Power shortages are necessitating the widespread use of generator sets (henceforth, gensets) on construction sites. So, which are the most popular sizes?

Most construction companies opt for gensets of 125 kVA or 250 kVA capacity, only very large sites can use 1000 kVA capacity, says Naresh Kumar Gupta, Founder Director, Generator Bazaar. “Multiple genset units are preferable to one large unit so that work continues without interruption even if a breakdown occurs.”

“15 kVA to 250 kVA gensets are the most popular for construction sites based on the typical load of welding, drilling, cutting tools, lighting, etc.,” opines Narsing Agrawal, Vice President at Modern Hiring Service. “Few construction sites use gensets larger than 500 kVA capacity in all.”

“Most companies prefer to place multiple small generators at different points on the site,” continues Agrawal. “Synchronising the power from multiple gensets at one point and then distributing it adds to the cost of cables but is the practice on more confined infrastructure sites like dams or hydroelectric power projects, or when the company has a distribution setup or wants to make power available at one point.”

Renewables ahoy

Is it viable to tap renewable energy to power a construction site?

Prasanta Kumar Ray, JGM and Head, Plant & Machinery, Mumbai Ahmedabad High Speed Rail C4, L&T Construction, attest to using solar power in areas where the load is very limited like onsite laboratories and lighting, as long as the use is expected to be long-term (five years or more). “We use LED lighting across our sites to reduce the load,” he says. “We use hybrid generators wherever possible, such as for lighting purposes, these gensets charge a lithium battery that is capable of taking the load through the night.”

“For small projects worth several crores it is not feasible to invest in renewable sources of energy but solar or wind energy can definitely be used for big projects,” says Mradul Kumar Bhardwaj, Manager – Operations, Poddar Infratech. “Solar illumination is being used on sites.”

In the future, Bhardwaj believes that the government’s push to use renewable energy and clean fuels will create a regime change in the genset space.

Emerging alternative

Speaking of alternative energy sources, there are conflicting opinions about the use of natural gas as a fuel to power gensets working on construction sites. One view is: “natural-gas-powered gensets have proven successful in industrial applications but these aren’t viable on construction sites where piped gas isn’t available,” to quote Agrawal.

The fact that “we cannot manage the storage of natural gas is why that fuel has still not become a viable alternative to diesel-powered gensets,” opines Gupta. “Generators using compressed natural gas are available in India but at a very high cost. When a widely deployable method to convert compressed natural gas to liquid natural gas becomes available, natural gas-powered gensets will be viable. The problem with compressed natural gas is stored. We need to be able to store natural gas in liquid form in cryogenic cylinders so that a fuel stock of at least a few days can be made available.”

That said, in a place like the Northern Capital Region (NCR) where diesel gensets are banned during winter, Agrawal believes that a very large construction site might opt for a natural gas-powered genset. “It depends on the usage because the availability of natural gas-powered gensets is limited, most are of a large capacity and cost 5x-6x times the diesel genset.”

Consequently, Ray justifies the use of a natural gas genset “where the load is very high.”

We’re using diesel generators so far as alternative fuels like natural gas are still not readily available, shares Bhanu Shankar Pandey, Incharge of Plant and Machinery, ACC India.

The alternative view is: “Natural gas gensets have emerged as a leading cleaner alternative to a diesel-powered genset,” to quote Aashim Ahuja, Director, Perfect Generator Technologies. “These are sold in sizes ranging from 10 kVA to 315 kVA which can power a household to a construction site to full-fledged factory operations.”

Ahuja’s company has supplied 3 x 125 kVA and 2 x 25 kVA gas gensets to a construction company for a site near Pragati Maidan, Delhi. “Gas gensets are cost-effective, efficient to operate, and can make operating within strict emission regulations easier because natural gas is the cleanest burning fossil fuel,” says Ahuja. “Gas gensets cost approximately twice as much as diesel gensets but their running cost is almost half that of diesel gensets.”

Onsite safety

No mention of a genset would be complete without covering safety. Onsite generators used by contractors must comply with the following standards, according to Ahuja: “Proper installation of the genset is a must, and that includes proper ventilation across the genset, earthing as per Electrical Board guidelines, regular cleaning of the genset if the site is dusty, etc.”

Safety best practices associated with gensets include proper earthing; using the power generated only through a panel board; installing MCVs (circuit breakers), earth leakage relays (ELRs), and earth leakage circuit breakers (ELCBs), and careful changeovers in case of outages of the power from temporary connections on site, adds Pandey.

Obviously, safety comes at a cost. Now while “reputed construction companies with sizable budgets and qualified technical staff implement genset-associated safety measures, the majority of construction sites don’t adopt safety best practices,” observes Gupta. “In general, India needs to improve how it implements generator-associated environmental and safety measures. We see a general lack of understanding of safety practices and a lack of implementation of norms here versus Gulf countries and Western nations.”

One way to ensure safety is to consult the vendor. “Electrical safety on site is critical, we try to ensure that sites, where we send gensets, adhere to a safety checklist,” says Agrawal.

Changing norms

Spiraling air pollution especially in the NCR in winter when gensets are banned leads Gupta to say: “To make a genuine difference to generator-associated pollution the government would have to devise new norms and implement them uniformly very stringently.”

New standards covering emissions of oxides of nitrogen (NO), hydrocarbons (HC), carbon monoxide (CO), particulate matter (PM), and the CI (Compression Ignition) and PI (Positive Ignition) are on the anvil.

The Ministry of Environment, Forest, and Climate Change has notified draft revised norms for genset emissions to come into effect in July 2023. Interestingly, these norms are common for all fuels, even upcoming fuels like hydrogen gas, quite unlike the present genset emission standards that are based on the kind of fuel used: gasoline, diesel and dedicated CNG, dedicated LPG, dual fuels and bi-fuels.

“The government’s new diesel genset emission standards aim at regulating emissions and reducing pollution in view of the large number of gensets in use in the NCR,” observes Ahuja.

Already, revised emission and noise standards have compelled construction companies to become more discerning about their choice of genset.

“Revised genset standards have compelled the use of more silent and energy-efficient gensets, especially in metro cities like Delhi where pollution is already a concern,” says Bhardwaj.

“We only buy or rent generators that incorporate the latest technology and meet the CPCB latest norm which requires gensets to generate less than 75 decibels of noise one metre from the enclosed surface, so all our sets are acoustic enclosed,” adds Ray. “We use gensets that are fuel-efficient and run on the best engines. We perform a life-cycle cost to choose a genset.”

May the judicious use of gensets be replicated across the industry.

Optimising capacity

First off, calculate your connected load.

For every project, we first calculate the connected load for every area by creating a schedule showing the equipment that will be used month-by-month and its connected load, explains Prasanta Kumar Ray, JGM and Head, Plant & Machinery, Mumbai Ahmedabad High Speed Rail C4, L&T Construction.

Based on his experience, Ray points out that a typical underground metro construction site would need a power connection of 10 MVA for the tunnel boring machine and 3 MVA for other needs whereas an elevated metro stretch of around 10 km would need around 4-5 MVA of power.

Your onsite power needs could come from “different machines proposed to be used (reinforcement cutters, bending tools, concrete mixers, lifting cranes, concreting tools, etc.), worker accommodation, onsite workplaces, and material fabrication yards, and illumination for night shifts,” explains Mradul Kumar Bhardwaj, Manager Operations, Poddar Infratech.

“Onsite generators are used to power equipment such as air compressors, hand drills, chain saws, battery chargers, water pumps, temporary lights and electric welders, each of which has a definite power requirement, and temporary worker accommodation and administrative offices,” adds Aashim Ahuja, Director, Perfect Generator Technologies. If you need help assessing your need, ask a vendor as most offer “power requirement assessment services, which can help determine the site needs,” he says.

After we’ve calculated the connected load, “if we can get a temporary connection from the board to optimise the cost of the diesel generator, we get generators to cover 70 per cent of that load,” shares Ray. “If we cannot get a temporary connection, we cover the entire load through diesel generators.”

As a rule of thumb, generators should cover 70 per cent of the electrical load of a site considering that all the machines needing power aren’t mobilised simultaneously, says Bhanu Shankar Pandey, Incharge of Plant & Machinery, ACC India.

To control your costs, it’s important to recalculate your load every month as the connected load is a dynamic factor, advises Ray.

Also, don’t scrimp and pinch when calculating the connected load because machinery translates into productive workers. “We try to engage as much machinery as possible to expedite the work on-site even though it requires heavy power consumption from the grid or through generators,” says Bhardwaj.