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About this Article
Written by: Patrick Gendotti
Written on: April 21st, 2012
Tags: aerospace engineering, material science, mechanical engineering, physics, security & defense, energy & sustainability, photovoltaic, power, solar cell, space
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About the Author
Patrick Gendotti is a senior studying Aerospace Engineering at the University of Southern California. Ben Bova’s Powersat novel sparked his interest in space-based solar power, and he has been a space and science aficionado ever since.
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Volume XIV Issue III > Space-Based Solar Power: A New Path Towards Sustainable, Clean Energy?
Space-based solar power (SBSP) is an idea that has been alternatively promoted and ignored since its inception in 1968. A space-based solar power system is essentially a satellite comprised mainly of solar panels that beams electrical energy down to a collecting station on Earth, which then distributes that energy to the domestic power grid. The primary advantages of SBSP are the cleanliness of the energy collection and generation, the amount of energy provided by such a system, and the energy self-sufficiency acquired by the United States. The glaring disadvantages to SBSP are launch costs, which inhibit both installation and maintenance of the power satellites, restrictive launch geography, and safety hazards. These positive and negative attributes of SBSP must be weighed meticulously to determine the current viability of solar power satellites, with the caveat that technological advances in photovoltaic arrays, reduction of launch costs, and the skyrocketing costs of fossil fuels may tip the balance in favor of SBSP in coming years.

Introduction

Space-based solar power (SBSP) was invented in 1968 and is one of the greenest technologies currently available to produce electric power. A space-based solar power system consists of an orbiting satellite comprised almost entirely of solar panels (Fig. 1) that transmits power to a ground-based collecting station using electromagnetic waves [1]. After installation, the satellite in orbit and the collecting station on the ground have essentially zero emissions, and the installation process itself generates very few emissions. The CEO of Solaren Corporation, Gary Spirnak, states that their proposed SBSP system will have “minimal impacts to the environment,” about the same as “the construction of a similarly sized terrestrial photovoltaic (PV) power plant” [2]. Solaren has negotiated a deal with Pacific, Gas, and Electric, northern California’s largest energy provider, to supply them with 200 megawatts of baseload power by mid-2016 [2]. Other companies have entered the SBSP race: Astrium, a European company, plans on launching a prototype satellite in 2016 and a fully-functional model by 2020, and the Japanese Space Exploration Agency, Mitsubishi Corporation, and Kyoto University have collaborated to test a microwave power transmission system in a simulated space environment this past year, with the ultimate hope of establishing an operational SBSP system by 2025 [3] [4]. While the idea of space-based solar power has been around for over 40 years, barriers to its implementation such as high launch costs, geographical launch restrictions, and safety hazards and unknown risks have contributed to its neglect. However, current research trends indicate that space-based solar power may be a viable option for clean, sustainable, self-sufficient domestic energy production within the next decade.
Wikimedia Commons/Wikimedia Commons
Figure 1: A SBSP satellite concept dominated by the solar panel area.

What is Space-Based Solar Power?

Space-based solar power is a blanket term covering satellite systems that have large solar arrays for the express purpose of collecting large quantities of solar energy. The remainder of the satellite consists of an antenna to beam the collected solar energy down to a power station on Earth, as well as various sensors and internal electronics. The wavelength of the electromagnetic waves transmitted from the satellite must be of sufficient size to leave unharmed flora or fauna surrounding the station, restricting the transmission wavelengths. Congress has not passed any specific requirements that pertain directly to space-based solar power transmission wavelengths, although similar scenarios with potentially dangerous electromagnetic radiation (like cell phone infrared radiation) have precipitated usage laws and minimum safety standards [5]. Aside from the requisite ground-based and space-based infrastructure, a company or institution would be needed to actively operate the SBSP system. For the satellite, operation would involve monitoring the status signals and ensuring its position in orbit remains stable. Likewise, maintenance of the ground facilities is necessary, although management of the ground facilities is not as critical since the system is largely autonomous.

Why Not Now?

Solar technology has made great strides since its invention and relative proliferation in the 1970’s, so you may wonder why the United States and other nations are not currently beaming down power from the skies. These advances have increased the feasibility of SBSP and reduced the scientific community’s general perception of SBSP as some lunatic fantasy at worst, and as a far-fetched, futuristic, and inherently foolish expenditure of time and resources at best. The following sections discuss some advantages and disadvantages of SBSP, as it currently stands. SBSP has numerous advantages over current energy generation technologies: it is immaculately clean, abundantly available, and eminently renewable. SBSP also supports domestic energy production, creates green jobs, and beautifies the landscape.

Clean, Green Energy

One of the primary advantages of space-based solar power is that it is one of the cleanest types of energy available. The sun is the primary source of energy for the Earth; solar energy that is harvested directly from the sun’s rays can be seen as the cleanest and most efficient form of energy production, since all energy the Earth receives comes ultimately from the sun. Detractors of space-based solar power may argue that the production of the solar panels themselves and the placement of the satellites in orbit may create hazardous and toxic by-products, but the damage done to the environment and the threat these materials pose to ecosystems is insignificant compared to the continued use of fossil fuels and their macro-scale impact on climate change.
Wikimedia Commons/Wikimedia Commons
Figure 2: A diagram depicting the flow of energy through a SBSP satellite. (National Space Society).

Comparison to Ground-based Solar Power

Since the atmosphere obstructs, reflects, and diffuses electromagnetic waves, ground-based solar power is intrinsically limited by the amount of solar energy reaching the Earth’s surface (Fig. 2). According to Scientific American, a maximum of approximately one kilowatt of solar power per square meter (approx. 1 kW/m^2) is available on Earth, and nearly five times that amount (approx. 5 kW/m^2) is available in space [11]. Therefore, the amount of energy available to space-based solar collectors is approximately 500% the amount of energy available to Earth-based collectors. Another significant benefit of placing solar panels in space is their ability to orbit the earth in a geostationary manner, allowing for constant exposure to the sun and continuous collection of solar energy. Solar panels placed on the earth’s surface, on the other hand, must rotate along with the planet and are unable to collect solar energy at night. Solar panels on satellites orbiting the earth do not have this same problem, since they are not attached to the earth’s surface and bound to rotate with it.

Energy Self-Sufficiency

Space-based solar power can help the United States attain a higher degree of energy self-sufficiency. The United States relies heavily on fossil fuels imported from tumultuous regions of the world, forcing the government to compromise with tyrants and their regimes in order to ensure an ample supply of those fossil fuels. With the increased focus on global warming, electric cars, alternative energy, and other “green” technologies have begun to erode the vaunted position of fossil fuels over all other forms of energy. This newfound emphasis on “green” energy, coupled with the domestic energy self-sufficiency SBSP would provide, makes SBSP a strong candidate for replacing fossil fuels both with American consumers and the government.

Economics

Another argument that favors space-based solar power over other, earth-based forms of energy production involves its potential for positive economical impact. Solar power technology is a green technology, so any jobs created as part of a space-based solar power initiative would fall under the umbrella of alternative energy jobs, which the administration has subsidized as recently as 2009 with the American Recovery and Reinvestment Act [6]. Additional jobs will be created in the private aerospace and energy industries, as companies must cooperate to design and launch the satellites into space. SBSP will create public sector jobs as well, as new government organizations, or at least new departments within existing organizations, must oversee the safe and orderly deployment of SBSP.

Aesthetics

Beauty is in the eye of the beholder, but in some cases, the beholders may still wish to avert their gazes. Many current forms of energy production are eyesores, disrupting the natural landscape of the Earth. Oil rigs, solar panels on rooftops, windmills, coal power plants, and other means to convert natural resources into electrical energy all fall within this category. Conversely, space-based solar power does not mar the natural landscape of the Earth; the satellites orbit the earth at a great distance (approximately 35,000 km or 22,200 mi), while the power collection facilities should be placed in remote, barren, and relatively deserted areas to minimize human, animal, and vegetable interaction with the electromagnetic waves beamed down from the geostationary satellites. One could argue that these collecting facilities are eyesores, but they would have minimal effect on the majority of the population, since they would be placed in locations with low population densities.

Disadvantages

Despite the panoply of reasons to support modern implementation of space-based solar power, a few flaws in the concept remain. The largest hindrances to SBSP are exorbitant launch costs, restrictive launch sites, and unknown safety risks and hazards.

Launch Costs

Launch costs have been notoriously high since the dawn of the space age, which has prevented early privatization and commercialization of space. The launch cost for one pound of payload in modern rockets is approximately $1300, which prohibits large, cheap transfers of material from earth to space. Since a 20-foot by 20-foot solar panel weighs approximately three pounds per square foot, the launch costs for a solar panel of that size and weight would be $1.56 million. This figure includes only the cost of launching the solar panel; the entrepreneurial company betting on SBSP must also plan on launching a transmitter, satellite housing, internal electronics, and tools for the satellite’s assembly. These various components add a significant amount of weight to the payload and correspondingly add a significant cost to the SBSP system. In addition to the costs associated with launching the solar panels is the maintenance of the satellites. Satellites do not operate indefinitely, and the cost of maintenance is likely proportional to launch costs, since the operating company may need to send technicians to the satellite itself. Although remote maintenance is possible, it is extremely difficult to diagnose the problems without human assistance on site.

Geographical Launch Restrictions

The satellites must be launched from the equator to remain in a geostationary orbit, so that their location does not change with respect to the earth. The geostationary orbit is essential, because the location of the earth-based power collecting station should not change with respect to the satellite, so that the satellite’s power transmission array is always directed at the power collecting station. A similar situation would be reception of satellite television within a home; the satellite dish must be oriented at the location of the communications satellite in a geostationary orbit. If the satellite’s orbit were not geostationary, the satellite’s position would change with respect to the earth, so the satellite dish would need to track the satellite as it moved across the sky (from the dish’s perspective). Some equatorial countries could exert coercive power over the United States or other countries that do not have launch sites at the equator and do not want to expend fuel (which has a direct financial impact) to transfer orbits, much as oil-rich countries do today. As a result, the United States is contemplating brokering a deal with India for a cooperative SBSP program, since India has many equatorial launch sites and has a positive relationship with the United States. One Indo-Asian News Service refers to SBSP as “the next major step in the Indo-U.S. strategic partnership,” cementing U.S. and Indian economic and technical ties [7]. Provided this partnership persists, the United States will not need to respond to the whims of unstable and undemocratic governments for access to equatorial launch sites and SBSP.

Safety Hazards

Safety hazards include misdirection of the satellite’s energy transmission beam, which could cause damage if not oriented properly, mistakes during rocket launches, and long term effects of low-frequency EM radiation [8]. Emergency scenarios may take place over the lifetime of a SBSP system that are nearly impossible to predict in advance; some safety hazards may not present themselves until the SBSP system is in operation. This unknown danger can present quite a problem to venture capitalists who take calculated risks and do not want to be held liable for damages, limiting the startup capital of potential SBSP entrepreneurs and preventing their dreams from becoming reality.

Conclusion

Space-based solar power has enormous potential for future energy generation. Although SBSP is not economically viable at this time, many of the disadvantages and flaws of such a program will diminish or disappear completely over time. According to Futron’s “Space Transportation Costs: Trends in Price Per Pound to Orbit 1990-2000” report, average launch costs decreased over 35% over the course of the decade (Fig. 3); that decrement occurred before the privatization and commercialization of space [9].
Wikimedia Commons/Wikimedia Commons
Figure 3: Futron’s estimates of launch costs per pound throughout the 1990’s.
Launch costs have fallen from approximately $4,000 to $1,300 per pound in the last decade, due to the intervention of privately funded space companies [9]. In fact, the CEO of Space Exploration Technologies, Elon Musk, asserts that launch costs of “$500 per pound or less are very achievable” in the next decade, drastically reducing the sunk costs of installing solar power satellites [10]. Trends indicate that solar panels will become better and better deals over time; energy conversion efficiencies will rise from about 20% to about 40%, and the costs of the panels themselves are likely to plunge, a development reinforced by government subsidies and incentive programs. The government can create bureaucracies to monitor and guide the budding private space industry, and in particular, the emerging space energy industry. These bureaucracies would allow preventative regulation of such bleeding edge technologies and minimize their potential hazards before they erupt into fully-fledged disasters, with the side benefit of creating jobs. Advanced launch vehicles will enable payload to undergo Hohmann orbit transfers to reach geostationary orbit despite having a non-equatorial launch site, and reduced launch costs will make this solution much more feasible. Overall, the future is bright for space-based solar power, provided predictions of the launch cost reduction, solar panel improvement, and continued emphasis on clean, green technologies are accurate.

References

    • [1] National Space Society. (2011, Nov.). Space Solar Power: Limitless clean energy from space. [Online]. Available: http://www.nss.org/s​ettlement/ssp/index.​htm
    • [2] Jonathan Marshall. (2009, Apr.) Interview with Solaren CEO Gary Spirnak. [Online]. Available: http://www.next100.c​om/2009/04/interview​-with-solaren-ceo-ga​r.php
    • [3] Corey Binns. “Space-Based Solar Power,” Pop. Sci. pp. 64-65, Jul. 2011.
    • [4] “Space-based solar power set for 1st test,” Daily Yomiuri. Jan. 23, 2011
    • [5] L. G. Salford et al. (2003, June). “Nerve Cell Damage in Mammalian Brain after Exposure to Microwaves from GSM Mobile Phones”. Environmental Health Perspectives (United States: National Institute of Environmental Health Sciences)
    • [6] “Energy Efficiency and Renewable Energy: American Recovery and Reinvestment Act.” U.S. Department of Energy [Online]. Available: http://www1.eere.ene​rgy.gov/recovery/
    • [7] “India-US space-based solar power programme urged.” Indo-Asian News Service. Sept. 13, 2010.
    • [8] Ben Bova. Powersat. New York, NY: Tom Doherty Associates, LLC, 2005.
    • [9] “Space Transportation Costs: Trends in Price Per Pound to Orbit 1990-2000.” Futron Corp., Bethesda, MD. Sept. 6, 2002.
    • [10] Elon Musk. “Senate Testimony – May 5, 2004” SpaceX. Internet: http://www.spacex.co​m/press.php?page=10 [May 5, 2004].
    • [11] Tim Hornyak. “Farming Solar Energy in Space.” Scientific American. Available: http://www.scientifi​camerican.com/articl​e.cfm?id=farming-sol​ar-energy-in-space [Apr. 1, 2008].