A number n is said to be economical if the prime power factori-sation of n can be written with no more digits than n itself. We show that under a plausible hypothesis, related to the twin prime conjecture, there are arbitrarily long sequences of consecutive economial numbers, and exhibit such a sequence of length 9.

The electric system needs to balance supply and demand on a moment to moment basis. Energy commodities such as coal, oil and natural gas can be readily stored in massive quantities. However, the storage of electricity has been relatively complex and expensive. Today, with the changing ways in which electricity is generated and used, increased penetration of renewable energy sources and smart gr...