The Prospects for Alternative Energy

MIT recently published a five-part series of articles on our options for new methods of energy production, probably timed to coincide with humanity passing the 7 billion person mark this weekend. The articles are the intro, one article on wind energy, one on solar, one on biofuel, geothermal and nuclear energy, and one on energy conservation. I’ll excerpt the juicy bits from all of them below; since this is an entire series of articles again, this’ll be a nice long post.

From the intro:

At any given moment, the world is consuming about 14 terawatts (trillions of watts) of energy — everything from the fuel for our cars and trucks, to wood burned to cook dinner, to coal burned to provide the electricity for our lights, air conditioners and gadgets.

To put those 14,000,000,000,000 watts in perspective, an average person working at manual labor eight hours a day can expend energy at a sustained rate of about 100 watts. But the average American consumes energy (in all forms) at a rate of about 600 times that much. “So our lifestyle is equivalent to having 600 servants, in terms of direct energy consumption,” says Robert Jaffe, the Otto (1939) and Jane Morningstar Professor of Physics at MIT.

Of that 14 terawatts (TW), about 85 percent comes from fossil fuels. But since world energy use is expected to double by 2050, just maintaining carbon emissions at their present rate would require coming up with about 14 TW of new, non-carbon sources over the next few decades. Reducing emissions — which many climate scientists consider essential to averting catastrophic changes — would require even more…

Ultimately, Moniz suggests, a non-carbon energy future will likely consist largely of some combination of nuclear power, renewable energy sources and carbon-capture systems that allow fossil fuels to be used with little or no emissions of greenhouse gases. Which of these will dominate in a given area comes down to costs and local conditions.

“No one technology is going to get us into a sustainable energy future,” Jaffe says. Rather, he says, it’s going to take a carefully considered combination of many different approaches, technologies and policies.

From the second article:

Globally, 2 percent of electricity now comes from wind, and in some places the rate is much higher: Denmark, the present world leader, gets more than 19 percent of its electricity from wind, and is aiming to boost that number to 50 percent. Some experts estimate wind power could account for 10 to 20 percent of world electricity generation over the next few decades…

MIT’s Sclavounos has been working on the design of wind turbines for installation far offshore, using floating platforms based on technology used in offshore oilrigs. Such installations along the Eastern Seaboard of the United States could theoretically provide most of the electricity needed for the eastern half of the country. And a study in California showed that platforms off the coast there could provide more than two-thirds of the state’s electricity…

The main problem with wind energy, it seems, is its unreliability – having power generated on and off unpredictably results in expensive logistical problems.

From the third article:

Since solar energy is, at least in theory, sufficient to meet all of humanity’s energy needs, the question becomes: “How big is the engineering challenge to get all our energy from solar?” Taylor says.

Solar thermal systems covering 10 percent of the world’s deserts — about 1.5 percent of the planet’s total land area — could generate about 15 terawatts of energy, given a total efficiency of 2 percent. This amount is roughly equal to the projected growth in worldwide energy demand over the next half-century.

Such grand-scale installations have been seriously proposed. For example, there are suggestions for solar installations in the Sahara, connected to Europe via cables under the Mediterranean, that could meet all of that continent’s electricity needs…

Nocera foresees a time when every home could have its own self-contained system: For instance, photovoltaic panels on the roof could run an electrolyzer in the basement, producing hydrogen to feed a fuel cell that generates power…

Like nuclear power, Moniz says, solar is characterized by high initial costs, but very low operating costs. But one significant advantage solar has over nuclear is “you can do it in smaller bites,” rather than needing to build multibillion-dollar plants.

From the fourth article:

Beyond wind and solar power, a variety of carbon-free sources of energy — notably biofuels, geothermal energy and advanced nuclear power — are seen as possible ways of meeting rising global demand…

Biofuels have been an especially controversial and complex subject for analysts. Different studies have come to radically different conclusions, ranging from some suggesting the potential for significant reductions in greenhouse gas emissions to others showing a possible net increase in emissions through increased use of biofuels…

Key to biofuel’s success is the development of some sort of agriculture that wouldn’t take away land otherwise used to grow food crops. There are at least two broad areas being studied: using microbes, perhaps biologically engineered ones, to break down plant material so biofuels can be produced from agricultural waste; or using microscopic organisms such as algae to convert sunlight directly into molecules that can be made into fuel. Both are active areas of research…

Geothermal energy has huge theoretical potential: The Earth continuously puts out some 44 terawatts (trillions of watts) of heat, which is three times humanity’s current energy use…

Using this method, “there are thousands of years’ worth of energy available,” says Professor of Physics Washington Taylor. “But you have to drill deeply,” which can be expensive using present-day drilling methods, he says.

Most analysts agree nuclear power provides substantial long-term potential for low-carbon power. But a broad interdisciplinary study published this year by the MIT Energy Initiative concluded that its near-term potential — that is, in the first half of this century — is limited. For the second half of the century, the study concluded, nuclear power’s role could be significant, as new designs prove themselves both technically and economically.

The biggest factors limiting the growth of nuclear power in the near term are financial and regulatory uncertainties, which result in high interest rates for the upfront capital needed for construction. Concerns also abound about nuclear proliferation and the risks of radioactive materials — some of which could be made into nuclear weapons — falling into the hands of terrorists or rogue governments…

I think making nuclear mainstream is only going to be more difficult after the recent disaster in Japan, unfortunately.

Aaand from the final article:

Doing more with less fuel or electricity could reduce humanity’s energy demands by as much as half. No technological breakthroughs are needed for such savings, just some well-designed regulations and policies…

But even though the importance of efficiency is well-known, implementation faces many obstacles. For example, there’s the hurdle known as the landlord-tenant problem. In a nutshell, improvements in a building’s energy efficiency are typically paid for by the building’s owner, whereas the tenants — who often pay the utility bills — get the savings. Without regulations such as stronger building codes, financial incentives or gain-sharing mechanisms, a landlord has little motivation to make changes…

But some kinds of inefficiencies are not so easily reduced. For example, about two-thirds of the energy used to generate electricity using conventional steam turbines is wasted, regardless of whether the steam is heated by coal, oil, gas or nuclear fission…

Still, some of these systems are better than others: Currently, the most efficient heat-based generators are combined-cycle natural-gas plants, which use a two-stage system to squeeze the maximum energy out of the fuel, achieving overall efficiencies of around 60 percent…

That means simply making greater use of existing combined-cycle gas plants, and less use of older, much less efficient coal plants, could achieve a 20 percent reduction in overall U.S. greenhouse gas emissions without building a single new powerplant, according to a 2011 MIT study…

The implementation of efficiency improvements is full of questions and complexities, but the basic goal — and overwhelmingly, the single most important arena for making a major dent in greenhouse emissions — is crystal clear. As Jaffe puts it: “What can be done? Conserve, conserve, conserve.”

So there’s a very brief overview of alternative energy as it stands today and in the near future. Of course, as I’ve said before, there are tons of other ideas for generating electricity, but there’s always the issue of how much they cost and how large they can be scaled. For now it looks like we’ll have to keep tackling electricity generation through a combination of things, with carbon-emitting forms taking a smaller and smaller role.

I’m holding out for a breakthrough in nuclear fusion… here’s an article on a current effort at fusion at Lawrence Livermore National Laboratory. Fusion uses hydrogen as fuel and produces plenty of energy (as you can see when you look in the sky); I would hope that’s the clean, efficient future of energy production.

Very Alternative Energy: Bacteria, Sewage and Saltwater

Most of the renewable energy sources that are under consideration involve an obvious source of energy—light, heat, or motion. But this is the second time this year there has been a paper that has focused on a less obvious source: the potential difference between fresh river water and the salty oceans it flows into. But this paper doesn’t simply use the difference to produce some electricity; instead, it adds bacteria to the process and takes out a portable fuel: hydrogen.

Nobel Intent brings us: the poop power plant. When freshwater meets saltwater with a membrane between (through which water cannot pass), ions will pass from the saltwater to the freshwater, creating a potential difference = power. Meanwhile, bacteria can liberate electrons in the process of digesting organic matter. Neither of these alone create much voltage, but when you combine them (not so clear on how this part works), you have enough voltage to release hydrogen from water molecules, which you can later use for power in fuel cells. You also need organic matter for bacteria to digest, so a potential system to use this in is, for example, where sewage empties out.

And there you have it – poop power plants. The future may not be as shiny and clean as we thought…