Twitter (News - Alert) is not the only tech stock whose forthcoming IPO has caught the attention of curious investors.

News reports point out that there are 13 initial public offerings now taking place in the United States. Many relate to technology or Silicon Valley, VentureBeat reports based on a list provided by Renaissance Capital.

When it comes to alternative energy, Pattern Energy Group had an IPO. The company owns and operates eight wind farms in the United States, Canada and Chile. Pattern Energy Group raised $352 million. It sold 16 million shares. They sold for $22 each, which was more than the predicted $19-$21 range, according to Investor’s Business Daily.

Voice over Internet Protocol is another sector represented in the flurry of IPOs. RingCentral (News - Alert) offers VoIP phone systems to small businesses. It sold 7.5 million shares at $13 a share. That represents the high end of its expected $11-$13 range, according to Investor’s Business Daily.

And Violin Memory, offering enterprise flash-based storage systems, sold 18 million shares for $9 a share. That is in the middle of its $8-$10 range. It was able to raise $162 million, Investor’s Business Daily reported.

Consider too Applied Optoelectronics, a provider of fiber-optic networking products. The company expected to raise $50 million in the IPO. Some 3.6 million shares were to be offered. The price per share ranges between $13 and $15.

Also, Covisint, which offers a data sharing platform, expected to raise $64 million in its IPO. It was to offer 6.4 million shares for between $9 and $11.

Montage Technology Group, a Shanghai, China-based fabless provider of chips for set-top boxes and in-memory computing, was also to have an IPO. It wanted to raise $92 million. Some 7.1 million shares were to be offered. The range per share was $12 to $14.

Some biotechnology, health care and pharmaceutical businesses will also hold IPOs. They include Enzymotec, Evoke Pharma, Fate Therapeutics, Foundation Medicine, Ophthotech, and Premier, according to the list. An energy company, Tecogen, will hold an IPO, too.

Looking at the list, 11 of the 13 businesses will join the Nasdaq. RingCentral and Violin Memory will be on the New York Stock Exchange. Pattern Energy Group will be included on both the Nasdaq and the Toronto Stock Exchange.