**1. Introduction**

The needs of water consumption, environmental targets and energy savings have become the main concerns of water managers over the last years, becoming more and more important goals for the sustainable development and energy efficiency in water systems (Ramos & Covas, 1999). The needs for water consumption, environmental targets and saving energy have become ones of the world's main concerns over the last years and they will grow to be more and more important in a near future (Refocus, 2006). The objective of these systems is to guarantee the delivery of enough water with good quality to populations. Although, in order to achieve that, energy for pumping is needed, representing the main cost for water companies who operate the systems. The evaluation of the energetic potential in water systems may become a common procedure to achieve energy improvements on these systems. This can be done by taking advantage of the possible environmental and economical benefits from the instalation of a water turbine as a clean energy converter.

The optimization of operations energy consumer or production systems has been investigated for some decades. The interest in this area is not only related to the complexity of the problem but mainly by the environmental, economical and social benefits by adopting this type of solution. The implementation of energy production components in water supply systems is a solution that intends to increase the energy efficiency by using local available renewable resources. With this kind of systems the external energy dependence and their costs can be reduced. The adaptation of water supply systems to produce energy is an advantageous solution because most of the system components already exist (e.g. reservoirs, pipe system, valves) and there is a guaranteed discharge continuous flow along each day. Pump hydro storage systems are used as energy and water storage on systems' networks. These systems consist of two reservoirs, where one is located at a low level and the other at

© 2012 Liang et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

a higher elevation, with pump and hydropower stations for energy injection or conversion. During off-peak hours the water is pumped from the lower to the upper reservoir where it is stored. During peak hours the water is released back to the lower reservoir, passing through hydraulic turbines generating electrical power (Bose *et al.*, 2004).

Pumped-Storage and Hybrid Energy Solutions

Covão tank and tunnels

Water Treatment Station

**A**

550,00

320,00

**D** 

Towards the Improvement of Energy Efficiency in Water Systems 177

St.Quitéria Hydropower Plant

**Surge protection device** 

In this system there is a pumping and a hydropower station located at Socorridos. It is a reversible type system which enables pumping (in one station) and power production (in a parallel station) of 40000 m3 of water per day. Figure 1 depicts a scheme of Socorridos

Levadas

The system includes an upper reservoir (Covão) at 540 m, which is used to supply water for the Câmara de Lobos population. In addition to the tunnels, the Covão reservoir is used as storage for the water that flow from the mountains. In Socorridos, there is a tunnel located at

**Figure 2.** Socorridos pumping station – outside view (on the left). Socorridos-St.Quitéria steel pipe (on

system. Figures 2 to 6 show the all elements of the system under real conditions.

WTS 80,00

**B**

**Figure 1. Multi-purposes scheme of Socorridos system** 

Socorridos Hydropower Plant

Socorridos Pumping Station (buried)

**C**

Socorridos tunnels

85,00

81 m that has the same capacity as the upper one.

the centre and on the right)1

When a wind park is combined with a pumped-hydro system, several advantages can be achieved:


The optimization of pump/turbine-operation with energy consumption/production has been investigated over the last decade (Allen, G., McKeogh, F.J., Gallachóir, B., 2006; Anagnostopoulos, J., Papantonis, D., 2006). An optimization problem is a mathematical model in which the main goal is to minimize or maximize a quantity through an objective function constrained by certain restrictions. The optimization models can use several methods which nowadays are becoming more efficient due to the computer technology evolution. In Firmino *et al*. (2006) an optimization model using linear programming was developed to improve the pumping stations' energy costs in Brazil. The study revealed that the energy costs can be reduced by 15%. In Gonçalves et al. (2011) a best economical hybrid solution is applied and the study showed the installation of a micro hydro in a real small water distribution system using water level controls and pump operation optimization by using genetic algorithms shows the improvement of the energy efficiency in 63%. In Castronuovo and Peças Lopes (2004) a model for the daily operation of a wind-hydro plant was developed using linear programming. They concluded that, for the test case presented, the predicted yearly average economic gain of including a pumped-hydro station in a wind farmer, is between 425.3 and 716.9k€.

In this paper an hourly discretized optimization model for the determination of operational planning in a wind pumped-hydro system is presented. Comparisons were made between cases with and without complementary wind energy. The economical profit for each case study is presented.
