Capacity estimation of a minihydro plant based on time series forecasting

doi:10.1016/j.renene.2008.10.011

Renewable Energy

Volume 34, Issue 5, May 2009, Pages 1204-1209

https://doi.org/10.1016/j.renene.2008.10.011 Get rights and content

Abstract

A procedure to estimate the capacity of minihydro plants based on water flow time series forecasting is presented. First, the classic method used for this purpose is introduced and then a set of methodologies to assess the feasibility of minihydro generation and to determine system capacity based on time series forecast is described. The water flow time series is processed to determine the theoretical power generation and to assess if a minihydro plant can be installed. Finally the characteristics of each of the electro-mechanical components for the proposed minihydro plant are selected.

Introduction

Distributed generation systems constitute a viable alternative to address generation and electric power supply problems to isolated regions or small loads. An important aspect on this type of systems is the planning, design and evaluation of the potential energy available in a selected place [1]. In minihydro plants, feasibility studies show how the water flow varies along the years and where the water should be taken to obtain its maximum profit; they also show the power amount that can be obtained from the water flow, as well as the minimum and maximum limits of the profitable power [2].

In the literature concerning the design and selection of the main components of a minihydro plant [3], [4], [5], the size of the generator is chosen based on the water flow time series organized into a relative frequency histogram, and with a pre-selected plant factor, whose value usually varies from 0.70 to 0.85 for this type of systems [5]. From this information, it is also possible to calculate the theoretical average power and the average annual generation that can be obtained from the site (e.g. river).

In this work forecast methodologies based on data measurements from a monthly water flow time series are applied to predict the behavior of the water for a particular river where it is desired to install the minihydro plant. The proposed procedure aims enhancing the estimation of the generator capacity as the historical data of water flow is now complemented with the results obtained via forecast techniques.

For completeness, a selection of the most important electro-mechanical elements of a proposed minihydro plant is also provided.

Section snippets

Water flow time series

Fig. 1 shows the water flow time series used in this work. This historical data corresponds to measurements taken from the Cardel hydrometric station, in La Antigua River, Veracruz, México. The time series has 420 monthly observations, from the period of January 1951 to December 1985 [6].

Capacity estimation: classic method

Records of water flow variations along the years are taken in hydrometric stations located in the main rivers. These stations take data about the hydrologic situation of the area including the water flow variations of the river; this is done periodically, in some cases on a day-to-day basis. The water flow records are very useful to allow forecasting the future behavior of the river. This data is also taken into account to decide if a minihydro plant can be installed in a specific place.

From

Forecast techniques

As mentioned before the water flow time series is frequently used for the design and capacity estimation of minihydro plants. However, records of these variables from a previously selected place are not always available or there is just a few historical data. Besides, climate changes around the world have provoked, for instance, that drought and rainy seasons are not as periodic as they used to be; this make the water flow levels to change drastically from one season to another, and in some

Application to the capacity estimation of minihydro plants

With the results obtained from the previous section (forecast data) and the historical data, it is possible to determine the design water flow Q_i for the turbines of the minihydro plant. It is also necessary to know the plant factor pf, which is the percentage of time that the plant is expected to be generating electric power at full capacity. The typical plant factor for this type of hydro plants varies from 0.70 to 0.85 [5].

The following procedure was used to determine the value of Q_i:

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Selection of electro-mechanical equipment

Fig. 8(a) illustrates the high head scheme of a minihydro plant; this scheme uses weirs to divert water to the intake, from where it is conveyed to the turbines, via a pressure pipe or penstock. Fig 8(b) shows the electrical diagram of a minihydro plant. The basic electro-mechanical equipment in these plants comprises the turbines, generators, transformers and the interconnecting power line. An appropriate design and selection of the minihydro plant components based on the forecast techniques

Conclusions

A procedure for estimating the capacity of distributed generation based on minihydro plants has been presented. This procedure has been successfully applied for a practical case where this type of distributed generation can be installed.

The classic method used to estimate the capacity of a minihydro plant was also introduced and then time series forecasting techniques were applied in order to enhance the historic data available. Based on the results of these forecast techniques and the

Acknowledgments

The authors want to acknowledge the Universidad Michoacana de San Nicolás de Hidalgo (UMSNH) through the División de Estudios de Posgrado of the Facultad de Ingeniería Eléctrica, and the Institute for Energy and Environment, University of Strathclyde, for the facilities granted to carry-out this investigation. Rafael Peña wants to acknowledge financial support received from CONACYT through a scholarship to carry-out his Ph.D. studies.

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Capacity estimation of a minihydro plant based on time series forecasting

Abstract

Introduction

Section snippets

Water flow time series

Capacity estimation: classic method

Forecast techniques

Application to the capacity estimation of minihydro plants

Selection of electro-mechanical equipment

Conclusions

Acknowledgments

Applied Mathematics and Computation

Distributed generation: semantic hype or the dawn of a new era?

Power and Energy Magazine, IEEE

Manual of renewable energies, mini hydroelectric power stations

Layman's book: on how to develop a small hydro site

Best practice projects yearbook 1997–2000

Manual de mini y microcentrales hidráulicas; una guía para el desarrollo de proyectos

Situación Actual de la Minihidráulica Nacional y Potencial en una región de los Estados de Veracruz y Puebla