Molnar 1

Low Temperature Solid Oxide Fuel Cells as a Utility Scale Solution to Power Generation

Prepared for: Hwayoung Yi Prepared by: Elliott Molnar

June 29th, 2015

Molnar 2 TEXAS A&M UNIVERSITY To: Ms. Hwayoung Yi From: Elliott Molnar Subject: Low Temperature Solid Oxide Fuel Cells as a Utility Scale

Solution to Power Generation Date: 6/29/2015 The following report approaches the issue of a growing energy demand and whether to meet the challenge with outdated coal-fired and gas turbine cycle power plants, or introduce modern fuel cell technology into the energy infrastructure which has recently become viable as a scalable stationary power source. Reports from government agencies, authoritative sources, and corporate entities on the emerging technology in the energy industry will be considered, as well as existing information on coal-fired and gas turbine plants. The capital, maintenance, operational, and environmental costs will be considered and weighted to determine the best direction for expanding the energy infrastructure.

Molnar 3 Abstract

“Low Temperature Solid Oxide Fuel Cells as a Utility Scale Solution to Power Generation”

Prepared By: Elliott Molnar With a growing demand for electrical power, the current infrastructure must be expanded. Brayton and Rankine cycle power plants have been the dominant choice of the power generation industry due to their legacy and well-understood concepts of operation. These cycles welcome heavy hydrocarbons as fuel sources which are often unrefined before firing, leading to copious amounts of carbon monoxide, nitrous oxide and volatile organic compounds (Elgowainy). Fuel cells, which were introduced in the second half of the 20th century, have long been an interesting concept to the energy community. Early proton exchange membrane fuel cells (PEMFCs) running on purified hydrogen and emitting water as the only exhaust compound made clean energy seem plausible. With high costs and low power outputs for their scale, PEMFCs were not seen as a viable solution to need to a larger energy infrastructure. Solid oxide fuel cells (SOFCs) have been seen as the most plausible of the newly emerged fuel cells as a stationary power supply. SOFCs have high power density which allows them to be scalable with high operating temperatures on the order of 700-800 [°C] producing a large amount of waste heat which can be recovered in a combined cycle system. Due to expensive Yttria-stabilized Zirconia surfaces, solid oxide fuel cells have previously not been a viable option to the commercial power industry. Nanostructure technology has solved a serious issue with the plausibility of fuel cells becoming a part of the electrical power infrastructure. The introduction of the nanostructured catalytic surfaces for use in fuel cells has led to lower temperature solid oxide fuel cell (LT-SOFC) technology. These new LT-SOFCs use cheaper Ceria and Bismuth based cathode surfaces as opposed to expensive Yttria-stabilized surfaces. The operating temperatures are around 350 [°C] which is still high enough to supply heat to a boiler and a low temperature super-heater in a combined cycle.

Molnar 4 Table of Contents

List of Illustrations………………………………………………………………………………... 5 Executive Summary………………………………………………………………………………. 6 Introduction………………………………………………………………………………………. .7 Argument…………………………………………………………………………………………. 8 Capital Costs……………………………………………………………………………… 8 Operating Costs…………………………………………………………………………… 8 Environmental Impact…………………………………………………………………… 10 Conclusion………………………………………………………………………………………. 11 Recommendation………………………………………………………………………………... 12 Glossary of Terms……………………………………………………………………………….. 13 References……………………………………………………………………………………….. 14 Works Cited……………………………………………………………………………... 14 Appendices………………………………………………………………………………………. 15

Molnar 5 List of Illustrations

Figures Figure 1 Natural Gas and Coal Prices (5-year with 2016 prediction) (EIA)................ ……..9 Figure 2 Comparison of Pollutants Produced by Different Systems (Elgowainy)………...10 Figure 3 An Open-Cycle Gas-Turbine Engine or Brayton Cycle (Sounak)……………….15 Figure 4 The Simple Ideal Rankine Cycle (Sounak)………………………………………15 Figure 5 Solid Oxide Fuel Cell Diagram. (Biopact)……………………………………… 16 Tables Table 1 Overnight Cost Comparison With 2010 estimates (EIA)………………………… 8

Molnar 6 Executive Summary

The power generation industry is rapidly growing as energy demands rise. To meet the growing demand, new power plants must be constructed. With every new plant, decisions must be made on what design is the best option, considering the local energy demands, peak hours, and environmental conditions. The dominant methods of power productions are the coal-fired Rankine cycle system, and the gas turbine Brayton cycle system. A combined cycle system can be implemented to take advantage of the waste heat from the gas turbine system. The existing methods of stationary power production are part of the core knowledge for most engineers. As an effect, new methods are not as well looked into unless they suggest significant benefits over what has worked for the past century. Solid oxide fuel cells, previously restricted by their economic plausibility, are now becoming a viable energy solution on the small scale and present the possibility for expansion if proper safety precautions to accompany scaling of the technology are considered. Companies such as Redox Power Systems have developed domestic scale Low Temperature SOFCs which show promising results if issues do not arise with scaling. In this study, it was found that in capital, operating, and environmental costs, LT-SOFCs are competitive, if not, better than existing power generation methods. With the introduction of cheaper materials and production methods, the capital costs were reduced in LT-SOFCs. As a side effect of changing the materials, the operating temperature was reduced to about 350°C and less pure composition fuels could be used. There are two reasonable courses of action to approach the need for increased power capacity. The more recommended approach is to begin scaling up LT-SOFC systems in order to meet the efficiency expectations and energy demands at a lower cost for the future. The alternative approach is to continue the implementation of the most efficient of the current systems, which is the combined cycle gas turbine.

Molnar 7 Introduction

With a growing population, there is a large need for and expansion in the power generation sector. In addition, the onset of the electrification of the automotive industry will lead to an expected increase in domestic consumption of electric power. The existing infrastructure applies outdated, yet understood concepts of power generation which are limited in efficiency by Carnot’s theorem. The early days of America’s energy industry found its roots in dirty, less energy-dense, lignite coal. Coal fired power plants have efficiencies on the order of 30-45[%] (EIA) and have fallen far behind the efficiency standards of gas turbine cycle power plants. However, with low maintenance costs, existing coal fired plants are tough to compete with economically. Gas turbine power generation is more efficient, but with turbine maintenance being an expected and costly operation, halting power generation for a significant operating period, coal fired plants still seem attractive in the modern era. Coal fired plants are no longer produced due to their high entry costs, but are kept running due to their low operational costs. Gas turbine systems are more common in the modern era because of their low entry cost but the natural gas fuel continues to be more expensive. Fuel Cells have long been an interest of the energy community, but previous designs were in no way economically viable. Modern solid oxide fuel cells on the other hand, are now becoming a competitive alternative to traditional heat engines. With the most recent capital costs as low as 700[$/kW] (Weimar), fuel cells are now less expensive than gas turbine and coal-fired capital investments of 917[$/kW], and 3246[$/kW] respectively (EIA). Fuel Cells also have the advantage of efficiency; nearly double that of the coal-fired method of power generation. To determine if solid oxide fuel cells are indeed an ideal solution to the needs of the growing power demands, we must look at all of the costs involved with power generation. First and foremost, the largest cost is the investment in infrastructure. The most important however in the long run is the efficiency and the expected fuel costs in the future. Fueling costs will be taken into account in terms of dollars per unit energy in order to have a standard unit to make a comparison on. As an issue that is a larger concern to the public than industry, the emissions and environmental effects must also be considered.

Molnar 8 Argument

Capital Costs As energy technology develops, the costs, methods, and scalability changes. In the capital costs of plant design, the cost of the units is the largest factor. In 2013, the capital costs for coal, gas turbine, and fuel cell units per kilowatt capacity were 3,246[$], 917[$], and 7,108[$] (EIA). In 2013, the expensive Yttria SOFCs were used as a model for the capital costs of a fuel cell system. In 2015 however, the introduction of new nanostructured LT-SOFCs has reduced the low-end cost to 672[$/kW] (Weimar). Due to lower material costs and cheaper production methods, fuel cells have dropped below the capital costs of gas turbine and coal fired systems. The higher power density of LT-SOFCs compared to the other options also allows for less land consumption, and therefore, lower property costs. There has been little exploration into the complications of scaling fuel cell designs to the gigawatt scale of coal fired plants. Capital costs may also increase as the rare compounds used in SOFCs rise in demand.

Table 1: Overnight cost comparison with 2010 estimates (EIA)

Operating Costs The most common unit for measuring the cost of industrial fuels is the USD per million British thermal units [$/mmBtu]. The most apparent cost in power generation is the fueling cost. As seen in figure (1), the cost of natural gas is now competitive with coal. In years prior to 2010, the costs of natural gas before shale fracking were as high as 5[$/mmBtu]. Natural gas is in high production and low demand, leading to the competitive cost of the fuel. The demand for coal is still much lower than natural gas due to the environmental limitations of coal fired plants. Currently, coal is about 2/3 the cost of natural gas per unit energy.

Molnar 9 While natural gas is slightly more expensive than coal, the efficiencies of natural gas powered devices such as turbines and fuel cells are higher. Both gas turbines and coal plants are limited by Carnot’s heat engine theorem, but due to the high firing temperature of gas turbine systems, the limiting Carnot efficiency is higher and limited by the turbine blade material and forging process. Coal-fired Rankine cycles are normally 45% thermally efficient and gas turbine combined cycle plants are 60% efficient on average for modern plants (Elgowainy). On the other hand, LT-SOFCs have a capable single cycle efficiency of 60% and if running in a combined cycle, up to 85% or greater can be achieved (Wachsman). This increase in unit efficiency when compared to coal fired systems bridges the gap that makes natural gas a more effective fuel when used in an SOFC system. Prior to SOFCs however, industrial grade natural gas could not be used as a realistic fuel. Due to contaminants within the fuel and molecular size, the surfaces of older PEMFCs would not tolerate heavier contaminating hydrocarbons, much less, the methane which forms the highest composition of natural gas. The issue of contamination could still occur in long term use for LT-SOFCs, so the maintencce costs will most likely be high for the fuel cell system when compared to gas turbine and coal-fired plant. It is important to note the reality of power consumption. Since power is consumed at different rates as a day goes on or as seasons change, the capacity of the power grid must be able to change in order to maintain the equilibrium between power being consumed and power being generated. Coal-fired plants are running constantly due to their start-up and shutdown times being as long as 2-3 days. Gas turbine plants may also take a decent amount of time to shut down due to the inertia of the turbine shaft. Fuel cells however, could be started up and shut down near-instantaneously as the demand for power changes (Elgowainy).

Figure 1: Natural Gas and Coal Prices (5-year with 2016 prediction) (EIA)

Coal 2016, 2.31NG 2016, 3.32

00.5

11.5

22.5

33.5

44.5

5

2011 2012 2013 2014 2015 2016

Cost (U

SD/mm

Btu)

Natural Gas and Coal Prices (5-year w/2016 predction)

CoalNatural Gas

Molnar 10 Environmental Impact One of the recent additions to the considerations in the power industry is the environmental impact of the system and the fuel being used. Coal is high in energy density, but it has many bonds that, when broken in combustion, form harmful compounds. Methane however, is very almost absent of bonds that may produce harmful compounds when combusted. Higher density, more harmful fuels are often used in transportation to avoid fuel weight in the vehicle. Natural gas, being a less harmful fuel and applicability as a stationary system fuel, is the best option for meeting the environmental needs of the public.

Figure 2: Comparison of Pollutants Produced by Different Systems Noise pollution has been identified as a considerable form of pollution as well. While not being harmful to the surroundings, noise can lead to hearing damage in humans. Maintenance crews in plants are continuously exposed to harmful noise pollution which comes with high speed rotary equipment. Fuel cells on the other hand do not produce significant noise pollution due to their method of operation. Since the only rotary equipment involved are the air and fuel inlet pumps and steam-turbines if there is a combined cycle in operation, noise pollution is significantly reduced.

Molnar 11 Conclusion

In capital, and environmental aspects, LT-SOFCs theoretically dominate the competition in all aspects. The capital costs of the LT-SOFC system can be as low as 679 [$/mmBtu] and the emissions are only rivaled by non-viable PEMFCs. A standalone LT-SOFC system would have no considerable noise pollution while a combined cycle LT-SOFC system would still have less noise pollution than the alternatives. A factor against the SOFC system happens to be the fuel cost. With coal being 69.5% the cost of natural gas per million Btu, it is significantly cheaper than natural gas. With the lack of demand for dirtier lignite coal and its regulation to avoid overproduction, it will most likely stay stable at around 2 to 2.5 [$/mmBtu]. With the much higher efficiency found in combined cycle LT-SOFCs of over 85%, natural gas is found to be a favorable fuel. Natural gas also has instability in its price, as seen in figure (1). Once natural gas becomes a stabilized commodity like coal, the LT-SOFC’s benefits can be confidently reviewed and confirmed as the most economically viable option. Scalability may also become an issue because existing fuel cell plants do not approach the capacity of existing coal fired plants. Expanding a fuel cell system into the scale of a coal fired plant could have unexpected safety issues. The management of high operating temperatures could become a risk, but such temperatures as 350[°C] are much lower than those found in coal-fired and gas turbine systems. As a safety and power management feature, SOFC systems have a much faster response time than coal and gas-turbine systems in the case of an equipment failure or changing power demands from the grid. Due to the high entry costs for coal fired plants, the next best production option for power is the gas turbine system. With higher efficiency and capability for use in a combined cycle system to recover the waste heat, the operational costs approach the same as the coal-fired plant. Maintenance costs are considerable for the turbines, but the capability to shut down the turbines and quickly restart after a shutdown make it a viable option to improve the capacity of the electrical grid in peak hours.

Molnar 12 Recommendation

I recommend that the stakeholders in the power generation industry consider one of the following options to meet the growing demand for grid electrical power. Option 1: Low Temperature Solid Oxide Fuel Cell System Emerging LT-SOFCs solve many of the issues presented by previous fuel cell concepts. Being able to use cheap industrial grade natural gas, low capital costs, and minimal pollution present a near perfect solution to the issues surrounding the current methods of power generation using gas turbines and coal-fired plants. While the technology is attractive, it has not yet been applied in a scaled operation. While the design of the cell stack is easily scalable, the management of several thousand stacks and whether or not they are properly operating may happen an issue akin to managing vast arrays of cloud servers. Option 2: Combined Cycle Gas Turbine System Traditional gas turbine cycles are well understood and the introduction of a combined cycle to the system is common in the modern day. While the gas turbine combined cycle system is more efficient, the fuel is more expensive than coal and the difference in efficiency make them only slightly more cost effective than coal-fired plants. The maintenance issues are expected and control systems are easily implemented. The power capacity is large and scalable to meet the outputs of other coal-fired plants. The efficiency is limited by Carnot’s theorem and therefore, the firing temperature. The theoretical maximum efficiency is therefore limited to about 70% and cannot be exceeded unless advanced blade materials are applied.

Molnar 13

Glossary of Terms Fuel Cell: An electrochemical device that reacts a gaseous fuel and oxidizer on a catalytic surface to form products, and in the process, produces electricity. Proton Exchange Membrane Fuel Cell (PEMFC): The oldest form of fuel cell, which was developed by NASA in the early days of the space program. The fuel is hydrogen and the oxidizer is oxygen. The product is water and does not yield a high power density. These cells are being adapted for transportation use because of their low operating temperature. Solid Oxide Fuel Cell (SOFC): As opposed to a PEMFC, the reaction surfaces are ceramic plates with a dosed conductive film. They are fueled by light hydrocarbons or hydrogen and the oxidizer is air. The products are similar to the combustion reaction, and as such, the operating temperatures are high in order to support the oxidation reaction. The high operating temperature limits these cells to use in stationary systems. These cells have significant power density and reasonably high efficiency. Low Temperature SOFC (LT-SOFC): The low temperature SOFC has the strength of using a more complex catalytic surface which lowers the activation energy of the oxidation reaction in the SOFC. The reduced activation energy lowers the operating temperature and increases the efficiency dramatically. The low operating temperature also opens up the ability to use less refined industrial natural gas as a fuel. Rankine Cycle: Commonly referred to as the steam cycle, the Rankine cycle introduces energy into the system by heating water into superheated steam and recovering the energy in a steam turbine generator. Crude fuels such as coal are commonly used to heat the boilers. Brayton Cycle: Commonly referred to as the gas turbine cycle, the Brayton cycle uses a compressor to compress air into a combustion chamber and then run the combustion products through a turbine to power the compressor as well as a generator. Due to the high operating temperatures and speeds of the turbine, gaseous fuels must be used to power the system. Natural gas is most commonly used as the fuel. British thermal unit (Btu): In the USCS system of units, the Btu is the standard energy unit used in thermodynamic calculations. The Btu is equivalent to 1.06 kilojoules in the metric

Molnar 14 system. Due to the scale of energy systems, the unit is commonly stated on the order of millions and written as [mmBtu]. Most commonly, the unit is used to compare fueling costs.

Works Cited

Bhattacharjee, Sounak. "GAS POWER CYCLE." Sounak 4 U. Weebly. Web. 28 June 2015.

Bhattacharjee, Sounak. "VAPOUR & COMBINED POWER CYCLE." Sounak 4 U.

Web. 28 June 2015.

"Biogas Powered Fuel Cell Wins Award, Attracts Attention from Sweden." Biopact. 29 May

2007. Web. 28 June 2015.

Elgowainy, A., and M. Q. Wang. "Fuel Cycle Comparison of Distributed Power Generation

Technologies." Argonne National Laboratory (2008). Print.

"U.S. Energy Information Administration - EIA - Independent Statistics and Analysis." Energy

Data Browser. Energy Information Administration. Web. 28 June 2015.

"Updated Capital Cost Estimates for Utility Scale Electricity Generating Plants." US Energy

Information Administration, 1 Apr. 2013. Web. 28 June 2015.

Wachsman, E. D., and K. T. Lee. "Lowering the Temperature of Solid Oxide Fuel Cells."

Science (2011): 935-39. Print.

Weimar, Mark R., Lawrence A. Chick, David W. Gotthold, and Greg A. Whyatt. "Cost Study for

Manufacturing of Solid Oxide Fuel Cell Power Systems." (2013). Print.

Molnar 15

Appendices The following diagrams describe the thermodynamic processes and devices used to operate the different power generation cycles.

Figure 3: An Open-Cycle Gas-Turbine Engine or Brayton Cycle. (Sounak)

Molnar 16

Figure 4: The Simple Ideal Rankine Cycle. (Sounak)

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Figure 5: Solid Oxide Fuel Cell Diagram. (Biopact)