Alternative energy pays off

WITH THE sharp hike in power tariffs in Andhra Pradesh, a small high-technology electronics and software company in Hyderabad is finding its investments in using renewable energy sources paying off.

Signion Systems specialises in digital signal processing and its clients include Defence and foreign companies such as Texas Instruments. It uses water, collected through rain water harvesting, for cooling its building as well as solar photovoltaic panels and a wind generator to meet its electricity requirements. A 3 kWp photovoltaic array, connected to a 1 kW UPS, drives DC pumps. The pumps take water from the two rainwater collection ponds and pass them through heat exchangers mounted below the roof of the Signion building. This system suffices to cool the rooms substantially during hot summer days. The photovoltaic array also provides power for some of Signion's computers. Another 5 kWp photovoltaic array, connected through a 5 kW UPS, supplies power for some more computers.

Signion has also acquired a 0.75 kWp wind generator (at a rated wind speed of 11 metres/second) and designed a power converter for it, the Zephyr-1000, which can provide conditioned power at 230 volts / 50 Hz.

The wind generator was fabricated in Pune in accordance with a Netherlands design. The generator uses a four-pole rare-earth permanent magnet based system to provide 3-phase variable frequency/voltage. The Zephyr-1000 power converter has an inexpensive Motorola microcontroller to run software for controlling both the rectifier and inverter. The rectifier software controls the voltage of the converter's DC bus. The DC bus can be supported either by ultracapacitators or by batteries. Signion currently uses electrolytic ultracapacitators but plans to replace these with long- life non-electrolytic (aerogel) ultracapacitators, once these become widely available. The rectifier software also provides elecrical braking, through controlled shorting of the rotor windings, at excessive wind- speeds. The inverter software provides impedence matching for optimum power transfer as well as regulation of output voltage, frequency and harmonic content.

Since overcast skies are likely to see stronger winds, the wind generator complements the solar photovoltaics. Initial tests showed that with the average wind speeds of 4.5 metres/second prevalent at Signion's factory, the power converter delivered 100 W of conditioned power. During the monsoon months when the average wind speed could be around 6 metres/second, it would deliver 200 W of power. The diameter of the wind generator's rotor blades is to be increased from the current 3.3 metres to 3.6 metres so that power output can be raised by 20 per cent. Signion expects to complete testing the wind generator system by the end of this year.

Signion also plans to establish a common 230 volts AC power bus to which the solar photovoltaic systems and the wind generator will be connected. Computers and other devices will then draw power from this bus.

Signion's alternate energy systems have cost Rs seven lakhs to set up and currently meet about 17 per cent of its power requirements. Mr Sriram Jayasimha, the technocrat-entrepreneur behind Signion, estimates that power from these alternate energy systems costs about Rs seven per unit. This compares favourably with the power tariff being charged by Andhra Pradesh's Transco. In addition, the alternate energy systems being used at Signion were able to provide conditioned power, with tightly controlled voltage and frequency excursions as well as surge suppression, required by sensitive electronic and computer equipment. The systems have provided trouble-free service over the last five years, says Mr Sriram Jayasimha.

N. Gopal Raj

in Bangalore