Tuesday, April 28, 2015

Kitchen hot water

A while ago, I wrote about my reasons for wanting a dedicated hot water system for the kitchen. Today, the system is finally operational. It's a big day!

I decided I wanted to do all the plumbing myself, which has made things take a bit longer (I have no previous experience brazing or bending copper pipe), but it has gone reasonably smoothly (albeit slowly), and in the end I'm reasonably happy with the standard of work. I left the most visible parts until last, when I'd had most practice and they look reasonably professional.

Here is a picture of the little hot water system on the roof (with the unfinished space heater next to it). It holds 30L of water, and has 8 x 50cm evacuated tubes. It is a low pressure system, so I can't just connect it to mains pressure with a tap in the kitchen (as is the norm). This system cost me $300 on ebay. It came with the aluminium racking immediately underneath it, but all the rest of the aluminium on the roof I installed myself.

Because the unit can't run at mains pressure, I needed a system whereby the tap to it controls its supply (before that supply reaches the tank). Then the tank is just sitting there at atmospheric pressure. To do this, I used an electric solenoid valve, which cost about $20 on ebay, with a 12 V transformer that I installed in the roof. We had an existing powerpoint in the roof that is controlled by a switch in the kitchen. That switch now energises the solonoid valve, switching it from normally-closed to open and allowing more water to flow into the tank of the hot water system.
Because the tank is always basically full, this causes it to overflow. The overflowing water exits the tank via the (hard-to-see) pipe at the top-left in the first image, and that pipe leads straight down to a (tapless) faucet in the kitchen below. Here is the last bit of pipework that directs that overflow through the kitchen window and out the spout in the kitchen.

How to use it

In the kitchen, flick the power switch, and wait. That switch activates the solonoid valve, opening it. Water enters the tank and causes it to overflow, and come out of the kitchen faucet (separate to the existing tapware). A bit before we have enough water, flick the switch back off -- the rest of the water will drain from the pipe into the sink before it stops.


Yes, this is quite an unusual system.

The main quirk is that, because the "overflow" pipe is basically empty of water most of the time, there is quite a latency between flicking the switch and getting water out of the tap. There is also quite a latency between un-flicking the switch and the water stopping. There's more testing to go here, but I think it's about 20 seconds.

Also, because the faucet is open to the tank, it is possible that the tank will boil in summer and lead to dripping in the kitchen. This remains to be seen.

Reflection on goals

The goal was to have "instant solar hot water" available at the flick of a switch. I now think this was a bit naive, but I still think it will be handy for two main reasons:
  1. Because it is a shorter run of hot water (it is basically hot immediately with no wastage), it decreases the load on the main solar HWS during winter. 
  2.  For the same reason, less water is wasted in summer (when we really need it!) -- we've been catching that water in jugs and drinking it later, but it is a bit of a pain, and still results in some wastage (from the main HWS, there is just over 2 L wastage to get hot water in the kitchen)
If I was doing this again, I'd consider installing an additional full-size solar HWS down that end of the house and just run the kitchen from that. One day, I may do that (depending how we go for hot water in winter).

Monday, April 20, 2015

Update on water systems (part II)

I wrote progress report on our water systems at the beginning of January. This weekend, we had the first solid rain since then. That is over 70 days without significant rain. This weekend, I estimate we caught about 8 kL in our tanks, so the summer dry spell is officially over.

From reading the water meter, we used 8.5 kL from town water over summer to make up the shortfall in stored rainwater. I estimate that
  1. I accidentally released 3 - 4 kL from the tanks into the garden in late January
  2. The tanks at the front of the house were only connected in December, which meant we only collected 1/2 of the spring rains
Were the summer to be repeated, I think our water would last. But, can we expect future summers to be similar to the 2014/2015 summer?

This summer, versus historical summers

This summer was not unusually dry -- if anything, the rain that we had at the beginning of January was unusual and is unlikely to be repeated every year. Here's what the data say for Adelaide:

All numbers are mm of rainfall for that month. the statistics [1] were calculated over all the historical rain data I have for Adelaide (since 1884). For the purpose of this analysis I've assumed the data are stationary (ie. there's been no change in Adelaide's rainfall patterns in that time).

Assuming the rainfall distribution is normal (a wrong assumption, but probably doesn't matter for this), 35% of years will be within 1 standard deviation of the mean. Note that for the months November to March this means that 1/3 of those months can be expected to have basically no rain at all! (Note that I haven't looked at inter-dependencies in the data (ie. Does a dry February tend to follow a dry January (which it probably does)?)

For the summer just gone,  here are the numbers

Every month except January was drier than average, but none by much more than one standard deviation. In other words, it was a dry summer but it was not unusually dry.

Rainwater Model

Based on this summer's data, I've revised my rainwater model a bit. Mainly I've realised that although I have 37 kL storage, I probably only have 30 kL of usable storage. I've also increased the washing machine frequency to daily, from 0.8 times per day. Looking at the historical data, we would now have run out five years since 1884.


I set up a dripper system on the garden, and believe I wasted a lot of water there. Next summer, I want to move to wicking beds for the annual crops.
I also want to have a functioning composting toilet, which will save more water.

[1] Standard deviation is a measure of how variable the data are. In this case, it is a measure of how likely it is that a given year is a long way from the mean (average) rainfall. For normally distributed data, about 1/3 of years will be within one standard deviation of the mean, and about 7% being more than 3 standard deviations away from it. More info on wikipedia.

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

Saturday, April 11, 2015

Winter approaching, roof work, more solar

I have been busy preparing my house for winter. Last winter (the first in this house) we did little apart from install curtains, and the interior of the house regularly dropped to 13 C on cold winter mornings. To be honest, this is quite bearable, especially with the electric blanket we use on the couch when reading or using the computer. But, it would be nice if the house was a bit warmer in winter.

Heat retention

Before working on heating, it is vital to minimise heat loss, otherwise any heat just rushes out of the house again. This has two main parts:
  • drafts -- do this first. Drafts are a killer
  • insulation -- stop heat conducting out
Our house is very drafty. Here's what I'm doing (work in progress):
  • go around the entire house with a caulking gun and seal up all the skirting-board to floorboard interface with gap filler
  • go around the ceilings, and fill all the gaps where the light supply cable penetrates the ceiling
  • put door skirts on all external doors
  • put rubber seats around all external doors so that they seal
  • Install a DraftStoppa on the bathroom exhaust fan
  • replace the kitchen exhaust fan with a proper (closing) duct that goes outside the roof
If I get time, I will also
  • remove all light switches and power points in cavity walls and seal the cable penetration
  • work on the windows to improve their seal
though, I suspect this might take until next year.

In parallel to this, I have also put a heap of insulation (rockwool) in the ceiling. There was insulation already, but it is old, dirty, compressed and thin and I just laid the new on top of the old, hoping that was adequate. I really didn't want to disturb 40 years of rat urine in the existing insulation! This job is only 1/2 done -- it's very easy to procrastinate going into the roof...
I have also started planning to retrofit double-glazing to some of the windows. For some windows, this will be easy. For some, hard. I'll leave the details of this to another article in the future.


Once the house is better at retaining heat, it will benefit from having more heat injected into it. To do this, I have started building a solar space heater from some salvaged material I had. Here's what I've used:
  • some corrogated iron, from the carport I pulled down
  • some light meranti timber from the pergola I repaired
  • Some other salvaged timber of unknown heritage
I snapped a few photos as things progressed:
Materials I am using, mostly reused except for the roll of plastic sheeting top-left

Beginning of the framing. I decided to make the frame to fit the plastic sheeting rather than the iron. This means that the frame is wider than the iron, which was a bit awkward to fill without cutting a long thin bit of iron (which I didn't want to do for waste). I had a couple of pieces of flashing lying around, which I was able to rivit to the iron and seal.

The unit on the roof. I decided to use an existing TV antenna to support it. As we don't have a TV, it's good to see the antenna is finally good for something!

Another shot of it installed on the roof. A rear brace is visible. It's important that it is anchored well, as it's a bit like a giant sail on the roof. Note the aluminium rails on the roof. I used some solar PV brackets that slide under the tiles and anchor to the roof purlens. I hope it's strong enough!

A closer shot of the side. I also used tin to help anchor the struts to the frame (stop the nails pulling out). I've angled it quite steeply (over 70 degrees), so that summer sun won't make it too hot (this is because the sun is higher in the sky in summer)

A view behind. Here you can clearly see the flashing, as well as the two struts and the anchoring to the TV antenna. I plan to put in a third strut. Behind it, you can see a 30 L solar hot water system that will supply only the kitchen. More about this in a future post.

 Next step

I will buy some ducting, and a through-tile to let me get the ducting into the roof. I'll need to work out an air blower and switching. I need to insulate the back of the collector (to reduce heat loss). Note too that the unit needs to be quite well sealed, otherwise cold air will reduce its efficacy.
EDIT: I forgot to mention that I also need to paint the inside of the box matt black, and cover the front with the roll of plastic shown in the photo. I'll also put some small vents along the bottom of the box for fresh air to enter (although another option is for the box to accept air from the house, heat it and return it through a second duct -- I'd rather have fresh air I think).


The collecting area is 3.1 m by 1 m. Assuming I can get it working fairly efficiently, I think it should be equivalent to at least a 1 kW bar heater in the lounge room when it's sunny. It might even be as good as a 2 kW heater. Time will tell...

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

Sunday, April 5, 2015

The philosophy of ethics

A few years ago, I read an article exploring human attitudes to ethics. The study worked by exploring some imaginary scenarios, which I've listed below. As you read them, you might like to consider what you think is an ethical response:
  1. A train is rolling along a track. Up ahead, you see a person unconscious on the track. The train cannot stop in time, but you have the power to divert the train to another track and save the person on the track. Should you?
  2. A train is rolling along a track. Up ahead, you see four people unconscious on the track. The train cannot stop in time, but you have the power to divert the train to another track which has only one unconscious person on it. You will save the four people, but the single person will die. Should you?
If you think that both these scenarios represent a clear yes (in other words, we should work to ensure the minimum number of people dying), then consider this scenario
  • A healthy person has arrived in town. You are a doctor and know that there are four people in town who are dying of organ failure (of different organs). You can kill the new person, harvest their organs and use them to cure the dying people (thus saving four people at the expense of one life). Should you?
I think most people would object to this. It represents extreme utilitarianism -- the idea that decisions should be made based on some dispassionate assessment of utility or greatest good to the greatest number, leading to a dictatorship by the majority.

What is interesting about these scenarios is they are life/death situations. People are going to die -- it is just a matter of determining how many people, and which people. Consider this scenario:
  • Life involves a lot of hard work which you would rather not do.You have the power to kidnap your neighbour and force them to work for you for nothing. Because you will not take care of them the way you would yourself or an employee, you will then have a more comfortable life.
This seems pretty clearly wrong, however it is interesting to note that this practice (called slavery) was around for many centuries. Even when people began making ethical arguments against it, it took many decades for the practice to stop. Also note that the benefits conferred to slaveholders were
not saving their life (it was not a life/death choice like the above train scenarios) -- it was merely an economic benefit that basically amounted to stealing wealth [1] from the slaves for the benefit of slaveholders.

Despite slavery clearly being optional (ie. not life/death), and pretty clearly ethically wrong, it still took decades of campaigning for it to be outlawed. In the US, it took a major war to finish it completely. 

Here is a different scenario, that encapsulates this, and also one new concept:
  • A town enjoys its wealth and prestige, but still contains an underclass. The original source of the town's wealth (mined minerals) is drying up, so the town proposes to sell options in future slavery to an adjacent town to maintain its wealth. It will work like this: the town will hold a lottery. Buyers of tickets will have a chance at owning the grandchild of sellers of tickets (and thus obtain the economic benefit that being a slaveholder brings). All current recipients of welfare in the town must enter an agreement that they are tacitly a seller of a ticket. In other words, the town is selling a random portion of the underclass's grandchildren as slaves to support their economy.
 Let's think about the aspects of this scenario:
  • It is non-essential, but maintains a standard of living: it is utilitarian, but not regarding a life/death situation
  • It occurs far in the future
  • There is a probabalistic element -- one can't say ahead of time who's grandchildren will be affected and by how much (ie. who their owner will be and what the social climate will be)
What do you think of this scenario? To me, it's pretty clearly unethical. I suspect that most people would agree with me.

However, I also believe it pretty accurately summarises the environmental problems (eg. global warming, resource depletion, ecological collapse) that we face: someone is going to pay for our recklessness. We don't exactly know who, and we don't exactly know how much (though the price seems to be increasing year-on-year). We do know that the costs with which we burden them are non essential to us (they're not life/death), but merely make our lives more comfortable.

[1] Think as follows: The slavers benefit from the slaves because they pay them less than they would need to pay hired hands to do the same work. That difference (lost wages and conditions) between the slaves and hypothetical hired hands is essentially stolen value that the slaves earned but weren't paid.

This article was written by Angus Wallace and first appeared at guesstimatedapproximations.blogger.com
Creative Commons License
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.