[ heat exchange ]
Table 2
Equipment installed
Cascade Cooling 28 ° C
24 bays AFC + 6 cooling towers + skids ( 1 pump and 1 PHE )
Cascade Cooling 30 ° C
32 bays AFC + 8 cooling towers + skids ( 1 pump and 1 PHE )
Plot area required ( m x m ) without pump skids
Annual water consumption ( m ³)
Annual electrical consumption ( MWh )
110 m x 18.3 m ( AFC ) + 6 x 10 m x 9 m ( WCT ) 141 m x 18.3 m ( AFC ) + 8 x 10 m x 9 m ( WCT )
90,000 m ³ 63,000 m ³ −30 %
3,650 3,050 −20 %
must be energy-efficient and use as little water as possible . This goal led to the development of the Cascade Cooling solution ( see Figure 1 ).
During cooler to colder weather conditions , when ambient temperatures are significantly lower than the process fluid temperature , the system operates in a closed-loop mode with air fin coolers . This configuration reduces equipment size and the number of fan motors , which operate under variable frequency drives to minimise energy consumption .
In warmer to hotter weather conditions , air fin coolers operate at full capacity , with additional cooling provided by wet cooling towers . This setup , operating in a closed loop with a plate-andframe heat exchanger , further lowers the process temperature while keeping water consumption to a minimum .
Cascade Cooling : a real case study in an arid and hot environment
A recent case study involved designing a largescale green hydrogen production plant with electrolysis capacities of 2 x 200 MWe and 1 x 100 MWe . The project ’ s cooling requirements included :
• Located in a water-scarce area , making water consumption for cooling a concern and driving the project toward a dry-cooled system where possible .
• Cooling water required at 38 ° C , with peak summer temperatures reaching 39 ° C , necessitating some evaporative cooling .
• Below 28 ° C ambient temperatures outside peak summer months , allowing for dry air cooling and large air coolers . However , during peak summer months , temperatures exceed 28 ° C for up to 17 hours a day , requiring a solution for these peak hours .
One option being considered is a fogging system to reduce the ambient air temperature at the cooler inlets , ensuring the coolers remain effective during peak periods . This would require the fogging system to reduce the ambient air temperature from , say , 39 ° C to 28 ° C . The design wet-bulb temperature is 19 ° C , and simulations suggest that this level of temperature reduction is theoretically achievable .
Alternatively , a wet surface air cooler or a closedloop cooling tower in series with the air cooler could be used in peak conditions through Kelvion ’ s Cascade Cooling solution .
The main technical drivers to be considered , in order of preference , are :
• Minimising water consumption due to the scarcity of water resource .
• Minimising electrical consumption .
• Minimising the plot space required for cooling equipment .
Using an ASHRAE database , which provides location-specific annual weather data , including dry-bulb and wet-bulb temperatures throughout the year and the corresponding number of hours
18 Hydrogen Tech World | Issue 18 | October 2024