In India, cluster bean (guar) is traditionally used as a vegetable or animal feed, but recently, the cultivation of this has assumed significance. Which one of the following statements is correct in this context?

With reference to 'fuel cells' in which hydrogen-rich fuel and oxygen are used to generate electricity. Consider the following statements:
$1.$ If pure hydrogen is used as a fuel, the fuel cell emits heat and water as by-products.
$2.$ Fuel cells can be used for powering buildings and not for small devices like laptop computers.
$3.$ Fuel cells produce electricity in the form of Alternating Current (AC).

Which of the statements given above is/are correct?