Is the Grid ready for the windy days?

Monday 30 November -0001

The monsoon months of May through September are some of the windiest months in the peninsula and Tamil Nadu has a lot to gain during these months if the wind energy is efficiently harnessed

The southwest monsoon months of May through September are some of the windiest months in the peninsula and Tamil Nadu has a lot to gain during these months. If the wind energy is efficiently harnessed by the state’s grid, wind energy can contribute up to 18 per cent (~12,000 Million kilo Watt hours) of the state’s electricity generation. But it should not repeat last year's mistakes

It is summer again and in the south Indian state of Tamil Nadu power cuts are back with load shedding lasting several hours in rural areas. The industrial and commercial sectors that faced severe losses due to power cuts last year have been promised ‘no power cuts’ this year from June 1st by the Chief Minister Jayalalitha.

The SW monsoon months of May through September are some of the windiest months in the peninsula and Tamil Nadu has a lot to gain during these months. This is because, the state not only has excellent wind resources but also has the highest installations of wind turbines in the country – 7,134 Mega Watt (MW), 40% of all installations in India. If the wind energy is efficiently harnessed by the state’s grid, wind energy can contribute up to 18% (~12,000 Million kilo Watt hours) of the state’s electricity generation1.

For this to hold, the state utility has to ensure last year’s trouble with wind does not repeat; last year the state grid was unable to absorb about 2000 Million kWh of wind energy during the windy months of May through September. Ironically this was also when the state was facing severe power deficit. With the arrival of another May, hopefully Tamil Nadu power utility is better prepared this time to harness the energy from wind more efficiently.

Last year, it is the ‘infirm’ nature of wind that was blamed for the grid’s inability to absorb the wind energy. Wind like solar is an intermittent resource and cannot be dispatched on demand. This in itself is not a problem! Utilities are used to meeting variable demand as the demand changes by the hour of the day and by the day each season. Having said this, with the increased grid penetration of wind, the utility has to be prepared with a back-up source if wind were to suddenly die. These back-up plants are typically based off fossil fuels and can be expensive, particularly if they have to be kept on-line. This challenge can be overcome easily with existing technologies.

Let us say each of the wind generation sites can record the wind speed and the power it can generate at a set frequency and all these sites can relay their site specific information to a central computing facility. Here computer models combining this large data set from different locations with weather forecasts and satellite images can crank out fairly precise forecasts of wind speeds days ahead and refine further for speeds hours ahead. This is precisely how the German grid is setting records in solar and wind integration. On a Sunday in May this year, renewable sources, mostly wind and solar, contributed to 74% to the total electricity mix midday. Similarly, in Colorado in the US, where wind power is booming, each of the hundreds of wind turbines record their site specific data every few seconds and dispatch the data every 5 minutes to a central computing facility 100 miles away where wind speed is forecasted with unprecedented accuracy.

In India, the Central Electricity Regulatory Commission last year mandated wind operators of capacities higher than 10 MW to forecast wind generation one day ahead in 15 minute blocks to help with grid orchestration. India’s wind farm operators have raised objection to this blaming high cost entailed. The tools are available for this and this is something easily doable and the cost is unlikely to be onerous for the wind operators.

The utility in turn has to grant wind energy a ‘must-run’ status. That is to say, the utility cannot blow wind energy away once generated and has to absorb the energy generated. What seems to have upset the wind operators is that, while it turned away wind last year, Tamil Nadu utility sought a permit from the state electricity regulatory commission to buy more expensive thermal power from out of state!

Once the energy generated by the wind operator reaches the grid, the utility has to compensate the wind generator. The government of India recently shifted from a tax based incentive of 80% accelerated depreciation to one based on generation of energy, generation based incentive (GBI) for wind. With the GBI, the emphasis is on revenue optimization makes it imperative for the operators to ensure optimal and efficient generation, as against just speedy installation under the earlier incentive; this is good news. GBI is also expected to draw a broader investor base and independent power generators to the wind sector. All said and done, unless the wind operators get paid in time, the investor interest in this sector will wane. In fact the wind operators last year had to wait over a year to be remunerated for the energy they generated.

Finally for the energy generated to be absorbed and transmitted to the demand centers so the utility can get paid, there has to be adequate transmission infrastructure. This has been a huge bottleneck in the country as a whole. In fact, the growth and up-gradation of transmission infrastructure have not kept pace with the increased capacity addition of power generation in the country.

In a smart move, taking advantage of the drop in solar prices, Tamil Nadu and other state governments have been wooing investments in solar energy. This along with the existing wind plants and any future power plants coming on-line will need good transmission infrastructure if all the power generated were to be absorbed efficiently and for the grid to be really ‘green’.

Over the last couple of decades, thanks to the government of India’s policy support, the entire wind related eco-system has sprung to support the successful deployment of wind power – turbine manufacturers, component manufacturers, operations & maintenance contractors and developers. In fact, India has evolved to be a major turbine manufacturing hub. There are now 19 manufacturers in the country with an annual production capacity of 9,500 MW of turbines. In terms of installations, India stands fifth in the world with around 20,000 MW of wind capacity. But with the current available turbine technologies the total potential is considered several folds higher.

Of course wind energy alone cannot bridge the state’s or the country’s power deficit. However, given financing and resource are not a problem, strong commitment on the part of the government and the industry can help wind energy be a sizeable percentage of the country’s grid. India has almost all it takes to be a large player in the wind arena. First it needs to find ways to extract as much energy out of this annual windy season!

 

 Shuba V Raghavan is an Independent Energy Analyst

1 Assuming wind plants operate at 20% plant load factor (PLF) and consume 2% auxiliary consumption. For rest of the state’s power capacity of 11,000 MW, a PLF of 75% and auxiliary consumption of 8% is assumed

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  • The problem is due to

    The problem is due to restrictions imposed on state load despatch centers by the regional load despatch center for grid discipline. Each state utility is given deviation warning if there is continuous under drawl / over drawl/ under injection / over injection by more than 150MW for specified time blocks. If wind blows heavily, there should be provision to back up thermal units not only in Tamilnadu but also in other states. i.e. when Tamilnadu over injects, and as frequency tends to increase beyond 50.05Hz, other states should be permitted to overdraw in order to maintain frequency within economical operation range. Such over injection and such overdrawls to backdown coal based thermal units should be allowed and should not be treated as grid indiscipline. We should consider India as a Grid and not Tamilnadu alone as a grid. To make this possible, the inter state transmission lines need to be strengthened. As there is no provision to back down thermal units to the extent of 2000MW (variability) within Tamilnadu, windmills are treated as spinning reserves and subjected to backdown.

    Also to manage such shortfall of around 2000MW (due to variability in wind penetration),the state should be able to purchase such quantum from spot market (energy exchange). But unfortunately, there is grid congestion; national grid (Rest of India to Southern grid) as well as regional grid (S1 to S2).

    Let us wait and see how things improve after COD is declared for Raichur-Solapur transmission lines, which is expected by August.

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