Avtor JS | Foto: stock.adobe.com 2:34 pop ENERGETIKA, Revija

Izziv za vodik sta hramba in transport

Vodik je nekaj časa veljal za potencialno gorivo prihodnosti, a se je naposled umaknil elektrifikaciji. Glavni izziv bolj kot pridobivanje predstavljata predvsem skladiščenje in transport.

Ker je vodik v plinastem stanju izredno razpršen, se metode za shranjevanje in transport zanašajo na povečanje njegove gostote. Kot najlažja molekula ima vodik zelo nizko gostoto, zato en kilogram vodikovega plina zavzame več kot 11 m³ pri sobni temperaturi in atmosferskem tlaku. Za učinkovito shranjevanje sta tako v uporabi dve metodi, vsaka s svojimi prednostmi in slabostmi:

Kompresija – Vodik se stisne pod visokim tlakom. Metoda je energijsko manj zahtevna, a zavzame več prostora.

Utekočinjenje – Vodik se ohladi na izjemno nizke temperature. Metoda je prostorsko učinkovitejša, a zahteva več energije.

Na kratke razdalje je boljša kompresija

Katera je za transport najprimernejša metoda skladiščenja zavisi predvsem od razdalje prevoza in od količine vodika, ki ga je treba prepeljati. Na kratkih razdaljah, do približno 3.000 km, je najcenejša možnost stisnjen vodik , še posebej če so na voljo cevovodi. V nekaterih primerih se obstoječe plinovode za zemeljski plin že prilagaja za prenos vodika, kar še dodatno zmanjšuje stroške.

Pri daljših prevozih v rabi tudi kemični nosilci

Pri večjih razdaljah pa je nekoliko bolj učinkovit prevoz vodika v utekočinjeni obliki, a so pri tem pomanjkljivost izgube, ki nastanejo kot posledica izhlapevanja. Vse bolj konkurenčni so tudi kemični nosilci, kot sta LOHC (tekoči organski hidrogeni nosilec ali angl. Liquid Organic Hydrogen Carrier) in amonijak. Ti so na razdaljah, večjih od 3.000 km sicer učinkovitejši, a dodaten strošek predstavlja razpakiranje vodika iz teh kemičnih nosilcev, saj je energetsko precej intenzivno.

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