What's in a name?

I've just changed the name of this blog from "Building a house" to "Low energy building". Hopefully this will more accurately describe the content, but it should more properly be "Stuff vaguely relating to low energy building, and anything else I feel like writing."

The name of this URL "minuszeroeco" has not changed. When I put that in, it wasn't the first choice, but I hope it conjures up something. I'm in perpetual apology for using "eco", which has been used with such variety that it has little meaning left. Most obviously it appears at the beginning of "economics".

"Minus zero" may have come from a Boomtown Rats song "Wind chill factor minus zero", from their seminal 1978 album the Fine Art of Surfacing. It seems to lack precision and I've never been completely sure what it means. If it's zero then it is neither plus nor minus, and if it's minus, then it's not really zero.

This may be something like 2+2=5 for large values of two. In other words, if each 2 is actually 2.4, then adding them together will get to 4.8, which rounds up to 5. So minus zero is somewhere under zero but not quite minus one. And I suppose that's what I was aiming for while building the house. I wasn't just trying to make a house that breaks even, or comes out with zero emissions. I wanted to make sure that it really did have less than zero emissions.

Golf loss is solar farm gain in Japan

An interesting story here from Electronics Weekly.

There's a triple victory here:

First, more generation of green power. (As well as tee power, fairway power, and a bit of bunker power if it's not too shaded.)

Second, less water wasted keeping the greens green.

And third, less people playing golf, which "has too much walking to be a good game, and just enough game to spoil a good walk." (Harry Leon Wilson, 1904)

A fully transparent solar cell that could make every window and screen a power source

This is really clever. Not sure how effective it will be though. I'm sure it could make every window and screen a power source, but it probably won't.

The clever part is that it diverts the invisible light coming in through the window towards the edges, where it is converted to electricity by solar cells. As well as the visible light we see, the sun has infrared radiation, at a shorter wavelength, and ultra violet, at a longer wavelength. Other approaches to solar glass have usually reduced the amount of light getting through, by applying a solar film over the windows, containing semiconductors. Since the semiconductors are not covering the glass, and the diverted light is outside the visible spectrum, this won't make any difference to how the windows look. 

I would show you a picture, but you wouldn't really be able to see anything!

Find out more at: extremetech.com

Another amphibian

We get loads of frogs in the garden. Then recently I saw this chap.

​

My son told me about him. "He's my pet," he said.

"Oh, what's his name?" I asked.

"Tiny."

"Why do you call him Tiny?"

"Because he's my newt!"

A Japanese fire bellied newt, I think. 

Do Google spreadsheets excel?

I started writing this post a couple of years ago, but after spending a few hours getting the charts working for http://minuszeroeco.blogspot.jp/2013/12/when-did-we-turn-heating-on-last-year.html, 

I ran out of time to write about it. 

It was about that time when I started banging against my head in an apparent ceiling on the amount of data a google sheet could hold. This was big data, but not that big. Or maybe it's just the greedy way I set up excel files. 

There is a new function in Google sheets now, called explore. A data bot goes in and looks at all your data, then plots graphs, scatter charts and histograms. It gives text descriptions of what is going on. I didn't need a computer to tell me that for every increase in generation of 10, "exported" increased by 10. But well done. This could have shown me a correlation that I didn't know about. 

This graphs is really good though:

It looks like it's been made with a thick paint brush, that has then started running in a few places. The line hints at the sine wave of the orbit around the sun. The cosmos has conspired with the climate to produce this one.

The histogram of solar generation is interesting too.

How much heating does the house need? Part 2: like, how much money does it cost?

The question of how much the heating costs is more straightforward. The electricity bill is the only payment for heating, and the heating only comes on at night time, so I don't have to worry about the cost of my solar electricity.

The electricity bill is all thrown in together so I can't just isolate the cost of the heat source, and even if I could, the same system is used for hot water and heating, so it would be difficult to separate those two costs.

We need to look at how much the electricity costs when the heating is off, look at how much it costs when the heating is on, and the difference is the heating cost. Simple enough, but there are a couple of questions.

First, the hot water is generated by an atmospheric heat pump, which takes heat from the nighttime air. It will use a lot more energy to get heat out of the winter air, when it drops ten below zero for a few days, than to get heat out of the summer air, which sometimes stays over 25. In other words, part of the extra cost of electricity in winter is for the hot water rather than the heating. Also the incoming water will be colder in winter, so it will need to be heated up from a lower temperature, and use more energy still. How much of the extra cost in winter should be attributed to the extra cost of hot water?

On the other hand, the hot water tank and pipes are in the house, so some of the hot water heat is going to be helping heat the house. Should that be taken into consideration?

Another thing that may make a difference is that fact that we pay different amounts for electricity in the day time, at off peak time and at "at home" time, and we pay nothing for electricity if it comes from our solar panels. In the winter it may be more overcast in the day time, so while that electricity would have cost us nothing on a sunny summer day, in the winter they may have charged us 24 yen per kWh. In the summer, when the heating is off, we only buy one or two kWh of day time electricity, but in the winter it's more like eight or nine. Is this going to matter or will it just be a few hundred yen a year?

We use about ten times more electricity in the morning and evening "at home" times, and three times that off peak, so imported day time electricity is only one or two percent of our total.

The second question is easier, so I'll answer that first.

No. Heating cost should just be the energy used in the heating equipment. 

Here are three estimates with different answers to the first question, starting high and pessimistic, and finishing low and optimistic. Each estimate is based on two or three years of data and rounded to the nearest 100 yen. 

1. The no-heating cost is estimated from the months of June to September, when heating is not needed. This is multiplied by twelve and then subtracted from the annual electricity cost.
20,800 yen per year
This will not take any account of extra winter costs for hot water, and will include the incidental heating costs that I just said should not be included.

2. The no-heating cost is the average of the months of April to November, when the heating is off. This is also multiplied be twelve and subtracted from the annual electricity cost.
12,500 yen per year
This is not as pessimistic as the first figure, but it is still treating some of the incidental costs as heating costs.

3. The no-heating cost is the average of April, May, October and November, the colder months when the heating is off. This is subtracted from the bill for each month when the heating was on, then an annual heating cost was added up and averaged.
3,600 yen per year

Our monthly electricity bill is the lines at the bottom. Can you see the heating on it?

I could probably try a bit harder and get an estimate that would be paying me to heat the house. Or, I could round it to one significant figure and call it around 10,000 yen. 

How much heating does the house need? Part 1: Primary Energy Factor

Heating load is one of the requirements for a passive house. Although the passive house standard does not eliminate heating, it severely limits the total amount of heating needed over the year, or the maximum needed at the coldest time of year. The limit means it is possible to heat a passive house just by adding heat to the incoming air with no central heating or other equipment. We have underfloor heating, but the house still meets the standard, which is 15 kilowatt hours per square metre per year.

After over three years of living in the house, we should have some idea of whether the actual performance of the house is the same as the simulation. The total primary energy use is easy to work out, and it is in the same ball park: 106 kWh/m2a compared to 94 in the simulation. All our energy is from electricity, and it is metred, so we know exactly how much is being used. To find the primary energy, you need to multiply the electrical energy by 2.7 to account for inefficiencies in power stations and transmission. 

"2.7" is the primary energy factor. This number may vary depending on where your electricity comes from, but the number in Japan seems to be the same as for the EU as a whole.

The Passive House simulation, and my measured calculation is assuming that all our electricity comes over the grid, mostly from fossil-fuel power stations. Around 80% ours does. The other 20% is from our solar panels. Since they are only on the roof, the transmission losses are low, and they are not burning any fossil fuels, so their running primary-energy costs are zero. We do have to pay back the primary energy used in their manufacture.

It's difficult to find a definitive list of primary energy factors. Development of the Primary EnergyFactor of Electricity Generation in theEU-28 from 2010-2013 gives some answers, not strictly relevant to Japan. The figures it gives are more useful as averages for the EU as a whole. This Leonardo Energy confidential report from July 2011 shows a range from 2 to 3 around Europe, and gives a primary energy factor for photovoltaic power in Poland as 0.7.

The Centre for Alternative Technology has a few more ideas on this, suggesting a square metre of panel used 250 kWh of energy to make, in 2004-2006. They also note that production goes up, and efficiency increases year on year. We should probably double this figure to account for transport and installation, just to be pessimistic. In a 30 year lifetime, each square metre of my panels will produce something like 7000 kWh, around fifteen times the energy to manufacture. So the primary energy factor is about 0.07. The Energy Skeptic has more information on this.

Graph from IPCC, via Energy Skeptic

We can place the primary energy factor at an arbitrary point between 2.7 and 0.07 and get the actual primary energy use to be the same as the simulated energy use.

It may be more sensible to accept that the simulation used the figure of 2.7 for all the electricity, so we should use it with the actual figures too. And we can easily explain the difference between the simulation and actual figures by the amount of hot water we use, which in bath-loving Japan is higher than the shower-based European figures.

Whichever way you look at it, this house uses less primary energy than the Passive House standard of 120 kWh/m2a.



Edenhofer, O.; et al., eds. 2011. IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation. Cambridge, UK, and New York: Cambridge University Press.   http://srren.ipcc-wg3.de/

Eroi panels

In all attempts at reducing our environmental impact on the planet, there is a haunting question of whether it is worth it, or if the effort we've put in to do our bit is actually going to make things worse.

There's a scene in some World War Two movie where one Nazi turns to the other and asks, "are we the bad guys?" I often ask myself this question, and the answer is usually yes.

And so with solar panels, I wonder whether they really are making a difference to the planet, or if they are just another part of our plan to convert as much of the fossil fuels under the ground into carbon dioxide in the atmosphere as possible. If they are just leaves of garnish that have been grown with gallons of water and transported with gallons of oil to make our plates look a little greener.

Financially they seem to make sense. They're working for me everyday by just lying there in the sun on my roof, and I'm looking at a total payback of around 8 or 9 years.

There's also a sense of security that I have my own power source in case of emergencies. I know that they will only ever produce power in the day time, and if we were snowed under they wouldn't be very effective, but at least the sense of security is there. I'd be able to keep the fridge working on a sunny day.

But are they saving the planet, or are they just green bling? Are they like parsley on the side of the dieter's plate, next to the potatoes and the large piece of steak?

One metric that can shed light on this is EROI, the energy return on investment. We're familiar with financial returns on investment. For example, if I put 10,000 yen in the bank, with the 0.02% interest rate it will take three and half thousand years for the bank to pay me 10,000 yen in interest.

The energy return on investment tells us how many units of energy will come for every unit of energy we put in. For solar panels we need to consider how much energy was used in the manufacture and transportation of the panels, and their installation.

According to a review by the Energy Skeptic of a report on Spain's experience with solar power, the energy return for solar there is low at 2.45. Optimists put it higher, and with improving technology it is increasing all the time. However, the mines digging the materials out of the ground are not solar powered, the factories making the panels may have a couple on the roof, but most of their electricity is coming in from the grid, and the transportation is mostly powered by fossil fuels. Research at Stanford claimed that all historical energy used to make solar panels until now will be repaid between 2015 and 2020.

It's a different story to coal, which found an early use in steam pumps removing water from coal mines, and was instrumental in extraction of the energy source from the ground. Coal has a much higher EROI, around 18 according to meta-analyses by Mason Inman in Scientific American, retold here.

Nuclear, meanwhile, is rated as low as 1 by some, and designated a sink of fossil fuels. The nuclear industry give it a score between 40 and 60 and claim it is a global-warming saviour. Politics is very much alive in these figures:

Hydro-electric 40+

Wind 20

Coal 18

"Natural" Gas 7

Solar 6

Nuclear 5

(Data from Scientific American cited in carbonbrief.org - I couldn't thoil the price Scientific American charge to read the original article.)

So they may be helping save the planet or they may be helping to destroy it. On the other hand, it may be that the panels will help to drive up fossil fuel prices and get us off them quicker. An interesting statistic from wikipedia's article on EROI is that the energy return on investment for US oil and gas halved between 1970 and 2005. In other words, while solar power is becoming cheaper to produce, both in terms of money and energy, the more oil and gas we get out of the ground, the more energy we need to get what is left. 

As a metaphor for this, you can imagine that someone has hidden several pennies around your house, and you're trying to find them. You'll find the first ones fairly quickly, but as you go on, they will take longer and longer to find. You may go and buy a metal detector, at which point the metaphor reveals that improvements in technique may speed up your retrieval rate. This will not help when there is nothing left to retrieve. 

I remember at school hearing that fossil fuels were going to run out in thirty years. When I told my father this, he said that he had heard that when he was at school. My son is no doubt learning that same thing at his school. Fossil fuels are a finite resource, but they may not be exhausted. It's more likely that their cost will increase, while the cost of alternatives is decreasing. 

And when the energy economics switch over so that fossil fuels are unviable, at least a lot of us will have panels on our roofs to produce electrical power, and keep our fridges running on sunny days when the roof is not covered with snow.

They don't half write some nonsense about solar

This was going to be titled: "Solar has become the most efficient way to generate electricity"

Solar has now taken over as the most efficient way of generating power.

This happened now. Right now. At the precise second you read this sentence. Or this one. Or at the time I wrote it. Or at least sometime this week. Or this year. Or maybe next year.

Of course you can't really give a precise time, any more than you can decide the precise point where the economy changes from bust to boom, or exactly which sip of drink was too much the day before a hangover.

Also, there is no single way to determine whether solar is more efficient than other ways of generating power. If you look at the cost of a power plant per unit of energy coming out of it, then solar is certainly a lot more expensive than options such as coal or uranium. However, if you look at the cost of the energy at the point of use--for example your house--then solar is often cheaper, since the electricity is there where you need it, and you don't have to pay for the line costs. As well as the availability of sunlight, this depends on the cost of electricity, the cost of panels, and any subsidies, which are all local factors. And you probably should not include subsidies if you want to really know whether solar is cheaper, but then you should probably adjust for the subsidies that coal, oil, gas and uranium get.

And even though solar in many places is cheaper where you need it, it may not be there when you need it, since solar panels are less efficient if it's cloudy, and even less efficient if it's dark.
The Japan Renewable Energy Foundation seems to be quite positive about solar. Although they may be as biased as people on the other side whose heads are stuck in oil barrels.

Reuters has an article from June 25th with the ambiguous title "Japan to stop inefficient coal-fired power plants being built" which in fact is about Japan's plans to build efficient coal-fired power stations.

There seems to be a lot of confusion over solar in the press, especially in the Japan Times. I think the wind is changing right now, so the weathercocks are all spinning aimlessly and pointing in different directions.

According to Reneweconomy.com.au, Deutsche Bank claims there will be grid parity by 2017 in 80% of world markets. Wikipedia has a good page on grid parity, which mentions Matsumoto as an example, and shows that is is already here. This backs up the evidence I have on my electricity bills.

Meanwhile global coal production has been increasing at least since James Watt put the first steam engine at the top of a coal mine to pump water out, and since Fukushima Japan was helping this trend, so it's distinctly possible there are big contracts for importing coal, with big backhanders for Abe and his mates. Business as usual, or is it? Another factoid I heard recently was that coal uses more land than solar for generating electricity.