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a near-constant, speed-variable power arrangement. In stand-alone small hydro units(say up to 100 kW) – typically classified as micro, pico and nano hydro systems – itis apt to use uncontrolled constant power turbines with constant head and discharge.Thus, the generated power is always constant while the consumer load varies. Anautomatic load controller is needed to ensure that controllable additional load is phasedby the generator such that the total output power is constant at varying consumerloads. Wind energy, on the other hand, provides varying power as cube of wind speed.Thus, output power must always match this wind power. For this, power balancers areneeded for all wind speeds and loads through dump loads and additional source orstorage system. In solar PV systems, power output is DC and depends on lightintensity, thus needing a controller and inverter. A combination of renewable energysources in hybrid mode, which may involve storage systems like a battery, could alsobe explored.1. Bio-energyDifferent types of biofuels can be converted to liquids or gases to feed an engine todrive a generator, which in turn will energize the local load. The energy system may besimilar to the small petrol/kerosene-driven generator sets (1-10 kW) that are commonin domestic and commercial sectors. Such units are in use in ships, boats, camping,tourism, military and other stand-alone, off-grid applications. Biofuel can replace fossilfuel in these engines, with synchronous or induction generators. Power quality atgeneration, transmission and load levels should be ensured under varying magnitudeand types of loads (1-phase, 3-phase, balanced, unbalanced, linear and non-linear).While petroleum is readily available for use in engines, the user must install a systemto convert the available bio-energy source to a form compatible with the engine. Apartfrom sizing and design of the engine for a given load, its performance with biofuel mustbe assessed. Suitable electrical system – comprising the generator, control andtransmission – should be evolved. Unit sizes may vary from 5 kW to 100 kW andbeyond. It has near-constant speed prime mover with a typical speed drop of 5 percent from no load to full load via governor control. The engine operates at varying inputpower by adjusting fuel intake decided by output power. Indian R&D institutions havecarried out considerable work with great promise on energy conversion systems. Thereare some success stories such as ‘husk power’ in Bihar, where power is generatedfrom rice husk for local communities. A comprehensive list of examples of Indianexperience in bio-energy may be prepared and required support provided for promisinginventions in terms of technology transfer as well as for deployment in rural areas withutilization of local bio-energy resources.2. Small hydro energyMicro or pico hydro units in off-grid mode can be installed for local loads in remotelocations with favourable hydro potential needing minimal civil works. For off-gridapplications, uncontrolled turbine or ‘pump as turbine’ in constant power mode is moreapt since head and discharge at turbine end are constant with specific water headnaturally available in a site. Since consumer power varies randomly, surplus powershould either be used or dissipated, and that requires an electronic load controller(ELC). Self-excited induction generator (SEIG), researched in depth at the Indian Instituteof Technology (IIT) Delhi, is a good candidate for such applications, and a few SEIGunits have been installed following the study by IIT Delhi. Power in moving rivers andcanals is the other variant of hydro energy. A vertical axis Darius type turbine installed46