Sourcing the sun

8 min read
09 Feb 2018
8 min read
2844 words
Turning to solar power as a supplementary energy source makes a lot of sense, even for hydropower-blessed Nepal

In the remote village of Bhangeri in Nuwakot district, old furniture,
rocks and pipes have been placed on the zinc rooftops of the houses. These items keep the roofs from being blown away by the wind. Also propped up on the rooftops are solar photovoltaic (PV) panels of all sizes. In the weeks and months following the earthquakes of 2015, when power supply got unusually intermittent, it was these solar panels that the villagers turned to for a dependable source of electricity.
That was how the villagers were able to light up their homes and charge their cell phones to talk to their near and dear ones during that trying time.Over the last decade, electricity has been a rare commodity for most Nepalis. During this period of load-shedding, solar PV panels, like those in Bhangeri village, popped up on rooftops of houses across the country. Solar PV panel vendors sprang up in every nook and corner of the country too. Today, two years since the exceedingly long power cuts came to a halt, Nepal still depends significantly (for nearly 35 per cent of its supply) on India to fulfill its electricity demand. As expected, solar panel adoption has dropped by more than 80 per cent with the end of load-shedding. But, say energy experts, supplementing energy needs through solar sources will not only lessen the load on the already overburdened national electricity grid, but also make the country more energy secure.

Energy security

Nepal’s geopolitical vulnerability was laid bare during the economic blockade of 2015. The blockade crippled the supply of petroleum products and threw normal life into disarray. “How can we be certain that India will not do the same with our electricity supply? What if they decide to stop selling electricity to Nepal?” says Kushal Gurung, CEO of Wind Power Nepal, an engineering and consulting firm. “And why is the government not aggressively looking to diversify its electricity sources to make up for the demand-supply deficit.” To achieve that balance, all Nepal needs to do is to turn to the sun. Nepal sees an average of 300 days of sunshine annually, making it a country with huge potential for solar energy. According to a report published by the Alternative Energy Promotion Centre (AEPC), a state-owned entity, commercial potential for solar power was estimated at 2,100 MW, which is nearly double the country’s current electricity demand. “By diversifying our energy sources, we’ll get closer to achieving energy security and sustainability—two key components any nation must achieve,” says Bhushan Tuladhar, regional technical advisor for UN Habitat.

The changing solar landscape

With both India and China aggressively setting up large-scale solar plants to add to their nations’ electricity grid, the demand for solar PV panels have shot through the roof. To meet this demand, manufacturers, mainly in China, have increased their solar panel production rate. This increase has helped draw down the cost of panels. Meanwhile, advancements in solar technology have made solar PV panels more efficient than ever. The convergence of these two developments has brought the per-unit cost of solar electricity at par with, and in some cases, lower than that of other renewable and non-renewable electricity sources.
Unlike hydropower plants, which can take years to come into operation, solar plants can be set up in a relatively short period. “We can have a 2 MW utility-scale solar power plant go online in less than six months,” says Anjan Niraula, General Manager, Gham Power. To set up such solar plants, the country already has the needed experts and engineers in the sector. Companies such as Gham Power and Wind Power not only deal with solar components, but also offer engineering, procurement and construction (EPC) services. EPC includes everything from conducting site surveys, determining power generation capacity, engineering a plant’s design, selecting and procuring equipment and constructing solar plants.

Different solar-power generation models

Residential solar PV system

The residential solar PV system is the most widely adopted solar electricity generation system in Nepal. “When load-shedding was at its most extreme, we used to be flooded with calls from the capital’s residents to have solar PV systems installed in their homes. But ever since the load-shedding ended, the demand dropped drastically,” says Niraula. Niraula estimates that with just the existing residential solar PV systems in Kathmandu alone, around 20 MW of electricity can be generated. The rule of thumb: 1 MW can power 1,000 houses; thus 20 MW can power 20,000 houses. “Just imagine what can be achieved if just half of Kathmandu’s 200,000 houses roofs were fitted with 1 KWH solar PV systems. We are talking about 100 MW just from half of Kathmandu’s rooftops,” says Gurung. Wider adoption of residential solar PV systems in Kathmandu will not only reduce the load on the national grid, but also make a significant contribution to the grid by feeding the excess electricity to it. In order to do just that, the government introduced a net-metering system in 2017, which allowed residential and commercial solar PV systems of certain capacity to supply electricity to the national grid. The people’s adoption of the system, however, has been lukewarm. The high upfront cost of installing solar PV systems  has been a major factor behind this underwhelming response. The average cost of installing a residential solar PV system with 1 KWH capacity (including batteries) is around Rs 350,000. The costs for a system without any batteries start from Rs 120,000.

Large-scale grid connected solar plants

But if the goal is to make a more significant contribution to the national grid, large-scale grid-connected solar plants (solar farms) are the way to go. Large-scale grid-connected solar plants can feed power to the national grid in real time, and don’t need expensive batteries to store electricity, which should keep per-unit electricity prices competitive. *For more on Nepal’s solar farming potential, read our next feature.

Solar microgrids

In 2014, 84.9 per cent of Nepal’s population had access to electricity, which was a major milestone for the country. This was largely made possible due to the success of micro hydropower plants in villages, which were not connected to the national grid. But it is not feasible for all villages without access to the national grid to build hydropower plants, and that’s where solar microgrids can step in. And even in villages with micro-hydropower plants, solar microgrids can make the electricity supply more robust. “It’s vital for villages to have access to electricity. Electricity can help jumpstart the economy. When load-shedding ended, Nepal’s economy also grew significantly,” says Tuladhar. “And the more villages you connect with electricity, the better it is for the overall economy.” But setting solar micro grids in remote villages is no easy task. The private investors who are willing to invest in such ventures are forced to charge high rates to their consumers owing to the cost of setting up microgrids. The average cost of setting up 1 KWH of solar micro grid is Rs 650,000. “Ferrying microgrid components to most villages with no road access often costs higher than the cost of the components themselves. The villagers would obviously want electricity at the national-grid rate, which is impossible for investors to provide,” says Gurung. “The government needs to step in by identifying firms that are investing in solar microgrids in such remote areas and bear the cost of transportation.”

The role of the government

Countries all around the world are diversifying their sources of electricity. India and China, Nepal’s immediate neighbours, are accelerating the shift to this renewable sources of energy. According to data published by Mercom Capital Group, a US-based research and consulting agency, last year alone, India added 7,100 MW from solar energy to its national grid. In 2016, India added 4,313 MW of solar energy. Similarly, in the same year, China had added 34,000 MW of solar capacity. Both the countries’ governments have been instrumental in the giant strides made in solar energy. They have accelerated solar-power adoption by building solar plants and making it enticing for businesses to invest in solar by introducing tax rebates.
In the case of Nepal, for it to grow its fledgling solar-power industry, the government needs to get on board too. It can start by introducing solar-friendly policies and offering better prices for the electricity produced by solar-farm companies. There’s much to gain by encouraging the solar sector. A thriving solar energy sector will complement hydropower, reduce Nepal’s dependence on India for its electricity and move the country closer to becoming energy independent.

How solar panels work

Before we understand how solar panels work, we must know what they are made of. Generally, solar panels comprise much smaller units called solar cells or photovoltaic (PV) cells. Most PV cells are made of silicon, which is one of the most abundantly available elements on earth. It is a natural semiconductor—an element that can be made to conduct electricity under certain conditions—which makes it the ideal material for solar-to-electrical energy conversion. A PV cell is made up of two layers of crystalline silicon that are sandwiched between two conductive plates. These two layers are treated (or doped) in specific ways so that each carries an electrical charge.
The upper layer (the n-type layer) is treated with phosphorus, which gives the silicon atoms additional electrons. These additional electrons give this layer a negative charge. The lower layer (p-type layer) is treated with boron, which results in the silicon atoms having fewer electrons. This absence of electrons gives this layer a positive charge. The point where these two layers meet is called the P/N junction, which serves as a physical barrier that keeps the electrons from flowing between the two layers.
When sunlight with enough energy reaches a PV cell, solar particles called photons ‘knock’ the additional electrons in the n-type layer out of their atomic orbits. Since these electrons cannot cross the P/N junction, they are collected by the conductive plate, which is connected to an external circuit. The electrons find their path through the plate, they travel on the circuit around the negative plate to reach the positively charged plate. This flow of electrons provides a constant flow of electricity that can be used for lighting a bulb or charging a phone.All solar panels generate direct current (DC) electricity, which flows in a single direction through a circuit—from the negative to the positive end. However, since most households use alternating current (AC), the electricity generated from the solar panels needs to go through an inverter that converts it into usable form. In an AC circuit, the electrons flow periodically in either direction between the two ends. This kind of electricity is usually produced through generators, which use kinetic energy and convert it into electrical energy. This is the type of energy that is generated by hydropower plants and diesel generators—the two prominent sources of energy in Nepal.

How solar water-heaters work

Solar water-heaters work on the same basic principle as solar panels—that is, they capture solar energy and convert it into a usable form. The only two differences between the two are the following: water heaters convert solar energy into heat energy, which is used to heat water; in solar panels, on the other hand, the sun’s energy is captured by photovoltaic cells that turn solar energy into electricity.

Components of solar water-heaters

Heat-collection component

The heat-collection component converts solar radiation into heat, which is then transferred to the water. This component comprises collectors, which are available in flat-plate type and evacuated-tube type. Flat-plate collectors have a horizontal pipe (called headers) at the top and the bottom, and smaller vertical pipes (called risers). Water flows from a storage tank to the bottom headers, goes up the risers—collecting heat along the way—and exits through the top header, and then goes back to the tank.
Evacuated tubes, as the name suggests, are tubes that are insulated by a vacuum layer, which limits heat loss from the water flowing through the tubes. This type of collector has the added advantage of receiving perpendicular radiation from the sun for the greater part of a day due to the cylindrical shape of the tubes—because larger areas of the tubes are exposed to the sun throughout the day. However, evacuated-tube collectors are relatively more expensive than flat-plate collectors.

Storage component

The water that is heated by the collectors is stored in a tank for further use. To ensure that the loss of heat from the water is limited, the storage tank is kept well-insulated, using materials such as polyurethane foam.
Solar water-heating systems can be categorised into two types, based on how water circulates inside them: passive and active. In a passive system, also known as a thermosiphon system, water flows without the assistance of pumps. Instead, the flow is generated by the natural process of convection. In this system, the storage tank is placed at a higher elevation than the collector. The sun’s energy heats up the water in the collector. The warm water rises up and flows into the tank, while cold water from the tank flows into the collector, unassisted, through the force of gravity.

An active system is very similar to the passive system in terms of how the water is heated. However, this system makes use of pumps to aid in the circulation of water. The pumps help to move water between the collector and the tank, making the issue of the tank’s location irrelevant. Unlike the passive system, where the tank has to be placed higher than the collector, this system allows for the tank to be placed in a location at any distance as per the user’s choice.

Electric water-heater Vs solar water-heater

The most significant factor that buyers take into account while searching for a water heater is the cost associated with it. Most electric heaters have lower initial costs (the cost of the device and installation) than solar water-heaters. That alone may make it seem like a good deal, but that would be the case only when you do not factor in the long-term costs. A typical 4,000 watt electric heater will use a considerable portion of electricity that is used in a household each time that it is turned on, adding to the electric bill.

On the other hand, although a solar water-heater may seem like a huge investment, it is the more sensible option out of the two in the long run. Since the water-heating process is powered by the sun, buyers can save a significant amount on electric bills. Furthermore, this option lightens the load on the national grid.