Hydrogen and Water: An Engineering, Economic and Environmental Analysis

Abstract

1 AcknowledgementsWe would like to thank Vince Tidwell and his team at Sandia National Laboratories for allowing us to be among the first external users of their Decision Support Model for Integrated Water-Energy Planning. Supporting pre-production software is no easy task, yet their model proved to be a crucial component of the regional water stress analysis. We would also like to thank Erik Schuster and his team at the National Energy Technology Laboratory for compiling much of the data that went into the Sandia model. Darlene Steward and Mark Ruth of the National Renewable Energy Laboratory have been important partners in tying this analysis to the existing frameworks of H2A and the MSM. Executive SummaryWater is a key feedstock to the hydrogen production process. Water is a process input (some, if not all hydrogen will come from the H 2 in H 2 O), and at least as importantly, water is used to cool the process equipment that will make hydrogen. Water is also an input to other lifecycle steps, particularly the generation of electricity.Water is abundant. Even in areas expected to achieve high levels of hydrogen vehicle market penetration, water use for hydrogen production is unlikely to be more than 1.5% of the local freshwater supply. Other uses of water such as agriculture and power production make hydrogen's anticipated use appear trivial.Water is inexpensive. Under reasonable economic assumptions, the cost of purchasing water, water treatment (including capital costs) and disposing of wastewater is expected to comprise less than $0.09 per kg hydrogen.However, it is still important for stakeholders in the hydrogen industry to understand the engineering, economic, environmental and policy issues related to water. In particular, this report addresses two key areas: Technology OptionsThere are two widely available options for water treatment: reverse osmosis and ion exchange. Similarly, there are two classes of process cooling: cooling towers and dry cooling. In general, these technologies face tradeoffs in cost, power consumption, total water input ("withdrawal") and wastewater generation ("discharge"). This report identifies the water purchase and discharge costs at which it makes sense to transition from a low-cost, high-withdrawal technology to a high-cost, lowwithdrawal technology. Water ResourcesIn order to anticipate the need for different water strategies, the stress on water resources and state of water prices in localities of interest to the hydrogen industry were analyzed. It was found that water purchase and disposal prices are not high enough anywhere to be a factor in early-stage hydrogen deployment, but that many locations exhibit risk factors (higher-than-average prices, low industrial water use, or high water stress) that warrant special attention.3

Development of a Life Cycle Inventory of Water Consumption Associated with the Production of Transportation Fuels

“…With the exception of SMR w/CCS process, the cooling and process water consumption requirements for all pathways in Table 22 were confirmed with confidential data from a variety of different sources in the refinery and gas industries. A range of estimates for water consumption factors of the different hydrogen production technologies in Table 22 are provided based on another study (Simon et al, 2010). The WCFs were converted to an energy basis using a LHV for H 2 of 0.114 mmBtu/kg.…”