Short sellers are sitting on potential losses of more than $300m in a little-known Chinese solar company whose stock has soared in spite of their heavy bets to the contrary.

Shares in Hong Kong-listed Hanergy Thin Film Power Group have more than doubled in the past six months, giving the distributor of solar equipment a market capitalisation of almost $15bn — almost as much as the three biggest US solar companies combined.

But several Hong Kong brokers report that hedge funds are still clamouring to borrow the stock, to short sell it: selling borrowed shares in the market in the hope their price will fall, so they can be bought back more cheaply and returned to their original owner. By doing this, short sellers can profit from falling prices — in effect, betting against the company’s shareholders — but lose when prices rise.