bits that fall through cracks

As I've described in how much do we use and renewable energy as investment, we have made an effort to reduce our power consumption, without going to absurd lengths. We regularly export about 8 kWh/day to the grid from our 2 kW solar PV system, and draw about 2 - 4 kWh/day from the grid. This is changing as we approach winter (read on).

As I said quite bluntly in Solar PV: opinions, merits, challenges, I am a believer in using the grid where it exists, because a battery storage system must be greatly oversized when off-grid to cope with the worst possible conditions -- conditions that are encountered only rarely [1]. Despite this, Australian utilities seem determined to cause grid defection: the process where people decide that they're economically better-off without the grid and leave it. I believe this will be a bad thing for Australia, because a lot of investment has already gone into the grid, and this will be wasted if people defect from it [2].

However, I'm also unhappy about our patterns of power use as they are. We don't have any fancy monitoring installed at our meter, I just take regular meter readings. I usually take a meter reading just before going to bed at about 10pm. Sometimes I check the meter again in the morning, just to see what has been used overnight. Without any intervention, we used about 1 kWh overnight.

Overnight power use

What's using all this power? Here's what I estimate/measure:

	Consumption (W)
microwave	0 (5)
mini oven	0 (5)
fridge (continuous equiv)	33
clock radio	5
master bedroom cd player	5
kids' bed cd	5
computers-office	10
macbook	8
old laptop	5
router	10

Our Electrolux ETM4200SB fridge is one of the most efficient consumer fridges (we bought it second-hand for $500), and uses about 800 Wh daily, when the fridge's environment is about 24 C.  800 Wh/day is the same as 33 W (continuous equivalent) [3]. All the other values in the table are standby power consumption that I measured myself with a plug in Watt-meter. If you add all these values up, and multiply by 12 (hours), you get about 1 kWh used overnight. Note that I've counted the microwave and mini oven as having a standby power (also known as a phantom load) of zero -- that's because I switch off the microwave at the wall.

Clearly, if we want to draw less power from the grid, this is what needs to be reduced. Particularly at night when solar PV isn't producing. On windless nights, those electrons are supporting coal power, even though we buy GreenPower [4].

The fridge is the big one, and it would be good to get a fridge like the ozefridge, that can "store coldness" for use overnight (so that it doesn't use electricity at night time), but it's too expensive to justify right now -- if we were considering going off-grid it would be a no-brainer though (because storing energy in batteries is less efficient, with greater maintenance, than storing the energy as coldness in the fridge). 

I will install proper switches on the supply cables to the two CD players, and I want to put a timer on the office computers and router (so that they're properly off at night time). EDIT: I have found that the timers consume a significant amount of power and are unreliable, so I have just been switching things off or unplugging them.

Doing this reduces our overnight power consumption to about 0.5 kWh overnight (10pm to 7am).

Data:

(Note that the resolution of these measurements is 0.1 kWh, so they are a bit approximate)

• I turned off the router and the two CD players overnight. Instead of using 1 kWh overnight, we used 0.7 kWh.
• Then I turned off the study computers and washing machine too, which reduced our consumption to 0.6 kWh overnight (I bought cheap powerboards for the study PCs (~$10 each) that have a switch on them that turns off the whole board)
•  If I turn off the router overnight our consumption is about 0.5 kWh overnight.
• We've unfortunately needed to run a night-light for the kids, which is using almost 0.1 kWh overnight

In looking to save power, this is a significant saving for us (about 20% of our total grid draw), for very minimal effort and no sacrifice.

Solar -- Winter

This is a sun path diagram. It slows the path of the sun through the sky in Adelaide across the year. The upper green line (top of the yellow area) is the path taken at the Winter solstice. The lower blue line (bottom of the yellow area) is the path taken at the Summer solstice. The red line is the path taken on May 5th (today) -- you can see it is not far from the Winter solstice path, even though the Winter solstice is nearly two months away (this is because the path the sun takes is a sinusoidal curve, and the time of greatest rate-of-change is behind us (that occurs at the Autumn/Spring equinoxes) -- the rate of change occurring near the Solstices is small (for example, if you pay attention to the time of sunrise and sunset, you'll notice it changes most rapidly at the equinox, and most slowly at the solstice).

Sun path diagram. The original is here

Below are meter reading data that I have collected. In these data, look at the date and the pattern of solar PV production and electricity consumption is clearly variable as the seasons progress. In particular, the decrease in solar PV production (green line) during Winter is marked.
Also obvious is the large change in grid-draw (red line) that occurred on September 1st, 2014. That was when we switched off our electric storage hot water heater and went to solar hot water.
There is also a further reduction that occurs in early February 2015 -- this is the reduction that resulted from my targeting of phantom loads! It is subtle on this graph, but is clearer on the next graph which shows the cumulative data. The switch to solar hot water is also apparent in this graph, as an inflexion point at September 1st 2014, and a second inflexion point is visible at early February 2015. This shows that the savings from our reduction in phantom loads are significant.

Conclusion

Once the main areas of energy reduction are targeted,  it is very worthwhile to reduce phantom loads, particularly overnight. For essentially no effort, we're saving money every day, and reducing our support for coal and gas fired electricity.

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[1] Another alternative is that off-gridders accept that sometimes they run out of power, and use candles for light, fire for cooking, and nothing else. This is fairly widely accepted by rural off-gridders, but something tells me that city folk will be less inclined to accept this.

[2] Note the idea of a proposal being "economical" -- I don't believe that economics adequately captures many of the most important elements in a decision, and that this is due to economic externalities (economic costs being imposed on non-players). Let's take an example. It is widely considered that cheaper to install a larger solar PV system and use the excess electricity to heat water. It costs less money. This is because solar panels are artificially cheap (their cost to society is much higher than the price paid for them -- I won't substantiate this claim here, it's an article to itself, but there are many such articles written already). In comparison, the monetary cost to install a solar hot water system (that uses sunlight to heat water directly, without converting it to electricity) is higher but the cost to society much lower.

This shows that "economic considerations" are not necessarily indicative of overall merit.

[3] I have considered playing with the fridge's thermostat. My idea was to run the fridge much colder during the day, then raise the thermostat so it didn't work as hard at night time. This would make a dent in our night-time consumption. I haven't done anything with this idea yet (there are clearly food-hygiene considerations here!)

[4] This is probably a somewhat contreversial statement. We buy 100% Greenpower, so in theory our power is all sourced from renewables. However, if there is a windless night, then any power consumption increases the electricity spot price, which aids coal/gas fired power stations (currently there is almost no storage of renewable energy in the grid).

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

Water at my house - part 2: hot water

Hot water

Please refer to this article that I wrote previously, which gives an introduction to the hot water system I've chosen.

At this point, only the main solar hot water system is connected. This supplies the whole house. It is located above the laundry and near to the bathroom, but is across the house from the kitchen (which is on the Eastern side of the house). Refer to Figure 1.

Figure 1: Schematic of the water connections at my house. Note the two hot water systems.

Having a hot water system a long way from where you want to use the hot water is a waste. This is because of two reasons:

1. the hot water cools on its way to where you want it. This can be reduced by lagging (insulating) the pipe
2. when you're finished with hot water, you're left with a pipe full of hot water. This is wasted.

This is bad for two reasons:

1. we're running rainwater, and don't want to run out in summer. Hence we catch the water that's coming out of the tap before it gets hot. This is doable, but is a hassle.
2. I want to run on pure solar hot water (without electric boosting), and anticipate that this will sometimes be marginal in winter. Any wasted hot water will make this harder.

Because of this, it is very beneficial to have hot water closer to where we actually want it. This is particularly true in the kitchen where solar heated hot water can regularly be used, if it's convenient (eg. fill the kettle with solar-heated hot water to save electricity).

For this reason, I've put a second, smaller, solar hot water heater on the roof right above the kitchen.It holds 30 L and cost AU$300 on ebay. Internally, this is different from the main heater in that there is no heat exchanger (refer to Figure 2 (b) in this article for a detail of the main solar hot water heater). The difficulty is that the unit can tolerate no more than about 5 psi, so can't be used in a normal fashion (ie. the supply fills and pressurises the tank, and a tap at the point-of-use controls the exit of water).

As far as I can see, there are two options to use this tank (which is not yet connected):

1. set up a small header-tank, and use this hot water system as gravity fed. This is not ideal because it necessitates a float valve and a tank up on the roof that is higher than the hot water system
2. use a tap that "pushes" water into the tank, causing its hot water to overflow down a pipe, and that water is what comes out of the faucet. This is not ideal because there will be quite a bit of latency between when one turns off the tap and when the water stops coming out. Also I can imagine that in summer the tap could drip if the tank boiled.

I haven't yet decided which of these arrangements to go for. At the moment I'm focusing on building a chicken house!


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

ebike

I often read articles about the bright future of electric cars. Here are a few.

The economics of electric vehicles

Part of the reason for moving to electric vehicles is the increasing difficulty of sustaining our oil consumption [1].The problem is that to replace the existing vehicle fleet with new electric vehicles will, I think, be prohibitively expensive. Consider that in Australia a petrol car can be bought for less than $1000, whereas the cheapest electric vehicle is more like $45000.

Because of this, I think that in general electric cars will be for rich people only, even in developed countries, and that middle-income and lower people will not own a car at all.

The electric-vehicle you will use will probably be an ebike. Consider this table:

	ebike	electric car
initial cost	$500 - $4000	$40000 - $100000
insurance	$0	$600
registration	$0	$700
range	50 km	160 km
carrying capacity	1 - 3 people	4 - 5 people
energy to recharge	0.3 - 0.5 kWh	10 - 20 kWh
battery replacement cost	$500 - $800	$15000
top speed	30 km/h	150 km/h

Clearly, cars and bikes are very different vehicles and there are many things cars can do that bikes can't. This is irrelevant, though, if the cost of the car is out of reach of many people -- as it is. I bet that this won't change either.

Using an ebike

My family's ebike was build from an old mountain bike, and a retrofit kit that I bought from gloworm bicycles [2]. I installed it myself, though mechanically challenged people could get it installed at a bicycle shop, or buy a complete ebike off-the-shelf. This kit was $1500 -- there are much cheaper kits available (starting form about $400) but we wanted a quality kit that would last.

There are a few scenarios when we use the ebike:

• we're ill, and not up to riding our other pushbikes
• we're going a long way or up a big hill, and taking the kids or other cargo (say, 30 kg) in the bike trailer 
• we're coming home last at night, and know we won't feel like cycling
• just feeling lazy that day

If we didn't have the ebike, these are all scenarios where we would drive instead of cycle, so having the ebike has meant that we drive a lot less.

Performance

The performance of the ebike is amazing. Much better than I thought. It has a 200 W motor, which doubles the power of a reasonably fit cyclist. A couple of things I have done with the ebike that I would never have imagined:

• took the two kids, lots of food/water, bike locks, trailer, etc up a steep 400m climb to go bushwalking (overtaking lycra-clad road-bikers on the way)
• accelerated myself up to about 30 km/h without pedaling at all
• Visited the hardware store and bought up, used the trailer to get it home

The power and range of this unit has exceeded my expectations. It has a nominal range of about 50 km, though after three years' heavy use its range is about 1/2 that -- and less if I'm using the motor heavily (ie. the above examples).

Conclusion

If you would like to cycle, but think you lack the fitness, or if you already cycle, but would like to decrease your dependence on your car, an ebike could be a good option.

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[1] The capital expenditure of oil majors is soaring, while their production is flat or decreasing
[2] I have no affiliation of any kind with glo-worm bikes -- I'm just a happy customer

Focus your energy, reap the rewards

There are only so many hours in the day

A common saying. I think it means that we need to focus our energies on the activities that further our goals. We need to recognise that we can't achieve everything and that if we try, we will merely dissipate our energy and achieve little.

This is also true when it comes to energy use. If you want to save power and money (we all have better things to do with our money than waste it) then you need to focus your consumption to achieve the outcomes you want, and avoid using it where it gives little or no benefit.

This article goes part-way to explaining how I have reduced my power consumption to $1/day ($90 consumption per bill).

Heating and cooling

Heating and cooling are probably the biggest users of energy in Australia (even though the climate is fairly benign here). What is the outcome are we trying to achieve with heating and cooling?: Personal comfort. This is fine, but is it really necessary to heat/cool an entire house to achieve this?

Heat/cool just the room

Instead of trying to heat/cool your entire house, why not close some doors, and just focus on the room you occupy. This will save you a large amount of money.

Heat/cool your personal space

This will save you even more, since it is only your immediate environment that you're affecting. For example:

• Use a pedestal fan to gently move air over you in summer -- the room feels much cooler when there's air movement
• Put on a jumper in winter
• We use an electric rug (eg. these) when sitting on the couch or at the computer. They use as much energy as a light bulb, but feel very warm (a typical reverse-cycle air-conditioner might use 3 - 5 kW that's between 60 - 100 times more power than a heated throw)
• Have a warm or cool drink (depending on the season)
• If your room is unbearably hot, try evaporative cooling (in hot-dry climates) instead of reverse-cycle -- your wallet will love you. An typical portable evaporative cooler uses 50 - 300 W, less than 1/10th what a reverse-cycle system uses.

Cooking

Cooking can add a lot of heat to your house. This might be welcome in winter (though it's probably not the best way), but in summer it's a clear negative. Try to cook in ways that release less heat into your house:

• avoid the oven where possible 
• use insulated cooking to keep the heat in the food 
• put lids on pots/pans (and turn the heat down)
• use the microwave, rice cooker, electric frypan, slow cooker -- insulated where possible, to focus the heat in the food (they're more efficient than a pot on the stove and much more efficient than an oven). Use a haybox cooker to achieve even more
• Then off the heat early, and cover the food with a couple of tea-towels (beware of fire risk -- take off the stove first) the food can finish cooking with the heat it already contains, and stop heating your house
• cook outside -- particularly in summer. You might consider a solar cooker and save energy at the same time
• cook for shorter periods -- a pressure cooker is good here
• substitute cook methods. For example, I've found that a pasta bake cooks well in the microwave, and then can be quickly browned under the grill. This avoids using the oven: it saves energy and keeps the house cooler.

A lot more information on the relative efficiency of different cooking methods can be found here.

Money savings

The money you save from using less energy can be used to further your other goals. Energy efficiency makes you richer! Right now, many Australians feel under pressure from their power bills. It does not have to be that way. If you are unhappily paying more than $300/quarter -- you are doing it wrong and have huge opportunities to save money.

How much do we use?

One of the things that is hard to communicate to people, in the context of reducing energy or water use, is just how much we use, and just how little we really need to use. Using less has many benefits -- mainly that we save money, and cause less destruction to the natural systems that support us.

I want to convince you that when people talk about reducing consumption, they're not talking about hardship or being a neo-Luddite. They're talking about being a little bit less wasteful and profligate.

Energy

A typical Australian household uses more than 25 kWh/day. This is an extraordinary amount of power, and is an average consumption of more than 1 kW continuous. To put it in perspective, it is equivalent to one-and-a-half draught horses working for you -- all the time, day and night, without rest. If people had to do this work, it would take five to eight energy slaves [1], working contstantly, to provide it.

The other thing to appreciate is that, for every 1 kWh of electricity you use in your home, 3 - 10 kWh of energy have been used in mining, processing, transporting, generating, distributing and transmitting that electricity to you. This is another reason to avoid electricity use where possible [2] and use lower grade sources of energy.

Cars

This is brought into sharper focus when we consider cars. 1 L of petrol contains about 10 kWh of energy. If you drive 8 - 12 km, you will probably use about 1 L of fuel, which is the equivalent of a draft horse working for about 12 hours. When a moderately fit adult can comfortably cycle that same distance in about 40 minutes, it becomes clear what a waste of energy cars are!

Water

The average Australian household uses more than 300 L of water per day. When you consider that a four-person household would drink about 20 L per day, that is a lot of water! Also reflect that Australia is the driest continent in the world. I think that this kind of water use will not be sustained, because the cost to provide the water will become too great.

Conclusion

When people talk about reducing consumption, they're not talking about hardship or being a neo-Luddite. They're talking about being a little bit less wasteful and profligate.


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Links:

[1] https://en.wikipedia.org/wiki/Energy_Slave
[2] http://guesstimatedapproximations.blogspot.com/2014/10/principle-use-lowest-form-of-energy.html

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

Detail: a solar hot water system

Solar hot water is such a good idea that it amazes me that there are houses in Australia without it!
A solar hot water system (HWS) is so cheap and easy that it can be built DIY as my friends Roman and Jana Spur have done in Brisbane (I don't think they've documented theirs, so I've included a link to another).
Solar hot water encapsulates some of the good things I've discussed in recent posts, such as:

• It is extremely simple, and is thus cheap, robust, repairable, low-energy
• It uses the sun's energy directly, without any conversions, and so is using low-grade energy that would otherwise be wasted. This energy that is falling on your roof anyway, and using it liberates high-grade energy for high-grade applications (eg. computers). It also shades the roof, and so helps keep the house cooler in summer.

Despite this, paying to have a solar hot water system installed in Australia costs a lot of money -- typically it is nearly $5000. In days gone by, most solar HWSs had a tank on the roof, coupled directly to the solar collector, through which the water flows by thermosiphon -- there is no pump required. These days, installers are less keen to install tanks on roofs because of the weight, so the tank typically sits on the ground and the water circulates with a pump. I view the pump as just another thing to break (and use power), and was not keen to get such a system. It's also possible to just install a larger solar PV system, and use that extra electricity to heat the water, but I didn't want to do that because it would be using high-grade energy (electricity) to produce heat, which is wasteful.

This article goes part-way to explaining how I have reduced my power consumption to $1/day.

After a bit of searching, I became aware of some Chinese designed and built systems that are available in Australia for around $1000 (depending on size). For some, it's possible to add collectors to a standard electric storage unit, but I decided to buy an integrated system, which is shown in the photo.

The solar hot water system, installed on my roof and plumbed in. This system cost me ~$1300, not including installation costs.

This system is differs from typical Australian systems in a few ways:

Pressure

The biggest difference, is that the tank is at atmospheric pressure (not mains pressure). The water is just sitting there, and the evacuated tubes are filled with water. Thus, the sun's heat directly heats the water, which sits in the tank. The small header tank you can see on top contains a float valve which de-pressurises the supply and ensures that the tank is always full. This has some advantages -- as water heats, it expands (some systems are known to dump all their water when it boils on sunny days). Because this system is open (note the upside-down U copper pipe at the top -- that's a vent), it can just vent steam if it boils. A downside of this I can see is that if I ever need to replace an evacuated tube, I'll have to drain the tank first.

Heat exchanger

So, if the system is low pressure, how do I use the water?
Separate to the supply to keep the tank topped up via the header tank, is a pressurised supply that passes through a heat exchanger within the tank. The cold enters, goes through a 30m copper coil within the tank, and by the time it comes out it has been heated by the hot water in the tank. The water in the tank acts as a heat reservoir -- that water never comes out the tap. The water that comes out the tap is instantaneously heated by the heat exchanger. A big benefit of this is that the hot water has no taste, since it hasn't been sitting in a hot tank, so I often use it to fill the kettle so it boils more quickly and uses less power.

The installation

This wasn't very easy, largely because I wanted the system to be on the steepest angle practicable. This is because in Adelaide, the optimal angle for a solar HWS is determined by the angle of the sun on the shortest day of the year. In Adelaide, this means a collector at 60° from horizontal (very steep!), so I had to "jack-up" the angle of the tank. I didn't get it as steep as 60° -- it's more like 45°, but trigonometry (performance = cos(15)) tells me that this should be about 96% performance at the winter solstice (vs a 60° tank). I made a big deal of getting this detail right, because I want to avoid using electric boosting as much as possible. The collectors face due North, which is also very important, and in winter it won't be shaded between 10am and 5pm.
I installed a heavy aluminium post horizontally on the roof to bear the weight. There is a wall directly beneath it, so the weight passes straight through the roof, through the rafters, and is borne by the wall. I've also put some tensioned wires to increase the strength of the frame when it is windy.

RECs/STCs

The system does not, to my knowledge, qualify for any rebates of this kind.

Total cost

I think the total cost, including getting it plumbed in, was about $2500 (about 1/2 the cost of a typical installation). This doesn't include the time I spent messing around. I estimate it's saving us about 6 kWh/day (that's what our old electric storage unit was using), which equates to about $2.10/day power saved [3]. This has a naive payback of 3.2 years at current power prices.

Performance

It works well. It was installed on September 21 (equinox), and has been boiling regularly since then. I will put shadecloth over the collectors in summer to reduce water wastage..

Future plans

I have a second smaller tank mounted on the roof nearer to the kitchen (to reduce the amount of hot water wasted in the pipes) that will be plumbed in soon. I will talk about this more in a future post.

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[3] Our electric storage was not connected to off-peak power, which would have been much cheaper to run and would have made the economics less favourable

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

Principle: lighter, simpler, less work

This post is part of a series on the principles of energy reduction.


Simple systems, that do less, and cause fewer changes from their natural state, use less energy.

Consequences

This is another argument against motor cars. Cars are

• large and heavy: compare the weight of the car with the typical weight of their occupants and cargo,
• complicated: these days, cars are not really serviceable or fixable -- replacement parts are ordered from the manufacturer and the original is thrown away

Similarly, air-conditioning is so expensive because it is artificially maintaining a space at a temperature different from its environment, which requires a lot of work.

Another way of expressing this idea is that human-built systems should work with, instead of against, natural systems as much as possible.


This post was written by Angus Wallace, and first appeared on guesstimatedapproximations.blogspot.com

Principle: use the lowest form of energy possible

This post is part of a series on the principles of energy reduction.


Some kinds of energy are harder to get/make than others. High-grade energy, such as electricity and petrol, are very hard to produce and thus have great effects on the natural systems that support us. Thus, it's beneficial to use low-grade energy where possible, and avoid high-grade energy.

An approximate heirarchy is, from lowest (on the left) to highest (on the right) grade:

Heat << Fuel << Movement << Electricity

This means that it takes a lot of heat energy to make movement energy [1], and a lot of movement energy to make electricity (ie. a lot of energy is wasted at each stage. Generally speaking, a lot of heat energy has been use to make the electricity we have in our homes. If we then use that electricity to produce heat, we have wasted a lot of energy.

How to optimise this

We can use heat energy to heat. An excellent example of this is solar hot water which uses heat from the sun to directly heat water (a process that otherwise uses considerable amounts of fuel or electricity). Similarly, heat from the sun can be used to heat our houses (using either passive-solar [2] or active solar space heaters [3]) -- this saves a lot of fuel and/or energy. Solar heat can also be used directly for cooking via a solar oven [4].

A more subtle point is that if you have solar-heated hot water, and want a cup of tea, put solar hot water in the kettle and boil that.

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[1] For example, the internal combustion engine in our car uses fuel to create movement. It does this at about 25% efficiency [5]. This means that it takes for units of fuel energy to produce one unit of movement energy.

[2] en.wikipedia.org/wiki/Passive_solar_building_design

[3] www.dummies.com/how-to/.../how-to-build-a-solar-space-heater.html

[4] en.wikipedia.org/wiki/Solar_cooker

[5] http://en.wikipedia.org/wiki/Engine_efficiency#Gasoline_.28petrol.29_engines



This post was written by Angus Wallace, and first appeared on guesstimatedapproximations.blogspot.com

I want to go back to the 1950s

About a decade ago, I read an essay that made the thought-experiment: "what if we decided to live with a 1950s standard-of-living, but with modern medicine?" and concluded that this could be achieved with  two days' work per week. I can't find the essay now (will keep looking), but I think it's a great thought. Let's think a little about life in the 1950s (in Australia, anyway -- this was not the case in other countries):

• One income could house and sustain a family
• Cars were rarer
• People generally ate fresh, home-cooked food
• Community was very important
• Most people grew at least some of their own food
• Public transport and cycling was common
• Lives were simpler and less hectic
• Our per-capita footprint on the environment was much lower (we weren't destroying our ecological support-systems so quickly)
• Electricity consumption was much lower, fuel consumption was much lower
• Most food was organically grown
• Market gardens and small-holder farms surrounded cities and provided much of the food
• People ate less meat and fish
• People owned less stuff, and produced less waste
• Australia had a manufacturing base, because people were prepared to pay a living wage to people who made things

I could go on.

The point, though, is that in the 1950s the average Australian lived a simple life like that advocated by many environmentalists in response to the current crises that are plaguing our society.

I think that, in many respects, we have regressed from the 50s. Yes, we currently live a much more sophisticated (and more consumptive/wasteful) lifestyle than people did then but I suggest that this will not be sustained. I think that if we keep over-reaching in this way we will end up greatly impoverished and will not even be able to sustain a lifestyle of the 1890s let alone the 1950s. If, however, we can control our consumption now, a 1950s lifestyle could be sustainable.

Why is this so rarely discussed?

I think a big reason this is not mentioned is because of the social issues prevalent in the 1950s. Yes, the 50s were relatively sexist, classist, racist and bigoted. I am in no way advocating a return to those values. But, I think we can maintain modern egalitarian* values with 1950s levels of consumption in a sustainable way.
I think another reason is that we are so obsessed with the idea of Progress, and that we are somehow better than people back then.

My vision

My goal and vision is to live, essentially, with consumption levels of people in the 1950s. I am yet to renounce many modern luxuries (eg. I have a hand-me-down mobile phone, and an old computer with broadband -- and myriad others, of course -- this is an experiment and work-in-progress!). My family owns a car, but I want to act (as much as possible) as though the car is not there. As part of this, I want to embrace the 50s aesthetic. This is not novel (the retro/vintage movement is in, ahem, full swing), but forms a component.

My challenge

Lots of people like to talk about "traditional values" -- I challenge you to embrace the traditional values of thrift, low-consumption, lack-of-pretension and simple living.


The post "I want to go back to the 1950s" was written by Angus Wallace and first appeared at guesstimatedapproximations.blogspot.com.au

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* an interesting note is that Australian society was actually more egalitarian in the 1950s than today. Today the difference between the wealthy and the poor in Australia is much greater. Like in so many areas, we are better at talking about egalitarian values today -- in the 1950s, people just got on.

Imagine 100% renewables -- what happens when there's no sun or wind?

Imagine an Australia running on 100% renewable energy:

1. Each house has 2 - 5 kW of solar PV
2. Each house has 1 - 2 days' energy stored (eg. in batteries, or similar)
3. Ditto for commercial and industrial buildings
4. There are also scattered wind farms and singleton wind turbines where feasible
5. There is scattered storage that is owned by the utility

What is the issue? Intermittency.

Intermittency

This is the problem that is always raised when renewable power is promoted: renewable power is intermittent:

• solar PV only produces electricity when the sun is shining
• wind turbines only produce electricity when the wind is blowing

Neither of these conditions are met all the time, so does that imply rolling blackouts?

Problem

Imagine an interval between sunny, windy periods in NSW during which the local renewable generation produces very little, if any power. Imagine that there is somewhere else in Australia that at that time is producing plenty of power. Let's say it is in SA. From where will people in NSW get electricity?

Solution

Luckily, our scenario includes some distributed electricity storage. There is not very much (a typical off-grid house would have 5 days' electricity storage or more), so it is much cheaper. It does mean, however, that after a few days of cloud and no wind people's batteries would be running down.

The solution is to use the existing grid. While Australia's current grid cannot send enough power around in real-time (ie. if it's sunny in SA and cloudy in NSW, SA can't in real-time supply Sydney's power demands), what is rarely considered is that this is unnecessary. Remember that the existing grid is vastly underutilised -- it is built with peak demand in mind (which occurs a couple of times per year). Most of the time, the grid is running well below capacity.

In this scenario, power can be sent from SA to NSW overnight, when demand is low, to keep batteries in NSW topped up. It does not need to power customers in real-time -- all it needs to do is stop the batteries going flat.

To restate it another way -- the transfer of power from SA to NSW would not need to match the maximum instantaneous rate of consumption in NSW -- it would only need to match the average rate over the period covered by the batteries. In fact, even this is not required since the batteries can be assumed to begin this period relatively full and end it relatively empty.

By doing this, we would obtain maximum benefit from the existing grid infrastructure, and also be able to install a much smaller storage system, while retaining the benefits of distributed generation.

In other words, I question whether the oft-repeated statement that high renewable penetration requires a much more extensive grid is true. We can use electricity storage to greatly mitigate this (though by exactly how much, I am not sure. Some time, I will try to get the data together and run the numbers).

The post "Imagine 100% renewables -- what happens when there's no sun or wind?" was written by Angus Wallace and first appeared at guesstimatedapproximations.blogspot.com.au

When does it make sense to go off-grid

Consider a household that already has enough PV to cover their personal use, just not always at the times they want to use it. They might consider going off-grid by buying batteries, etc.

This is the situation I'm in. We use about 3 kWh/day, and are exporting, on average, about 7-8 kWh/day -- so we certainly have plenty of power. If we went off-grid, we'd probably want at least 5 days' power, so 15 kWh storage. I haven't priced this exactly, but I think such a system would be at least AU $8000.

What would this save us? Well, currently our exported power is sufficiently above our consumption that I estimate our bills will be $0 henceforth (ie. I think we are exporting enough power to pay for our consumption and the grid connection). Therefore, there's no benefit to us doing that!

In fact, at current electricity prices, I can't think of a situation where doing this would be justifiable. Perhaps if we were paid significantly less (ie. as the difference between what we pay to use power versus what we are paid for supplying power becomes greater, such a system would become more attractive. What sort of difference would be needed to make this worthwhile?

I'm assuming a fixed cost of $8000 to take ourselves off-grid. I recognise that for most people (because of their greater consumption) it would be more expensive. However, in that case their savings would be greater. It's not proportional though: because we use so little power, the connection fee makes up a sizeable proportion of our bill.

Exploratory model

I have done some basic modelling of how variations in our electricity billing would affect the payback of a basic off-grid system.  There are two main components to our bill -- a quarterly service fee (connection fee), and a charge per unit of energy (kWh) used. I've modelled a range of fess and tariffs, which are shown in the table below. Different connection fees are shown across the top, and different tariff structures (the difference between our consumption tariff and the Feed in Tariff (FiT)) are shown down the side. The values in the middle is the estimated ROI for the appropriate fee-tariff combination. My belief is that the "difference in tariffs" will go up, while the basic consumption tariff stays about the same and that the quarterly connection fee will also go up. There is talk of increasing the cost of connection, so that "solar users pay their fair share" (factually incorrect: it's not that houses-without-solar subsidise houses-with-solar, but that houses-without-airconditioning subsidise those with airconditioning. Utilities don't want to discourage consumption. These articles discuss in detail.). Also, the cost of off-grid battery storage is likely to decrease markedly in the next few years, but for simplicity I've only considered an $8000 system.

I've colour-coded the data, and believe that the red ROI levels are uncompelling. The orange is marginal but might be considered by someone who was passionate about being off-grid. The green results are starting to look economic.

I modelled the payback on the basis of varying the difference in consumption tariff and the FiT. At the moment, we pay AU$0.35 / kWh for electricity we use and get AU$0.24 / kWh for electricity we export to the grid. The difference is AU$0.11 -- but I expect this to increase in the future (especially when the FiT decreases in 2016). I've also modelled changes in the quarterly connection fee. Now, it is $70/quarter, but I think it's likely to increase.

Results

With our current tariff structure, I estimate the ROI for an off-grid system to be 6% -- this is not compelling. If the tariffs remain the same, but the quarterly cost increases to $130, I estimate the ROI to be 9% -- still marginal. Similarly, if the quarterly cost remains $70 but the difference between import and export pricing rises from AU$0.11 to AU$0.22 (quite possible in 2016), then I estimate the ROI to be 9%. If the difference between import and export pricing rises to AU$0.30 AND the quarterly cost increases to $100 (I consider this reasonably likely in the next 3 years), then the ROI is 12% -- this is starting to look like it could worth doing. Couple that with a 25% decrease in the price of off-grid systems in that time (given that some people are predicting a 50% decrease in price by 2020, this seems plausible) and the ROI is 15% -- I would consider doing this, and I bet a lot of other people would too.

Caveats

One caveat is that because we use so little power, changes in the quarterly connection fee have a big affect on the ROI. For households that use a lot more power, this will be less important and only the "difference in tariffs" will have much effect.
A second caveat is that this model does not consider any on-going expenses associated with maintenance of an off-grid system.


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

Renewable energy as an investment

Summary: My wife and I have invested about $8000 in solar PV, a solar hot water, and a better fridge. I estimate the return on this investment to be 17.5%, which I think makes a compelling case for people to do similarly.

I moved into my house in early 2013. Just before Christmas, we had a 2 kW solar PV system installed. We decided to get a good one, with an SMA inverter, and it cost about $5000. I realise there are similarly-sized systems that are much cheaper, but I wanted to be more confident in the longevity of the system.
Since buying it, I've been monitoring our power use quite closely, but we have always been quite careful in our use. We generally don't use heating or cooling (though we do have an electric blanket on the bed, and an electric throw for the very chilly evenings) -- the house doesn't get below 13 C or above 30 C so it's pretty bearable.
When we bought the house, it had an electric storage hot water system (300L), which I knew was a very inefficient way to heat water. My goal was always to switch to a solar hot water system. My feeling was that the existing electric storage unit would likely use about 3 kWh/day, which I thought was pretty wasteful and uneconomic. To install a hot water heater in Australia costs nearly $5000. For what it is, this is a lot of money (a solar hot water heater is something that can be built pretty easily). I started investigating cheaper options, and found that a Chinese-made 240L evacuated-tube and built solar hot water systems can be bought in Australia for about $1300. I bought one, and installed it on the roof. The setup I've gone for is quite complicated, because I decided to get a separate smaller unit to supply the kitchen, and also wanted to switch the house to rainwater (other posts to come).

We finally did this two weeks ago, and I've been surprised. It appears that the electric storage hot water system was using more like 6 kWh/day -- a huge amount of power! Without it, our average daily consumption (admittedly only over a 2 week period) is 3 kWh/day. I have done a bit of modelling of the estimated savings that we are gaining from the combination of the solar PV and hot water system, and I estimate that we are saving, on average, almost AU$4/day. At this rate, we will repay the investment in just over 5.5 years (ignoring any kind of future discounting, or cost of finance) for a ROI of 17.5%. Assumptions:

• 0.35 c/kWh cost of electricity drawn from the grid (this is the rate in SA)
• 0.22 c/kWh paid for electricity exported to the grid (we got in for the last available Feed in Tariff (FiT), so for people installing now the economics will not be quite as good. Also our FiT will end in 2016 which will affect the future economics. By this time though, the system will have paid for half its cost.)
• boosting of the system (using electricity to heat the water when the sun is insufficient -- eg. the middle of winter) is sufficiently rare not to affect the overall statistics. I think this is likely.

The last assumption might seem unlikely to you -- when we've been through winter, I'll comment on the frequency with which we need to boost the system. However, the analysis I've performed so far ignores that some of the electricity produced by the PV is consumed directly (ie. it's offsetting our consumption), which means that our savings are actually a bit higher than $4 / day, and hence our ROI is actually a bit higher than I've calculated.


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