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| | <span>A turbine converts the energy in | | <span>A turbine converts the energy in |
| | falling water into shaft power. There are various types of turbine which | | falling water into shaft power. There are various types of turbine which |
| − | </span> | + | </span>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. |
| − | | + | |
| − | can be
| + | |
| − | | + | |
| − | categorised 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.
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| | {| cellpadding="0" border="1" | | {| cellpadding="0" border="1" |
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| | power - | | power - |
| | the pressure of water leaving the runner is reduced to atmospheric or | | the pressure of water leaving the runner is reduced to atmospheric or |
| − | lower. </span> | + | lower. </span> |
| | | | |
| | == '''Load factor''' == | | == '''Load factor''' == |
Revision as of 11:20, 16 June 2010
Introduction
disambiguation:
grid connection
island / isolated grids
battery storage / charging stations
Grid connection for mhp's
Hydropower usually operates 24 h / day. Most mhp's are connected by a grid to their consumers. If a connection towards the national or main grid is available, electricity can be fed in there. Often micro or pico hydropower units are installed in remote areas. There they feed an isolated grid. In such grid the mhp is usually the only power source. The power produced has to be leveled equal with the power consumed (see controller).
Battery storage is no must like at solar or wind power projects. This is a big advantage as it reduces costs and maintenance significantly. Nevertheless can charging stations extend a mhp's effectiveness by utilising power in times of low demand (late night). So even consumers can be served with are to far from the station to be connected by transmission cable.
Storage basin or dams
Small hydropower plants usually use (part-) river flow as driving force. Storage basins or even dams can buffer water. So demand peaks or (short) periods of water shortage can be bridged. As such infrastructures is costly and sophisticated, it's only used if there is a clear financial revenue; e.g. electricity supply for remote industries.
Ballast or dump load
A ballast load is mostly an electrical resistance heater. It's sized to handle the
full generating capacity of the microhydro turbine. They're placed in air or water. If there is more electricity produced then consumed the charge controller uses this excess energy to generate heat.
Other but not common ballast load may be pumping water or ice production.
Metering
AKA:
battery monitor, amp-hour meter, watt-hour meter
[[Image:|Metering]]
System
meters measure and display several different aspects of your
microhydro-electric system´s performance and status—tracking how full
your
battery bank is, how much electricity your turbine is producing or has
produced, and how much electricity is being used. Operating your system
without
metering is like running your car without any gauges—although possible
to do,
it´s always better to know how well the car is operating and how much
fuel is
in the tank.
[[|]]Main DC Disconnect
AKA: Battery/Inverter disconnect
[[Image:|Main DC Disconnect]]
In
battery-based systems, a disconnect between the batteries and inverter
is
required. This disconnect is typically a large, DC-rated breaker mounted
in a sheet-metal enclosure. It allows the inverter to be disconnected from the batteries for service, and protects the inverter-to-battery wiring against electrical faults.
Inverter
AKA: DC-to-AC
converter
[[Image:|Battery-Based Inverter]]Inverters
transform
the DC electricity stored in your battery bank into AC electricity
for powering household appliances. Grid-tied inverters synchronize the system´s output with the utility´s AC electricity, allowing the system to feed hydro-electricity to the utility grid. Battery-based inverters for off-grid or grid-tied systems often include a battery charger, which is capable of charging a battery bank from either the grid or a backup generator if your creek isn´t flowing or your system is down for maintenance.
In rare
cases, an inverter and battery bank are used with larger, off-grid
AC-direct
systems to increase power availability. The inverter uses the AC to
charge the
batteries, and synchronizes with the hydro-electric AC supply to
supplement it
when demand is greater than the output of the hydro generator.
[[|]]AC Breaker Panel
AKA: mains panel, breaker box, service entrance
[[Image:|AC Breaker Panel]]
The AC
breaker panel, or mains panel, is the point at which all of a home´s
electrical
wiring meets with the provider of the electricity, whether that´s the
grid or a
microhydro-electric system. This wall-mounted panel or box is usually
installed
in a utility room, basement, garage, or on the exterior of a building.
It
contains a number of labeled circuit breakers that route electricity to
the various
rooms throughout a house. These breakers allow electricity to be
disconnected
for servicing, and also protect the building´s wiring against electrical firess.
Just like
the electrical circuits in your home or office, a grid-tied inverter´s
electrical output needs to be routed through an AC circuit breaker. This
breaker is usually mounted inside the building´s mains panel. It enables the inverter to be disconnected from either the grid or from electrical loads if servicing is necessary. The breaker also safeguards the circuit´s electrical wiring.
Kilowatt-Hour Meter
AKA: KWH
meter, utility meter
[[Image:|Kilowatt-Hour Meter]]
Most
homes with grid-tied microhydro-electric systems will have AC
electricity both
coming from and going to the utility grid. A multichannel KWH meter
keeps track
of how much grid electricity you´re using and how much your RE system is
producing. The utility company often provides intertie-capable meters at no costs
'Turbines'types
[[Image:]]
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.
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
|
|
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.
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.
Load control governors
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 both frequency and voltage output from a
generator. Traditionally, complex hydraulic or mechanical speed
governors
altered flow as the load varied, but more recently an electronic load
controller (ELC) has been developed which has increased the simplicity
and
reliability of modern micro-hydro sets. The ELC prevents speed
variations by
continuously adding or subtracting an artificial load, so that in
effect, the
turbine is working permanently under full load. A further benefit is
that the
ELC has no moving parts, is very reliable and virtually maintenance
free. The
advent of electronic load control has allowed the introduction of simple and efficient, multi-jet turbines, no longer burdened by expensive hydraulic governors.
Controller:
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Load- or Flow- controller ensure that the power output does not exceed the power demand (e.g. 230V, 50 Hz).
If flow of water in a MHP-station is constant the energy output of a turbine/generator is constant as well. Power demand is usually fluctuating over the time (e.g. day/night). If supply is higher than demand, excess energy must be diverted, dumped. alternatively the water flow can be reduced which results in less power output.
In case of more power demand than supply the controller cuts of the of demand line.
Load controller are placed between generator output and the consumer line.
Controller Types
Load controller:
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Electronic circuit, which keeps output power constant in Frequency- and Voltage- parameters.
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).
Ballast load
usually electrical heaters in water or air. If energy demand is temporarily low the excess energy is converted into heat.
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)
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