Micro-Hydropower Plants - Estimation of Management Costs

The feasibility analysis of a micro-hydro power plant (MHPP) requires the estimation of three categories of costs:
1. Starting costs
2. Construction and installation costs
3. Operation phase costs
The third category encompasses management, operation and maintenance costs related to the operation phase of the power plant. An estimation of these costs is necessary in order to calculate the financial projections of the project.
In August 2010, the PSP Hydro team of GIZ in Rwanda completed the study ‘Privatisation of the Management of Existing Micro Hydro Power Plants: Feasibility analysis and strategy’. For this study, financial analyses of 18 publicly funded MHPPs had to be carried out. In order to do this, the PSP Hydro team created a model for the estimation of the operation phase costs for these plants, most of which were still under construction. This model (Management_cost_estimation_model.xls) is presented in this article.

Estimation model

Initially, the PSP Hydro team planned to collect information of existing MHPPs in operation in Rwanda in order to create a benchmark database from which estimate the costs of the new ones. To do this, the PSP Hydro team carried out consultations with 5 companies that were responsible for 6 hydropower plants, between 50 kW and 2 MW, in 2010. Unfortunately, the companies could only provide very poor records of their operational expenditures. Therefore, PSP Hydro had to change its strategy. To compensate the lack of real data, PSP Hydro drew in its own expertise to develop the spreadsheet for the calculation of operation phase costs for MHPPs that is in attachment.
The basic principal of the spreadsheet is that operational costs are directly related to the size as well as to the costs of categories 1 and 2. For example, the number of personnel will be bigger for bigger plants and the insurance cost will be directly related to the value (or cost) of the installed assets. The model is valid for MHPPs between 100 kW and 3 MW.
The required information is:
- Generation capacity (kW)
- Investment on civil works (RwF)
- Investment on electromechanical system (RwF)
- Investment on distribution system (RwF)
- Investment on office equipment (RwF)
- Cost of starting and other project costs (RwF)
The outputs (in RwF), for each of which an individual estimation is made, are:

1. Personnel
2. Maintenance contract for power plant
3. Insurance
4. Electricity and water bills
5. Office stationary
6. Consumables and spares (excluded office)
7. Communication and promotional actions
8. Transport
9. Office rent
10. Local taxes
11. Environmental management

Reliability of the model

This is a simplified model but the obtained results are comparable to those presented in previous studies in Rwanda:

• Fichtner (2009), ‘Actualisation Study of the Electricity Masterplan, Section 6, Economic & Financial Assessment’; DECON, December 2009. (See Tables 4-7, page 4-12)
• MARGE (2010), ‘Elaboration d’un plan stratégique national de maintenance des équipements de production et de distribution de l’énergie renouvelable’, BTC, July 2010. (See presentation of Robert J. van der Plas on ‘Maintenance Strategy for RET in Rwanda’ delivered on July 7th 2010 within the framework of MARGE’s study)

Recommendations

The coincidence with Fichtner (2009) and MARGE (2010) suggests that the model developed by PSP Hydro provides adequate estimations, at least for the study on privatisation for which it was created. However, as soon as the MHPPs co-financed by PSP Hydro are operational and real data is available, the model should be improved. This is a useful tool for feasibility analysis of MHPPs in Rwanda and could easily be adapted to other developing countries.

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Operation and Maintenance of Hydro Power

Introduction

Micro hydro operation and maintenance (O+M) procedures must be planned and put into action in the initial stages of any scheme to prevent breakdowns and reduced power outputs. The failure to use O+M procedures will result in financial problems and loss of confidence in the value of micro-hydro. The design engineer, the equipment installers and the users of the scheme, all have important parts to play in the O+M of micro-hydro schemes.
Ongoing operation, maintenance, and surveillance (OMS) are required to keep a plant running smoothly. However, OMS should not be considered only after building a micro hydro facility. It should be considered in choosing a site, designing the facility and when looking for financing. Sites that are remote or have poor access will have greater servicing costs. Facility design can greatly influence ongoing OMS costs including surveillance requirements and replacement and repair costs. Consideration should also be given to the availability of spare parts and the possible purchase of spare parts in advance. In financing the project the annual OMS costs need to be factored into the overall project cash flow. Thus, OMS should be thought of continually throughout the development of the micro hydro project.

Design considerations

It is essential that the long-term OMS costs be considered during the design of a micro hydro facility. For instance, it may be initially cheaper to buy and use uncoated steel pipe rather than a pipe coated for corrosion protection. Once the maintenance costs (the cost of replacing or field coating steel pipes to deal with corrosion), operating costs (increased friction and reduced energy with uncoated pipe), and expected life span are considered it may be cheaper to purchase coated steel pipe. This type of lifetime and reliability analysis should be considered carefully in all aspects of the design – it could save a lot of time and money.
The ease with which maintenance can be performed should also be considered during the design phase of a micro hydro facility. For example, equipment that requires regular maintenance should be located in a place that is easily accessible, and not located in a confined space. Also, if any equipment may need to be removed for maintenance during its lifetime, the means of achieving such a task should be considered. For instance, if any part of the generator needs to be removed for replacement, repairs, or upgrades - is there an economical way of doing it? Is there a hoist or crane capable of moving all the pieces of the generator? Can the roof of the building be removed easily for external crane access? By meticulously thinking through all the possible OMS scenarios that may occur, a lot of time and money can be saved over the life of the project.

Managing OMS

Even for the smallest micro hydro installations, a plan that ensures the consistent operation, maintenance, and surveillance of the facility is useful, if not necessary. To accomplish consistency in OMS, plans and procedures should be developed. These plans are typically located in the following documents:

• OMS Manual - The OMS Manual contains the operating instructions for the plant. It is written in a language that the operators can easily understand. OMS Manuals ensure consistent error-free operation of the plant.
• Equipment Manuals - Manufacturers usually provide Equipment Manuals for most equipment (i.e. turbines, hoists, pumps, switches, etc.). The availability and organization of equipment manuals greatly help OMS efficiency. A great deal of time and money can be spent on trying to find out how to do the necessary OMS, when the actual OMS may take little time or money to complete.
• Facility Drawings and Design Information - Make sure to keep the proper design information and drawings for all aspects of the plant that are uniquely designed. This information can make future repairs and modifications much easier.
• Maintenance Schedule - A Maintenance Schedule outlines when and what maintenance should be done. A schedule should be made according to a specific plant’s equipment OMS needs. It could consist of a checklist that must be signed by a supervisor or a worker once the maintenance has been completed. It could be a schedule developed using specially designed scheduling software.
• Log Books and OMS Records - Log Books record what OMS has been completed, and what has happened in the day-today operations of the plant. This can help trouble shoot problems regarding the facility’s OMS down the road. If any major work is completed that greatly changes the facility’s design or operation, a record should be kept for future reference. Over time, new operators will be hired and they can benefit from the recorded experience of their predecessors in operating the plants.

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Components of Hydropower

Turbine types

Turbine Runner	Head pressure
	High	Medium	Low
Impulse	Pelton Turgo Multi-jet Pelton	Crossflow Turgo Multi-jet Pelton	Crossflow
Reaction	Francis Pump-as-turbine (PAT)	Propeller Kaplan

A turbine converts the energy in falling water into shaft power. There are various types of turbine which can be categorized in one of several ways. The choice of turbine will depend mainly on the pressure head available and the design flow for the proposed hydropower installation. As shown in table 2 below, turbines are broadly divided into three groups; high, medium and low head, and into two categories: impulse and reaction.

The difference between impulse and reaction can be explained simply by stating that the impulse turbines convert the kinetic energy of a jet of water in air into movement by striking turbine buckets or blades - there is no pressure reduction as the water pressure is atmospheric on both sides of the impeller. The blades of a reaction turbine, on the other hand, are totally immersed in the flow of water, and the angular as well as linear momentum of the water is converted into shaft power - the pressure of water leaving the runner is reduced to atmospheric or lower.


For Further Information, click here.

Generators

• Thermo Electric Generators
  

Established producers of hydro generators

Marelli

Induction motor as generator

Controller:

Function principles

A Load- or Flow- controller ensures that the power output does not exceed the power demand and power output is stable (e.g. 230V, 50 Hz).
Water turbines, like petrol or diesel engines, will vary in speed as load is applied or relieved. Although not such a great problem with machinery which uses direct shaft power, this speed variation will seriously affect frequency and voltage output from a generator.
Traditionally, hydraulic or mechanical speed governors altered flow as the load varied. Nowadays usually electronic load controller (ELC) are used. These prevent speed variations by continuously adding or subtracting an artificial load (load controller). In that in effect, the turbine is working permanently under full load and the ELC diverts excess energy into a dump load, mostly a heater. The traditional kind of equalizing power in and output by controlling the flow is usually also automatised (flow control). Thereby the ELC steers a valve which regulates the amount of water inflowing.
In case of more power demand than supply the controller cuts off single users (clusters) in order to keep voltage and frequency constant for the others (first and second class connections). Load or flow controller are placed between generator output and the consumer line. <span lang="DE" style="font-size: 11pt; color: black; font-family: tahoma" />

Controller Types

Fluctuating energy demand requires a mechanism which either regulates the water input into the turbine (= flow control) or by diverting excess energy from the consumer connection (= ballast load).
For small micro or pico hydropower sites it's sometimes not easy to find the right controller. There is a lower price limit of several 100 USD even for only 1 or 2 kW power. In such cases there may be thought of manual control.

Load control:

The electric load controller (ELC) keeps outgoing Voltage and Frequency stable. Therefore the load on the generator has to be kept stable. The controller adds and subtracts an artificial load (heater) in a way to neutralise the fluctuations on the consumer side.

Ballast load

If energy demand is temporarily low the excess energy is dumped. It's converted into heat by some heat elements either in water or air. To increase an mhp's overall efficiency such excess power could be utilised as well. Therefore some storage technology would be required. Battery charging, freezers, water pumping or heat storage may be options. (see also discussion
Regarding intelligent load management: Dr Nigel Smith, Dr Philip Taylor and Tim Matthews

Flow control

regulates the amount of water into the turbine in order to match power output and power demand. Nowadays flow control is done mostly via electronics, which steer a valve

Manual flow control
In very small schemes often all power for lighting and TV is used constantly. Then energy consumption barely alters or does only at certain times. In such cases it can be even practical to train an operator who open / closes a valve manually to stabilise the Voltage. This allows to disclaim a controller, which saves costs and potentially flaws.

Load factor

The load factor is the amount of power used divided by the amount of power that is available if the turbine were to be used continuously. Unlike technologies relying on costly fuel sources, the 'fuel' for hydropower generation is free and therefore the plant becomes more cost effective if run for a high percentage of the time. If the turbine is only used for domestic lighting in the evenings then the plant factor will be very low. If the turbine provides power for rural industry during the day, meets domestic demand during the evening, and maybe pumps water for irrigation in the evening, then the plant factor will be high.
It is very important to ensure a high plant factor if the scheme is to be cost effective and this should be taken into account during the planning stage. Many schemes use a 'dump' load (in conjunction with an electronic load controller - see below), which is effectively a low priority energy demand that can accept surplus energy when an excess is produced e.g. water heating, storage heaters or storage cookers.

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Classification of Hydropower

By Size

Hydropower installations can be classified by size of power output, although the power output is only an approximate diversion between different classes. There is no international consensus for setting the size threshold between small and large hydropower.
For the United Nations Industrial Development Organization (UNIDO) and the European Small Hydropower Association (ESHA) and the International Association for Small Hydro a capacity of up to 10 MW total is becoming the generally accepted norm for small hydropower plants (SHP). In China, it can refer to capacities of up to 25 MW, in India up to 15 MW and in Sweden small means up to 1.5 MW, in Canada 'small' can refer to upper limit capacities of between 20 and 25 MW, and in the United States 'small' can mean 30 MW.
The German Federal Ministry for Environment, Nature Conservation and Nuclear Safety mentioned that a SHP is < 1 MW, everything above is a large hydro electric plant and usually comes along with a large dam. The International Commission on Large Dams (ICOLD) defines a large dam as a dam with a height of 15 m or more from the foundation. If dams are between 5-15 m high and have a reservoir volume of more than 3 million m³, they are also classified as large dams. Using this definition, there are over 45 000 large dams around the world.



Small hydro can be further subdivided into mini, micro and pico:

Mini (MH)	< 1 MW	grid connected	special know how required
Micro	< 100 kW	partially grid con.	professional know how required
Pico (PH)	< 10 kW	island grids	small series units produced locally; professional equipment available
Family (FH)	< ~1 kW	single households/clusters	often locally handmade solutions; professional equipment available

There is no binding definition how Mini hydropower output is to be classified. Rules for communication avoiding misunderstandings: Generally the terms can be used "downwards compatible". Pico- is also Mini- but not visa versa. Specific terms (Pico, Family) should be used only if they are required to indicate specifics. The spectrum needs higher diversification as smaller it becomes as there are certain differences in technique, usage, applicability and the grade of of ability to replicate them.

Comments:

• all installations require "special" knowhow
• there are "over the counter" pico turbines available for "self installation"
• Micro hydro is perhaps the most mature of the modern small-scale energy supply technologies used in developing countries. There are thought to be tens of thousands of plant in the “micro” range operating successfully in China[1], Nepal, Sri Lanka, Pakistan, Vietnam and Peru.
• Historically the term hydropower developed from naming very small units towards nowadays huge dams. Then there where new terms created to separate different clusters. All of them are hydropower. What is considered "mini or "micro" may be defined once and forever ... or not. If there are different opinions on this topic you're welcome to open a discussion group on this.

Comments on the debate “small” versus “large” Hydro Power

Classification according to size has led to concepts such as ‘small hydro’ and ‘large hydro’, based on installed capacity measured in MW as the defining criterion. Defining hydropower by size is somewhat arbitrary, as there are no clear relationships between installed capacity and general properties of hydropower or its impacts. Hydropower comes in manifold project types (see Classification By Facility Type) and is a highly site-specific technology, where each project is a tailor-made outcome for a particular location within a given river basin to meet specific needs for energy and water management services.


Large hydropower developments involve large dams and huge water storage reservoirs. They are typically grid connected supplying large grids. Preference for large hydro is on the decline due to the high investment costs, long payback periods and huge environmental impacts (losses of arable land, forced migration, diseases and damage to biodiversity). Many social and environmental impacts are related to the impoundment and existence of a reservoir, and therefore are greater for 'large hydro' plants with reservoir.


Small hydropower stations are typically run-of-the-river. They combine the advantages of hydropower with those of decentralised power generation, without the disadvantages of large scale installations. Advantages include: low distribution costs, no/low environmental costs as with large hydro, low maintenance and local implementation and management. Power generated with small hydro station can be used for agro-processing, local lighting, water pumps and small businesses^[1].


The constructions and integration into local environments of Small Hydro Power (SHP) schemes typically takes less time and effort compared to large hydropower plants. For this reason, the deployment of SHPs is increasing in many parts of the world, especially in remote areas where other energy sources are not viable or are not economically attractive.


However, larger facilities will tend to have lower costs on a USD/kW basis due to economies of scale, even if that tendency will only hold on average. Moreover, one large-scale hydropower project of 2,000 MW located in a remote area of one river basin might have fewer negative impacts than the cumulative impacts of four hundred 5 MW hydropower projects in many river basins (see also Negative Environmental Impacts). For that reason, even the cumulative relative environmental and social impacts of large versus small hydropower development remain unclear, and context dependent. General concepts like ‘small’ or ‘large hydro’ are not technically or scientifically rigorous indicators of impacts, economics or characteristics. Hydropower projects cover a continuum in scale, and it may be more useful to evaluate a hydropower project on its sustainability or economic performance, thus setting out more realistic indicators^[2].

By Facility Type

Hydropower plants can be classified in three categories according to operation and type of flow (see figure a-c). a) Run-of-river (RoR),
b) storage (reservoir) and
c) pumped storage HPPs
In addition, there is a fourth category (d) called in-stream technology, which is a young and less-developed technology.
Storage HPPs require high dams and big storage areas to be flooded. Such is usually the case in big infrastructure projects including the known environmental impacts. Small and micro hydropower usually avoids those but utilizes water that runs of a river.
Pumped storage HPPs work as energy buffer and do not produce net energy.




a) Run-of-River Hydropower Plant

Run-of-River Hydropower Plant

RoR plant mainly produce energy from the available flow of the river, taking advantage of the natural elevation drop of a river It is suitable for streams or rivers that have a minimum flow all year round or those that are regulated by a larger dam and reservoir upstream Water is diverted into a penstock and channeled to the turbine and then returned to the river RoR plants have either no storage or short-term storage, allowing for some adaptations to the demand profile Such reservoirs are usually smaller than those of reservoir hydro power plants but nevertheless dams can be ten to twenty meters high and can have gates to allow for water storage Power generation is dictated by local river flow conditions and thus depends on precipitation and runoff and may have substantial daily, monthly or seasonal variations Environmental impacts are generally lower than for similar-sized storage hydropower plants

b) Hydropower Plant with Reservoir

Hydropower Plant with reservoir

Hydropower projects with a reservoir (storage hydropower) store water behind a dam for times when river flow is low Therefore power generation is more stable and less variable than for RoR plants The generating stations are located at the dam toe or further downstream, connected to the reservoir through tunnels or pipelines Type and design of reservoirs are decided by the landscape and in many parts of the world are inundated river valleys where the reservoir is an artificial lake In geographies with mountain plateaus, high-altitude lakes make up another kind of reservoir Reservoir hydropower plants can have major environmental and social impacts due to the flooding of land for the reservoi

c) Pump Storage Hydropower Plant

Pump Storage Project.JPG

Pumped storage plants are not energy sources, instead they are storage devices Water is pumped from a lower reservoir into an upper reservoir, usually during off-peak hours, while flow is reversed to generate electricity during the daily peak load period or at other times of need Although the losses of the pumping process make such a plant a net energy consumer, the plant provides large-scale energy storage system benefits Pumped storage is the largest capacity form of grid energy storage now readily available worldwide

d) In-stream Hydropower Scheme

Space for a figure

To optimize existing facilities like weirs, barrages, canals or falls, small turbines or hydrokinetic turbines can be installed Usually the turbine is mounted on the river bottom, an existing river structure or on a floating structure These low-impact turbines act much like an underwater turbine and use the river current for power generation Basically they function like a RoR scheme The technologies may operate in unidirectional or bi-directional (tidal) river flows and do not divert river flow or use dams to retain water or create an artificial head As a new technology, in-stream HP is still relatively expensive as compared to other renewable alternatives and requires further study concerning potential environmental impacts and maintenance concerns

Text and Figures of this article are mainly taken from the Chapter 5 of the IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation (2011). Prepared by Working Group III of the Intergovernmental Panel on Climate Change [O. Edenhofer, R. Pichs-Madruga, Y. Sokona, K. Seyboth, P. Matschoss, S. Kadner, T. Zwickel, P. Eickemeier, G. Hansen, S. Schlömer, C. von Stechow (eds)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1075 pp.

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Measuring Head & Flow

The first step to judge a sites hydropower potential is to measure/estimate head and flow.

Head (the vertical distance between the intake and turbine)
Flow (how much water comes down the stream)

Head is very often exaggerated as is the flow rate, which varies over the year!

Wrong data occurs frequently. Confirmation of existing data is highly recommended!

Head and flow are the two most important facts of a hydro site. This will determine everything about the hydro system—volume of civil constructions, pipeline size, turbine type and power output. Inaccurate measurements result in low efficiency, high cost and scarcity of power.

For sophisticated methods how to inquire a sites feasibility, please check the Manuals section.
"Layman's book: How to develop a Small Hydro Site" may be a good start.


Methods of Head and Flow Measurement without Sophisticated Tools



Estimation of height can be done easiest if there is a steep slope (waterfall)by rope. Principle of a step by step head measurement:

Head measurement.jpg

By measuring total height step by step, it's crucial to do the bearing strictly horizontally. Ensure that by using a level or a water filled hose. Widely available are hoses and pressure gauges which allow the easiest method of height measurement. As longer the hose as less steps have to be taken to measure the total head.

Height measure by level

Head by pressure gauge

Height measure by hose

Estimation of flow is very difficult without measurement. A quick and easy way to measure is the floating method


First, measure the waters speed at an steady flowing part of the river. Therefore drop some item and stop the time it needs for a certain distance to float. Second, do a sketch of the rivers cross section by measuring its depth every 20-50 cm so you come up with a grid showing the rivers profile from side to side. With this data its cross sections area can be calculated easily. Finally the flow volume results from (water) speed x (section) area.

Flow measurement.jpg

Example:

A ball drifts 10 m in 12 s => speed = 10m/12s = 0.12 m/s.
Cross section => A1= 25 cm * 40 cm (0.25 m * 0.4 m) = 0.1 m2 ; A1+A2+ ... = A = 0.5 m2
Flow volume = 0.12 m/s * 0.5 m2 = 0.06 m3/s => 60 l/s

To estimate a sites potential cost its necessary to know additionally:
Pipeline (penstock) length
Electrical transmission line length (from turbine to consumer). As smaller the sites power output as higher the power lines cost share
Number of potential customers



Units and Power Estimations


Power: watts [W] or Kilowatts [kW] 1 kW = 1000W
Flow: 1 m³/s = 1000 l/s
Gross heat: height difference the water "falls down"
Net head: a little smaller than gross head. Gross head deducted by energy loss due to friction in penstock

Potential power ('electric)' is calculated as follows:
Power [W] = Net head [m] x Flow [ l/s] x 9.81 [m/s²] (est. gravity constant) x 0.5 (turbine/generator efficiency)
Potential power is estimated as follows:
Power output [W] = height [m] * flow [l/s] * 5

More accurate estimations take into consideration:
exact net head (intake to powerhouse)
exact flow (constant during the year?)
combined efficiency of turbine and generator (depends on quality, est. 60% = 0.6)

Example:
A 6 m high waterfall has 300 liter/sec => potential power est. : 6 m * 300 l/s * 5 = 9000 W = 9 kW

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Principle of Hydropower

A mass of water moving down a height difference contains energy. This can be harvested. Moving water drives some waterwheel/turbine. This rotation either drives machinery directly (e.g. mill, pump, hammer, thresher, ...) or is coupled with a generator which produces electric power.

Hydropower is probably the first form of automated power production which is not human/animal driven. Moving a grind stone for milling first, developed into the driving of an electrical generator. Next to steam it was for long the main power source for electricity.

Its continual availability does not require any power storage (unlike wind/solar power). It is mainly mechanical hardware. This makes it relative easy to understand and repair-/maintainable. In smaller units its environmental impact becomes neglect-able (see: environmental impact assessment and pros and cons of micro hydropower) .

In order to create electricity from hydropower, two parameters are critical:
Flow; or the minimum amount of water that is constantly available throughout the entire year
Head; the difference in height

These specific conditions limit generalising and standartisation of "how to install hydropower plants". Choosing the right location and planning requires some specific knowledge. With knowledge of water flow and height difference the potential power can be estimated. 

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