Water Recovery From Hydrogen Fuel Cells and Other Energy
Production Systems [Project #4139]
ORDER NUMBER: 4139
DATE AVAILABLE: April 2011
PRINCIPAL INVESTIGATORS:
Paul Westerhoff, Jonathan Posner, Kiril Hristovski, and Juan Tibaquirá
OBJECTIVES:
The overall project goal was to assess the feasibility of integrating fuel cell technologies
into the toolbox of options for municipal water providers. The specific objectives
included the following:
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Quantifying the net water yield, water quality, and net energy output from different
types of fuel cells
Investigating the impacts of proton exchange membranes (PEMs), fuel cells, and
electrode materials on water quality
Determining if fuel cells can be operated to maximize water production instead of
energy production
Assessing if additional fuel cell water treatment is necessary to serve as potable water
Developing recommendations for the water industry to explore fuel cells as major
sources of water and as means to decrease energy consumption
BACKGROUND:
Society needs increasing amounts of both water and energy. However, because both
water and energy are interconnected a water-energy nexus has emerged. This project
attempts to look into the future to identify opportunities for the water industry around this
water-energy nexus where pure water may be a by-product of energy production. Two
specific scenarios are considered. First, hydrogen fuel cells may provide an opportunity
for decentralized water and power production. Second, recovery of water from thermocooling systems may provide an opportunity to recover desalinated water.
APPROACH:
To accomplish the above goal and stated objectives, the project was organized into the
following six tasks:
1. Review literature (Task 1)
2. Organize a workshop to investigate linkages between new sources of water and
energy production (Task 2)
3. Evaluate water collected from energy production systems. This includes comparing
analysis of water quality from hydrogen fuel cells operated in several laboratories
across the United States (Task 3A) and comparing those results to design and conduct
tests with hydrogen fuel cells in the project team’s laboratories (Task 3B). This led to
©2011 Water Research Foundation. ALL RIGHTS RESERVED.
analysis of water from field sampling of high temperature energy production systems
(internal combustion engines, molten carbonate fuel cells, cooling towers) (Task 3C)
4. Evaluate treatment requirements for water collected from energy production systems
(Task 4)
5. Comparison of technologies for producing high quality water as related to energy
production (Task 5)
6. Develop recommendations for the water industry (Task 6)
RESULTS/CONCLUSIONS:
The workshop was useful at validating the project team’s approach of exploring water
recovery from energy production systems. The workshop participants agreed that water
quality and yield from novel energy and water systems should be considered as a
contributor to the overall water balance in the future. The water industry should follow
trends in energy production and cooperate with energy partners to identify unique
opportunities to produce high quality water from energy production systems. Use the
energy production as the “water treatment system”. Because the amount of embedded
water in per capita energy usage is lower than per capita water consumption today, water
recovery from energy systems should be considered as an approach to recover “high
quality water” for direct potable consumption.
Water quality results obtained from the lab-scale hydrogen fuel cells, a residential-scale
PEMFC (1kW), and a commercial-scale molten carbonate fuel cell (250 kW) led to the
several key conclusions. Generally, water quality from hydrogen fuel cells easily meets
USEPA regulatory and WHO guidance levels for drinking water. The conductivity of the
fuel cell waters was low (< 50 µS/cm) compared to tap waters, which are often > 500
µS/cm. The presence of certain anions (e.g., fluoride) and TOC in PEMFCs was shown
to be caused by degradation of the fluorinated-organic membranes. The levels of
regulated and non-regulated semi-volatile, volatile, and PAH trace organics were below
detection limits in fuel cell waters. The presence of certain metals (aluminum, nickel,
lead) was attributed to corrosion of tubing in the fuel cells. This could easily be avoided
for potable consumption by using alternative tubing materials.
The quantity of water produced from laboratory and residential-scale PEMFCs was
assessed. The results from the lab scale fuel cell show that the collection percentage is
higher when the self-humidified membrane is employed. This is because of the lower fuel
cell operating temperature used, which causes the fraction of liquid water exiting the fuel
cell to be greater. The experiments with the commercial PEMFC showed that is possible
to recover ~ 8% of the total theoretical water produced without any external condensing
system. Cooling systems can increase the water recovery to ~ 70% of the theoretical
water yield. Thus fuel cell systems can provide between 0.05 and 0.3 L/kWh, which is in
the range of per capita water human water consumption (2L per day internal and 5 L per
day for cooking) to be supplied from typical daily per capita energy usage (on the order
of 30 kWhr).
Water from internal combustion engines and cooling towers were collected using an
apparatus designed and fabricated specifically for this project (a thermo-electric cooling
©2011 Water Research Foundation. ALL RIGHTS RESERVED.
system). All the internal combustion engine samples had organics present (6 to >300
mgTOC /L). The lowest TOC samples were from well operating gasoline engines with
catalytic converters and a natural gas auto. The highest TOC was from a mobile gasoline
powered electric generator that produced unacceptable water for drinking water purposes.
The research confirmed that water could be recovered from internal combustion engines.
The research showed that water of very low conductivity (below 20 µS/cm (~10 mg/L of
TDS) could be recovered from cooling towers, thus demonstrating their potential to serve
as desalination treatment systems. The presence of organics in the condensed water
could be microbial related or antiscalants added to the cooling water system.
Treatment of recovered fuel cell water is probably not required if appropriate plumbing is
used. Improvements in fuel cell membrane properties (i.e., increased lifetime with
decreased membrane degradation) would further improve water quality. If treatment is
desired, existing technologies are currently available. A water energy ratio (WER)
concept was developed that can be used for fuel cells, power generation, or any process at
the water-energy nexus to readily compare the embedded water and energy content of
different products.
APPLICATIONS/RECOMMENDATIONS:
Energy generation is becoming increasingly decentralized (e.g., solar panels), and it may
be reasonable to consider decentralization of high-quality water production. In many
regards customers already are doing significant amounts of decentralized water treatment
(e.g., under sink treatment systems, softening, reverse osmosis, private wells, etc). If a
future hydrogen economy emerges, as forecast by the U.S. Department of Energy, there
will be considerable amounts of decentralized power generation using hydrogen,
including at personal residences. Hydrogen fuel cells for on-site power production
eliminate on-site carbon dioxide emissions and 1.5 to 15 L of very high quality water per
day for a typical person at a residence can be obtained. The range is dependent upon the
ability to recover water exiting the fuel cell.
This project hopes to provide utilities with a basic understanding of opportunities that
exist at the water-energy nexus to obtain “new sources of water” at the point of energy
generation. In addition to hydrogen fuel cells, cooling towers located on buildings or at
power plants evaporate water as a means of thermal exchange. This evaporation process
separates very clean water from saltier blow-down water. It may be possible to collect
condensate or condense vapor at these sites, thus allowing cooling towers to effectively
act as “water desalination systems”.
This project should be viewed as a mechanism to understand and begin exploiting the
water-energy nexus to benefit the water industry. Water research agencies should reinitiate collaborative funding opportunities with EPRI and other partners. This project
also brings to light the opportunities to provide very high quality water for potable water
through on-site (decentralized) water production. The water energy nexus should not be
viewed as only involving consumption of water and energy, but also as an opportunity to
recover water during the production of energy.
©2011 Water Research Foundation. ALL RIGHTS RESERVED.
Increasingly potential benefits are becoming available for co-locating large power and
water systems. Today, this involves co-location of power production and desalination
facilities to utilize low-grade waste heat to reduce energy consumption during
desalination. In the future, it may be logical to “harvest” water from power generation
facilities, be they thermo-electric cooling systems, large scale fuel cells, or internal
combustion engine sources. A key current limitation lies in water recovery systems.
This will require advances in efficient capture of both water aerosols (droplets) and water
vapor. While some of the research needs require basic science advances before being
realized in the 5–10 year time horizon, it is critical that the water industry stay involved
in the water energy nexus and recognize opportunities to “produce” new sources of water.
©2011 Water Research Foundation. ALL RIGHTS RESERVED.