DOE Annual Progress Report: Water Needs and Constraints for Hydrogen Pathways

[摘要] Water is a critical feedstock in the production of hydrogen. In fact, water and many of the energy transformations upon which society depends are inextricably linked. Approximately 39% of freshwater withdrawals are used for cooling of power plants, and another 8% are used in industry and mining (including oil and gas extraction and refining). Major changes in the energy infrastructure (as envisioned in a transformation to a hydrogen economy) will necessarily result in changes to the water infrastructure. Depending on the manner in which a hydrogen economy evolves, these changes could be large or small, detrimental or benign. Water is used as a chemical feedstock for hydrogen production and as a coolant for the production process. Process and cooling water must meet minimum quality specifications (limits on mineral and organic contaminants) at both the inlet to the process and at the point of discharge. If these specifications are not met, then the water must be treated, which involves extra expenditure on equipment and energy. There are multiple options for water treatment and cooling systems, each of which has a different profile of equipment cost and operational requirements. The engineering decisions that are made when building out the hydrogen infrastructure will play an important role in the cost of producing hydrogen, and those decisions will be influenced by the regional and national policies that help to manage water resources. In order to evaluate the impacts of water on hydrogen production and of a hydrogen economy on water resources, this project takes a narrowly-scoped lifecycle analysis approach. We begin with a process model of hydrogen production and calculate the process water, cooling, electricity and energy feedstock demands. We expand beyond the production process itself by analyzing the details of the cooling system and water treatment system. At a regional scale, we also consider the water use associated with the electricity and fuel that feed hydrogen production and distribution. The narrow scope of the lifecycle analysis enables economic optimization at the plant level with respect to cooling and water treatment technologies. As water withdrawal and disposal costs increase, more expensive, but more water-efficient technologies become more attractive. Some of the benefits of these technologies are offset by their increased energy usage. We use the H2A hydrogen production model to determine the overall cost of hydrogen under a range of water cost and technology scenarios. At the regional level, we are planning on following the hydrogen roll-out scenarios envisioned by Greene and Leiby (2008) to determine the impact of hydrogen market penetration on various watersheds. The economics of various water technologies will eventually be incorporated into the temporal and geographic Macro System Model via a water module that automates the spreadsheet models described. At the time of this progress report, the major achievement for FY2009 has been the completion of the framework and analytical results of the economic optimization of water technology for hydrogen production. This accomplishment required the collection of cost and performance data for multiple cooling and water treatment technologies, as well as the integration of a water and energy balance model with the H2A framework. 22 (twenty-two) different combinations of production method (SMR, electrolysis), scale (centralized, forecourt), cooling (evaporative tower, dry) and water treatment (reverse osmosis, ion exchange) were evaluated. The following data were collected: water withdrawal, water discharge, electricity consumption, equipment footprint, equipment cost, installation cost, annual equipment and material costs and annual labor costs. These data, when consolidated, fit into a small number of input cells in H2A. Items such as capital cost end up as line-items for which there is space in the existing H2A spreadsheets. Items such as electricity use are added to the values that already exist in H2A. Table 1 lists eight potential technology combinations for cooling and water treatment associated with centralized SMR hydrogen production. When water costs are very low, the most economical system is described by row B, however, as water purchase and discharge prices rise, systems with higher water efficiency prevail. Tables 2a, 2b and 2c show the price of hydrogen production as a function of water purchase and discharge price. In table 2a, the technology is fixed. In table 2b, the price is the lowest of the eight available water technology options. Table 2c identifies the chosen technology for the economic conditions. This analysis has shown that at current prices, water is not expected to have a major impact on hydrogen deployment. In previous years work, it was show, qualitatively, that acquisition of water rights (permitting) can present a major issue for any new water user, particularly in highly water stressed areas.

[发布日期] 2009-07-02

[学科分类] 再生能源与代替技术

[关键词] CAPITALIZED COST;CHEMICAL FEEDSTOCKS;COOLING SYSTEMS;ELECTRICITY;ENERGY BALANCE;HYDROGEN;HYDROGEN PRODUCTION;ION EXCHANGE;POWER PLANTS;PRODUCTION;PROGRESS REPORT;WATER;WATER RESOURCES;WATER RIGHTS;WATER TREATMENT;WATER USE