A Hydrogen-based Microgrid where Electrolyzer Hydrogen is replaced by Hydrogen from Alternative Sources (Methanol-Reformation)
Abstract
Key desirables when planning for a microgrid, including a microgrid that is hydrogen-based are — to achieve the right balance in demand and supply, to achieve higher energy efficiency and to have reliability and resiliency.
Problem
When the primary generator of energy in a microgrid is Solar or Wind, the very nature of such generators characterized by load transients, switch on/switch off events and idling conditions [1], makes it challenging even for a PEM Electrolyzer (the most popular electrolyzer type due to its durability) to perform optimally. A PEM Electrolyzer performs better than Alkaline Electrolyzers under dynamic conditions but it must still be accompanied by a power conditioning system if its performance is not to be compromised by inherently occurring transients that can lead to failures with the downstream Fuel Cell [1]. A power conditioning system for this can be complex, cumbersome and costly.
The problem can be alleviated by augmenting with an intermediate Hydrogen-storage system which will add further costs to the end-to-end system
Our Solution
Designing a microgrid ab initio, we at Hydrozen2050, use a completely different approach for setup of a hydrogen-based microgrid.
We recommend a Fuel Cell supplied with a constant and smooth stream of renewable Hydrogen, that is produced by our Methanol-Reformer system, then compressed and fed directly into the Fuel Cell.
Since in our system Hydrogen [2] is produced constantly with a smooth flow rate, the integration with the downstream Fuel Cell reduces to a simple hydrogen pressure control system. This is in stark contrast to a strongly coupled subsystem, with high nonlinearity and complex dynamic processes, required to mitigate the variability of power fed to a PEM Electrolyzer. Even then, a hydrogen pressure control system is still required to deliver the electrolyzer-produced hydrogen to the Fuel Cell
So in comparison, our system is significantly less complex, less cumbersome and much cheaper
Details
Regardless of the source of hydrogen that feeds the Fuel Cell — whether the source is a PEM Electrolyzer or a Methanol-Reformer — in both cases, hydrogen pressure control system is still required.
It is important to point out here that in our case the Methanol-Reformer is a completely external and independent system to the Fuel Cell. It is known that the cost of the reformate within the Fuel Cell is a significant factor contributing to higher cost (~30% of the total system unit manufacturing and service cost of a Fuel Cell) [3], a cost which we avoid completely.
The purpose of this hydrogen pressure control system (and air/oxygen inlet pressure system) is crucial to ensure that the inlet pressure be carefully maintained within the designed operating range [4]. This applies regardless of whether the Fuel Cell is a low-pressure or high-pressure Fuel Cell. Whereas a high-pressure Fuel Cell is desirable when higher power density is desirable (eg in an FCEV), low-pressure Fuel Cell comes with a benefit that less sealing, lower probability of membrane fracture and lower parasitic losses are observed [5] (eg benefits for stationary applications)
Conclusion
To gain the benefits of clean and reliable power, the planning of a microgrid invariably includes a Fuel Cell. A Fuel Cell offers reliable generation as it can run continuously 24 hours a day, seven days a week, 365 days a year (as long it has a fuel (ie Hydrogen)— supply). Providing a constant supply of renewable Hydrogen is not practically possible with a variable energy source like Solar or Wind but with a Methanol-Reformer it certainly is
References
3. Fuzzy control of hydrogen pressure in fuel cell system — ScienceDirect
4. Dynamics of Low-Pressure and High-Pressure Fuel Cell Air Supply SystemstryHLP4.dvi (umich.edu)
5. Fuel Cells and Hydrogen Production — A Volume in the Encyclopedia of Sustainability Science and Technology, Second Edition, Lipman & Weber (Editors), Springer, 2019, pp 128
6. Fuel Cell Operating Conditions (fuelcellstore.com)
7. Hydrogen Pressure Control in Hydrogen Fuel Cell System｜Kao Lu (genndih.com)
[2] Hydrogen produced is renewable — Blue Hydrogen if use common methanol with CCU/S and Green Hydrogen if use e-Methanol / Bio-Methanol
[3] Fuel Cells and Hydrogen Production — A Volume in the Encyclopedia of
Sustainability Science and Technology, Second Edition, Lipman & Weber (Editors), Springer, 2019, pp 128
[5] Dynamics of Low-Pressure and High-Pressure Fuel Cell Air Supply Systems tryHLP4.dvi (umich.edu)
