A process for the preparation of water-absorbent polymer particles, comprising the process steps of (i) preparing an aqueous monomer solution comprising at least partially neutralized, monoethylenically unsaturated monomers bearing carboxylic acid groups (α1) and at least one crosslinker (α3); (ii) optionally adding fine particles of a water-absorbent polymer to the aqueous monomer solution; (iii) adding a polymerization initiator or a at least one component of a polymerization initiator system that comprises two or more components to the aqueous monomer solution; (iv) decreasing the oxygen content of the aqueous monomer solution; (v) charging the aqueous monomer solution into a polymerization reactor; (vi) polymerizing the monomers in the aqueous monomer solution in the polymerization reactor thereby obtaining a polymer gel; (vii) discharging the polymer gel out of the polymerization reactor and optionally comminuting the polymer gel thereby obtaining polymer gel particles; (viii) drying the polymer gel particles; (ix) grinding the dried polymer gel particles thereby obtaining particulate water-absorbent polymer particles; (x) sizing the grinded water-absorbent polymer particles; and (xi) treating the surface of the grinded and sized water-absorbent polymer particles; wherein in process step (i) the preparation of the aqueous monomer solution comprises the step of: (ia) at least partially neutralizing acrylic acid by mixing acrylic acid with an aqueous solution of sodium hydroxide, thereby obtaining an aqueous solution of the at least partially neutralized acrylic acid; (ib) cooling the aqueous solution of the at least partially neutralized acrylic acid with a cooling liquid in a heat exchanger, wherein the cooling liquid used in the heat exchanger has been cooled in an absorption chiller in which at least a part of the heat of the heated cooling liquid obtained in the heat exchanger is consumed by the evaporation of a refrigerant liquid in a vacuum that is created by the absorption of a refrigerant vapour into an absorbent. (i) preparing an aqueous monomer solution comprising at least partially neutralized, monoethylenically unsaturated monomers bearing carboxylic acid groups (α1) and at least one crosslinker (α3); (ii) optionally adding fine particles of a water-absorbent polymer to the aqueous monomer solution; (iii) adding a polymerization initiator or a at least one component of a polymerization initiator system that comprises two or more components to the aqueous monomer solution; (iv) decreasing the oxygen content of the aqueous monomer solution; (v) charging the aqueous monomer solution into a polymerization reactor; (vi) polymerizing the monomers in the aqueous monomer solution in the polymerization reactor thereby obtaining a polymer gel; (vii) discharging the polymer gel out of the polymerization reactor and optionally comminuting the polymer gel thereby obtaining polymer gel particles; (viii) drying the polymer gel particles; (ix) grinding the dried polymer gel particles thereby obtaining particulate water-absorbent polymer particles; (x) sizing the grinded water-absorbent polymer particles; and (xi) treating the surface of the grinded and sized water-absorbent polymer particles; (ia) at least partially neutralizing acrylic acid by mixing acrylic acid with an aqueous solution of sodium hydroxide, thereby obtaining an aqueous solution of the at least partially neutralized acrylic acid; (ib) cooling the aqueous solution of the at least partially neutralized acrylic acid with a cooling liquid in a heat exchanger, wherein the cooling liquid used in the heat exchanger has been cooled in an absorption chiller in which at least a part of the heat of the heated cooling liquid obtained in the heat exchanger is consumed by the evaporation of a refrigerant liquid in a vacuum that is created by the absorption of a refrigerant vapour into an absorbent.