Proportion of year spent at each insolation level information

[fourtytwo42]

Has anybody seen any data available on this subject ?

There are plenty of tables giving the total insolation for a location and orientation BUT the results are usually totaled in Kw/h or similar.

What I am interested in is a set of figures giving the total hours spent at each insolation level within that total.
I have a completely weird reason for wanting to know based around having a fixed load resistance and no MPPT.

Of course I think its a bit unlikely so I am trying to derive my own figures with lots of holding ones finger in the wind, but I like grasping at straws too so perhaps there's something out there ?

[CatalinaWOW]

Has anybody seen any data available on this subject ?

There are plenty of tables giving the total insolation for a location and orientation BUT the results are usually totaled in Kw/h or similar.

What I am interested in is a set of figures giving the total hours spent at each insolation level within that total.
I have a completely weird reason for wanting to know based around having a fixed load resistance and no MPPT.

Of course I think its a bit unlikely so I am trying to derive my own figures with lots of holding ones finger in the wind, but I like grasping at straws too so perhaps there's something out there ?

Doing searches for daily insolation or monthly insolation has always given me what I needed.   There are maps that let you zero in on the average values over fairly small regions.  Unit conversions are often required to get the form of information you want.

You are on your own for the site specific variations from these averages.  If you live behind a tall building, or in a deep valley things can be very different.

[Someone]

Thats something the meteorology department does:
http://www.bom.gov.au/climate/data/oneminsolar/about-IDCJAC0022.shtml
The met office has the data somewhere:
http://badc.nerc.ac.uk/data/surface/radt_file_format.html

[fourtytwo42]

Thank you for your replies I should have said I am in the UK and our met office wants to sell most data.
I found this site http://www.pveducation.org/pvcdrom/calculation-of-solar-insolation that gives basic data without weather corrections but I also use a weather forecast that gives me cloud cover. I will post whatever fudged data I manage to produce here for your amusement in a few days.

[fourtytwo42]

I should entitle this lies and damm statistics BUT as promised here is my chart adjusted for seasonal and weather variations. It compares the power that could be derived from a 1Kw PV system using MPPT and that derived using a simple restive load (in this case 20R heater). The idea is to determine the real gain of MPPT in this situation and if it is economically justified. Of course the chart is very situation dependent but here in the UK the average insolation is quite low and we have a fair amount of cloud cover, the resistive load matches MPPT at about 70% insolation.
Plotting the resistive load line against MPPT for different insolations makes you believe there is a lot to be gained but when you factor in the hourly insolations and weather the losses are not so large.

[splin]

I think this is what you are looking for:

http://re.jrc.ec.europa.eu/pvg_tools/en/tools.html#DR

It's a fabulous resource. Select your location on the map, select 'HOURLY DATA', select the year(s), slope and azimuth of the panel, select 'Radiation components' and click 'Download csv' to get hourly data for the whole period. The total insolation is the sum of the Bi (In-plane beam irradiance) and Di (In-plane diffuse irradiance) columns in W/m2. I'm not sure about Ri (Reflected irradiance) - probably also needs to be included in the total but it won't make much difference.

You can even upload your own horizon file to account for your own shading objects (but the tool does use geographical mapping data to calculate the horizon).

This a beta version of the tool - the current version is here: http://re.jrc.ec.europa.eu/pvgis/ but doesn't directly give you hourly data for a specific year but does give average hourly radiation for a specified month. Its worth a look because it provides a bit more data. The monthly radiation tab also provides the number of heating degree days which the beta version doesn't seem to - but as it provides hourly temperature data for the year you can calculate that yourself.

[EDIT 1] Corrected DAILY DATA to HOURLY DATA

[EDIT 2] Attached 2016 insolation graph for East Midlands, south facing at 30% slope. This was derived from the hourly data and used the frequency() function in Excel. 4432 of the 8760 hours in the year received no insolation.

In 845 hours the insolation was between 0 and 5% of the peak, ie. 0 < insolation <= 53.6 W/m^2

[fourtytwo42]

Thats astonishing splin thank you very very much a much better site than I ever found. Just goes to show the data is there if only you know where to look (mining). I was trying to make the economic case for adding the low insolation technology and decided to do it based on my fudged figures but now I will have a way of making proper assessments.

I wish I was facing a bit more around to the south instead of SSW to pick up more earlier in the morning but hey I got 52degrees slope, 30% sounds like hard work especially in winter. I wonder how long it will be before we start altering our roofs to suit solar technology, windmill caps come to mind