Conventional concentrating solar power (CSP) plants typically have a very high levelised cost of
electricity (LCOE) compared with coal-fired power stations. To generate 1 kWh of electrical
energy from a conventional linear Fresnel CSP plant without a storage application, costs the
utility approximately R3,08 (Salvatore, 2014), whereas it costs R0,711 to generate the same
amount of energy by means of a highly efficient supercritical coal-fired power station, taking
carbon tax into consideration.
This high LCOE associated with linear Fresnel CSP technology is primarily due to the massive
capital investment required per kW installed to construct such a plant along with the relatively
low-capacity factors, because of the uncontrollable solar irradiation. It is expected that the
LCOE of a hybrid plant in which a concentrating solar thermal (CST) station is integrated with a
large-scale supercritical coal-fired power station, will be higher than that of a conventional
supercritical coal-fired power station, but much less than that of a conventional CSP plant. The
main aim of this study is to calculate and then compare the LCOE of a conventional supercritical
coal-fired power station with that of such a station integrated with a linear Fresnel CST field.
When the thermal energy generated in the receiver of a CST plant is converted into electrical
energy by using the highly efficient regenerative Rankine cycle of a large-scale coal-fired power
station, the total capital cost of the solar side of the integrated system will be reduced
significantly, compared with the two stations operating independently of one another for
common steam turbines, electrical generators and transformers, and transmission lines will be
utilised for the integrated plants.
The results obtained from the thermodynamic models indicate that if an additional heat
exchanger integration option for a 90 MW (peak thermal) fuel-saver solar-augmentation
scenario, where an annual average direct normal irradiation limit of 2 141 kWh/m2 is considered,
one can expect to produce approximately 4,6 GWh more electricity to the national grid annually
than with a normal coal-fired station. This increase in net electricity output is mainly due to the
compounded lowered auxiliary power consumption during high solar-irradiation conditions. It is
also found that the total annual thermal energy input required from burning pulverised coal is
reduced by 110,5 GWh, when approximately 176,5 GWh of solar energy is injected into the
coal-fired power station’s regenerative Rankine cycle for the duration of a year. Of the total
thermal energy supplied by the solar field, approximately 54,6 GWh is eventually converted into
electrical energy. Approximately 22 kT less coal will be required, which will result in 38,7 kT
less CO2 emissions and about 7,6 kT less ash production. This electricity generated from the thermal energy supplied by the solar field will produce
approximately R8,188m in additional revenue annually from the trade of renewable energy
certificates, while the reduced coal consumption will result in an annual fuel saving of about
R6,189m. By emitting less CO2 into the atmosphere, the annual carbon tax bill will be reduced
by R1,856m, and by supplying additional energy to the national grid, an additional income of
approximately R3,037m will be due to the power station. The annual operating and
maintenance cost increase resulting from the additional 171 000 m2 solar field, will be in the
region of R9,71m.
The cost of generating 1 kWh with the solar-augmented coal-fired power plant will only be
0,34 cents more expensive at R0,714/kWh than it would be to generate the same energy with a
normal supercritical coal-fired power station.
If one considers that a typical conventional linear Fresnel CSP plant (without storage) has an
LCOE of R3,08, the conclusion can be drawn that it is much more attractive to generate
electricity from thermal power supplied by a solar field, by utilising the highly efficient large-scale
components of a supercritical coal-fired power station, rather than to generate electricity from a
conventional linear Fresnel CSP plant. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/15901 |
| Date | January 2015 |
| Creators | Van Rooy, Willem |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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