Randall MacEwen has been named CEO of fuel-cell developer Ballard Power Systems. Previously, MacEwen was EVP of Stuart Energy Systems, an onsite hydrogen production company, and CEO of Solar Integrated Technologies. John Sheridan, the current CEO of Ballard, is retiring after serving in that role since 2006.

Stem, an energystorageintegrator and services provider, named Karen Butterfield as chief commercial officer. Most recently, Butterfield served as managing director of national account sales for SunPower. 

WaterSmart Software, a behavioral water efficiency startup, added new CEO Robin Gilthorpe, formerly the CEO of Terracotta. The company also named Doug Roy as VP of sales. Prior to joining WaterSmart, Roy was director of sales for Schneider Electric Water. 

Dan Sowder, formerly a senior project manager at Duke Energy, is now Director of Power System Engineering at 1Energy Systems, a software developer for energy storage systems.

Nick Galesic, formerly with Panasonic Eco Solutions, is now a project manager in operations at SunEdison.

Competitive Power Ventures promoted Paul Buckovich to CFO. Previously, Buckovich served as the firm's senior VP of finance. The firm has 5,000 megawatts of conventional generation and 1,300 megawatts of wind power projects in development across North America. Its Asset Management group has close to 5,000 megawatts of natural gas generation and wind power under management.

I missed this item when it broke, and it's worth logging: Colin Murchie, formerly the director of government affairs at SolarCity, joined Sol Systems in April as director of project finance, according to his LinkedIn profile.

Advanced battery maker Aquion added Tom McDaniel to its board of directors. McDaniel spent 37 years with Edison International, where he served as CFO. He currently serves as chairman of the board of Tendril Networks, an energy management software firm, and he is a director at SunPower, the high-efficiency PV panel maker.

Jigar Shah joined the board of sPower (Sustainable Power Group), a renewable energy provider. Shah founded SunEdison, a solar services firm. SPower is a vertically integrated owner-operator of utility and distributed electrical generation systems across the U.S., actively buying solar development assets in any stage of development. SPower is a portfolio company of Fir Tree Partners, a global investment fund.