Comment

One of the panaceas prescribed by environmental activists to combat global warming is to switch to renewable non-fossil energy sources. But can we depend on these resources for meeting a large part of our future energy demand? There are good reasons to doubt this.

Take wind power, for example. India is a region of low mean wind speeds, barring the monsoon months. Since energy derived from wind power is a function of the cube of the wind speed, this means India’s on-shore wind power potential is very limited.

The ministry of new and renewable energy (MNRE) has estimated a total potential of just 45,000 mw. The actual capacity installed, despite such inducements as capital subsidies, quick depreciation, etc, has been only about 12,000 mw and the average capacity factor is a miserable 15%.

Small hydro — up to 25 mw capacity — remains a problem because the subcontinent’s streams and rivulets, barring the snow-fed ones in the Himalayan foothills, are not perennial. They exhibit a reasonable water flow only during the monsoons. Run-of-the-river generation is, therefore, sporadic and undependable.

Any attempt at creating small dams raises a furore from people displaced and downstream water consumers as well as objections about deforestation. Because of this, while the potential for small hydro has been pegged at 15,000 mw, the capacity installed so far is less than 2,500 mw and the actual capacity utilisation is less than 50%.

Regarding biomass-based electricity generation, although there appears to be a huge amount of agricultural residues available in the country, from the cultivation of food grain, fruits and vegetables and plantation products, the fact remains that no concrete survey has been done on the actual availability of surplus biomass in the country.

The word surplus is used deliberately, since a large portion of the agro-residues in the country are used as cattle fodder and for bio-fertiliser. Collecting a sufficient quantity of such residues to feed a biomass-based generator is a logistical nightmare and expensive to boot.

A CII-Godrej Green Business Centre publication indicates, for example, that a 4.5 mw biomass-based power plant installed in Karnataka consumes about 150 tonnes of biomass per day to generate about one lakh units of electricity. The same problem of fuel availability afflicts biogas generation from animal wastes. It is estimated that 100 tonnes per day of cattle dung would be required to generate 300 kw of power. Such amounts of dung would be only available from large-scale cattle sheds.

For all the reasons mentioned above, against an estimated biomass power potential (excluding co-generation) of 16,000 mw, less than 1,000 mw has been installed so far.

Then again, it must be remembered that using biomass for power generation does not reduce the load of greenhouse gas emission as it is carbonaceous material that is being fired in the boilers in the form of solids or gas, resulting in carbon dioxide emission from the stacks.

How about solar energy? Yes, with an average solar insolation of 4-7 kilowatt-hours per square metre of land surface and about 2,300-3,200 sunshine hours per year, theoretically India’s future energy needs can be harnessed from the sun. However, when we come down to the technical and financial nitty-gritty, things are not all that rosy.

One is the fact that the efficiency of currently available commercial solar energy devices is pretty low. For systems capturing solar heat, this efficiency could be as low as capturing 3% of the incident energy for your ordinary flat plate solar collector to 7-14% for parabolic dishes. In the case of devices converting solar light to electricity, the conversion efficiency varies from 8% to 18%, depending on the technology used.

This low efficiency translates into a large collector area required to set up even a small amount of utilisable energy. Barring, perhaps, the Thar Desert, one cannot see large swathes of land available for establishing large-scale solar power plants.

The other negative factor about solar photovoltaic power is its very high capital cost —- around 4-5 times that of fossil fuelled power. A household, which wants to use solar electric power for meeting a connected load of 3 kw, would have to shell out Rs 6 lakh in installation costs. True, there are technologies on the horizon, which promise to bring down the cost further, but they are still commercially unproven.

Today, solar PV constitutes a miniscule part of India’s power generation capacity, with estimates in the region of 100 MWp, with grid connected solar PV generation at just a little over 2 MWp.

As against this, the Indian Solar Mission’s target of achieving 20,000 mw installed solar power capacity by 2020 appears a pipe dream. True, the MNRE announced in January 2008 an incentive scheme for Grid-Interactive Solar PV Generation Projects, which included a combined MNRE and state utility feed-in tariff of Rs 15 per unit, valid for 10 years after start of generation. But what about the enormous capital cost involved and how will that be raised by entrepreneurs?

India’s main renewable energy resources are wind, solar, biomass and small hydro, with a total potential of just around 100,000 mw. As of now, against an installed power generation capacity of 145,000 mw, renewables account for just about 9%. The demand for electric power, at a GDP growth rate of 8% per annum, is expected to touch 780,000 mw by 2031/32.

So, even if the entire potential of renewable energy is exploited —- a tall order indeed —- it will not meet more than 12% of the future demand. This does not mean we should not invest in renewable energy. But let us be realistic about what can be achieved.