Monday, 17 April 2023

More more solar panels. Do we now have enough energy for a gas free home?

We now have four solar panels on our garage roof. They're at an angle so that they face exactly toward the south.

Today with help from a friend we installed two more solar panels on our garage roof. This means we have four 400 W panels on the garage roof to work alongside the sixteen 235 W panels which are on the roof of our home.

The original two garage mounted panels were in the shade until about 9 am so you can see from this graph that they suddenly "wake up" at that time. The new panels placed today do better a few minutes earlier as they'll be earlier out of the shade.

The roof of our home is oriented south west, while the panels on the garage are oriented directly toward the south so as discussed a few days ago they compliment each other. The garage is shaded by our neighbour's home early in the morning but as the new panels are further to the south and will be shaded less (even though to arrange this we had to push the older pair slightly further north) we're hoping that we see a little bit more electricity early in the morning than was previously the case.

The new set of panels, closer to the camera, are mounted at just 12 degrees, vs. the 24 degrees of the set which we put up last year. This will mean they have slightly lower output overall, but they will shade the older set behind them less often due to being lower at the back and they will catch the morning sun from the east a bit better due to their lower angle creating less of a self-shadow.
The usual "back of an envelope" design process

Last time I couldn't get commercially made hooks as everything seemed to be sold out everywhere. This time I used commercially made hooks to hold the solar panels in place as they were available inexpensively. Otherwise the frame which these panels are mounted on is very similar to that of the last pair of solar panels except that they're at 12 degrees from horizontal this time instead of 24 degrees. This is to decrease the chance of the new set of panels putting the slightly older set behind them in shade and to hopefully increase their output early in the morning when the sun comes from the east. We'll see if that works out.

So far as possible I collected the parts required for this job by bike. Three meter long pieces of wood do make for a slightly unusual sight on the cycle-path.

In total the bill for the two new panels, all the parts required to make the brackets and all the parts required to make a safe connection to our electricity supply added up to about €550.

Helping a friend with his installation a few days ago. He then helped me today. Doing things for each other certainly helps to keep costs down !

We now should have enough energy

Our gas supply was removed last week so we need to have a heating solution for next winter which does not involve gas. As discussed a couple of weeks ago, we actually didn't use much gas at all, so replacing it shouldn't require too much electricity. Added to the overproduction of electricity which we already had before they were installed, the new panels ought to be enough to make our net electricity consumption very close to zero for the year.

As it stands right now, our energy company is asking us to pay €5 a month for energy, with an expectation that we will have overpaid by €290 at the end of the year. That seems to be working out quite well !

Wednesday, 5 April 2023

Eleven years of rooftop solar power - and it's a new record year

Our rooftop solar panels have been in place for eleven years, and the highest output year was the most recent. In total the rooftop panels have delivered 37591 kWh to date.

When we had our rooftop solar panel system installed in April 2012 we were told to expect an output of no more than 3150 kWh per year due to the angle of the panels and the direction they face on our roof. We were also warned that output would drop slowly over time. In practice we actually saw an average of 3357 kWh over the first ten years. Until now the highest output year was the second year after they were installed with 3516 kWh, but that record was broken in this last year, 2022-2023, which is year eleven for our system. No less than 3614 kWh of electricity came from our panels last year, which is nearly 3% more than the previous record.

We actually generated a little more than this because we added a couple of extra panels in September. But because these have only been operating through the darker months until now, they've only added slightly to the total, bringing it to 3780 kWh.

The new peak output wasn't the result of a particularly sunny winter. March, was particularly cold and dark, with snow and hail and produced the third lowest amount of solar power from our roof top panels since they were installed. Luckily, April has brought far more pleasant weather so far.

March 2023 was one of the darkest ever and even the extra panels didn't bring our total for the month to a total which was as high as the average over the ten previous years

The effect of panels facing in different directions

The extra panels on the garage face are installed facing directly south while those on the top of the house face south-west as that's how our house is built. This means that the sun hits the extra panels on the garage earlier than those on top of the house and that we have significantly more solar power earlier in the day now than was the case when we only had the panels on the top of the house.

Proportion of theoretical maximum output achieved by the solar panels on our house roof and those on the garage roof on the day of writing. Having panels facing in different directions flattens out the production curve meaning that we can cover our own usage for a larger proportion of the day.

Early in the morning all our solar panels are in shade, only receiving indirect light. The output of the panels on the garage suddenly come out of the shade of our neighbour's home at about 9:15, giving a rapid rise in output, today seen as a rise from from 5% to 22% of their potential. On the other hand, the panels on the roof of the house don't see a sharp rise due to an obvious shadow, but because of the angle of the roof they don't reach 22% of their potential on the same day until more than an hour later, around 10:30. This difference means that while on a day like this the output of the roof top system alone wouldn't reach 1 kW until nearly 10:45, adding two extra panels on the garage have brought that forward by more than half an hour.

Our garage roof at just after 09:00 this morning. These panels are at a 45 degree angle because that means they face directly toward the south. The sharp shadow line is due to our neighbour's home. The sun has melted the ice off of most of one panel and output is increasing rapidly as the panels receive direct sunlight. When we install two extra panels these two will be pulled back by about half the width of a panel and the two new panels will see the sun slightly earlier each morning than these do.

Doubling the size of the installation on the garage should mean on a day like this we can reach an output level of 1 kW by about 9:45 and 2 kW by just after 10:30. As such, two extra panels will address a source of slight annoyance - ever since the roof top system was installed we've observed that turning on appliances like our washing machine in the morning meant that we drew energy predominantly from the grid instead of from our solar panels, but with four panels facing south on the garage to take up the slack while the larger array on the roof "wakes up" this will no longer be the case - at least in summer.

No more gas so we will probably need more electricity than before

Our gas supply is being removed next week. We've already not used it for some time. In the future we'll probably need a bit more electricity than now so extra capacity is of course helpful.

Effect on a possible future battery installation

If we install a battery in the future, which we are considering in the future, it will have less to do because we will already have improved our autonomy by covering more of our morning electricity usage directly with solar power, thus reducing stress on a battery as it won't have to cover such a large proportion of our energy usage during mornings. I had hoped to have figures for the year so far showing improved autonomy compared with last year, but due to the very dark winter it hasn't been possible to produce those, so that's something for a future blog post.

Tuesday, 21 March 2023

Having the gas disconnected

Having the gas connection removed from a home in the Netherlands costs €869, except that it's subsidized at the moment so costs nothing at all. What better time can there be to remove fossil fuels from your home ? Our gas supply will be cut off in a few weeks time.

It's taken us a bit longer than I'd hoped to get to this point but in a few days our gas supply will finally be cut off. We stopped cooking with gas many years ago, but we still had gas central heating and a gas hot water heater for our shower. It was the latter which stood in the way of getting rid of gas altogether as having no hot water in our bathroom at all, especially over winter, was not at all appealing. However we installed an electric water heater last month which then meant we no longer had a good reason to still have a gas supply to our home.

How much gas, how much CO2 ?
For some odd reason our energy company decided that our annual summary of energy usage should be over a period of February 23rd 2022 to March 11th 2023 this year. That's two weeks longer than a year and includes more of the cold days. The summary shows that we consumed 540 m3 of gas. That's considered to be quite low, but it's still a lot. 540 m3 of gas emits almost a whole ton of CO2 when it's burnt (multiply cubic metres of gas by a factor of 1.78 to find how many kg of CO2 are produced), and that's something that we really do not want to do.

An absurdly over-sized boiler

In February we used 48 m3 of gas, about a third of an average
apartment or under a fifth of an average "2 onder 1 kap" (semi-
detached) home similar to ours.
This morning I worked out that the water heater which we removed last month actually accounted for slightly more than half of our total gas consumption for the year. Subtracting the equivalent of 12 summer months (when the central heating is turned completely off) from the entire years gas consumption suggests that only about 245 m3 of gas was used by the central heating boiler last year.

Burning 245 m3 of Dutch gas (at 33.32 MJ/Sm3) releases about 8163 MJ or 2270 kWh of energy. Our gas heating boiler is a Radson EHRE 240 from 1993 with a rated output of 28 kW. It's been obvious for years that it was grossly over-sized - I had to take action a couple of years ago to make it shut down sooner to stop us from getting too hot - but it wasn't until now that I calculated how absurdly powerful it was. A 28 kW output with consumption of 245 m3 of gas suggests that over the whole year this thing only actually operated for the equivalent of about 5 minutes at full power.

The beast awaiting removal
Because we put a lot of effort into insulating our home, we can now make our living room and dining room (i.e. most of the ground floor of our home) heat up slowly with nothing more than a 400 W IR electric heater even on very cold days. Clearly we don't need anything like 28 kW !

The boiler dates from before condensing boilers were common-place. Its rated efficiency is 83%. It also doesn't have a balanced flue but instead takes air from the boiler room in which it sits (getting rid of it means we can insulate that room properly and gain a small storage room on the top floor) and as the heated water we receive from it on the ground floor has travelled two floors down to reach our living room and slowly gurgle around the radiators we clearly don't get the benefit of much of the 2270 kWh of energy released by the gas as heat in our living room.

So what now ?
We have decisions to make. Even a few small resistive electric heaters switched on when we're near them would be a more efficient way to hear our home. A friend of ours has reported good results from using an air conditioning unit to heat his living room this winter, and that's definitely more efficient than a resistive heater, but it does make a bit of noise. We will also need some heat upstairs, in the bathroom, bedrooms, work room etc. We've also been working on improving ventilation in our home so fitting a ventilation system with heat exchanger where the old boiler used to sit on the top floor would probably be beneficial. We have decisions to make over the coming months: By December it'll be cold again. 

Hoping to reduce our energy bill further
Last year a quarter of the total gas bill of €1051 was the connection charge. This year our gas bill will be much lower but it won't be zero as we'll still have to pay the connection charge for however long it takes to be disconnected. While gas cost us €1051 last year, our total energy bill for the year was only €587 once we took off the amount that the energy company paid us for nearly 900 kWh of excess electricity that we generated with our solar panels, as well as various other compensations and apparently random things that I've never understood which always appear on energy bills.

Anyway, the energy company decided that we had overpaid by €180 so they're sending us money, which is of course welcome. Then they set our monthly payments this year to be a bit higher than they were last year, which doesn't seem very logical under the circumstances, but they did this last year as well so I'll again have to argue it down this year.

We already added two extra solar panels at the end of last year to roughly cover the water heater's consumption and our plan now is to add a couple more panels again which should leave us with about 1600 kWh per year free compared with last year which we can use for heating. Hopefully that will be about enough. If we end up generating about as much extra electricity as the heating consumes, then not only will we no longer have any fossil fuels in our home but our bills should also be well on the way to zero.

Of course it's impossible to work out exactly what anything will cost because energy bills are absurdly complicated. While we work out how to reduce our energy consumption and CO2 output, perhaps the energy company can put some effort into making their bills understandable.

Job completed earlier than expected

Update 11th April: Our gas supply was removed this morning. Two gentlemen turned up with a digger and made a huge hole in the front garden, removed the supply pipe and the meter from indoors, and then they made everything neat again. So that's it - we no longer have any fossil fuel to burn.

In other news, I took delivery of two more solar panels a couple of days ago. So in a little while I'll write something more about our solar power system.

Wednesday, 8 February 2023

Electric water heating - finally got rid of the pilot light !

There's nothing much more boring than a photo of a cylindrical water heater hanging on the wall, but there it is boringly getting on with its job, heating the water for our shower and bathroom using solar power from our roof and our showers definitely don't mean burning gas any more !

Over three years have passed since I calculated how much gas the pilot light in our water heating system was consuming. It was a bit frightening. 134 cubic metres a year, That means the pilot light wasted almost twice as much gas each year as we just used for heating our home for the whole of January. What's more, 134 m3 at the current price of around €1.80 per m3 works out as about €240, which due to everything else we've already done to reduce our energy consumption is about half of our total annual energy bill for electric and gas combined (we've paid €40 a month for the last year, and the energy company currently owes us money). It's been at the back of my mind literally since I first made that calculation that I had to do something about it, but there are always other things to do and it took until this week until it happened.

Of course I went through all options, including such things as heat pump water heaters. These appear to only be available in absurdly huge sizes meaning more waste, with costs that are simply too high, and with unknown reliability compared with a simple resistive heater. I also considered complete heating systems including water, but most of the year we unplug our heating system so this seemed less than optimal. Eventually I decided that a simple hot water tank, was the best option so long as it could be well insulated and with some kind of control to stop it wasting energy when we didn't need the hot water.

I should have been able to write this last year. I ordered a water heater in September which got delayed due to covid and then didn't turn up at all. After sitting on a waiting list for several months I eventually asked the company I'd ordered it from for a refund which they sent promptly, so I can't really complain about that. Anyway, I then ordered another type which arrived less than 48 hours after I'd ordered it. It's supposed to be a "DAT Arca 80 litre anti-kalk" (anti calcium) boiler, but for some reason what turned up has "GOT" written on it instead. Before ordering I tried to work out whether I'd be able to buy spare parts, and it seems I can. Not that there's much in this thing to go wrong.

Between the two orders I did a bit of extra research which led me to prioritize buying a boiler with a dry heating element which should last longer.

Smart vs dumb boilers

Some boilers are "smart". The main reason why smart boilers are claimed to use less electricity every year than the boilers with dumb controllers is simply that the dumb boilers are typically switched on 24 hours a day, consuming electricity to make warm water when no-one will use it. Smart boilers include such features as analysing your use for the first week and then only warming water when it thinks you'll need it. That's not a bad idea, but we don't really have a fixed weekly pattern of use so I'd have had to use it as a time switch instead.

At the moment the controller consists of a simple analogue clock style time switch and I've also got an energy meter connected up to let me measure electrical consumption over time.

I have no interest in any "smart" IoT product as connecting things like this to the internet means yet another thing to worry about with potential spyware and software updates (if they happen at all they'll be phased out before the lifespan of the product) so I never had any intention of connecting the boiler to the internet. However the company who made the first product only sold the model of their boilers which had thick insulation alongside the smart controller so that forced the issue. Luckily I found an alternative product that combined 30 mm of polyurethane insulation with a simple dumb thermostat. Perfect for us. I think I would have ended up using the smart controller as nothing more than a time switch anyway, and a cheap analogue time switch for then €5 does the same job.

Matching consumption to available solar power

I also found that some companies were offering "anti-salderings" boilers at extra cost. These come with lower power elements than usual as a better match to domestic solar power installations.

Underneath the easily removed plastic base of the boiler is this mess of wires. Disconnecting the two white wires from the second element halves the energy consumption, making it more compatible with using excess solar power.

The idea of this is to ensure that to the greatest extent possible you only use your own electricity. This is because Dutch energy companies don't give you very much for any extra kWh that you export to the grid, and no-one is quite sure what will happen in the future to the existing rules around this. So when I found it was possible to buy a 1500 W boiler which actually has two 750 W elements wired in parallel, that's what I chose because this can also be run as a 750 W boiler which happens to come with a free spare element. The company that we bought our boiler from also offers an anti-salderings version of the same boiler for €50 more. Does this differ in any way other than only having one element wired up ? I don't know.


The size of the boiler was a topic of much discussion. I'd have been happy with a 30 l boiler, but my wife insisted on 80 l.

The biggest problem with buying a fairly large boiler was the weight. This thing weighs 32 kg. Holding up there above my head over the stairs while Judy helped push it into place to hook it onto the supports that I'd already fitted in the wall took a lot of effort. The bathroom is just behind the wall on the right. This was the closest place to the bathroom where we could install the water heater. This means less loss due to long pipes than was the case with the gas water heater. As you can see, I'd not yet done the plumbing or electrical work when this photo was taken.

I'm almost totally bald while Judy has long hair so it's no surprise that she thought a larger boiler would be necessary. I've done calculations which I think reliably indicate that 50 litres would be more enough for Judy, but as we're grandparents now we might actually need to run a bath for our favourite visitor at some point and that could mean needing more water. The extra large boiler will cost a bit of extra energy, but we can compensate by running it slightly cooler and letting the shower mix in less cold water. But in any case we should have solar power to spare - I expanded the solar installation in September when I ordered the first water boiler specifically in order to cope with this.

Tidying up

The water pipes to the gas heater have been removed but the heater is still in place in the boiler room alongside the central heating boiler (which doesn't get used much, but . I'll get rid of it when the gas central heating boiler is removed, a job which I will probably have to get someone else to do so they can do both at once. Until that day it's doing us no harm and it's perfectly safe - the gas pipe the gas boiler has a tap on it which which is now switched off.

How much energy does it use ?

After three weeks of operation, with us having showers as frequently as usual, the water heater had consumed 44 kWh of electricity. That works out as an expected consumption of about 770 kWh per year to cover all our hot water usage, which would cost about €300 at today's electricity prices. By comparison, the consumption of our old gas water heater's pilot light was 134 m3 per year. At today's price that amount of gas would cost over €400 per year, and remember that that was just for the pilot light. i.e. it didn't include the gas used for actually making hot water that we washed with. So all else being equal, replacing the gas water heater with electric would save us about €10 a month. i.e. it would take about three years before the new water heater has paid for itself in reduced cost.

We expect these extra solar panels installed in September to
generate about the same amount of electricity as the water heater uses
But all else isn't equal: The extra 800 W of additional solar panels which we added to our rooftop system a few months ago should generate approximately the same amount of energy each year as the water heater consumes. As a result, our annual energy cost should just drop by the price of the gas that the water heater burnt, which worked out as about €40 a month. That's quite a significant number for us because €40 a month just happens to be exactly the  same amount as we've paid for our electricity and gas together over the last year.

So as we stand right now our energy bills ought to be very close to zero in future even if we do nothing more to improve efficiency of our home. But that's not the plan. We will of course continue to do more to make our home more efficient, and there will be more blog posts about it.

Why not install solar thermal water heating ?

A perfectly reasonable question, which someone asked on social media. My answer is as follows:

In total the panels, the boiler and all the parts needed to install everything cost less than €1400. It would have cost at least twice as much to install a thermal solar water heater. Also, we'd still have needed to buy the  electric boiler (a more expensive version of it with pipes as well as electric heating) because if we'd gone with solar thermal that would almost certainly not heat the water sufficiently in winter. By doing it this way, all the solar panels on our house & garage combined can contribute to water heating, not just a smaller area so it's likely to work better on darker days.

In addition, the extra solar panels are on the garage roof were easily to reach safely at a low work height while thermal solar panels would have had to be installed on the much higher roof of our home. So in addition to this being a cheaper way of heating water than thermal solar, I also did not have to clamber about on the roof of my house (nor pay anyone to do that dangerous job for me), didn't have to make holes in the roof for pipes which could leak, and there's no risk at all of leakage due to pipes being frozen in winter.

And think of future maintenance. The water heater and solar panels function completely separately from each other. i.e. either can be replaced without affecting the other component of the system.

I don't think that thermal solar makes much sense these days. It did in the past when PV panels were far more expensive than they are now. My father-in-law made his own solar water heating panels in the 1980s. This was an interesting project, they were made of copper sheeting with copper pipes soldered on, all painted black, in an insulated wooden box with glass in front. They were very effective and I enjoyed a few nice warm showers from that system in the summer. But it worked out in large part because they built a home around the system so the panels could be larger than commercial systems and ideally located to work with gravity. Around the same time I was experimenting with my first solar electric panels on my roof, but they produced very little electricity for their size and cost and it would have been completely impractical to use them for heating water. For many years I thought we'd end up with solar thermal water heating, but they were always difficult to install on a standard home, and this is now a better way of doing it.

Anyway, that's another DIY job finished, and we've taken another step in the direction of complete independence from fossil fuel.