(294b) Cooling Tower Design for the Water – Energy Nexus: Effect of Weather Conditions on Water Consumption and Tower Sizing

Authors: 
Guerras, L. S., University of Salamanca
Martín, M., University of Salamanca

Water-energy-food nexus has become an important triangle for the analysis of the sustainability of society growth (García and You, 2016). The three resources lie in the heart of the design of any transformation process. In particular, the power industry and the production of electricity play an important role due to the strong link between water and energy (Bauer et al 2014). Most power plants use wet cooling towers that cooldown the water used in condensing the exhaust steam from the turbine at the expense of water evaporation that is lost. The make-up of water represents the consumption of water in these facilities.

The analysis of water withdrawal and consumption in the power system has been carried out in recent literature presenting the operation of plants over time (Peck and Smith, 2017) as well as evaluating the abstractions and consumption as average values (Byers et al 2014). However, the operation and the design of the cooling towers is subjected to weather conditions (Ludovisi and Garza, 2015) and locations (Maulbetsch and DiFilippo, 2006).

In this work we evaluate the water footprint of Rankine and Combined Cycle (CC) power plants. Ranking plants will be able to resemble current coal and nuclear based facilities in terms of water consumption, while the CC cycle simulated natural gas powered facilities. Biomass based power plants can fit either to the schemes since biomass can be used as fuel in a boiler or used to produce a syngas via gasification. The facilities are modelled based on thermodynamics, mass and energy balances and rules of thumb for the boiler, the Rankine cycle, the Brayton cycle of the IGCC and the cooling tower where geometrical constraints are also included in the formulation.

We perform a detail analysis of the water consumption of these types of facilities for 10 different allocations corresponding to different climate regions in Spain, from semi desertic to the south, Mediterranean, Atlantic and continental ones over a year long and compute the structure and cost of the cooling tower. As a result, rules of thumb for the sizing of the cooling towers in different climate areas are developed. Correlations for both, the water consumed and the tower size and cost, as a function of the humidity, the temperature and the atmospheric pressure are developed to evaluate the water stress of the energy transition from current fossil and nuclear based power to renewable one.

References

García D., You F., (2016). The water energy food nexus and process systems engineering: a new focus. Comp. Chem. Eng. 91, 49-67

Bauer, D., Philbrick, M., and Vallario, B. (2014). "The Water-Energy Nexus: Challenges and Opportunities." U.S. Department of Energy.

Peck, J.J., Smith, A.D. (2017) Quantification and regional comparison of water use for power generation: A California ISO case study. Energy Reports 3, 22-28

Byers, E.A., Hall, J.W., Amezaa, J.M. (2014) Electricity generation and cooling water used: UK pathways to 2050

Maulbetsch, J. S., and M. N. DiFilippo. (2006). Cost and Value of Water Use at Combined-Cycle Power Plants. California Energy Commission, PIER Energy-Related Environmental Research. CEC-5002006-034.

Ludovisi, D., Garza, I.A. (2015) WATER CONSUMPTION OF COOLING TOWERS IN DIFFERENT CLIMATIC ZONES OF THE U.S Proceedings of the ASME 2015 Power and Energy Conversion Conference