René Verboeket

At the end of last year Solinq installed solar panels on my roof. Now, one year later, this is a great opportunity to take stock and see whether or not the intended yield has been achieved.

 A step back in time

On 5 December 2008, 14 solar panels with a capacity of 235 Wp were installed on my roof facing ESE. This brings the total capacity up to 3290 Wp. At the end of the day (it was already dark), the system was connected to the grid and as such was operational. On 6 December our first solar electricity was generated.
 

Expectation

Because the roof orientation is not ideal (124° in relation to the north) and one of the chimneys casts a shadow on the solar panels from 14.00 hours onwards, the yield is not optimal. The orientation at 124° in combination with a pitch of 29° has resulted in a yield loss of 11%. The shading caused by the chimney adds a further yield loss of 6%. This implies that the yield from my solar panels is "only" 83.7% of the ideal situation. In the ideal situation (an orientation of 185° and a pitch of 36°) the yield in kWh would be: 0.85 x 3290 = 2797 kWh. This means that I can expect a yield of 0.837 x 2797 = 2341 kWh per year.

One year later
One year later and I can declare that my expectations were very pessimistic. On 5 December 2009 at 5.00 PM the counter was on 3019 kWh! So 29% above the expected yield. Of course 2009 was an exceptionally good year with a lot of sunshine, but the difference is huge. This means that my payback period is now shorter! With the grant included, my yields this year amount to €1660.

A clear overview of the figures: 

• On 20 July the highest peak power of 3046 Watt was reached;
• There were actually six months in which the highest peak power was more than 2900Wp (April, May, June, July, August, September);
• On 24 June the highest daily yield of 21.27 kWh was achieved;
• May was the month with the highest yield of 438kWh;
• In May, June, July and August a yield of more than 400kWh was achieved;
• The yield of the first year was 3019kWh.

Maintenance
It is often said that solar panels should be cleaned regularly, as otherwise the yield drops considerably. I have never cleaned my solar panels, but on 2 December 2009 I reached a peak power of 1660W, whereas the highest peak power in December 2008 was achieved on 7 December (two days after the installation!). At 1445W, this peak was much lower than it was a year later. It would seem that the panels mounted on my roof do not need to be cleaned. According to Ivo Kusmic this is because of the special glass that is used for the SOLON panels. This glass is easily cleaned when it rains.

Providing all your own electricity needs
In the same period that the solar panels supplied 3019 kWh of electricity, I used 2914 kWh of electricity (if you don't use the tumble dryer, your power consumption drops dramatically!). This means that in the first year I was able to meet my own electricity needs, and I even had a surplus of 104 kWh!

In 2010 my house was refurbished and the two chimneys demolished (this saves a further 6%). Two more solar panels fitted perfectly in the empty spaces, which has allowed me to expand the system to 3760 Wp.