Monday, 5 April 2021

Nine years of solar power. 30 MWh generated.

Today is an anniversary. Our rooftop solar power setup was installed on this day nine years ago. When the system was first installed I had two concerns, about the inverter and about the panels themselves.

The biggest concern was about the inverter. I expected that this would have a limited life because an inverter is inevitably a box of power electronics which has to work quite hard. Power supplies, especially in my experience switched mode supplies, can be quite unreliable after a few years. I've fixed quite a few of them in the past, and switched mode supplies can be quite tedious to work on. An inverter is like a large switched mode power supply which works in reverse so I didn't have huge expectations for longevity and sadly the inverter has actually failed twice, first in 2018 and then in 2020. In both cases it was quite simple to fix and because I know which end of a soldering iron to hold onto I did that myself.

The other concern was the less well known longevity of the solar panels. There are two main ways in which solar panels degrade. The first is due to corrosion should they become damp and the second due to the sun light falling on the panels degrading them. I've had solar panels on homes that I lived in since the mid 1980s, starting with several 30 cm x 30 cm panels which I used to charge batteries. Those panels were not sealed from the weather so they got damp, there was visible corrosion in some places, and their output dropped markedly over time. But around the turn of the century I bought a 12 V sealed panel to replace them. I still have that on my garage roof and it's output is still close to the specification so I hoped that the panels for the roof be similarly long lasting.

The guarantee said that the output of the rooftop panels would still be at 90% of the initial level after 10 years of use. I realised soon after the panels were installed that their peak output was significantly higher than it the specification suggested. The rated peak output for the installation was 3760 W and the installers suggested that we'd probably not see more than about 3600 W because of the angle of our roof. But within a few days I was seeing ~3990 W. I had some concerns at that time that perhaps there had been a little slight of hand on the part of the manufacturer, who perhaps under specified the panels in order to protect themselves from guarantee claims. i.e. Perhaps we'd see the panels degrade by more than 10% over ten years but that they'd still be within 10% of 3760 W or even within 10% of 3600 W in ten years time, meaning that a loss of almost 20% of output would be possible without being able to claim on the guarantee. But this has not turned out to be the case at all. There is no degradation. I can happily report that the observed peaks last summer were still around 3990 W. What's more, we're not quite at ten years yet, but the total output from the system also seems not to have dropped even slightly. After the first three years passed I noted that the system had generated 10200 kWh in total. Six years further on the total is almost exactly three times this, at 30556 kWh. What's more, if not for the inverter glitch in 2018 which costs us about 250 kWh of output, we'd actually be ahead of the first three years by now.

Graph of output over time

The orange line shows our excess production over time. It goes up in summer and down in winter, and by March we just about break even which is why the last part looks flat. When the panels were installed we had teenage children at home and our consumption was similar to our rate of generation. You can tell how long ago our children left home from this graph (some lower power appliances also made a difference). The glitch three summers ago was caused by the inverter failing and my taking a few days to fix it. The second failure was a year ago in February and lost only one day's winter output so that isn't visible on the graph.
When the panels were installed I estimated that it'd take about ten years for them to pay for themselves. Because electricity prices change, we've changed our electricity meter once and supplier more than once, it's quite difficult to work out exactly where we are now so far as the return on investment is concerned. However it's quite easy to make an approximate calculation so that's what I'll do. I know that we'd generated 30442kWh up to the end of March, and of that we'd consumed 27767 kWh and exported 2589 kWh. Electricity costs us just under 20c per kWh so we've saved about €5300 from our electricity bill. With our current tariff we get pretty much the same for what we export so that's worth about €500. This leaves us with about €5800 of our original €8000 investment returned, and at the same rate the system will have paid for itself in about 13-14 years after installation. This is about the same result as I came to about three years ago. Just four or five more years to wait, then.

Note that in reality over a whole year we use about 40% of our own generation directly from the panels and export the rest of what we produce. The electricity company doesn't bill based on this, though, so for a purely financial calculation we don't need to take that into account.

I'm happy with the system. The inverter fault was disappointing and the manufacturer's response even more so, but I fixed that. The panels are faultless. Solar panels with lower performance were much more expensive when I first started experimenting with them in the 1980s but when we installed this system it was clear that they'd pay back within a reasonable amount of time. They're now not far from half the price that they were then so someone considering installation these days can expect to see their money back very quickly indeed.

Sunday, 5 April 2020

Eight years of solar power. How much of our own generation do we consume ?

As of today our rooftop solar panels are eight years old. Here's the latest graph of electrical generation vs. consumption. You can see the eight years which have passed, the data neatly making sinusoidal shapes due to changing seasons caused by the rotation of our planet around the sun:
The blip in the graph is due to the inverter failing in 2018. It also failed in January but I got my soldering iron out sooner this time and because it was January and not the middle of summer far less was lost. Therefore no visible second blip.
The red bars show our consumption of electricity each month. The blue bars show the generation of electricity from our solar panels each month and the yellow line shows our total generation vs. consumption. Since the beginning we've generated more electricity each year than we used and in the last four years we've reduced our consumption making this difference between generation and use much greater. This led to the yellow line rising steadily higher. If you live in the Netherlands or anywhere in Europe connected to the same grid then it's possible that during the last eight years you've used some of the electricity generated on our roof as what we don't use goes into the grid.

Over the last eight years the system has produced 27039 kWh of electricity. That's 3380 kWh per year, very close to the estimated 3478 kWh per year predicted before they were installed. But this total over eight years was impacted quite severely by the period when the inverter failed two years ago. Over just the last 12 months we generated 3438 kWh, which is remarkably close to the prediction.

But while it's nice to see that we generate much more electricity than we use and the system is working very nicely, the graph also exposes an obvious problem. We never manage to generate even close to enough electricity in the winter, and of course there's never any output from our panels over night, which is exactly when we turn on our light bulbs. The installation of a smart meter a year ago has given me more data to work with and so now I can see how much of the electricity that we use ourselves comes from our panels and how much of our own electricity we use (these are not the same thing...). When we're not using our own electricity we're using what comes from the grid, and the Dutch grid is far from 100% renewable (we have of course signed up to a 100% renewable contract, but the effect of that is mostly only to make the paperwork say its renewable).
Data from the beginning of January 2019 until the end of March 2020.
Blue: our generation vs. consumption. Any month where this is above one we generated more electricity than we consumed.
 Red: the proportion of our consumption which was from our panels, varying between 0.12 in winter and 0.6 in summer.
Yellow: proportion of our generation which we consume, varying between 0.25 in summer and 0.75 in the winter.
This new graph which makes use of the smartmeter data shows a more complicated picture. Though each year we generate far more electricity than we consume (blue bars are often well above 1), our pattern of usage doesn't match the generation very well. We over-produce in summer, under-produce in winter and we keep putting our lights on when it's dark outside rather than in the middle of the day. We come closest to being independent of the grid in the summer when our panels generate more than twice what we consume, and though we don't use much of our own electricity (yellow bars) it does make up nearly 2/3rds of our consumption (red bars). On the other hand, while in the winter we consume most of the electricity that we generate, there is very little of it so it accounts for only about an eight of our consumption, the other 7/8th coming from the grid.

As you can see, having solar panels on the roof, even if they generate far more electricity than we use, does not make us even close to being independent from the grid. What's more, there's no way we could make ourselves so.

It is of course possible to buy a relatively small domestic battery which has enough capacity to store about one day's supply. If we had one of those it would allow us to consume exclusively our own electricity for March through to September, pushing the red bars for those months up to 1. However in the winter months it would be nearly idle because we then generate on average only about a quarter of our consumption, falling to a sixth in the worst month, and we are already using a high proportion of our generation (the yellow bars reach as high as 0.9), so the battery could do almost nothing to help in winter.

To be independent from the grid through the winter we'd need to store electricity from June, July, August and September to fill the trough in our production between October and February and there is no possible storage system which could do this. At present we could buy a small unit which we could fit into our garage, costing a not inconsiderable sum, to cover ~24 hours usage but to store enough to go through winter we'd need something about 120 times as large and 120 times as expensive. It's just not a sensible idea on any level.

Quite apart from the cost and I have reservations about the reliability of batteries for home storage. We already know that, as I expected in advance, inverters are not entirely reliable. It's a box of power electronics which works hard and so we should expect less than perfect reliability. A domestic back-up battery adds far more complication and is almost certainly less reliable. Why ? Because such a battery installation would require not only its own inverter circuitry similar to what we already have in association with the solar panels, but also a battery charger and the battery itself. More power electronics means more to go wrong.

Doubling the number of panels on our already full south facing
roof isn't an option. North facing panels won't work so well.
Such a battery would more than double the price of the solar panel system, more than double the embedded carbon cost, more than double the chance of it going wrong and requiring costly maintenance or replacement as a result. None of that is good news for us or for the planet. Even given all those constraints, it seems that the manufacturers' somewhat optimistic assumptions still suggest that a battery could only provide us 100% usage of our own solar power if we also at least doubled the number of solar panels that we have. As our roof is already almost full this would require us to annex our neighbour's roof entirely for our own use. That's not going to happen.

Let us remember that the excess that we generate and do not use is not lost. Investing too much in trying to use our own electricity ourselves is almost certainly counterproductive. A good proportion of our excess is consumed by other electricity users, both domestic and industrial. This leads to those consumers having lower emissions from their electricity consumption.

Reduce consumption!
A domestic battery makes no practical sense and doesn't necessarily make sense for our environment either. The best thing for us to do, and I would suggest for everyone else as well, is to reduce energy consumption as much as possible. We're continuing on that path, making our home more efficient every year. The less we consume, the easier it will be for our grid to operate without fossil fuel input. Any additional loads will keep the fossil fuels burning for longer.

Domestic and commercial
Our domestic solar panel setup is not actually 100% domestic. We operate our business, Dutch Bike Bits, out of our home, so the business is also powered from our solar panels. We try to run our business in the most ethical way we can. Therefore there is no extra energy consumption in another building and we don't use any form of motorized transport so our parcels, all of which contain goods to support people who cycle and are therefore assisting other to also use the most efficient vehicles on the planet, begin their journeys by bicycle.

Monday, 23 March 2020

Low carbon footprint hummus (super fast and economical to make)

Ingredients: Chick peas, garlic, tahini,
lemon juice, salt
Hummus is one of the tastiest things to eat for lunch on bread. It's also super easy to make yourself, even from a store cupboard if you're trying not to go outdoors (the COVID-19 pandemic is a very big problem at the moment in the Netherlands).

So if you're stuck for something tasty to put on bread for lunch, consider making hummus. It takes far less time than going to the shops, it's cheaper than commercial hummus and the result is tastier.

The ingredients required as all easily stored except for the garlic. The only fresh ingredient needed is garlic, though you can use garlic from jars if required.

In this example I used a 400 g tin of chick peas, one table-spoon of olive oil, a couple of tablespoons of tahini and small squirt of lemon juice, four cloves of garlic and a tea-spoon of salt.

Drain the chick peas, but keep the liquid. You'll find you need to add some liquid while liquidizing and this is the best thing to use. Keep any which is left over for use as liquid in other recipes (it'll go off if left too long - I put seal on the tin and use within a day or so).

The exact proportions of ingredients are not important. You can vary them to suit your taste buds and also to suit what you have in stock. Even the main ingredient, chick peas, isn't really necessary. OK, so real hummus may be a chick pea dish, but exactly the same procedure can be followed with any kind of tinned or pre-cooked bean and it you get a similar tasty result. So if you need something to spread on your bread and don't have any chick peas, try some other bean. For instance, black-eyed beans make a great spread as well.
Super simple - just put everything in a liquidizer. No cooking is required. Note that everything is shown "dry" here. It's always necessary to add some of the liquid from the chick pea tin to make it liquidize properly. You can also vary that according to taste - some like their hummus to be more liquid than others. If you don't have a liquidizer you can simply mash all the ingredients together. 

After 30 seconds or so it'll look like this. Stop when you like the consistency. It's immediately ready to serve.
One 400 g tin of chickpeas and the other ingredients together make about enough hummus to fill two average commercial retail hummus containers. We buy these only occasionally and when we do that we keep the containers which can be re-used many times. The red specks are due to an optional extra ingredient - I included a red chilli this time around. Other spices or herbs can be added in the liquidizer at the start.
Lunch. This recipe always makes delicious hummus.

Carbon footprint

As before when I made a pizza, I wanted to calculate the carbon footprint of this meal. It won't be very high for the calories because vegan food never is. And in this case it'll last for a few days of lunches so the cost per day will be low anyway. Unfortunately, I couldn't find accurate figures for the chick peas or tahini, so I warn you in advance that the following figures are to a large extent guess work. Perhaps you can help with this.

The first part is easy. The liquidizer consumes 1000 W but it's required for only a very short time. Less than 30 seconds in total. Therefore the total amount of energy consumed is very small. This works out as about about 8.3 Wh, or 0.0083 kWh. Due to the full sun today the only effect that it really had was to make our electricity meter run backward less quickly but I've calculated here as if we were using the average carbon footprint for electricity across Europe. Even so, the liquidizer doesn't do much harm:

Ingredient Quantity (g) CO2 equivalent (kg/kg) Total CO2 (g) kcal
Electricity 0.0083 kW 500 g/W 4.2
Chick peas 400 0.7 280 468
Olive oil 10 1.5 15 80
Lemon juice 10 0.5 5
Total carbon footprint / calories373.2 g718 kcal

As explained before, I cannot claim this time that the figures above are in any way accurate. The carbon intensity of tinned chickpeas and of tahini are both based on figures that I found (here) for similar ingredients. I picked "ready to eat meals" for the chick peas and "Nuts and almonds" for tahini (which is ground up sesame seed). As those two items dominate the total this makes the entire result questionable. However I have picked replacement values which are on the high side so I would be surprised if the carbon footprint of hummus made this way is greater than what is shown above.

I hope that readers can contribute better sources for those ingredients.

How much did it cost to make ?

These cheap chickpeas cost about 60 cents a tin, the small amount of Tahini is worth about 20 cents. The other ingredients perhaps 10 cents at most between them. That makes for a total cost of probably less than 90 cents for an equivalent amount of hummus as is found in two commercially made pre-prepared packs which cost about €2 each.

What about dried chickpeas ?

Dried chickpeas have a lower carbon footprint when sitting on your shelf than does an equivalent quantity of tinned chickpeas. However a lot of energy is required to boil them at home. I therefore would expect a higher carbon footprint for chickpeas that I boil myself than is the case for those bought in a tin where economies of scale will make the process more efficient, almost certainly more energy than is consumed in making the small amount of steel in a can. This seems to be confirmed by various sources.

Wednesday, 30 October 2019

The forgotten energy saving potential of the microwave oven (also quick low impact vegan pizza recipe)

The recipe book which came with my
first microwave over in the 1980s
Click these links for the recipe without the story, to find out how much CO2 was emitted, or for how far you can cycle using only the energy in the pizza.

Back in the early 80s I bought a microwave oven for my mother with some of my earnings from my first job. Microwave ovens were not really a new invention but they were not entirely commonplace yet in the UK. I don't think my Mum really wanted a microwave at the time, but she became quite convinced by it and made quite good use of it because it allowed some recipes to be cooked just as well before, but in less time. A year or so afterwards I packed in the dead end job and became a student but my accommodation consisted of one room in a building with no shared kitchen. For several months I ate nothing but salad for my evening meal, which was healthy enough but ultimately not so varied, so I bought a second microwave oven and began to learn to cook with it.

Microwave ready meals were not really a thing in the early 1980s so people didn't buy microwave ovens merely to warm up frozen pizzas. Because many owners had no previous experience with microwave ovens they were supplied with information about how the oven worked, what it was useful for, and complete recipe books. My first microwave oven was a Samsung and it came with this book.

They were both full of tempting looking meals,
completely cooked by microwave
Inside the Samsung book there were a wide range of recipes some of which became favourites during my student days. However this book was of course aimed at every potential buyer so it included a lot of non-vegetarian recipes which were of no use to me so I bought a second book which while not completely vegetarian did include a lot more recipes for things that I wanted to eat.

I ate fairly healthy food when I was a student, and very nearly every evening for a period of years I prepared my meal in the microwave oven, everything cooked from fresh ingredients. The budget was small but the food was good.

Microwave ovens are not the best way of cooking every type of food. Some of my experiments as a student were not total successes. For example, at that time I didn't understand about how bread was made and I once ended up making my lunch sandwiches out of incredibly dense lumps of dough for half a week because I couldn't afford to throw anything away. But microwaves have advantages for some kinds of cooking.

The forgotten potential
My old microwave cookbooks include short descriptions of why microwave cooking is advantageous. For instance, the microwave oven consumes far less energy than a conventional oven to achieve the same result, it saves time and it's less dangerous to use because it doesn't get hot in itself.

Much of the potential seems to have been forgotten with microwave ovens now being seen by many people as useful only to warm up low quality frozen food.

We've done this with our produce. Quick, easy and effective.
There is more awareness now than there was 35 years ago that we really should be trying to consume less energy, but while we now have an image of ourselves as being "green", we actually consume twice as much electricity now as we did back then. The average person was actually more frugal before anyone had LED lighting in their home or solar panels on their roofs.

These books are full of recipes for proper food.
Now, more than ever, we need to address our excessive energy consumption and enormous CO2 emissions. We can start in the kitchen. Switching to a vegan diet is of course enormously beneficial because a plant-based diet produces far lower emissions than does a meat and dairy based diet. But we can go beyond just the savings due to the ingredients we use by changing how we cook.

An online discussion a few days ago revealed how remarkably energy and carbon intensive a pizza can be if it is a frozen pizza, warmed up and delivered to your home. There's no obvious reason why a pizza should be so damaging. It is, after all, basically just tomatoes on toast. However this prompted me to think about one of my favourite dishes when I was a student: microwave quick pizza. This took no time to make and included no exotic ingredients so surely had a low footprint.

Quick low impact inexpensive vegan pizza

I clearly referred to this page quite often
when I was a student.
When I was a student, one of my favourite recipes was a basic microwave pizza. This took less than 15 minutes to cook from scratch, it was very simple, it was tasty and it was nutritious.

The original quick pizza recipe which I used as a student of course used cheese as a topping, but I've been vegan for decades now and so I always substitute something else. There are many commercial cheese substitutes. I've tried most of them in the past, some are better than others and you may well find one that you really like. However we cook from basic ingredients every day so we don't usually have things like "vegan cheese" in our refrigerator. For the pizza which I've made for my lunch today I've used nuts as a substitute for cheese. That may sound a bit, well, nuts, but it's not actually a bad substitute. Nuts contrast with the tomato, they provide protein and oil as does cheese and in any case many commercial vegan "cheeses" are made at least in part of nuts.
Ingredients for the base (makes one pizza)
120 g self rising flour
20 ml olive oil
35-45 ml water
pinch of salt

Ingredients for the topping
100 g tinned tomatoes, drained.
10 g peanuts, crushed.
1/2 small onion.
2 cloves garlic.
Basil, oregano, salt and pepper, nutritional yeast to taste.

Mix all the base ingredients together into a dough. Add the water slowly as you want a nice dough and not something too sticky.

Slightly oil a plate and spread the pizza dough on it. It's not a bad idea to make sure that the sides are slightly high to contain the topping, but the topping shouldn't really be wet so this isn't actually very important.

Microwave on full power for about 3 minutes. The pizza base will become puffy and rise slightly.

While the base is in the microwave you have time to drain the tomatoes (if they're too wet then the entire pizza will be too wet), chop them, crush the peanuts in a mortar and pestle and also finely chop the onion and garlic.

When the pizza base is ready, spread the onion and garlic on top and microwave for two more minutes. This softens the onion a bit, which doesn't happen so readily if you put it in with the tomato already on top.

Now add the tomato, herbs and crushed nuts and microwave for another 3-4 minutes.

Add salt, pepper, nutritional yeast to taste.

Perhaps not the best pizza in the world. Perhaps some people wouldn't even consider it to be a "true" pizza. I don't much care. It's tasty, nutritious, quick to prepare from scratch and it's all I've got for lunch today.
I like cabbage, perhaps more than most people, so I added some of that to the topping as well at the same time as the onions and garlic. I also added capers before the last microwave step and I topped it off at the very end with a few small tomatoes from our garden (it's nearly November but we still have the last of the fresh tomatoes) and a few basil leaves also from the garden. You can add anything you like.

Obviously if you're alergic to peanuts you should substitute something else. Nothing is very critical. It will probably also work with gluten free flour.

Note: This isn't a real bread recipe. It's more like a recipe for a scone (you can make good scones in the microwave). The rising action in this case is the result of a chemical reaction with the sodium bicarbonate in the self rising flour. This chemical is all that distinguishes self rising flour from normal flour and you can just add a tiny quantity yourself (its sold as baking powder) to normal flour if you want. Baking with yeast is different. If I had know about that difference when I was a student I wouldn't have had to eat solid bread for a week (see story above).
0.08 kWh consumed in
the 19 minutes it took to
make the pizza, write
down what I was doing
and take all the photos.

A low carbon meal

Having cooked and eaten the pizza we can now calculate the CO2 emissions which resulted from it. The electricity is easy: There are articles online which show the carbon intensity of electricity for different countries. Exact figures vary but for the Netherlands, and across Europe, around 500 g/kWh seems to about average. My plug-in usage meter measured 0.08 kWh used in total by the microwave. Generating that amount of electricity would normally result in about 40 g of CO2 being released. Because I cooked this pizza at lunch-time the microwave oven was actually entirely powered by our own solar panels. The electricity meter span backwards the whole time. But I will stick with the 40 g for this calculation as it's more representative.

Impacts for the ingredients are taken from this link (it refers to Finland, but I can't see most of them would vary much elsewhere).

Ingredient Quantity (g) CO2 equivalent (kg/kg) Total CO2 (g) kcal
Electricity 0.08 kWh 500 g/Wh 40
Flour 120 0.8 96 400
Olive oil 20 1.5 30 160
Water 40 0.5 (for mineral water. I used tap water) 20
Tinned tomatoes1000.3 (vegetable juice)3019
Peanuts102.3 (nuts and almonds)2361
Herbs, salt, pepper500
Total carbon footprint / calories256.5 g662

So I've calculated that my lunch had a total impact calculated of around 260 g CO2. I've been a bit unkind to myself because our electricity has a lower impact, at least in the daytime, and my water definitely has a lower impact as it came from the tap - I never buy mineral water so in this case around 200 g was probably more accurate. Either way, the total is small enough to fit into most carbon budgets.

The total weight of the finished pizza was about 370 g (very little liquid had a chance to evaporate, and the rest of the ingredients stayed in the plate). So the impact of a pizza made in this was is 0.7 kg CO2/kg food. This makes sense because it's somewhere in the middle of the impact of the ingredients themselves. It's a very long way removed from the 19 kg/kg figure given at the link for "pizza", but it's clear that what they're referring to is a ready made or delivered meal of some kind.

Another study suggested that a frozen pizza in Norway could have an impact on the climate equivalent to as much as 290 kg CO2. My recipe has less than 1% of that impact.

Following the recipe above you too can make a pizza which is quick to prepare, tasty, nutritious and has about 1/30th of the environmental impact of a delivered pizza. If it had been cooked in a conventional oven then the energy consumption would have been far higher. The energy saving potential of microwave ovens is largely not appreciated, but it should be. We are killing our planet with over-consumption of many things, including energy.

Addendum: What can we do with 662 calories?
662 calories is more than a quarter of the daily requirement for an average man and very close to a third of the recommended daily for an average woman. We need to eat that amount every day just to be healthy. We also need to exercise for about half an hour every day. So let's work out what can be achieved by using those calories.

We should always bear in mind that we need 30 minutes of exercise every day just to maintain a healthy body. In 30 minute we can cover 15 km on a bicycle, so by cycling we effectively get 15 km of travel for free every day with no impact on the environment over that of the food we have to eat anyway.

Velomobiles are the most efficient vehicles on the planet. But can you get a
subsidy to buy one of these ? Of course not. However the Dutch government
will give you €6000 to buy an electric car which produces far more pollution.
However if we ignore that and simply plug the calories that we have into a calculator and work out the potential then we find that with a standard town bike we can ride an impressive 32 km at just over 20 km/h using nothing more than the energy from the pizza. If we use a more efficient type of bicycle then we can cover 46 kms at 30 km/h using just that pizza as fuel. That works out as about 5.65 grams of CO2 emissions per km for the efficient bicycle and about 8 g CO2 per km for a standard bicycle. By comparison, in the Netherlands, an electric car produces about 60 g CO2 per km and a diesel car anywhere about 120 g per km.

A cyclist can easily travel with a tenth of the emissions of the driver of even one of the most efficient cars, but even that comparison is unfair because actually we get our first 15 km for free.

Saturday, 28 September 2019

The surprising cost of a pilot light (waakvlam)

We have a low energy bill. This is the case because we've done quite a lot of work in our home to improve the insulation so that our central heating rarely comes on, and we've tackled our electricity consumption by installing solar panels. However, we've not yet done anything to the gas equipment in our home which was already here when we moved in 12 years ago, in part because until now it's not been easy to tell which piece of equipment used most gas so should be targeted first.

While we've had a smart electricity meter for almost a year now, and I've used a plug in measuring device for much longer to check which appliances had higher than expected consumption, our energy company didn't install a smart gas meter until a week ago. The old meter was not easy to read for small levels of usage. But the new meter has made it easy to find out something which I had long wondered about: How much of our not very high gas consumption was wasted to no effect.
The new gas meter. Since installation we've burnt 5.725 cubic metres of gas.
The gas water heater
How much gas does a pilot light (waakvlam) use ?
Our house has three devices which run on gas: The gas hob in the kitchen, the central heating boiler and a separate water heater which heats water only for the shower, bath and bathroom sink.

The water heater is really old. Old enough to use a pilot light (waakvlam) instead of starting itself with an electronic igniter whenever hot water is required.

If you're unfamiliar with what that means, there is a very small flame which burns continuously, 24 hours a day, 365 days a year, just waiting for someone to turn on the hot tap so that it can be used to ignite a much larger flame to heat water.

In the past I've asked several people who work for the gas company, or otherwise seem to know about gas appliances how much gas is used by such a flame and I've always been re-assured that it's "next to nothing", "unmeasurable" or "similar to a mobile phone charger", but I was never quite convinced. The new gas meter has allowed me to measure how much gas is being consumed and the result is surprising.

The pilot light. It's small, but any gas burnt here is wasted.
Meten is Weten. It costs how much ?
One day this week we took readings from the gas meter while avoiding using any gas appliance for 18 and a half hours so that period passed with only the pilot light burning gas. Over 18.5 hours, the meter showed that 0.283 cubic metres had been consumed. That equates to 0.366 cubic metres per day or 134 cubic metres per year.

134 cubic metres of gas isn't insignificant at all ! In fact, it turns out that in summer months our gas usage is dominated by the consumption of the pilot light, which consumes more than we use for hot water and cooking combined. Over the whole year it consumes rather more gas than we use in February to heat our home. It's an appalling waste not only of gas but also of money: That pilot light costs us nearly €90 a year to run.

Like a phone charger ?
The comparison made previously with a mobile phone charger is particularly absurd as phone chargers genuinely do consume an unmeasurably small amount of electricity when they're not in use (unplugging them is something that some people do in an obsessional way because it looks like it'll save energy, when actually the effect is almost nothing at all). But this pilot light consumes a very measurable amount of gas. 134 cubic metres of gas is equivalent to about 1340 kWh of electricity. If a phone charger used that much it would certainly be measurable. It would also add somewhat more than €100 a year to the electricity bill and the charger would be rather hot rather than cold to the touch.

The next step
Obviously this old water heater has to go. That has long been the plan because actually we'd like to get rid of gas altogether. It's not happened yet because we prioritized insulation and electricity first. But discovering how much this thing wastes has given new urgency to the plan. At the very least we need to be rid of this water heater. It appears to be possible to buy an instant electric heater for about the annual cost of the gas for this, and an electric heater would effectively cost nothing to use because it would operate on the excess electricity from our solar panels which we currently export to the grid and for which the electricity company pays us very little. So I expect to change this quite soon.

Monday, 8 April 2019

Seven years of solar power: How valuable is our solar energy ?

I've been interested in solar energy since before I can remember. My first practical experience beyond things like solar powered calculators was in the mid 1980s when I put a square meter of surplus panels on the roof of my parent's home. These provided 12 V DC which I used, amongst other things, to charge the battery in my then quite new laptop computer. It wasn't until seven years ago, though, that we installed a large system on our home and the seventh anniversary of that system passed on April 5th.

Seven year summary
We have 16 panels each rated for 235 W output for a total of a 3760 W peak. In this part of the world it is usual to calculate the expected total output as the equivalent of 925 hours of full sun each year on the panels, giving an predicted output of 3478 kWh per year. In practice, over the last seven years our system produced 23601 kWh in total or an average of 3372 kWh per year.

Output per month over seven years. Red bars show our electricity consumption, blue bars show the production from our panels and the yellow line shows where we are in total now relative to where we began. Our production in is higher than our consumption on average, though obviously that is not the case in the winter. The kink in the yellow line from July 2018 is the period during which our inverter was not working (I repaired it myself)
Several things contribute to the slightly lower output relative to the estimate: Our panels are mounted at the angle of the roof and not at whatever the ideal angle might be, they face South West rather than directly towards the South. But the most damaging thing so far as the average is concerned is that our inverter failed last year and so we had no output at all for a few weeks during the sunnier than average month of July. Calculating out average output for the six years before the inverter problem we come to 3410 kWh per year which is within 2% of the prediction.

Return on investment
The monetary value of the electricity which we've generated is about 20 cents per kWh for that which we use ourselves and about 7 kWh for the excess that we export to the grid. We have exported about 1200 kWh in total for a value of €84 and consumed about 22400 kWh ourselves for which we would otherwise have had to pay about €4500. In total, then, about €4600 has been returned from our original €8000 investment. If the same rate of return continues then the system will have taken 12 years to pay for itself.

Our new smartmeter. When the photo was taken
everything electrical in our home was powered
from the panels and 2 kW was being exported
to the grid.
If the inverter fails again and this time we have to replace it then that will of course increase the repayment time. This might happen. However the panels themselves are expected to last much longer than the repayment period.

A smart meter
Something else which changed last year was that our electricity meter was replaced in December.

The new meter doesn't give us any real advantage over the old mechanical meter which span backwards just as enthusiastically as forwards for nearly seven years. The electricity costs us the same amount either way around.

Of course it does offer an advantage to the electricity company because they no longer have to ask us to read the meter or visit to do so themselves.

What the new meter does give me, though, is that it counts differently and therefore I have a little more information for future calculations. While we pay the same amount of electricity in peak and off peak periods, the meter displays them separately, for both inbound and outbound electricity. So now we can see how much electricity we consume at night time and we can see how much leaves our home rather than being consumed here.

Solar electricity is more valuable than average because it is
generated at peak times of consumption (source)
Perhaps after a year of recording this information I'll have something which which I can create an interesting graph. Thus far I have just three and a half months of this extra data, all of it from winter and spring. There's not much contrast to see.

What has long been obvious of course, and is also visible even in the small amount of data which I have now, is that our electricity is generated only in the daytime and then mostly on sunnier days. As it happens, solar electricity remains quite valuable in the Netherlands because this daytime generation corresponds reasonably well with peak usage. That means that the electricity which we export, most of what we generate, is almost certainly of use to someone else.

The first thing I made the prototype
hardware do was wiggle a GPIO and
then send serial data as shown here.
Software for a smart meter
I'm late to have a smart meter installed but as it happens, I spent a few months two years ago working on software for the prototype smart meter hardware of one of several competing manufacturers. I'm almost certain that the meter that I have now is not related to the manufacturer for whom I did the work, so my code is almost certainly not involved in reporting my own electricity usage, but as I'll never open the box of the meter and look inside, I'll never know for certain.

It was quite an interesting project for a while because it was like a return to the old days for me, when I worked on 8 bit processors and embedded software. This work was with what for me was a new processor, the Renesas RL78. It's a quirky 8/16 bit design. The RL78 assembler is styled so that the source code looks a bit like that for the Z80, but the processor is really completely different. In total I had 32 kB of flash and 4 kB of RAM to work with. These days that doesn't sound like much at all but that means this device has about the same amount of memory as the guidance computers which took Apollo to the moon so it's enough to do great things. In this case it's in a finger nail sized package which consumes micro-watts, and the little RL78 can of course compute many times faster than the AGC.

Power for a home and a business
We generate more than enough electricity to power both our home and our business, though of course I always point out that we're not actually doing so at night, or on darker days in the winter. Anyway, if you want a support a solar powered bicycle business which uses no powered vehicles then you can do so here:

Monday, 17 December 2018

Upgrading Windows to version 3 (Continuing to insulate our home with triple glazing)

Our windows were fitted by Van Dijk Services
Assen. They did a good job so deserve a link.
We knew we'd have to do something about the insulation of our home in Assen before we even moved in and every year we've made some change to improve the energy efficiency of our home. One of the oddities of 1970s Dutch homes is that while they had double glazing on the main rooms on the ground floor, it was quite common to have single glazing in places like the hall and all of the bedrooms upstairs. We fixed that problem eight years ago by installing HR++ double glazing to replace all the single glass and this was very effective. But we kept the same older windows downstairs.

It took a while for us to get around to considering the downstairs windows because we were busy with insulating the floor, the roof, the walls, installing solar panels on the roof, our bicycle parts business, and generally getting on with life, but we've now begun. In fact, we did one of the smaller panes last year because the old double glazing had developed a leak and we took this as an opportunity to experiment with triple glazing. We made measurements and found that it was effective. When the outside temperature was -2 C and the inside temperature 17.5 C the temperature of the inside of a double glazed pane was measured as 9 C while the inside of the triple glazed window alongside it measured 14 C. Clearly we could stay warmer with less heating if we replaced more of the old double glazing downstairs in our home with triple glazing.

Thus far we've replaced the glass only on the front of our home. We're still not entirely sure what we'll do on the back of house, but there is less than half the area of double glazing in the living room on the back compared with the front.

One of the old panes being removed

The replacement coming into place. It took some lifting because it weighed 127 kg.

Fixing into place

Just fitted, not made neat and tidy yet.

A tidy job completed. We now have to wait a couple of days before we can clean the glass because the sealant has to dry first.
Travel less, nor more, insulate your home
and don't eat meat
We hope this will reduce our gas consumption and our heating bill. We already have a very low energy bill because we generate more electricity than we use. The gas bill, which covers cooking and water heating as well as heating, is also low and has reduced each year. Dutch bills are increasing quite sharply this year due to increased tax on gas, but our estimate for next year is the same as this year, and the energy company doesn't know that we've taken measures which hopefully will reduce our usage further.

It's becoming more and more obvious to us that we can't continue to increase our energy usage but must decrease it. We must decrease our burning of fossil fuels. There is little time left to do this. The IPCC report from the 8th of October told us that emissions need to be reduced to zero in 12 years time. Who is doing enough to make that happen ?

Because of our concerns we are not only continuing to make our home more efficient but have also got rid of our car and stopped our business of offering holidays and study tours. Encouraging people to make international journeys to cycle is just not of this time. We must all stop behaving as if we can do whatever we like without consequences. Our children and our grandchildren, not to mention millions of people in poorer countries, are being made to pay for our own selfishness.

Yesterday afternoon. Four identical houses, ours is on the left. We're winning the race to keep ice on the roof from melting. Luckily it was somewhat warmer today.
January Update: Is it effective ?
We will really only know how effective the triple glazing is after the bills come in and we see if we've used less heating. However it's -4 C in the garden today, the sun is still on the side of the house and the inside of the double glazing at the back measure 8.7 C while the inside of the triple glazing at the front measure 14.5 C. Obviously we are loosing a lot more heat through the double glazed panel than through the single glazed panel.

Ice crystals visible on the outside of a triple glazed window when the temperature is -9 C outside. Photographed from the warmth inside.
There's also a very visible difference in that ice crystals form on the outside the triple glazed panel, proving the temperature there stays below freezing while we have a more liveable temperature inside the house. This never happens with our double glazed windows. In fact the closest thing that I have seen to this in the past was when we had ice all over the inside of the upstairs windows of our house before we replaced the single glazed panels there with double glazing. That wasn't comfortable at all !

Update February 2019 - it's working !
The front of our home, with the living room, is now fully triple glazed while the rear with the dining area (open to the living room) and kitchen remain double glazed. There's now an obvious difference in temperature between the front and the rear which I can also measure. Seeing this graph in February 2019 led me to make a simple calculation of consumption of gas for heating:

Source: Martien Visser.
I keep a spreadsheet of our monthly gas and electric consumption. We used less gas in January 2019 than any other January on record, even the somewhat colder 2017. Our gas consumption in January 2019 was 15% lower than the same month in 2016 when the temperature was very similar. A drop in gas consumption of 15% represents a greater than 15% drop in use of energy for heating because we also use gas for water heating and for cooking.

I only have one month of data so far so have to be cautious, but it appears that the replacement of the front windows with triple glazed panels has been effective. At this rate the windows will have paid for themselves in terms of nothing but a reduced heating bill within ten years even if there is no increase in the price of gas. That's a good rate of return and if it's possible I will replace the rear downstairs windows with triple glazing later this year.

Update November 2019
We've just had the rear windows upgraded to triple glazing.

This time the work was done by D & S Glasmontage, a different local company from the one who did the front windows, but known to us already because they installed new windows for us upstairs many years ago.
So now we're completely triple glazed downstairs except for the window in the back door of the kitchen.