Thermosiphon System

Basically a thermosiphon system uses the natural laws of nature to operate.

Hot water is less dense than cold water. Actually water is at its most dense at 4 degrees

centigrade, just before freezing.

As we all learnt in basic science at school, when we heat water the lighter hot water "floats" to the top and the denser cold water "sinks" to the bottom.

In the example above we use a bunsen burner to heat the water, but the sun can act like a bunsen burner.

When we position one of our systems externally we are relying on the sun to heat water held in the collector unit, as that water temperature rises, so the hot water moves into the cylinder (geyser), that is specially designed to store hot water efficiently.

Have a look at some examples here in sunny SA.

Please don't hesitate to contact us with any further questions

info@greencon.co.za

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Climate Effects on Crop Yields

While news reports and disaster movies remind us about tipping points for Arctic melt and sea level rise, some things closer to home get less attention. Take food supply: new modelling studies show that there are climate tipping points here too, beyond which crop yields will collapse.

Wolfram Schlenker at Columbia University, New York, and Michael Roberts at North Carolina State University in Raleigh used a high-resolution dataset of weather patterns from 1950 to 2005 to discover how yields of three key US crops would respond to increasing temperatures.

"The single best predictor of a year's yield is the amount of time temperatures exceed about 29 °C and the extent to which they do so," they say.

"Below this, warmer temperatures are beneficial for yields, but the damaging effects above 29 °C are staggeringly large."
Maize massacred

Overall, the results suggest that yields of maize, cotton and soybean drop by roughly 0.6 per cent for each "degree-day" spent above 29 °C.
A degree-day is a measure devised by the team to indicate by how much 29 °C is exceeded and the time spent above that threshold. At present, agricultural regions across the US spend an average of 57 degree-days above 29 °C during the growing season.

That's likely to rise as the world warms. Using a model of future climate change the researchers found that the number of degree-days above 29 °C in a growing season could rise to 413 by the end of the century if we do not cut greenhouse gas emissions. This would cause maize yields to fall by 82 per cent.

Even if we reduce emissions by 50 per cent by 2050 relative to 1991 levels – a target that governments are struggling to agree on – yields could still fall by between 30 and 46 per cent.
"These estimates of yield loss are amongst the best we have," says David Bohan, head of the Ecosystem Dynamics and Biodiversity group at Rothamsted Research, UK.
States of hunger

The US is the world's largest producer and exporter of crops, accounting for around 40 per cent of global maize and soybean production.

"If US yields go down a lot, it could drive up prices of staple food commodities all around the world", say the researchers. "Almost surely the poor would suffer far more that the US would."

David Pimentel at Cornell University in Ithaca, New York, argues that curbing biofuel production would tackle starvation and high food prices far quicker than curbing greenhouse gas emissions. "Some 66 per cent of the world population malnourished, yet the US turns 33 per cent of its corn crops into biofuels," he says.

Source: New Scientist

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Developers Putting "Green" into their investments

Joe VanBelleghem isn't afraid to put his money where his mouth is. After reading the influential book "Natural Capitalism" by Paul Hawken and others, the Canadian real-estate developer committed to building projects that embraced the triple bottom line approach advocated for in the book: People, planet and profits.
So when VanBelleghem's firm, Victoria, Canada-based Windmill West, and its co-developer, Vancity Credit Union, bid on a 1.3 million square-foot, mixed-use sustainable community development near Victoria, the team included in the proposal penalties for themselves totaling CAN $1 million (about US $923,000) if they didn't achieve stringent green building standards.
The CAN $500 million project, called Dockside Green, is about 35 percent complete and still has another 7 years to go. But its signature residential phase, known as Synergy, was completed late last year and is the highest-scoring Leadership in Energy and Environmental Design (LEED) certified project in the world according to VanBelleghem, achieving “platinum” for its sustainable design. The development includes on-site renewable energy and wastewater treatment; energy-saving features like Energy Star appliances, heat recovery ventilators, and double-glazed windows; rooftop gardens; and a series of man-made ponds across the former brownfield site that have attracted ducks and otters.
“This is an urban site where we’ve really brought nature back,” VanBelleghem said. “It’s a beautiful development. It’s a detailed, complex way of thinking about how we should build our communities.”

Synergy (pictured above, credit: Windwill West), with a price tag of CAN $23.6 million, encompasses four detached buildings over a common under-ground parking structure. The four buildings include 95 residential units—ranging from 560 square-foot condos to 1754 square-foot, three-bedroom townhouses—and some commercial spaces on the ground floor.
One of Dockside Green’s most impressive green features is its on-site biomass heat generation plant (see drawing below, credit: Windwill West), which currently provides heat and hot water to Synergy and eventually will provide it to all 26 planned buildings in the development. The CAN $7 million plant relies on gasification technology from Vancouver-based Nexterra Systems to convert biomass into a clean burning synthetic gas, or syngas, which is used to generate heat. The plant is fueled by 1.1 tons of locally sourced wood waste per hour at peak capacity, cranking out 7.7 million Btus every 60 minutes.

Largely thanks to this renewable energy, Dockside Green is to be a carbon neutral development. The biomass plant will provide about 75 percent of its energy needs and the remaining 25 percent (for electrical power) will be made carbon neutral through the purchase of green power certificates. But renewable energy generation isn’t the whole story. Synergy and the other buildings in the development are on track to achieve this carbon neutral goal largely because of the design team’s commitment to energy efficiency.
“We took energy very seriously,” said Robert Drew, Synergy’s project architect and an associate principal with the architectural firm Busby Perkins+Will, which created the master plan for Dockside Green. “We wanted to make sure we developed an envelop for the building that contributed to energy demand reductions.”

Synergy’s four detached buildings have roofs and walls that are twice as insulated as conventional construction and their windows are about 50 percent better. Each residential unit has a high-efficiency fan coil for heating, sub-meters for both water and power, and Web-based energy-use monitoring. These features and others are projected to contribute to a more than 50 percent reduction in energy demand compared with conventional construction.
Synergy and the other buildings in Dockside Green will also benefit from on-site wastewater treatment, which will allow the development to recycle much of its water for irrigation and toilet flushing. These features plus low-flow water fixtures mean that residential units should use about two-thirds less water than conventional construction.

The design team also made a point of carefully selecting materials that had minimal environmental impact in the way they were harvested or manufactured, according to Drew. They required paints and other materials with low or no volatile organic compounds.

Dockside Green’s sustainable credentials have not gone unnoticed. Most recently, last month it was recognized by the Clinton Climate Initiative along with 15 other projects worldwide as a large-scale urban undertaking that demonstrates that cities can grow in ways that are “climate positive.” Dockside Green also has won awards from the American Institute of Architects’ Committee on the Environment, the Canadian Urban Institute, the Architectural Institute of British Columbia and more.

About 95 percent of Synergy’s residential units are sold or leased. VanBelleghem said that in the current highly competitive real-estate market, he’s not selling Synergy units at a premium. But he said his residences are selling faster than their less-green competitors because people perceive Synergy as having “better value and better quality.” VanBelleghem said that building such a sustainable development does cost more than conventional construction—he wouldn’t say how much more—but he said that the margins are consistent with other real-estate projects.
“We spend about half the amount of money in marketing because of all the media coverage we get,” he said. “We get approvals more quickly; we’ve been able to increase the housing density and height limits over what the code would normally allow; and we’ve worked cooperatively with the city and environmental groups.”

But as impressive as Dockside Green is, VanBelleghem is already planning an even bigger project. With a rough budget of about CAN $1 billion, VanBelleghem is working on a mixed-use community outside of Victoria that embraces the same sustainability principles as Dockside Green but is about three times its size. No word yet if the Canadian developer will include a cash penalty in this new proposal if the project doesn’t achieve the highest green building standards. But based on the success Dockside Green, that shouldn’t be a worry for him.

Source: Renewable Energy World

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