Posts Tagged‘supercritical’

Life Without Water.

All life as we know it has one basic need: water. The amount of water required to sustain life is a highly variable thing, from creatures that live out their whole lives in our oceans to others who can survive for months at a time without a single drop of water. However it would be short sighted of us to think that water was the be all and end all of all life in our universe as such broad assumptions have rarely panned out to be true under sustained scrutiny. That does leave us with the rather puzzling question of what environments and factors are required to give rise to life, something we don’t have a good answer to since we haven’t yet created life ourselves. We can study how some of the known biological processes function in other environments and whether that might be a viable place for life to arise.

Supercritical CO2 Extraction

Researchers at the Washington State University have been investigating the possibility of fluids that could potentially take the place of water in life on other planets. Water has a lot of properties that make it conducive to producing life (as we know it) like dissolving minerals, forming bonds and so on. The theory goes that should a liquid have similar properties to that of water then, potentially, an environment rich in said substance could give rise to life that uses that liquid as its base rather than water. Of course finding something with those exact properties is a tricky endeavour but these researchers may have stumbled onto an unlikely candidate.

Most people are familiar with the triple point of substances, the point where a slight change in pressure or temperature can change it from any of its one three states (solid, liquid, gas) instantly. Above there however there’s another transition called the supercritical point where the properties of the gaseous and liquid phases of the substance converge producing a supercritical fluid. For carbon dioxide this results in a substance that behaves like a gas with the density of its liquid form, a rather peculiar state of matter. It’s this form of carbon dioxide that the researchers believe could replace water as the fluid of life elsewhere, potentially life that’s even more efficient than what we find here.

Specifically they looked at how enzymes behaved in supercritical CO2 and found that they were far more stable than the same ones that they had residing in water. Additionally the enzymes became far more selective about the molecules that they bound to, making the overall process far more efficient than it otherwise would have been. Perhaps the most interesting thing about this was that they found organisms were highly tolerant of this kind of fluid as several bacteria and their enzymes were found to be present in the fluid. Whilst this isn’t definitive proof for life being able to use supercritical CO2 as a replacement for water it does lend credence to the idea that life could arise in places where water is absent.

Of course whether that life would look like anything we’d recognise is something that we won’t really know for a long time to come. An atmosphere of supercritical C02 would likely be an extremely hostile place to our kind of life, more akin to Venus than our comfortable Earth, making exploration quite difficult. Still this idea greatly expands our concept of what life might be and what might give rise to it, something which has had an incredibly inward view for far too long. I have little doubt that one day we’ll find life not as we know it, I’m just not sure if we’ll know it when we see it.

CSIRO Goes Supercritical on Solar Thermal.

Whilst I might tend towards nuclear being the best option to satisfy our power needs (fission for now, fusion for the future) I see little reason for us to not pursue renewable technologies. Solar and wind have both proven to be great sources of energy that, even at the micro scale, have proven to be great sources of energy that have great returns on investment. Even the more exotic forms of renewable energy, like wave power and biomass, have proven that they’re more than just another green dream. However the renewable energy which I believe has the most potential is concentrated solar thermal which, if engineered right, can produce power consistently over long periods of time.

CSIRO Solar Thermal Heliostats

Solar thermal isn’t a recent technology with functioning plants operating in Spain¬†since 2007. However compared to most other forms of power generation it’s still in its nascent stages with the numerous different approaches being trialled to figure out how to best set up and maintain a plant of this nature. This hasn’t stopped the plants from generating substantial amounts of power in the interim however with the largest capable of generating 392MW which might not sound like a lot when you compare it to some coal fueled giants but they do it without consuming any non-renewable fuel. What’s particularly exciting for me is that our own CSIRO is working on developing this technology and just passed a historic milestone.

The CSIRO maintains an Energy Center up in Newcastle where they develop both energy efficient building designs as well as renewable energy systems. Of the numerous systems they have there (including a traditional photovoltaic system, wind turbine and gas fired microturbine) are two concentrating solar thermal towers capable of generating 500KW and 1MW respectively. Their larger array recently generated supercritical steam¬†at temperatures that could melt aluminium, an astonishing achievement. This means that their generating turbines can operate far more efficiently than traditional subcritical designs can, allowing them to generate more power. Whilst they admit they’re still a ways off a commercial level implementation the fact they were able to do it with a small array is newsworthy in itself as even the larger plants overseas haven’t achieved such a goal yet.

Looking at the designs they have on their website it seems their design is along the traditional lines of solar thermal, using the steam created to directly feed into the turbine to generate electricity. This, of course, suffers from the age old problem that you only generate power when the sun is shining, limiting its effectiveness to certain parts of the day. The current solution to this is to use a heat storage medium, molten salts being the currently preferred option, to capture heat for later use. Thankfully it seems the CSIRO is investigating different heat storage mediums, including molten salts, to augment their solar thermal plant with. I’m not sure if it would be directly compatible with their current set up (you usually heat the molten salts directly and then use them to generate steam down the line) but it’s good to see that they’re considering all aspects of solar thermal power generation.

Considering just how much of Australia is barren desert that’s bathed in the suns radiation solar thermal seems like the smart choice for generating large amounts of power without the carbon footprint that typically comes along with it. The research work that is being done at the CSIRO and abroad means that this technology is not just an environmentalist’s dream, it’s a tangible product that is already proving to have solid returns on investment. If all goes well we might be seeing our first solar thermal plant sooner than you’d think, something I think all of us can get excited about.