Best Solar Output So Far - Today Breaks 20kWh Barrier

With a reasonable breeze today and slightly lower temperatures we have broken the 20kWh for the first time and got a new record for the electricity generated. By the time the sun set today we had generated 20.6kWh which is a full 1kWh more than the previous record set at the beginning of April. As per my blog post yesterday about the effect of temperature on solar panel electricity generation the cooler day as well as the breeze look to have contributed.

I think at 20kWh we are now getting very close to the maximum electricity that can be generated in the UK from 3kWp solar panels. I'm hoping we can hit the 21kWh target which would mean each 1kWp of panels had generated 7kWh which seems to be the maximum possible for us.

Maximum solar panel electricity output in UK

How does Temperature Affect Electricity Generated by Solar PV Panels?

How much variation does temperature cause for generating electricity from Solar PV Panels?

With one of the hottest days in the UK so far this year it is interesting to compare the output for a hot sunny day with a cooler sunny day earlier in the year.

The best generating day in April was 19kWh for a clear sunny day with temperature of 12C. Yesterday generated 17kWh for a clear sunny day with a temperature of 27C despite the longer generating time with the lengthening days.

Solar panel output with different temperatures.

As you can see the output was for longer on the blue day (24 May) but the peak was lower than on the green day (2 April) as the temperature was far lower. The equation is the temperature coefficient which for our panels is 0.5% meaning output drops by 0.5% per degree over 25C. So for panels at 35C which is 10 degrees higher the output would be 5% lower.

As another comparison the maximum peak generation was around 2.3kW yesterday but for cooler days this has been as high as 2.5kW and for cloudy days with sunny spells it has peaked as high as 3kW showing the effect that temperature has on solar power generation.

One company was selling a hybrid solar panel that included water heating as well as electricity generation. As a method for cooling the solar panels to improve their efficiency it seems like an effective method based on this data as the water will extract the heat that can then be used for hot water in the house.

Solar panel generation in high temperatures

May Solar Generation Falls Short: Disappointing Solar Panel performance in May

We are now half way through the month and so far the electricity generated by our solar panels has been disappointing with the poor weather to blame. At the current rate May will be the first month when solar electricity generated has fallen well below target.

May solar panel performance lags behind target

Our record peak electricity generated remains the 1st April when you would actually expect the lengthening days to 22 June to break records consistently. The failure to reach new peaks shows the lack of clear sunny days and the number of rainy days since the hosepipe ban was introduced. Although the sun has shone at different times over the last 6 weeks we have not had a single day when the sun has been out all day with clear blue skies.

How does the Feed in Tariff (FITs) work?

The UK Feed in Tariff was modelled on one introduced in Germany and implemented in the UK from 2010. It pays households that have invested in solar PV power systems a set rate for every kilowatt hour of electricity that they generate as well as a payment for all electricity that they export to the national grid. The export payment is current calculated as "deemed" until smart meters are widely used across the UK. The deemed rate is assumed to be 50% of the electricity generated so if you can use a larger proportion at home then you will still be paid for it. As the export rate is much lower than the FiT rate this won't be a massive saving.

Feed in tariff details in the UK for your solar panels

Depending on your viewpoint the Feed in tariff has either been a huge success leading to large numbers of solar installations to help our CO2 reduction targets and massively cutting the price of solar power or an expensive scheme that has been abused by large players to make money at the expense of all consumers who effectively pay for FITs through a levy on electricity bills.

What is not in dispute is the drop in the costs of installation since 2010. It was common for a 4kWp solar pv system to cost up to £20,000 at the time and as of May 2012 this can cost as little as £7000 now. Putting the cuts in the feed in tariff in context these current prices still give a better return than the original rate with the higher prices.

Impressive PV Solar Generation Despite Wettest April for 100 Years

April 2012 has been officially recorded as the wettest for over 100 years with rain virtually every day. Our weather station shows a huge 137mm of rain fell during the month compared to 20mm in March 2012. Despite this huge variation we actually generated more electricity from our PV solar panels than in March and were still above the SAP target. March generation was 310 kWh and April had the impressive result of 320kWh despite the rain so we can only imagine how good generation numbers would be with sunny weather.

The April figure of 320 kWh compares to a SAP 2009 estimate of 294kWh and PV-GIS of 330 kWh so is very close to the target. During the month we had some new records for solar electricity generation set with the highest 5 minute average electricity generation at 3.012kW as a result of the intermittent cloud cooling the panels. An output of 3.012kW from 3.01kWp PV solar panels must be about the maximum possible. I guess this was above the rated kWp figures as they are measured at 25C and this month the temperature has been nearer the 10C range. Lower temperatures improve solar power generation as can be seen by the peak generation just after clouds cool the solar panels.

Two New Records - and a Pigeon Nest!

Today the solar panels have passed a landmark and set a new peak production record. We have now generated over 1MWh (1000kWh) of electricity which seems incredible in 5 months that cover the worst winter period. Based on the current generation amounts it seems feasible that we could generate double this over the next 7 months. 3000kWh  from 3kWp panels would be an excellent result and give even faster payback on the panels.

We have also hit a new peak generation record today with 3.012kW being recorded at 1310 today. As today has been such a mix of sun and cloud it seems that the cooling effect of the clouds allows the generation to jump to the maximum when the sun comes back out again. It seems slightly strange that the peak recorded is above the nominal output of the inverter which is rated at 3000W.

Peak solar panel output and pigeon nests

Finally we discovered that a pigeon had decided the space under the panels would be perfect to start to build a nest. Sadly we disagreed on this and the pigeon will have to look elsewhere as sticks taped together and access to the panels via the velux window were enough to dislodge the sticks from beneath the panels. Having the velux window in the middle of the panels has proved to be very useful!

Maximum Solar PV Power Output Achieved!

Today has been a complete mixture of weather from bright sunny spells to cloud and rain with thunder and lightning. Overall the solar panel power output hasn't been fantastic but the mix of cloud and sun has meant that we have achieved the maximum possible output from our solar panels today.

Solar PV panel peak outputs

Our panels are rated at 3010W potential (Wp or 3.01 kWp) meaning that the theoretical maximum peak output that could be obtained would be 3010W.

What is the maximum output of solar panels connected to a Sunny Boy HF3000 Inverter?

 Our panels are linked to a Sunny Boy HF3000 inverter which therefore limits the maximum power output to 3000W. This was achieved at 1230 today just after a cloudy sky had given way to sunshine. The solar panel output soon dropped as the panels warmed up but it shows that the maximum PV output from the inverter can be achieved.