Growth of the oil price, together with estimations according to which the known oil reserves shall diminish during the next 15 years by half of their quantity, constrain the developed country to turn to the renewable energy sources (RES).

Bound by the commitments assumed by the Kyoto Protocol, the debates concerning the “green energy” developed widely. The European Directive 2001/77 established that „promoting the electric energy from renewable sources, on the unique energy market, has as objective the increase of the renewable energy sources (RES) ratio from 14% to 22% (by 2010) out of the electric energy gross consumption from the European Union. The Directive brings a series of encouraging measurements and facilities for the investors in SER.

Romania intends, at its turn, that by 2010, the electric energy consumption from renewable sources to reach 33% out of the gross internal consumption, this percentage being at present around 28% and is exclusively covered by the energy generated in hydropower stations.

Within SER, the hydropower has the highest percentage and it is considered energy supplied by hydropower units with an installed power lower or equal with 10 MW („small hydropower”), micro hydropower stations – MHPS. These are turning to account the micro-hydropower potential, integrated part of the hydropower potential, and if up to present hydropower stations with high powers as 10 MW were preferred to be performed, in view of integrating in the European Union, Romania shall take measures for tuning to account the micro-hydropower in order to be in compliance with the EU Directive concerning RES.
Hydropower potential developable in Romania by MHPS is equivalent with around 80% out of the energy generated by Iron Gates I, excepting that the MHPS are distributed on the whole country surface, therefore their construction would determine an economic growth in all the areas. On the other side, the water stored on a certain river stretch or brought in a certain point represents an utility in all the activity fields, having as direct or indirect result, the fulfillment of more utilities.

This way, the energetic structures and installations of small power would provide, besides the electric energy, also other utilities as: drinking water supply, industrial water supply; irrigation of agricultural lands; control of underground water levels on the riparian lands; environment protection by putting under safety conditions the riparian lands against floods; improvement of the local climatic conditions; sustaining of touristic activities; development of fish hatchery funds and other more.

An investment in a micro hydropower station also represents, for the isolated localities, generally from the mountains area, fuels savings for the electric energy supply and why not, thermal energy.

Many examples can be given, from other countries, where the electric energy supply was applied through a micro hydropower station. Some of them are shown in the below table:

	Construction of a small Pelton turbine with a single nozzle for Aspen Snowmass Ski Area. The site is an existing conduit used for the snow machine for the ski track. The turbine operates when the snow machine is not used and generates 115 KW for the ski track utilities.
	Hystad project is located in British Columbia. The turbine is designed to operate at a head of 317 m. The installed power is of 7 MW.
	Micro-turbine with 900 rpm, 2MW, for a project located in Honduras. Servo-deflector is designed for the whole wicket gate. Turbine is shown before commissioning.
	Inauguration of the 5 KW hydroelectric system commissioning. The installation serves for the domestic activities of a family from North Carolina.
	This micro-turbine with variable discharge is connected to a 40 MW Synchronous Marathon generator. It supplies electric energy for a coffee processing factory from Republic of Panama.
	The energy provided by a micro hydropower station to a community retired in New Guinea. This transversal turbine of 100 KW supplies energy to a mountain village and to a school from Papua.

SHP GUIDE

Water power is the most important electric energy source that does not contain carbon dioxide, sulphur dioxide, nitrous oxides or any other kind of polluting emissions and it does not creates any other solid or liquid waste. Hydropower station is using a natural or artificial head of a river and includes all the main advantages as compared to other power sources, savings in the carbon consumption, fuel or fire wood, being independent at the same time.

Under the present conditions, the following main advantages of the micro hydropower stations can be highlighted:
• They are proper for small power requirements, decentralized (light industry, private farms and factories, rural communities) and for external operations of the main network;
• They require low voltage distribution network and, possibly, sub-regional micro-networks;
• They can be operated in private ownership, in co-ownership or joint ownership, with a requirements of half-qualified manpower and with an administration in co-ownership or individual;
• Short construction period with local materials and use of the local population capacity, can have a considerable impact on the rural life quality;
• Their flexibility, specially as regards to their adjusting to variable loads depending on the inflow, makes them a privileged component part in any integrate power system;
• Hydropower stations can last for a long period of time. Some of them have over 70 years and are still in operation conditions. The power stations prepared to be commissioned in the near future can have an even longer life and can serve the consumers for many generations without polluting the environment;
• Investments in micro hydropower stations proved to be safe and reliable for many tens of years.
The electric energy output using as main source the water, is an energetic conversion process within which the water is an efficient mean for transmitting and transforming the gravitational process of flowing in mechanical and electric energy.

Main component parts of a hydroelectric station of small power are the following:
• The reservoir: constitutes a storing component of the available potential energy;
• Transferring, that includes the catching device (water intake equipped with trash rack) and the transferring circuit (canal, gates, galleries, tailrace canal or the outlet), where a part of the available energy is transformed into kinetic energy;
• Hydraulic turbine: is a part of the power station where the water energy is transformed in mechanical energy;
• Generator: the mechanical energy transmitted to the turbine maintains the generator runner speed generating electric energy according to the electromagnetic laws;
• Switchyard and conveying line: generated electric energy is conveyed and transformed in order to be connected to the network for supplying electric energy required by the consumers.

Generated power output is depending on two factors:

1. Water head height on vertical: the higher it is, the higher the power generated is.
2. Water discharge that is flowing through the turbine: the generated power is direct proportional with the water quantity flowing through the turbine within the time unit (second, minute).

Micro hydropower stations systems are divided in two main categories of turbines:
Turbines for high water heights and low discharges, impulse turbine.
Turbines for low water heights and high discharges, reaction turbines.

Turbines for high water heights and low discharges, impulse turbine.
The power generated in an impulse turbine is entirely given by the water hammer in the turbines. This water determines a direct push or impulse of the blades, its name deriving from this.

Turbines for low water heights and high discharges, reaction turbines.
The reaction turbines are rotated by the water reaction force hammering the runner blades. They can operate at very low water heights of up to 0.6 m, but they need a much higher quantity of water as compared to the impulse turbines.

Construction of a micro hydropower station consists in two categories of works: civil works and mechanical and electrical equipment works.

Civil works

Main civil works at the micro hydropower station are the intake dam, the pipes for the water conveying and the power station. The water route within a micro hydropower station is including:

- A water intake including the trash rack for the floats, a gate and an inlet into a canal, in a penstock or directly into turbine, depending on the development type. The water intake is generally made of reinforced concrete, the trash rack is made of steel, and the gate is made of wood or steel.
- A headrace canal and/or conduit and/or penstock that are conveying the water to the power station, from the developments this is located in, at a certain distance downstream of the water intake. The canals are generally excavated and are following the land contour. The headrace conduits and the penstock conveying the pressure water can be made of steel, iron, glass fiber, polymer, concrete or wood.
- The inlet and the outlet from the turbine include the valves required for stopping the water access and for technical revisions. These component parts are, generally, prefabs of steel or iron. The gates downstream of the turbine can be made of wood, if its maintenance and revisions require it.
- The tailrace canal conveying the water discharged from turbine back to the river. This, similar to the headrace canal, is carried out by excavation.

Mechanical and electrical equipment

Main mechanical and electrical component parts of a micro hydropower station are the turbine (turbines) and the generator (generators).

One turbine transforms the hydraulic energy in mechanical energy. There are different types of turbines that can be classified in many ways. Selection of turbine shall mainly depend on the available head and the discharge installed in the micro hydropower station.

Turbines are generally divided in three categories: of high, mean and low head.

The turbines used for low or mean heads are mostly reaction ones and include Francis and Kaplan turbines with fixed or variable blades. The turbines used for large installations are the impulse ones. These include Pelton, Turgo and Banki turbines (transversal flowing). The turbine having transversal flowing is sometimes named Banki. It is used for a large range of heads, covering the fields of Kaplan, Francis and Pelton turbines. It is appropriate for flowings with high discharges and low heads. The turbine selection type, geometry and dimensions are mainly depending on the head, discharge and speed of the runner.

As regards to the generators, there are two main types used generally within a micro hydropower station and namely: the synchronous ones and the induction (asynchronous) ones. A synchronous generator can be separately used while an induction one shall be used in connection with other generators.

For more information:
www.solaria.ro, www.lpelectric.ro, www.homepower.com/education/comp_hydro.cfm, www.inshp.org/, www.small-hydro.com, www.smallhydropower.com/manual3.htm etc.

Laws concerning the renewable energy sources:

- Government Decision no. 443/10.04.2003 concerning the promotion of electric energy generation from renewable power sources
- Government Decision no. 1535/18.12.2003 concerning the approval of Strategy for turning to account of the renewable energy sources.
- Government Decision no. 1429/2.09.2004 for the approval of the Certifying Regulation of the electric energy origin generated from renewable energy sources.