Feb 2, 2018: Waste-to-Energy Systems

The Last Word on Tile Roofs

This week I was sent some interesting articles about both industrial and domestic-scale waste-to-energy systems. These outline some very promising developments in the technology needed to convert wastes into usable forms of energy. I’ll get to those in a minute. Firstly I’d like to round out the discussion we’ve had over the last couple of weeks about how inappropriate tile roofs are for Australia climates. In our last three Newsletters (here, here and here) I’ve been banging on about how tile roofs (especially the dark-coloured ones that you see in every new subdivision these days) are a stupid idea in Australia. The truth is they don’t make much sense anywhere unless clay is the only building material you have on hand. But here in Oz, where we have very hot summers and ready access to lots of better materials (like light-coloured Colorbond), a dark-coloured tile roof is completely insane. Anyway, I promise I’ll move on to other subjects but I would just like to share with you an email I received last week from a regular reader named David, which confirms, from first-hand experience, everything I’ve been saying. (This was written in response to last week’s Newsletter entitled ‘Should I Replace My Tile Roof’)

Interesting topic- we have done both, ie: repaint, and reroof.
When we bought our 1974 built house in 1995 in Brisbane, it had a very dark brown tiled roof, and just some ceiling batts. We had it painted with an off white (very light green) heat resistant roof paint in 1996.
The difference was absolutely enormous.
Then by 2012, the light green paint was all flaking off, mostly because the people who applied the coating did a lousy job in preparation. That’s what I was told by experts I called in to look at the problem.  It meant that another repaint would be difficult or impossible owing to flaking paint.
We decided to “bite the bullet” and go with a new “surfmist” (white) colorbond roof plus “anticon” blanket. We also had to have an engineer look at it closely as tie downs on the roof framing were non existent, just a few skew nails, relying on the weight of the tiles to keep the roof on in a blow. (Tieing the whole thing down properly cost approximately another $1500.)
All up the cost was about $30k, not bad considering it’s a very large house. Literally NOTHING beats a white colorbond roof. 
Dark roofs are the dumbest thing anyone could ever consider in our climate. Even with extreme insulation, all that heat goes into the environment, a heat island effect.
Anyway, the transformation was amazing, and the house is sooo much cooler now, and also even much cooler than after the original roof was repainted. We rarely need to use the aircon now even with our Brisbane summer, and when we do, it’s only one small super efficient 2.5 kW unit, used mainly to dehumidify, which draws around 520w max from our 5kW solar system. (6.5kW of panels, 5kW inventer.)
Even with charging our PHEV daily, we export far more power than we consume.
I shudder when I see many of today’s brick boxes, with little or no eaves, and black or dark coloured roof. Total madness! (One of our neighbours has a jet black roof, and the others are all pretty dark.)  There are so many people who just don’t understand even the most basic Physics, (which it just so happens was always my favourite subject at school.)
Today in Brisbane has been a real summer stinker, we reached about 34C here, but we have taken it easy most of the day in our living area with the house well closed up, with just the 2.5 kW Panasonic inverter A/C running. It’s about 27C inside, yet low humidity and extremely comfortable, and meanwhile we have been exporting 4-4.5 kW for most of the day, and even now at 3:30pm we are still exporting 3.85 kW. The aircon is running, but not working hard at all, and probably using 200-300w at the absolute most. (I have a clamp meter on the switchboard so can always keep an eye on things.)
We have also some shade cloth and small trees strategically planted to keep sun off the western walls. We can’t do anything about the lack of wall insulation in our 1970’s house, but were I building from new it would be done PROPERLY with extremely good insulation etc. as you alluded in your newsletter.
P.S. How’s your PHEV going. Both my wife and I absolutely love ours, (it’s white) but will hopefully pass it on to one of our kids when we (hopefully) get a Tesla Model 3 some time next year…. I’ve had my deposit down for a long time. (We actually like the PHEV so much, that if it had more battery range, say another 50klms, I wouldn’t even consider bothering with a Tesla. )
This is clearly a man after my own heart… he even has a PHEV like ours… and his comments about light and dark roofs are right on the money. I’ll leave it at that except to say I’ve received two quotes so far for replacing the tile roof on the house next to the Greeny Flat with ‘Shale Grey’ Colorbond and ‘anticon’ blanket. It looks like it will cost around $20k. I’ll keep you posted.

Waste-To-Energy Systems

As I mentioned at the start, I’ve been sent a number of articles this week about waste-to-energy systems. What we do with our food waste and other organic solids is a subject that people don’t always want to talk about but it’s very important. Our poo and our kitchen scraps have the potential to generate a LOT of methane. If this is just allowed to escape into the atmosphere it is a very potent greenhouse gas (about nine times worse than CO2). But if we capture it we have a renewable energy source. And while it’s true that when we burn it we get CO2, it is still much better than either letting methane escape or burning fossil fuels.

Generating Biogas can be done on a domestic or an industrial scale and, if you’re interested, here are some articles to read.

This article from The Conversation talks about the Home Biogas system described in the video above. It is currently available in Australia for about $1000. My brother is thinking about getting one and, if he does, I’ll be sure to let you know how well it works. For more information about the system you can visit the Home Biogas website here.

This article from New Atlas describes a larger system called NEWgenerator which can recover (N)utrients, (E)nergy and (W)ater from sewage. This system has been specifically designed for use in developing countries where clean water, energy and fertiliser can be in short supply and human waste can be a health and environmental disaster.

Finally this other New Atlas article is about the ‘World’s Largest Waste to Energy Plant’ which is due to be completed in Dubai in 2020. This huge power-plant will theoretically deal with 60% of Dubai’s garbage and produce enough energy to power 120,000 homes. I think we’d have to call that a win-win and I think there is a bright future for these kinds of technologies that can convert environmental problems into energy solutions.

A rendering of the Dubai waste-to-energy proposal (Source: New Atlas)

A rendering of the Dubai waste-to-energy proposal (Source: New Atlas)

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