[The Woodman]

These are a few of my notes that might help.

Hydro power generation is defined in steps:

Pico: <5kW
Micro: 5kW – 100kW
Small/Mini: 100kW – 30MW
Large: >30MW

You might also want to have a look at the Renewable Obligation Certificate scheme to understand more about the finace structure.

Available Flow Rate: The available flow rate in a water course is determined by a number of factors:

The size of the watercourse catchment draining to the collection point for the generating system.
The physical characteristics of the catchment terrain such as gradient, vegetation, soil type etc.
The long term rainfall characteristics of the local area.
The quantity required to be left in the river for environmental reasons; this will be identified by the EA.
Power Generated: The power generated from the water can be calculated by formulas which take into account the head, flow rate, gravity, friction and other losses due equipment efficencies but an indication of the power that can be achieved from the equation: Power Produced (kW) = 7 x Available Flow Rate (m3/sec) x Head (m)

Power produced is measured in kWh (kilowatt hours) e.g. a site with a 5 kW output will theoretically produce (365 x 24 x 5) = 43,800 kWh of electrical energy per year.

Efficiency: The efficiency of hydro electricity equipment is variable with the best units achieving 90% efficiency. Typical overall efficiencies for the pico / micro size systems are lower at around 50 – 75% depending on size, type and location. For example the system discussed in the previous section will only be able to generate between 21,900 and 30,660 kilowatt hours of electrical energy from the available energy of the water flow.

Costs The following costing information is general and current prices should be sought for budgeting purposes.
Capital Costs System costs vary depending on the site, type of system used and distance from connection point.
Typical costs are in the region of £2,000 - £9,000 per installed kW with costs for sites with a limited water flow and a low available head being at the higher level and possibly considerably more on some sites.
Running Costs Running costs are in the region of 2% of the installation cost per year, less if a high proportion of the installation cost was infrastructure. The components of the system are simple and require little maintenance and should have a lifespan in the region of 20 years.

Returns The primary benefit to be obtained from electricity generation is from replacing existing electricity supplied to the business as this is the highest value that can be obtained in the region of 9 – 15 pence per kilowatt hour (January 2009).
Income sold either directly to an electricity supplier or through a broker will have a value of between 4 – 6 pence per kilowatt hour (January 2009) depending on the market demand for renewable energy.
In addition to the energy produced all electricity suppliers are required to produce a percentage of their power from renewable sources 9.1 percent in 2008/09 rising to 15.4% in 2015/16. The government provides support of around 5 pence per kilowatt hour in the form of Renewable Obligation Certificates (ROC’s) 1 ROC being issued for each MWh of electricity produced from a renewable source.
Producers of electricity from micro generation systems (under 50kW installed capacity) may be eligible for 2 ROC’s per MWh from April 2009; thereafter small systems may be able to obtain a subsidy in the region of 10 pence per kilowatt hour produced. The value of ROC’s may vary up or down depending on demand.