Frosty Nights

 January 2022 started with three warm days and nights where even the night minimum temperatures were ≥ 8oC, well above the average day/night temperature (4.3 oC) for Hereford in the month of January.

As I write this post (18/1/22), we have had a week of subzero night temperatures and average day/night temperatures of about 1 oC.

The garden plants have survived remarkably well. Following a -4 oC overnight temperature, the daffodils looked a little sad...

...but soon recovered in the afternoon sun.

I was a little more concerned about the snowdrops, in spite of their hardy nature, as the first flower of 2022 lay prone across a nearby stone...

Recovery took a little longer in the shady wood-in-the-garden but, by mid-afternoon, it was standing proud once again...

How do plants survive subzero temperatures? It may be a combination of factors but is mainly down to the presence of sugars and proteins in the plant sap which depresses the freezing point of water; in effect, they possess their own form of anti-freeze. 

The First Snowdrop of 2022

This is our wood-in-the-garden. Small in size (less than 3 square metres) but containing two Oaks, two Hazels, two Hollies, and one each of Birch and Rowan. Not sure what constitutes a wood but the generally accepted definition of an orchard is 5 trees. There are other trees dotted about the garden: Elder, Photinia, Ornamental Crab Apple, Strawberry Tree, another Birch, Winter-flowering Cherry, another Rowan, Acer, and two Pine Trees. And we also have an orchard: eight Apple, two Pear, three Plum, a Crab Apple and a Medlar.

Now, where was I? Oh, yes! Our first, fully-formed, snowdrop of 2022 appeared in the garden on or around January 9th according to Mary. I took an out-of-focus photo on January 13th but here is a better photo of the same snowdrop in our wood-in-the-garden on 16th January.

Galanthus, or snowdrop, translates from Ancient Greek as milk flower which is certainly descriptive and appropriate. On the other hand, the snowdrop is often referred to as a harbinger of spring which seems somewhat inappropriate since its first appearance occurs, in this part of the world, in or around the middle of winter when Spring seems a long way off. Nevertheless, it is always a pleasure to see.

Anecdotally, this year's first appearance of a snowdrop flower seems early. December 2021 was warm which may explain why. Looking back a year, this photo of snowdrops in the snow was taken on the 24th January 2021 inferring we are, climatically, a couple of weeks early in 2022 in the phenological cycle of the snowdrop. Of course, it could just mean that 2021 was unusually cold at the start of the year and that is what held back the 2021 growing season. It will be interesting to see whether this year's growing season starts a bit earlier.

Pears Pared to the Final Pair

 

Pears (noun) - a yellowish- or brownish-green edible fruit that is typically narrow at the stalk and wider towards the base, with sweet, slightly gritty flesh

Pare (verb) - reduce (something) in size, extent, or quantity in a number of small successive stages

Pair (noun) - put together or join to form a pair

January 10th 2022 and the last two fruits from the 2021 harvest were consumed today for breakfast. Most of the pears were eaten fresh, a few were given away and some were enjoyed cooked in red wine. How to pick and store pears is described here. My prediction the pears would last into 2022 was just about met; the consumption rate was just over 1 pear/day.

Conference pears cost about 40p in the supermarkets so the 2021 harvest was worth about £50-£60. And Concorde is a better-tasting pear than Conference! Apart from the initial purchase, there are no significant season-to-season costs. Maintenance time (winter pruning and autumn fruit-picking), is minimal, especially if you choose a trained form like espalier.

 

PV Generation - 16 Years and Still Going

A photo from the newly installed CCTV camera showing part of the roof-mounted solar PV array.

Time for an update on the performance of my PV panels. A nominal 4.92 kW of panels installed as two separate arrays and 'activated' on 9th December 2005 has been in operation for more than 16 years. The original cost was £25,000 although there was a grant of 50% at the time. I also receive just over 14p/kWh from EON for all the electricity I produce.

The last report was rather brief and I had intended to expand upon it with some explanatory data. See here, here and here for related links.

The PV solar panels are maintenance-free although two components have failed since installation. One of the two inverters failed in August 2015 after 9½ years in service; it took 6 months to replace for a number of reasons including the original installer going out of business. Cost £1087.37 including fitting and testing. In August 2020, after nearly 15 years in use, the generation meter started to fail (intermittent readings) and then completely failed (no readings) in December 2020. A replacement meter was fitted on 17th February 2021 (delay due to COVID). Cost £72 including installation and testing. Caplor Energy were supplier and fitter for both items.

The table below summarises the total annual electricity generation readings from both solar PV arrays, along with the annual sunshine hours recorded at the Ross-on-Wye weather station.

Year	No of operating years	PV generated (kWh)	Sunshine hours (R-on-W)
2006	1	3988	1721
2007	2	3966	1622
2008	3	3801	1498
2009	4	3832	1576
2010	5	3900	1579
2011	6	3904	1515
2012	7	3674	1433
2013	8	3661	1522
2014	9	3887	1579
2015	10	3885	1636
2016	11	3807	1512
2017	12	3704	1516
2018	13	3968	1739
2019	14	4071	1578
2020	15	4342	1860
2021	16	3744	1593

[Note 1: Annual readings on the 8th December were taken until December 2012; thereafter, monthly readings on the 8th of the month. Note 2: The data for each calendar year covers the period from December to December; e.g. 2010 reports the elelectricity generated and sunshine hours measured from December 9th 2009 to December 8th 2010. This is to match up with the number of operational years. Note 3: Sunshine hours are taken from the Met Office's Ross-on-Wye weather station. Note 4: Sunshine hours at Ross-on-Wye changed from Campbell-Stokes recorder to Kipp & Zonen sensor at the end of 2018. I have used a correction factor of 1.2 to convert KZ values to CS values. Note 5: PV generation data between August 2015 and December 2015 underestimated due to failing/failed inverter; no correction has been made to the generation measurements for 2015. Note 6: No generation data are available for December 2020 and January 2021 due to meter failure; value for February 2021 will be under-reported. Estimates for generation data for these 3 months, using data from the previous 4 years, have been used to fill in the gaps.]

Annual PV generation data are summarised in the histogram below.

As noted previously, the efficiency of the PV panels is expected to decrease with age but this has been offset by a small but noticeable rise in annual sunshine hours.

Since 2012, I have been collecting monthly generation data and this allows me to dig a little deeper to see when the extra sunshine hours occur. Approximately 90% of the electricity generated is during Spring (MAM), Summer (JJA) and Autumn (SON) so this is the obvious place to look for changes in sunshine hours using electricity generation as a proxy for sunshine hours.

Over the 2012-2021 period, PV generation increased during Spring (March, April, May: MAM), slight decrease/no change in Summer (June, July, August: JJA) and a small increase in Autumn (September, October, November: SON). In total, based on linear regression best fit, there was an increase in PV generation of approximately 40 kWh/year over this period - or about 1% per annum - due to increased solar radiation. The linear relationship between sunshine hours and PV generation is illustrated below. 

By implication, the efficiency of the solar panels is also decreasing by about 1% per annum which is roughly in line with expectations.

Here's hoping for sunny weather in 2022...