Carbon Conservation & Energy Efficiency


Bruce Rowse & Team

Archive for the ‘Climate positive’ Category

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.

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.

You have SPAM with a huge carbon footprint

Thursday, September 3rd, 2009

You may have come across this news item a couple of months ago but it is worth taking another look. Although, the study was conducted by a major spam-ware corporation, it is clear that junk e-mails have a huge carbon footprint.


Anything powered by electricity emits greenhouse gases. Recently research was conducted in the US to find out the amount of energy needed to transmit, process and filter spam globally. The results were startling. According to the ‘Carbon Footprint of Spam’ report the average greenhouse gas emission of a single spam message is 0.3 grams of CO2. Is this a lot? Well, if you multiply this by the number of spam sent annually it translates into a huge figure.

It is estimated that there are 62 trillion junk e-mails sent each year. In terms of energy this equals to the energy needed to drive a car around the planet 1.6 million times. If looking at the electricity needed to power these spam it equals to 33 billion kWh. This amount of electricity could power 2.4 million homes for a year! Spam-related emissions for all e-mail users around the world in 2008 totalled 17 million tons of CO2 or about the same as the emissions produced by 3.1 million passenger cars. That’s 0.2% of the total global emissions.

The report found that about 85 to 91% of all e-mails globally is spam. Nearly 80% of the spam-related GHG emissions came from the energy used by the PC users viewing, deleting and searching for legitimate e-mails amongst the junk e-mails. But spam filtering itself accounts for about 16% of spam-related energy use. To view and trash a piece of spam takes about 3 seconds.

If every inbox were protected by spam filters, organisations and individuals could reduce today’s spam energy by 75% or by 25 billion kWh per year. This would save the same amount of greenhouse emissions as produced by 2.3 million cars. In late 2008 a major source of online spam was taken off line and global spam volumes dropped by 70%. However, there are always new ones to take its place.

Linfox video on their carbon reduction program

Wednesday, August 12th, 2009

This 8 minute video shows how Linfox is going about reducing its carbon emissions. What stands out for me in this video is the broad commitment across the organisation to cutting greenhouse gas emissions. Use it to help inspire a similar commitment in your organisation.

Canberra to be Better Place’s first city for electric vehicle recharge network

Saturday, July 25th, 2009

Yesterday Better Place announced that Canberra would be the first site in the national rollout of its electric vehicle recharge network.

Construction of the network will begin in 2011, with services available to electric vehicle owners from 2012.

ActewAGL – the electricity distribution business and retailer in the ACT – responsible for sourcing and distributing the renewable energy that Better Place will use to power electric vehicles within the ACT. “A significant influence on our decision to choose Canberra was the enthusiasm and support we have received from Michael Costello and his team at ActewAGL” said Evan Thornley, Chief Executive Officer of Better Place Australia.

The deployment of the network will include:

  • Recyclable lithium-ion batteries that will power the electric vehicles and be provided as part of the service to drivers, reducing the up-front costs of purchasing an electric vehicle;
  • Charge spots in homes, offices, shopping centres and other car parks where drivers can plug in to keep their battery fully charged; and
  • “Battery Swap Stations” where motorists can drive in and have a depleted battery automatically exchanged for a fresh, fully charged one.

The vision of Shai Agassi, Better Place founder, is for electric vehicles to be cheaper and more convenient than fossil fuel powered cars. Australia is one of three countries where the technology is being rolled out globally. Its great to see this vision now being translated into concrete plans.