First year figures

Having finally had a chance to sit down and do some calculations on our first year with solar power, the figures are quite interesting.

Based on our use over the previous two years our average annual electricity consumption was 4320 kWh. Our first years solar generation was 4047 kWh which is around 93.5% of our average usage. This is much better than we expected, we had hoped for 75-80%. It seems that with a bit more effort to improve efficiency and reduce waste we could get very close to 100%.

The electricity consumption figures for the first full year with solar show that we used 2720 kWh. This is around 63% of the average for the previous two years and gave us a saving of around 1600 kWh. This works out at around £190 saving on our annual electricity bill at current prices. Adding this to the income from the FIT we made a net return of around 14% on the installation cost. This means the pay back time will be just over 7 years.

Overall this is on the high side of our expectations and we are very pleased with it. Given the very indifferent summer we had in 2012 it will be interesting to see how the system performs in future years. The majority of the electricity the system generates is in the 6 months between April and September. If we have a better summer then the likelihood is that the annual generation will exceed this years figure and take us close to the 100% mark for generation vs consumption.

Our first year of Solar

We have just passed the one year mark since our solar PV system was installed so its a good time to report on how the system has performed. Before having solar PV installed I looked at various calculators and modelers to see what sort of yield we could expect. This allowed us to calculate the expected return on our outlay and how long it would take to pay for itself. The EU has a calculator that uses satellite data to predict sunshine amounts for locations in the UK and most of  Europe which I used. This reported that our system should generate around 3640 kWh in a year. In fact we generated 4047 kWh in the year, around 11% above this figure which was very pleasing. This was despite the summer being rather poor.

This electricity generated equates to earnings from FIT revenue of around £1870. I have estimated that savings on our electricity bill will be at least £200, although the final figure could be quite a bit more. In total this gives us around £2075 which is just over 14% of our capital outlay. If the system continues to perform this well then we can expect it to pay off the capital cost in around 7 years.

There is a link to the EU solar PV modeler on my useful links page and there are also a number of other useful calculators included there. These are well worth a look if you are considering installing Solar PV as they give a reasonable idea of the likely returns possible. The cost of installing Solar PV systems has come down quite significantly in the last year so there are still opportunities to get a reasonable return if you have a suitable location.

It seems our solar panels have proved attractive to the local bird life as well as a family of pigeons seemed to have taken up residence on our roof over the summer. I need to get the ladder out and have a look when there is a suitable day. I doubt they will do any harm apart from blocking the gutters with nesting material but I will take a look to be sure.

Solar powered kiln update

Items that have just been glaze fired

We have used the kiln several times over the course of the summer for both bisque and glaze firing and have been very pleased with the results so far. The biggest challenge has been finding reliable sunny days to fire the kiln so we can stick to our green agenda. With careful timing of the firing it has been possible to have the main part of the firing (when the kiln runs at full power) happen when the solar panels are generating maximum power so that it runs entirely from solar power.

A typical glaze firing has been started at around 7:30am and the kiln runs at 180C/hour until it reaches 600C, usually around 10:45. At this point the kiln goes to full power until it reaches the target temperature which is 1240-1260C, it then holds this temperature for 10-20 minutes to allow the glaze to melt evenly. The firing usually completes some time between 1:30pm and 2pm. As our solar panels face south east we generate maximum power from mid morning to early afternoon which covers the maximum demand from the kiln nicely.

During the early part of the firing when the kiln is gradually warming up to 600C it uses a "duty cycle" which means the elements are turned on for a few seconds at a time. The kiln controller turns the elements on for long enough each minute to meet the meet the requested temperature rise needed, in this case 180C/hour. This is in fact quite gradual, much slower than a normal domestic oven. The down side is that when the elements are on they will draw full power (3kW) which is more than our solar panels will be generating at that time. However when you calculate the power used during this period it is small compared to the amount used in the second part of the firing when the kiln runs at 3kW for more than 3 hours continuously. Our solar panels gradually increase output during the first part of the firing so quit a lot of the energy required will still be supplied by the solar panels. Each firing is in practice costing is very little, just a few pence at most.

The challenge as we head into autumn is to find enough time to cover the kiln firing as the peak power from the panels gradually reduces from 3.6kW we get during the summer. Judging from the measurements I took last year the latest that we will have enough of a window to cover the main part of the kiln firing is probably around mid October. Our plan is to put the kiln somewhere dry for storage over the winter and not fire it again until the spring. At the moment the kiln is in the middle of the garage and we want to put the car in there during the winter months so that is another reason not to fire it during the winter.

We will be busy getting some more work through the kiln over the next few weeks whilst we can, I will post some more photos of work fired in the kiln soon.

Our first kiln firing

Well we finally managed to fire the kiln after waiting for a suitable sunny day, this was no easy thing with the poor weather we have been having this summer. Here are some photos of the work just after opening the kiln the next morning once it had cooled off. The models are my wife's work and the bowls and cups are mainly mine.

Pieces waiting to be removed from the kiln after firing

Pieces safely removed and ready for decoration / glazing

The day we chose turned out not to be quite as sunny as forecast! - well it is England in the summer so we shouldn't have expected unbroken sunshine :-) Despite this we only used about 50p of electricity whilst the kiln was being fired and some of this was down to boiling the kettle and running other household appliances so the actual cost of running the kiln was a bit less than 50p which was pleasing.

We have since done another couple of bisque firings with similar results, we are still waiting for the elusive sunny days of summer when we might fire the kiln for almost nothing!

The next firing will be a stoneware glaze firing which requires a higher temperature to be reached, 1240C rather than 950C. This will use more electricity as the kiln will need to run at full power for at least a couple of hours to reach 1240C and then this temperature needs to be held for a 20 minute "soak" to allow the glaze to melt evenly. I will report back on how this went, we are excited to see the first finished pieces that we made in our own kiln.

Solar powered ceramics

We have been doing ceramics evening classes for the last three years and had been considering getting a small kiln for some time so that we could fire work at home. We had been put off by both the start up cost and the potential running costs. Some research revealed that we could get a hobby kiln that would run from a standard household 13amp socket and had a peak rating of 3kW. I did some calculations about firing schedules and realised that on sunny days between April and September it would be possible to fire the kiln pretty much entirely from the solar power. It would need the kiln to be started first thing in the morning so that the peak load coincided with peak output of the solar panels. Our system generates more than 3.5kW during the middle of the day at this time of year (if it is sunny) which is more than enough.With the summer months coming up we decided to go for it and have now purchased the kiln below.

Our shiny new kiln !

The next step is to do a test firing of the kiln, the only problem is it hasn't stopped raining for the last three weeks and the few sunny days have been during the week.  I did give the kiln a very short run up to check that everything was in working order, the picture below shows the kiln controller in action.

The kiln controller during a short test

We are busy making some work so that we have something to fire once the test firing has been done. The test firing is recommended for the new kiln as the elements will burn off their protective coating and the kiln will have had a "burn in". The test firing involves heating the kiln up at  a rate of 150C/hour until it reaches a temperature of 600C at this point it will be heated up at full power until it reaches the target temperature of 1050C. The test firing should take around 6 hours so I am planning to start the kiln at around 8am one morning as soon as we get a suitable sunny day.

The longest firing we will are likely to need is when we glaze stoneware which requires a top temperature of 1240C, this requires an initial rate of 180c/hour until it reaches 500C and then at full power until the target temperature. This should take somewhere between 6 and 7 hours to complete so the 8am start should still be fine. I might have to start the kiln a little earlier when the days get shorter in late August and September.

I will post some more reports once we have had a chance to fire the kiln for real, this should be in the next couple of weeks. I am going to check how much power we draw from the grid during the firing by taking meter readings before and after the firing, hopefully it won't be much.

We need to work hard now to create some work to be fired but that is the fun bit !

Mystery sounds - solved ?

We had noticed that under certain conditions we would get some odd rattling sounds from the roof, this only started after the solar panels were installed so we knew it was something to do with them and was rather worrying as it seemed something was loose. The sounds only happened when there was a strong wind blowing from a south or south-east direction which is quite unusual so this has only happened about three times since the panels went up.

I contacted our supplier (EVO energy) after a stormy day in February when the sound was very apparent and they said they would send someone to inspect. The earliest day available was in early March so we booked that up and waited. I re-confirmed the appointment a few days before and they asked if we had scaffolding still up, we of course hadn't as the system had been up for nearly 6 months. The day before the inspection was due some contractors turned up an erected scaffolding, I was a bit surprised.

Scaffold goes up again !

On the day a team of three turned up first thing at 8am and took a good look at the installation. After about 30 mins one of them team came down and explained that the tiles and mountings were very secure and couldn't be the cause of the sound. They suspected that the cable runs were the cause as the slack cable had been laid on the tiles between the panels. I went up and took a look and it was easy to see how the loops of cable could be whipped up by the wind and hit the panels, mountings and tiles. A quick experiment flicking the loose cable against the panels was able to produce a metallic sound something like that we had heard - mystery solved maybe?

The team then removed the bottom row of tiles and cable tied all of the loose cable runs to the mounting rails so that they couldn't flap around any more. They were finished and on there way by around 9:30am. Only time will tell if this was the cause, we will listen carefully next time there is a strong south or south-easterly wind.

Having the scaffolding in place did allow me to take a close look at the condition of the panels and see if they needed cleaning. They were not that dirty but there was a thin film of grime from the damp winter months and some residue from bird droppings, we get rather a lot of resident seagulls in the winter ! I took a bucket of soapy water and a telescopic window cleaner with me and gave the panels a wipe over to see how much effect this would have. It did remove a fair bit of grime so I guess it will make some improvement, I am wondering how easy it will be to clean them without the scaffolding. We have a garage with a flat roof on that side of the house so access is quite easy and relatively safe so I will probably give them a wipe over a couple of times a year.

Panels still looked quite clean after 6 months in place

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Winter quarter savings

I have now had a chance to sit down and calculate how much energy we saved from our winter quarter electricity bill. The bills for this quarter over the last three years have been very similar averaging around 1240 units so any saving was going to be quite easy to see. The bill shows that our usage this year was just 780 units which is around 63% of the previous years - very impressive. This amounts to a saving of around £55 on our bill, I have already arranged for our monthly electricity payment to be reduced significantly on the basis of this.

We have made a very big effort to make use of the solar generated electricity, my wife has been doing everything possible to use power hungry devices during the daytime. We used to run the dishwasher in the evening or overnight but this and the laundry, vacuum cleaner are now used during the daytime. In the winter it has also been possible to use the electricity to cook meals during the daytime. Stews and casseroles need cooking slowly over a few hours so they are excellent to cook during the day and then warm up for dinner.

The longer days will give us even more opportunity to make use of our own electricity. I am looking forward with interest on how the system will perform during the summer months. We had the system installed at the autumn equinox so we have only seen how it works on the shorter winter days, the next 6 months will show us just what the system is capable of.