Low orbit satellites would require agreements

about rectenna locations and flight paths

• High Efficiency solar cells and production of lightweight, solar-cell laden panels

• Wireless power transmission• Robotics• Space Transportation

Way To Go…

• Ground launch systems such as

– geosynchronous orbit space elevator.• Launching from the moon –Cost 100 times lower than from Earth, due

to the lower gravity.

Launch Methods

Where SPS will take us?

Imagine soaring through space in a vehicle that could use the Sun to power itself. This Solar Clipper concept shows how solar panels could collect the Sun’s energy to keep a spacecraft moving through our Solar System.

The interior of the habitat can be landscaped with lunar soil and planted. Those living in space need not be cut off from green growing things

SPACE SETTLEMENT

home in orbit

Live on the inside of air-tight, kilometer scale, rotating spacecraft.

• More reliable than ground based solar power.• Promising energy source of the future.• In order for SPS to become a reality , several

things have to happen:– Significant breakthrough in technology.–Building SPS using materials in space.– International Co-operation.–Cheaper launch prices.

Conclusion

• NASA-www.nss.org

• www.spacefuture.com

References