Renewable, Hydrogen-Based Energy For Isolated Communities
Glenn Rambach, Desert Research Institute (left) and David Haberman, President,
DCH Technology, Inc.
The U.S. Department of Energy (DOE) has identified
isolated communities as a viable site option for demonstrating the practicality
of integrated, renewable, hydrogen-based, utility power systems. DOE has
a mandate to pursue this goal as part of the Hydrogen Futures Act of 1996.
The [U.S.] State of Alaska is a candidate for such integrated demonstration
projects because of its exceptional vulnerability to fossil fuel price fluctuations
and its environmental and energy infrastructure logistical challenges.
These DOE-led initiatives are directly pertinent
to meeting the energy needs of isolated communities worldwide by providing
hydrogen energy system designs that can autonomously power isolated communities
with uninterruptible renewable energy. Other candidate customers for such
renewable power are military posts, remote mines, and remote autonomous
The technological building blocks of a renewable
hydrogen energy system have now reached a state of maturity that permits
responsible planning. The implementation of such systems do not require
scientific breakthroughs but are engineering, fiscal, and public policy
challenges. The demonstration of integrated hydrogen energy systems in recent
years in the United States has resulted in a systems engineering data base
that can form the foundation of the next generation of energy system developments
There are two key benefits that would result
from the implementation of a prototypical, uninterruptible renewable energy
Various system elements are discussed below.
- A generic design optimization algorithm that matches an arbitrary renewable
energy source profile with an arbitrary community load profile with the
right amount, and type of storage (this can be generalized for any energy
storage process and medium); and
- A generic control system optimization algorithm that provides electricity
to the customer at the lowest cost, based on temporally varying source
and load conditions.
Primary Power Production
The primary power production installation must
be overbuilt in peak capacity to permit simultaneous load following
and stored energy production. The principal criteria that define the primary,
renewable power source, require:
Wind TurbinesThis is the most mature renewable
technology that permits small-scale, and incremental installation. The current
and expected capital and installation costs for wind turbines make them
the most attractive choice for most potential sites. Quiescent periods may
last for days to weeks. Wind turbines rated for arctic use are currently
Solar PhotovoltaicA maturing renewable
technology whose capital costs are several times higher than wind turbines.
However, such costs are expected to fall to a competitive range in five
to 10 years. Under certain conditions of regional power value and resource,
solar PV can be the technology of choice. Quiescent periods would generally
follow a diurnal cycle.
Micro-HydroelectricUnder the conditions
where an adequate flowing water resource is available, where it is intermittent
(regularly spaced rain or monsoon episodes), and where topography, or other
constraints prohibit the use of pumpedor other reservoirhydroelectric
storage, micro-hydroelectric power production with the type of energy storage
systems considered here can be appropriate.
Low-Dynamic-Pressure (q) Water TurbinesGiven
the conditions in the section above, and intermittent, low-gradient river
flows, submerged water turbines with the type of energy storage systems
considered here can be appropriate.
- the source to be intermittent;
- the average source power to be adequate enough to technically and economically
justify installation of an autonomous system; and
- the maximum credible quiescent period to be within a range that permits
the use of a realistic, economically viable energy storage system.
Energy storage capacity, to first order should
be sized for the maximum credible period of quiescence for the primary power
production system, and for the average load. There are several different
possible energy storage technologies, with varying degrees of maturity,
cost, and scaleability, they are: hydrogen-fuel cell, hydrogen-ICE gen,
halogen fuel cell, Zn-Air fuel cell, Zn-FeCN fuel cell, flywheel, compressed
air, pumped hydro, and battery.
This discussion will be confined to hydrogen-based
energy storage methods. As such, all hydrogen energy storage possess three
basic elements: (1) a primary power-to-hydrogen conversion system (hydrogen
production), (2) a hydrogen storage system (storage), and (3) a hydrogen-to-electricity
conversion system (electricity production).
Hydrogen Production Via Electrolyis
Potassium hydroxide (KOH) electrolyzers are
commercially available in two basic configurations: low-pressure unipolar
and intermediate-pressure bipolar. Both types are attractive methods of
hydrogen production for remote power systems. Under certain conditions,
the bipolar system may provide hydrogen elevated pressure, potentially up
to the storage pressure, reducing or removing the requirement for a compressor.
The current capital cost for KOH electrolysis systems is high, but the potential
for economy of scale improvements is promising.
Solid polymer electrolysis is an emerging, solid-state
method of hydrogen production that should have capital costs that evolve
similar to PEM fuel cells. As the costs decline, this will be an attractive
method of hydrogen production because of its simple, solid-state configuration
and its ability to provide hydrogen at intermediate pressures.
The scale of the hydrogen storage system in
remote, renewable power systems is directly proportional to the maximum
credible quiescent period of the renewable resource and the average load.
It is this property that makes flowing electrochemical storage methods more
attractive than batteries in remote applications of renewable energy with
long periods of stored energy conversion. In these systems, the power conversion
and energy storage hardware are separate, requiring only the size of the
storage hardware (generally least costly) to fit the quiescent power production
conditions. Intermediate-pressure, 100 to 500 psi, gas vessels are a good
choice for most small community power systems. The expected costs and required
system volumes are reasonable. Where space is premium, or where the storage
system is also supplying hydrogen for transportation applications, high
pressure, 500 to 3,000 psi, or low-pressure hydride systems may be required.
Hydrogen-ICE-Generator SetAn electrical
generator driven by an internal combustion, reciprocating engine (ICE),
with a high compression ratio and lean operation* can provide electricity
production with efficiencies similar to a fuel cell. The production system
would have to have an efficient turn-down ratio that matches well with the
temporal load profile. The key advantage to a hydrogen-ICE genset is the
very low near-term capital cost relative to the current cost of fuel cells.
This leaves a cost window of opportunity while fuel cell costs
decline. The primary environmental concern would be the small NOx emission
from nitrogen fixation. However, it is unlikely that this type of power
system would be used in a NOx nonattainment area.
Hydrogen Fuel Cell
Phosphoric Acid Fuel CellCurrently available
in 200-kW units integrated with a natural gas reformer. The reformer is
not necessary for remote hydrogen stored energy applications. The PAFC operating
temperature in excess of 150°C in a 200-kW unit permits cogeneration
of utility heat, but also requires long start up times. Long start up times
mean that the PAFC would have to idle even while stored electricity
is not necessary.
Proton Exchange Membrane Fuel CellCurrently
205-kW units have been integrated into buses for use with neat hydrogen.
A hydrogen PEMFC could operate with short (several seconds) start up and
shut down times. The primary issue for including a PEMFC in a remote, stationary
power application is the capital cost.
Regenerative Fuel CellSolid polymer regenerative
fuel cells are electrochemical devices that perform electrolysis electrochemistry
when current is applied to its electrodes, and perform electricity production
when hydrogen and air are applied to its electrodes. Current cost are high
and system sizes are small, but if RFCs can be manufactured at a lower combined
cost than electrolyzers and conventional fuel cells, then this would be
the preferred technology.
A large fraction of the worlds population
has yet to benefit from the use of utility electricity. These power systems
can be a fully sustainable electrical resource in numerous isolated locations
in the world where the following conditions are met:
The regions of the world where these requirements
are met include remote Alaskan, Canadian, Russian, and other communities,
insular islands, remote military installations, remote mines, and remote
- A high regional value for electricity;
- A reasonable, intermittent renewable resource;
- No electrical power grid available;
- The unavailability of pumped hydroelectric, flywheel, or compressed
air energy storage; and
- Stored energy resource required for more than a day.
*Suggested and developed by Lawrence Livermore National Laboratory,
©1997. All Rights Reserved. A Publication of
the National Hydrogen Association.
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