(756a) Peaking Power With 100% CO2 Capture Through the Integration of Solid-Oxide Fuel Cells, Compressed Air Energy Storage and Real Time Optimization

In recent years, sustainable production of
environmentally friendly electricity has become a major topic of discussion and
research worldwide. One promising technology is the solid-oxide fuel cell
(SOFC) power generation system [1]-[4]. An SOFC utilizes a carbonaceous fuel
gas (synthesis gas, for example) and an oxidant (typically air) to efficiently
produce electrical power through an electrochemical reaction across a solid
oxide barrier. There are key advantages to using SOFCs for power production.
For example, the anode exhaust is mainly H₂O and CO₂,
which are easily separated if the anode and cathode streams are not mixed
downstream, and the cathode exhaust is mostly N₂, which can be used
for additional power generation or heat recovery and then safely vented.
However, a significant disadvantage of the SOFC system is that there are
currently cost-prohibitive operational challenges associated with its dynamic
use, which limits the usefulness of an SOFC system for following a typical
diurnal demand profile for electrical power.

This work extends on the design of a natural
gas-fuelled SOFC system for base load power production with a compressed air
energy storage (CAES) plant for load-following capabilities described by Nease
and Adams (2013) [5]. Real-time optimization (RTO) is used to improve
load-following performance by minimizing the squared error between supply and
demand over dynamic simulations of up to one year of operation. The RTO scheme
uses real demand data available from the Independent Electricity Operator of
Ontario (IESO) to avoid sudden drop-offs in performance of the SOFC/CAES plant
stemming from system (such as stream flows) and compressed air storage (such as
minimum/maximum storage pressures) constraints. The effect of prediction
horizon on the RTO scheme's ability to improve load-following is investigated.
Furthermore, real forecasting performance metrics from the IESO are used to
incorporate realistic noise into the RTO predictions in order to quantify the
effect of uncertainty on the load-following capabilities of the SOFC/CAES
system. Calculations are performed using a combination of Aspen Plus v7.3 for
pseudo steady-state model development and MATLAB for dynamic simulations.

Simulation results based on real market demand
and pricing data show promising results for the SOFC/CAES system with regard to
its ability to provide peaking power with 100% carbon capture at competitive
market prices. The addition of CAES to a base-load SOFC plant provides
significant load-following capabilities with relatively small penalties to
efficiencies (1.1% HHV) and levelized costs of electricity (LCOE) (0.08-0.3 ¢
kW^-1 h^-1). Moreover, the addition of RTO to the SOFC/CAES
plant reduces the sum of squared error (SSE) between plant supply and consumer
demand by up to 68% when a realistic prediction horizon of 24 hours is used.
Extending this prediction horizon further reduces SSE with diminishing marginal
returns. The addition of pure random noise with a standard deviation of up to
10% does not have an adverse effect on load-following performance. However,
consistent over- or under-prediction of demand causes significant increases in
SSE due to error compounding (as much as a 100% increase over the case with no
uncertainty). However, even under unrealistically high uncertainty conditions,
the use of RTO still improves load-following by more than 50%. The integrated
SOFC/CAES plant, with the addition of RTO, is hence a very exciting
forward-looking energy strategy to provide affordable peaking power with zero
CO₂emissions. 

References

[1]        Adams T.A. II, Barton, P.I.
High-efficiency power production from natural gas with carbon capture. Journal
of Power Sources. 2010, 195, 1971.

[2]        Adams, T.A. II,
Barton P.I. High-efficiency power production from coal with carbon capture. AIChE
J. 2010, 56, 3120.

[3]        Duan, L.;
Yang, Y.; He, B.; Xu, G. Study on a novel solid oxide fuel cell/gas turbine
hybrid cycle system with CO2 capture. Int. Journ. of Energy Res. 2012, 36,
139-152.

[4]        Becker, W.L.;
Braun, R.J.; Penev, M.; Melaina, M. Design and technoeconomic performance
analysis of a 1 MW solid oxide fuel cell polygeneration system for combined
production of heat, hydrogen, and power. Journal of Power Sources. 2012, 200,
34-44.

[5]        Nease,
J, Adams TA II. Systems for peaking power with 100% CO2 capture by integration
of solid oxide fuel cells with compressed air energy storage. J. Power Sources.
2013; 228(15): 281-293.