From: Essential Information <ei@igc.apc.org>
Newsgroups: sci.energy
Date: 31 Dec 92 13:54 PST
Subject: Re: Energy Ideas - HVAC-2
Nf-ID: #R:cdp:1466300134:cdp:1466300143:000:4568
Nf-From: cdp.UUCP!ei    Dec 31 13:54:00 1992



ON THE HORIZON: FUEL CELLS

Fuel cells provide both heat and electric power without burning
fuel. Since they operate at relatively low temperatures and use
clean fuels, these cogenerators emit far less pollution than
conventional fossil fuel electricity sources. In addition, fuel
cells attain higher efficiencies than typical cogeneration
facilities (over 80 percent). 

Power from Electrochemical Reactions

Though a fuel cell does not burn fossil fuels, it consumes the
fuel in an electrochemical reaction which produces electricity
directly. A fuel cell consists of three parts: the fuel
processor, the power section and the power conditioner (see
diagram below). In a natural gas fuel cell, the fuel (methane) is
mixed with steam in the fuel processor. The chemical reaction
between the two gases yields a gas consisting of hydrogen, carbon
dioxide and trace amounts of nitrogen oxides. This gas is moved
to the power section, where an electrochemical reaction takes
place between the hydrogen and oxygen in air. This reaction
produces direct current (dc) electricity, steam and heat. The
steam is returned to the fuel processor to continue the cycle.
The power conditioner transforms the current into alternating
current (ac) which can be used on-site.

Types of Fuel Cells

Fuel cells are classified by the electrolyte they use. An
electrolyte is a non-metallic substance which can conduct
electricity. In the power section, the electrochemical reaction
occurs in the presence of an electrolyte, which conducts the
electrons yielded by the reaction toward the power conditioner.
The five types of fuel cells are: alkaline, which use potassium
hydroxide as the electrolyte; phosphoric acid; molten carbonate,
which use a liquid alkali carbonate; solid oxide, which use rare
metal oxides; and solid polymer, which use a polymer membrane as
the electrolyte. Currently, only phosphoric acid fuel cells have
been used commercially, because phosphoric acid is the only
common stable acid which will not react with either hydrogen or
oxygen.

Advantages of Fuel Cells

The main advantage of the fuel cell is the reduced emission of
air pollutants. According to an article in the May 22, 1992 Los
Angeles Times ("The Natural Gas-Powered Fuel Cell System," p.
D1), a natural gas fuel cell emits only 1,130 pounds of carbon
dioxide and 0.02 pounds of nitrogen oxide per megawatt-hour
(MWh), while a conventional power plant (presumably coal-fired)
emits 1,485 pounds of carbon dioxide and 5.74 pounds of nitrogen
oxide. The reduction in carbon dioxide emissions may be
attributed to both a slightly higher electricity generation
efficiency (42 percent as opposed to 34 percent for combustion)
and the use of natural gas instead of coal, which contains less
carbon per unit of energy. The reduction in nitrogen oxide
emissions may be attributed to the lower operating temperature of
the fuel cell as compared to a conventional power plant. In
addition, the use of natural gas eliminates emissions of volatile
organic compounds (VOCs) and sulfur dioxide, which lead to acid
rain.

Other advantages make the fuel cell a promising energy source.
According to the Southern California Gas Company, fuel cells
provide a constant, uninterrupted energy flow, since the cell
does not experience the power fluctuations typical of a utitlity
grid. The fuel cell is easy to operate and maintain, since it has
fewer moving parts, like turbine blades, than conventional power
systems. In addition, the fuel cell is modular, and its size can
be easily increased when growing demand requires more power.

CASE STUDY:

Fuel Cell Installation atop Office Building
In 1992, a 200-kW fuel cell was installed at the South Coast Air
Quality Management District (SCAQMD) headquarters in Diamond Bar,
California. This fuel cell is the first of ten which will be
installed, owned and operated by the Southern California Gas
Company. In this agreement, SCAQMD has agreed to purchase the
natural gas for the fuel cell; all of the electricity is used
on-site, and SCAQMD receives a 10 percent discount on its
electricity consumption. The fuel cell also provides all of the
building~s heat. Ranji George of SCAQMD stated that the agency
has a responsiblity to assist in the integration of technologies
which will lead to reductions in air pollution, and thus agreed
to test the fuel cell. He reported that the fuel cell has run
continuously without any problems since installed.(Contact:
Michelle Bagley, Southern California Gas Company, 555 W. Fifth
Street, Los Angeles, CA 90013, (213) 244-2544.)


Newsgroups: sci.energy