Heat
makes up a large share of overall energy consumption and CO2
emissions globally. To reduce global greenhouse gas emissions sufficiently to
avoid dangerous climate change, the current hydrocarbon fuels used for heat generation
need to be substituted by low-carbon alternatives.  

Fuel
cells and hydrogen could potentially generate low-carbon heat and electricity. Hydrogen
is potentially a credible zero-carbon alternative to natural gas, particularly
if economic low-carbon hydrogen can be produced and delivered using existing
gas network infrastructure. Existing fuel cells have built-in reformers that
produce hydrogen from natural gas, but an alternative fuel such as hydrogen
produced from a low-carbon energy source could be used to power fuel cells in
the future.  

Fuel
cells are not the only technology for heating with hydrogen, but they are the
most prominent because of their electrical efficiency advantage. Similarly,
hydrogen is not the only fuel that can power fuel cells, and most currently
produce hydrogen internally by reforming a supplied hydrocarbon fuel.

In
the industrial sector, possible roles for hydrogen and fuel cell products
include the substitution of hydrogen for natural gas in some processes and the
use of combined heat and power (CHP) technologies. CHP is on-site electricity generation
that captures the heat that would otherwise be wasted to provide useful thermal
energy such as steam or hot water that can be used for space heating, cooling,
domestic hot water and industrial processes. It is currently the largest and
most established market for fuel cells.

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Fuel
cells offer wider energy system benefits for high-latitude countries with peak
electricity demands in winter. Hydrogen is a zero-carbon alternative to natural
gas, which could be particularly valuable for those countries with extensive
natural gas distribution networks, but many national energy system models
examine neither hydrogen nor fuel cells for 
heating. Hydrogen can be used as an alternative to natural gas for space
heating, water heating, and for gas cooking. In homes, hydrogen could be used
to power fuel cell micro- CHP, direct flame combustion boilers (similar to
existing natural gas boilers), catalytic boilers and gas-powered heat pumps. A
variety of larger district heat and CHP devices that use natural gas could also
be redesigned to use hydrogen. It would also be possible to replace a large
number of natural gas processes in industry; for example, hydrogen could be
used to fuel cement kilns, although substantial plant redesigns would be
necessary. From a consumer perspective, there is no difference in the
appearance or operation of hydrogen boilers when compared to their natural gas
equivalents. A direct flame combustion H2 boiler is functionally
identical to the gas boilers installed in Europe and North America to supply
residential central heating, except that it burns hydrogen instead of natural
gas.

Hydrogen
can be produced from fossil fuels, biological material or water. Current
hydrogen production is largely from steam methane reforming, but there is also strong
interest in the electrolysis of ‘green’ hydrogen from water that in the future
would use zero-carbon electricity. Hydrogen is not a sustainable energy vector
unless the production process produces low emissions.

Widespread
consumption of hydrogen for heating would require the production of huge
quantities of the gas. Constructing a pipeline network would likely be more
economic than bulk delivery by freight transport vehicles to supply cities.
Possible routes for achieving widespread pipeline distribution include scaling
up and expanding existing hydrogen networks, constructing entirely new ones, or
converting some or all of existing natural gas distribution networks. Pipe
costs for hydrogen are difficult to generalize as they are heavily influenced by
geographic considerations such as the routing of pipelines and the way they are
trenched and installed in the ground. This depends on factors such as geology,
topography, coordination with other buried electrical or fluid conduits, the
costs of securing the rights to install pipes through private land, etc. On
average, costs for hydrogen pipe infrastructure are estimated to be around 10%
to 20% more expensive than for natural gas.

In
countries with high-carbon electricity systems, fuel cells can reduce carbon
emissions relative to conventional heating technologies. As with financial
savings, CO2 savings are country and site-specific, depending on the
carbon intensity of grid electricity and on the heating system that is
displaced. Fuel cell micro-CHP is the technology with the lowest overall
emissions, currently produces lower emissions than both gas boilers and heat
pumps. Fuel cells also offer significant benefits to local air quality even
when fuelled on natural gas. The process of reforming the fuel at low
temperatures in the absence of air, rather than combusting it, results in lower
emissions of harmful air pollutants, including oxides of nitrogen (NOx), carbon
monoxide (CO) and particulates (PM10). 
Emissions from fuel cells are around a tenth of those from other
gas-burning technologies.

Installation
of a fuel cell is comparable to that of conventional heating, requiring the
skill-sets of a heating engineer and an electrical engineer. Installation can
take as little as a day, and involves relatively little disruption to the
premises. In contrast, heat pumps require more specialized skills. Residential
fuel cells are physically larger than gas boilers, around the size of a large
fridge-freezer, and so they are installed in basements or outside. Apart from
their physical size, fuel cells are relatively unobtrusive. The only moving parts
are pumps and fans so noise levels are similar to boilers. CHP engines can be
significantly louder, although modern sound- proofing reduces residential
systems to around 45 dB. Fuel cells could therefore be suitable for
installation in living spaces if their size can be reduced sufficiently.

One
clear advantage that fuel cells and other CHP devices have is the ability to
operate during a blackout. This became a highly prized selling point as the
Great East Japan Earthquake of 2011 caused lasting power shortages across
Japan, and hurricanes Katrina and Sandy caused extensive power loss in the US.
Provided that the natural gas network is not disrupted, the fuel cell can
provide hot water and sufficient power for refrigeration, a TV, computer and
lighting during an emergency. Similarly, commercial fuel cells continue
operating throughout power outages, enabling shops and offices to continue
functioning as normal.

For
many years, durability was a key issue holding back fuel cells. Stack lifetimes
were around 10,000 h (around 2 years of intermittent operation) for all but
PAFC technology, which proved a serious barrier to practicality and cost
competitiveness. Recent improvements in both PEMFC and SOFC technology,
particularly by Japanese manufacturers, have seen lifetimes improve past the
critical milestone of 40,000 h (10 years).

Being
a newly commercialized technology, fuel cells need to gain public acceptance as
a safe and dependable technology. 
Although the public are familiar with using natural gas and petrol, the
association with hydrogen (flammable and explosive) gives the impression that
fuel cells could be dangerous. In natural gas-fired CHP systems, hydrogen is
generated on-demand and almost instantaneously consumed, so only a fraction of
a gram is present in the system at any given moment. Safety considerations are
therefore very similar to a conventional gas boiler and other electricity-
producing technologies such as solar PV.

The
major barriers to the deployment of hydrogen and fuel cell heating systems are
high costs when compared against alternatives. Upfront capital cost remains a
major hurdle for fuel cells to overcome. The high capital cost of fuel cell
systems is offset by lower running costs which result from lower consumption of
grid electricity. The running costs experienced in one country are not
necessarily transferable abroad because of climatic and social differences.

Hydrogen
may become one of the main energy carriers of the future, because it produces
less local air pollution than fossil fuel based energy, and can be manufactured
from a wide variety of sustainable and carbon-free sources. There is a need to
include hydrogen and fuel cell heating technologies in future scenario
analyses, assessments and for policymakers to take into account the full value
of the potential contribution of hydrogen and fuel cells to low-carbon energy
systems to reduce greenhouse gas emissions from heat provision.

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