[Photo: David Rubinstein interviewed on CNBC's Squawk Box / NYTimes]

Faced with richly valued stocks and bonds, investors are turning to private-equity firms for higher returns.

Carlyle Group said it expects to raise $100 billion for its funds in the next several years from investors seeking higher returns in an era of ultralow interest rates and richly valued stocks and bonds. The Washington, DC, PE firm currently manages around $169Bn, up from $107Bn at the end of 2010. David Rubenstein, who founded the firm in 1987 with William Conway and Daniel D’Aniello, called the fundraising goal “substantial but quite realistic.”

It is not clear where all the money flowing into private equity will go. U.S. PE funds were already sitting on an all-time high of $474 billion of investor commitments, or “dry powder,” at the end of 2015. And, keep in mind that Carlyle has invested (just) $12.5Bn in the past 12 months, and has $54.4 billion in dry powder.

Private-equity firms like Carlyle buy companies and fix them up with the intention to sell them later for a profit. The firms also buy real estate, make loans and invest in infrastructure and corporate debt, among other activities.

Yet, despite such high cash piles, investors continue to pour money into funds, lured by the promise of higher returns. Carlyle said it is likely to start raising money for new buyout funds targeting the U.S., Europe, Asia broadly and Japan specifically by the end of 2017. It expects funds targeting energy and real estate to add to the haul.