One of the big problems with wind energy is predicting cost efficiency and future output — in other words, not only which way the wind will blow, but also how hard. Second Wind makes some of the measurement equipment used to gauge wind strength.

The company’s “sodar” (sonic detection and ranging) device emits sound waves into the atmosphere and measures the returning sound to determine wind speed. Second Wind also sells various other equipment, from wind vanes to meteorological towers, and the data loggers to track them all.

Good Energies, a London-based renewable energy investment firm, provided the entire $4 million second round for Second Wind.