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British researchers suggested using heat pumps to preheat hydrogen to very high temperatures, which they say could reduce its need by more than 20%. It is also claimed that the process could reduce the energy demand of European industry by around 200 TWh per year.
Using heat pumps to preheat industrial hydrogen (H2) systems could reduce their need by more than 20% and cut the cost of process heat for heavy industry by more than 10%, according to new UK research. United.
The group of researchers, led by the University of Leeds, states that the use of heat pumps to preheat hydrogen at very high temperatures could reduce European industry demand by approximately 200 TWh per year, with a reduction of 40 TWh per year. year only in the UK.
In the study “ Reducing industrial hydrogen demand through preheating with very high-temperature heat pumps ”, published in Applied Energy , the scientists state that their conclusions They derive from recent advances in the field of thermomechanical energy storage, which allow heat pumps to operate at very high temperatures.
“Heat pumps have normally been considered for low-temperature applications in buildings, district heating and industry, with maximum temperatures of up to around 75-100ºC”, the study states, adding that the combination of heat pumps with storage of Thermal energy has allowed scientists to reach an operating temperature of 500ºC with argon as the working fluid.
The researchers say that while heat pumps are far from reaching the extreme temperature required by many industrial thermal processes, such as blast furnaces, they can still be used to preheat combustion air or hydrogen. The article evaluated the performance of preheating at temperatures of 300-500ºC, finding greater cost savings at the highest point.
“For a given combination of capital invested in the electrolyser and electricity price, the relationship between relative cost savings and temperature is linear in the temperature range of 300 to 500ºC”, they explain. “Adding a reverse Joule-Brayton heat pump to a green hydrogen-based heating system brings cost savings when electricity prices exceed £5 ($6.35)/MWh. With electricity prices above £30/MWh and electrolyser costs above £400/kW, cost savings exceed 5% when preheating to 300ºC and 8% when preheating to 500ºC.”
Heat pumps based on the reverse Joule-Brayton cycle are commonly used in small-scale applications. They typically draw ambient air into a compressor and then convey the hot compressed air to a heat exchanger where it is cooled, thus delivering heat to a water-filled radiator or hot water system. Finally, it expands the air through a reciprocating expander until it reaches atmospheric pressure and expels it to the atmosphere.
The scientists explained that the cost savings guaranteed by this heat pump system are possible in part due to the fact that heat pumps absorb heat from the environment and therefore reduce the demand for electricity. In the proposed system configuration, the group assumed that the heat pump transfers heat from a water source, such as mine water, to an industrial plant. The greatest cost savings is related to the use of less fuel, hydrogen in this case, which is possible thanks to its preheating.
“Heat pumps appear to be a lower cost preheat option than electric boilers at electricity prices above around £25/MWh, with levelized cost savings over the electric boiler option reaching around £4 % at electricity prices above £130/MWh,” the academics explain. “However, the question of whether the savings from using heat pumps outweigh their added complexity requires further investigation and needs to be considered on an application-by-application basis.”
According to them, their work could help decarbonise the global economy, as process heat that can be used by heat pumps accounts for around 11% of global energy demand. |
