An eco-city in Portugal that its makers are aiming to build by 2015 takes its cues from the nervous system
If today's cities were living things, they would be monsters, guilty of guzzling 75% of the world's natural resources consumed each year.
Now a more benign urban creature is set to emerge. The planned city of PlanIT Valley, on the outskirts of Paredes in northern Portugal, is aiming to be an environmentally sustainable city. And, just like an organism, it will have a brain: a central computer that regulates everything from its water use to energy consumption.
Various eco-cities are in the pipeline, but this could be the first to be fully built - by 2015 - and could open its doors as early as next year. While Masdar City in Abu Dhabi welcomed its first inhabitants this month, it will not be completed until at least 2020. And the development of Dongtan near Shanghai in China has not even got off the ground yet, following financial and political difficulties.
Like other sustainable cities, PlanIT Valley will treat its own water and tap renewable energy. Buildings will also have plant-covered roofs, which will reduce local temperature through evapotranspiration, as well as absorbing rainwater and pollutants.
Yet that is where the similarities with other eco-cities end, according to its makers Living PlanIT based in Paredes. For a start, PlanIT Valley will be built closer to existing transport links than the likes of Masdar. More significantly, its "brain" will use data collected from a network of sensors akin to a nervous system to control the city's power generation, water and waste treatment (see "Brains and nervous system"). It's a kind of "urban metabolism", says Steven Lewis, chief executive of Living PlanIT.
While this network of sensors sounds expensive, the cost of installing it will be offset by using more efficient building techniques. "Because we have reduced the cost of the building, we can spend a bit more on the technology," says Lewis. For example, software used to design cars and aircraft was used to create the architectural plans.
What's more, the buildings are being prefabricated so that when construction begins at the end of 2010 it should be cheaper and quicker. The hexagonal shape of the buildings was chosen to make efficient use of space.
The city's technologies could be retrofitted to existing towns. This would be a good idea, says Simon Joss of the University of Westminster in London. Still, he adds that the 2015 completion date may be optimistic, and that the project's success cannot be determined until people move in. "It's about developing a community," he says.
Brain and nervous system
PlanIT Valley will have its own artificial nervous system to control its water and energy consumption.
Sensors in every building will measure occupancy, temperature, humidity and energy use. This information will be fed to a central "brain", along with information on energy production from photovoltaic devices and wind turbines, as well as water used and waste produced.
The brain can then use this information to control each aspect of the city. For example, if sensors show that the water level in one building's storage tank is low, the system will move water from another building where there is an excess.
It will also use weather forecasts to predict when days will be cloudy, which will reduce the amount of energy generated by the city's photovoltaic devices. It would then switch to using stored energy, in the form of ice produced by excess electricity on sunnier days, to provide chilled water for the building's air conditioning systems, for example.
An urban data centre will process all the information gathered by the system's sensors - around five petabytes each day. To prevent a problem hitting the data centre and knocking out the control of the entire city, each building will also have sufficient computing power to function on its own.
To save on heating bills, the hot air produced by the data centre will be used to heat other buildings.
Only 3% of the water consumed in a city is used for drinking and cooking, so buildings in PlanIT Valley will re-use as much water as possible.
Cooking water can be collected and reused for flushing toilets. Similarly, rainwater will be collected by tanks on the "green roofs" of buildings and then filtered by the plants to remove pollutants. A series of lagoons in the city's central park will use reeds, bamboo and other plants to filter waste water, making it suitable for reuse as "grey" water in toilets and irrigation.
Once these plants have grown, consuming carbon dioxide as they do so, they will be cut down and used to produce biofuel, with a new batch planted to replace them.
Eyes and ears
If a child goes missing, its parents could turn to the city's eyes: a network of cameras connected to software.
An application called "Find my Kid" will allow parents to locate children who wander off at the shopping centre, for example. Software first checks if the person asking for the information has a right to know the answer - a father, say - and then automatically searches footage from security cameras to identify the child based on a description of their clothing and appearance.
Find my Kid is one example of the "Place Apps", which Living PlanIT hopes to develop by collaborating with software firms. They could be available at computer terminals dotted around the city or in smartphones. Other possible apps could help inhabitants find a parking space, for example.
The apps could also use microphones to listen for sounds. A Place App designed to run in the meeting room of an office building could identify the topic of the meeting from the use of certain spoken keywords. Then it could suggest potential collaborators within or outside the company, Lewis proposes.
This city will thrive by eating its trash.
On average, cities divert only 5% of trash for recycling or energy production. That figure will be 80% for PlanIT Valley.
Human and organic waste will be used to generate electricity. An anaerobic digester will use enzymes to stimulate microbes to digest such waste, producing chemicals that can be fermented and distilled into biofuels to run the city's cars or to generate electricity. The process also generates by-products such as amino acids and vitamin B12, which can be sold to the pharmaceutical industry.
Dishwasher-sized digesters are also being developed for homes. Fed by a tablet containing enzymes, these would process food and human waste to generate biofuel, which can then be burned to generate electricity.
Of the remaining landfill waste, any aluminium will be extracted and used in industrial chemical reactions to generate hydrogen, which could be used as a fuel to power vehicles.
Finally, a biomass reactor will heat whatever waste cannot be recycled to 400°C without oxygen, a process known as pyrolysis, to generate energy and biochar, which can be used as a fertiliser.
Residents will not be asked to separate plastic and glass in their trash. All waste is fed through the central digester, which cleanses materials of organic contamination, before they are separated. That means more can be recycled.
This article first appeared in New Scientist.