How does one determine what size and capacity to specify for your hydrogen refuelling station? This doesn’t have to be a complicated question. You can start by answering two questions: How much hydrogen do you want to deliver to vehicles every day, or every month, or yearly? And, how many back-to-back vehicle fills do you want to be able to do at the busiest time of the day?
The first question will determine your average hydrogen flow rate. This flow rate is a key design parameter for picking a compressor size, or a liquid pump capacity, depending on how your system receives hydrogen. The key here is to pick a compressor (or other device) that delivers the hydrogen that you need on a continuous or average basis. Trying to size a compressor to meet your peak requirements will result in a larger, more expensive component whose capacity will be under-utilized most of the time. Instead, you want to pick a component that delivers an average amount of hydrogen to support a full day of operation.
The second question will determine the right amount of hydrogen storage to meet your peak requirements. You can use the size of each vehicle tank and the total number of vehicles that you want to fill back-to-back, to figure out the size of the hydrogen storage banks. To do this sizing, first assume that the compressor (or other device) is not available to replenish the storage banks (although at times the compressor may be augmenting the stored hydrogen). Then pick storage bank sizes that allow for the number of back-to-back full vehicle fills that you need at the busiest time of day while maintaining the storage pressure well above the dispensing pressure. The process of properly sizing storage is iterative, as one may initially pick too small or too large a storage system, before finding a size and arrangement of storage banks that is optimal.
At Hyfluence, we use proprietary simulation tools developed in-house by our engineering team to size a hydrogen station’s storage and compression. We start with a storage size and configuration (e.g. 3 banks), and a vehicle tank size and number of back-to-back fills, then run our simulator to perform the vehicle fills while “depleting” our simulated storage. Our simulator also runs simulated compression, based on real-world compressor data, to “replenish” the storage during or after each fill. Then we review the results and, if needed, adjust our storage sizing and/or compression throughput, and re-run our simulation, until we get the results we need. This process results in optimized storage sizing that, combined with the compressor sizing, strikes the right balance between performance and cost.
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