The invention relates to antifreeze concentrates for cooling systems in fuel cell drives, from which are produced ready-to-use aqueous cooling agent compositions having a maximum conductivity of 50 μs/cm, based on alkylene glycols or the derivatives thereof, and containing orthosilicic acid esters of formula (I) wherein the variables R1 to R4 are the same or different and represent C1-C20 alkyl substituents, C2-C20 alkenyl substituents, C1-C20 hydroxyalkyl substituents, optionally substituted C6-C12 aryl substituents and/or glycol ether substituents of formula (CH2—CH2—O)n—R5 wherein R5 represents hydrogen or C1-C5 alkyl and n represents a number between 1 and 5