Wednesday, December 16, 2015

hot, hot, hot...

Here in Adelaide, we're in the middle of our third 40C+ heatwave for the summer (which only technically started 17 days ago. I think a good case could be made for starting summer on October 15th in Adelaide). It has not been a hot spring overall, but we have had some very hot weather and have had very little rain. According to the BOM, Adelaide had only 15mm of rain in November (I would have guessed less!). October was hot and dry too, with an average maximum of 27 C (compared with a historical average of 21.3 C) and only 9 mm of rain.

Today, I went out in the garden at 3:30pm. It was 43 C, and we're in our 3rd day of a 5 day heatwave. Here are some photos I took.

2 year old walnut tree, showing dead burnt leaves from our last 40 C + heatwave. It will lose more leaves after today -- notice the wilting present on its leaves.
2.5 year old apple tree, showing burnt apples and wilting of leaves. I hope that, as the tree gets larger, it will shade more of its own apples and reduce the burning.

tomato plants in a non-wicking bed. They are very stunted, with lots of wilting and burnt leaves. We have been harvesting fruit, about 1 kg so far, but there's not that much fruit there. I think they need more water than I've been giving them (about 2 times per week)

I showed these images partly to show the effects of Adelaide heat waves, but partly to contrast with the wicking bed photos below. Note that neither of the wicking beds have been watered for 5 days, and the average daily maximum has been about 38 C in that period.


The better (and older) wicking bed. There is a little bit of wilting on the zucchini, but remember -- it's nearly 43 C outside! As you can see, the plants are blooming.

This is one end of the newer (large) wicking bed, that leaks a bit. But it still is working, as can be seen from the very happy curcurbits and beetroot shown here.

The other end of the large wicking bed, showing more happy curcurbits (with no signs of wilting) and happy silverbeat.


So, the wicking beds are an absolute, resounding success. I had been thinking that we wouldn't want more, because giving tomatoes too much water leads to poorer fruit (because the plants don't grow such extensive roots). I now think that we definitely need a wicking bed for tomatoes, but that we'll just keep it drier than the other beds. I think eventually, all our annual vege beds will be wicking beds.

Grey water project

In a previous post, I described a grey-water system to process the washing machine water. This is a failed project. I used 25 mm poly pipe to send the water, and I knew that it would block. I assumed I would be able to just blast it through with high pressure water to clear it. Unfortunately this doesn't work. I don't know if this is because
  • the pressure isn't high enough
  • the blockage is too intransigent, or
  • the pipe is just too long (15 m)
or a combination, but it is just not working so I've abandoned it. For now, our washing machine water is just going down the drain.
What I plan to do instead, is dig up some weedy reeds we have near the fence (which is only about 3 m from the laundry), and pipe the washing machine water there, and plant some bananas there. I'll do this with 50 or 70 mm PVC. Anyway, we'll see...

Secondary glazing

This is a success, and the house has performed well in the hot weather. We've run the reverse cycle A/C split system (a 2 kW system, so not particularly large), to try and keep the living area cooler while our solar PV is producing, and the temperature in our bedroom has stayed below 30C, which is quite bearable with the ceiling fan on low. Having the washers around the screws means that the acrylic sheeting stays sealed around the sides of the window.


Friday, December 4, 2015

Secondary glazing

My house has lots of windows. Windows are very poor insulators, and my windows let a lot of heat out of the house in winter and a lot of heat into the house in summer. Improving windows' thermal performance is very worthwhile if these things are already done:
  • drafts reduced/eliminated
  • Summer sun is excluded from the house (no direct sun on the windows in summer)
  • roof insulation is improved
I've done work on all these. The drafts project is not complete, but I've gone around 2/3 of the house with gapfiller, and have closed all the internal air vents. We've put external blinds on all the East-, West- and North-facing windows (though most of them were there when we moved in) and I've put a lot of insulation in the roof (not a fun job, but a very worthwhile one).

Secondary glazing is a cheap retrofit to get some of the benefits of double glazing. It doesn't insulate as well as double glazing, but it's a lot better than single glazing. The basic principle is that a second pane of glass is installed close to the first. It needs to be about 10 - 20 mm away. Too close, and heat transfer is too great (the air barrier isn't wide enough), too wide and an air current is established within the window and heat is transferred by convection.

For my house, I ordered acrylic sheeting which was cut to size. It was about $1100 for about 23 windows. I had an idea to attach it using double sided sticky tape so that it would look neater (than having screws in the corners). This seemed to work well, and I put some desiccant into the window to absorb moisture and prevent condensation. They looked great and I was very happy with them. Very schmick, so I kept going and did more windows.

Problem 1

What I found was that all the desiccant absorbed water (perhaps from the dobule-sided tape itself, though I'm not sure) and the desiccant turned to drops of sticky crap within the window. To cut a long story short, I don't recommend that people attach secondary glazing with double-sided tape. It may be that if I had done it on a cold winter's day and foregone the desiccant that condensation would not have been a problem. However, it will be very difficult to remove the glazing if there are problems down the track.

Hence, I've put all the rest on with small screws, one in each corner. This still looks good, and performs well.

Problem 2

We have sliding sashes in our windows, and the way they work means that the secondary glazing on the upper window needs to go on the outside so that it doesn't interfere with the opening of the window. This raises another problem. The acrylic is now exposed to the hot outside air, which causes it to expand more than the indoor sheeting (acrylic expands much more than glass as it heats -- up to 5 mm per meter of length). Because the corners are fixed in place, this is causing the sheeting to bow out in the middle (which means there are air gaps down the sides of the sheeting. To improve this, I plan to drill larger holes in the acrylic, and use rubber washers underneath the screws so that the acrylic can move relative to the screws, and hopefully avoid bowing. I will post about the success (or otherwise) of this plan.

Potential problem 3

The other potential issue with having the secondary glazing outside is that it is exposed to the elements. It is fairly UV stable, but will lose clarity in time if in direct sun (I'm being careful to keep it out of the sun). Also, I'm a little concerned about rain ingress into the glazing. I'm unsure how best to prevent this, but plan to put a bead of silicon along the top of the acrylic on the outside and see if that is enough (all the glass is under eaves so shouldn't get much direct rain on it).

What's left?

We have two enormous windows (1500 W x 1800 H) which it is possible to secondary glaze. I'd need to use 10 mm acrylic (vs 6 mm for the smaller windows) which would be extremely heavy and unwieldy and expensive (the two windows would cost nearly as much as the rest of the house). For this reason, I'm getting a quote to replace the existing glazing with a double-glazed plane. This is possible because the existing frame is nearly 100 mm wide and there is plenty of room. This will perform better than the secondary glazing, but it is not feasible to replace the glazing in all our sashes without replacing the sashes themselves (prohibitively expensive).

Performance

Our house definitely has better thermal performance than last summer. We've had a few days up around 40 already this summer, and the house has stayed about 26. This weekend, we'll have two consecutive days at about 40, it will be interesting to see how it goes. It's about 23 inside right now.
Note also, that our secondary glazing does not have the benefit of low-e glass, which is reflective to infra-red frequencies and helps prevent heat transfer. If we buy double glazing for the large windows, we will definitely get this (our's are South facing. For windows benefiting from winter sun, you may want to avoid low-e glass).

Cheaper options

Instead of installing secondary glazing, it would be much cheaper to make and install kume blinds, which provide possibly better insulation (at the cost of light and the view). We decided to improve the glazing.

Thursday, November 26, 2015

Wicking beds

It's been a while between blog posts, particularly those concerning house projects. I have a lot to catch up on, and I've now finished one of my employment contracts and so should hopefully have a bit more time to blog. There are a few things I want to write about:
  1. wicking beds successes and failures (below)
  2. acrylic secondary glazing and some of the learnings there. Not all is resolved, but is getting there
  3. failed project: Washing machine drain to front yard (pipe blocks)
I won't write about all these here, I will just focus on the wicking beds, but I hope to get to the others in coming weeks.

Gardening Australia (the only TV program I've watched for the past 6 years -- about an episode per year) has a great website about wicking beds. Basically, they cause the garden bed to be watered from below, by the process of the water wicking upwards through the soil. This means that the driest soil is right at the surface which minimises evaporative losses. In our ongoing attempts to reduce our water use, we wanted to build some so that we didn't need to water so much.

So far, I've built two using different materials, but both employ the same principles.
We built a round one first, using some salvaged corrogated iron, with help from permacultureSA.  I cut it so that the corrogations are vertical, and then pop riveted it into a circle (diameter ~ 2 m). The top was sharp, so I put a piece of hose all the way around held on with cable ties through holes I drilled into the corro. Underneath, I removed all the soil/mulch down to the clay, and made the bottom smooth. I made the inside walls of the bed as smooth as I could. Into this went builders' plastic (orange). This holds the water. I put two layers, but if I did it again I'd put 4 layers -- it is essential that it doesn't leak. There is an overflow pipe about 1/2 way up the walls, which are 400 mm high.
Into the builders' plastic, I put upside-down polystyrene broccoli boxes (these can easily be got for free, since they are not allowed to be reused), cut to a height of about 200 mm. I drilled holes in their bottoms and cut wedges from the tops to allow water to easily move through them. I also put a length of PVC pipe across the bottom, bending up and poking out the top. On top of this I lay geotextile, allowing it to form pockets all the way to the bottom of the reservoir in places. Then I filled the top with soil, being careful not to let soil get below the geotextile. First time around, all of the filling steps were done by the permacultureSA working bee -- unfortunately, we used poor plastic and it leaked and had to be taken apart and made again with better plastic :-(. Not good.

 I built a second bed using exactly the same method, but larger. This one is 4 m by 2 m. The sides of this are made of some old timber I had lying around, and it doesn't actually go all the way to the clay -- I let the deep mulch around the bed hold in the builders' plastic. This one leaks a bit, so I can't fill it much with water. It could be that the mulch has punctured it, but I think the plastic had a few holes (it was kicking around in my dad's shed for years and has been moved back and forth) -- also I only used two layers again -- silly! Use at least 4 if you do this -- moving all the soil is hard work!
(There are some volunteer tomato plants in this bed that need to be moved ;-)

Results

The beds seem to work pretty well, and hardly use any water. We're putting all our water-loving plants in there (not tomatoes!)

Learnings

  1. You really don't want leaks in the reservoir. Make sure the base (in particular) and the sides are smooth to avoid punctures, and that the plastic doesn't have holes. Use the thickest builders plastic, not the thin stuff you get at B------.
  2. It's really important that the base of the reservoir, and the bed above it, is level. Use a spirit level for this
  3. Don't shove a garden fork or stakes into these beds once they're done ;-)
  4. Don't walk on them
  5. I'd like to think that, when I build the next one, it'll have a concrete slab at the bottom and rendered brick walls, but I'll probably just hack it again...
  6. The beds take a long time to fill, particuarly gravity fed. Always use a timer otherwise you will forget which defeats the purpose of the beds (saving water).
I think they're great and we will use them henceforth.



Monday, October 12, 2015

Income equality

I have had many interesting discussions recently about income equality between the sexes. This post is an attempt to organise some thoughts.

Australia has a gender pay gap of nearly 18%, and women are very underrepresented in leadership positions. To start with, this is clearly unfair, unjustifiable and to the detriment of our species (numerous studies have shown that diverse teams make better decisions -- I'll leave the research to you if you are interested).

My idea (which I now find to be written about already -- see below) is that income nonlinearity contributes to the gender pay gap. I outline the idea here:

In Australia, at modest income levels, incomes rise in (approximate) proportion to the experience and responsibility of the employee. However, at higher levels this breaks down -- the trend becomes nonlinear and incomes rise exponentially with experience/responsiblity. The graph looks something like this:




In households where both a man and woman work (clearly not all households are structured like this but many are) there is a simple pressure to focus on one person's career because of the exponential rewards for seniority. Couple this with society's chauvanism (women need to challenge stereotypes to attain seniority in the workplace) and the fact that if the couple wants children the woman must take some time off, it makes sense for couples to in general focus on the man's career.

Note here that I am trying to understand what is happening in Australia now, not to argue that this is a good or just outcome.

This idea is described in detail in A Grand Gender Convergence: Its Last Chapter, by Claudia Goldin, who writes:
Whenever an employee does not have a perfect substitute nonlinearities can arise. When there are perfect substitutes for particular work- ers and zero transactions costs, there is never a premium in earnings with respect to the number or the timing of hours. If there were perfect substitutes earnings would be linear with respect to hours. But if there are transactions costs that render workers imperfect substitutes for each other, there will be penalties from low hours depend- ing on the value to the firm.

What to do?

If you think, as I do, that something needs to be done about gender inequality then what needs to be done? I think a good start would therefore be to reduce income inequality at all levels: reign in top incomes to be more proportional to experience/responsibility -- ie. return the exponential income increases to a more linear progression.

This will have the added benefit of a more egalitarian society in general.




Friday, October 9, 2015

The relative cost of things

My idea regarding ideas for public transport has resulted in conversations about the problem of smart phones. This post is not a defense of smart-phones -- I see them as a decidedly mixed-blessing (perhaps one day we'll be wise enough to get their benefits with fewer social costs). I wanted to briefly talk about our (me included) inability to estimate the cost of things.

In a previous post, I wrote about a new battery I installed on my ebike. I was shocked to learn that it is estimated to take 500 kWh to build a 1 kWh Lithium-ion battery. This is a lot.

Similarly, many environmentalists object to smartphones and other computer technology because of the environmental cost. A large part of this, though certainly not all, is the embodied energy contained in the device (much of which is sourced from fossil fuels). For a smart phone, this is estimated to be about 280 kWh.

This is also a lot of energy.

However, consider that 1 liter of petrol contains about 10 kWh of energy. That makes the lithium battery equivalent to about 50 L of petrol (or one tank of fuel in a car) and the phone equivalent to about 1/2 a tank of fuel. That doesn't sound like so much, and is largely because we don't think about the ludicrous amount of energy that petrol contains and cars consume.

I see this as a problem with the way we compare energy use. High tech gizmos seem like they use a lot of energy to make, but the good old-fashioned internal-combustion-engine uses orders of magnitudes more. In my opinion, a smart phone that allows someone to efficiently use public transport and avoid car transport (without requiring a large-scale re-organisation of suburbia) would be an excellent use of resources, and would hugely decrease our reliance on motorised transport.

With Europe as an example, it is clearly possible to have an excellent public transport system without a fancy mobile phone based setup. However Europe also has population density that Australia
lacks. For Australia to provide public transport service equivalent to Europe's (given our sprawling cities) would be expensive (it either requires replacing housing stock with higher density dwellings, or having lots of public transport routes). Using an idea along the lines of my dynamic route generation plan could let us service our cities more cheaply (in terms of energy and money!).

Some may argue that such a proposal requires a lot more than just a smart phone. Of course, that is true -- a setup like the smartphone network and google maps requires broadcast towers, routers, repeater stations, network infrastructure, GPS satellites, computer server farms, etc. All this infrastructure already exists. It is being used, right now, by many applications. From an environmental viewpoint, it is a sunk cost: the environmental damage is done, I think we may as well get what good we can from it.

Tuesday, September 29, 2015

Public transport in the age of the smartphone

Summary

Now that most people have smartphones, why do we need fixed timetables for public transport?

Detail

My wife and I visited Sydney a while ago. We haven't spent much time there and don't know the way around well. To navigate, we used Google Maps and selected public transport as our method. It is quite amazing -- Google is able to tell us where to walk, which bus/train/tram stop to wait at and it  even designs connections allowing time to walk between them. In my experience (and I now use it exclusively when planning a journey via public transport) its performance has been flawless.

It got me thinking -- 85% of Australian adults now own a Smart Phone. If we reach a situation where people can be relied on to have a smart phone, how can we take advantage of this to (re)design public transport?

Imagine

It's 2017, and you want to go somewhere by public transit. You use your smartphone to plan where and when you want to go (whether it is now or in 30 minutes' time). The app lodges the journey request with the local public transport authority (PTA), where there is a computer that dynamically generates the routes and timetables to minimise waiting times and maximise the directness of routes. The transport fleet is different -- there are still many large buses/trains/etc but in addition there are now a local fleet of small mini-buses (say 8 - 12 seats) that facilitate relatively local movements or act as feeders to the larger/faster routes.
The novelty of this idea is that the routes and timetables are dynamically generated -- there are no fixed routes or timetables -- these are designed on-the-fly in response to demand. There are New Years eve fireworks in Sydney and 1.5 million people want to go home at 1am? No problem -- feeder shuttle buses take people to the trains and larger buses take people to places where rail service is poor. Because the route planning is centralised, it can even avoid bus-jams (traffic jams comprised almost entirely of buses) by rerouting accordingly.

From the users' perspective, the service would operate similar to using Google Maps to plan a journey.
From the drivers' perspective, it would be like using a GPS navigator that tells them where to go and whom to collect/deposit.

Why?

Public transport is hugely under-utilised -- many buses/trains are well below capacity. Yet one often needs to wait for service. A system such as this would be much cheaper to roll-out than additional vehicles, and would result in a leaner service that was much more agile and efficient.

How is this different to Uber?

(disclaimer: I've never actually used Uber)
There are a few ways I can see
  1. It is designed with systemic efficiency in mind. Because the drivers are employees and can be relied on to work particular times, the central planner organises them collectively to move people. This will achieve much greater performance than a system where individual drivers compete for individual passengers. This point can't be overstated -- as a hybrid system, performance would be excellent.
  2. It's publically owned/operated. I would envisage that this is state-subsidised. Also, because journeys are shared (just like a bus/train), trips would be very cheap compared with a taxi service.
  3. It still uses connections to maximise efficiency. Of course, because connections are planned, you would never miss one. For example, your shuttle bus deposits you at the train station, the train waits until people have boarded and then departs. There is no timetable.

Problems?

 There are two (related) problems that I can see
  1. 15% of Australians lack a smart phone [1]. A service such as this would exclude non-smartphone users. I think a government subsidy to give all low-income people a smartphone would still give savings in public transport alone if this were implemented.
  2. Technology barrier. Old people and people with sensory or cognitive impairment could tend to be excluded. This would need to be carefully managed to ensure access.

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[1] This number is changing rapidly. This article states that 30% of Australians who lack a smart phone are planning to buy one in the next 12 months. If that eventuates, by 2017 only about 7% of Australian adults would lack a smartphone.

Saturday, September 19, 2015

Vasectomy

this post contains comments and judgements about medical practice and attitudes. Although I'm fairly knowledgeable about such things, I am not a medical doctor, surgeon or allied practitioner. Please consider this post as opinion only and not as a basis for medical decisions

I've got two kids, and it's enough. My wife and I decided that I'd get a vasectomy to be sure (well, fairly sure) not to have any more.

I had a vasectomy on Friday September 14th. The actual procedure seemed very simple and quick, and I was home that afternoon. I had a very quiet weekend, just relaxing on the couch, I followed the advice of my urologist to apply ice and take neurofen. He had previously told me that Monday "might be the worst day", so I  wasn't too concerned as the pain become more acute throughout the weekend. By Tuesday I could hardly stand up, and the pain was so acute that, even lying down, I couldn't tell when I needed to urinate because of the constant pain and discomfort.

My scrotum was approximately double its normal size.

At this point I phoned the urologist's surgery to get some advice, but was told that he was on a week's holiday and that his colleague (also a urologist) was also on holiday. There was no post-operative support (!)

When nothing had improved by Wednesday, I went to my GP, who thought I might have an infection, so put me on antibiotics. This did seem to help, and by Thursday the pain had reduced to the point where I could walk, but was still extremely uncomfortable (it felt like I had an extra pair of testicles).
I saw the urologist the next Monday (when he returned from his holiday) and he was quite concerned, diagnosing a hematoma (bleeding from the operation), and advised that I continue taking the antibiotics.

It's now 5 weeks after the procedure, and things have mostly settled. I can ride my bike again, though I still regularly get pain, especially at the end of the day.

Thoughts

I think that we take vasectomy too lightly. It's a surgical procedure, and thus vulnerable to all the complications that other surgical procedures can cause. In my case, my scrotum wasn't shaved before incision (I would expect that would increase the risk of infection).
As an example of people's attitudes, I heard a story about a guy who cycled home from his vasectomy (ie. it's such a trivial thing), and had a couple of veiled comments along the lines of "toughen up and stop whinging".
But, speaking with other men, I have heard many stories of problems. One guy I spoke to said he still gets pain from his two years after the procedure. Another guy had an infection that required hospitalisation.

Conclusion

Vasectomy is a very minor operation. It is routine and is usually successful. Despite my experience, I would recommend it. But -- do not take it lightly, do not attempt to be tough, and do not ignore symptoms afterwards -- if you have significant swelling or pain, see someone straight away.
Also, remember that the experience of surgery is hugely varied -- just because your brother has a vasectomy and jogs home does not mean that will happen for you.

Friday, July 17, 2015

el nino

The bureau of meteorology says that we are in an el nino. This would explain the dry winter we are having so far.

As I said in planning for water scarcity, Winter is the time to prepare for summer*. Our rainwater tanks are now completely full. That is 37000 litres of water we have stored, and it is comforting to reflect on that as we head into a summer that may well involve water rationing (Adelaide's reservoirs are at 50% capacity).

Kitchen waste water

Last Summer we bucketed out kitchen water onto the garden, using it to water trees. I feel that this is not sustainable -- the bucket is heavy and awkward, and the risk of indoor spillage is worth considering. We visited some near by friends recently, Ash and Annie, who have set up a worm farm outside their kitchen window, into which their kitchen waste water drains. From the worm farm, the water drains to an underground sump from which a small solar powered pump drives the water around their garden.

It's a great setup and inspired us to do something similar, but we wanted to try something a bit simpler (whether ours works long-term without blocking remains to be seen). My parents were able to get me a 200 L plastic barrel. I turned it on its side, and cut a square lid. We put some broken concrete in the bottom, covered it with geo-textile and covered the textile with compost and food scraps, before introducing the worms. I then cut a hole in the bottom and installed a hose plug, to which I've connected a hose that drains to citrus trees in the front garden. I expect that this hose will block up, and will need to be periodically "blasted through" with high pressure water.

Here is a diagram of the setup
Diagram of barrel. The barrel is on an angle (that was just the easiest way to get it to the optimum height), masonry inside it, geo-textile [soil barrier] on top of the masonry, worm bedding on top. The 50mm PVC pipe is shown, with small holes in the bottom to distribute the water inside the barrel. I added the tap at the front so that we can use worm tea when we want (worm tea on tap! ;-)

This has been running for about 3 - 4 weeks now -- the worms are not yet established, but it seems to be working so far. I think it has about 20 L per day going through it. The water that comes out is quite rich, and I'm hopeful it will make for some very happy trees!

Getting the PVC pipe from the sink to the barrel was very straight-forward. We have an S-trap under the sink. It has a rubber seal on the back, and the pipe that came out of that went through our outside wall, 90-degree bend and straight into the sewer. I cut that pipe near the ground, and was able to twist the whole thing sideways to point towards the barrel (the pipe swiveled within the rubber seal). Then I used some plumbers' glue to extend the pipe, and put another 90-degree bend in it directing it into the barrel.
The waste-water worm farm. The pipe is visible exiting from the kitchen on the right. Below that, the waste to the sewer is visible (blue arrow) where I cut it off and bent it around (the original path of the waste pipe is shown by the red line). Also visible is the (grey) join that I used to extend it (red arrow)



Mulching

I managed to get the biggest free load of mulch ever. It was about 10 cubic meters, and I've been steadily moving it onto the front garden and the path. I now have lots of mulch in the front garden -- more than 40 cm deep in places. Need to be a bit careful here, as it takes quite a bit of rain to penetrate the mulch and get to the soil where the roots can access it. Also, mulch can deplete the soil of nitrogen as it decomposes. Immediately around all the trees, there is also lots of compost, which will hopefully provide sufficient nitrogen. Also, when I water the trees in summer, I usually give them at least 10L each so that will soak down into the soil. Such think mulch will help keep the roots cool and moist in summer.

Toilet

Along with the washing machine and kitchen sink, the toilet uses a lot of water. I've been experimenting with a bucket composting loo that I empty into a wheely bin in the backyard. This saves water and retains the nutrients for the garden. I'm the only person in our house currently using this, but if we all exclusively used it it would save about 30 - 50 L freshwater per day. My plan is to build a bucket composting toilet from plywood.
(By the way, I mix carbon-rich things in to the bucket such as cardboard and mulch. It doesn't smell at all)

Wood heater

We've had quite a bit of cold weather recently -- I finally replaced the glass in our combustion heater (it was missing when we moved into the house two years ago) and it has been fantastic. We don't need to burn a lot of wood with it, but it makes a big difference! I think it's original to the house (about 60 years old) -- it's really in very good condition.

Conclusion

I'm not really sure how to conclude this, since it's a work in progress. I've recently started another job, so am busier and fewer projects are happening, but I hope to keep turning things over. I've ordered a heap of acrylic sheeting to add secondary glazing to most of our windows -- I will blog about this as I do it.

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* This is a general truth I believe. For most natural resources (energy included) there are times of abundance, and times of scarcity. Use the times of abundance to prepare for the times of scarcity.

Thursday, July 2, 2015

Peak oil, debunked

For years, I've been trying to find a sensible debunking of peak oil. Clearly, the reality that oil production will, at some stage, peak is incontrovertible. The debunking I was seeking concerned the nature of EROEI and renewables, and whether it would be possible to successfully transition from a fossil-fuel society to a renewable society in the sort of time frames that remain to us.

There are many peak-oil writers who contend that this is not possible and that because of this, industrial society will disappear over the next few centuries. I wanted to find an opinion that countered this (I like to read all sides of a debate).

Finally, I've found one: Bountiful Energy

This is a sensible, well-written blog that attempts to systematically dismantle the idea that industrial civilisation is failing because of peak oil. But, is it right?
(I encourage you to read it yourself, but here are some of my thoughts)

The good

The blog makes some new observations that I'd not previously seen in the peak oil debate:
  1. EROEI for oil in transport is a lot lower than reported because of the poor efficiency of the internal combustion engine. The author estimates EROEI of about 4 for fossil-fueled transport. This is a pretty low bar for renewables to clear!
  2. The author also develops the idea of cost of net energy, which is the cost of the energy gain from a process. He contends this to be more useful a metric than EROEI. I'm inclined to agree.
  3. The author observes that a lot of the embodied energy we see can be recycled. For example, a lot of the embodied energy in solar PV installations is used to manufacture the aluminium racking. This is almost completely recoverable at the end of life, and so that should be considered when assessing the EROEI for solar PV. This will make the EROEI of PV better.

The bad

The biggest problem I have with the blog, is that he appears to believe (I am discussing this with him) that pollution and environmental catastrophes will not affect industrial civilisation. My feeling is that it is impossible to separate peak oil from the effects of pollution since the extraction of more marginal fossil fuels (one can't call tar sands "oil" in any meaningful sense) is inherently more polluting (per unit of net energy) than conventional oil plays. In other words, the negative effects of peak oil could manifest as environmental degradation rather than high/low prices, etc. (quoted from a comment I left on his blog, to which he has not yet responded).

Conclusion

I will keep reading and thinking about his blog. My feeling for now is that it helps clarify for me the way industrial society is likely to follow the trajectory of limits to growth. For example, taking his blog at face-value, I could see industrial civilisation making a significant transition to renewables this century, but still failing to contain pollution which will drive down quality of life. This could also be seen to tie in with David Holmgren's brown tech scenario.

In a nutshell, the author of Bountiful Energy is bringing interesting new arguments and insights, but I am not yet convinced that the future will be business-as-usual.

Tuesday, June 23, 2015

Overreach

Hubris in chess leads to overly aggressive moves that expose pieces to insufficiently protected positions. The result is regularly a fatal counter-attack after the foray fails [p80, Depth of Field: Stanley Kubrick, Film, and the Uses of History]

Overreach occurs when a person becomes overextended and often ends up forfeiting position. It is possible that, had Napoleon not invaded Russia he could have consolidated Europe into a French empire. Instead, the French army could not maintain its supply lines and was defeated. This lead to the conquest of France and Napoleon's exile.

This is a general concept, and is not limited to chess or war. Consider the global financial crisis (2008). There were many anecdotes about people who had overextended themselves financially and lost their homes when they could no longer earn the money they had previously. It is sobering to think that in some cases, after 20 years of earning good money, and person could lose their home because of relatively-short-term unemployment.

To my mind, this relates to sustainability. It shows us how difficult it is to be sustainable, and how easy to overreach and expose ourselves.

This can, of course, occur at every level:
  • the individual living beyond their means (even if it requires a sudden illness or job loss to become apparent)
  • A wealthy family whose margin loan is called because of declining stock values
  • A company that hires staff anticipating growth, but hires more staff than it can maintain
  • Suburban sprawl in a city necessitating roads and other infrastructure that the city can't afford to maintain
  • A country arranging its economy around increasing levels of service-based jobs, whilst outsourcing all manufacturing, requiring the importation of all manufactured goods.
Along these lines, it is my opinion that we, as a civilisation, are overreaching ourselves in the services that we think we can provide. As an example, it is considered normal for people to drive their private cars where they want, when they want -- spending a quite small proportion of their income to do so. The problem is, that the technology we have to make private motorised transport "happen" are unsustainable. It's abundantly clear that the internal combustion engine is unsustainable: it burns petrol, which will run out. Electric cars, powered by solar photovoltaics are a technically-sustainable means to provide motorised transport. The problem is that they are also unsustainable -- or at least, we can not sustainably produce them, in sufficient numbers, to replace our current vehicle fleet at a reasonable economic cost.

In other words: we do not have the technology to sustainably provide people with private motorised transport (whether such technology is feasible, even in theory, is to me an open question)

So here is an example of overshoot in our society: we have come to expect a service that we can not sustainably deliver ourselves. Not only do we expect it -- the functioning of our entire society is predicated on it! This is a problem -- the disruption caused when we lose our ability to afford cars will be significant. As things tighten, the resources we waste on unsustainable transport are resources we won't have to build sustainable transport -- the end result being we end up with a much lower standard of transport than if we had accepted compromises earlier.

Wednesday, June 17, 2015

Planning for water scarcity

It is winter, the rainwater tanks are about 80% full, and I'm planning for summer. I know that, for our water to last through summer, we need to gather every drop possible, and then conserve it throughout the dry months. It can be dry from November to May some years, and when this is combined with hot weather, lack of water can be difficult. Wikipedia puts it well: "Nine of Adelaide's ten warmest years ever recorded have occurred in the last decade: from 2002 to 2014. Summer 2013-14 was the hottest summer on record, with a record number of 13 days exceeding 40 °C (104 °F), while Autumn 2014 was the warmest autumn ever recorded in Adelaide's history.[48 The following summer, in January 2015, bushfires burned out of control after days of extreme heat conditions in Sampson Flat, South Australia which then spread towards the outer northern suburbs of Adelaide, toward Greenwith and Golden Grove.[49] The heatwave and fires caused widespread destruction, health problems and fatalities. The number of heat-related deaths in Adelaide is expected to more than double by 2030."
In other words, summers are hot and dry, they are getting hotter and drier, and this trend will continue.

I've written other articles about our water collection and storage:
Rainwater modelling (assess sufficiency of storage against historical meteorological data for Adelaide)
Water at my house: rainwater
Progress report on water systems

Grey water

Last summer I caught our washing machine water in a wheelie bin and bucketed it onto the garden to reduce the watering load. That's a lot of work, and I don't think it's sustainable (for my body!) -- I get plenty of exercise, and don't need more. I wanted to set up a greywater system to save me work.

There are some good online resources about greywater systems:
Art Ludwig has fabulous diy info for greywater on his website. I spent quite a bit of time reading his site, and have understood that:
  • pumps are to be avoided
  • use gravity to get the water where it's wanted
  • keep the system simple
The basic principle is that the washing machine puts the water into a white bucket, from which it drains through a black pipe, to our front yard. That pipe finished underground (about 200 mm  deep) within an upside-down plastic plant pot with holes drilled in the sides. That water then falls on the ground there, and the whole thing is covered in mulch.

The bucket. The washing machine outlet is visible behind (grey corrogated pipe), and the exiting black pipe goes to the front yard. This bucket exists to protect the washing machine pump -- if it was connected directly to the black pipe and there was a blockage, it could burn out the pump. The white bucket has an overflow hole on the other side (below the grey water inlet). If the water is not draining, it will exit through that hole (to protect the pump)

The side of the house, showing the pipe. I have tried to make the pipe gently slope down right along the length of the house so that there are no "local minima" in the pipe (places for crud to accumulate and block the pipe). You can also see a heap of broken concrete. This is concrete that I've dug up elsewhere, but I don't want to put it in landfill, so am looking for another use for it -- maybe shoved down the sides of a hole to hold in a post...

Here's where it terminates in the front yard. I've put the bamboo on top, because I don't want someone walking on it and breaking it.
The idea is that there is a large mulch pit where the pipe terminates, so that the grey water can diffuse through the mulch and generally wet the area. Plants will get their roots into the mulch, but because the water falls from the pipe and there is an air gap, plants won't get their roots into the pipe and block it. (fingers crossed).
Instead of digging a circular bed, I've dug a spade-width trench over to a couple of other trees. I've filled this trench with mulch. Probably the trench is currently too small to accept all the grey water, so I'll need to dig some more -- other trees can then access the water which will be good. I've got two citrus and a white sapote near here, so the water will be appreciated.

I've used 1 inch pipe, which is narrower than recommended (from memory, Art Ludwig recommended 40 mm pipe), so I expect it will get blocked from time to time. My plan is to put the hose in at the white-bucket end, and just blast it through. I hope it works!

Salt build-up

This is always a concern with grey water. Adelaide town water is very salty, so we're ahead here (because we run on rainwater), but we use low-salt soap in the washing machine, and we use it very sparingly.

The front garden

I thought I'd include a few photos of the front garden. We've been here about 18 months and the entire garden was couch grass when we moved in. All the grass is now gone, and there is an average of 150 mm of mulch across the yard with about 12 trees planted.

Mandarin -- this tree has been in the ground for ~21 months, and seems very happy

Almond tree -- this tree has grown amazingly (~21 months in the ground) -- we even had some almonds in April! You can also see the rainwater tank (top left). We had a few discussions about whether it was aesthetically ok to put a rainwater tank in the front yard. I've wrapped wire around the tank and we're growing a passionfruit vine up it. I see us as trailblazing a new garden aesthetic! ;-)

Orange tree -- has a few oranges on it (also in the ground for ~21 months)
I was a bit hesitant as to whether I should let the citrus trees fruit, but I decided to just let them. I guess it's possible they won't fruit next year (because of the stress). Time will tell...

There's lots more work to do here. I want to plant at least another 6 trees this winter. I'm thinking another lemon, and some more nut trees, an avocado (our last one died). Any other suggestions? Out the back we've got apples, pears, nectarines, peaches, plums, walnut, fig...

Wednesday, June 10, 2015

Environmentalists should live in the Real World

Many times, I have seen someone arguing for reduced ecological damage, a carbon tax, a transition to renewables, etc. A response I regularly see goes something like "environmentalists should get out in the REAL WORLD" or "this sounds nice in theory, but it won't work in the REAL WORLD" or "in the REAL WORLD, people don't have time for this"

I think the underlying thinking behind these blanket statements is that the human world of the economy, jobs and politics (referred to as the real world) places hard limits on what is possible for us to do as a society. For example, we can't transition to renewables because of the needs of industry for cheap power. People can't ride bicycles to work because they don't have time. A carbon tax is bad because it is a burden on the economy.

The interesting thing to me, is that this thinking is precisely backwards.

In actuality, all of our prosperity comes from natural systems:
  • food
  • water
  • fuel (including fossil fuels)
  • air
  • materials (eg. plant fibres, mineral ores, chemical feedstocks, animal skins)
The natural systems that provide these services to us are the real world.  Conversely, the worlds of
  • money 
  • economy 
  • finance 
  • politics
are actually completely dispensable. If you doubt this, reflect on the fact that for most of history (say until 5000 years ago) no human society had these things. Even today, some human societies lack one or more. Money, by itself, has no inherent value, meaning or worth -- it is merely a token of exchange. The only reason people see money as valuable is because it can be exchanged for goods and services (all of which eventually come from the natural systems that support us).

So, when someone says "this sounds nice in theory, but it won't work in the REAL WORLD", what they area really saying is "forget about the biophysics of our natural support systems, we must at all costs maintain our arbitrary system of exchange tokens -- that is what is really important"

When put this way, it sounds stupid. That is because it is stupid. It is like the Easter Islanders chopping down their last tree to put up another stone statue (so that they couldn't build more fishing boats and starved). In fact, the similarities are very troubling.

Sunday, May 31, 2015

Bikes for transport, electrified xtracycles

I've written about bikes before. I first introduced my xtracycle here, the ebike and associated thinking here, and talked about cycling with two kids here.

As I introduced last post, if we want to lessen the destruction we cause to the biosphere, it can be hard to identify where to best focus. Here is the priority list (as I see it):
  1. drive less or (preferably) not at all
  2. eat less industrially-produced meat, fish and dairy
  3. use less energy and buy GreenPower
  4. buy less stuff
In terms of reducing environmental damage, I think these are the Big Four. It's also great to buy organic, go to farmers' markets, do gardening, and play acoustic guitar (we try and do all these) but if you drive across town to pick up your organic veg in your Pajero, it's of questionable benefit (in my opinion). To my mind, this is similar to the (well-intentioned) person with a drawer full of washable nappies, and a disposable nappy on their child.
This is the reason I haven't written much about the garden. We put a fair bit of effort in, but it seems to me in many ways the less important part of what we are striving for -- though that could be seen as my prejudice as an engineer! I'd love to hear people's thoughts/criticisms of this idea. I do plan to write about it though.

We have a car (a small SUV in fact!), and are exploring how little we can drive it (it has been about a fortnight since we drove). I'm keen to see whether we can share a car with some like-minded people nearby but we're yet to organise that. A difficulty is that my youngest child is under 3, and so we have many years of car seats ahead of us.

In terms of thinking about efficiency, 1 L of petrol is equivalent to about 10 kWh. That is extraordinary, and shows just how much energy a car is using (and just how energy-dense petrol is). This is a big reason I love bicycles.

I recently made some changes to our bikes. The xtracycle was on a bike that was really too big for my wife and I hoped that putting it on a smaller bike would let her use it more effectively. Also, we sometimes took the kids places quite far away (or up a decent hill) that was hard to pull the trailer. I hoped that combining the xtracycle with the ebike would solve all these problems.

The xtracycle, now with electric assist front wheel and disc brakes.
I also took the opportunity to alter the platform on the back (using some found material) and bring the child seat forward. This greatly helps the dynamics of riding it, as the kids' weight is now in front of the rear axle. I've also mounted the battery for the ebike beneath the rear tray. I'm yet to finish installing a front rack on the bike.

Performance

The bike rides well. It carries a rider and two passengers (front passenger sits on platform and holds rear-facing handlebars, rear child sits in the plastic seat). It has a huge luggage capacity. It is fast, and can easily be ridden at 25 - 30 km/h on the flat when fully loaded. Handling is greatly improved with the children's weight further forward. Because the rear wheel is now 26" instead of 27", the weight is also marginally lower, which also improves handling. At some point, I might consider replacing the rear wheel with a strong 20" or 24" wheel.
In its previous  configuration (here) I carried a child and about 100 kg of luggage on it. It's quite amazing how much weight it can bear!

The problem is that it is still relatively hard to ride with a child in the rear seat, and my wife is still uncomfortable. It requires a lot of upper-body strength to balance -- particularly when the rider is getting on/off with two kids on the back. I do think a smaller rear wheel would help this, but we may consider a bakfiets (or similar dutch bike) instead. Not sure at this point. Also, our oldest child is nearly at the point where he could ride a tag-along (he can ride his own bike 5 kms, so could probably do 15 km on a tag-along).

Conclusion

We use this bike a lot. It's good for two kids, and great for cargo. Also, there have been many times that the ebike has allowed us to leave the car at home. I believe that, if electric vehicles are the future, it will be electric assisted bikes for most people -- electric cars will remain too expensive for most.

Monday, May 25, 2015

Eco-consumption

The problem that we are facing, as a species, can be summarised in one word: overconsumption.

Simply, we are using more than the Earth can sustainably provide and so are degrading its natural capital. It's like the young man who inherits $1million, only to be broke a few years later because he overspent -- he didn't spend only the return on his investment, he spent his capital. That is what we are doing.

The problem is that we are individually so disconnected from the fact that our goods and services are ultimately dependent on natural goods and services that we often don't know what we actually need to do to cause less damage.

Here is an example to clarify what I mean. I know people who want to do the right thing by the environment, so they have bought washable nappies for their baby. They were excited about this, and felt good about doing it (as they should). Here's the catch though: washable nappies are only good for the environment if their use displaces disposable nappies that would otherwise have been used.

Put this way, it is obvious, but this pattern runs deep and there are other, less obvious, examples. It is also made more confusing because marketing is a $500 Billion per year industry, and marketers have identified the environment as being a useful method to sell products.

Solar PV

In Australia, most people who buy solar PV panels for their house sell STCs (formerly RECs) [1]. Essentially, they are selling the "green" part of the energy that those panels will produce over their lifetime. Companies buy these credits, so that products can be packaged for sale.
You may say but I've still got the panels so my power is Green, right?, well, no. Consider the person who pays extra to buy GreenPower from the retailer. The retailer can call the power GreenPower, because they have bought sufficient STCs -- many of which have come from new PV installations.

Dishwasher

There is a widespread idea, encouraged by advertising, the dishwashers are Green because they use less water than hand-washing. Here's the catch: this assumes a perfectly full load in the dishwasher. Also, it doesn't include the energy-and-water that was used in the dishwashers manufacture, packaging, distribution, installation and disposal. The depth of the problem is well summarised here, although I don't agree with that article's conclusion. But, again, this is presented by advertisers as a settled debate: buy a dishwasher -- it's green!

Conclusion

Hopefully these examples help you identify this pattern in your own life, and be more resilient against the Evil Forces of Marketing. As a general rule, the best outcome for the biosphere (and for our collective future) is not to consume and not to buy.



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[1] for the record, I sold my STCs when I installed my system. I regret it now, and may buy them back at some point.

Monday, May 18, 2015

Winter warmth

I have got the rooftop solar space heater working. It's quite simple. This is what it looks like from the roof:
My north facing roof. From left, the mini-kitchen-solar-HWS, the solar space heater collector, the solar PV, the main solar HWS
It's not easy to see in this photo, but on the top right of the solar space heater collector, there is a 6" galvanised steel duct connected, which goes through the tile. I picked up the ducting cheaply from a car yard for $10 (I saw it from the train and made an offer). In the roof, I connected insulated, flexible ducting to the galv ducting and ran it to a pump (the pump draws about 55 W -- not much). From there, it is ducted to a 3-way splitter, and then to three outlets that I installed in the ceilings. They look like this:






Installing them was quite simple, although sawing through my ceiling was a bit intimidating! I used a cheap thermostat from ebay so that the pump only turns on when the air in the solar collector is warm enough. It is available here (It works fine, but I can't recommend it yet as I don't know how it will last). The thermostat is designed to keep a space at a certain temperature, which is the opposite of how I'm using it. I've put the thermometer in the rooftop solar collector, and anytime that collector rises above a certain temperature (23 C at the moment), it activates the pump [1].

The controller seems to work fine. Note that I also installed a 1-way flow valve (like this), so that warm air can't flow out the house through the solar heat collector at night time)

Performance and improvements

It's early days to judge yet, but I think it has raised the inside temperature of the house from about 15 C to about 17.5 C, which I'm pretty happy about. The weather hasn't changed much from before it was running, and we've had a mixture of gloomy and sunny days.
Improvements:
  1. Insulate the back of the collector. The collector loses a lot of radiant heat from the back. I need to insulate this, which will make the pumped air warmer.
  2. Experiment with collector air flow. I may try to make the air flow a two pass thing, either by double-glazing and running the air intake between the glazings or running the air behind the corrogated iron, to preheat it and make the insulation less important. 
  3. Pump speed. I think the pump has a higher speed setting, and I'll try that
  4. Insulate. I've still got more work to do insulating and draft-proofing the house. That will help
When winter sun is shining in Adelaide, it is about 1000 W per square meter. My collector is about 3 square meters, and I think I'm achieving at least 33% efficiency,  which makes my heater at least 1 kW when the sun is shining (it costs about 50 W to run). This gives a coefficient of performance of at least 20, making it at least 4 times more efficient than the best-performing reverse-cycle heater (and also a lot cheaper to install).

Conclusion

I think that, when finished, this will show it is possible in Adelaide to do a cheap retrofit (I will itemise this sometime) on a 1950s house with relatively poor thermal performance and keep internal winter temperatures above about 18 C.

Shower

I have also just put a "lid" on the shower using some of the left over plastic sheet from the solar heat collector. I built a simple wooden frame, and attached the plastic sheeting with some screws, and have just sat it on top of the shower screen. It makes the shower much warmer by trapping the warm air. The shower is more like a sauna, and so it feels warmer (because heat loss by evaporation from the skin occurs less in a warm humid shower). It also has the benefit that not so much steam goes into the bathroom -- we don't even need to run the exhaust fan now. This is really easy to do (about 30 mins work, with children helping), and is really worthwhile.

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[1] To work in this way, the thermostat is run in its cooling setting (where it switches on above a certain temperature). In summer, I will switch it to its heating setting, so that it only switches on below a certain temperature. Then I can tell it to pump air into the house, when it is below (for example) 24 degrees. This sounds confusing and backwards, but it works.

This article was written by Angus Wallace, and first appeared at guesstimatedapproximations.blogspot.com.au

Tuesday, May 12, 2015

What is the best tilt for solar PV?

We have a 2 kW solar PV system, and solar hot water. Our house is a net exporter of electricity (we don't use gas). This is by quite a margin: our average consumption is about 3 kWh/day and our average export is about 6.5 kWh/day.

Thus, we export more than double the power that we import from the grid.

However, at this time of year our import/export is about equal. We are using slightly more power than during the shoulder season (though we're yet to boost our solar hot water), but the production of our solar PV system has markedly decreased. There are two reasons for this:
  1. The angle of the sun is much lower at this time of year, resulting in lower irradiance to the panels
  2. Cloud cover
Clearly, there's nothing that can be done about cloud cover. But it is the sun's angle I want to talk about here.

PV tilt

There has been much discussion of the optimal tilt for PV panels. Back when there was a well-paying feed-in-tariff (FiT), people advocated installing the panels nearly flat. At Southern Australian latitudes, the annual production of clean panels is maximised when they are flat (note the word clean -- below ~10 degrees tilt, panels must be manually cleaned).

Now that there is no FiT, the equation has changed. For me, the FiT is less of a consideration -- my goal is to to live within my solar budget throughout the year. But why?

EDIT: It is worth mentioning that choosing the "best" tilt is important for all solar collectors: solar thermal, solar hot water, and solar PV. If anything, it is more important for solar thermal than solar PV, since solar PV collects diffuse light energy from the sky and not just the sun.

Your solar budget

Growing up in an age of cheap fossil fuels, we have been conditioned to the idea that gratification follows expectation. Want to heat your house to 35 C in the middle of winter? Sure. Want an outside spa in the snow? sure. This simply will not happen in the age of renewables. For a society powered on solar and wind, there will be times (sustained cloudy and calm periods) where power is significantly more expensive. By "significant", I imagine 10 times dearer or more.

This can be mitigated by installing battery storage, however batteries are expensive. To install sufficient storage to provide during prolonged periods of low production will be out of reach for many. I think in Australia a 3 kWh (usable) battery system would (currently) be affordable by the majority, and might cost $3000 including installation. Note that such a system would really only provide power for one day, and then only for the frugal.

This is a side issue, about which I will elaborate in another post, let's get back to the PV tilt.

It's all about winter production

If you want to live within your means, it is the winter production that is crucial. There is a solar bounty in summer, so there's no problem there. Therefore, we need to increase the tilt of the panels to increase winter PV production. Here comes some maths:

Let's imagine we have a solar panel that is directly facing the sun. We would say that its surface is normal or perpendicular to the sun. This maximises the production because it catches as much sun as is possible.
Now, let's imagine that we tilt the panel so that it is not directly facing the sun. Now it catches less sunlight (its shadow is smaller) and so it will produce less energy. If we keep turning it, eventually it will cast no shadow (it's sideways to the sun) and receive no direct sunlight [1] and produce little.

So, as we turn the panel from directly facing the sun, to being side-on to the sun, let's imagine a scaling factor that describes the production of the panel. This factor will be decreasing as we increase the angle away form the sun form 0 degrees (facing) to 90 degrees (side on). The curve that describes this is called the cosine curve.
The cosine curve, showing how production decreases as the PV panel is tilted away from direct sunlight. Remember, that this does not consider energy production from diffuse light (in practice a panel will still produce energy if oriented away form the sun, it will just produce a lot less). Note that for low angles (less than, say, 20 degrees) there is little effect on production, but by 40 degrees it is falling sharply. That is the characteristic of the cosine function.

Looking at the amount of power exported from my house since September 2014, this pattern is clearly visible as we approach winter.
These data start on December 20 2014 (summer solstice) and the decrease in production through Autumn 2015 is clear.

My panels are oriented at about 23 degrees, which means that at the winter solstice, my panels are oriented about 40 degrees from ideal, significantly effecting production.

Given that we have lots of available PV power in summer, I would happily sacrifice a little to gain extra winter production and I would do this by increasing the tilt of my panels. I think the optimum would be to increase their tilt to about 45 degrees, which would reduce the winter sun's angle to about 20 degrees and increase winter production (at the cost of some summer production).

Conclusion

Orienting PV panels to ensure optimal winter production is a strategy that will help maximise your self-consumption. This helps you get the most from your PV system during all seasons.

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[1] PV panels also produce energy from diffuse light form the sky, but it is a lot less than direct sunlight. Here, we consider only the direct sunlight.
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