The Winter Solstice

This is was written a few days before the Winter Solstice when the day is short and the Sun is low in the sky.  It is the time of the pre-Christian festival of Yule, regardless of one's religious beliefs, this is a time of year when the spirits need lifting from the cold and damp with parties and festivals.  At present I feel a strong desire to keep warm by setting fire to something that died a few million years ago.

Most religious festivals are linked in some way to the land and climate in which they are celebrated, for example, Candlemas (Feb-2) coincides with the time the soil starts to warm after the winter and Easter marks the start of the growing season and so on.  Whilst these events were once marked in some way, we increasingly isolate ourselves from seasonal variation with central heating in winter, air conditioning in summer and strawberries in November.  This process started with the large scale use of coal at the start of the Industrial Revolution around 1750.

The graph shows the estimated clear sky irradiance over Southern England at the time of the solstices and the equinoxes.  The energy yield at each time is proportional to the area under the curve, or to put it another way, its cold in winter and warm in summer.  It is possible to do similar things with wind.

We are an urban and industrial society and there is not going to be a return to the rural idyll (if it ever existed) any time soon.  Yet understanding and appreciating the climate and economy in which we live can lead to good designs and better decisions.  The sustainable energy economy is a big challenge and it is important to realise what can be achieved.  Industrial and urban economies need continuous supply of energy, part of the base load created by street lighting, transportation, schools, hospitals, data centres, pub signs etc..  I suggest that there is little public support for a railway system powered solely by wind turbines.  Sailing ships were displaced by coal fired steamships because they could run to schedules and were big enough to accommodate all who could afford to travel.  This base load will be underpinned for the foreseeable future by fossil/nuclear generation. Within that sector of the energy economy, the key elements are conservation, management and storage, implementation of which is not helped by legacy systems.

I'm embarrassed to admit it, but some of my interest in sustainable energy was sparked by the 1970s BBC TV series "The Good Life" in which an attractive young couple unimaginably named Tom and Barbara Good, but played endearingly by Richard Briars and Felicity Kendal attempt self-sufficiency in Surrey.  Needless to say the challenge was a rich source of humour.  My wife is too well grounded to let me indulge in such fantasies so I have contented myself with a paper project to provide 1 kwh per day from renewable sources without costing the Earth.  Whilst pondering this problem, I have learnt how to mount transistors in TO 220 cases, a little about controlling them with a computer, but I'm still struggling.  My backyard almost makes us self-sufficient in garlic and provides a small supply of vegetables of the type normally discarded by supermarkets but as a source of wind and solar energy it is a sad disappointment.

The path of helium filled balloons which have escaped from young partygoers suggests that at around 500m there might be a steady wind, but the neighbours, tolerant in many ways would not accept an airborne wind turbine.  A boat on a river estuary might work, but my wife is too well grounded to let me indulge in fantasies.  The obvious solution is to buy electricity from people who generate it from wind, solar and other sustainable sources and use the grid as a delivery system.  But energy from these sources is a natural product whose availability changes with the seasons.