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Harnessing excess generation in Delhi’s grid

A look at real-time generation for the Northern Grid, from which Delhi draws its power, reveals that despite popular belief, over 160-240MWh of energy is being lost due to excess generation each day.

This is over and above the often quoted 20% transmission losses. Essentially, this "real" excess generation can be mapped by looking at the frequency at which the grid should be operating.


How it works

All grids are mandated to have a baseline frequency of operation of 50HZ at all times, and cannot fluctuate more than 49.5 to 50.2 Hz. The baseline frequency of 50Hz is the frequency that the grid maintains, in real time, if supply exactly matches demand. When supply of electricity exceeds demand, the frequency increases as not enough energy is being drawn from the grid. Grid operators must ask generators to cut back on generation else the grid will "trip". In the reverse case, demand exceeds supply, the frequency drops below 49Hz, as the grid slows down when the load increases. Too much electricity is being drawn and grid operators may ask generators to bring partly loaded plants to full loading / start peaker plants, when the frequency falls below 49.7Hz (1st warning) and 49.5Hz (2nd warning). If this is still not enough, load shedding might occur to help stabilize the grid back to 49Hz.

In this respect, any time the grid is operating above 50.2 Hz, it represents a measure of excess generation i.e. over and above transmission losses. One would not expect a city like Delhi to have excess generation - however, some excess generation is truly unavoidable in any grid system, regardless of the forecasting, power control systems, or transmission efficiency.  The only way to effectively ensure usage of this excess generation is through storage. 

A typical day in the Northern Region - how much time the grid has spent generating too much energy

For example, see the amount of excess generation experienced in 24 hours in real-time for the Northern Grid. (In 24 hour profiles, NRDLC has marked the time spent above 50.09Hz in red, as this means supply exceeds demand; of this, the time spent above 50.2Hz corresponds to real - and illegal - excess generation considered in our analysis.)


Winter Day – 15 January 2014
Summer Day – 15 July 2014
Source: NRLDC Website
Over 160-240 MWh energy per day is wasted in any given year on the Northern Grid alone
An analysis of frequency control data for the Northern Grid over one whole year demonstrates that a range 160-240 MWh of energy is being lost on a typical day – and this varies significantly in summer to winters.
This waste energy essentially represents a waste of energy, and one could financially quantify this waste as this is electricity is generated, paid for, but not used. 
Harnessing waste energy
Excess energy on a grid could be harnessed by small scale storage or storage devices. While many devices exist, charging of batteries is the most obvious form of storing and harvesting this energy; and this can be redeployed for industrial, residential use or for mobility. Batteries can be connected to the grid and charged, not as a constant load to the system, but to redirect excess generation when it occurs in real time. 
To help us visualise the waste energy in real terms, and to help investigate if financially feasible to harnessing excess energy, it is useful to think in terms of using batteries for small grid scale storage, sourcing these batteries through the EV market, and redeploying them for mobility or other uses. 
Here, the CAPEX cost pertains to the full cost of buying BYD electric buses, since most of the price of a bus reflects the investment in advanced storage batteries.
In particular, our analysis suggests that harvesting this waste energy could fully pay for the purchase and charging costs of a fleet of 30 e-bus equivalents in Delhi alone.... not over the lifetime of the grid, but associated with the inefficiencies tolerated in one day.
In real life, the batteries used for small scale grid storage could be second-hand and may be re-purposed beyond mobility. However, this article demonstrates that even buying brand new technology (capable of advanced storage for fleet based mobility in a concrete use-case) can break even with efficiency gains that could be made off the Northern Grid.
The total CAPEX and charging costs of a single e-Bus distributed over 5 years can be recovered daily from efficiency gains in the Northern Region grid alone – in fact, efficiency gains could recover the costs of at least 30 such e-Bus equivalents (in winter months, daily gains could recover costs 70 e-Bus equivalents). 
However, leaving aside the break-even points from a financial perspective, the real amount of energy saved could provide 300- 500 daily e-Bus equivalent charges in summer, and 600 – 1000 e-Bus equivalent charges in winter. A fundamental point to note is that the right power controls need to be in place so that these batteries act as storage when required by the grid, rather than an additional load on the grid.
Significant capital can be freed up for a strapped municipal and Central government budget by investing in enhanced grid control & small scale storage upgrades!
Image Credits: Bert Kaufmann
Author: Sustainability Outlook