Catch Energy Where It Falls
In the 1990s, environmentalists in India told urban planners to find ways to channel rain from rooftops and gardens. The idea was to recharge local aquifers in order to reduce the need for costly water from dam reservoirs tens and hundreds of kilometers away. More than two decades later, in spite of changes to mandatory building bylaws, urban rainwater harvesting has met with mixed success at best.
More recently, with advances in solar panel technology and plummeting prices, a similar approach now aims to catch energy where it falls. Early signs suggest a better chance for rooftop solar to succeed in shifting the urban energy paradigm.
The incumbent Prime Minister Narendra Modi has set a target of 100 gigawatts of solar power by 2022, up from 20 gigawatts in 2009. The government is attempting to achieve 40 gigawatts of the target utilizing urban rooftops. “Currently there is less than one gigawatt installed on rooftops across the country, but evidence suggests that this will increase rapidly in the coming years,” says Adarsh Das, CEO of Sun Source Energy, a private company which has completed more than 65 installations across India. According to Das, the cost of generating rooftop electricity has dropped 60% in the past five years, and is now competitive with commercial and industrial tariffs. According to the Ministry of New and Renewable Energy, rooftop solar may attain parity with domestic tariffs by 2017, while in some areas this has already been achieved.
Rooftop solar has immense potential in India, where numerous regions are endowed with 300 sunny days in a year. The government of Delhi recently published a draft solar energy policy estimating a potential of 2,500 megawatts (MW) across 31 square kilometers of rooftops. They say this could help meet one fifth of the city’s peak electricity demand in the future. Currently, Delhi has only seven MW of installed rooftop solar capacity, but the policy has set a target of 1,000 MW by 2020, and double that by 2025. To begin with, all government buildings will be mandated to install a system. Other state and local planners across India are drawing up similar plans.
The government’s 100 gigawatt target seems ambitious, given that the country has been adding only one gigawatt annually. According to a conservative estimate by the Ministry of New and Renewable Energy, the rooftops of buildings with more than two rooms can accommodate about 25 gigawatts of capacity. “Our target is ambitious, but not unachievable,” says A.K. Tripathi, Director (hydro) of the Ministry of New and Renewable Energy. The government will subsidize around five of the 40 gigawatts to the tune of 15% of the project cost, says Tripathi.
The appeal of rooftop solar power has grown, given that land acquisition for power projects has becoming increasingly challenging. Large hydropower projects are facing financial challenges as well as local opposition. Increasingly, local planners are evaluating solar potential within their own jurisdictions.
Rooftop solar can be expedited, given that little time is spent in land acquisition – in fact, most sites are ready for installation. This will reduce the loss of cultivable land and areas used for grazing. It will also moderate the need for large-scale projects, be it coal or hydropower, which have severe social and ecological costs. Environmentalists in India have welcomed the push for expediting such decentralized renewable energy solutions.
