Book Review – Let It Shine, The 6000-year Story of Solar Energy by John Perlin

Let it shine coverPerlin’s history of solar energy use is very interesting.  The book is rich in historical incidents and illustrated with old photos and drawings.

Perlin divides the book into six sections.  He begins Part 1 of his tale by discussing how the ancient Chinese, Greeks, and Romans designed their buildings to take advantage of solar heating in winter and to minimize over-heating in summer.  He discusses “burning mirrors” used to concentrate the sun’s rays to start fires, heat objects, and even as weapons of war.  Some of that evolved to using lenses to concentrate the sun.  The Romans used glass to trap heat, but after the fall of the empire, this was abandoned because hard times required defensible homes and besides the Church frowned on growing exotic plants outside their natural habitat.  However, by the sixteenth Century, the influence of the Church was broken and greenhouses started to be used.  A good thing too, because during the period 1550 to 1850, called the Little Ice Age, growing seasons were very short.  Another technique was to grow plants near a heat-absorbing brick or stone wall.   Perlin discusses various methods of glass-making and greenhouse design.

Part 2 deals with the history of  solar syphons and engines used mainly to pump water. Of course, the problem with most of these contraptions is they didn’t work at night or on cloudy days.  There were, however, a few installations that stored heat during the day to run, or partially run, the motors at night.  However, such installations were much more expensive to build than conventionally fueled plants.  World War I interrupted some grand schemes and cheap oil available after the war caused investors to lose interest.  Perlin also mentions use of solar evaporation to produce salt.

Solar water heating is the subject of Part 3.  “The story of solar water heating begins in the nineteenth century when Europeans and Americans began to bathe on a regular basis.” Perlin first describes conventional, in home systems, then moves on to solar water heaters. He provides many drawings of the devices he describes. Within this section, Perlin has a chapter on the solar still, a device used by downed-airmen to desalinate sea water.

I note here that solar energy provides about 85% of the hot water needs in my home (the rest is from natural gas).

Part 4 deals with the history of using solar energy to heat homes.  In Europe, knowledge of proper house citing to take advantage of the sun was seemingly lost after the fall of the Roman Empire, and cities were built without regard to structural position relative to the sun. But ancient knowledge was revived and improved upon during the “Enlightenment” beginning ca. 1800.  The basic principle is to have large windows facing south-southwest (in the northern hemisphere), to take advantage of the low winter sun angle to heat the house.  During the summer, the high angle of the sun does not penetrate much into the structure.

In America, solar architecture was practiced early on by the Pueblo Indian tribes of the Southwest.  The Spanish colonials also practiced proper solar orientation of structures as did settlers in New England with the “saltbox” style of housing.  There was much experimentation and refinement ( and controversy) with solar architectural techniques.  In this section Perlin discusses various types of solar collectors.

Part 5 deals with the discovery of the photovoltaic effect and the development of photovoltaic solar collectors.

Part 6 deals with what Perlin calls the post-oil embargo era.  For 30 years after World War II, oil and gas were abundant and inexpensive. The U.S. government was providing encouragement for nuclear power, “atoms for peace” but provided little or nothing for solar energy research.

The modern solar movement may have been born on “Sun Day” in 1978 according to Perlin.  Reports of the time said the solar movement “has some of the attributes of a political movement.”  Solar pool heating made inroads in the 70’s and 80’s.  The counterculture embraced solar energy and solar architecture was rediscovered.

The oil embargo of October, 1973, brought great disruption.  The Arab’s cut back on oil exports as a reaction to U.S. support of Israel in the Yom Kippur War. This was also the time that “peak oil” predictions began, i.e., concern that we were using oil faster than new reserves were being discovered. (Shale oil and gas and vast new resource discoveries on the continental shelf have put the “peak oilers” out of business.) Nevertheless, at the time, there was more interest in alternative energy sources and solar energy was one of them.  There was much interest and many  schemes for equipping homes and businesses with photovoltaic arrays and solar collectors to produce electricity and heat.  Perlin describes the various programs, public and private, and the development of solar cell technology.

Overall, this is a very interesting book on the development and use of solar energy through the ages.  I was somewhat put off by the Forward to the book, written by Amory Lovins, chief scientist at the Rocky Mountain Institute, which struck me as  mainly propaganda that made some questionable claims. For instance, he claimed that renewable energy projects, mainly wind and solar, receive subsidies smaller than nonrenewable energy projects get. That may have been in the early days but CBO data shows that is not true, at least since 2008, see:

Perlin takes a dim view of utility scale solar electricity generation because of its high cost.  He prefers dispersed arrays on individual buildings.  Indeed, the cost of electricity produced by utility-scale arrays is much higher than from conventional generation (see my post “Solar energy cannot economically compete in electricity generation“).   There is also the inconvenient fact that the footprint of solar and wind farms is very large. (See my post “The Scale Problem.)

This book is a recommended read.  It can be found at Amazon, and at Barnes & Noble.