Home Heating

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<img src="https://counter.theconversation.edu.au/content/57114/count.gif" alt="The Conversation" width="1" height="1">
GUEST OBSERVER
Another hot and humid day in Sydney tomorrow with a maximum of 32 degrees in the city and 38 in the western suburbs.
How many times have we heard that on TV or radio weather reports?
But what would you think about the following forecast?
Temperatures in Wattle Street, Ultimo, will spike at 37 degrees around 10 am. Further up the hill at Point Street we can expect a top of 40 degrees shortly after 1 pm. Meanwhile, at the Observatory Hill weather station the 3 pm maximum will struggle to pass 32 degrees.
We are unlikely ever to be able to forecast temperatures to such pinpoint accuracy. Still, the above exercise reflects the very real differences in temperature – and thermal comfort – at the scale of the individual street, indeed individual block, within our cities.
The driver of this surprising variability is the interaction between urban form and the heat energy of the sun. Building heights and materials, width and orientation of streets, and presence or absence of vegetation all affect local temperatures across the city. And if we drive to work, the heat from our vehicle’s engine and exhaust might be adding a degree or two.
Recent media reports have highlighted the bizarre weather patterns in Sydney over January, February and March 2016. Some reports have linked evidence of temperature extremes to urbanisation and the loss of shading and moisture that vegetation provides. This is known as the Urban Heat Island (UHI) effect.
A research collaboration between the UNSW Faculty of Built Environment and the Universities of South Australia and Melbourne has collected further evidence for the highly localised effects of building form, surface materials and street orientation on outdoor microclimate and pedestrian thermal comfort. The aim is to build a solid evidence base to inform design, planning and policy across Australian cities.
Meteorological data collected during the 2015-16 summer in Sydney reveals that air temperatures in the street “canyon” may vary by up to 5℃ from those the Bureau of Meteorology records at Observatory Hill.
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Even more worrying are the surface temperatures measured on building facades. These may exceed 70℃ in the sun.
The vertical surfaces of multi-storey buildings account for much of the urban surface in contact with the surrounding air. Hotter surface temperatures elevate nearby air temperatures during the day.
Then, due to the thermal mass of typically dense and dark building materials, building facades continue to emit radiant heat well after sunset. This slows the cooling of local outdoor air temperature.
Without night-time cooling, human thermal discomfort is prolonged. Consecutive nights of elevated air temperatures have severe impacts on human health. This includes increasing heat-related mortality and morbidity.
More extreme heat days projected from climate change on top of localised heating due to urban design elevates the health risks from future heatwaves.
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<h2>Urban temperatures vary with design</h2>
Our research sought to quantify the effects of typical urban form and materials on street microclimate and outdoor thermal comfort. We recorded building surface temperatures and ambient air temperatures using a thermal camera and mobile weather station in various locations in metropolitan Sydney.
Preliminary results suggest that business-as-usual architectural and urban design are exacerbating urban heat and creating hotter cities. This is alarming when considering the current and projected population of Australia’s major cities, particularly the growing proportion of vulnerable elderly.
On January 14, 2016 – Sydney’s hottest day that month – the 9AM and 3PM air temperatures recorded at Observatory Hill were 30.8℃ and 32.4℃ respectively.
On the same day, pedestrian-height air temperatures were recorded mid-morning in Wattle Street, Ultimo – 32.34℃ at 9am – and mid-afternoon in Point Street, Pyrmont – 36.34℃ around 3pm. These temperatures in Wattle and Point streets were 1.54℃ and 3.94℃ higher – or up to 12.2 percent greater – than the maximums at Observatory Hill.
Prior studies have reported a significant increase in mortality for every 1℃ rise in air temperatures above a mortality-temperature threshold (typically around 32℃ for Australian cities). This applies particularly for the population aged 65 years and older. Conversely, every degree of cooling has health and economic benefits for urban residents.
The surface temperatures of nearby building facades confirm a potential source of localised heating. The seven-storey, northeast-facing Wattle Street facade recorded a maximum spot temperature of 65℃ and a mean surface temperature of 46℃ around 9AM. The eight-storey, northwest-facing Point Street facade recorded an average surface temperature of 42.4℃ and a spot maximum of 54℃ mid-afternoon.
Notwithstanding measurement uncertainty due to emissivity (how well a material emits heat energy), the higher daytime building facade temperatures suggest an influential relationship with observed near-facade air temperatures.
By taking into account the design drivers – including orientation and solar exposure, material albedo (reflectance) and emissivity, and views of opposite buildings and the sky – building designers can help cool our cities through “cool facades”.
<h2>Buildings hold key to outdoor comfort</h2>
We also calculated the effects of material properties on outdoor air temperatures and thermal comfort for January 14.
Footpath albedos (reflectance) in Wattle Street and Point Street ranged from 0.033 to 0.050 for rough weathered bitumen and smoother grey stone pavers respectively. Superficially the footpath materials appear to be the same colour. However, the rougher bitumen has a lower reflectance and therefore absorbs more solar radiation (and becomes hotter) than the smoother stone tile.
Prior studies have linked surface roughness to reflectance characteristics. The potentially contradictory effects of footpath surface reflectance on air temperatures and thermal comfort are evident in the grey globe thermometer (GGT) measurements.
The GGT measures only radiant heating to which humans are particularly sensitive. Cooler air temperatures are often correlated with higher albedo surfaces, but greater reflectance may increase the radiant load on pedestrians, increasing thermal discomfort.
The GGT 10-minute mean between 8.30AM and 10.30AM in Wattle Street was 36.95℃ and the ten-minute mean air temperature for the same period was 33.70℃. Between 1PM and 2.30PM in Point Street, the GGT ten-minute mean was 43.0℃ and the ten-minute mean air temperature was 38.57℃.
The relative differences between ambient and GGT temperatures are 4.87℃ and 6.05℃. This greater GGT temperature difference confirms the additional radiant heating from the more reflective footpath surface and nearby hot facade.
The conclusion? Weather is not simply what the bureau tells us. As higher urban temperatures occur at the scale in which people actually live – the building, the street, the block – the implications for our health and well-being are profound.
By informing those involved in city planning, management and design about the implications of their design decisions on urban microclimate, this research provides the evidence base for a “cool” urban future.
Paul Osmond is senior lecturer, Sustainable Built Environment, UNSW Australia and can be contacted <a href="https://theconversation.com/profiles/paul-osmond-205774" target="_blank">here</a>.
Jonathan Fox PhD Research Candidate, Urban Climates Research, UNSW Australia and can be contacted <a href="https://theconversation.com/profiles/jonathan-fox-250999" target="_blank">here</a>.
Both are authors for The Conversation.
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jchancellor-FAypfDUnLy

Building cool cities for a hot future

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GUEST OBSERVER
A few years ago, similar to views about future electricity demand, forecasters thought gas demand in Australia would keep rising. As it turns out, gas demand peaked in 2012 and may halve by 2025 - as we showed in our recently published University of Melbourne Energy Institute (MEI) report.
Step by step, householders are making economic decisions that will eventually lead to many completely disconnecting from the gas grid, as they find gas to be an increasingly costly secondary source of home energy.
This is particularly true when it comes to space-heating. When the cost of operating a modern reverse cycle air conditioner (known in Tasmania and elsewhere around the world as a heat pump) can be one-third the cost of heating with gas, why wouldn’t a householder have a look at the possibilities?
Another attraction is that heating with a reverse cycle air conditioner is largely renewable. Our research has quantified that reverse cycle air conditioners in Australia recover more renewable energy than do all of the millions of rooftop solar photovoltaic (PV) installations. Who knew?
Gas demand declining
The following chart illustrates how gas demand will decline in eastern Australia in all sectors: in the electricity generation sector, in industry and also in buildings as householders and building managers switch to efficient electric heating devices.
<a href="/images/2015/09/07/image-20150904-28914-1x3dun3.jpg" target="_blank">Click to enlarge</a>
<img src="/images/2015/09/07/image-20150904-28914-1x3dun3.jpg" alt="">
Previously we qualitatively described how in this “second electrification” of the Australian home, people will economically fuel-switch to induction cooktops, hot water heat pumps and reverse cycle air conditioners, resulting in their homes becoming gas-free.
As shown in the following chart, the money that householders can save when economically fuel-switching from gas to electricity can amount to hundreds and even over a thousand dollars per year.
Some of this change will occur very rapidly. In up to one million homes in eastern Australia, householders have already installed reverse cycle air conditioners for summer cooling but have never attempted to use them for heating. Why not? Time and time again I have been told by friends, acquaintances and those writing on social media, “Oh, I have always thought that gas must be cheaper.”
As shown in the following chart, analysis done by the Alternative Technology Association (ATA) indicates that using reverse cycle air conditioners to heat a large Melbourne home can amount to A$658 per year. But how is this possible?
<a href="/images/2015/09/07/Screen%20Shot%202015-09-07%20at%209.18.23%20AM.png" target="_blank">Click to enlarge</a>
<img src="/images/2015/09/07/Screen%20Shot%202015-09-07%20at%209.18.23%20AM.png" alt="" width="782" height="491">
<h2>Heat pumps: global renewable energy giants</h2>
The biggest reason behind these new home economics is that reverse cycle air conditioners produce far more energy than they consume. Operating at efficiencies of up to 600%, they use a small amount of purchased electricity to capture free renewable heat from the outside air. For ducted gas heating, which can operate at efficiencies of less than 50%, the opposite is true.
The following diagram shows that a ducted gas system will consume 34.02 megajoules of energy (including gas and electricity for the air blower: the sum of the two blue figures on the left) in order to produce just 10 megajoules of useful delivered heat. The rest of the gas energy purchased is immediately, in a sense, thrown away.
<a href="/images/2015/09/07/image-20150904-28894-9yjaso.jpg" target="_blank">Click to enlarge</a>
<img src="/images/2015/09/07/image-20150904-28894-9yjaso.jpg" alt="">
This compares to an efficient reverse cycle air conditioner that requires only 2.55 megajoules of purchased electricity (the sum of the blue figures on the right) to extract an additional 9.53 megajoules of free, renewable, ambient heat from the air outside your house, and then produce the same 10 megajoules of useful delivered heat.
In other words, in this comparison, in order to get the same amount of heat from a reverse cycle air conditioner, the householder must purchase only 1/13th of the energy needed to operate ducted gas. This efficiency advantage wipes out the traditionally lower cost of gas energy versus electrical energy when those commodities are compared on a dollar-per-megajoule or per-kilowatt-hour basis.
In 2014, reverse cycle air conditioners were such significant harvesters of renewable energy in Australia that our research found they recovered twice as much renewable energy as did rooftop solar photovoltaic (PV). The following chart compares these 2014 figures and also shows the future potential of reverse cycle air conditioners as more people learn of their capabilities.
In the United Kingdom, the renewable-energy-harvesting power of reverse cycle air conditioners is recognised and they are even eligible for renewable energy certificates in that jurisdiction.
In Australia, where governments have not been interested in rewarding people for buying air conditioners, no similar scheme exists. However, in an application of the same technology, hot water heat pumps do receive renewable energy credits here.
<h2>Gas stays in the ground – for longer</h2>
One consequence of falling gas demand in eastern Australia is that it will take longer to deplete already-developed conventional gas resources. As shown in the following figure, the Australian Energy Market Operator’s recent gas demand forecast results in the depletion of 10,000 petajoules of gas by 2032. In the Melbourne Energy Institute scenario (also plotted below), which projects that less gas is used in buildings, the same volume of gas lasts for more than an extra decade.
<a href="/images/2015/09/07/image-20150904-28914-alh1ow.jpg" target="_blank">Click to enlarge</a>
<img src="/images/2015/09/07/image-20150904-28914-alh1ow.jpg" alt="">
Using less gas in buildings, thanks to economic fuel-switching, energy efficiency measures (such as insulation, draught-proofing and improved window treatments) and other factors, means that a significant volume of gas can be freed up for higher-value industrial uses, as illustrated in the following chart.
<a href="/images/2015/09/07/image-20150904-28878-nvgpub.jpg" target="_blank">Click to enlarge</a>
<img src="/images/2015/09/07/image-20150904-28878-nvgpub.jpg" alt="">
 
Plenty of people in Australia are talking about disconnecting from the electricity grid. However, the costs and technicalities of battery storage and the possibility of needing to resort to a back-up petrol generator will convince many to stay connected to that often-reliable electricity grid.
On the other hand, we’ve shown the gas network is different. Households are making, and will continue to make, economics-based decisions to reduce gas use.
When planning the future of our energy grids, we think it is time that energy planners move away from decades of focusing strictly on supply-side options, and now consider gas and electricity demand-management options as well.
 
Tim Forcey is energy advisor, Melbourne Energy Institute at University of Melbourne and author for The Conversation. He can be contacted <a href="https://theconversation.com/profiles/tim-forcey-104740" target="_blank">here</a>.
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The cheapest way to heat your home with renewable energy – just flick a switch

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Telstra is pouring money into making homes smarter and in turn, growing its business.
That means the telecom company is trying to transform into a tech company through smart devices that talk to each other and control the heating, cooling, and lighting etc in your homes, according to a recent report in The Australian Financial Review.
Telstra is not alone. Tech giants Apple, Amazon, Samsung and Google have all been vying to control the emerging $US121 billion market.
As an example of how Telstra envisions its future, Telstra executive John Chambers uses his Smart Home app to check the liquor cabinet usage of his children.
“I now have a much deeper understanding of my home,” Chalmers told the AFR.
Eighty percent of Australians worry about leaving a light or appliance on when they go away, surveys show. It is this opportunity that Telstra is trying to cash in, with a $25-a-month Smart Home plan when its customers bundle up their mobile and broadband services.
 It could also become a boon for the elderly and disabled.
“You’ll be able to see when your mum is opening the fridge and how is she moving around the house, a whole variety of very simple non-invasive techniques just to keep an eye on your ageing parents,” Chambers says.
“We’re working on solutions to adapt it to the 500,000 homes of Australians with a disability.” 
He said existing smart devices are not cost-effective. Telstra is working on a single, intuitive platform which can integrate with Apple, Google or Samsung devices on one app.
Telstra’s new ventures are a response to the threat to its traditional business. The company has been pivoting hard and investing heavily in new businesses. 
Telstra Ventures – the company’s venture capital fund – has spent more than $240 million on 18 digital health businesses, with the aim of reaping $1 billion in annual revenues by 2020. It is still not profitable yet.
Whelan said Telstra Ventures aims to invest in  companies that are already generating revenue. 
“We have a process internally called the conveyor belt,” Whelan says. “We formulate ideas, we incubate them, we scale them and then transition them. We have businesses at all those stages of the life cycle.”
Chambers expects the number of devices in a people’s home will go up significantly in a few years.
“The potential to service a few million homes is very real,” he concludes.
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