Solar Generation Stats and wind measurements - January to March

We have a 2kW 8 panel solar array (Panasonic HIT panels), mounted on a south-facing roof at approximately 35-40° angle from the horizontal, which was installed at the end of August 2013.

These are the results for January, February and March 2016 (in red) with last year's results (purple), year before (green) and distribution by average sunlight 1971-2010 (met office stats) in blue:

The totals for the months are:

January 31kWh (last year was 51kWh)

February 111kWh (last year was 92kWh)

March 173kWh (last year was 176kWh)

Averages:

WIND SPEED MEASUREMENTS:

I've discontinued the wind speed measurements - even over the windiest quarter of the year, the wind speeds at 5m height are not sufficient to recommend a cost-effective turbine installation. 

Investigations currently ongoing into wind capture at 10m, and/or cheaper turbines (thereby allowing breakeven at a lower wind-speed).

Solar Generation Stats and wind measurements - December

We have a 2kW 8 panel solar array (Panasonic HIT panels), mounted on a south-facing roof at approximately 35-40° angle from the horizontal, which was installed at the end of August 2013.

These are the results for November 2015 (in red) with last year's results (purple), year before (green) and distribution by average sunlight 1971-2010 (met office stats) in blue:

The panels have done 21kWh this month - down 9kWh on last year's results.

With 248 hours of daylight in November (sun up to sun down for all 30 days), the average kWh generated per hour of daylight this month was 0.08kW. 

In September, I started monitoring the average wind speeds across my back garden to see if a wind turbine would be a financially viable investment.

Here is a graph showing December's wind speeds:

Average wind speed for the month was 2.7m/s.  

Average gust speed for the month was 4.4m/s.

Maximum wind speed recorded for the month was 9.2m/s. 

Maximum gust speed was 13.9m/s.

Solar Generation Stats and wind measurements - November

We have a 2kW 8 panel solar array (Panasonic HIT panels), mounted on a south-facing roof at approximately 35-40° angle from the horizontal, which was installed at the end of August 2013.

These are the results for November 2015 (in red) with last year's results (purple), year before (green) and distribution by average sunlight 1971-2010 (met office stats) in blue:

The panels have done 27kWh this month - down 32kWh on last year's results, and down 50kWh on the forecast by average sunlight. 

With 300 hours of daylight in November (sun up to sun down for all 30 days), the average kWh generated per hour of daylight this month was 0.09kW. October last year was 0.19kW.  A particularly gloomy November this year.

In September, I started monitoring the average wind speeds across my back garden to see if a wind turbine would be a financially viable investment.

Here is a graph showing November's wind speeds:

Average wind speed for the month was 2.58m/s.  

Average gust speed for the month was 4.26m/s.

Maximum wind speed recorded for the month was 10.2m/s. 

Maximum gust speed was 16.3m/s.

As usual, November was quite blustery, yet the average wind speed values recorded are disappointing. The average gust speed for the month is still less than the 5m/s ideal minimum recommended value I've been reading for cost-effective generation.  

However, there is no doubt that a turbine would have been productive for a significant percentage of the month.   I've done a bit of digging and have found the transfer function for the EOLO 1000 turbine I'm looking at (ie, how many W are generated at a particular wind speed):

 

Next I will find out how to plug these curves into my actual raw data in excel to arrive at a (hopefully reasonably accurate) prediction for kWh generated.  

Here is a pic of the E1K EOLO 1000 turbine I've been considering:

http://www.lmagency.biz/contents/en-uk/p58.html

With all the grid-connection kit, and the 6-blade upgrade (as shown), it costs a total of 924 euros + 66 euros shipping = 990 euros - approx £670.  If I do installation myself, that would cost a couple of hundred quid (foundations and mast), so the whole shebang goes in for under a grand.  Note it has "1k" and "1000" in it's title, but look at the transfer function - it only hits 1kW at 24m/s - that's a 53mph wind!  At a more realistic 5m/s it's only doing 120W, and it hits 200W at 6m/s.
This is why looking at the number in the title for any given turbine is a waste of time. Another turbine I'm looking at, the Aeolos V-600 turbine generates 200W at 5m/s http://www.windturbinestar.com/600wv-v-aeolos-wind-turbine.html

Transfer function - pdf here:

http://www.cheso.ro/eoliene/turbine-eoliene-verticale-aeolos-v-300w-600w-fisa-tehnica.pdf

No price information online for this one. I'm suspecting it's significantly more than £1000, but without actually asking them I don't know...

This is all the data I need to calculate a cost-per-kWh to compare to buying the electricity from the grid. Sadly, there will be no new feed in tariffs available from January 2016 (thanks very much Mr Osborne :P )

Solar Generation Stats and wind measurements - October

We have a 2kW 8 panel solar array (Panasonic HIT panels), mounted on a south-facing roof at approximately 35-40° angle from the horizontal, which was installed at the end of August 2013.

These are the results for September 2015 (in red) with last year's results (purple), year before (green) and distribution by average sunlight 1971-2010 (met office stats) in blue:

The panels have done 112.00kWh this month - up 8kWh on last year's results, and down 11.95kWh on the 123.9kWh value forecast by average sunlight. 

With 341 hours of daylight in October (sun up to sun down for all 31 days), the average kWh generated per hour of daylight this month was 0.33kW. October last year was 0.30kW.

Last month, I started monitoring the average wind speeds across my back garden to see if a wind turbine would be a financially viable investment.

Here is a graph showing October's wind speeds:

Average wind speed for the month was 1.01m/s.  

Average gust speed for the month was 1.89m/s.

Maximum wind speed recorded for the month was 6.5m/s. 

Maximum gust speed was 9.2m/s.

Wind Generation

Yes - you read that right - wind generation.

I noticed that during the autumn/winter months, there is a significant dip in the amount of electricity generated by the solar panels, and I also noticed that during autumn and winter, it's a lot more windy. So I've been looking into the practicalities of buying a micro-turbine to balance out our renewable energy supply a bit. 

There are many different turbines available on the market (I've blogged briefly in earlier posts about wind turbines) and I've been trying to find a reliable way of comparing them - and it's hard.

There seems to be no universally-accepted standard system for quoting the power generation capabilities of wind turbines. The system that's generally used is they quote the power generated when the wind is blowing at an average speed of 11m/s. 

But then some of them quote the power generated at 12m/s. And suppose your average wind speed is only 8m/s? How much less can you expect to get from turbine A compared to turbine B? Etc., etc., I'm sure you get the picture.

There are two basic styles of wind turbine - horizontal axis wind turbines - HAWT (windmill type):

 and vertical axis wind turbines - VAWT (umm.. modern art installation type...??)

And there are lots of different variants of each of these two designs. Some have 3 blades, some 5, some 7. Some VAWTS have vertical blades, some (like the one above) have helical blades.  Which would be best for my situation?

After lots of digging around the web, I learnt these things:

1. In non-turbulent wind, HAWTs are more efficient than VAWTs.
That's why they're used in the middle of fields and far away from built-up areas. . But in turbulent wind (wind that changes direction quickly and very often), VAWTs are more efficient than HAWTs. Wind around buildings and built-up areas is always a lot more turbulent, which is why VAWTs are used in urban environments.

2. The higher your average annual wind speed, the more electricity you'll generate. 

From what I've read, people are generally saying if your annual average wind speed is less than 5m/s, a turbine would not pay for itself within a reasonable time span. You could have very high winds over a couple of months, during which you generate a lot of electricity, but then the turbine will be idle the rest of the time, and generate very little. 

3. The higher up you go, the faster the average wind speed is.  
I found a handy little website that has an archive of average yearly wind speeds for localised areas in the UK:

http://tools.decc.gov.uk/en/windspeed/default.aspx

You type in the OS grid reference of your area (we are at SD3230) and it tells you your average yearly windspeed at 45m, 25m and 10m height above ground level (agl).

So basically, you want to stick your turbine as high as you can. Tricky in a back garden - even a big one like ours. Better on top of the house, but then you get into all sorts of structural installation problems, since the forces exerted on the turbine in high winds are significant and you don't want your roof ripping off. 

However, if I were to stick a turbine on the end of my shed at 10m high, there's no guarantee I'd get the 5.9m/s average quoted above. In any built-up area there is a micro-wind climate, with trees and buildings acting as wind blocks and wind funnels from various directions - in my back garden, it may be less than 5.9m/s, it may be more. 

The only way to be sure is to measure the wind speed exactly where the turbine is going to go. So at the end of August, I bought a weather station kit from Maplin, and fitted it to the side of my shed in the back garden.

(complete with moon too!)

The anemometer (get me!) is mounted at approximately 5m high, and I have been logging wind speed results for the whole of September, and I intend to record wind speeds over the autumn/winter months and see what we get.

I've set the system to read the wind speed every 30 minutes and log it into an excel csv file (over 1900 readings for September alone!). The red is the wind speed, the green is what the system calls the gust speed - although I'm not sure what distinguishes a wind from a gust, but there you go.

Here is the graph for September 2015:

Average wind speed for the month was 1.33m/s.  

Average gust speed for the month was 2.30m/s.

Maximum wind speed recorded for the month was 5.8m/s. 

Maximum gust speed was 9.5m/s.

Solar Generation Stats - September

We have a 2kW 8 panel solar array (Panasonic HIT panels), mounted on a south-facing roof at approximately 35-40° angle from the horizontal, which was installed at the end of August 2013.

These are the results for September 2015 (in red) with last year's results (purple), year before (green) and distribution by average sunlight 1971-2010 (met office stats) in blue:

The panels have done 234.83kWh this month - up 29.7kWh on last year's results, and up a whopping 56kWh on the value forecast by average sunlight. 

With 420 hours of daylight in September (sun up to sun down for all 30 days), the average kWh generated per hour of daylight this month was 0.56kW. September last year was 0.49kW.

Solar Generation Stats - second complete year

We have a 2kW 8 panel solar array (Panasonic HIT panels), mounted on a south-facing roof at approximately 35-40° angle from the horizontal, which was installed at the end of August 2013.

We now have two complete years of generation (Sep 2013 - Aug 2014 and Sep 2014 - Aug 2015).

These are the results for y/e Aug 2014 (in green) and y/e Aug 2015 (in red) and distribution by average sunlight 1971-2010 (met office stats) in blue:

Totals for August:

The panels have done 231kWh this month - down 18kWh on the month compared to August last year.

Average generation values for August 2014 and the year:

With 496 hours of daylight in August (sun up to sun down for all 31 days), the average kWh generated per hour of daylight this month was 0.47kW. August last year was 0.50kW.

Sept 2013 - Aug 2014:                                     Sept 2014 - Aug 2015:

Sept 2014 - August 2015

Totals for the year:

The panels have generated a total of 2001kWh over the year 2014-2015. This is up 72kWh on the year compared to 2013-2014 (which was 1929kWh).  

Anomalies and differences: 

April 2015 generated more kWh per hour of daylight (0.63kW) than any of the summer months in 2014 and 2015. The main summer months July and August 2015 have both been poorly performing months in comparison to the previous year, yet the overall generation for the year is up.

Yearly average based on first two years:

The average of 1929 and 2001 is 1965kWh, which I shall use as the forecast for 2015-2016.

Any deterioration in the generation capability of the panels has been more than offset by the higher amount of sunny days in the year. Due to the huge variation in yearly generation between the 1st year and 2nd year, an accurate predication for the full 20-year generation total is not possible. However, here are the best case/worst case scenarios:

Best case scenario:
Assuming *no* degradation in generation capability, and using the 2-year average 1965kWh (as above), the 20 year total generation comes out at 39,300kWh (39.3MWh). 

Worst case scenario:
Using the lower 1929kWh as the average per year, and assuming 1% degradation per year in generation capability (this is the value given by the manufacturers), the 20 year total generation would be 36,600kWh (36.6MWh).

Financial benefit - Feed in Tariff:
This year our generation payments have gone up from 15.3p/kWh to 15.45p/kWh (1% increase) and our export payments have gone up from 4.77p/kWh to 4.83p/kWh (just over 1% increase). This has netted us a total of £356.75 for the year, up £20.92 on last year's total of £335.83.

Financial benefit - using our own electricity and not having to buy from the grid:
A bit more difficult to arrive at a figure for this. We have two electricity meters, one which records how much solar electricity we have generated, and one which records how much electricity the household has used in total. But we don't know how much of the electricity used has come from the solar panels, and how much has come from the grid. 

I work from home, and we use a lot of electricity during the day, and last year I assumed the best case scenario (ie, that we used 100% of the solar electricity that we had generated). However I think this is a touch too optimistic - this year, I am going to use a figure of 80%. I have pretty much plucked this figure out of the air, using our electricity bills and gut feeling as a guide.

80% of 2001kWh is 1600.8kWh that we have not had to buy from the grid, which would have cost us 15.78p/kWh on our current tariff. Total saving: £252.61 for the year.

Financial benefit - total for the year:
Summing the feed-in tariff payments and the savings from using our own electricity, this gives a total financial benefit for the year of £609.36. This is down £15.64 on last year's total benefit of £623.98. 

Financial benefit - total so far:

The total financial benefit we have had for the first two years is £1233.34

Break even:

Assuming an average total yearly financial benefit of £616.66 (average of first two years' values) it will take us 8.4 years to fully recoup the original £5200 investment in the panels.