5 Ways to add value to your services using Life Cycle Design

Life Cycle Design (LCD) has quickly become the go-to method for defining sustainability in buildings in governments, green building councils and organisations around the world. It is considered best practice for good building design by the International Standard Organization (ISO 14044) and is a powerful methodology for ensuring genuinely sustainable and high performance outcomes.

This article and video recording provide an overview of Life Cycle Design and explain five ways to add value to your services using LCD. Be inspired by how LCD has been incorporated in different sectors and projects, and how key stakeholders have taken it on board.

Some of the topics covered include:

What is Life Cycle Design and the methodology
The importance of green buildings and measuring building environmental performance
Green Star projects – general overview
LCA as a required part of ESD tender documentation
ISCA and use of LCD as an integrated desgin approach
LCD for regulatory approvals
Marketing and sales campaign
eToolLCD software 

 

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carpark

Car Park Lighting Sensors

So if you’re designing an apartment building and you’re stuck with an underground car park things can get pretty nasty with energy consumption.  With no natural light and a clear safety requirement to keep the area lit all things point to an energy hungry lighting solution.   Even the most efficient lamps will still burn a lot of power running 24 hours a day, 365 days a year.

The most obvious solution to drop run time is lighting controls.  Specifically motion sensors.  But how should these be set up, and how does the set up (number of lamps per sensor and lamp shutoff delay) actually effect the energy savings the controls will achieve?  The short answer is, make sure they turn off really quickly after the car or person is out of the area.  The long answer is below:

It’s Complex…

The interplay between the car park layout, vehicle traffic, pedestrian traffic, simultaneous use of certain areas of the car park, probability of a specific car bay being accessed, the shut-off delay timing and the distribution of sensors means calculating light run time is very complex.  Pondering the possibilities got the better of me and I ended up running a simulation to determine effect of some key parameters.

A Conceptual Car Park

The conceptual car park looked like the below pick.  Effectively 150 bays with one pedestrian access and a main vehicle exit point at one end.

Car Park Map

I used some basic lighting design to work out how many lights would be needed (single globe T5s) to achieve an adequate light levels (50lx).  The calcs indicated a requirement of about 80 lamps.  I just placed these in the road ways and walk ways in my conceptual design.  These are the numbers with the x in front of them.  In reality they’d be probably be spaced more evenly but this satisfies the requirements of the model which is just to see how many lights would be triggered when each bay was accessed.

Which Car Bay Triggers which Lamp?

That was a manual process of thinking about how a person will walk from the lift to the car, and then how they will drive out (or vice versa).  The below diagram shows that if car bay 125 is accessed the blue line will be traversed by the car driver and passengers, whilst the red line will be travelled by the car.  All the lamps highlighted in red will subsequently need to fire.

Car Park Map - Lights Triggered By Bay 125

Simulation

I got some stats on how many trips and average household does from here and here.  The Sydney data also gave these neat graphs on when the trips occur as well.  This enabled me to put a probability on a given car being accessed at a certain time of the day.  The sensors are obviously going to give the most benefit during lower trip frequency times.  But depending on the set up, you can even get a reduced run time during the peak times in this car park (not every day, but some days there’ll be savings due to the random nature of when people take a car trip).

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After some sense checking I ran the simulation for different combinations of motion sensor parameters.  The focus was on:

  • The delay before the lamp is shut down after the motion sensor is activated (or re-activated)
  • The number of lamps per sensor (if you whole car park is wired to one sensor, you’re not going to get as much benefit)

The below chart shows the results.  It looks pretty clear that the most important attribute is the delay before the lights are shut down again.  Amazingly, with 10 lamps per sensor a 90% run time reduction could be achieved if the lamps only fired for a minute.  10 lamps per sensor is probably as sparsely as you’d want to space the sensors to make sure they fired when there was movement

Simulated Car Park Lighting Energy with Sensors

Pit Falls

The simulation is obviously not a real live thing so I want to note some possible pit falls.

  • I got lazy and didn’t model weekend days separately.  So the actual savings are probably greater than what I’ve reported above.
  • If you car park is full or big rodents that trigger motion sensors 24 hours a day, the savings won’t be achieved.
  • My “Shut off delay time (mins)” is actually the lamp run time from when the motion sensor is first fired during a particular event, not from when it was last fired during that event.  So for you to achieve the 1 minute shut-off delay, you’ll probably want the light to go down 5 or 10 seconds after there was no motion in an area.  Perhaps this would cancel out the additional savings you’d get from lower weekend trips.

Other Car Park Lighting Ideas

Although motion sensors in car parks are an absolute no-brainer, there are also other things that can be done to make car park lighting smarter, a few of which I’ll include below.

Lux sensors may also be utilised with dimmable lamps to ensure light levels over the requirements are not delivered and hence energy savings may be achieved due to lower average lamp power.  The benefit of lux sensors in underground car parks is limited however due to a lack of natural light.

A better coefficient of utilisation can be achieved with light coloured rooms (more reflectance, so better light utilisation from your lamps which means you’ll need less lamps).

The lamp itself should be considered carefully and in conjunction with the lighting controls.  The most efficient globe in the world may be the wrong choice if you need more of them than necessary.  Similarly, if it won’t handle being turned on and off all the time, that’s going to be a problem.

The light housing can also help if it’s got a nice reflective backing to disperse the light where it’s needed (down and sideways) instead of where it’s not (up).

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Grid-tied VS Off-grid Solar PV systems

Introduction

With the tremendous uptake of residential solar PV installations all around the world, the next question that often comes to mind is: to stay grid connected or go off-grid? For most people who are concerned about environmental issues, they might be led to believe that completely weaning off our fossil fuel powered grid is the truest form of sustainable living. However, here at eTool we like to challenge people’s beliefs based on data from life-cycle analysis.

To start, let’s quickly look at the difference between the two systems.

Grid-tied

Grid-tied PV system

 

A grid-tied system is connected to the utility grid. In new systems, there is only one meter that measures both in-coming and out-going power to the house. Power generated from the solar panels goes through the inverter which converts DC to AC which then used throughout the house. Any left-over power that is not used goes out to the meter where it is measured then fed into the grid to be consumed elsewhere. This system has no on-site battery storage so any solar power that is not used at the time it is generated will be fed directly out to the grid. When no energy is generated by the solar panels such as at night or on overcast days, power will be drawn back from the grid to supply the house.

Off-grid

Off-grid PV system

 

An off-grid system means that the system has no connection to the grid at all. In this situation, battery storage is necessary in order to provide power to the house when there is no power generated by the PV system. An additional on-site generator may also be required as a backup in case the stored power runs out. In this system, the power from the solar panels goes through a charge controller or battery regulator then into the battery bank for storage. On demand, the power is drawn from the batteries through an inverter then to the house to be used. If the power stored in the batteries run out, a generator can be started to produce backup energy.

 

LCA Comparison

Carbon Intensive Grids

 

SYSTEM TYPE SPECIFICATIONS
AU Standard Structure – timber + double brick
Cooking – Electric
HWS – Gas storage
HVAC – Airsource heat pump (MEPS ave)
Lighting – CFL
Refrigeration – AU average
Water – AU average

In order to compare the systems, we will use LCA to quantify the impacts in CO2e. We assume that all other factors are constant such as water, gas and the carbon intensity of the grid. The table above shows the building structure and appliance specifications for a standard Australian detached home. Only the PV systems will change in order to better compare the difference between grid-tied and off-grid.

Graph1

The graphs above shows the life-cycle carbon impact of a standard Australian home with no PV system installed. We can see that the life-cycle energy of the building takes up the largest portion of the overall impacts of the building. The graph on the right shows the end-use breakdown of the standard Australian household’s energy use.

Graph2

The blue column on the left in Graph 2 above is a standard Australian home with no PV. The red column is an off-grid system sized to provide 100% solar power throughout the year. This is a 15kW PV with about 100kWh of battery storage to provide backup power for 3 days while the green column is the grid-tied version with 15kW of PV without battery storage. The orange& dotted columns show the impact of a smaller off-grid 8.5kW PV system with 60kWh of battery storage. The dotted orange column has an additional backup diesel generator that provides 10% of the energy demand. The teal column on the right is the grid-tied equivalent with 8.5kW PV and no diesel backup or battery storage.

We can see that installing a PV system alone has a significant effect at reducing the CO2e impact of the building. Note that despite a near two-fold increase in the amount of PV, the life-cycle carbon savings in the off-grid system only has marginal improvement when compared to the grid-tied system. This is due to the high embodied impacts of the larger PV system which are underutilized in the off-grid system whereas in the grid-tied system all extra power generated by the over-sized system is fed into the grid.

Graph3

In the graph above, we compare the category breakdown of the 15kW PV systems versus the AU standard home, we can see that while the life-cycle energy use of the solar powered homes have dropped significantly, the recurring impacts on the other hand have increased due to the impacts related to replacing PV panels and batteries.

Low Carbon Intensity Grids

In areas with cleaner grids, in this example I’ve used the Tasmanian grid (even though it is still connected to the NEM) – is a grid-tied PV system still relevant?

Graph4

 

The graph above shows that although the proportion of savings is much less in a low-carbon grid, a grid-tied PV system still has a lower life-cycle CO2e impact compared to an off-grid system. In areas with cleaner grids, the embodied energy impact of the building becomes proportionately more important than the operational energy as shown in the graph below.

Graph5

 

Best Practice Design

How about a house that is designed by someone who knows what sustainability is about? Let say they designed using low-embodied energy materials and didn’t install any air-conditioners – how would such a house compare? The low-impact or ‘best practice’ design building assumes that the occupants are more sustainably conscious and try to reduce electricity demand as much as possible in the choice of appliances they will use and are more likely to build with low embodied impact materials such mud brick. A detailed list of specifications in the ‘best practice’ house are listed below while still assuming Australian averages for water and refrigeration energy use. Based on these specifications, the off-grid ‘best practice’ home will need 4kW of PV and 48kWh of battery storage assuming 10% of the energy demand to be provided by a diesel generator.

 

SYSTEM TYPE SPECIFICATIONS
Best Practice Structure – mud brick
Cooking – Wood
HWS – biomass
HVAC – ceiling fans+wood pellet heater
Lighting – LED
Refrigeration – AU average
Water – AU average
PV – 4kW
Off-grid Backup –  48kWh battery storage + diesel generator

The graphs below show the global warming impact of a ‘best practice’ home on an Australian average grid the embodied and operation energy breakdown and the carbon impacts on a low-carbon grid. Even though the overall life-cycle carbon impacts of the building has dropped significantly due to the ‘best practice’ design, the results still indicate that being grid-connected is better for the environment in both grid situations.
Graph6 Graph5 Graph4

 

 

Conclusion

In areas with carbon intensive grids such as Australia, it is important to help ‘clean up’ the grid by staying grid-connected with our PV systems. This is due to the fact that all the excess potential energy from off-grid PV panels is ‘wasted’ instead of captured to be used elsewhere. An off-grid setup will usually have a PV system that is large enough to meet most of the energy demand of the household throughout the year. This means that the system will be sized to produce enough power in winter but in summer when there is more daylight, the extra electricity generated by the system will be wasted.

A grid-tied system on the other hand is able to take advantage of an existing energy network and maximise the energy generation potential of their PV systems as any excess energy is fed back into the grid to be utilised elsewhere. This means that the embodied energy of the building can also be offset when the building produces more renewable energy than it consumes throughout its life.

A cleaner grid also means that other homes, offices and industries such as water desalination plants and manufacturers that use this cleaner electricity will be less carbon intensive. We all benefit from the knock-on effects of staying grid-connected.

For areas where the grid is already ‘clean’, the operational energy impacts become less significant from a carbon perspective but you’re still better to have grid-tied PV. Staying connected in a green-grid also helps avoid the additional embodied impacts from an oversized PV & battery storage system.

 

Graph9

Bear in mind that there are other resources and technologies that haven’t been modelled here which may provide better solutions by taking the best of both systems. For example, hybrid systems combine the advantages of grid connection with battery storage to help moderate grid loads. To provide an efficient solution to large scale energy distribution, ‘Smart Grid’ systems that monitor and control the grid’s energy distribution and production is the way to go. Combine smart grids with hybrid solar systems and the economics and efficiency of renewable energy distribution and supply grid will be greatly improved. Nevertheless, the underlying message still points to the fact that staying grid-tied is the key in order to stay most sustainably relevant today and in the future.

Tesla most recently announced their low-cost ‘Powerwall’ battery storage system which will affect the current PV market.

 

 

Sustainable Design Principles 101 – Multi-Residential Australia

This post is designed to guide design teams during early design stages prior to any form of drawing mark-up. It describes a pathway of continuous building improvement through easy low hanging fruit strategies to incorporation of renewable technologies and advanced design principles. As sustainability becomes engrained in the construction industry it is important that stakeholders maintain an understanding of what the market expects both presently and going forwards into a low carbon future.

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Achieving Targets – The Basics

Generally a multi-residential apartment building built to BCA standards (electric hot water, 6 star Nathers and standard air conditioner) will have approximately the same impacts as the benchmark average dwelling (4.2 tonnes/person/year). They tend to be smaller (less space to heat and cool), have longer design lives and high occupancy (reducing the impacts on a per person per year basis). The chart below represents the life cycle Impacts of a typical multi-residential apartment building.

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Typically there are a number of “low hanging fruit” design improvements that are low cost and low risk to implement. The measures focus on operational energy which generally makes up 70%-80% of the total life cycle impacts. The measures are detailed below for a standard apartment building with a mix of one and 2 bed apartments, please note these are indicative figures and will vary depending on final design, density, services and materials used.

Sustainability Measure

Typical percentage improvement
Gas hot water system 25%-30%
Lighting motion sensors/timers in common areas 6%-8%
Apartment Energy Monitoring 2%-4%
Behavioural Change Programs 2%-4%
Low flow shower heads (5l/minute) 1%-2%
Limit refrigeration space to less than 750mm 0.6%-0.7%
Ventilated refrigeration cabinetry 0.4%-5%
Total approximate 37%-45%

 

With implementation of the above measures the building will achieve approximately a 37% to 45% improvement sitting at a Silver medal rating. To achieve greater improvements renewable technologies are needed.

 

Renewable Technology Typical percentage improvement
Solar Hot Water (1m2 per dwelling) 3%-4%
Solar PV (1kW/ 10m2 per apartment) 5%-7%

 

The majority of medium rise flat roofs can easily accommodate the above with room left over for other elements such as flues and skylights. The low hanging fruit combined with some renewable generation will typically achieve around a 45-55% improvement.

 

 Achieving Targets – Best Practise

For higher ratings to be achieved, there will need to be upwards of 1 kW and per apartment and over 10m2 of roof space available alongside the measures detailed above. This can require careful consideration of roof designs from the outside and in some instances, consideration of options off-site such as community owned solar PV farms may be required.

Renewable Technology Typical percentage improvement
Solar PV (2kW/ 20m2 per apartment) 10%-14%
Solar PV (3kW/ 30m2 per apartment) 15%-20%
Solar PV (4kW/ 40m2 per apartment) 20%-28%

 

Roof Orientation for PV:

Capture3Once a residential building gets above 4 storeys, or a commercial building gets above 3 storeys, it will likely end up in a position where the solar technologies that are required are constrained by the roof space that is available. In this situation the design team should take roof design into consideration from an early stage and optimise it for solar panel installations. The following guidelines should be considered:

  • By installing panels “flat” on a roof, many moor panels can fit because they do not need separating for shading.
  • Shading from surrounding objects and buildings is an important consideration however it is rarely a problem in multi-residential buildings taller than their surroundings. PV can be very worthwhile even if partially shaded and can may still deliver significant carbon savings compared to other measures.
  • For designing roofs in this situation, the following considerations should be made.  Note that the below loss figure for varying orientation and pitch are applicable to Perth (latitude of 32 degrees):
  • The orientation of the roof can significantly aid the amount of PV or Solar Hot Water that can be installed in the diagram above

– North facing panels at 32 degree pitch gives optimum energy gain over the whole year (100%)

– Dropping pitch to 5 degrees only results in a loss of approximately 9% (91% of optimal generation)

  • If panels are to be pitched at lower than 10 degrees, consideration should be given to at least annual cleaning until it is proven that soiling is not effecting generation.
  • If possible, avoid hips in roofs as these significantly reduce the amount of PV that can be installed.  It is far better to pitch the roof in two directions only.  Even pitching north and south in two directions is likely to result in a better overall result than in four directions.  The south facing panels may generate less power per panel than the east or west, but more panels will be able to be installed because hips won’t have to be avoided and this will more than make up for the slight loss of efficiency in south facing panels.
  • Very wide gutters can significantly affect the available roof space for solar collectors.  Consider overhanging the roof structure over a required large gutter.
  • Protruding services that break up the roof space should be designed if possible on the south side of the building.  This reduces the losses due to shade for solar collectors across the whole roof.
  • Roofs with multiple heights are complex due to overshadowing.  If possible avoid this.

For solar hot water systems the same rules apply however slighting more consideration may be required to match demand with pitch, so a higher pitch to meet the higher winter water heating demand.  This is not such an issue with PV as it can be fed into the grid when generation is higher than demand.

 

Advanced Design

Some of the recommendations listed below represent paradigm shifts not only in actual construction but also in the marketing and sales strategies that may be required to ensure a developments viability. There may be times when it makes more sense to invest the money that would go into some of these expensive onsite solutions to other local projects that can deliver more value and higher CO2e savings. Examples of this may include Investments in street light upgrades, existing housing retrofits, solar panels on local schools and buildings, behaviour programs, community farms, bicycle infrastructure etc.

Functionality

The more people a building can house the less impact per person that building will have. Furthermore for every person that is housed in a sustainable building that takes one more person out of the average, unsustainable building – moving society towards a low carbon economy faster.

Typical multi-residential buildings have approximately 50% of the total floor area dedicated to actual living space, the rest tends to get tied up in common areas, car parks, plant rooms etc. By minimising the common areas you reduce impacts on two fronts: living area available for the same volume of materials, and reducing the operational energy required to light and ventilate the common spaces (this can typically take up to 15% of the total CO2e emissions).

 

ratio net dwellable area/gross Floor Area Life Cycle Reduction in Emissions
45%
50% -3.1%
55% -5.6%
60% -7.7%
70% -11.0%
80% -13.5%

 

There are numerous ways that common areas can be reduced:

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Space efficiencies can also be gained by increasing the number of stairwells whilst reducing the common walkway areas.

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Although stairs are likely to be the more expensive option, this could be recouped by adding the spare hallway space into each apartment, in the example above this provides an extra 8.75m2 per apartment.

Typology (Beds and bathrooms)

Environmental impacts can be reduced through increasing the occupancy of the apartments themselves. Whilst 2 bedroom 2 bathroom apartments are fashionable, with good design that (rarely used) spare bathroom could be a third bedroom instead. This provides an increase in the overall sustainable living space of the building without impacting on the floor area being constructed

 Materials

In many ways embodied carbon is equally (and perhaps more) important a consideration than operational energy. eTool LCAs will typically assume current grid intensities throughout the 100+ year predicted design life of a building. This means operational energy makes up around 80% of the total impacts. In reality over the next 100 years the grid will decarbonise and operational energy will contribute much less over time. The embodied carbon in materials on the other hand is locked in from the year the material is manufactured and transported to the site. There are many low impact alternatives to common materials in construction. Timber and CLT can be used in place of concrete and steel. Where concrete is necessary fly-ash or blast furnaces slag blends should be incorporated, these are waste products that can directly replace a proportion of the concrete thereby reducing its impacts.

graph 1

Timber veneers and plywood should be avoided due to the high impact of the glues and resins used in these products. Plasterboard also has very high impacts. Alternatives such as plain hardwood, bamboo or MDF represent significant savings. IF plasterboard is to be used 6mm sheets should be preferred to 12 mm sheets with acoustic requirements met through insulation which is typically low in CO2e emissions.

graph 2

Carpets (especially wool) should be avoided with cork or polished concrete finish preferable. If absolutely necessary carpets should be dark coloured (to avoid replacement through soiling) and plant based materials such as jute and sisal should be specified that have natural/non-synthetic rubber backing.

graph 3

Lighting

There tends to be little difference in terms of environmental benefit between CFL lights and L.E.D lighting Increasing natural light levels using solar-tubes, skylights or similar means less use of artificial lighting energy. Specifying lighter matte colours to surfaces such as the balcony, ceiling and walls will bounce light deeper into the dwelling thus increasing natural lighting. Light shelves in windows is another passive way to divert and bounce light deeper into the dwelling. Similar systems using adjustable louvres can also be used. Providing translucent shading material in addition to heavier curtains allow the option of diffused daylight to penetrate whilst maintaining privacy. The top of the windows is where light penetrates deepest into the dwelling, so it is important to ensure that this part of the window is not obstructed by drapery or blinds. Translucent partitions between rooms also allow light to be drawn into deeper rooms. Clerestory windows also provide a method of introducing more natural light into central rooms.  Ideally these should be utilised with higher ceilings and high reflectance surfaces in order to encourage light to penetrate.  In order to prove the value of these initiatives a daylighting simulation should be undertaken to ensure expense is not incurred for no benefit.  This will likely make this recommendation hard to justify economically (there will be many far easier wins elsewhere in the building.

Gas cookers over electric

In regions with fossil fuel dominated electricity grids such as WA, gas represents a large advantage over electricity for providing energy to cook with.  This is due to the heat and electricity losses associated with distributed power.  Burning the fuel (gas) at the source eliminates these losses and is a more efficient way of using the fuel. The majority of gas cookers sold today include safety features that automatically turn off the gas when no flame is present. Rinnai has also developed the ‘inner flame’ technology that produces a flame that is directed inwards which is about 27% more efficient than standard gas stoves. The drawback to moving to gas cooking is that a gas pipeline may need to be installed. If the implementation of this strategy is outside of the project budget the developer may offer the strategy as an upgrade package for purchasers. This eliminates the need for upfront capital while promoting best practices and educating the public.

Or Induction cooktops

An all induction cook-top is an alternative that could deliver carbon savings over a standard electric cook-top.  Induction cook-tops work by transferring electrical energy through induction from a coil directly to the magnetic pan. Only the area in contact with the coil heats up and therefore the cooker can be up to 12% more efficient than a standard electric conduction cooker.  The controls on an induction cooker are also far more precise giving a greater range of cooking techniques.

Car Park Ventilation

By applying a detailed engineering design to the car park ventilation systems, it is expected that the fan run times could be considerably cut down especially when natural ventilation is utilised.  Computational fluid dynamics would be utilised in this technique to determine how to best move air through the car park to maintain acceptable CO2 levels with minimum energy demand.  Gains may also be achieved in reduced ducting.  At least a 20% saving in ventilation may be achieved.

Biodigesters

Biodigesters turn food and or human waste into gas that can be used in cooking. Although not well established in western countries this technology has been used for hundreds of years in China and India. Communal or individual systems exist that may be incorporated into an innovative building design.

 Appliances

The appliances that go into the building can make a significant proportion of the recurring impacts.  Modern appliances tend to have fairly small warranty periods in relation to the lifespan of a building.  TVs in particular can often not last more than 10 years.  Ensuring that appliances are purchased second hand and those that are purchased new have a long warranty and are kept for as long as possible can provide significant carbon savings.  In this recommendation we have assumed each appliances lasts twice as long as the standard warranty. Where appliances are installed they should also be of the higher MEPS rating bands for energy efficiency.

Thermal Performance

Modern 6 star dwellings in Western Australia need very little in the form of heating/cooling. The developer with sustainability in mind will provide only ceiling fans for cooling and renewable biomass pellet heaters for heating. Bio Where air conditioners are provided they should be single split units which can obtain higher efficiencies generally than multi splits. A COP/EER of 5 is exemplary.

Tri-generation, deep geothermal and shallow ground source heat pumps can also be appropriate in very large developments with high demands such as precincts with swimming pools. However they entail very high outgoing capital costs and the environmental benefit should be considered carefully against other technologies.

Swimming Pools

Most importantly swimming pools should be appropriate for the size of the development. Proportionally 50m2 pool shared amongst 100 dwellings will have 100x fewer impacts per dwelling than the same size pool provided for a single dwelling. Where pools are installed they should ideally be naturally heated through ambient air and install pool covers that contain the heat when the pool is not in use. Typically including a pool cover which can operate automatically or manually for 8hrs per day during the pools closed hours has a 28% saving in the pools heating energy demand. Pool pumps efficiency should also be considered carefully, high-efficiency pool pumps of up to 9 stars MEPs rating are currently available on the market.

 Hot Water

Alongside solar thermal technology and low flow shower heads, an opportunity exists to warm the inlet temperature of the water by using a heat exchanger. Water exiting apartments in the sewerage drains will have a higher temperature than the normal inlet temperature of water coming into the building from the mains, particularly in winter.  By passing the inlet water over the warmer outgoing water, the temperature can be increased. A 5% reduction in energy demand of the hot water system can be achieved.

For communal systems there will be significant heat losses in the pipe carrying the hot water around the building as well as from the individual water storage tanks. Based on the conservative assumptions of a 25mm pipe with 25mm of insulation (125mm total diameter) the heat losses are estimated to increase the hot water demand by 10%. Correctly installed 50mm pipework insulation could therefore reduce the losses through hot water pipe by approximately 5%.

 

eTool

The door is always open at eTool for questions surrounding design decisions. If a project is in concept phase we are happy to sit down for an hour and discuss potential strategies and targets. Full targeting sessions are also available at low cost to determine more accurately the costs involved in achieving design aspirations. Following this our full LCA will provide the most detailed environmental assessment available.

 

Brown Paper Background

eTool International Residential Benchmark (Methodology Summary)

Below is a summary of our approach to the International residential benchmark.  A full EN15978 report on the benchmark model can be found here.  International Residential Benchmark Weighted x10 dwellings v28

In light of eTool’s recent exploration into global markets, we thought it prudent to create a “global” benchmark for housing developments.  eTool will be using this benchmark for all future housing projects. The reasons an international statistically mixed use benchmark is the most robust model to compare designs against are as follows:

  • The planet does not care what kind of house you build only how close it is to zero carbon. A mixed use benchmark provides a fair comparison of performance across different house types be it apartments, detached, maisonettes etc.
  • The planet does not care where you build your building, only how close it gets to zero carbon. Climate change is a global problem, whilst regional benchmarks can be useful for comparing similar buildings in the same area they can produce unfair results.  For example, a house built in a low carbon grid area (e.g. Brazil) may have emissions of 2 ton/person/year.  This may only be a small improvement against the average Brazil house as they both have the benefit of a low carbon grid.  Conversely a building in WA may have higher emissions (say 3 ton/person/year)  but despite having higher emissions than the Brazil case could show a larger improvement against the average WA house.  A single benchmark is the only way to give correct credit for the true sustainability performance of a building.

Before getting into the nitty gritty, it’s important to understand the purpose of the eTool benchmark, which is:

  • To establish a common measuring stick against which all projects are assessed so that any project can be comparable to another.
  • To create a starting point, or “average, business as usual case” from which to measure improvements.

Benchmark Form and Structure

The benchmark has been created to represent an average dwelling built in a developed country, the statistics for a range of developed countries have been population weighted and combined into a single theoretical average dwelling.

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The statistics used in the benchmark are based on data obtained for each country. The construction type and dwelling size statistics take new build data wherever available, as this data is generally reliable and represents a picture of the way buildings are currently being built across the developed world. For residential buildings there is a mix of houses and apartments. This is the latest breakdown of the new dwellings density mix across the countries considered in 2010:

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The occupancy is calculated by dividing teh countries population by the number of dwellings to give an average. This is weighted by population to give a global average of 2.52.
For the single dwelling element (59% of our average dwelling) a building structure has been modelled taking a cross section of commonly used construction techniques. In this instance, the data was obtained for U.S.A.  The U.S.A makes up the largest proportion of new housing in the developed world and is considered to represent a fair “average house.”  Construction techniques are unlikely to differ significantly enough to impact on the overall modelling, whilst brick houses may be more common in the U.K. and Germany, timber framing is far more prevalent in Japan and Sweden.

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A similar approach was taken with windows, internal walls, floors and roofs. The vast majority of those installed in new builds across America and Europe are double glazed and allowances have also been made for the smaller proportions of other window framing options currently in common use.

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For the multi-family dwellings, a standard concrete frame structure has been taken with one level of car parking and typical auxiliary and common layouts, such that the apartment living area represents approximately 50% of the total floor area of the building.  The total impacts of this building have been weighted on a per m2 basis and 56 m2 has been added to the model to represent the apartment element.

Benchmark Operational

Existing data has been used for operational energy, and arguably new build data would be preferable, but total existing data is generally a lot more robust (and readily available). Whilst new build energy figures were available for some countries, the figures tend to be from modelling completed for regulatory purposes and are therefore theoretical. In many countries there is a perceived “performance gap” between modelling results and actual consumption mainly due to differences in occupant behaviour, but also because of limitations in software and methodologies used for the modelling. The hope is that there will be continued industry effort towards monitoring of new build housing performances. Until further data in this area is available, we have a robust snapshot of how average buildings are currently performing by taking existing housing data.

The data for total residential fuel consumption was divided by the total number of dwellings in each country analysed. This was then weighted according to population to give a final figure for the average energy consumption of a developed country dwelling.

Capture7

End-use percentage estimates were then used to determine where this energy is being used in the dwellings.  Again, U.S. data[ix] has been used to represent the average.

Capture

Other impacts such as appliances and cabinetry and finishes have also been included by the estimated proportion of dwellings estimated to include these.

Capture8
The global average water consumption is considered fairly consistent across most developed countries with America and Australia having higher water consumption due to larger garden sizes.  A conservative nominal 169l/person/day has been assumed for water supply and treatment.

 

[i] Populations by country 2010 http://countrymeters.info/en/United_States_of_America_(USA)

[ii] Characteristics of New Housing U.S.A http://www.census.gov/construction/chars/highlights.html

[iii] Statistics Bureau Japan http://www.stat.go.jp/english/data/nenkan/1431-09.htm

[iv] EU Odysee Data 2008 downloaded on 11.7.2014

[v] Australian Bureau of Statistics Average floor area of new residential dwellings 2012 http://www.abs.gov.au/ausstats/abs@.nsf/featurearticlesbytitle/E9AC8D4A1A3D8D20CA257C61000CE8D7?OpenDocument

[vi] U.S. Energy Information Administration – Annual Energy Outlook 2014 – Energy Consumption by Sector and Source http://www.eia.gov/oiaf/aeo/tablebrowser/#release=AEO2014&subject=0-AEO2014&table=2-AEO2014&region=1-0&cases=full2013full-d102312a,ref2014-d102413a

[vii] Odysee energy database for EU and Norway (2008) downloaded from http://www.odyssee-mure.eu/ in July 2014

[viii] Statistics Bureau Japan Chapter 10 Energy and Water http://www.stat.go.jp/english/data/nenkan/1431-10.htm

[ix] U.S. Energy Information Administration Residential Sector Key Indicators and Consumption http://www.eia.gov/oiaf/aeo/tablebrowser/#release=AEO2014&subject=0-AEO2014&table=4-AEO2014&region=0-0&cases=full2013full-d102312a,ref2014-d102413a

 

 

DSCN8615

eTool Brings Whole of Building LCA to Brazil

Adding to the mix of a great and festive culture, strong and growing economy, and abundance in natural resources, Brazil will now have access to eTool services and eTool LCD software to conduct whole of building Life Cycle Analysis. This exciting announcement is part of eTool’s global collaboration in building design and is an opportunity to provide Life Cycle Analysis services to a nation that is not only in continuous and fast development, but can also act as a showcase to the world for sustainable development.

“LCA is a fundamental concept in designing for sustainability and I’m excited to help eTool develop new projects in Brazil. When I came to live in Australia, one of my main goals was to take something back that would enhance the quality of life for people and also guarantee development in balance with nature, and that’s exactly what eTool is about”, said Henrique Mendonça. Henrique has worked for over 2 year as a Life Cycle Engineer at eTool and is now the Business Development Facilitator for Brazil.

Brazil is the 7th largest economy with over 200 million people. Rapid economic development has pushed millions of people from a low socioeconomic status ,up to middle class, which has increased the demand for basic infrastructure such as electricity and transportation as well as the services desired for this higher income population. Brazil’s infrastructure by necessity is going through some major overhauls such as ports, airports, roads, railways and energy systems. Worldwide demand for natural resources and food push Brazil’s national contribution to global warming in an upward trend due to fossil fuel emissions as well as deforestation and land degradation.

Strained resources and the rising demand for development provide opportunities for product manufacturers, designers, consultants, builders and developers to embrace the concept of LCA as part of intelligent building design. Certification standards on building environmental performance such as LEED, AQUA, PROCEL EDIFICA, and others, all include LCA as part of the design process, which is further indicative of the global trend towards LCA as a standard methodology for good building design. Research and development is also moving forward with academic partnerships in Brazil working on developing local life cycle inventories, and looking at the design and use of supporting tools.

“I believe education is a major goal for the LCA industry in Brazil at the moment. In order to support that, eTool is creating local case studies and producing relevant content, providing technical support to designers though webinars and creating local partnerships to spread the concept of life cycle design. There is a lot of expertise in LCA developed by eTool in Australia that will be applicable to Brazil, as international standards that eTool comply with (ISO 14040 and EN 15978) are guiding the future of LCA worldwide”, says Henrique, after meeting with industry professionals during his visit in Brazil early this year.

‘Think global and act local’ is a well-known statement in our society, and eTool is proud to be on the journey towards not just thinking globally, but acting globally. Stay tuned as we continue to bring you news from the tropical lands of Brazil and our other global collaborations.

 

Expo GBC 2014Henrique with his parents at the GBCB Green Building Conference in Brazil.

clouds_banner

A Rough Carbon Budget For Buildings

Why A Carbon Budget?

As we learn more about greenhouse (GHG) pollution and global warming we’re getting better at understanding cause and effect. There’s lots of complexity, obviously. However, the variables are slowly being identified, tested, and fed back into the models. Last year the media latched onto a story that global warming had ceased. I wish the stories indeed did debunk climate theory. Unfortunately not. We’re just in a period of warmer oceans and cooler atmosphere. Will Steffen explained this in a very objective manner when questioned in the Senate Committee on Extreme Weather Events (see page 12 of this transcript). Anyway, all the scientific research into climate change now enables us to make predictions of warming based on the volume of GHG we release into the atmosphere. And we’re even able to make predictions about what effects this may have. The below infographic is an incredibly good summary of these predictions, and the background data is rock solid if you’re interesting in looking into this further.

KIB_Gigatons_CO2_Apr14_A4

 

It’s pretty clear we need to try to limit warming to two degrees. The big reason for this is that there are tipping points for our climate, which trigger events that force more warming. Some examples include melting of arctic tundra and stored methane, release of methane from sea bed methane clathrates or the collapse of the amazon due to drought and fire. We don’t actually know at what point these events will happen and they may even happen before we get to two degrees warming. What we do know, is that it’s highly likely they will happen if we keep warming the planet. Even without these events occurring, we’re on track for four degrees of warming by the end of the century. Four degrees will probably put so much pressure on food resources there’ll be major global conflict. Not over land, or oil, but over food. It could get very messy.

A Per Capita Carbon Budget

So, we need to work out how much more carbon we can release to avoid these events, we need to set a budget. There is actually a level of GHG pollution that the planet can happily cope with naturally through chemical and biological sequestration. It’s a rubbery number, but sits at about 2.0 tCO2e per person. In 2050, accounting for population growth, we really need to be aiming for approximately 1.0 t CO2e per person per year which would actually enable us to reduce the GHG in the atmosphere. This, then, is our sustainable level of GHG emissions on a per capita basis. Some calculations on this here and here (with slightly different results).

Apportioning to Economic Sectors

Relating this to buildings is a little difficult because we don’t really know how the economy is going to decarbonise. There might be breakthroughs in certain sectors that enable it to effectively zero its GHG emissions, whilst others may find it very hard to shake the existing thirst for fossil fuels (or land use change). If however, we assume that all major sectors of the economy decarbonize together, then we can essentially take each sector’s current percentage of GHG emissions and multiply it by 1.0 t CO2e to yield the per capita budget for each sector. This is one of the best diagrams I have come across to explain GHG flows through the economy. It’s taken from a great publication called Navigating the Numbers.

GHG Flows

GHG Flows

In the diagram, the column “end use activity” is what we need to focus on to determine how current GHGs are apportioned across our economy. Directly, buildings are responsible for 15.3% of GHGs. However, there are a lot of indirect emissions that relate to buildings if you take a life cycle approach to measuring an impact of a building. These include transportation of materials to the site, transportation of equipment and labour, construction energy, emissions relating to materials production, further transport, and equipment use to maintain the building. Then deconstruction, demolition and landfill emissions. There may also be land use change emissions associated with some building products, or urbanisation as well. If we make the below assumptions regarding the allocation of these indirect emissions to buildings (which are not based on research, but I believe are reasonable), we land at a number of 26% of total GHG emissions relating to buildings.

  • 60% of building energy use relates to electricity to determine distribution and transmission losses
  • 70% of coal is used for electricity or downstream processes attributed to buildings
  • 30% of oil and gas gets used for electricity or downstream processes that can be attributed to buildings
  • Unallocated fuel combustion is proportionally attributed to all end uses
  • 1% of air transport and 10% of all other transport relates to building construction, maintenance, design or management.
  • 50% of iron, steel and cement is used in building construction or maintenance
  • 10% of chemicals are used in building construction or maintenance
  • 25% of aluminium and non ferrous metals are used in building construction or maintenance
  • 10% of other industries are providing materials or services to building construction or maintenance
  • 25% of land use change emissions due to harvest and management of forests relate to construction and maintenance of buildings
  • 15% of all landfill gas emissions relate to disposal of construction waste
  • 75% of waste water treatment emissions relate to building waste water

Building Related Emissions

These assumptions and calculations at this point are moving pretty quickly towards “back of the envelope”. The only way I can really justify this is that there are no numbers out there telling us what is a sustainable level of GHG emissions for buildings. So don’t hang your hat on these numbers, however, in lieu of more robust calculations, here’s a starting point.

A Carbon Budget For Buildings

We can now set a rough carbon footprint for environmentally sustainable buildings at 260kgCO2e per year per capita. This will be split between residential dwellings and other buildings. If we assume the split is the same as the direct GHG split in the “Navigating the Numbers” flow chart, that gives us a budget of 168kgCO2e per year per capita for residences, with the remainder of building related GHG distributed to workplaces, hospitals, civic buildings etc. We haven’t done any work on how to distribute the remainder amongst these other buildings as it gets pretty complex but watch this space. For residential buildings in Australia, we have a lot of work to do to achieve this budget. See the below chart for a visual on that.

Australian Residential Buildings

Close

Although these numbers require more work to confirm, they provide some guidance in lieu of other sources. They display the extent of the challenge. In particular, note in the last chart that the target is many times less than even the embodied GHG of current “average” buildings in Australia. I extend on this topic in this post, exploring some lateral thinking to solving the challenge of hitting our carbon budget for buildings. Note, this is an update on the video attached to the next post so you may spot a difference in the figures.

 

 

Brown Paper Background

eTool Residential Benchmark For Australia

Before getting into the nitty gritty, it’s important to understand the purpose of the eTool benchmarks, which is:

  • Establish a common measuring stick against which all projects are assessed so that any report is comparable to another (for the same type of project).
  • Create a starting point, or “average, business as usual case” from which to measure improvements.

The benchmarks are not an average of existing stock but rather an average of new stock. Hence any efficiency requirements etc in the Building Codes etc are taken into account. When comparing to the benchmark, the target is pretty simple. Effectively Australia has to drop it’s GHG emissions by about 90-95% on a per capita basis for us to become sustainable global citizens. With this in mind, what we should be trying to do is drop our building’s emissions by 95% against the benchmark to ensure the building is stabilising the climate.

Creating the business as usual benchmark is pretty complex. For residential buildings in Australia there is a broad density mix from detached through to apartments. This is the latest breakdown of the new dwellings density mix in Australia (from ABS) over the last two years:

DetachedSemi DetachedLow Rise ApartmentsHigh Rise Apartments
Proportion of New Dwellings61%13%7%19%

For each of these density types, eTool have formulated a BCA code compliant building. We have then created a nominal statistical mix of  floor areas to match the average new dwelling size in Australia (214m2). In this way we come up with a “dwelling” that is a mix of densities and matches the size of the average Australian dwelling.

A similar approach is taken for operational energy. In this case we first research the most up to date residential energy estimates for Australia.  This data comes from ABARE Energy in Australia 2012. It gives us guidance on the total energy used per household (existing housing stock) in Australia and also the fuel mix split (electricity, gas, wood etc). We then use other end use percentage estimates to determine where this energy is being used in the dwellings.  The most commonly quoted breakdown of household energy use in Australia is from the “Your Home Technical Manual” which is actually a reference to the “Energy Use in the Australian Residential Sector, 2008”.  This report is commonly referred to as the “Base line report”.  This report itself actually states:

The study identified a paucity of end-use data for residential energy use in Australia, particularly in regional areas. Some of the appliance energy consumption estimates used in this study rely on research that is 15 years old or, alternatively, on work undertaken in New Zealand. 

The study recommends an comprehensive end use energy monitoring program which we believe is being undertaken. Until the results are out we’re a feeling our way in the dark a little.  Not withstanding this, the study is useful to guide the decisions about where we’re using our energy. To verify the Base Line Report figures we also took some state government studies (eg Sustainable Energy Development Office in WA) and statistics from other countries (notably the BRANZ HEET study and also stats from the US). The largest unexplained discrepancy seems to be in the estimates for heating demand.

The Base Line Report suggests that 38% of total end use energy in Australia homes is dedicated to heating and cooling purposes.  This seems very high given the following facts:

  • The comprehensive HEET study from BRANZ in New Zealand (a much colder climate, and one dominated by heating requirements) only calculated 34% of end use energy dedicated to thermal performance.
  • The WA SEDO estimate for thermal comfort energy demand is also much less, hence it’s hard to believe the additional demand is due to cooling.
  • A large percentage of Australia’s population (Perth, Sydney and Brisbane) all live in quite mild or warm climates where heating would not make up more than 50% of the thermal control energy demand (and less still of the actual end use energy demand)
  • Heating is the most end use energy intensive thermal comfort mode as cooling typically utilises either apparent cooling methods (evaporative or fans) or heat pumps, both of which have effective Coefficient’s of Performance of 2.5 or more. This means for every one unit of energy input, 2.5 units (or more) of heat is dissipated of pumped from the dwelling when cooling. Heating on the other hand requires more energy than the actual heat load demand theoretically required to heat a space (or at least the same amount). This is mainly due to flue losses.

The high estimate in the Base Line Report may be linked back to the ABARE Energy stats which are also questionable. The Energy in Australia 2012 document from ABARE gives a biomass figure for residential energy use that equates to 6280MJ / household /annum.  When this is calculated in terms of mass of wood, it works out at 400kg of timber per household in Australia.  Even if one in every 5 houses (studies suggest it’s more like one in every 10) is using a wood heater that was their primary source of heat, that’s 2t of wood per annum they would need to be burning in order for the ABARE data to reconcile. To give you an idea, an average small box trailer full of wood is about 250kg. We’re not convinced there’s 2 million households in Australia receiving 8 trailers of wood per annum to heat their homes. The BRANZ HEET study further supports the proposition that ABARE have overestimated biomass consumption in the Australian residential sector.  BRANZ calculated that each wood heater uses 4,500kWh (one tonne) of wood per annum.

Without making any adjustments to either the end use demand figures, or the top down supply figures the numbers don’t reconcile very well. For example, trying to “fit” the biomass, gas and LPG energy into the end use break down “squeezes” electricity out of the hot water and space heating categories. There simply isn’t enough low grade heat requirements in dwellings to account for all the biomass. However, when we aligned the biomass use predictions with BRANZ, and adjusted the demand figures to better match some of the competing studies we got good reconciliation.

This also supports the total residential demand estimate in the Base Line Report which is quite a bit lower than the ABARE stats.

Once we knew the amount of energy the existing housing stock were using, we then determine how this would differ in new dwellings.  Some energy use would remain pretty static (eg appliance use and refrigeration). Lighting, hot water and heating and cooling have relatively new BCA code requirements focussed on energy efficiency. For these end categories appropriate adjustments were made to account for the newer technologies and associated demand.

Heating and Cooling (Thermal Control)

The heating and cooling energy requirements are the most complex, as there are very few stats on what equipment is being deployed in new houses. The NatHERS system does help this situation and we make an estimate of the deployment of heating and cooling technologies in the current housing stock as follows:

  1. Estimate the heating verse cooling loads for buildings in the top 20 populous NatHERs climate zones (85% of Australia’s population). This works out to be 60% heating and 40% cooling.  
  2. Estimate the efficiency of each type of heating and cooling technology
  3. Estimate the deployment of each type of heating and cooling technology
  4. Adjust estimates such that total energy consumption matches our adjusted ABARE figures and the split in thermal demand matches the NatHERs weighted average for Australia

This then informs our decisions about what people are likely to choose for new houses.  The summary is found in the following tables:

Electric Heat PumpElectric Fans or Evaporative Coolers
Existing Stock Cooling Demand50%50%
New Housing Stock Cooling Demand60%40%

Electric Heat PumpElectric RadiatorsGas FluedGas Internal HeaterWood Heaters
Existing Stock Heating Demand20%10%17%51%2%
New Housing Stock Heating Demand35%0%20%40%5%

For each major BCA climate zone or population centre then simply divide the NatHERs energy demand estimates for a 6 star dwelling for the building between these categories and apply appropriate efficiency or COP figures to determine what the end use energy demand will be.

Hot Water

The building codes have now banned the use of electric resistance storage hot water systems in all residential buildings apart from class 2 building (strata buildings). Some state governments also discourage the use of electric heaters in class 2 buildings. This has led to a huge shift from electric storage hot water heaters to gas, solar, and heat pump units. This is a great thing for reducing the carbon intensity of the delivered hot water to dwellings (see more explanation on hot water fuel types here).

Using the same reconciling procedure between the end use energy estimates and the adjusted ABARE data we get the following mix of fuel uses for meeting demand in Australian existing housing stock:

Fuel Contribution to Water Heating Demand of Existing StockFuel Contribution to Assumed Water Heating Demand of New Stock
Natural Gas and LPG77%79%
Electric15%13%
Solar8%8%

Note, this doesn’t imply that 77% of water heaters are gas fired, it implies that 77% of energy used by water heaters is gas. The difference is that gas water heaters have lower efficiencies than electric resistance heaters (99%) or heat pumps (approximately 270%). With a gas water heater, depending on the age of the heater, it may be as low as 50%, and won’t get much better than 85%. So the mix of heaters installed in existing buildings is actually more slanted towards electric.

New buildings will tend more towards gas due to the current BCA requirements. With this in mind, we’ve used the figures in the right hand column for the split in fuel use for new dwellings.

gas v electricity

Are You Using Gas or Electricity In Your New Home?

We are passionate about reducing the carbon intensity of buildings first and foremost. It’s what we live and breathe, so we try to look at every consideration when putting our recommendations forward…we don’t take it lightly! Here we give some key considerations to help you make a sound decision when choosing between gas or electricity.

Industry and government have portrayed electricity as a clean and efficient source of energy, and it is, at the point of use. Perceptions of gas (sorry, “Natural Gas”) are similarly affected by public opinion and government policy that focus on the point of use. This ‘point of use’ perception is reinforced by the way most people interact with electricity and natural gas in their everyday lives, flipping a switch or turning on a burner and paying a monthly bill. They rarely see or understand the generation side of electricity, the power plant, or the extraction and transportation of natural gas or the ultimate carbon emissions associated with combustion.

The Life Cycle Story of Electricity

Apart from solar photovoltaic (still a tiny contributor to most electricity grids), all our electricity starts life on the output side of a turbine. These turbines are usually driven by steam, but there are some power plants that use wind or water (Hydro). So where does the steam come from? To make it we need heat, and lots of it.  At present we’re getting the overwhelming majority of this heat from coal or gas (the only real exceptions here are reactors that use nuclear power, geothermal plants that use the heat deep under the Earth’s crust, or solar thermal energy).

Coal is the cheapest form of heat for power plants, unfortunately though it’s also the dirtiest. The furnace exhaust of a coal-fired boiler is full of green house gases and also abrasive fly ash which renders it very unsuitable for heat recovery (it basically wears components out way too quickly to make it viable). In fact, most coal-fired power plants are lucky to capture one third of the heat energy as electricity.

When power plants use gas, there are two advantages. Firstly, burning gas releases less greenhouse gas than coal for equal amounts of heat (it’s still very bad for the planet, but not as bad as coal). Secondly, the waste gases produced from gas-fired turbines can be sent through a heat exchanger which drives a secondary turbine. The combined cycle gas fired turbines capture up to 60% of the heat and turn it into electricity (nearly twice as efficient as normal coal-fired plants).

Once the electricity is produced, we lose more of this energy during transmission and distribution. In Australia, about 7.5% of the electricity generated at the power plants is lost before it gets to the consumer. So when you look at the life cycle of fossil fuel generated electricity, you can see that we’re not getting much bang for buck.

There are also some other minor hidden impacts of electricity generation, although these impacts are very small compared to the CO2 released during combustion. They include:

  • Parasitic loads, which basically means they use some of the electricity generated to run the plant itself.
  • The carbon emissions associated with extracting the fuel source. This can be due to fugitive emissions (for example, methane that escapes from a coal seam as it is mined, crushed and transported, or gas that needs to be flared during processing)
  • The carbon emissions associated with transporting the fuel to the power plant
  • The embodied emissions of the power plant infrastructure

Using electricity in a building for heating water, cooking or space heating is the final step in the chain. The use of electricity at the home doesn’t add any environmental impacts (you don’t release any CO2 in the building, that all happened up stream).

The Life Cycle Story of Gas

Likewise, the natural gas used by a building must be extracted from the ground, processed or refined to remove impurities, and finally transported to the residence. All of these extraction, processing, and transportation steps require energy. And of course there’s the fugitive emissions of gas that escapes at the well, refinery or during transport. In total however, direct use of natural gas in the home is usually far more efficient than sending it to the power station to turn to electricity before returning that electricity to your home. The valid concerns regarding the latest significant source of gas production from “fracking” should not be discounted and may alone be enough to counter any climate change argument for the use of gas.

Of course when you burn gas you emit a lot of carbon dioxide at the building. In most cases however, you can capture a lot more of the heat than is usually captured by your electricity generator when they burn fossil fuels (particularly if they are relying largely on coal which is certainly the case in Australia). For example, good quality gas storage hot water units and instantaneous water heaters now run at 85% efficiency as opposed to coal-fired power plants (30%) and combined cycle gas-fired power plants (55%). So generally you get more “use” out of the gas by burning it on site.

Some Comparisons

Let’s now look at some examples of how electricity compares to gas in terms of local grid networks in different regions. Below we estimate the energy demand of an average house (2.4 people) and look at how that can be delivered with a range of technologies using both electricity and gas. We have chosen a number of regions to demonstrate the importance of local characteristics (largely relating to electricity energy sources).

  • Victoria:  Present heavy reliance on black and brown coal for electricity, standard gas supply impacts
  • Tasmania:  High renewable hydro content for electricity, standard gas supply impacts
  • Western Australia: The home of eTool, electricity generated largely by gas and coal fired plants with quite low thermal efficiencies, standard gas supply impacts
  • United Kingdom:  A fairly typical greenhouse gas profile for Europe (mix of gas, coal and nuclear with small but growing renewables content). Far lower greenhouse gas intensity than the average Australian electricity supply. Standard distributed gas supply impacts
  • Sweden: A very low carbon electricity grid. Gas supply not common, assumed standard distributed gas impacts

 

Cooking – Cook Tops

 

Technology

Assumed Technology

Efficiency (%)

End Use Energy Demand (MJ)

Greenhouse Gas Emissions (kgCO2e / Annum)

Victoria

Australia

Tasmania

Australia

Western Australia

United Kingdom

Sweden

Electric Induction

85%

1,273

492

140

343

219

24

Electric Element

75%

1,443

558

159

389

248

27

Gas Ring Burner

40%

2,705

167

163

186

186

186

 

Cooking – Ovens

Technology

Assumed Technology

Efficiency (%)

End Use Energy Demand (MJ)

Greenhouse Gas Emissions (kgCO2e / Annum)

Victoria

Australia

Tasmania

Australia

Western Australia

United Kingdom

Sweden

Electric

75%

481

186

53

130

83

9

Gas

60%

555

34

33

38

38

38

 

 

Water Heating

Please note that water heating load would vary depending on climate. For simplicity in comparison we have assumed a mild climate in the below energy demand calculations. We’ve applied the same demand across all regions so the carbon emissions are comparable between the electricity grids for the same demand profile (despite the fact there’s no mild climates in Sweden!). Similarly we’ve assumed the same solar radiation (an average of Australian capital cities approximately weighted by population). Note that the conclusions drawn below assume standard sized hot water systems with typical efficiencies, tank heat losses and solar collector size (where applicable).

 

 

Technology

Assumed Technology

Efficiency (%)

End Use Energy Demand (MJ)

Greenhouse Gas Emissions (kgCO2e / Annum)

Victoria

Australia

Tasmania

Australia

Western Australia

United Kingdom

Sweden

Electric Storage

99%

8,159

3,605

1,025

2,514

1,603

173

Gas Storage

85%

9,503

670

654

647

747

747

Gas Instantaneous

85%

7,357

519

506

501

579

579

Heat Pump (COP3)

300%

2,692

1,190

338

830

529

57

Heat Pump (COP5)

500%

1,615

714

203

498

317

34

Solar, Electric Boost

8,138

927

372

692

496

189

Solar, Gas Inst. Boost

6,489

250

247

246

263

263

 

Note that in many mild climatic regions families can successfully turn off their boosters for solar hot water systems and run on 100% solar.  The above calculations however assume “average” use of the system, so the booster is left running and switches on whenever the water temperature drops below the set point.  There is also a requirement for hot water systems to periodically heat themselves up to a high temperature to ensure that legionnaires diseases doesn’t get established, so this also influences energy use regardless of hot water demand.

Space Heating

The following figures assume a conditioned space of 180m2 and a heating energy requirement of 50MJ/m2/year which about average for a new compliant house in Perth. For simplicity in comparison we have assumed the same ambient temperature in different regions to calculate the below technology efficiency.

 

Technology

Assumed Technology

Efficiency (%)

End Use Energy Demand(MJ)

Greenhouse Gas Emissions (kgCO2e / Annum)

Victoria

Australia

Tasmania

Australia

Western Australia

United Kingdom

Sweden

Elec. Air Source Heat Pump (COP4)

400%

2,591

1,002

285

698

445

48

Elec. Air Source Heat Pump (COP5)

500%

2,058

796

226

555

354

38

Gas Heater, Flue, High Efficiency

75%

13,333

822

803

795

917

917

Wood Pellet Heater

95%

10,526

25

25

25

25

25

Is This Enough Information to Make a Decision?

What about if our grids use more renewables, and the carbon intensity reduces?
This is a really valid point that needs to be considered carefully. If the advantage of using gas is marginal, definitely think twice about implementing it over the electrical option. We know that as governments respond to climate change the carbon intensity of electricity grids will drop, quickly eroding any advantage that the gas solution may have had. Australia is lagging a little in this regard; we’re a very large emitter per capita and have secured some of the easiest targets to obtain in our Kyoto negotiations. That said, the government has committed to reducing total greenhouse gas emissions by 80% on year 2000 levels by 2050. That’s only 37 years away and most buildings we knock up today will still be around at that point. With this in mind, there needs to be a very clear advantage in using gas over electricity to justify its use.

There is a slim possibility that existing gas networks may be utilised for distributing renewable gases. This is already happening in some innovative communities where sewer gas is being collected, refined and sent back to apartments for cooking. This may somewhat alleviate any concern building designers may have been encouraging the use of what is essentially a fossil fuel network (natural gas) over electricity grids that can be more easily transformed to renewable sources.

What About Solar Electricity?

Now begins the philosophical debate. If you have a roof top solar PV system large enough to meet all your home energy demands with 100% clean renewable energy, would you use gas or solar electricity for your heating sources?
Electricity seems the obvious choice. Interestingly though, it may not be when you look at the net benefits of choosing each option. Let’s say with your solar PV system, you are energy neutral, that is you use as much as you generate. Of course you need to export into the grid in times of high generation, and import when your usage outpaces your production, but over a whole year you’re energy neutral.

If you’re doing this whilst cooking with electricity and then you swap to gas, you’ll be using a little more energy in the building as your gas cooking appliances aren’t as efficient as electricity. That said though, you’ll be exporting more electricity as you’ve displaced some demand with gas. These electricity exports will be reducing the demand for the normal fuel sources used by your generators. If this is coal, then the net result will be better for the environment as your greenhouse gas “credit” for exporting electricity will be bigger than the impact of using gas at the home. There are numerous variables that you may want to consider here, the most important of which is probably when you’re exporting and importing and how that relates to the generation of fuels being employed during those periods.

Researched and written by Henrique Mendonca and Richard Haynes

 

Research Sources

http://www.climatespectator.com.au/commentary/its-time-rip-gas-networks

http://renomart.com.au/gas-and-electric-cooktop-guide/

http://www.c2es.org/publications/natural-gas-commercial-buildings

http://www.c2es.org/publications/natural-gas-residential-sector

http://en.wikipedia.org/wiki/Induction_cooking#cite_note-19

http://www.choice.com.au/reviews-and-tests/household/kitchen/ovens-and-cooktops/cooktops-buying-guide.aspx

http://theinductionsite.com

http://www.fishnick.com/publications/appliancereports/rangetops/Eneron_Pot_Testing.pdf