The Energy-Water Nexus, the intersection of our energy economy with water availability and demand, affects nearly every aspect of our lives from energy availability and disruption to water availability for food production, drinking, and industrial productivity. In many parts of the US, water scarcity already is a key consideration both for management of current systems as well as for planning of future investments. And water scarcity is expected to increase for the foreseeable future.
In the US, a power generation energy transition is underway driving toward lower carbon intensity technologies. The latest EIA Annual Energy Outlook forecasts growth of electricity from renewable and gas-based power while coal and nuclear are expected to decrease and level off. Coal and gas plants will increasingly be pressured to decarbonize further while improving flexibility with increased, nondispatchable renewable generation on the electricity grid. This decarbonization may come in many forms, for example: carbon capture utilization and storage (CCUS), fuel switching from coal to biomass or from natural gas to hydrogen (H2) or optimizing asset utilization through water treatment and heat rate improvements.
Both CCUS and fuel switching to biomass or H2 will increase water intensity of fossil power generation. For the H2 case, steam methane reforming currently accounts for more than 95% of US production. An alternative, fossil based H2 production process is coal/biomass/waste gasification. Both can be decarbonized with the addition of CCUS; however, this will require power or heat to drive it, likely from a combustion source that will require cooling and water to do so. With the costs of solar and wind power decreasing, there is increased interest in a renewable-based approach to H2 production. In this process, the renewable electricity drives an electrolysis unit that splits water into H2 and O2. This process would also require water as a primary input.
CCUS viability depends on several factors such as geological suitability, cost, and permitting; nevertheless, one potential consideration is the extraction of water from the subsurface, enabling increased storage capacity and reducing the areal extent of CO2 and pressure plumes. The total dissolved solids (TDS) concentration of extracted brine is dependent on the geologic formation in which the CO2 is being injected; however, Department of Energy’s Office of Fossil Energy (FE) solicited for projects to develop technologies that could treat waters with an average of 180,000 ppm TDS in FY14 (DE-FOA-0001095) and FY15 (DE-FOA-0001238) and in conjunction with FOA DE-FOA-0001260 which was specifically focused on integrated brine extraction storage tests (BEST). These projects found that while there were many innovative technologies, it was not possible to commercialize these technologies given a lack of market incentive. Nevertheless, as CCUS becomes more prevalent, treating CCUS brines could provide a source of treated water that can be used at the plant or within a regional ecosystem for value-added purposes such as agriculture and municipal drinking water and as an offset to the use of fresh water.
Deadline: Jan. 29, 2021