Fulfilling the promise of green hydrogen

In 2019 there was less than 100 MWe of electrolysers (equipment that uses electric current to break apart water molecules into hydrogen and oxygen gas) installed globally, but today there is close to 1 GWe of operating electrolysis capacity, half of which was added just last year. The growth is set to continue: about 11 GWe of capacity is at an advanced stage of planning for deployment in the next 2 - 4 years, and a huge 480 GWe of capacity has been announced, heralding unprecedented growth in the green hydrogen market over the coming decade.

Most of the hydrogen produced today is used in large-scale chemical and refining plants, usually producing more than 10 tph of hydrogen. This is equivalent to 400 MWth of electrolysis for each large-scale hydrogen consumer. Most industrial applications that use hydrogen require mechanical compression to raise the pressure from the 20 - 30 bar typically provided by the incumbent steam methane reforming process (SMR or ‘grey’ hydrogen), to anywhere between 50 and 200 bar depending on the end-use application requirements. As a consequence, the hydrogen compressor is a critical piece of equipment in the hydrogen value chain. Compression technology has been used and optimised for decades. Most hydrogen compressors operating today are positive displacement machines, primarily reciprocating, which enables high efficiency and high-pressure ratio per stage on low-molecular-weight gases like hydrogen. There are thousands of hydrogen reciprocating compressors operating efficiently and reliably at refineries, petrochemical and chemical facilities (ammonia and methanol), spanning a wide range of power capacities from as low as 100 hp to as high as 20 000 hp (equivalent to approximately 0.1 - 15 MW of energy).

While hydrogen compressors have been around for some time, a new and important requirement has been added more recently. Unlike grey hydrogen – which is produced on a continuous basis – green hydrogen production can be intermittent due to the inherent variability of renewable energy inputs like wind and solar. Consequently, there is a mismatch between the operating requirements of the compressor and the variable nature of the energy input. This article will discuss the main requirements and design considerations for hydrogen compressors paired with electrolysers for industrial-scale intermittent hydrogen production and use. It will also show how companies like Electric Hydrogen (electrolysis OEM) and Neuman & Esser (compression OEM) think about the various tradeoffs at play to provide a solution to customers that is fit-for-purpose to produce zero emission green hydrogen at large scale to decarbonise industrial applications.

Requirements for electrolysis and compression

There are three major economic and operational requirements when supplying compressed green hydrogen to industrial offtakers.

Lowest initial investment

Electrolysis to produce green hydrogen has been historically more expensive than traditional hydrogen production solutions like SMR. Electrolysis OEMs, such as Electric Hydrogen, are combining scale and innovation in the electrolyser stack and plant design to drive costs down and make green hydrogen at competitive economics. It is important that electrolysis OEM and compression OEMs work together to optimise the entire electrolysis system and reach the lowest-cost solution. It is also important to put these investment costs in perspective: all-inclusive electrolysis plants (inclusive of power conversion, and all elements of balance of plant but not additional compression beyond the electrochemical one) range between US$850/kWe,in and US$1700/kWe,in. Compression systems for these plants add between US$50/kWe,in and US$100/kWe,in depending on the desired flow rate, the suction pressure provided by the electrolyser, and the discharge pressure required by the end user. These costs need to come down in order to make green hydrogen a viable alternative to grey hydrogen.

Written by Soufien Taamallah, Electric Hydrogen, and Luiz Soriano, Neuman & Esser.

This article was originally published in the Spring 2024 issue of Global Hydrogen Review magazine. To read the full article, simply follow this link.

Read the article online at: https://www.globalhydrogenreview.com/hydrogen/11042024/fulfilling-the-promise-of-green-hydrogen/