Autum, acer leaves, japan

Solar Energy and the Seasons

As a solar engineer, it’s my job to understand the movement of the sun across the sky throughout the year.  However, a technical understanding of solar movement often feels at odds with my appreciation of the world around me.  That confusion comes from our cultural perceptions of the seasons, and their definitions.  So, when exactly do spring, summer, autumn and winter start and end?

Solar Seasons

From a solar perspective, we can look at the movement of the sun across the sky.  We know that at the summer solstice, June 21st , that the sun reaches it’s highest point in the sky, and that our days are longest.  Similarly, at the winter solstice (December 21st), the midday sun is at its lowest point in the sky, and the days are at their shortest.

Midway between the two solstices lie the spring (20th March) and autumn (22nd September) equinoxes.  These dates don’t get as much attention as the solstices, but consider this – on the date of the equinoxes, everywhere on the planet receives exactly 12 hours of daylight.  It doesn’t matter if you’re in Aberdeen or Abu Dhabi, on these days, everyone is equal.

soalr energy, seasonal variation

Solar energy varies from solstice to solstice

These definitions imply that the solstices and equinoxes are the midpoints of the seasons.  It’s always annoyed me when people talk about the summer solstice as the first day of summer – from a solar energy perspective it’s the middle of summer!  Crazy fools!

It’s something our pagan ancestors understood very well.  We know that they understood the passage of the sun across the sky in intricate detail – look how Stonehenge aligns with the summer solstice, and the entrance passageway to Newgrange in Ireland aligns with the winter solstice. The four points between the equinoxes and solstices were marked with festivals, each denoting the beginning of a season.  Beltane (May 1st) marked the start of summer, and Samhain (31st October) the start of winter.  These two, in particular live on in modern times.  May 1st is still celebrated as the start of summer.  In Oxford, for example, 1000’s of revellers gather at dawn to mark the start of summer, with choir singing, morris dancers, bands, and (lets be frank here) the chance to go to the pub at 6am.  Simialrly, Samhain marked the start of winter, and now lives on as Halloween.

Similarly, the start of spring was celebrated on 1st Februray (Imbolc) and the start of autumn (Lughnasadh, or Lammas) on the 1st of August.

And this is where the whole thing falls apart for me.  Really?  Autumn starts on the 1st August?   A week ago we had the hottest day the UK has ever seen, and today it’s meant to be the start of autumn?  Are you kidding me?

Thermal Seasons

The above description of the seasons doesn’t even tally with what we were taught at school.  Back then, I was told:

  • Winter – December, January, February
  • Spring – March, April, May
  • Summer – June, July, August
  • Autumn – September, October, November

So what’s the difference?  It comes about because our perception of the seasons is more about heat than light.  There is a lag between the times of maximum sunlight and the times of maximum heat, as it takes time for the land and oceans to warm up.  This means what we feel (temperature) is out of phase with what we see (sunlight).  If we consider the lag between sunlight and heat to be 1 month, that shifts the solar definition of the seasons in line with what we were taught at school.  If we consider the time lag to be longer at 6.5 weeks, then the crazy fools who say the summer solstice is the start of summer, would actually be correct.

temperature, Seasonal, London

Temperature in London, UK peaks after the summer solstice (from www.yr.no)

What if there aren’t 4 seasons?

Now here’s a thought.  What if there aren’t 4 seasons throughout the year?  In north European climates, the year can actually be divided into 6 seasons of 2 months each.  These are based on ecology – the observed plant and animal behaviours that are seen exclusively in these seasons.  They are defined as:

  • Hibernal (winter) – December and January. Bare trees, freezing cold, and snow.  Stay inside, hot chocolate, .mulled wine and Christmas
  • Prevernal (pre-spring) – February and March. Trees begin to bud, that first bright, clear, cold morning of the year, daffodils.
  • Vernal (spring) – April and May.  Trees come into leaf, cherry blossoms, and planting crops in the veggie patch.
  • Estival (summer): June and July. Hot, hot, hot.  Vegetation in abundance, t-shirts, shorts and flip-flops, and Glastonbury.
  • Serotinal (harvest) – August and September. Leaves begin to turn, crops mature (serotinal literally means ripening). The weather is still warm, barbeques in the back garden, but you might need some candlelight at the end of the evening.
  • Autumnal (autumn) – October and November. Leaves turn colour fully and fall to the ground.  Winter coat comes out, hats and scarves, kicking piles of leaves, and catching your breath on the morning air.

seasons, solar, thermal, prevernal, vernal, Estival, Serotinal, autumnal, hibernal

For me, this seems a much better description of the passing of the year.  The ‘extra’ seasons of pre-spring and harvest capture those time of year perfectly, autumn is reserved for just the period of falling leaves, and brilliantly, winter is only 2 months long.

So, as I write this on 1st August, welcome to the start of Serotinal!   That sounds a bit of a clunky phrase – and it might take a while to catch on!  But it doesn’t sound as weird as autumn starting, when its 25 degrees outside.

So, take a look around, observe your surroundings, and find which one of these three seasonal definitions suits you best.

Further reading

Fully Charged, 2019, LIVE, Robert LLewellyn, Helen Czerski, Jonny Smith, Maddie Moate, Silverstone

Visit Joju Solar at Fully Charged LIVE 2019

Joju Solar will be exhibiting at Fully Charged LIVE again this year.  The 3-day event will be held at Silverstone Race Track from Friday 7th – Sunday 9th June.  The event is put on by Robert Llewellyn and the team behind the Fully Charged Youtube Channel, and will feature all the latest from the world of electric vehicles, and renewable technologies for the home.

We can safely say that last year’s event was by far the best trade event we’ve ever attended.  The expected audience was well exceeded and 65% of those turned up within the first hour of the first day.  When the doors opened at 10am, the surging crowds were more like a Black Friday sale than any renewable energy show we’d ever been to.

Fully Charged, Joju Solar, talking

That’s our stall with the orange posters on the right hand side.  We didn’t stop talking solar, battery storage and EVs all weekend!

What to expect this year

This year’s event promises to be even better; the venue is now double the size and there will be a wider range of activities.  The highlights include:

  • The ability to test drive the latest electric vehicles on the Stowe track. There are an anticipated 1000 daily test drives, but with 10,000+ visitors expected, you are advised to keep an eye on the Fully Charged website for details
  • Over 100 exhibitors. We’ll be there of course, but expect to see EV manufacturers, EV chargepoint industry, energy utilities, and other green transport solutions among the stalls.
  • Our stall wll feature the latest Tesla Powerwall with back-up gateway, Sunpower’s new super-high-efficiency 400W modules, our latest EV chargepoint products, including lamppost mounted ones.
  • There will be 30 live sessions across the course of the weekend, hosted by Fully Charged Presenters Robert Llewellyn, Jonny Smith, Helen Czerski, and Maddie Moate.
  • Our Technical Director, Dr Chris Jardine, will be talking about “Streetwise solar, storage and charging for suburban EV drivers” at 12pm on Saturday

So grab your tickets and come and say hello!  We’d love to talk to you about any new projects you might have, or simply catch up with our old friends and customers.  Hope to see you there!

Oxford, Power Station, Project LEO, local grid, local energy

A Smart Local Energy System for Oxfordshire

Back in the 1890’s a power station in central Oxford powered a local grid that ran the city.  As demand for electrical power grew, many small local networks like this across the country were developed.  However, by 1925, such an approach was seen as inefficient and fragmented, and major review was conducted by Lord Weir.  The British Government created the Electricity (Supply) Act of 1926, which recommended that a “national gridiron” supply system be created. This was the formation of the National Grid as we know it, a back bone of high-voltage transmission lines feeding lower voltage local distribution networks.  One outcome of this, however, was that it supported a model of large centralised electricity generation; many GW of coal, gas and nuclear plants supplying the bulk of our power.

Now, in 2019, the challenges are very different.  With the need for rapid decarbonisation of electricity to mitigate climate change, not to mention the fact that renewables are now cost-competitive with traditional generation, we now have many smaller generators connected at the bottom of the electricity grid.

Which poses the question: is the old localised energy grid model a more appropriate way of managing our electricity system in the 21st Century?  Has the wheel turned full circle?

This is what a major new project, Project LEO (Local Energy Oxfordshire), is looking to find out.

Project LEO, logo

Project LEO

Project LEO is a £13.8m project over 3 years, run by a consortium of Scottish & Southern Electricity Networks, Open Utility (Piclo), EDF Energy R&D, Nuvvé, Low Carbon Hub, University of Oxford, Oxford City Council, and Oxfordshire County Council.  The aim of the project, as the name would suggest, is to develop a local electricity market for Oxfordshire, that supplies its own needs, ensures reliable grid operation, and rewards generators a storage for the energy and flexibility they provide.

Why is this project being developed in Oxfordshire?  Currently the grid in Oxfordshire is constrained, meaning it’s hard to connect more renewable energy projects to the grid; the grid is essentially full.  There are two potential ways to solve this:

  • upgrade all the wires and substations so they can take more power. However, the expense of this could be vast.
  • Develop a smart local grid, where storage and flexible demand soak up excess renewably generated power, to allow more renewable generation to be connected without massive upgrades of infrastructure

Put another way, lets imagine a new massive solar farm was connected to the grid.  In summer the excess power would blow up the existing substations – no-one wants that!  So the first option would be to build a new substation at considerable cost.  The second option would be to find nearby users to take that excess power, which is likely to be considerably cheaper.

Local Energy Marketplace

To facilitate this, Project LEO is developing a local energy marketplace, to control and manage the operation of the ‘assets’ in a smart local energy system.  These assets might include hydro generation on the Thames which could be ramped up and down, or large heating systems such as the Bodleian book depository, which could be used flexibly according to available renewable power. It could also include smaller solar PV systems, batteries and smart EV charging.

Joju Solar to play a part

And this is where Joju Solar comes in!  We’re going to be working with our long-term community energy partner the Low Carbon Hub to deliver solar and storage projects that integrate with the Project LEO local energy marketplace.  Lots of innovation will be required.  For example, currently batteries charge from solar, and discharge to meet demand within the home.  In future, batteries will still charge from solar, but might discharge when Oxfordshire needs it, rather than when your home needs it. This should reduce costs for everyone, and allow more renewables to be connected to the grid.  However, it won’t be easy; devices will need the ability to ‘talk’ to the grid for them to be able to respond to the signals from the local market.

It’s a very exciting step for us – to go beyond simply installing generation and storage in people’s homes and businesses, and actually help create a local smart electricity grid.  We can’t wait to get started.

Further Reading

Renewable Energy, News, October, 2018

Renewable Energy News – October 2018

Recent weeks have seen dozens of stories about renewable energy hit the headlines. We have compiled our pick of the renewables news during October 2018.

12 years left to save the planet

The IPCC’s 2018 report into climate change has warned that if drastic steps are not taken in the next 12 years to curb global warming considerably, the risk of droughts, floods, heat extremes and poverty affecting millions of people will increase significantly. The world’s leading climate change scientists have indicated that urgent action is needed to limit the temperature increase to a maximum of 1.5C, in order to prevent irreversible damage to nature, in addition to climate-related poverty for hundreds of millions of people globally. Carbon pollution will need to decrease by 45% by the year 2030, which can be achieved by improved efficiency, an increase in the uptake of renewable energy, and a switch to electrified transport.

Will new diesel and petrol cars be banned by 2032?

This month, a committee of MPs have urged government ministers to bring forward the target date for banning new sales of petrol and diesel vehicles in the UK, from 2040 to 2032. Their reasoning for bringing the target closer is that they believe an earlier goal is achievable with the right leadership, and to stick to the 2040 deadline will mean the UK starts to lag behind globally in the switch to electric vehicles. Transport is currently the UK’s biggest source of carbon emissions, and car emissions are the primary cause in illegal pollution levels in many of our cities.

UK government announces subsidy cuts for EVs and hybrids

The Department for Transport (DfT) has announced that the plug-in vehicle grant, which was previously available on fully electric vehicles and hybrid vehicles, will be reduced significantly, or in the case of most hybrid models currently available in the UK, scrapped completely, under the new rules, brought in by 9th November 2018. Pure electric vehicles will go from a subsidy of £4,500 to a maximum of £3,500, with potentially a total abolition of the grant for any car after the next 35,000 low or zero emission vehicles are sold. Many have called for the government to rethink this decision if targets for low emission vehicle ownership by 2040 are still to be achieved. However, grants for the installation of electric vehicle chargepoints are unaffected.

3 million EV charge points needed by 2040

A report from Aurora Energy Research has indicated that around 3 million commercial and industrial charge points will be needed by 2040 to support the mass roll out of green vehicle fleets, with chargers installed in motorway service stations, public car parks and workplaces. The report also suggests that some of these charge points incorporating solar and battery storage technology to help generate and provide electricity when needed, could help them become profitable sooner, as well as helping to reduce some of the extra demand on the grid at peak times.

Solar energy setting new highs as coal use hits record lows

The Department for Business, Energy and Industrial Strategy (BEIS) released the latest stats in October for energy generation in the UK between April and June 2018. The 4.65TWh of solar energy generated set a new record for solar in the UK, with a combined renewable total generation of 24.3TWh during the same period, which equates to almost a third (31.7%) of the total UK electricity generated overall. In contrast, coal contributed just 1.6% in this same period, which is a record low.

A third of UK utility firms are potentially already using onsite battery storage

A survey, carried out by energy supplier, Haven Power, has indicated that around a third of utility firms in the UK are already starting to implement sustainable energy solutions, by already having some storage batteries installed onsite. The survey also showed that some areas of the country seem to have a greater awareness of the potential of using these types of technology, with 75% of London-based utility firm respondents declaring they understood how to sell excess energy generated onsite back to the grid, compared with just 11% of respondents in Wales.

For more information on battery storage systems and how they work for businesses or in residential settings, click here.