Premier Power Renewable Energy picked one of the worst days in Wall Street history to start public trading of its stock. But while upheavals in the financial sector drove the Dow Jones industrial average down 500 points, Premier Power’s shares closed 15 percent up. The company custom designs, engineers and installs photovoltaic systems. It used a reverse merger with a publicly traded shell company to go public and opened Monday for trading. The company also closed on a $7 million private investment by hedge fund Vision Capital Master Investment Fund Ltd. The cash allows Premier Power to buy solar panels at bulk prices in advance and to finance more projects for customers. It also puts the company in a position to use cash and stock to buy other solar power companies. Premier Power has contracts for $48 million in sales this year.