The roof is the limit

The IPCC report this week presented an apocalyptic scenario for the planet unless governments begin immediately to reduce their carbon emission. Most of Nepal’s electricity is generated by climate-friendly hydropower plants, but over-dependence on hydropower is detrimental to the stability and reliability of the national energy system.

As this monsoon showed, expensive hydroelectric infrastructure is exposed to the risk of flash floods, and can also damage valuable riverine ecosystems.

Nepal needs a reliable and steady as well as clean and diversified supply of energy for economic progress, and with the cost of photovoltaics plummeting large-scale solar farms are becoming feasible.

At present, 68% of Nepal’s energy consumption is derived from biomass: firewood and agricultural residue. And 25% of the national energy mix is from fossil fuels, all of which is imported from India. The rest is obtained primarily from hydropower, about 3.5% and another 3.5% from renewables such as solar photovoltaics (PV), biogas and micro-Hydro.

In 2020, Nepal consumed 8,880GWh of electrical energy mostly generated from hydropower, of which about 25% was imported from India to tide over a shortfall.

The increasing incidence of extreme hydro-meteorological events and seasonal floods have damaged hydropower infrastructures worth billions over the past few years. Moreover, hydropower infrastructure is invasive – they involve resettlement, inundation of fertile land and damage to river ecosystems.

The increasing demand for energy and the social, environmental and capital cost of hydropower should prompt a switch to solar energy to supplement existing hydropower. However, PV farms are also subject to land constraints, although the area needed is smaller than that for an equivalent hydro system.

A solution comes in the form of rooftop photovoltaic systems in combination with surface solar farms, floating solar arrays and agrivoltaics (solar PV in combination with agriculture) as a significant part of the energy mix in Nepal.

Rapid reduction in the price of solar panels and new battery technology in recent years have opened up enormous markets in developed and developing countries alike. The solar resource in Nepal is compatible with the production of electricity at $40/MWh, and could fall below $30/MWh once the country’s solar industry matures.

For high-demand urban centres, solar energy can therefore be an avenue to produce a significant portion of their energy consumption from rooftop photovoltaics.

The government aims to increase annual electricity consumption per capita from 0.26MWh to 1.5MWh by 2030, electrifying transport, cooking and industry. This is where solar energy could come into play and largely eliminate solid biomass and fossil fuels.

If all of this new electricity demand is to be met from solar PV, 1,000 watts of solar panels will be needed per person, covering 5sq m (twice the area of a double bed). To put this in perspective, Australia is currently installing solar panels at double that rate.

All of these panels could be easily accommodated on the roofs of buildings, instead of taking up valuable land. Because the panels will be spread throughout the country, the spatial variability can help ensure reliable power supply to the national grid along with an integration of storage systems including batteries and pumped hydro energy storage.

According to a report by International Renewable Energy Agency (IRENA), 60% of total solar PV capacity globally by 2050 will be utility-scale, while the remaining 40% will be from rooftop arrays. The report expects distributed solar PV installations to grow more rapidly, driven by policies and supportive measures, as well as consumer engagement in clean energy transformation.

A sectoral analysis from the same organisation shows that globally, in 2020, solar photovoltaics accounted for approximately 127GW of electricity generation capacity addition. This amounts to 45% of global generation additions including renewable and non-renewable energy technologies. A radical transformation is already underway in the global energy sector. At the forefront of this change lies solar PV energy.

A recent study of solar rooftop potential of cities including Kathmandu, Pokhara, Biratnagar, Butwal, and Nepalgunj by Renewable and Sustainable Energy Laboratory (RSEL) at Kathmandu University indicated that the average per capita rooftop area available is 24sq m.

This is sufficient to generate about 8MWh per person per year -- 30 times more than Nepal’s current per capita electricity consumption and is on par with electricity consumption in developed countries like Europe, Australia and Singapore.

Across rural Nepal as well, there is vast rooftop solar potential. This could supply cheap electricity directly to millions of people to power water pumps, grain grinders, lighting, refrigeration, cooking, heating, telecommunications and electric vehicles. Most of these services can be operated or charged during the daytime, greatly reducing the need for overnight storage.

An adequate policy framework that promotes the efficient use of solar rooftop along with agrivoltaics, floating solar and surface solar will be fundamental for Nepal’s green development. Concerned authorities, academia, industries and the government should collaborate to achieve the diversification of energy sources and complete electrification of Nepal.

The recently launched Solar Nepal Initiative at Kathmandu University will explore such avenues and disseminate science-based information to help improve on the policy framework as well as raise awareness among the general public and researchers.

Sunil Prasad Lohani is a lead professor of Renewable and Sustainable Energy Laboratory (RSEL) at the Department of Mechanical Engineering, Kathmandu University, where Ural Kafle is a research scholar.