First test of a brand new technology21 September 2001
FuelCell Energy has started up a new kind of power plant based on a DFC/T 250 kW direct fuel cell integrated with a Capstone modified type 330 microturbine. The significance of this particular fuel cell is that needs no external source of pure hydrogen – it generates its own from natural gas.
The test, the first of its kind, is being funded by the US Department of Energy through its Office of Fossil Energy. The co-operative agreement is managed by the National Energy Technology Laboratory as part of the DOE's Vision 21 programme.
An objective of the programme is to develop power plants that would generate electricity with net efficiencies approaching 75 per cent (with natural gas), while producing SOx and NOx emissions of less than 0.01 lb/million BTU. If achieved these levels would be significant improvements over conventional power plants, which are 35–60 per cent efficient and produce emissions of 0.07 to 0.3 lb/million BTU of these gases. The NOx and SOx emissions from the prototype system are anticipated to be better than Vision 21 goals because of the non-combustive features of the DFC/T power plant. The expected high efficiency of the plant should also result in a 40–50 per cent reduction in CO2 emissions compared to conventional power plants.
At the core of this power plant design is FCE’s commercial DFC fuel cell technology. The system combines the potential fuel savings and positive environmental attributes of the DFC with the Capstone non-fired gas turbine and a network of heat exchangers. Features of the DFC/T system include: high efficiency, minimal emissions, simplicity in design, direct reforming internal to the fuel cell, no pressurisation of the fuel cell, independent operating pressure of the fuel cell and turbine, and potential cost competitiveness with existing combined cycle power plants but at much smaller sizes.
The test programme
The DFC/T power plant began operating in July this year, and the test programme is expected to last several months. The power plant is designed to operate in a dual mode: as a standalone fuel cell system or in combination with the microturbine. Hot gas generated by the fuel cell drives the modified microturbine to generate electricity. This proof-of-concept demonstration should provide information to aid design of a 40 MW DFC/T power plant that can approach the 75 per cent efficiency goal as specified by the Vision 21 programme, as well as serve as a platform for a high efficiency DFC/T in smaller sizes for retail power applications.
“The commencement of operation of this 250 kW fuel cell and microturbine demonstration is very exciting for us,” said Jerry D Leitman, president and CEO of FuelCell Energy. “Such a high efficiency, low-emission system represents a potentially powerful addition to our product line and opens up another innovative choice for high efficiency generation of both retail and wholesale power.”
“We are pleased at the progress of this joint project and believe there is great potential in very high efficiency fuel cell/microturbine systems. This project takes advantage of the ultra-low emissions of both technologies,” said Dr Ake Almgren, president and CEO of Capstone Turbine.
“Our Vision 21 programme aims to integrate multiple advanced technologies in order to create systems that achieve breakthrough improvements in performance and cost. Fuel cell-turbine integration is a key part of that strategy,” said NETL fuel cells product manager, Dr Mark Williams. “The data and the experience gained in start up, transient and continuous operation of the power plant will be incorporated into the conceptual design of larger MW-scale power plants suitable for inclusion in a Vision 21 system.”
The FuelCell technology
The key reaction in every fuel cell involves hydrogen and oxygen. Hydrogen is supplied at the anode, oxygen at the cathode. The two gases, which in chemical terms have enormous ‘affinity’, migrate towards each other ; the hydrogen is ionised by the electrolyte, causing an electric potential to develop, before combining with the oxygen to form water. One difference between types of fuel cells is how the hydrogen is produced. Some fuel cells require pure hydrogen. Others have to make it externally in a “reformer”. FuelCell’s product however runs on standard pipeline natural gas. The company’s innovation is the discovery of a way to use the heat generated by the fuel cell to extract hydrogen from natural gas. Hydrogen is produced directly inside the fuel cell, where it is immediately consumed in the reaction.
DFC is a high-temperature, high-efficiency type fuel cell designed for stationary applications. Operating directly on natural gas results in a simpler, more efficient system; natural gas is readily available and transportable, and it is not necessary to wait for the hydrogen economy to materialise.
In addition the high operating temperature provides high grade heat, which increases overall energy efficiency and increases the number of options for using generated heat.