untitled
Key elements of a renewables energy regime for Pitcairn Island  
 
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ref:

INFORSE Secretariat
Gl. Kirkevej 82
DK-8530 Hjortshøj
Denmark
Phone: +45 86 22 70 00
Fax: +45 86 22 70 96
E-mail: inforse@inforse.org                          

cf: http://www.inforse.org/projects_pro.php3id=23

http://www.inforse.org/europe/educat.htm

Tranche One: micro-hydro

the magic formula for micro-hydro:

Power (kW) = Head (drop-in metres) x Flow (m3/second) x Gravity (9.81s2) x Efficiency (.51)

kW = H x Q x g x e

the key metrics to support about 100 households are:

15kW = 100 x .03 x 9.81 x .51

A turbine generator set to operate at a head of 100 m (328 ft.) with flow of 0.03 m3/s (63.6 cfm) will deliver approximately 15 kW of electricity. This is given by P = Q (0.03) ?nbsp;H (100) ?g (9.81) ?e (0.51) = 15 kW, assuming an overall systemic efficiency of only 51% ...with gentle tweaking this could be leveraged to c@ 75%.

Pth =  H x Q x g x e

Pth = Theoretical power output in kW
H = Gross head in m
Q = Usable flow rate in m3/s
g = Gravitational constant (9.81 m/s2)
e = systemic efficiency

 another.eg:
A site has a head of 10 m (33 ft.) with flow of 0.3 m3/s (636 cfm or 4755 gpm); therefore, the potential power output is given by Q ?H ?g (0.3 ?10 ?9.8), which is 29.4 kW.

Table 1 - Typical Power Output (in Watts) With Various Head and Water-Flow Rates

===============================
Power = The rate of doing work
(IE Watts or horsepower)

1 Watt = 1 Volt X 1 Ampere

1 Horsepower = 746 Watts

1000 Watts consumed = 1 kiloWatt-Hour  [kWh]
(IE the unit found on utility bills)
===============================

nb! the sweet spot on the graph below re. Pitcairn,is the co-ordinate 120m x 20 lps delivering 16kW power

Conversion Factors
Here's  some useful conversion factors when evaluating a hydro power site:

1 cubic foot (cf) = 7.48 gallons;
1 cubic foot per second (cfs) = 448.8 gallons per minute (gpm);
1 inch = 2.54 centimetres; 1 foot = 0.3048 meters;
1 meter = 3.28 feet; 1 cf = 0.028 cubic meters (cm); 1 m3 = 35.3 cf;
1 gallon = 3.785 litres; 1 cf = 28.31 litres; 1 cfs = 1698.7 litres per minute;
1 cubic meter per second (m3 /s) = 15,842 gpm;
1 pound per square inch (psi) of pressure = 2.31 feet (head) of water;
1 pound (lb) = 0.454 kilograms (kg);
1 kg = 2.205 lbs;
1 kilowatt (kW) = 1.34 horsepower (hp); 1 hp = 746 Watts.

Standard micro-hydro systems are constructed of the following key components:

  • Penstock, the pipeline carrying water from source to turbine.
  • Turbine, which transforms the energy of the flowing water into rotational energy.
  • Alternator or generator, which transforms the energy of motion into electricity.
  • Regulator, which either controls the electricity produced by the generator, or reroutes excess energy.
  • Wiring delivering the electricity to either the power grid, home, or storage batteries.
  • Batteries (optional) to store the electricity.
  • Inverter (on DC-producing systems) to convert the electricity to the standard AC current used in the home.

A key component of the system's functionality is the height and pressure of falling water, known as "head." Head is a function of the height of the fall and the characteristics of the channel, and can be calculated by a professional, or on your own using the techniques mentioned in the "Steps to Micro-Hydro" section.  The higher the head, the less water needed to produce power, and the smaller, cheaper, and more efficient equipment can be used in your system.  A "high head" site typically has a height of over 10 feet, whereas shorter drops are referred to as "low head." Sites with drops of less than 2 feet may not support a system.

Figure 5 - Head of a micro-hydropower system

Power calculation

The power available at a site is the product of the flow volume and head.  Flow volume is measured in cubic feet per second (cfs) or gallons per minute (gpm), one cubic foot equaling 7.48 gallons.

  • The flow rate is the quantity of water flowing past a point at a given time. Typical units used for flow rate are cubic metres per second (m3/s), litres per second (lps), gallons per minute (gpm) and cubic feet per minute (cfm).

  • The head is the vertical height in metres (m) or feet (ft.) from the level where the water enters the intake pipe (penstock) to the level where the water leaves the turbine housing.

    With the right configuration, a hydropower system can cost as little as one-tenth the cost of a photovoltaic (solar power) system producing the same amount. 

    • PUMPED STORAGE PLANTS
    Pumped storage hydro-electricity is a remarkably simple principle. To start with, two reservoirs at different altitudes are required. Water stored at height offers valuable potential energy. During periods of high electrical demand, the water is released to the lower reservoir to generate electricity. When the water is released, kinetic energy is created by the discharge through high-pressure shafts which direct the water through turbines connected to generator/motors. The turbines power the generators to create electricity. After the generation process is complete, water is pumped back to the upper reservoir for storage and readiness for the next cycle. The process usually takes place overnight when electricity demand is at its lowest.
    While pumped storage facilities are net energy consumers, they are valued by a utility because they can be rapidly brought on-line to operate in a peak power production mode. This process benefits the utility by increasing the load factor and reducing the cycling of its base load units. In most cases, pumped storage plants run a full cycle every 24 hours.


     

    ref.

    Design of Microhydro Electric Systems:

    http://tinyurl.com/ozsoy

    http://tinyurl.com/ovkwk

    http://thinkingdesigns.com/hydro/micro-hydro-system.php

     


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