It’s getting hot in the city. Urban Heat Island Effect ensures that temperatures in city are higher than its surrounding rural areas, even when receiving the same amount of solar radiation. Well, if it gets too hot in the city, why not escape to the off-shore islands? Singapore’s Semakau Island – site of the nation’s landfill – has gained traction as a wildlife hotspot; while St John’s Island and Pulau Sebarok are believed to have strong enough current speeds to potentially power 6,700 flats using tidal turbines. Read more

Eco business.com (12 August 2013):

Some homes in Singapore could be powered by the sea in future – if scientists manage to prove that tidal turbines in nearby waters can help meet the country’s growing electricity needs.

From next month, researchers from Nanyang Technological University (NTU) will survey two sites, one near St John’s Island and another near Pulau Sebarok.

The two locations are believed to have strong current speeds of about 1.2m to 3m per second – enough to generate power from turbines placed on seabeds.

Based on estimates by other researchers, the two spots could house enough tidal turbines to power about 6,700 flats here, said project leader Michael Abundo from the Energy Research Institute at NTU.

The project will involve confirming the estimated tidal current speeds. Sensors will also be left on the seabed for a month to collect data, which will allow the scientists to forecast long-term current speeds.

“Wind and solar energy may be affected by the weather, but tidal currents are very predictable. If you have data from one lunar month or 29.5 days, you can forecast the current every hour for the next year,” said Dr Abundo.

The two sites were selected after ruling out other areas which had maritime traffic, or were aquaculture zones and marine protected areas.

Results from the survey will be ready by the end of the year, and will be used to fine-tune the turbine designs.

Turbines in other countries have been designed for higher current speeds of about 4m per second. The survey will also include a sonar scan to profile the seabed’s slopes, as steep slopes are not suited for most tidal turbines.

This is all part of a larger plan by the institute to map areas where Singapore can tap renewable marine energy. The scientists believe the project is critical because renewable energy from the sea can help quench the country’s growing thirst for electricity.

Singapore consumed about 41,730 gigawatt hours of energy in 2011, up about 10 per cent from 2009. About 80 per cent of its fuel mix for electricity generation today comes from natural gas.

The NTU team had previously estimated that tidal currents in several spots south of Singapore could meet 1.5 per cent of the country’s electricity needs in 2011.

But there are challenges ahead.

The Energy Market Authority has said that marine renewable energy is limited in Singapore as much of its sea space is used for ports, anchorage and shipping lanes. Most funded projects here are also focused on solar energy.

“Singapore should not disregard any energy option that is tappable,” argued Dr Abundo.

“Even if the technology may not yet be widely deployed in Singapore, it could still be used elsewhere in the region, and this would boost Singapore’s reputation for renewable energy research and development.”

Source: www.eco-business.com/

 

By Kate Allen, Science and Technology reporter (17 August 2013):

Bike down a city street on a hot summer night until you pass a park and be rewarded with a blast of cool air.

This, in miniature and in reverse, is an easy way to understand what geographers and climatologists call the Urban Heat Island effect: even if a city and its rural surroundings receive the same amount of solar radiation, the city will be hotter.

But if the Urban Heat Island sounds simple, it masks a host of social thorny ramifications.

In Toronto, there is “almost a perfect overlay between poor areas and hot areas,” says Kevin Behan, deputy director of the Clean Air Partnership, an environmental group.

Mitigating the Urban Heat Island effect — which can be as easy as switching roof colours — is a matter of social justice, many experts say. And as climate change continues to amplify weather extremes, that task is increasingly urgent.

“During the summer, cities are getting a lot warmer,” says Hashem Akbari, an Urban Heat Island specialist at Concordia University in Montreal. “People need to have air conditioning, if they can afford it. If they cannot afford it, they pay for it in different ways” — with their health and sometimes with their lives.

Scientists began noticing the Urban Heat Island effect almost as soon as cities were first industrialized. In London, a chemist and amateur meteorologist named Luke Howard showed in the early 1800s that the heart of the city was an average of 0.9 C hotter than the leafy suburbs of Tottenham, Stratford and Plaistow.

Modern scientists have confirmed that the average temperature difference between an urban heat island and its rural belt is usually 1 C to 2 C but can reach as much as 12 C in extreme cases.

Cities, with their smokestacks and exhaust pipes, produce more heat than the countryside, but they also retain more heat. Concrete, brick and asphalt absorb energy from the sun and radiate it back into the urban atmosphere at night — that’s when the urban heat island effect is most pronounced.

Trees, soil and water, on the other hand, release cooling moisture into their surroundings through the process known as evapotranspiration.

“The areas of Toronto that we know are highly treed — the central areas, like Rosedale, Forest Hill and the ravines — come out looking much cooler than parts of the city that are much more built up,” says Stephanie Gower, a research consultant at Toronto Public Health.

Gower described a heat “doughnut” that rings the city, including those areas of Scarborough and Etobicoke where there is less mature tree canopy.

Even within a small section of the city, the contrast can be extreme. The leafy streets of High Park are separated from the highrise apartment buildings of nearby Parkdale by a mere railway line, but heat-wise the two neighbourhoods are “chalk and cheese,” says Behan.

The Urban Heat Island problem “doesn’t affect everyone equally,” he says.

People who are more vulnerable to heat tend to live where the effect is most amplified or in buildings with no air conditioning.

“Children under 5, people over 65, those without English as a first language, immigrants, even from hot countries, are part of the vulnerable populations in Toronto,” says Behan.

For that reason, city officials take a keen interest in the Urban Heat Island effect. For instance, after a formal recommendation from Toronto Public Health, the city’s Urban Forestry department began using heat vulnerability maps to determine where new trees should be planted first.

In Toronto, it is estimated that heat contributes to an average of 120 premature deaths a year. But that average can mask extremes — deaths spike during very hot summers.

Last year, Concordia’s Akbari wrote a study that examined the effect of changing roofs from black, which absorbs sunlight, to white, which reflects it back into space.

In simulations, Akbari found that every one percentage point increase in a square metre of urban reflectivity could offset seven kilograms of carbon dioxide.

If every city in hot and temperate climates changed its roofs and road surfaces to reflective colours, Akbari calculated the effect would be the equivalent of taking every car off the road for the next 50 years.

Green roofs also significantly offset the urban heat island effect, turning a heat-absorbing surface into one that participates in evapotranspiration.

“I’m not only interested in the science,” says Akbari. “I would measure my success by the amount of energy and number of peoples’ lives saved.”

Source:  www.thestar.com/news/

 

By Francesca de Châtel for CNN (26 July 2007):

Semakau now attracts diverse wildlife, like this great-billed heron.

LONDON, England (CNN) — Garbage dumps are generally not associated with thriving coral reefs, vast mangrove plantations and rare bird species.

Yet on Pulau Semakau off Singapore, this is exactly what you will find: just beside a secluded ecological zone that harbors dozens of rare plant, bird and fish species lies the world’s first ecological offshore landfill.

Located 8 kilometers south of Singapore and covering an area of 3.5 square kilometers, the Semakau Landfill was designed by engineers and environmentalists at Singapore’s National Environment Agency (NEA). It consists of two small islands that have been connected by a rock embankment. The area inside the landfill is divided into 11 bays, known as ‘cells’, which are lined with thick plastic and clay to prevent any harmful material from seeping into the sea.

Since the landfill was put into use in 1999, four of the 11 cells have been filled, covered with earth and planted with grass.

The landfill, which cost around $400 million, can hold up to 63 million cubic meters of rubbish, enough to satisfy Singapore’s waste disposal needs until 2040.

Clean and odor-free

What distinguishes Semakau from other landfills is that it is clean and free of smell. Two thirds of the material that comes to Semakau has passed through one of the city’s four incinerators, reducing it to approximately ten percent of its original volume. Waste from construction material is also processed, while toxic waste like asbestos is packaged in such a way that it cannot leak into the surrounding environment.

Two mangrove groves that were destroyed when the embankment was built have been replanted near the landfill and today they serve as biological indicators for the local environment. If they were to start dying, it would be seen as a sign that harmful material had leaked from the landfill.

Scientists expected that some of the mangroves would not survive the relocation, but today they cover 1.4 square kilometers around the island and even have to be cut back in places — a sign that the landfill is indeed leak-proof.

Flourishing wildlife

Together with the island’s other ecosystems such as seagrass meadows, coral reefs and sandy shores, the mangroves serve as a habitat for a variety of birds, fish and plants.

The decision to build a landfill off Semakau was taken in the 1990′s when the previous landfill on the main island had nearly reached capacity. “As land is scarce in Singapore, it was decided from the outset that the new sanitary landfill in the smaller islands would be designed as an environmentally friendly facility which would be used to meet Singapore’s land use needs when it was eventually filled up and closed,” the NEA explained in an official statement. Every effort was made to minimize the impact on the local environment so that the area beside the landfill, which always had a rich flora and fauna, has remained intact.

“Great effort went into making sure that the impact of the landfill on Pulau Semakau’s biodiversity was minimized. In fact, biodiversity remains high and we have not lost a single species because of the landfill,” says Wang Luan Keng, an education and research officer at the Raffles Museum of Biodiversity Research (RMBR) in Singapore.

New species

She adds that as the island’s various ecosystems continue to flourish, scientists are still discovering new species on Semakau.

In July 2005, the government decided to open the western part of Semakau up to the public for recreational purposes. Today there are guided nature walks along the island’s coast, while sports fishing and bird watching associations also organize special excursions to the island.

“When we do the tours around the island, we have a powerful message,” says Ria Tan, an associate at the RMBR and owner of a popular Web site, wildsingapore.com. “We tell people: ‘Look how beautiful this is, and imagine what could be destroyed if the landfill had to be expanded.’ This makes them think and when they go home they are more careful about how they deal with waste.”

Rich biodiversity

Thus, the Semakau Landfill project has inadvertently turned into more than just a trash dump; it is becoming an educational project and could serve as a model for sustainable urban development around the world. “The rich biodiversity around the sanitary landfill shows that development and environmental protection can co-exist and need not be mutually exclusive,” says the NEA.

“It is of course a compromise, but in the context of urban living I think it is a good one. Some nature lovers criticize the project, but in the end we have to throw our rubbish somewhere and this is a good solution,” says Tan.

Wang agrees. “I see Semakau Landfill as a great way of striking a balance between the need of urban development and nature conservation.”

Source: www.edition.cnn.com