eTool LCA Software Updates – Summer 2014

EN15978 Compliance

The last few months have been hectic for our software development team. We brought the software into line with the European standard EN15978 – Sustainability of construction works – Assessment of environmental performance of buildings – Calculation method.  We undertook so eTool could be used to gain innovation credits in Green Star projects.  For out international audience, this is a environmental rating scheme managed by the Green Building Council of Australia.

Technically the update was a big challenge, EN15978 a very comprehensive standard with quite strict rules regarding how the LCA calculations should be conducted.  It’s a piece of work we planned back in 2012, we did need that little commercial push to undertake the change, and the opportunity to utilise eTool LCA for Green Star projects provided this.  We are really happy that we managed to complete this piece of work.  We really think the planet has a lot to benefit from through this standard, and hopefully through the use of eTool LCA.  Here’s some reasons:

  • EN15978 was written by CEN technical committee 350 who are also developing other standards to meet there overall mandate of delivering standards to holistically assess the sustainability of construction works.  This is really exciting.  It effectively draws a line in the sand and gives really solid guidance on how we should be assessing the buildings.  It includes social, economic and environmental considerations for sustainability.
  • A good Life Cycle Assessment is without doubt the best way to measure and improve the environmental performance of something.  This has been recognised by CEN TC 350 who have relied on it nearly exclusively for the environmental assessment of buildings.
  • CEN TC 350 also developed a standard for the assessment of building products.  These will be used by the new ECO EPD framework being developed in Europe which will align most of the major EPD Program operators.  Now this is exciting.  Finally, we have an international system that reports truly comparable data for construction products.  It’s equivalent to nutrition labelling for building products (substituting health info with environmental info).

All this means the stars are nicely aligning for low impact buildings.  There’s a huge opportunity to cut through the greenwash if industry uptakes this approach.  One of the things we love about this approach is it actually enables policy makers to set budgets in order to ensure we hit sustainability goals.  I’ve written about this concept and how it might be approached here.

Software Speed Improvements

Users during the last 12 months would have noticed that at times, particularly for very big designs, the software laboured.  It was getting pretty frustrating for our ops team who were working more and more on complex LCA models for large projects.  We’d delayed tackling this problem because it required a massive re-write of the back end.  There’s nothing worse than spending two months labouring on a software improvement project, then delivering the result which looks exactly the same!  It was a very nice change though, to give you an idea of the performance improvement, we had a large test design that was taking the best part of four minutes to save, now it’s taking just two seconds.  The big driver for this was actually to enable more features to be introduced to eTool LCA that would have otherwise slowed it down further.  There’s more coming!

Record Recommendations

This is probably  my favourite new feature.  It makes the job if modelling and tracking improvement ideas very easy.  I can honestly say this has enabled our operations team to significantly increase the research time we can allocate to identifying more improvement ideas.  Less time doing little admin tasks like copying and pasting data between eTool and spreadsheets, and more time focusing on reducing the impacts of the design.  All users need to do now is hit record, model the improvements, hit stop and every change to an impact due to that improvement will be recorded at different life cycle stages of the building.  And it’s recorded for every indicator too, so you can see how much carbon you saved verses how much money you saved.   I love using this feature.  Check it out.

Solar Panels

Cleaning dusty solar panels

solar cleaningSo after years of wondering how much impact dust had on reducing the output of a Solar PV system I finally decided it was time to get around to running my own experiment.

You’re probably asking “why didn’t he just google it and find some nice scientific paper that told him how much of an issue the dust was?”. Well I have spent a fair bit of time looking and still haven’t found any nice simple scientific papers that provide a simple enough answer for me. The numbers that do get thrown around range from anything between 1% to 50% which doesn’t really help in answering the basic question “how often should I be cleaning my panels”. I have listed a few good ones below but if anyone can send through some new links I’d be most appreciative.

Anyway I felt the best thing to do was to run a good old back yard (well roof top) experiment on my parents Solar PV grid connect system in Perth Western Australia. I installed this system back in June 2007, so coming up to it’s seventh birthday, and it hasn’t missed a beat, caused a house fire, electrocuted anyone or blown up the local network. It’s provided beautiful, problem free renewable energy and even almost paid for itself. Back then Solar PV grid connect system retailed for around $10Wp installed and now we are down to around $1/Wp, nice learning curve. It was nice just to get up on the roof to reminisce about the good old days as an installer and remember how fast the renewable energy industry has moved.

Enough reminiscing – back to the subject!

The system hasn’t been cleaned (other than rain) for over five years and Perth has just had it’s driest summer on record, so if they was ever going to be a “dusty to the max” situation the time was now.

The system is 2.79kWp with 18 x 155Wp BP Solar poly crystalline panels (yes back then 155Wp was considered a pretty big, efficient and fandangled panel) coupled with an SMA SB2500. It’s orientated pretty close to due north at around 30deg pitch on some custom made “Alex Bruce” welded steel frames.

I waited until I had two fairly similar days in solar irradiation and temperature lining up consecutively (10th and 11th of March). I then recorded the total energy output on day one, cleaned them after the sun went down and then recorded the total energy output after day two.

Drum roll…………

  • Day one = 13.68kWhr
  • Day two (after cleaning) = 13.59kWhr

A drop of 0.7%!

Now before you decide that you should go through dust on your panels I need to mention a couple of details. Solar irradiation (how much the sun did shine without clouds or stuff in the way) was pretty much spot on but it was hotter on day two (33degC vs 28degC) with a little bit less wind to help cool the panels. For those of you who know that panels don’t like getting too hot you’d probably be spotting a pretty big flaw in my highly scientific experiment.

Under these conditions I would have expected a 2-3% drop in performance. This was verified by going onto PVOutput and seeing how a few systems in the same area performed over the same two days (I had to assume some sneaky bugger hadn’t gone and cleaned them on the night in question).  I took an average performance for three systems and it seemed to show a drop of around 3.2% between the 10th and 11th of March. So instead of our system dropping by 3.2% it only dropped by 0.7% suggesting the cleaning saved or improved performance by 2.5% which is a pretty good outcome.

However the devil is in the detail.

When I was cleaning the panels I started with the hose on mist to see how much dirt would come off while simulating rain. Again very unscientific but I would suggest 70-80% of the dirt including the odd bird poo came off with the fake rain. Funny thing is we were forecasted for a storm the next day so I probably could have just let nature do the cleaning. Furthermore, this would suggest that 70-80% of the dirt has only been there since the last rain, so this massive 2.5% improvement only is really only over the last few months. Over the course of a year, I reckon I could improve the situation by maybe 1.5% at most by regular cleaning.

There was a bit of lichen starting at the corners and I had to scrub at these bits to get them off. If these had grown further and ended up over the cells then there would be more substantial drop in output (might have taken another five years). I’ve also seen branches and leaves sitting over panels so it’s definitely worth having a periodic look or monitoring your systems output (saves you getting on the roof) to pick up any substantial decrease in performance.

Now for the money side. Everyone is on different tariffs so to make it easy I’ll base my calculations on $0.25/kWhr. This system is now (after seven years) probably knocking out 10kWhr/day average over a year. So a 1.5% improvement would amount to about $14/year. It took me about 20minutes to get on the roof, give them a clean and get back down (excluding the ten minutes of reminiscing). I’ll excluded travel time and costs as I rode around on my bike for exercise and like visiting my parents anyway. With this all in mind I’d be worth $40/hr cleaning panels. If you did it for a living and included travel, writing out invoices, insurance etc you’d probably be down to $10/hr.

I should also mention I went through about 50l of good drinking water and a squirt of washing liquid in the process. I think the broom could do another 100 or so systems before the bristles fell out…

On the environmental front you could suggest that the cleaning will save another 50kgCO2e/year from avoided fossil fuel burn so maybe that alone is enough motivation to get on the roof and give them a scrub.


I think I’ll wait for the rain to clean them next time but if I ever feel like a good reminisce about how fast things have moved for renewable energy, I’ll take a bucket and a broom and head on up to the roof….



The above story is just one slightly scientific anecdotal experience and:

  • If you’re in a dryer dustier place than average suburban Perth Western Australia,
  • or if your panels are much flatter (less than say 10deg pitch) and wont self clean as easy,
  • or you’re in the path of some large migratory birds topped up on mulberries,
  • or you’re directly under very low flying air craft (see link below),
  • or you just like things being clean….
  • or you just may think differently


Some links with much more scientific rigour behind them:

Cano, J. (2011). Photovoltaic Modules: Effect of Tilt Angle on Soiling. ARIZONA STATE UNIVERSITY. Retrieved from

Mejia, F., & Kleissl, J. (n.d.). Soiling Losses for Solar Photovoltaic Systems in California. University of California. Retrieved from

Sulaiman, S. A., Hussain, H. H., Siti, N., Leh, H. N., & Razali, M. S. I. (2011). Effects of Dust on the Performance of PV Panels. World Academy of Science, Engineering and Technology, 58, 588–593. Retrieved from

Denver, J., Miller, J. T. A., Manager, P., Jackson, J., Engineer, S. D., Gupta, V., … Hoffner, J. (2009). Impact of Soiling and Pollution on PV Generation Performance Performance Loss Due to Pollution (pp. 1–5). Retrieved from