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§ 5.12.2 SPS Compared to Other Power Sources

There are many different ways of generating electricity, e.g., coal fired power plants, nuclear energy, oil, natural gas and hydroelectric dams. The bottom line is that the sources that are used are those which are least expensive.

Likewise, there are many different ways we use energy, e.g., air conditioning, space heating, transportation, lighting and manufacturing. The best energy source is one which is flexible enough to be adapted for diverse uses.

Finally, our societies are requiring energy sources that minimize destruction or degradation of the environment, though large tradeoffs are always made with today's energy sources.

Even though SPS is technically feasible, environmentally attractive, and electricity is highly flexible and clean, will SPS be economically competitive? Yes. I have worked in the construction industry, and also intensely studied different energy supply technologies, and can produce this basic, common sense analysis:

Compared to today's energy sources, the SPS and rectenna system offers an economically competitive large scale energy source, and in fact appears to offer a much less expensive energy source once significant space-based infrastructure is established. In addition, the SPS and rectenna system has strong advantages in terms of environmental issues. It appears that SPS will eventually become the premier energy source for Earth. The sooner, the better.

In this section, the SPS is compared to both conventional energy sources (fossil fuels and nuclear), as well as alternative energy sources. The SPS is solar energy, so that it falls under the category of alternative energy. Compared to other solar energy concepts to date, the SPS is clearly the most feasible long-term, large scale solar power source for our economies, as well as the most economical.

Compared to today's energy sources

Currently, the world gets about 95% of its energy from coal, oil and natural gas, and almost all of the other 5% from nuclear power and hydroelectric dams.

The SPS concept appears to have inherent promise to be a most economical source of electric power to our economies, relative to today's electricity sources and all other energy sources seriously projected for the forseeable future.

The economics of energy supply consists of two elements:

  1. the cost of building the power plant and its supporting infrastructure, i.e., the front end capital cost, and
  2. the cost of operating the power plant, e.g., mines, fuel processing facilities, transportation infrastructure, and waste disposal.

Let's first look at a coal fired power plant for comparison. In terms of front end capital costs, a coal fired power plant has massive generators and mechanical systems constructed from a great variety of precision parts which are expensive. A SPS consists of a very small variety of simple parts mass produced in great quantity.

A SPS needs no fuel supply and waste handling systems.

The SPS consists mainly of a flat plane of silicon solar cells on a beam structure, with electric busbars feeding a large antenna with waveguides and tubes. The satellite is made mostly from a small variety of simple parts mass produced in space. The satellite has only small quantities of precision or special parts.

The receiving antenna on Earth would be mainly screens, posts, and concrete. Practically no moving parts.

The mass of the rectenna would be a little bit less that a coal fired power plant with the same output, assuming a safe, low power density SPS beam, and the satellite in space is about a tenth the mass of a coal fired power plant, to give you a picture of what we're dealing with.

Once built, the SPS and rectenna would continuously supply energy passively with no pollution. In contrast, a coal fired plant of equal power output to an SPS would have to burn tonnages of coal in excess of 20 TIMES the combined weight of the SPS and its ground-based rectenna, and also mine, transport, process and dispose of the ash of these tonnages, each and every year!! This is a massively expensive operation, yet it is the least expensive electricity source today which can reliably supply electrical energy in quantities large enough for our demands.

A nuclear power plant is much more complex than a coal plant, i.e., composed of an even greater variety of specialized and expensive components. A nuclear power plant is about twice as massive as a rectenna, considering just the power plant and not all the facilities required for nuclear fuel mining, transport, purification, enrichment, rod fabrication, spent fuel temporary storage, reprocessing and disposal facilities. Nuclear power plants have very high front-end capital costs (especially with ever-changing safety regulations and the need for nuclear safety), but lower operating costs compared to coal-fired plants. Nuclear power also has long pending nuclear waste disposal issues.


Cost per

on large scale?







acid rain, CO2,
mining, waste





(peaks ~2010)

acid rain, CO2,



Natural gas


(peaks ~2025)

CO2, some
acid raid

electric, heat,
LNG for transport




no (~4%)



econ. sites

Nuclear fission








far future






sunny daytimes




Solar space heating




space heat

sunny winters,
new structures

Solar thermal
electric (ground)


sunny daytimes



sunny south

Solar thermal
ind. heat (ground)


sunny daytimes



sunny south

Wind energy





some coasts

Alcohol fuels






Biomass gas






Ocean thermal









brine, sulfur,
toxic metals


few sites

The most important case against adding more nuclear fission power plants is that it takes only 20 kilograms (45 pounds) of plutonium, about the size of a grapefruit, to produce a bomb. It's been 50 years since the first nuclear bomb was made, and advanced technical knowhow is now widespread. Much smaller amounts of plutonium are sufficient for a terrorist to fatally poison areas. The more nuclear plants there are, the greater the chances of an offensive person obtaining the material one way or another in the fuel cycle. Nuclear fission is a risky energy source for the world's growing energy needs, and the sooner we start moving away from it, the better.

Coal and nuclear are more economical and reliable large scale power sources than alternative energy sources, which is the bottom line of why they are prevalent, so in the discussion here I will not give a long analysis of wind turbines, geothermal, and ground based solar energy sources (especially considering unreliable supplies and expensive storage needs for ground-based solar and wind power). The following table below summarizes the weak points of alternative energy, e.g., cost per unit of power produced, whether there's enough of it to power a significant percentage of our electricity needs, environmental problems, versatility (e.g., passive solar space heating reduces energy consumption but does not provide other energy so it's a partial solution), and location of the energy source relative to demand.

Nuclear fusion using hydrogen will be technically feasible some day, but it does not look any more economical at this point in time than fission or coal. The power plants will be complex. Plus, fusion is not clean. Fusion produces dangerous radioactive gases, e.g., tritium hydrogen, which are much harder to contain than the solid waste products of nuclear fission. Hydrogen is the most difficult element of all to contain. These radioactive gases must be contained during production (breeding) and extraction, purification, plasma fueling and of course disposal of radioactive wastes and ancillary equipment.

If we spent the same amount of money on SPSs as we do on oversold fusion, we would have a more economical and environmentally clean alternative energy source, sooner. There are no significant advances in technology required for SPSs, in contrast to the advances in technology required for fusion. The spinoffs of space development far outweigh the spinoffs due to fusion power.

You can see that the SPS and rectenna have some natural economic advantages over conventional energy sources, once space based infrastructure in emplaced. Convincing arguments can be made that the SPS will be the main power source for Earth from an economic standpoint in the long-term future.

However, the environmental advantages are also significant, as covered in another section, after we look at the pure economics and feasibility of other alternative energy sources.

Compared to "alternative" power sources

Unlike other solar energy concepts, the SPS would supply solar energy 24 hours per day. It would be reliable, too. Unlike the SPS, ground-based solar energy can't supply power at night unless it has expensive storage equipment plus extra generating capacity during the day. Further, power from terrestrial solar power plants requires backup power for cloudy days, and power generated and stored varies with the seasons.

Unreliability and planning needs make conventional solar energy inconvenient and unattractive to responsible utility companies -- an economy can't be held hostage to the whims of the weather.

Reasons why "alternative energy" concepts like wind power and ground-based solar cells have not caught on is because each concept suffers from one or more of the following issues:

  • abundance
  • concentration of energy supply
  • reliability
  • cost per kilowatt

Regarding reliability, an economy can't shut down because the wind stops blowing the wind power generators as much, causing demand/supply fluctuations in energy prices, rationing or power failures. Also, it takes a lot of wind generators in a windy place to power a small city, for example.

The figure on the left shows the effects of atmospheric absorption of solar energy on Earth on a fairly clear day. Of course, SPSs in space do not suffer from any atmospheric absorption.

The figure below shows the seasonal variations of solar energy on the surface of the Earth. Again, the SPS is not affected.

Absorption of sunlight by the atmosphere

Geothermal energy, hydroelectric dams, and other renewable sources of energy exist, but there is not nearly enough of it to power our economies, especially at costs nearly competitive to fossil fuels.

In contrast, the SPS is an abundant, reliable and a natural 24-hour supplier of energy, and rectennas can be located within sufficient proximity to consumers everywhere.

Oil, gas, and the electric economy concepts

The SPS poses a clear alternative to coal and nuclear power plants. But what about oil and natural gas? Can the SPS reduce the vulnerability of the world economy to oil cutoffs (e.g., due to a Middle East war, terrorism, or embargoes)? Would it be wise to divert our budgets away from wasteful military hardware and invest it into space development (by direct government subsidization and/or massive tax incentives)? Do we need a lead time well before oil supply starts to fall short of oil demand?


The "Electric Economy" concepts -- electric heat, electric vehicles, synthetic liquid fuels made with the help of electrical energy -- would reduce the growing world economies' vulnerability to energy shortages. This means using clean electrical energy in place of natural gas heating, and making synthetic liquid fuels from natural gas, coal, and hydrogen gas from water electrolysis.

Electric cars would be more popular if parking lots at work, shopping centers, etc., were equipped with simple plug-in recharge meters. Electric cars are clean and quiet.

Liquid fuel for long range vehicles is the main energy source which SPS electricity cannot substitute for directly. However, it can substitute indirectly by providing energy in making synthetic fuels. Also, by using electrical energy in place of oil and natural gas wherever possible, oil and natural gas are liberated for use in long range vehicles.

This requires a willingness to change a little of our infrastructure for the better, e.g., setting up plugs for electric vehicle chargers in parking lots (e.g., office buildings, shopping malls, restaurants, etc.), and opening quick-battery-swapping service stations on the road. Pumping petrol will become a thing of the past for those who choose electric vehicles.

Analyses of the costs of electric vehicles reveals that the cost of electric cars would be roughly the same as present day automobiles in a scenario of mass production of electric vehicles anywhere near the current production of gasoline (petrol) cars. The electric cars are currently more expensive because of the cost of the batteries (front-end capital cost), but the operating costs of electric cars is less since electricity costs less than gasoline, and less maintenance is required on an electric vehicle than a car powered by an internal combustion engine. Again, a main impediment is that there's no plug to charge your car at the office parking lot, at the shopping center, at restaurants, etc.

It's worth noting that from the 1920s through World War II, oil-starved Germany made synthetic gasoline on a massive scale from coal and natural gas, enough to supply the massive Nazi military machine almost exclusively.

Synthetic liquid fuels are made by hydrogenating coal and/or getting natural gas to bond into bigger molecules to form liquids. Petrol (i.e., gasoline) consists of hydrocarbons, i.e., molecules made up of carbon chains surrounded by hydrogen. Coal is pure carbon. To produce synthetic fuels from coal, you combine it with hydrogen. The hydrogen can be supplied by using electricity to split up water into hydrogen and oxygen. In the late 1970s, the U.S. funded synthetic fuels research in response to the Arab oil cutoffs, but those budget items were cut in the early 1980s, which coincided with the time an international oil shortage became an oil glut. Today, we rely on military spending and realpolitik to protect the world economies from oil cutoffs.

Oil makes up 40% of modernised countries' energy consumption. Western Europe, Japan, and the U.S. (WEJUS) consume more than 60 million barrels each and every day! We can readily replace city car gasoline consumption by using electric cars instead. By doing so, we need replace only 12 of the 60 million barrels per day equivalent in electricity, because electric cars are more than 80% efficient whereas gasoline cars are only 15% efficient (yes, most of the energy goes out the tailpipe as heat instead of motion).

Electric cars of range approximately 100 miles (150 km) at highway power without recharge are just recently starting to becomeeconomically attractive to consumers. Charging at parking lots can readily be done, though this kind of infrastructure is hard to get started, and is a great barrier to realization -- a chicken-or-egg situation.

However, we are eventually going to have to face the fact that fossil fuel production can't keep up with growing demand for fossil fuel energy because of both depletion of resources and the increased demand due to rapid development of less developed countries. Tax incentives and other measures may need to be emplaced by governments to deal with the situation, to the detriment of our future economic fluidity.

It's a simple fact that new oil discoveries have not kept pace with consumption. In the relatively oil-rich USA, oil reserves have fallen steadily since the 1960s despite technological improvements in exploration and drilling plus significantly increased drilling rates. The US imports more than 50% of its oil, today more than at any other time in history, and US dependence on imported oil only continues to increase. Europe imports more than 70%, and Japan and most free Asian nations import nearly 100% of their oil.

Modern analyses project that profitable synthetic gasoline would go to market at about $2 per gallon using slightly improved German methods from the 1920s -- about twice the price of today's gasoline in the US, or about the current price in Japan and Europe where gasoline is heavily taxed to discourage overconsumption. Synthetic fuel is not produced anywhere since Middle East oil is so much cheaper and drives synthetic fuels out of the market at the present time.

There is no place on Earth like the Persian Gulf in terms of oil abundance and cheap production.

As the rest of the world grows, we can expect the Free World to become increasingly dependent on the volatile Middle East for its oil, and thus potentially hostage to a cutoff for any reason. If and when that happens, you can expect worldwide economic recession and hardships, and excuses for outside armies to go in and try to get the oil flowing back out (and which may not be successful despite strong efforts and presences), resulting in the vast spread of terrorism, perhaps with plutonium in hand.

We can expect to maintain high military spending. However, taking a small fraction of military spending and putting it into SPS development would ultimately enhance our security permanently, and be much more economically productive and positive.

Even a beefed up military will not be enough one day, as growing world demand for oil will eventually outstrip supply.

We've been tapping most of the best oil producing geologies for decades, and more than 100 million barrels of oil each and every day is a lot of pumping from the Earth. Increasing demand from newly industrializing countries will eventually cause stiff competition for oil and price rises.

However, production of synthetic liquid fuels from coal is polluting and poses formidable environmental challenges.

We are going to have to find an alternative to consuming massive quantities of oil. If we cut out a big chunk of oil consumption by replacing half our city cars with electric cars, we will significantly relieve consumption of fossil fuels and synthetic fuels.

Putting off the problem until later only makes the problem worse. The sooner we make a committment to solving this problem, the slower we will consume fossil fuels, the less vulnerable our interdependent economies will become, and the better our futures will be. Better sooner than later.

Conservation can help, but it's not the answer. The bulk of the growth in oil consumption is coming from the less developed countries which are industrializing. It's bad enough to see the US, Japan and Western Europe alone consuming around 80 million barrels or more of oil every day for the indefinite future. When you see the industrialization of the other 80% of the world, you get an idea of the magnitude of the problem.

I've worked and lived in less developed countries, including for multinational engineering and construction companies helping to develop these countries. Indeed, I'm writing this on my notebook portable PC in a bus heading down a highway on the Thailand peninsula, a country with a low per capita income by Western standards but which has been growing at an average rate (percent of GNP) about 4 times that of the industrialized world over the past 15 years. So I'll use this country as an example:

The applications of SPSs are immediately apparent in less developed countries like this. Instead of building deep sea ports for ocean tankers, and so many refineries, pipelines, and petrol stations, for handling imports of Middle East oil, they could be supporting SPS development with the energy piped in by simple electric power lines. They would pay less for electricity than for oil, thus improving their trade balance. Electrical power lines are less destructive to the environment than the alternatives.

Instead of trying to increase domestic oil and gas production by offshore drilling, which is polluting the beautiful beaches and unique underwater sealife, long-term planning could consider substitutions of electrical energy. Already, countries like Thailand have suffered great environmental damage downwind from coal fired power plants and downstream from coal mines, and is seriously considering nuclear power beyond Thailand's current small research generators. Electricity is expensive here. Unlike in industrialized countries, liquified natural gas is popular here, largely from offshore drilling, and used for cooking and many new taxis (as in Australia).

Again, better to offer SPSs sooner than later.

In poor countries where people struggle to survive, environmental preservation is a luxury. Alternatives to environmentally destructive lifestyles must be economically available, feasible and attractive.

Electricity is a most convenient, flexible and clean modern energy source.

The rectennas are simple, relatively cheap construction items, requiring little technical know-how, and can have dual use as irrigation structures or fish farming upon bodies of water. Development around SPS electricity would be much more financially attractive for developing countries to importing oil and coal, compared to the alternatives.

It seems that positive natural market mechanisms will come to bear worldwide when we make progress on SPS development, as well as political decisions. Really, if Thailand is considering nuclear power, don't you think they would prefer solar power satellites and rectennas?

As for non-market mechanisms, it's worth noting that the US spends 300 billion dollars a year on its military to police the world, while practically nothing is spent on developing energy alternatives.

If instead, tax incentives were budgeted for private sector space development of SPS, with perhaps government subsidation (e.g., matching funds for leading companies or consortiums for the first few years just to speed up the development process), we would all get a whole lot more for our money. It's win-win for everyone in every country, especially compared to the alternatives. It will also be the advent of new energy exporters -- of solar power, up in space far from political radicals.

In any case, it seems fairly clear that SPSs and rectennas will be a major long-term power source of choice all over the world, and whatever entity develops the source and gets the patents will create a wealthy, glorious and historic legacy. It's only a matter of when, and who. > Products and Services > Solar Power Satellites (PowerSats) > Earth Power Station Comparisons

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