Decarbonisation Technology - November 2022

Electrolyser power rating

10,000 kW el. PEM Electrolyser

25,000 kW el. PEM Electrolyser

100,000 kW el. PEM Electrolyser

H 2 production

180 kg/h

450 kg/h

1,800 kg/h

Waste heat at 80 º C

2,500 kW

7,500 kW

25,OOO kW

Steam output 5barg (170°C)

5,100 kg/h

15,OOO kg/h

49,200 kg/h

Steam compressor driver power

1,OOO kW

2,600 kW

8,400 kW

COP (Coefficient of Performance)




Table 2 Overview of possible performance figures for a steam generation system, applied to commercial, high-efficiency PEM electrolyser waste heat streams

stage with an individual load control device, the inlet guide vane mechanism. Assuming as starting conditions typical PEM electrolyser waste-heat temperatures, Atlas Copco Gas and Process compressors can efficiently pressurise steam up to 20 bar(g). Using water steam not only as a heat carrier but also as a working fluid in a heat pump offers additional beneficial aspects: water is a fluid with no negative aspects, it is abundant, low cost, and neither toxic nor flammable. In addition, the resulting COP and possible output temperature are very high in comparison with other heat pump technologies and commonly used refrigerants. Table 2 shows typical steam-compressor- system parameters, assuming typical PEM electrolysers of 10, 25, and 100 MW power

ratings as the waste heat source. The waste heat at 80°C is turned into 170°C/5 barg steam, which represents a typical utility-steam level in the industry. With COPs higher than 3, the system enables efficient upcycling of the waste heat. As a rule of thumb, the steam compressor uses 10% additional power to enable full utilisation of the unavoidable by-product. Especially when the electrolyser is part of a larger production facility, such as refineries or chemical plants, steam, at the right pressure, can simply be fed into the existing distribution network. Furthermore, it enables the use of electrolyser waste heat in existing high- temperature district heating networks in a simple way. Proven turbocompressor technology The optimisation of industrial heat pumps, whether using refrigerants or water steam, is a system with a number of variables. Continuously operating production processes in industry require maximum reliability and economy, for example, while turbomachines are vital for larger outputs. Integrally geared turbocompression has long been a proven technology, and it comes with the desired high performance, reliability, and cost attributes. Designed to be flexible, it can have arrangements of up to eight individual compressor stages on a gearbox (see Figure 8 ), as well as the possibility of multiple interstage cooling. And especially in the case of heat pumps with large temperature lifts, an integrally

Figure 8 Cross-section of an integrally geared compressor core


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