Damless hydroelectricity?

Paul Raven @ 27-07-2009

Otter Estuary, Devon, UKHydroelectric power generation usually relies on harnessing the potential energy of water moving down from springs in high places, but there’s an as-yet unexploited source of power available at the estuaries where rivers flow into the sea. [via SlashDot; image by me’nthedogs]

In the inverse of the desalination process, energy is released as pure water mixes with salt water… and we may be nearing a point where technology will allow us to exploit that reaction and tap a new sustainable source of electricity:

Extracting clean, fresh water from salty water requires energy. The reverse process – mixing fresh water and salty water – releases energy. Physicists began exploring the idea of extracting energy from mixing fresh and salty waters, a process known as salination, in the 1970s. They found that the energy released by the world’s freshwater rivers as they flowed into salty oceans was comparable to “each river in the world ending at its mouth in a waterfall 225 meters [739 feet] high,” according to a 1974 research paper in the journal Science. But those who have chased the salination dream have collided with technological barriers.

Brogioli has developed a new approach to salination, a prototype cell that relies on two chunks of activated carbon, a porous carbon commonly used for water and air filtration. Once he jump starts the cell with electric power, all that is required to produce electricity are sources of fresh and salty water and a pump to keep the water flowing. When the separate streams of salty and fresh water mix, energy is released.

A typical cell would require about three dollars worth of activated carbon, and, given a steady flow of water, the cell could produce enough electricity to meet the needs of a small house. It’s the equivalent, in hydroelectric power, of running your appliances from a personal 100 meter (338 feet) high waterfall.

Science being science, there are plenty of skeptics who don’t think it’ll work – or, more generously, who don’t think it will scale well. But it’s still worth looking into, as Brogioli points out:

Brogioli maintains that his salinity cell could be ramped up faster than other salination approaches and could be made as affordable as solar power in a decade or so. He argues that any new renewable energy source is worth looking into, even if it is only a partial solution to our energy and environmental problems.

“There is no really clean energy source, and none of them can replace fossil fuels alone,” he said. “So, it’s a matter of compromise: find the best resource for a given region and use many different resources together.”


Nietzsche on science fiction

Adam Roberts @ 15-07-2009

The Adam Roberts Project

The excitement in the academic community at the discovery of four new Nietzsche notebooks has percolated, to some extent, into the general culture; and a palpable thrill has echoed through the SF community with the news that one of these notebooks contains Nietzsche’s thoughts on the—then—new genre of science fiction: Einleitende Studie, Also Sprach Zukunftsromane. The Adam Roberts Project, in conjunction with Futurismic Publishing Incorporated, is proud to be the first to reprint a selection of these Nietzschean apothegms; the full edition will be published later this year, in a dual-language edition, by Unwahrscheinlicheraben Buchbindung. Continue reading “Nietzsche on science fiction”


Space-based solar again

Paul Raven @ 10-07-2009

solar eclipseSpace-based solar power is about as science fictional as an energy solution can be, but that doesn’t seem to be stopping people from trying to make it a reality. We mentioned Solaren’s combined energy platform and hurricane killer idea back in April; now here’s PowerSat, who (naturally) have their own unique selling point:

Most proposals for space-based solar have involved a constellation of satellites, each transferring those 17MW to a central unit for transmission back to earth. This adds to the complexity of the system and means at least one satellite has to integrate a very large amount of power. PowerSat hopes to avoid all that. The satellites will receive a pilot signal from the ground and use that to coordinate their energy-carrying return signal to the ground-based receiver. “The satellites act as a radio frequency cloud to create a phase array of phased arrays,” Maness says.

When the microwave signal hits the ground, the transmission from each satellite should be additive—all of which dramatically cuts down the weight and complexity of the hardware that has to be put into orbit.

There are, of course, concerns about the effects of the power transmission beams when they reach the surface, but PowerSat are convinced (after researching thoroughly) that there would be no harm to humans, animals or anything else living. However, the beam would certainly knock out your mobile phone signal – which is a pretty minor flaw, but one that’s bound to create a significant obstacle to PowerSat’s plans… [image by James Jordan]


The romance of steam power returns

Paul Raven @ 09-06-2009

steam valveDespite its association with a bygone era of anachronistic and bulky (but very stylish) technology, steam power is making a comeback thanks to stimulus money from the US government. Combined Heat and Power (CHP) systems are appealing to large organisations because of the efficiency they offer, but the same logic could apply to more domestic situations as well:

Today, most of the time, we make electricity and generate heat in different places. We get our electricity for lighting and power from a central station located far away and transmitted to us through the grid. Heating or cooling, on the other hand, is often accomplished with on-site boilers or electric radiators. Both systems work less efficiently when they stand alone. Together, waste heat generated during the process of making electricity can be scavenged and piped around to provide climate control.

Makes sense, right? It sure does – and it’s environmentally sound as well.

A DOE report released late last year found that CHP was already responsible for reducing American emissions by 248 million metric tons of CO2, which is equivalent to taking 45 million cars off the road. That’s a lot more than wind, solar or any of the other renewables. They have such a big impact because they effectively double the amount of work that we get from burning the same amount of fossil fuel.

With the extra impetus to reduce carbon dioxide emissions to combat global warming, these electric plants that also use their excess heat could experience a lot more growth over the next 30 years. To do so, though, they have substantial challenges to overcome.

For one, many of the regional benefits of CHP are not recognized by existing environmental and utility regulations. Utilities resist CHP systems because they complicate their transmission infrastructure and they say that’s costly. And people have grown used to having their power generated in some far off place and often object to the installation of a power plant nearby.

Ah, good old NIMBYism… but perhaps those complaints will be fainter once the markets have made fossil fuels into ludicrously expensive commodities again. [image by waddie]

It’s interesting to note yet another field of concern and endeavour where the solution might involve a move back from centralised provision to localised. Economics, politics and now energy… is it time for the return of the city-state?


Coal: fuel of the future

Tom James @ 24-04-2009

geological-carbonThe British government has given the go-ahead to a new generation of coal-fired power plants incorporating carbon-capture and storage technologies in a bid to reduce carbon dioxide emissions. Clean coal has been met with criticism and the policy seems just a little bit flaky:

Up to four new plants will be built if they are fitted with technology to trap and store CO2 emissions underground.

The technology is not yet proven and would only initially apply to 25% of power stations’ output.

Green groups welcomed the move but said any new stations would still release more carbon than they stored.

Uh huh. According to UK energy secretary Ed Miliband:

Once it is “independently judged as economically and technically proven” – which the government expects by 2020 – those stations would have five years to “retrofit” CCS to cover 100% of their output.

Kind of a glass quarter-full situation then. And it might not even work. But do check out the details.

[image and articles from the BBC and the Guardian]


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