Science Fact: Energy from Space and Energy from Algae are both Big Ideas trying to answer a Big Problem. In this case the Big Problem is the world’s expanding thirst for energy.
The U.S. makes up 4.4% of the world’s population yet consumes about 25% of its energy. China has more than 4 times our population, with each person consuming ¼ as much energy as we do; India has almost 4 times our population and each person there consumes 1/12 as much energy. Those two countries alone, whose people would dearly like to match our energy usage, could require 67 times the energy the U.S. is currently using, or 16 times the total energy being produced world-wide today.
Today 80% of the world’s energy is provided by fossil fuel, specifically coal, oil and gas. It is hotly debated how long fossil fuel will continue to be available at close to its present prices – 20 years? 200 years? — but even the most optimistic observers concede that supply will not be able to keep up with the dramatically increasing demand.
Talking about a big problem requires using some big numbers. To avoid jumping back and forth between thousands and trillions, or between joules of energy and barrels of oil, I’ll try to put everything in terms of one unit: a gigawatt, meaning a trillion watts, that is, the power required to light 10 million 100-watt light bulbs. [A gigawatt measures the rate of energy use, a quantity that’s also known as power. When talking about world energy consumption people usually use a crazy unit like terawatt-hours per year (one of these is equal to 0.114 gigawatt). However, we will just use gigawatts.]
How big is a gigawatt? To get a handle on this term, think of the many ways we consume energy. Besides the gas or electricity for your car, there’s electricity, natural gas and perhaps oil to power your home. You use energy when you ride public transportation and in your workplace. In addition, the products and services you consume were produced using energy, to extract and fashion the raw materials into useful items and transport them to your local Costco.
When we add it all up, our total energy usage averages 12,500 watts per person in the U.S., which is one-eighty-thousandth of a gigawatt. [You won’t be able to compute that number from the kilowatt-hours appearing on your electric bill – the average American home uses 10,837 kw-h per year, which amounts to only 1,236 watts. In other words, less than 10% of your energy usage passes through your electrical meter.] Thus one way to visualize a gigawatt is to think of it as the total energy being used by a city of 80,000 people. The 25% share of world energy used by the U.S. adds up to about 4,000 gigawatts.
If you want to address a global problem you need resources available on a global scale. Let’s set aside fossil fuel, whose capability and eventual limitation are well understood. We’ll also set aside nuclear energy, although if some form of nuclear energy gained wide social acceptance it could become a contender again. Instead, let’s consider “renewable” energy sources, meaning sources that aren’t likely to run out for millions of years. Interestingly enough, a list of these global energy sources sounds like the classical elements of ancient China, India, Greece and Babylonia:
– Earth: If you go into a deep mine, it’s hot down there. Geothermal energy takes advantage of the temperature difference between the depths of the earth and the surface. A typical estimate suggests the possibility of generating 140 gigawatts by 2050, perhaps eventually ten times that much, or 1,400 gigawatts. However, that gigantic number is still less than a tenth of the 16,000 gigawatts the world uses right now. So the earth’s heat is not a big enough idea.
– Water: Water has been a source of power for thousands of years in the form of water wheels and in modern times through hydroelectric power. Most recently, attention has focused on extracting energy from ocean waves, whose available energy has been estimated at 2,000 gigawatts. It appears that the energy in ocean waves is only slightly greater than geothermal energy.
– Air: Energy in the air, in the form of wind, also has a long history, notably in sailboats and windmills. Our modern approach is to convert wind energy to electricity at wind farms so it can be transported, stored and used in locations and at times when the wind is not available. The total energy in wind at a height of 300 feet above land and coastal water, excluding Antarctica, is estimated at 80,000 gigawatts. In other words, about 5 times the total power currently used worldwide. If we could get clever enough to tap the energy in the jet stream, that’s an even larger source of energy – 380,000 gigawatts, or about 24 times the world’s current power.
– Fire: The most impressive and reliable source of “fire” that’s readily available is of course the Sun. Thus our modern way to extract energy from fire is one or another form of solar energy. Energy from the sun hitting earth totals 174,000,000 gigawatts, or more than 10,000 times the energy we currently consume. All we need to do is to intercept a bit of it – say one percent? – and convert it to a more useful form.
The sun provides so very much more energy than any other source that it invites grandiose solutions. So here our discussion moves into Speculation!
Science Speculation: In the area of solar energy, there are two approaches that can qualify as Big Ideas. Both require us to have patience, because they are ambitious multi-year projects:
Energy from Algae. We’re familiar with solar water heaters and solar cells, and they seem to be everywhere. However, you have to expend a lot of energy to fabricate and maintain those structures, so it’s hard to imagine them covering some large area like, say, the state of Arizona (114,000 square miles).
It’s somewhat more believable to imagine thousands of square miles of algae ponds, capturing sunlight, running it through the photosynthesis cycle and producing an oil-like residue. After all, there are seven man-made lakes in the world (reservoirs) that each exceed 2,000 square miles in surface area. Containing and controlling large areas (and volumes) of water is something that humans are well acquainted with.
How much solar energy might be captured by a pond measuring 2,000 square miles (5,180 square km) in area? Each such pond receives over 5,000 gigawatts of sunlight (at noon on a clear day). Since it’s not always high noon and the length of the day varies by season and latitude, the effective amount of sunlight is one-fourth of that, or 1,250 gigawatts, with further reductions if you choose a site with lots of clouds. If energy conversion could come close to the inherent 20% to 30% energy efficiency of cyanobacteria(blue-green algae), such a pond might provide around 300 gigawatts of power. Roughly 50 such ponds (adding up to almost the area of Arizona) would match current global energy consumption, and that would be a large-scale project indeed.
A research article by D. C. Elliott et al in the journal Algal Research reports good progress in developing a continuous chemical process to produce useful crude oil from a slurry of algae. Here are your tax dollars at work at the Pacific Northwest National Laboratory of the Department of Energy, developing a “pea soup” of algae from which oil can be extracted:
Of course, this is research, on a laboratory scale. It needs to be scaled up, so a bio-fuels company has licensed the technology and is working to build a pilot plant. There will be many technical challenges to extracting large-scale energy from algae, including: water evaporation; control of competing organisms; collection and re-dispersal of algae; high-temperature, high-pressure processing of the harvested algae; and recycling of water and nutrients.
Energy from Space. The latest headliner in the race to capture the sun is a dramatic program at the Japan Aerospace Exploration Agency(JAXA) and described in a recent IEEE Spectrum article by Prof. Susumu Sasaki. Known as the Space Solar Power System(SSPS), its main feature would be a one-mile-square panel having microwave antennas facing the earth and photovoltaic solar cells on the side away from earth.
Nothing is easy out in space. Because this gigantic structure needs to have its antennas always visible to a fixed receiving station on the earth, the satellite rotates with the earth and therefore does not always collect maximum sunlight. Thus it is assisted by two large mirrors to direct sunlight onto the photocells at all times of the day and night. There’s also the problem of stabilizing such a large satellite. To accomplish this without using literally tons of fuel, JAXA plans to attach the solar panel to its instrument package with tethers six miles long. Because the control unit is farther from the earth it sees less gravity, and the difference in gravity can be used to stabilize the entire structure using “gravity gradient stabilization.” When you add all this together, energy from space certainly qualifies as a Big Idea.
Out in space, there are no clouds, there’s not much weather and the sun is always shining. Therefore, you can generate electricity 24 hours a day. To deliver it to earth, the energy is converted to microwave radiation at a frequency of 5.8 GHz, about twice the frequency of your microwave oven. There’s an antenna about a mile across on the ground to receive the microwaves and convert them back to electricity.
You would probably not want airplanes wandering into the microwave beam. However, if an airplane or a seagull happened to fly across the area, it would not burst into flame: the microwave intensity is only about a thousand watts per square meter, the same intensity as tropical sunlight on a clear day.
How much power can you generate? A single SSPS satellite could provide about a gigawatt of power. That’s the same power that a nuclear power plant produces, but without generating radioactive waste.
You have to give the Japanese credit not only for vision but also for long-term planning. The next step in the SSPS project is to demonstrate the transmission of hundreds of watts on the earth for a distance of 150 feet using antennas and pointing hardware similar to what would be on the satellite. In 2018 JAXA hopes to transmit several thousand watts of power from a spacecraft. If all goes well, the satellite would be scaled up, first to 2 megawatts, then 200 megawatts, then to a gigawatt system. The principal technical challenges are in six areas: wireless power transmission, space transportation, construction of large structures in orbit, satellite attitude and orbit control, power generation, and power management. Many questions await answers, including the initial and ongoing cost of such systems.
Ultimately, many such satellites could float above the earth, beaming down power. It would take thousands of them to supply all the power we need but space is a large place, there’s a lot of room up there. A Big Idea indeed!
Dyson Sphere. In case you thought that ideas couldn’t get any bigger than this, consider the Dyson sphere. This concept takes its name from physicist Freeman Dyson, who credits the idea to Star Maker, a 1937 science fiction novel by Olaf Stapledon. Dyson postulated that a very advanced civilization would be satisfied with nothing less than the entire energy output of the Sun. They would deploy a network of satellites, a “Dyson sphere,” surrounding the Sun and capturing essentially all of its energy. At our present state of understanding of matter, spacecraft control and the ability of humans to cooperate with one another, such a concept seems far fetched indeed!
Do you think Energy from Space, or commercial Energy from Algae, is likely to be seen within your lifetime?
Drawing Credit: laobc, on openclipart.org
Well researched, well written and timely. What makes it particularly easy to understand is the NORMALIZATION of the measuring units.
First, congratulations on attempting to tackle this complex problem in a way that tries to cut through the bewildering “Gordian Knot” of inconsistent information about energy futures using different measuring units and different technologies. I like your approach of translating all such ideas into a consistent set of units, and gigawatts seems an ideal choice. I also like how you’ve separated the competing possible sources of energy into the ancient categories of earth, air, water, and fire. The conclusion I believe you’ve reached is in agreement with my own — that terrestrial means of power generation cannot satisfy the ravenous desire for energy we humans have, and which will lead to many times today’s energy consumption if we take the long view of human evolution even before we consider population growth. This conclusion means that some kind of energy capture strategy based on solar energy seems the only practical way out if energy consumption by the rest of the world rises to the per capita status in the United States.
Unfortunately the story doesn’t end there. Even if we conquered ALL the technical problems of GENERATING or CAPTURING energy in a way that was economically feasible, I see two really big problems ahead — one is how to store energy in a practical and scalable way (since energy USE during the day does not necessarily coincide with energy GENERATION, even before you consider moving vehicles that might need on-board passive energy storage), and the other is the environmental impact of energy use given that the total amount of energy the world consumes (taking the long view) is likely to be many times what it is today.
The ideal way of “storing” energy would rely on a cycle that does not involve toxins or byproducts, such as the hydrogen-oxygen cycle to bounce back and forth between water versus molecules of hydrogen and oxygen. This theoretically would involve no waste products during energy use except releasing water, which sounds ideal. In practice, however, “burning” hydrogen to generate energy means high enough temperatures to produce various nitrogen oxides (and we have a LOT of nitrogen in the atmosphere) so even this idealized system isn’t perfect. In addition, there are a lot of practical obstacles which must be overcome before we can safely and compactly store hydrogen if you rely on the hydrogen-oxygen cycle, but we can make an assumption here that some “magic” will occur through technological innovation someday to solve both problems.
It’s the other problem, however, that I have the most concerns about — the earth can be regarded as a closed energy system if you take into account enough in-and-out factors, such as the radiation of energy from earth out into space. If we increase the amount of incident radiation which is “captured” (such as by deploying solar panels in orbit, or deploying gigantic fields of solar panels on earth that more efficiently capture solar radiation compared to the land underneath the panels, or deploy gigantic mats of algae which use sunlight in order to grow) and then made use of such “extra energy” on earth, that energy will ultimately be released in one or another form (such as heat). From that perspective, every “extra” gigawatt we capture and use on earth MUST subsequently be released BACK into space if we are to maintain a stable environment on earth. Yet even if we did somehow manage to normalize the net energy state of our planet to be what it is today, where and how we release heat into our atmosphere can easily alter localized weather patterns on earth if you take a large enough energy usage base.
Unfortunately, the “Law of Unintended Consequences” tends to overcome most of our well-meaning efforts in trying to solve Big Problems.
Excellent points, Charles. Energy storage and heat removal are both Big Problems that accompany proposed global energy solutions. Storage is less of a problem if algal oil is a success, since infrastructure to transport and store oil is already well in place; however, if electrical energy from space becomes important, that does not automatically come with an efficient means for storage. Heat removal folds into concerns about global warming, since both involve the balance between incoming solar energy and its radiation into space. Conservation, anyone??