Our solar PV installation – a year on…

Following on from the previous short post about our experiences of a new Ground Source Heat Pump system a year after its installation, here’s an even shorter post about how our solar PV array has performed a year on from when it was installed.

(For earlier posts about our solar PV installation, read these…)

Our installation comprises of 20 x Linuo 195Wp monocrystalline PV panels mounted on Schüco Lite rails connecting to an SMA SunnyBoy SB4000TL-20 inverter. The installation was specified, supplied and fitted by the excellent Greenday Renewables based at Fort Dunlop, Birmingham.

The original estimate for the total annual output of our installation, based on historical local climate and meteorological data, was 3,560 kWh. Our actual output for the first year has been 3,585 kWh which I’m pleased with given how much poor weather we’ve had this year.

As we managed to secure the higher Feed in Tariff (FiT) rate of 43.4p/kWh at installation time (which increases every year as it is index linked) we have generated an income of around £1,700 for this first year, plus any additional savings from not having to import as much electricity by using our own generated electricity as much as possible. Based on these figures the system should have paid for itself within 5 years.

Being a true geek, one of the first things I did after the system was installed was to set up some automated logging and reporting of data acquired from the inverter by connecting to its bluetooth interface. This data logging solution has evolved over time but is now implemented using the open source sma-bluetooth project running on a Raspberry Pi single board computer with a USB bluetooth adapter, storing captured data in a MySQL database and producing real-time web accessible charts using PHP and the excellent Highcharts library.

I look forward to reporting on how the system has performed after it’s second anniversary!

More solar PV goodness

A couple of days after posting about the latest record day from my solar PV installation, the record was broken again! A new record of 26.69 kWh for the day.

In fact, the last 6 days have all produced over 22 kWh for the day.

And finally, another comment on the performance of my ground source heat pump. With the recent hot weather the heat pump has been on an average of only 1 hour a day – in fact yesterday it didn’t come on at all! All helping to save me money 🙂

A new solar PV record day

Today our solar PV installation generated 25.07kWh of electricity, a new record beating the previous high of 21.69kWh.

This is what the graph from my automated data logging looks like:

As you can see there was unbroken sunshine all day although it only peaked up to around 3.1kW which reduced the overall output for the day. We’ve seen the system peak at over 4kW so I hope as we get later into the year we will see higher daily totals due to the higher peak output.

[ An interesting side note to this – our ground source heat pump was only on for 4 hours today, whereas during colder weather we can expect it to be on around 10 hours a day. I assume this is because of the high temperatures during the day and the obvious much reduced demand for heat. Let’s hope this this is a good indication of typical behaviour during the Summer months. ]

Our best solar PV generation day so far

It’s been a glorious early Spring day today with continuous sunshine from dawn til dusk, and as a result it’s also been our highest solar PV generation day since the system was installed just over a month ago. You can see this from the chart produced by my automated data gathering and chart generation tool running on my Linux server:

As you can see we generated a total of 20.81 kWh of electricity throughout the day, peaking at an output of 3.17 kW at around 1:30pm. With the feed-in tariff (FiT) rate now confirmed as 43.3p/kWh for our installation and a deemed export rate of 50% of generation at 3.1p/kWh, this makes a total daily income of £9.27. That doesn’t include any savings on electricity that we were able to use ourself during that period instead of having to import it from the grid.

Although it’s still early days for our system and we are only just into Spring, things are looking promising for meeting or exceeding the estimated output for the system over the next year.

Automated solar PV stats

Following on from previous posts about our new solar PV installation, I have now implemented an automated process which pulls stats from the SMA SunnyBoy 4000TL bluetooth-enabled inverter, stores the stats in a MySQL database and then makes a daily chart available showing solar PV generation, looking something like this:

In a little bit more detail…

  • Everything is hosted on my Debian Linux server.
  • I use the excellent open source sma-bluetooth package (http://code.google.com/p/sma-bluetooth/) and the bluez-tools package to connect to my inverter via bluetooth. The smatool program within this package stores the data it downloads in a simple MySQL database.
  • I have a cron job which runs this data extraction every 5 minutes.
  • I then wrote a simple PHP script which uses the excellent pChart 2 library (http://www.pchart.net/) to generate a daily output chart which is hosted on my personal web server.

So, I can now keep track of how much electricity I am generating wherever I happen to be!

Solar PV update

Our solar PV array has been installed for a few days now so I thought I’d post an update with a few more details now that we’ve had some time to get to know it.

The PV panel array itself isn’t actually as large as I had originally imagined. It consists of 20 x LINUO 195Wp panels mounted onto Schüco Lite rails, but they are slightly smaller than some other panels and so don’t take up as much space. Here are pictures of the roof before…

and after…

I’m very pleased that we were able to install the internal components – inverter, generation meter and isolator switches – in the service cupboard next to our secondary electrical distribution board and heat pump / cylinder as it makes for a tidy and hidden installation.

In the pictures below you can see the inverter (the big red and black box) with the two DC rotary isolator switches below it to the left, and then the AC rotary isolator and generation meter below it to the right.

The inverter that we have is an SMA SunnyBoy 4000TL-20 and this features a bluetooth link as standard allowing various performance stats and configuration to be accessed remotely. I’ve downloaded the free Sunny Explorer software from the SMA web site and monitored performance over the last few days. Here’s the generation graph from yesterday so you can see it’s peaking around 3kW output – I don’t think that’s too bad for a late Winter’s day. It’s also quite addictive (I guess until the novelty wears off!) monitoring the performance throughout the day, praying for the sun to come out!

While the Sunny Explorer software is useful and easy to use, I am very keen on writing my own tools to extract this information from the inverter so that I can do more with the data in a more automated way. I’ve already started playing with some open source Java libraries for interfacing with SMA inverters via bluetooth so hopefully I’ll have something up and running soon. At some point I’d also like to look into an interface into our IVT Greenline HT+ heat pump so I can do a similar thing with that.

We now have solar PV

In the space of 6 months we’ve gone from having nothing to do with renewable energy to now having a ground source heat pump providing hot water and heating for our house, and as of today a solar photovoltaic (PV) array generating electricity for our consumption and export of any surplus back to the grid.

Our solar PV installation consists of an array of 20 LINUO 195W (peak) monocrystalline silicon panels arranged in landscape orientation on our 30° pitch South facing roof feeding back into an SMA SunnyBoy 4000TL inverter. It is rated at 3.9kWh peak and has an estimated annual output of 3,560kWh.

The supply and installation was carried out very efficiently and professionally by Greenday Renewables based at Fort Dunlop, Birmingham. Thanks to them for managing to get the installation completed before the 3rd March cut-off for reduced Feed in Tariff rates.

Within a few minutes of the installation being completed and the inverter powered up, it was generating electricity at a peak of 2.5kWh! Almost exactly on cue, after a day and half of dark skies, wind and rain, the sun came out and shone brightly 🙂