Hot Where it Matters, Cool When its Needed
Colin Maidment at London South Bank University is leading a research effort to investigate more environmentally friendly air-conditioning and refrigeration systems. One option, ironically, is to use carbon dioxide to replace the synthetic HFC refrigerants used in such systems and using the heat generated by CO2-based air-conditioning systems and fridges in supermarkets, for example, to provide hot water for nearby homes.
By Helen Knight in New Scientist (27 July 2010):
Green machine is our weekly column on the latest advances in environmental technologies
Will people’s environmental intentions wither in a heatwave? With much of the US, eastern Europe and Asia sweltering, it may be tempting to crank up the air conditioning to make homes and offices more tolerable.
That would be bad news for the planet, with aircon playing a significant role in the greenhouse-gas emissions produced by residential and commercial property – roughly 10 per cent of the world’s total emissions, says Graeme Maidment at London South Bank University.
“With global warming that will tend to increase even further, because people will use more air conditioning, while existing systems will have to work harder,” he says.
Rebirth of the cool
Maidment is leading a research effort, funded by the UK’s Engineering and Physical Sciences Research Council, to investigate more environmentally friendly air-conditioning and refrigeration systems. One option, ironically, is to use carbon dioxide to replace the synthetic HFC refrigerants used in such systems, he says: such gases can have around 4000 times the global warming potential of CO2. Around 2 per cent of the UK’s greenhouse gas emissions are attributed to them, says Maidment.
In conventional vapour-compression systems used by aircon units, the refrigerant is compressed and condensed and then expanded and evaporated to cool the room. The heat generated in the compression phase is normally radiated into the air outside the building.
Compressing CO2 generates much higher temperatures than HFCs – around 150 °C compared with around 60 °C. So Maidment and colleagues are investigating the idea of using the heat generated by CO2-based air-conditioning systems and fridges in supermarkets, for example, to provide hot water for nearby homes.
Meanwhile, Matt Poese and colleagues at Pennsylvania State University in University Park are developing an HFC-free air conditioning system based on sound.
The team uses a linear motor to move a loudspeaker-type plate back and forwards, generating a sound wave in helium gas – which doesn’t add to the greenhouse effect. The sound waves create areas of compression and expansion within the gas, causing it to alternately heat up and cool down, says Poese. “It’s like a sponge – the gas sucks up heat in one location and then gets transported by the sound wave to another location where the heat gets squeezed out of the gas,” he says.
The team have previously built a fridge for ice-cream maker Ben & Jerry’s based on this so-called thermoacoustic technology. They say they can scale it up for use in air conditioning, and aim to build 3.5-kilowatt devices – equivalent to a basic home model – which could be dotted around buildings. Having several units could reduce the energy used by air-conditioning systems by only cooling those rooms currently in use, says Poese.
Others are also looking at refrigerants that don’t warm the atmosphere. One of these is a mixture of ammonia and water. Srinivas Garimella at the Georgia Institute of Technology in Atlanta is developing a system in which external heat is used to boil off ammonia vapour from a solution. The ammonia circulates through a condenser and then an evaporator, where it provides the cooling, before being reabsorbed by the water.
Known as absorption refrigeration, the technology was invented before today’s vapour compression systems, but it is bulky, requiring multiple heat exchangers, and so has mostly been used to cool only large buildings such as hospitals and universities.
Garimella has got around this problem by developing micro-scale heat exchangers, in which the solution flows through channels only 0.5 millimetres in diameter, taking advantage of the high heat-transfer efficiencies at this scale. His team have so far developed a book-sized prototype that generates the equivalent cooling to a 300 watts system, and plan to increase the cooling power of the device further with funding from the US Advanced Research Projects Agency – Energy.
Since the process is driven by heat rather than electricity, it could reduce greenhouse-gas emissions even further by using energy-efficient sources of heat. Air conditioning could be combined with solar power – which has one obvious advantage, says Maidment. “When the sun shines, you need air conditioning.”
Archive for the ‘Express 119’ Category
Hot Where it Matters, Cool When its Needed
Sugar to Sweeten Up the Bitter Energy Supply Pill
Victoria’s “exceedingly ambitious” white paper recognises that owners of power stations must be compensated if they are forced to close early, but it’s no substitute for a trading scheme and is silent on a range of crucial issues, according to Energy Supply Association of Australia CEO Brad Page. Meanwhile, Queensland University of Technology scientist Dr Slade Lee says sugar cane production methods could hold the key to making ethanol cheaper.
CE Daily (28 July 2010)
Victoria’s “exceedingly ambitious” white paper recognises that owners of power stations must be compensated if they are forced to close early, but it’s no substitute for a trading scheme and is silent on a range of crucial issues, according to Energy Supply Association of Australia CEO Brad Page.
The paper offers no details on how much abatement each element will deliver and at what carbon price, he told CE Daily.
Reducing emissions to 20% below 2000 levels by 2020 (a 40% cut in per capita terms) “means an enormous change in our energy supply mix in Victoria,” he said.
“When 66-odd% of the electricity is still going to come from brown coal I do wonder if just the other 34% coming from gas and renewables can actually get you to the target that is being asked,” he said.
“And I can’t answer that question because I can’t see all of the contributions from all of the policies.”
State action will ‘complicate’ national efforts
Instead of individual states introducing their own policies, “national answers are the way to go, with a properly constructed national emissions trading scheme”, Page said.
“It really is not a substitute for a national carbon management plan … to have individual states starting to try to fill the void,” he said.
“Because it would be our view that in the life of the next [Federal] Parliament there will be a much clearer plan, and a plan implemented, and that getting out there too fast as a state actually complicates matters very dramatically for both investors and for policymakers alike.”
Page said individual state measures would be of limited effectiveness, given the interconnected electricity market operating in eastern and southern states.
The actions of one state alone “don’t actually change the investment climate and for that matter, because we are in a competitive, interconnected market, don’t necessarily deliver the outcomes that that state government might think it is going to get”.
Recognition for power station owners
However, there is at least one aspect of the white paper that Page views very positively – the plan to obtain four million tonnes of lowest-cost abatement from the State’s brown coal-fired sector.
“We actually would applaud the initiative on the basis that, for probably the first time since the CPRS debate commenced, we have a sovereign government in Australia that openly recognises that you cannot arbitrarily close plants early either through taxation measures, or some other intervention, without properly recompensing the owners for the lost value,” he said.
The white paper suggests a tendering process to secure the abatement, but Premier John Brumby specified it would involve a “staged closure of Hazelwood [power station]“, involving two of its generating units closing by 2014, when launching the paper on Monday.
Brumby said that, instead of the strategy increasing household energy bills, energy efficiency improvements are likely to result in cuts to energy bills for “many households”.
The feed-in tariff to support large-scale solar power plants is likely to cost the average household between $5 and $15 a year, he added.
By Jessica Mawer ABC Online (27 July 2010):
Scientists say they may have found a cheaper way to produce ethanol.
Dr Slade Lee from the Queensland University of Technology has met farmers and industry leaders in far north Queensland to discuss the region’s biofuel prospects.
Dr Lee says cane could hold the key to making ethanol production cheaper.
He says the enzymes needed to make ethanol are currently being manufactured in large, expensive processing plants but there may be a cheaper way.
“We’ve struck on a novel approach to the problem and that is to get the plants, the sugarcane plants themselves, to produce the cellulose, our idea is to actually get the plants themselves to produce those enzymes,” he said.
A Green School Made out of Bamboo in Bali
When one goes to Bali, you normally expect it to be for sun, sea and surf. But for someone as interested in arts and the environment as I am, there are much more fascinating diversions. So with the help of The Green Asia Group and its dedicated Bali organiser Carolyn Kenwrick, Ken Hickson uncovered the Green School, described as “one of the most amazing schools on earth” giving its students a relevant holistic and green education. Not only that, but the School buildings are made entirely of bamboo. Green School founder John Hardy says this:
“School chose bamboo in the spirit of plenty. With rapidly escalating world cement prices, not to mention the sheer amount of fossil fuel that cement consumes, we must look to alternative building materials. Frankly, it is hard to talk to students about sustainability while they are using the last piece of rainforest for their chair and their table.”
Green School is also becoming the home of the Bali Starling Project, helping to save one of the world’s most endangered bird species. More on that from Carolyn in a future issue.
For more on the Green School, read on.
I’ve been in Bali for a few days, by courtesy of The Green Asia Group, en route to Singapore for the National Sustainabilty Conference (29/30 July) at the Amara Hotel. And back in Brisbane in time for the Climate Change @ Work Conference at Southbank 4 August. See you in Singapore or Brisbane.
What’s the Green School in Bali all about:
Delivering a generation of global citizens who are knowledgeable about and inspired to take responsibility for the sustainability of the world
Green School Bali, one of the most amazing schools on earth, is giving its students a relevant holistic and green education.
The students come from all corners of the world, many relocating with their parents just for the experience of attending. Amongst them, fully 20% are local Balinese kids funded by scholarships from generous donors, allowing them to benefit from an international education and facilitating the magic of Balinese culture to fully permeate the education. The curriculum for younger children is influenced by the work of Rudolf Steiner, who pioneered the idea of holistic education. Older students have the opportunity to study for Cambridge IGCSE’s and a planned IB diploma/certificate course will take them to graduation. Green Studies, which focus on sustainability, and a quality Creative Arts program complement the academic curriculum.
The campus is remarkable. Green School is striving to have the lowest carbon footprint of any international school anywhere, through use of bamboo and rammed earth for its buildings, growing its own food in its gardens, and plans to generate its own power from the river. The central building, “Heart of School”, is one of the largest bamboo structures in the world and has an architectural beauty usually witnessed only in cathedrals and opera houses.
Recent studies revealed that the most important component in student education is the quality of teachers. With this in mind Green School has on staff 21 teachers, including a certified Steiner teacher and a PHD. Seven hold Masters Degrees, one an MBA, four have postgraduate teaching qualifications and 17 Bachelor Degrees. All 21 are qualified educators who are also engineers, psychologists, environmentalists, scientists, film, arts and media people, who choose Green School because they are passionate about equipping children with the skills needed to face the challenges of the future.
Green School invites families from Bali and all other corners of the world to consider giving their children the gift of a Green School education. Young people are welcome for just a term or their entire education.
Why Green School: Why Bamboo?
This section from the website, why bamboo, was contributed by John Hardy, one of the schools co-founders.
Why is Green School where it is?
Green School is located in Sibang Kaja, a village that has been largely passed over by Bali’s tourist development. In developing a “green” school, we wanted the ability to work directly from and with the land – tourist-fuelled development would stand in the way of this relationship. Moreover, the relative scarcity of tourists allows for a fresh conversation between our school community and the local villagers, enabling a more conscious interaction. We are also lucky to have great support from the village leader, A.A. Watusila. Finally, the site is more or less equidistant between Ubud, Sanur, Denpasar, Canggu and Seminyak, all major Balinese urban centres.
Why is everything made out of bamboo?
Green School chose bamboo in the spirit of plenty. With rapidly escalating world cement prices, not to mention the sheer amount of fossil fuel that cement consumes, we must look to alternative building materials. Frankly, it is hard to talk to students about sustainability while they are using the last piece of rainforest for their chair and their table. It is the painful truth that they are going to have to stretch to get enough rain forest timber to build their homes.
Bamboo is available and plenty, and when it is treated with borax salt, it is rendered immune to the bugs that like to eat it, so it becomes a permanent material. Every student at Green School will have an opportunity to plant his or her own bamboo and, eventually, four to five years down the line, will have a chance to harvest, treat and build something with that bamboo.
If you need a lot of timber in the future, don’t look for wood, look for bamboo. It fixes a huge amount of carbon in the soil and this is a good solution in the world of ever escalating problems. It is a rapid solution to some of the problems that are facing us. Plant bamboo.
Why not build out of concrete?
Cement/concrete uses about 1/3 of the world’s oil, between digging it out of the ground, heating it, moving it, and destroying it when it’s no longer appropriate. This uses a huge amount of the world’s fossil fuel and creates huge amounts of carbon for the world.
Green School does use some cement, but the cement is primarily underground. A small percentage of the classroom floors is made from cement, but in general we want Green School to be really green – which means less cement. Representing cement as modern or high class or the future is really not very green. Cement has a very limited place and we need to keep it in its place.
Why are the fences made out of sticks?
The fences are an old Balinese system called “tiang hidup” which means living post. The Balinese discovered long, long ago that if they post a stick, the termites will eat it – unless the post is living, in which case it’s immune from termites. Moreover, the leaves that grow on the post are brought to the cows and goats, providing food with much-needed nutrients for these animals. The post also fixes nitrogen in the soil, which helps the garden flourish.
Why are the blackboards made from bamboo?
Our blackboards are made from bamboo slats, sanded down beautifully, coated in black propane and set in a bamboo frame. This stands in contrast to the “standard” classroom blackboard, generally made from large pieces of slate framed in rainforest plywood – not a very “green” material. Moreover, to acquire those kinds of pieces of slate would require transport across huge distances, forcing a large ecological footprint. When we looked at having a “green” school, we needed to have a “green” blackboard, so we committed ourselves to using local materials – including, of course, bamboo, the life source of the School. One little circle on each blackboard is left unpainted, reminding everyone who uses the board that this is a board unlike others: a truly “green” blackboard.
Why are the paths made of stones?
The walking paths at Green School are made from sandstone blocks carved out of the local river valley and gravel developed from encrusted stone. The advantage of such paths is twofold: first, these natural elements have much less impact on the planet than cement or asphalt road. And second, it lets Green School operate on a principle of adaptability: as people decide to walk when they feel most comfortable, we can easily move rocks and put them where people walk. Thus, the garden can easily become a path and the path can easily become a garden.
How long does a bamboo classroom last?
The classrooms are made from bamboo because it is a sustainable material – as long as it is sheltered from the elements, bamboo lasts forever. The classrooms will last as long as the grass roof is maintained.
My classroom does not have any walls, what’s going to happen when it rains?
The classrooms don’t have walls because it is important in a tropical place like Bali to catch every breeze that comes through – the breeze, combined with fans, is our air conditioning system. Our classrooms are designed to be like ships sailing across the earth, equipped with a “rig” and sails to keep the rain out and the wind in. This creates a further connection between students and the earth.
Is it dangerous having coconut trees on the campus?
When building Green School, we wanted to preserve the local terrain as much as possible – including the coconut trees. If you look closely at the coconuts hanging from Green School trees, you will see that they are in netted bags. This means that the tree can experience its natural cycle of producing coconuts – valuable in the world as a source of both coconut oil and nutrients – while the people below are protected from any mishaps from falling coconut or branches. This is a solution that preserves the environment, maintains safety in the classroom, and also helps in the kitchen.
The bathroom is made out of earth, isn’t that dirty?
Mud was chosen for the walls of the bathroom because it is a local and easily workable material. Although it does create a little dust, its impact on the world is very, very small. Tile, concrete and bricks all take a huge amount of energy to produce.