Necessity, they say, is the mother of invention. A metaphorical DNA test, however, suggests that its father is probably that old reprobate, Creativity. The simple fact is that for many inventors, a pressing need is not essential: scientists often create something new just because they can. Moreover, there is often a prolonged gestation period before Necessity actually gives birth, with a typical invention – be it a physical object, a protocol such as the World Wide Web or a theory – going through three stages as it passes from idea to prototype to product. In the case of Newtonian mechanics, for example, the three stages were the alleged apple, the impenetrable Principia and those neat equations we all know.

But whatever it is, an invention has to work both in principle and in practice. If it doesn’t, it is just a silly idea, and we all have plenty of those. Journalist Tyler Hamilton’s book Mad Like Tesla contains much that may turn out to be in the “silly idea” category. In it, he reports on the sincere but distinctly unconventional attempts of various maverick inventors – most of them Canadian, like Hamilton himself – to create new ways of harvesting sustainable energy. Maverick Canadians? Yes, they do exist.

Some of their efforts seem to fail at the idea stage: Thane Heins’s electric motor produces more power than it consumes, he says, but he is touchy about people testing it. Others falter as prototypes: Dick Weir and Carl Nelson’s supercapacitors should store energy more efficiently than batteries but, although the principle is sound, materials seem to be a problem and the demo date keeps receding. As for Cal Boerman and Gary Spirnak, their big idea is a giant solar collector in space, beaming microwave power to Earth. They cannot afford the luxury of a prototype – it is go for it or bust.

Only a few of the inventions in Hamilton’s book, such as Jay Harman’s energy-saving fans inspired by natural vortex motion, have made it to product stage, and all are viewed with suspicion by the energy business. However, as Hamilton keeps telling us, Nikola Tesla was also thought to be mad – yet that did not stop him from inventing the three-phase induction motor that powers much of modern industry.

Reading Hamilton’s book, you cannot help feeling that what powers some of these would-be Teslas is the X-Factor factor: the lust for fame. Yet fame, for most inventors, is an uncertain prize. In another book on odd inventions, How James Watt Invented the Copier, author René Schils focuses on the lesser-known activities of 25 famous scientists. These include the titular Watt, whose copier created duplicates by pressing letters written in slow-drying ink onto thin paper. This device was a minor commercial success, but most of us would not have heard of Watt had he not also revolutionized the design of steam engines.

The subtitle of Schils’s book, Forgotten Inventions of Our Great Scientists, is disingenuous, since only a few of his examples are true inventions. The rest are observations or calculations, though none the less fascinating for it. Astronomer Harlow Shapley, for instance, relocated the Sun to the suburbs of our galaxy, but sought relief from his day job (well, night job) by watching his observatory’s resident ants. He found that their speed depends on temperature, something entomologists had not noticed. Benjamin Franklin used his job as Britain’s deputy postmaster general (yes, really) to ask why mail boats took so long getting to America. Answer: the Gulf Stream, a phenomenon then unknown to the British navy. Thomas Young of double-slit fame helped to decipher hieroglyphs via the Rosetta Stone. And Rosalind Franklin – the only woman to appear in either of these two books – worked on carbon as well as DNA, paving the way for the discovery of buckyballs.

But the genuine inventions created by some of these big names can be interesting too. Exhibit A is Albert Einstein and Leó Szilárd’s absorption refrigerator, which worked on a principle still used in fridges for caravans. Inside their fridge you might find soda water, invented by pioneering chemist Joseph Priestley. And while sipping it, you could estimate how many years you have left to live by using life tables originally devised by Edmund Halley in moments spared from sorting out the regularly recurring comets.

There is plenty to think about in these two books. Why, for instance, is it so hard for inventors to break into established markets? In energy supply, obviously, companies cannot simply junk huge infrastructure investments in favour of something new, however good it might be. But what about Harman’s energy-saving vortex fan? Surely it cannot be that difficult to fit a different kind of fan to a computer? Maybe the fan is not all it is cracked up to be.

Overall, there is a strong whiff of boosterism around Hamilton’s book, and despite his hard-nosed journalistic training and frequent caveats, he has perhaps been charmed into accepting some of the wilder claims of these hippyish entrepreneurs. Still, at least all of them are trying to do something new. Some of the characters in Schils’s book, by contrast, have sidelines not a million miles away from the stuff they are famous for. Kelvin’s work on the transatlantic cable, for example, was simply another bit of mathematical pragmatism, of the same kind that led him to the absolute scale of temperature. And Darwin’s study of worms was, to him, not a sideline at all but central to his achievement and part of the famous peroration to On the Origin of Species.

Nonetheless, both books are worth a look for the sheer entertainment value of their subjects, be they kooky believers in bizarre phenomena or just scientists taking a break. Reading about such characters, you really cannot avoid the conclusion that Necessity may be the mother of invention, but its father is the compulsion to invent.