The Feasibility of Small Hydro-Electric Generation in a Large Urban Area

The Feasibility of Small Hydro-Electric Generation in a Large Urban Area

Benson Y. Zhang (University of Auckland, Auckland, New Zealand) and Adam Taylor (School of Engineering, Auckland University of Technology, Auckland, New Zealand)
DOI: 10.4018/jsesd.2012100105

Abstract

The possibilities of generating electric power from relatively small hydro-electric sources in a large urban area is investigated. Two different aspects of hydro-electric sources have been studied: storm/waste water pipes in large multi-tenanted residential buildings and urban storm water discharge area (CSI area). The potential to generate from these sources has been investigated using a micro-turbine. The potential electric power which could be extracted from the sources was estimated using energy conservation equations under normal engineering assumptions. While technically feasible, all options are shown to be uneconomic in practice.
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2. Background

New Zealand’s narrow and longitudinal geography and reliance on hydro electric power have evolved hand-in-hand with a disparate distribution of population/consumption and power generation between North Island and South Island [REF]. Generally, electricity is generated in the South Island, transmitted to consumption in the North Island over a High Voltage Direct Current (HVDC) link (http://www.gridnewzealand.co.nz/n45.html).

Ongoing upgrades to this network are becoming burdensome to the nation, and hydro-electric resources in the South Island are becoming scarce, and the losses in such an elongated and distributed network are significant. The idea of locating generation locally to demand is gaining traction, perhaps using micro-turbines (Li, Wang, & Yuan, 2010.)

2.1. Local Generation

Alternative solutions have been suggested and implemented, such as using more geothermal generation in the North Island, more coal-fired generation in the North Island, or more wind-farms in the North Island (Hung & Bodger, 2007). Local generation close to the load to minimize transmission losses and the environment impact is considered by some engineering and political commentators as the best pathway forward.

Local generation suggests that, rather than transfer the energy from main area of generation to the main area of demand, energy is generated in the main area of demands or nearby from renewable resource, such as wind, geothermal and mini-hydro. While the energy generated from local renewable resource may not be enough for local demand, it could smooth the transmission loads different between peak and off-peak period, and not require significant transmission infrastructure expenditure or environmental impact. Hence, existing transmission lines could continue is service and upgrading may not become necessary.

2.2. Mini and Micro Hydro-electric Generation

Mini-and-micro generation schemes are commercially available and are typically employed in off-grid run-of-river applications, supplying sites ranging from a tiny scheme to electrify a single home, to a few hundred kilowatts for selling into National Grid. Small-scale hydropower is one of the most cost-effective and reliable energy technologies to be considered for providing clean electricity generation. The key advantages of small hydro (Schwartz, Pegallapati, & Shahidehpour, 2005; Kusakana, Munda, & Jimoh, 2008; Kusakana, Munda, & Jimoh, 2009) are:

  • Highly efficient: 70-90%,

  • High capacity factor: typically>50%,

  • Highly predictable: energy out is proportional to water flow.

Small hydro schemes are environmentally friendly as in most cases run-of-river installations require only a small dam or weir, little or no water is stored, and no significant transmission infrastructure is required. Therefore run-of-river installations do not have the same kinds of adverse effect on the local environment as large-scale hydro (Sarasua, Fraile-Ardanuy, Perez, Wilhelmi, & Sanchez, 2007; Dumur, Libaux, & Boucher, 2001). Indeed, in a city, water sources akin to run-of-river are often present in the forms of waste and storm water. This research focuses on the idea of using micro turbines to generate electricity locally in urban area.

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