Space-based solar power involves collecting solar energy from satellites in space and transmitting it to receivers on Earth. It offers higher solar intensity than ground-based systems since there is no atmosphere in space. Early concepts from the 1970s proposed using large solar panels on satellites to collect energy and transmit it via microwave beams to large rectifying antennas on Earth. Significant challenges to the technology include developing reusable low-cost space access and demonstrating efficient space-to-Earth power transmission. However, if implemented on a large scale, space-based solar power could supply most of humanity's energy needs by harnessing the vast solar resources available in space.

1. Space-Based solar power
(SBSP)

2. Trends of Concern

3. Future Energy Options Must Be…

4. Introduction
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.

5. How it would differ
• SBSP would differ from current solar collection methods in that the
means used to collect energy would reside on an orbiting satellite
instead of on Earth's surface.
• Higher collection rate and a longer collection period due to the lack of
a diffusing atmosphere and nighttime in space
Solar Intensity
1,366 W/m2 No Night Min Weather
Solar Intensity
1,000 W/m2 Night Loss Weather Loss
Space Solar
Ground Solar

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

7. History
• Originally known as satellite solar-power system (SSPS), was first described in November
1968.
• In 1973 Peter Glaser was granted U.S. patent for his method of transmitting power over
long distances using microwaves from a very large antenna (up to one square kilometer)
on the satellite to a much larger one, now known as a rectenna, on the ground.
• Between 1978 and 1981, the US Congress authorized the Department of Energy (DoE) and
NASA to jointly investigate the concept.
• In 1997 NASA conducted its "Fresh Look" study to examine the modern state of SBSP
feasibility.
• On Nov 2, 2012, China proposed space collaboration with India in SBSP

8. Requirements for Space Solar Power
• Low-cost, environmentally-friendly launch vehicles.
• Large scale in-orbit construction and operations: To gather massive
quantities of energy, solar power satellites must be large, far larger
than the International Space Station (ISS).
• Power transmission: To transmit power from satellites to the Earth’s
surface with minimal environmental impact.

9. Design
Space-based solar power essentially consists of three elements:
• a means of collecting solar power in space, for example via solar
concentrators, solar cells or a heat engine.
• 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
antenna (rectenna).

10. Microwave power transmission
• Power transmission via radio waves can be made more directional, allowing
longer distance power beaming, with shorter wavelengths of electromagnetic
radiation, typically in the microwave range.
• A rectenna may be used to convert the microwave energy back into electricity.
• NASA Study of solar power satellites required a 1-km diameter transmitting
antenna, and a 10 km diameter receiving rectenna, for a microwave beam at 2.45
GHz.
• Experiments in the tens of kilowatts have been performed .
• Conversion efficiency under experimental conditions was measured to be around
54% efficient.

12. Laser power beaming
Power can be transmitted by converting electricity into a laser beam that is
then pointed at a photovoltaic cell.
Compared to other wireless methods:
• Collimated monochromatic wavefront propagation allows narrow beam
cross-section area for transmission over large distances.
• Compact size: solid state lasers fit into small products.
• No radio-frequency interference to existing radio communication such as
Wi-Fi and cell phones.
• Access control: only receivers hit by the laser receive power.

14. 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.
• Rectennas would likely be several kilometers across.

15. Rectenna

16. Challenges
The most significant technical challenges are the development of
• Low-cost re-usable space access
• Dealing with launch costs
• Demonstration of space-to-Earth power beaming
• Efficient and light space-qualified solar arrays
• Space Assembly, Maintenance and Servicing, and
• Large in-space structures

17. Conclusion
The solar energy available in space is literally billions of times greater
than we use today. Space solar power is by far the largest potential
energy source available, dwarfing all others combined.
This technology on a larger scale, combined with already demonstrated
wireless power transmission can supply nearly all the electrical needs
of our planet.
Space solar power can completely solve our energy problems long
term. The sooner we start and the harder we work, the shorter "long
term" will be.

18. References
• http://www.nss.org/settlement/ssp/
• http://martianchronicles.wordpress.com/2010/06/20/our-burning-
need-for-energ/
• http://en.wikipedia.org/wiki/Space-
based_solar_power#Microwave_power_transmission
• http://spacesolarpower.files.wordpress.com