What are the Benefits?

Micro

Micro Micro Micro hydro hydro hydro hydro power power power power system system system system introduction introduction introduction introduction

Not everyone is lucky enough to have a source of running water near their homes. But for those with river-side homes or live-on boats, small water generators (micro-hydro turbines) are the most reliable source of renewable energy available. One relatively small water turbine will produce power non-stop, as long as running water is available, no matter what the

weather.We're pleased to introduce a comprehensive line of micro-hydro water turbines, ranges from 200W to 100KW.For people with a good source of

year-round running water, one or two water turbines may be all they need to power their homes. However, for those with seasonal, winter-only streams available, a small water generator may be the perfect back up for a solar system's off-peak season.

If you think a home water power system may work for you, browse our site for more information, or contact us for help putting together a microhydro system to meet your needs.

What What

What What are are are are the the the the Benefits? Benefits? Benefits? Benefits?

1. The considerable benefits of micro hydro power include the following:

2. ‘Fuel-free’ source of power

3. Different to large hydro since environmental impacts of installation are negligible.

4. Renewable energy source therefore helping to reduce greenhouse gas emissions and having a net positive impact on the environment.

5. Constant generation over long periods unlike wind and solar power 6. Good correlation with demand (more hydro energy is available in winter when heating loads are high)

7. Long lifetime of systems, typically 25 years or more Low maintenance requirements and running costs

8. Reasonable payback for grid -connected systems, often 10 years or less

Technology Technology

Technology Technology background background background background

When water flows from a higher to a lower point, potential energy is released.

Micro-hydro schemes were developed to extract this energy in the form of

mechanical power. The amount of power available depends on the volume of

water flowing and the height (head) from which it drops. Micro-hydro

technology can only be used in wet mountainous areas, as it depends on

adapting existing streams rather than making large dams to manage water flow.

A micro-hydro scheme consists of a turbine, civil works and optional equipment for generating electricity.

Turbines Turbines Turbines Turbines

Turbine design varies depending on the head and flow of the available water:

1. Pelton turbines consist of a set of small buckets arranged around a wheel onto which one or more jets of water are directed. These turbines work well with a high head and do not require a large flow.

2. Francis turbines have a spiral casing that directs the water flow through vanes on a rotor and is used with lower heads and higher flows.

3. Cross-flow or Banki turbines are made as a series of curved blades fixed between the perimeters of two disks to make a cylinder. The water flows in at one side of the cylinder and out of the other, driving the blades around. They are used at even lower heads and larger flows, and are much easier to make than most other designs.

4. Propeller turbines are used for very low heads and large flows. The blades can be fixed, similar to a boat propeller, or a more complex version, the Kaplan turbine, has blades that can be adjusted in pitch relative to the flow.

5. River current turbines can be used with a large flow in a river. They are similar to a wind turbine, but immersed in flowing water rather than air.

Civil Civil

Civil Civil works works works works

In addition to the turbine, a system needs civil works to get the water to the power house in which the turbine is installed. A small dam is required in the stream bed to direct the water to the ‘head works’. Most micro-hydro systems are ‘run-of-river’ i.e. they store very little water behind the dam. The head works usually consist of a settling tank, to remove silt from the water. This feeds either a canal or a pipe that transfers water to the forebay, another tank sited above the power house. The canal or pipe can be fairly long, 1 km or more, if a suitable stream is distant from where the power is required.

The forebay usually has a second settling tank and a screen to prevent silt and

floating debris entering a pipe called the penstock, which is made as steep as

possible to transfer water to the turbine. When the water leaves the turbine, it

flows back to the stream through the tailrace. Some turbines, such as the

Francis and propeller turbines, can use a diffuser (also known as a draft tube)

in the outlet pipe to increase performance by reducing the kinetic energy of the water leaving the system.

Generating Generating

Generating Generating electricity electricity electricity electricity

When turbines are used to generate electricity the output from the turbine must match the demand for power, otherwise the voltage and frequency can vary suddenly, which can badly affect electrical equipment. The demand for electricity in an off-grid system is often very variable, because people switch lights and machines on and off, so the power supply must be varied to keep close control. There are several ways to do this. One approach is to use a mechanical governor, which controls the water-flow to the turbine by opening and closing valves. However, these are expensive and react slowly. The alternative is to use an electronic load controller, which allows the full flow of water to run the turbine, but switches a ‘dump load’ on and off to balance the varying power demand. The dump load is usually an electric heater which can simply be cooled by the flowing water, or if possible used to generate useful heat, such as for washing water.

Installation Installation

Installation Installation and and and and economics economics economics economics

The term ‘micro-hydro’ is usually used for power outputs of between 5 kW and 100 kW. This is sufficient to give light to a village or a small town or to run one or more small industries, such as wood or metal working machines.

Internationally, most micro-hydro systems are off-grid, as they are usually in remote mountainous areas. Systems below 5 kW are usually termed

‘pico-hydro’ and are usually used for individual homes or communities of two or three houses.

When a micro-hydro system is installed in a community, the local people are usually involved, as labour is required to build the civil works. This labour is regarded as providing about 15% of the total cost of a system and is

sometimes referred to as ‘sweat equity’. Most micro-hydro systems require

subsidy, as the capital cost is fairly high (about £2,000 per installed kW), while

the running cost is comparatively low. Systems requiring a large amount of civil

work or sited in inaccessible areas can cost much more. People pay for the

electricity provided or for the service available from machines driven by

mechanical power. This income is usually used to pay for operation and

maintenance of the plant, but may be sufficient to pay back a loan, if one is

taken to cover part of the cost of installing the plant.

Benefits Benefits Benefits Benefits

The output from a micro-hydro system is shaft power. This is often harnessed to drive a generator for electricity, but it can also be used to drive machinery directly. Many successful micro-hydro programmes have used shaft power to run food processing equipment, such as grain mills, rice hullers and oil

expellers. Most people see the main benefit of electricity as providing lighting, but this is only required in the evening, about four hours a day, while the power is available over 24 hours. Programmes that encourage the use of electricity to run small industries are much more likely to be successful.

The main environmental benefit of micro-hydro is the replacement of fossil fuels, such as diesel for driving machinery and generating electricity, or

kerosene for lighting. There are positive benefits for remote communities using micro-hydro electric systems, such as refrigeration for health clinics,

computers and radio for schools, internet access and mobile phone charging.

Young people are drawn back to their rural communities, as they can use their education to run small businesses powered by electricity. A major attraction is the availability of entertainment, such as TV and videos.

Environmental Environmental

Environmental Environmental impact impact impact impact of of of of hydro hydro hydro hydro power power power power

Globally, hydro-power is the largest source of renewable electricity, providing about 16% of the world’s electricity (global supply was 3,040 TWh in 2006), but most of this is from large-scale systems. In 1995, the total micro-hydro

capacity in the world was estimated at 28 GW, supplying about 115 TWh of electricity. About 40% of the micro-hydro capacity was in developing countries.

There are concerns about the environmental impact of large-scale hydro, because it requires large areas to be flooded to provide reservoirs, and can have serious impact on water management. Carefully-designed micro-hydro systems take a limited amount of water from a river or stream, have a small storage volume, and return the water a short distance down stream, and thus have very little environmental impact. Large numbers of small hydro systems have much less environmental impact than a single large hydro scheme supplying the same energy output.

Estimating Estimating

Estimating Estimating Head Head Head Head and and and and Flow Flow Flow Flow

Head Head

Head Head:::: The head is the height difference between where the water would enter

the hydro power system and it would leave it, measured in metres. Typically

this could be the height of a weir or the vertical drop of water over a water

wheel. If a waterwheel is an overshot type, the head will be the same as the wheel diameter. If the site is undeveloped and has no old watermill structures present, then the potential head would be between where the hydro intake screen would be and where the water discharged from the turbine would return to the watercourse.

With hydro it is very important to get as much head as you possibly can, as more head means more power for not much more cost. Depending on how much flow you have, the minimum amount of head required for a viable hydro system varies. If you have low head and low flow, then installing a hydro system won’t be very cost effective. Typically a head in excess of 1m is the minimum requirement.

Flow Flow

Flow Flow:::: This the amount of water that can be passed through the turbine, measured in cubic meters per second. If is very difficult to work out how much flow there is at a site, and establishing this forms a large part of the feasibility studies that we offer. The table below shows photographs of ‘typical’ rivers and streams to help you estimate how much flow you have. You need to estimate the average annual flow, and not the flow on the wettest day of the year. Once you’ve estimated the head and the average flow, you can estimate the power output as detailed below.

Power Power

Power Power:::: The maximum power of the hydro system can be roughly estimated as:N=9．81ηQH, for the micro unit it could simply estimated by N=(6.0～

8.0)QH. (Noted: The head is in metres and the flow in metres-cubed per second).The micro hydro power systems supplied by Hydro Generation typically range from 5kW - 250kW. A system smaller than 10kW however is unlikely to be cost effective.

If any query please feel free to contact us, waiting for your further inquiry.

Prepared by Jack Chen