Annual variation in location of sunrise and sunset

Friends, we are just 16 days away from the winter solstice, and those of us who live in the UK are dismally aware that at this time of year, the Sun only rises above the horizon for about 8 hours.

And not only does the Sun rise above the horizon for a short time, it also fails to rise very high in the sky.

Together these factors make for poor yields from solar panels.

This article is about a third factor which I feel is sometimes overlooked: the location of sunrise and sunset.

The location of sunrise#1

I asked OpenAI Chatbot about this:

How does the location of sunrise vary through the year in the UK?

The location of sunrise in the UK varies significantly throughout the year. In the winter months, sunrise occurs in the southeast, while in the summer months, it appears in the northeast. The amount of daylight hours in the UK also increases as the year progresses, with the summer months having the longest days and the winter months having the shortest.

This is an excellent answer. Accurate and concise. I followed up:

How far north of east does the sun rise at the summer solstice?

At the summer solstice (the longest day of the year), the sun rises as far north as 70° north latitude in the UK, which is around halfway between East Anglia and the Shetland Islands.

In contrast, this answer is utter nonsense! So I guess I will have to write this article myself!

The location of sunrise#2

I was interested in the location of sunrise because of the new panels I am installing will face about 22° north of east – not a very favourable location.

I looked up data for each week of the year from The Time and Date website: the data below are relevant to London, but you can look up data for many other locations worldwide if you are interested.

Click on image for a larger version. This is an extract from tables at the Time and Date web site. It has both the time of sunrise and sunset and the angle of sunrise and sunset measured clockwise from due North.

I then collated the results and plotted them through the weeks of the year.

Click on image for a larger version. This graph shows how the location of sunrise and sunset vary through the year. Angles of sunrise and sunset measured clockwise from due North.

The graph above shows that the phrase: “the Sun rises in the East and sets in the West” is only approximately true. For 6 months of the year, the Sun rises north of East and sets north of West.

My New Solar Panels
This is probably not news to anyone, but I found it interesting, because I am putting solar panels on my home that face north of East.

Click on image for a larger version. Google Maps view of my house showing existing solar panels in blue and the new panels in Yellow. For 6 months of the year between spring and autumn equinoxes, the panels should produce a useful solar yield in the morning.

After plotting these lines on the map, and noting which houses the lines intercepted, I was able to translate them onto a photograph to show the expected location of sunrise through the year.

Click on image for a larger version. Photograph showing the ‘panels-eye’ view of the street-scene at the back of the house For 6 months of the year between spring and autumn equinoxes, the panels should produce a useful solar yield in the morning.

Considering all the panels on the house,- including the 12 installed in November 2020 – in summer the system should generate from early dawn – only just after 4 a.m. in mid-summer, to almost 8:00 p.m. So despite the poor orientation, the Easy-PV calculator suggests the 5 panels will generate 1,338 kWh per year (268 kWh/panel) compared with 3,860 kWh year from the original 12 panels (322 kWh/panel).

Click on image for a larger version. Charts showing the angular extent of daytime through the year. The orientation of the three sets of panels on the different roofs is shown as red arrowed lines.

Along with the 5 panels on the roof, I have installed three panels on the flat roof which are only at 12° to the horizontal. The Easy-PV calculator suggests these 3 panels will generate 919 kWh per year (306 kWh/panel), although I am not sure I properly accounted for shading.

Click on image for a larger version. The same photograph as above but now showing the panels on the flat roof.

Summary
Sadly, although the panels have been installed for more than month, no inverter has been installed and they have not been connected to the grid. Apparently, this will happen “tomorrow”.

But if the output is as I anticipate, then next year the system will generate around 6 MWh. The amount we draw from the grid should be slightly reduced as I hope we will be off-grid for 6 months rather than 4.5 months year. So considered over a year, cumulative generation should be roughly twice as much as we draw from the grid.

Consequently – considered over a year – we should export almost as much as we import, which is getting close to one definition of carbon neutrality. This is my dream!

Click on image for a larger version. Cumulative PV generation for 2022 is just under 4 MWh, in line with the MCS guidance when the system was installed. Cumulative Grid Consumption is expected to be just over 3 MWh this year. The dotted purple line shows anticipated generation next year.

6 Responses to “Annual variation in location of sunrise and sunset”

  1. David Cawkwell Says:

    You might want to consider night storage heaters used to store the electricity during the day as heat and release during the night. Quite cheap second hand.

    • protonsforbreakfast Says:

      David,

      Good Morning.

      Storage heaters are a great solution for many people. As you say, they are relatively cheap and work well for winter heating where the next day’s heating requirement can be accurately predicted. My neighbours have them and they are very happy with them.

      Overall, they are not as efficient as a battery/PV/heat pump system. This can store cheap-rate, lower-carbon nightime electricity in a battery and then use that during the day to operate a heat pump. At this time of year this produces 4 x the heat of a system using storage heaters for the same electrical consumption.

      Admittedly, the capital costs are higher, but in terms of abating CO2 emissions, I don’t know of anything that can beat a heat pump! And even in December about 10% of the electricity is provided by solar PV!

      All the best

      Michael

      • David Cawkwell Says:

        I mean to use the night storage heaters to store day time solar for use at night. Especially good for where I am in Portugal. Sunny days but nights can be colder. Plus no need for large battery banks and the night storage heaters can be kept fully charged it is not necessary to use them when it is warmer than expected. No moving parts so a very reliable system.

      • protonsforbreakfast Says:

        Ah yes. That is a great idea and I will suggest it to my neighbour. Unfortunately, solar production is almost exactly in anti-phase with our heating requirements.

        But we do still capture solar energy in December (only about 2 kWh/day) and this is used to power the heat pump and deliver around 8 kWh of heat!

        I hope it stays warm in Portugal!

        But I

  2. edhui Says:

    There appear to be substantial areas of your garden covered by grass. Given that its admittedly impressive carbon capture qualities are negated by a fast return to the atmosphere however you dispose of your clippings, wouldn’t it be advantageous to your carbon budget to completely cover your garden with panels as well?

    • protonsforbreakfast Says:

      Ed,

      Good Morning.

      Surely you don’t imagine that I haven’t thought about it?! However, I am not the only resident of this dwelling and my co-resident has an attitude that could be described as NIMBY. One can’t win all the battles!

      All the best

      Michael

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