Zolo (Boulder, Colorado) has developed sensor and monitoring equipment used to improve the efficiency of large combustion sources such as coal-fired power plants and gas turbines and which also, therefore, help reduce harmful emissions, including greenhouse gases. The technology is based on tunable diode laser absorption spectroscopy instrumentation developed at Stanford University.

The money is earmarked for the deployment of sensors for coal-fired power plants, and to develop sensors for other industrial applications, the company said. Zolo's existing customers include: PacifiCorp, Texas NRG, Xcel Energy Constellation, CPS Energy, and the United States Department of Defense.

El Dorado Investment Company is the venture capital arm of PinnacleWest Capital Corp., owner of Arizona Public Service. Existing Zolo investors, Canaan Partners, Crescendo Ventures, and Morgenthaler, among others, also participated in the round.

"Zolo Technologies is perfectly positioned to help mitigate growing concerns about the efficient and clean generation of energy as well as global climate change," said Todd Jaquez-Fissori, investment partner of Siemens Venture Capital, in a statement. "Their products also dovetail extremely well with several business interests of Siemens Power Generation."

"Siemens AG and Arizona Public Service, the business arms of our new investors represent very large potential customers, as well as strategic business partners," said Henrik Hofvander, chief executive officer of Zolo, in the same statement.