Carbon Conservation & Energy Efficiency


Bruce Rowse & Team

Archive for September, 2009

What will make zero net energy office buildings affordable by 2020?

Wednesday, September 16th, 2009

A zero net energy office building is one which consumes no net energy. Its an office that uses very little energy, then has some form of renewable energy to generate all the power it requires.

With current off the shelf solar technology, presuming little or no shading, its possible to get around 100 kWh  of energy per year per square meter of solar panels at latitudes of around 40 degrees, more in sunny locations at lesser lattitude. For a single storey building, with a roof covered with solar panels, and little shading, keeping office energy consumption to 100 kWh/m2 is easy, and in fact I’ve audited quite a few small offices that are nothing special but only use in the order of 100 to 120 kWh/m2. But a grid connect solar system nowdays costs in the vicinity of  $700 to $1,000 per square meter, which is pretty  expensive, so there are very few zero net energy offices in existence.

Aggressive energy conservation and use of off the shelf technology (like skylights) can mean that office energy consumption is kept down to somewhere between 30 to 50 kWh/m2, meaning only half the roof needs to covered with solar panels, or allowing for some shading. For example our office uses only 30 kWh/m2/year, but is shaded in winter, we could make it energy neutral now just by covering around 2/3rds of the roof in solar panels.

So it is possible now, in 2009, to have a zero net energy office, but its not easily affordable, yet. And if your office is 3 storeys or higher, its becomes very hard to achieve no matter what your budget.

Technological advances however, are happening rapidly and I believe that by 2020 a zero net energy low-rise office may be affordable. And importantly this should be achievable by retrofitting an existing office building, with no need to especially construct a new building. Some of these technological changes are:

  • The emergence of LED lighting. Assuming by 2020 we have LED lighting of around 200 lumens per watt. Allowing for some daylighting, and good use of task lighting, it may be possible to have annual lighting use less than 8 kWh/m2/year.
  • Computer efficiency improvements. Assuming that with thin client architecture and high efficiency monitors by 2020 an office PC uses 15 watts, and that a 200 watt server can then serve 30 clients, computer energy use would be around 3 to 4 kWh/m2/year.
  • There are many likely pathways for HVAC, which will depend on climate. A likely pathway for temperate climates is 100% fresh air HVAC systems, with air to air heat exchangers, but also using legacy internal ducting to allow high flow full economy cycles. Fans will be highly efficient, and heat pumps will have high efficiencies at a range of loading conditions, with the conditioning of air separated from ventilation to lower fan energy use. Couple this with light weight retrofit phase change materials (PCM) to provide thermal mass (eg plasterboard with encapsulated PCM), white roofs (where there are no solar panels), glazing treatments and new insulating membrane technologies to improve the thermal performance of the building. Seal the building well, and combine with good use of sensors and intelligent control all of which limits HVAC energy use to say 15 kWh/m2/year.
  • Miscellaneous loads: high efficiency fridge at say 150 kWh/year; near zero standby loss hot water system; high efficiency multi function devices, totalling say 4 kWh/m2/year.

This will result in total office energy use of around 30 kWh/m2/year.

With aggressive energy conservation occupants should be able to to get down to say 15 to 20 kWh/m2/year.

Assume solar panel efficiency is more than double current efficiency and the installed price per watt of a grid connect system is one third of the current cost. This will provide 260 kWh/m2/year at a cost of say $500 per square meter.

A single story unshaded office where aggressive energy conservation is practiced will then need only 8% of its roof covered with solar panels, at a cost per square meter of building area of only $40.

A three storey half shaded office building would need most of its roof covered.

It should be possible to have a 7 storey building energy neutral if unshaded and the roof is covered with solar panels. Of course if additional solar panels can be added to walls it should be possible to get even taller energy neutral buildings.

By 2020 the net zero energy low-rise office building should be easily affordable, and in fact it may well be standard good financial practice to convert existing office buildings to energy neutral ones. So even building owners with no interest in acting to slow climate change will have energy neutral buildings. And most low rise office buildings then – whether they are 100, 50, or 1 year old –  could be energy neutral.

I say “should” and “may” because I still have some doubt as to whether a couple of the technologies that modify the thermal performance of a building –  particularly PCMs, and retrofit membrane’s that improve its insulation properties – will be affordable. But then again with focus a lot can change in 11 years, and as more of us demand better energy performance from our buildings I believe that this will spark the innovation needed to make zero net energy office buildings common place.

You can help make this a reality by acting now to make your building more efficient. Do what is affordable now. Then repeat regularly - technology is now advancing quickly. You’ll create the demand that will drive the innovation that will create the technology that will make energy neutral buildings common place.

Arctic Summer Sea Ice

Saturday, September 12th, 2009

Since I read the draft of Climate Code Red by David Spratt and Philip Sutton just under two years go I’m now setting up an annual routine of looking up the Arctic summer ice thickness in mid September, when the ice extent is at a minimum.

Climate Code Red alerted me and many other Australians to the rapid loss of Arctic Ice, with the Arctic compared to the “canary in the coal mine” when it comes to global warming. I wrote an article which I posted on Squidoo about this towards the end of 2007, which summarised my understanding of Climate Code Red.  Now in September 2009 the need to rapidly cut greenhouse gas emissions is no less urgent. And if anything – as indicated locally by the bushfires in Victoria in February and the record breaking weather of August – climate change is happening quicker than we thought.

Now for an update on the Arctic. Science Daily recently reported on research which has correlated satellite data with submarine records. This shows that in the winter of 1980 Arctic ice averaged 3.64 meters in thickness. By the end of  2007 the average was 1.89 meters.  Over 27 years the depth of Arctic ice halved.

Over the same time the extent of the summer sea ice has greatly reduced.  The summer of 2007 had the lowest extent of summer sea ice. In September 2009, as reported by the Examiner, the ice extent is somewhat more than in September 2007, but still well below the 1979 to 2000 average.

The canary in the coal mine is still alive, but its future isn’t looking good. We need to keep on cutting carbon emissions.

Painting your roof white better than a PV system in slowing global warming

Thursday, September 10th, 2009

Lawrence Berkerley National lab reported November last year on some fantastic research into how “cool roofs” can help slow global warming. White surfaces reflect rather than absorb radiation, and can be effective in re-radiating heat back into space. I’ve only just come across this research today, and the potential greenhouse gas savings are enormous.

Painting a roof white

Painting a roof white

Most roofs are dark in colour, the research by Akbari, Menon and Rosenfield calculated the CO2 offset achieved by increasing the solar reflectance of urban surfaces. For a 100 m2 roof making a dark roof white (with a long term solar reflectance of 0.60 or more) will offset around 10 tonnes of CO2 per year.

A 10 tonne saving per 100 m2 is a large saving. In hot climates white roofs also reduce air conditioning loads. So called “cool coloured” surfaces apparently have only half the benefit.

In California its been law since 2005 that flat roofs be painted white. We should have the same laws in Australia, and should also be legislating that sloped roofs should be white, or at least “cool coloured” as has been the case in California since July.

Assuming it costs $1,700 to clean and paint a 100m2 tiled roof white, and thus save 10 tonnes of carbon, this one measure will provide more climate benefit implementing all of the following:

  • Replacing you gas hot water system with a solar hot water heater (gas boosted)
  • Installing a 2 kW solar PV system on your roof
  • And implementing energy conservation measures that save 16 kWh per day

* Assuming an emissions factor of 1 kg CO2/kWh.

If you don’t have an air conditioner “geo engineering” by painting your roof white won’t save you any money. But in terms of tonnes of greenhouse gas saved per dollar invested painting your roof white – whether at home or at work – could be one of the least expensive ways of cutting greenhouse gas emissions. And it may help you avoid the need to get an air conditioner.

If you have a low carbon footprint to start with, based on this research, painting your roof white could actually neutralise your other emissions. And someone with a white roof is doing more to slow global warming than someone with a 5 kW PV system on their dark roof.

Solar Air Conditioning – Cool Technology!

Monday, September 7th, 2009

A recent Sustainability Assessment job took me to the corner of Victoria to the town of Mildura.  A town of around 30,000 people, Mildura borders NSW on the Murray River.  In summer the maximum temperature averages over 30 degrees and naturally there is a high demand for air conditioning and water.  Conventional air conditioning systems contribute substantially to greenhouse gas emissions through the consumption of electricity (predominantly generated from burning coal) and water, for cooling towers and evaporative cooling systems.

The idea of solar air conditioning was mentioned, which sounds great, but does it exist and is it practical?

After doing some reading, yes, solar air conditioning does exist, but despite Australia’s sunny climate there does not seem to be much awareness, knowledge and skills in this area.  So how does it work and why isn’t it widespread in Australia?

From my understanding, there are essentially two categories of solar air conditioning.

  1. Ventilation based systems that use photovoltaic power to power fans via heat exchangers or  through desiccant filters  that remove moisture from the air and improve thermal comfort and;
  2. Solar thermal systems that harness the sun’s thermal energy (heat) to drive the cooling system.

Photovoltaic powered ventilation based systems are very much dependent on climatic conditions and building design.  These kinds of systems take advantage of fresh air intake to a building and remove unwanted levels of humidity, improving thermal comfort and reducing cooling (heating) requirements.  These kinds of systems have generally been adopted for smaller-scale applications, including the residential market.  This form of solar cooling does not actively cool the air supplied to a building space and is therefore limited to the right environmental conditions to work effectively.

Solar active thermal systems are expensive, more complex and generally too big for smaller applications such as residential housing.  The common system uses an absorption chiller, which compared to a conventional compressor based chiller, does not use electricity to power the system, but instead uses solar collectors to heat water that is then used to produce chilled water through interaction with a refrigerant or desiccant solution.  Such systems can also be used to generate hot water for heating requirements and general hot water needs.  Such systems make good sense where ample sunlight is available and for large-scale or remote applications.

Absorption Chiller

Solar Absorption Chiller


Australia has a high demand for air conditioning and therefore a high demand for electrical energy through use of conventional compressor driven coolers.  The high demand of air conditioning in summer puts a huge strain on the electricity network and contributes substantially to global warming through burning fossil fuels and use of refrigerants (which have an extremely high global warming potential) in air conditioning systems.

Why then is solar air conditioning not widespread, at least for large-scale applications?  The main barriers to solar cooling include:

  • The high cost of solar collectors
  • Lack of skills in solar cooling technology and increased complexity
  • Abundant, cheap energy with no environmental cost
  • Minimum incentive to reduce peak power consumption

Overcoming these barriers really requires government intervention through subsidies, research funding, introduction of interval metering to pass on peak costs to electricity users and introducing a carbon tax or trading scheme to factor in an environmental cost on energy.

The Australian National University (ANU) is currently developing a hybrid solar air conditioning that is aimed at replacing conventional residential air conditioners.  The design employs a solar thermal powered compressor that can provide cooling and heating just like a reverse cycle air conditioner. The break-through is the ability to generate cooling like an absorption chiller, but without the need for a bulky and complex system.

The system employs what is called an ‘ejector pump’, which is capable of generating low pressure (necessary for refrigeration) and is low cost to manufacture.  A refrigerant is pumped to high pressure and then heated by solar collectors (the same used for solar hot water systems).  The ejector creates a drop in pressure (the cooling effect) by converting the energy in the refrigerant into kinetic (movement) energy by firing fluid into the ejector at supersonic speed.

Ejector Pump

Ejector Pump


Amazingly, the only electricity needed to power the ejector unit is 150 watts or 1/10 the power minimum of a conventional air conditioner.  This is set to revolutionise air conditioning as we know it and the project is moving closer to commercial viability.  With the onset of a carbon trading scheme, the rollout of smart meters beginning, energy rates set to increase and summers increasing in temperature, the economic case for this upcoming technology holds great promise.   I certainly can’t wait for this ‘cool’ technology!

Indoor plants make buildings safer

Monday, September 7th, 2009

According to the U.S. Environmental Protection Agency, volatile organic compounds (VOCs) are found in concentrations consistently higher indoors (up to ten times higher) than outdoors. These cause significant health risks. Now scientific research has confirmed that the solution is in many common, easy-care indoor plants.

VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. VOCs are emitted by a wide array of products numbering in the thousands. Examples include: paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, office equipment such as copiers and printers, correction fluids and carbonless copy paper, graphics and craft materials including glues and adhesives, permanent markers, and photographic solutions.

Symptoms from VOCs include eye, nose, and throat irritation; headaches, loss of coordination, nausea; damage to liver, kidney, and central nervous system. Some organics can cause cancer in animals; some are suspected or known to cause cancer in humans.  Key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, shortness of breath, declines in serum cholinesterase levels, nausea, vomiting, nosebleed, fatigue and dizziness.

So you could say that these plants are self-regulating air purifiers which also produce oxygen and remove carbon from the air.

As well as adding to our safety, plants add greatly to our comfort. We feel good when we’re around healthy plants because they’re a key part of our natural environment,. To top it off, plants are beautiful, modular and incredibly good value.

So select from those listed below, and google how to care for them, it’s simple. Just be aware that many indoor plants are chosen because they are understorey plants. This means in a forest they shelter under other taller plants, and so often do not cope well with any direct sunlight on them.

These Indoor Plants have been proven to Reduce Air Pollution

Common name Latin name

Parlour Palm Chamaedorea elegans

Dracaena Dracaena marginata and D. “Janet Craig’

Kentia palm Howea forsteriana),

Peace Lilly Spathiphyllum ‘Petite’, Spathiphyllum. ‘Sensation’),

Philodendron ‘Congo’ Philodendron ‘Congo’


Umbrella Tree Schefflera ‘Amate’

Snake Plant /Mother-in-law’s Tongue    Sansevieria trifasciata

Zanzibar Zamioculcas zamiifilia

Sources: Recent Research carried out by the National Interior Plantscape Association and Professor Margaret Burchett at the University of Technology Sydney.