Power shortages are necessitating the widespread use of generatorsets(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 1,000 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 forconstruction sites based on the typical load of welding, drilling, cutting tools, lighting, etc,” opines Narsing Agrawal, Vice President, 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.”
“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 future, he believes that the Government’s push to use renewable energy and clean fuels will create a regime change in the genset space.
“We cannot manage the storage of natural gas;that’s why it 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 storage. We need to be able to store natural gas in liquid form in cryogenic cylinders so that afuel stock of at least a few days can be made available.”
That said, in a place like the National Capital Region (NCR), where diesel gensets are banned during winter, Agrawal believes 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 costfive to six 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, In-Charge of Plant & Machinery, ACC India.
The alternative view, to quote Aashim Ahuja, Director, Perfect Generator Technologies, is, “Natural gas gensets have emerged as a leading cleaner alternative to a diesel-powered genset. These are sold in sizes ranging from 10 kVA to 315 kVA, which can power anything from a household to a construction site to full-fledged factory operations.”
His company has supplied 3 × 125 kVA and 2 × 25 kVA gas gensets to a construction company for a site near Pragati Maidan in 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.”
Best safety 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 ageneral 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,” says Agrawal. “We try to ensure that sites where we send gensets adhere to a safety checklist.”
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 to regulate emissions and reduce 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 lifecycle cost to choose a genset.”
May the judicious use of gensets be replicated across the industry!
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, PoddarInfratech.
“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.”
“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, according to Bhanu Shankar Pandey, In-Charge 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 onsite even though it requires heavy power consumption from the grid or through generators,” says Bhardwaj.
