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Daily Archives: May 9, 2013
A trio of companies has joined forces to develop a truck cabin air conditioning system that uses solar energy generated from panels on the trailer’s roof area for its power.
ICL Co Ltd, Mitsubishi Chemical Corp and Nippon Fruehauf Co Ltd co-developed the air conditioning system and the companies plan to conduct field tests of the i-Cool Solar system shortly. If the trials go well, we could see these units on highways in spring 2012.
The “i-Cool Solar” system stores electricity via the photovoltaic panels in special on-board batteries and uses the stored energy to power the cabin air conditioner when the truck is idle.
The system is made up of the i-Cool air conditioner from ICL, the installation mount for the PV panels from Nippon Fruehauf’s, and the PV cell modules from Mitsubishi Chemical.
The companies claim the i-Cool Solar can save roughly 1.8 liters of light oil per hour when the truck is not moving and reduce fuel consumption by about 1 percent when the truck is moving (based on calculations made on a standard 10 ton truck).
This results are fuel savings of around 1,500 liters of light oil per year.
The i-Cool Solar unit also makes it possible to operate other equipment on trucks, such as moving up and down the tail gate. The air conditioning system can also reduce the over-discharge of the storage battery which increases its lifespan.
A smaller version for use in cars is also in development.
According to a team of researchers at the UC San Diego Jacobs School of Engineering, the solar panels sprouting on increasing numbers of residential and commercial rooftops around the world aren’t just generating green electricity, they’re also helping keep the buildings cool. The news that letting photovoltaic panels take the solar beating will reduce the amount of heat reaching the roof shouldn’t come as much of a surprise, but the fact no one has thought to quantify just what the effects of rooftop solar panels on a building’s temperature are is a little baffling.
Although the observations for the study were taken over the short period of three days in April this year, Jan Kleissl, a professor of environmental engineering at the UC San Diego, and his team believe they the first peer-reviewed measurements of the cooling benefits provided by solar photovoltaic panels. And despite the limited time, Kleissl is confident his team developed a model that allows them to extrapolate their findings to predict cooling effects throughout the year.
Using a thermal imaging camera, the team gathered data on the roof of the Powell Structural Systems Laboratory at the Jacobs School of Engineering, which is equipped with tilted solar panels as well as solar panels that are flush with the roof, while some of the roof is not covered by any solar panels at all.
They determined that during the day, the panels reduced the amount of heat reaching the roof by about 38 percent and as a result the building’s ceiling was five degrees Fahrenheit (three degrees Celsius) cooler than the ceiling under an exposed roof. Tilting panels with a gap between the building and the solar panel that allowed air to circulate were found to provide a bigger cooling effect than flush solar panels. Kleissl and his team say the amount saved on cooling the building amounts to a five percent discount on the price of the solar panels over their lifetime.
Additionally, the panels help hold heat in at night to cut heating costs in winter. On the flip side, however, the panels would also keep the sun from heating up a building in winter and would keep the heat accumulated in the building during the day in summer from escaping at night. Therefore the effects effectively cancel each other out in many climates.
“There are more efficient ways to passively cool buildings, such as reflective roof membranes,” said Kleissl. “But, if you are considering installing solar photovoltaic, depending on your roof thermal properties, you can expect a large reduction in the amount of energy you use to cool your residence or business.”
Created by U.S. architectural firm Brooks + Scarpa, the recently completed Green Dot Animo Leadership High School in Inglewood, Los Angeles, wears its green heart very much on its sleeve. The new public school for 500 students is characterized by a large south facing façade covered with 650 solar panels, which not only help shield the building from the sun but also capture an estimated 75 percent of the energy needed to power the school.
According to Brooks + Scarpa the school’s combined sustainable strategies “will reduce carbon emissions by over 3 million pounds (1.36 million kilograms),” which translates to the equivalent of the annual emissions from more than 1000 cars.
In a design that also incorporates passive solar principles, the architects chose to move away from creating a traditional large block-like structure, instead choosing to build the school around a large internal courtyard. Benefiting from the Californian temperate climate, this landscape naturally makes its way into the school’s protected open-air lobby. This design helps to improve the amount of natural light and ventilation that can enter the structure, limiting the need for additional interior lighting and air conditioning.
Where the exterior is not covered with solar panels, ribbed screens have been installed which visually connects the school with its external environment and enable staff members to control how much light can enter the building.
The 53,500 square foot (4970 sq m) Green Dot school was completed at a cost of US$17.3 million.
A US school has cut a six-figure sum from its winter energy bill by replacing its oil-burning boiler with woodchip biomass ones. The switch has reduced the school’s carbon footprint by between 35 and 45 percent. The boilers are housed in a brand new green-roofed building which has become only the third LEED-certified power facility in the US.
Unlike the oil-fired boiler they have replaced, the biomass burners combust locally-sourced woodchip, which, though not a wholly clean source of energy, is cleaner than using oil. An electrostatic precipitator removes 95 percent of particulates from emissions before entering the atmosphere.
Because the woodchip comes from FSC-certified forests, it’s effectively a renewable source of energy as the forests are managed to maintain their stock. The International Panel on Climate Change goes so far as to argue that appropriately sourced woodchip is a carbon neutral fuel for this very reason. The carbon lost to the atmosphere when the woodchip is burned is gradually put back as replacement trees grow.
There are green roofs and there are green roofs. The former, best written in the sort of quotation marks that express dubiousness, are often little more than a thin shrubbery planted apologetically in the corner of a roof terrace. The latter are almost lush undulating meadows in comparison, and create the impression that the building has been slipped into the landscape like a letter into an envelope – when viewed from a favorable angle at least. It’s firmly in this category that the new biomass building at the Hotchkiss School in Connecticut belongs.
As one should expect from a green roof, this one serves more than aesthetic purposes. Bioswales, specially designed sloping channels, combine with rain gardens to slow and filter rainwater before it enters the ground.
The Hotchkiss School reports that between mid-October and the end of December, nearly half of the system’s winter operating period, the school slashed more than US$350,000 from its energy bill.
Lockheed Martin has been getting its feet wet in the renewable energy game for some time. In the 1970s it helped build the world’s first successful floating Ocean Thermal Energy Conversion (OTEC) system that generated net power, and in 2009 it was awarded a contract to develop an OTEC pilot plant in Hawaii. That project has apparently been canceled but the company has now shifted its OTEC sights westward by teaming up with Hong Kong-based Reignwood Group to co-develop a pilot plant that will be built off the coast of southern China.
OTEC uses the natural difference in temperatures between the cool deep water and warm surface water to produce electricity. There are different cycle types of OTEC systems, but the prototype plant is likely to be a closed-cycle system. This sees warm surface seawater pumped through a heat exchanger to vaporize a fluid with a low boiling point, such as ammonia. This expanding vapor is used to drive a turbine to generate electricity with cold seawater then used to condense the vapor so it can be recycled through the system.
Tropical regions are considered the only viable locations for OTEC plants due to the greater temperature differential between the shallow and deep water. Unlike wind and solar power, OTEC can produce electricity around the clock, 365 days a year to supply base load power. OTEC plants also produce cold water as a by-product that can be used for air conditioning and refrigeration at locations near the plant.
Despite such advantages, and even though demonstration plants were constructed as far back as the 1880s, there are still no large-scale commercial OTEC plants in operation. This is largely due to the costs associated with locating and maintaining the facility off shore and drawing the cold water from the ocean depths. But the time may finally be right.
With the shelving of the Hawaii OTEC pilot plant, the 10 MW prototype offshore plant will be the largest planned OTEC project to date. Like the Hawaii project, which was also to be a 10 MW facility, the China OTEC plant is designed to pave the way for higher capacity plants ranging from 10 to 100 MW.
The plant is to be built off the coast of southern China to supply 100 percent of the power needed for a large-scale green resort community being developed by Reignwood Group. The new resort is planned as Reignwood’s first net-zero community, with the company also currently developing two large-scale low-carbon resorts and others planned for key locations in China.
Lockheed Martin and Reignwood will begin concept design of the sea-based prototype plant this year with construction due to begin next year. Once it is up and running, the two companies plan to use the knowledge and experience gained over the course of the project to improve the design of additional commercial-scale plants.
The companies claim each 100 MW OTEC facility could produce the same amount of energy in a year as 1.3 million barrels of oil and decrease carbon emissions by half a million tons. Assuming oil trading at near US$100 a barrel, they estimate fuel savings from one plant could exceed $130 million a year.
The video below from Lockheed Martin describes the OTEC process.
Ordinarily seen as a waste product, the husks of sunflower seeds could be used to make concrete, according to research out of Turkey. Not only are the husks a sustainable source of aggregate, it’s claimed that the resulting concrete is more resistant to cracking during post-freeze thaws.
However, the researchers report that with greater concentrations of husk, the concrete would only be suitable for use as an insulating material. Lower husk density results in a lightweight concrete that could conceivably be used for construction purposes, though the researchers suggest this should be restricted to agriculture buildings a single story tall.
Having a high calorific value sunflower seed husks can also be formed into pellets for use as a biomass fuel.
The research was carried out by Can Burak Sisman and Erhan Gezer, engineers at Turkey’s Namik Kemal University. The research appeared in the International Journal of Environment and Waste Management.
While we wait for affordable multi-junction solar cells that are pushing past the 40 percent conversion efficiency mark to make it out of the lab and onto our roofs, we have to make do with standard commercial silicon cells that currently max out at around 19 percent. A team from the University of New South Wales (UNSW) in Australia has found a way to improve the quality of low-grade silicon, enabling higher efficiency solar cells to be produced from cheaper, low-grade silicon.
It’s been known for several decades that hydrogen atoms can be introduced to help correct the efficiency-reducing defects and contaminants found in lower-grade silicon. However, researchers have had limited success in controlling the hydrogen to maximize its benefits. The solution found by the UNSW team relates to controlling the charge state of the hydrogen atoms.
Hydrogen atoms can exist in a positive, negative or neutral charge state, which determines how well they can move around the silicon and their reactivity, which is important to help correct the defects. The researchers say that by controlling the charge state, it will be possible to achieve higher efficiencies using lower-cost, low-grade silicon.
“We have seen a 10,000 times improvement in the mobility of the hydrogen and we can control the hydrogen so it chemically bonds to things like defects and contaminants, making these inactive,” says Scientia Professor Stuart Wenham from the School of Photovoltaics and Renewable Energy Engineering at UNSW. “This process will allow lower-quality silicon to outperform solar cells made from better-quality materials.”
Wenham expects to achieve efficiencies of between 21 and 23 percent using this new technique, which was patented by the UNSW team earlier this year. The researchers have attracted the interest of industry partners interested in commercializing the technology, and they are working with manufacturing equipment companies to introduce it into solar cell manufacturing processes.
Source : UNSW