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

Solar PV: opinions, merits, challenges

I read a lot about solar photovoltaics (PV). Some people believe they will save the world and that, in the future, we'll have electric cars with a solar panel on the roof (let's call them techno-utopians). Others believe that solar is useless. Interestingly, that latter group fall into two main groups (in my experience):

1. fossil-fuel-loving climate-change-deniers, who think that solar will never replace coal/oil/gas
2. devoted environmentalists, who believe that the cost of manufacturing solar PV outweighs its benefits (presumably, they believe that some sort of return to a non-industrial society is therefore required)

I have sympathy for the environmentalists, and can see where they're coming from, but I think they're wrong. I also think the deniers are wrong. I believe that solar PV can replace many uses of fossil fuels, and is starting to do so right now.

Making solar PV

Solar PV panels are reasonably energy-intensive to manufacture. They are a semiconductor and, although they don't require the same level of precision as (say) computer chip fabrication, PV factories still require clean-room manufacture. They also require a large number of obscure material inputs. This is energy-expensive. However,

1. Even with current technology, a solar PV system is thought to be energy positive after as little as a few years (ie. it has produced all the energy in its manufacture). [1] (remember that the system will generally last well over 25 years)
2. There is much research into lower energy cost solar panels. This may reduce the energy and material inputs still further

Solar PV performance

The amount of sunlight falling on the ground represents an absolute maximum to what energy a PV panel can produce. However, given most panels operate at well below 20% conversion efficiency, there's a lot of headroom! In other words, I'm not sure that lack of winter production is quite as bad as it is often made out to be.

PV panels "thermally derate", which means their production decreases when they're hot. On cold days, they work much more efficiently. Thus, if panels are oriented for winter production, cooler temperatures mean that they'll work more efficiently. This increase in efficiency tends to partially offset a lack of winter sun intensity. Of course, a cloudy day is a cloudy day, and production will be lower. Such is the nature of renewables.

What is solar capable of at a domestic level? Evidence

I have a 2 kW system at home, facing due north at about 22deg inclination. I have taken regular meter readings for the last 12 months, and throughout last winter I exported on average 3 kWh/day to the grid (in other words, the panels' average production was greater than this, because some of their power was consumed on site and not exported). I live at latitude 35 deg, in a climate that is often overcast and rainy in winter.

The data I've collected are shown in this article. Note that the winter data look artificially bad because at the time we had an electric storage hot water system that was consuming about 6 kWh/day (now replaced), some of which was produced by our solar PV and hence not exported to the grid.

My feeling is that my family of four could go off-grid with the system we have now. It would not be hard for us to live within our solar PV energy budget as it currently stands. It is possible that we are doing this right now, however winter 2015 will show whether our solar PV production exceeds consumption. Right now, I'm betting it will.

But, solar PV can't power industrial society!

The simple fact is that we do not know if we can run an industrial society on solar PV and wind power -- we've never done it before. I think that, given that an industrial society can be run on 1% (or less) of current power consumption, that it is possible to do this -- though there would be challenges. The question is: do we have the political will to vastly reduce our energy consumption to enable a complete transition to renewable energy?

I think we need to conceptually separate technical and political limitations. I especially think we should not limit political considerations based on incorrect technical opinions (eg. someone saying "we should not invest in solar or a transition to renewables because it is technically infeasible to replace fossil fuels and maintain our society": the latter part of that statement is unproven)

Solar is not a silver-bullet -- there are no silver bullets -- but solar can do a lot. Some people think that anything that is not perfect is useless. That logic is fallacious, in my opinion.

Off-grid versus grid-tied solar PV systems

While I'm at it, I also tire of criticisms of grid-tied solar, as if only off-grid systems have merit. In broad strokes, having a network will almost always represent better resource use than having batteries, because it means that resources can be shared (compare the installation and maintenance energy-costs of batteries versus a grid connection). If a network is available, it is best to use it (even if it is a "network" of two dwellings). By all means add some batteries if you want, as this can help the network function more effectively, but setting up batteries as an off-grid system means one requires a massive excess of storage for the rare occasion that it's needed.

Conclusion

Our current way of life is unsustainable. This means it won't continue. We cannot keep burning fossil fuels. Solar PV offers an alternative energy source that is available right now, that can probably allow us to maintain many/most important aspects of our society. 

It is not certain that we will successfully transition from fossil fuels to renewable energy. Failure to do this means our civilisation will collapse. We need to be installing as much solar capacity as possible, as quickly as possible, and not waiting for some pie-in-the-sky, perfect technology to appear. 

To the greenies who don't believe in solar PV or renewables, I say: fine, don't use them. But don't keep using coal/oil/gas powered electricity -- you know that road is a dead-end.

References

[1] http://www.nrel.gov/docs/fy04osti/35489.pdf

Storing renewable energy

Once you are producing renewable energy, there is a strong financial incentive to use as much of it as possible rather than drawing power from the grid. This is for the simple reason that (in Australia) the compensation for exporting power to the grid is as low as 8 c/kWh, whereas it can cost more than 35 c/kWh to draw power from the grid.

The optimal way to use your renewable energy is: use as much of it as possible, and draw as little from the grid as possible.

That's all very well, but the sun only shines in the daytime -- how do you use your home-generated "free" energy at nighttime? The obvious idea is to use batteries: charge them when the sun shines, and use the power later. The problem is that they're too expensive for this to make economic sense (though their price is rapidly decreasing). Is there any way around this? Here are some ideas:

Use a delay timer so that appliances run in the day time, when you are producing energy.

• Many appliances these days have timers (for example, my washing machine has a "delay" function that let's me delay a cycle's completion by up to 12 hours. I try to always run the machine in the middle of the day.
• If it's a hot day, and you think you'll be using air-conditioning, then run it during the day to pre-cool the house (this will only work well if your house is well-insulated).
• It is possible to cook during the day too, even if you're not at home, using a slow cooker, or something similar. Cooking when not there can be a fire hazard, so be careful.

Design your systems so that power consumption occurs during the day, when you are producing

• There are fridges and freezers that will create and store "coldness" when power is available (eg. these -- I have not used them though). I think it would be similar to do something similar with a conventional fridge/freezer -- this is something I plan to experiment with.
• If you run pumps, etc, then run them during the day. If you need pressurised water at night, it may be possible to use a header-tank.
• If you need electricity to heat your hot water, time it to occur during the day.

On weekends, try to perform energy-intensive activities during the day

eg.

• vacuuming the house
• cooking, especially the oven

Doing some of these will help you to use more of the power that you produce, and will increase the benefit of your renewable energy system. Note that, if you want to go off-grid, tricks like these can allow you to use a smaller off-grid system (which is cheaper!)

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

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