NEW YORK (AP) -- Shares of alternative energy companies were mixed Wednesday afternoon, with shares of fuel-cell suppliers Ballard Power Systems Inc. and Plug Power Inc. rising after the companies received a U.S. government contract.

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The Defense Department gave Ballard and Plug a $3.5 million contract to develop fuel cells that can provide backup power for government agencies.

Ballard shares rose 33 cents, or 7.2 percent, to $4.89, while Plug stock picked up 6 cents, or 2 percent, to $3.

Shares of Hoku Scientific Inc. added 27 cents, or 2.7 percent, to $10.47.

Ethanol producer Green Plains Renewable Energy Inc. gained 56 cents, or 5.5 percent, to $10.80.

On the losing side, shares of Energy Conversion Devices Inc., which makes solar cells and fuel cell batteries, sank 71 cents, or 3 percent, to $23.10.

Fuel cell developer FuelCell Energy Inc. shares hit an annual high of $10.57 earlier in the day, but fell 28 cents, or 2.7 percent, to $10.09.

Shares of biofuels maker Verenium Corp. dipped 9 cents, to $5.69.

Shares of Quantum Fuel Systems Technologies Worldwide Inc., which makes systems for vehicles that use fuel cells and hybrid technology, gave up a penny, to $1.02.

Rentech Inc., which makes technology that helps produce synthetic fuels, lost 3 cents to $2.20.